US20150361523A1

US20150361523A1 - Use of oxygenated or polyoxygenated inorganic weak acids, or derivatives, residues and waste thereof, in order to increase the recovery of copper and/or the concentration of copper in processes for the leaching or bioleaching of copper minerals

Info

Publication number: US20150361523A1
Application number: US14/758,141
Authority: US
Inventors: Carlos SCHUFFER AMELLER
Original assignee: QUIBORAX SA
Current assignee: QUIBORAX SA
Priority date: 2012-12-28
Filing date: 2013-12-27
Publication date: 2015-12-17
Also published as: CA2896667A1; WO2014100910A1; CL2012003727A1; PE20151174A1

Abstract

The invention concerns the use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same, or of solid and liquid wastes from plants producing oxygenated or polyoxygenated weak acids, or minerals or compounds and their derivatives to increase copper recovery from mineral and/or to increase the copper concentration of the pregnant leach solution in the copper leaching process or the copper bioleaching process.

This invention also concerns a copper leaching procedure that comprises the addition of a necessary amount of an oxygenated or polyoxygenated weak acid, or a compound or a mineral that generates the same to the leaching process, and the simultaneous addition of sulfuric acid to the leaching heap, where the necessary amount of oxygenated or polyoxygenated weak acid will depend on the characteristics of the mineral.

This invention also describes a copper bioleaching procedure that comprises the addition of a necessary amount of an oxygenated or polyoxygenated weak acid, or a compound or a mineral that generates the same into the bioleaching process, and the simultaneous addition of sulfuric acid to the bioleaching heap or dump site, where the necessary amount of acid added will depend on the characteristics of the mineral.

Description

This invention concerns the use of oxygenated or polyoxygenated weak inorganic acids, in any concentration, and their derivatives, residues, and solid waste in copper ore leaching or bioleaching, using sulfuric acid or its derivatives.
Particularly, it concerns the use of oxygenated or polyoxygenated weak acids, such as boric acid, its derivatives, minerals containing boron, borax, their derivatives, residues, and solid and liquid waste from plants producing boric acid and borax, and phosphoric acid, their minerals, derivatives, residues, and solid waste, in copper mineral leaching or bioleaching, using sulfuric acid or its derivatives.
The invention also concerns a leaching and bioleaching process in which an oxygenated or polyoxygenated weak acid, such as boric or phosphoric acid, is added as part of the process.
The traditional leaching process of copper minerals is a hydrometallurgical process, consisting of the recovery of copper from the minerals, which are separated by applying a solution of sulfuric acid and water. The subprocesses that occur in leaching are:
First stage: Heap leaching

- Crushing: The extracted material containing copper minerals is fragmented by primary and secondary crushing in order to separate the mineral from the impurities that accompany it. This crushing is sufficient to expose the copper minerals to the infiltration of the acid solution.
- Heap formation: A conveyor belt takes the crushed material to the site where the heap will be formed. In the process, the material is irrigated first with a solution of water and sulfuric acid. This process is known as curing, and its aim is to start the copper sulfuration of the mineral at an early stage, while the small particles produced by crushing are agglomerated. In this process, concrete can be added simultaneously as an agglomerating product. The mineral is deposited in an organized manner in a continuous heap of varying height (leaching heap). A drip and/or sprinkler irrigation system is placed over the heap which covers the entire exposed area. An impermeable cover, over which a drainage system (slotted pipes) that allows the solution leaking from the mineral to be collected has been installed under the heaps of mineral to be leached.
- Irrigation system: An acid solution of water and sulfuric acid is slowly dispersed by the drip and/or sprinkler irrigation system onto the surface of the heaps, which permeates the heap to its foundation. The leaching solution partially dissolves the copper contained in the minerals, forming a copper sulfate solution that is collected by the drainage system and removed from the heap section in waterproof pipes. This process produces copper sulfate solutions in variable concentrations, usually about 2 to 20 grams per liter (gpl), called PLS, that are taken to various tanks where they are purified by eliminating any solid particles that may be in the solutions.

It must be noted that variable amounts of non-leached copper remain in the leaching heap, the amount of which will depend on the quality of the mineral.

- Second stage: Solvent extraction.

In this stage, the residues or impurities are eliminated from the solutions collected from the leaching heaps. The copper concentration increases by approximately 5 times through ionic extraction. The PLS solution is mixed with a solution of paraffin and organic resin to extract the copper from it. The resin selectively attracts the copper ions (Cu⁺²), thus obtaining both a resin-copper complex and a low-level copper solution, called raffinate, which is reused in the leaching process and is recovered in the byproduct solutions. The resin-copper complex is treated independently with an acid-rich electrolytic solution that causes the copper to release from the resin and bind with the electrolyte. This is the solution that is taken to the electrowinning plant.
The above described process (hydrometallurgy) can be used for both oxidized minerals and sulfur minerals. However, sulfur minerals present a problem, since their dissolution kinetics are much slower than those of oxidized minerals. As a result, an acid solution is not enough to achieve its dissolution, regardless of the acid solution strength, and a reaction catalyst is also required. Certain bacteria can be used as a catalyst, and the resulting process is called bioleaching.

- Bioleaching Process:

In the bioleaching process, microorganisms are used to dissolve minerals, releasing valuable metals found in a mineral or a concentrate that would be very hard to extract through conventional methods. Bioleaching is the conventional leaching process, catalyzed biologically and applied to sulfur minerals due to the necessity of increasing their dissolution kinetics. As such, bioleaching is a chemical process, mediated by water and atmospheric oxygen, as well as a biological process, mediated by microorganisms.
The role that environmental, biological, and physical and chemical factors play in bacterial growth and development is fundamental to mineral extraction return via bioleaching. Controlling these factors is very important to ensure that the necessary pH, humidity, temperature, nutrient, and energy source conditions are optimal, together with the absence of inhibitors, so as to allow for the maximum copper return.
Factors that influence the response of microorganisms responsible for bioleaching according to Pradhan et al. [Pradhan, N., Nathsarma, K. C., Srinivasarao, K., Sukla, L. B., Mishra, B. K. (2008). “Heap Bioleaching of chalcopyrite: a review”. Minerals Engineering 21: 355-365, 2008.] and the ITGE (Instituto Tecnológico Geominero de España [Technological Geomining Institute of Spain] (1991)) are:

- pH: Acidophilic bacteria, i.e., bacteria that grow in acidic media, and cannot be developed in a pH greater than 3.0. The pH determines which bacteria species will be developed in the medium.
- Oxygen and carbon dioxide: As most leaching bacteria in nature are aerobic, they need an environment with oxygen to survive. Oxygen (O₂) and carbon dioxide (CO₂) are necessary for leaching, as a result, it is important to ensure aeration regardless of the technology used.

Oxygen is used as an oxidant by microorganisms in leaching environments. Carbon dioxide is used as a carbon source to produce their cellular structure or to generate biomass.

- Nutrients: The bacteria used in bioleaching require nutritional sources for optimal development. They can be obtained from the ore itself, such as ammonium, phosphate, sulfur, metallic ions (like Mg), etc. Magnesium is necessary for CO₂fixation, and phosphorus is required for energetic metabolism.
- Energy source: Microorganisms use ferrous ion and inorganic sulfur as their primary source of energy. In ore leaching, the ferrous ion (Fe+2) is produced biologically, so it is not necessary for it to be added.
- Light: Visible light and non-filtered light have an inhibitory effect on some bacteria species, but iron offers some protection from visible rays.
- Temperature: Microorganisms are classified according to the temperature range in which they can survive. Thus, mesophilic bacteria survive in an optimal range of 30-40° C., moderately thermophilic bacteria at a temperature close to 50° C., and extremely thermophilic bacteria in temperatures over 65° C. If the temperature of the medium in which microorganisms exist is less than 5° C., they become inactive, and only perform their function if the temperature increases. However, if the temperature of the medium is greater than the optimal temperature, the microorganisms die.

It is important to note that the oxidation reaction of sulfur ores is exothermic; that is, it releases heat to the medium, thereby producing an increase of temperature. The capacity to control temperature will depend on the bioleaching technology design used. For example, it is more difficult to control temperature in a heap than in an agitator tank.

- Presence of inhibitors: During the bioleaching process, heavy metals such as zinc, arsenic, and iron accumulate in the leaching solution. In certain concentrations, they can be toxic for microorganisms. These toxic concentrations can be reduced by diluting the leaching solution.
- Redox potential (Eh): Oxidation of the reduced species depends on electron movement or transfer, thus influencing bacteria metabolism. As a result, the potential measurement acts as an indicator of microbial activity: the greater the potential measurement, the greater the microbial activity. The optimal potential is between 600 and 800 my (millivolt).
- Particle size: The smaller the mineral particle size, the larger the contact area for the microorganism, making leaching more effective.

All these factors can change depending on the type of microorganism.
In the state of the art, some initiatives regarding the improvement of copper concentration in the leaching process are found; some of which are presented below.
In document WO2010/149841 A1 (equivalent to AU2010264622), “Method for leaching chalcopyrite concentrate” a method to leach concentrated chalcopyrite by adding an aqueous solution of sulfuric acid and a flow of oxygen under atmospheric pressure conditions and temperatures oscillating between 75° C. and the boiling point for the solution is described. However, no reference is made in this document to the use of other acids, in particular weak acids, in the leaching process.
In document RU2226559 (C2) (the priority of which is RU20010127611 20011010), a method to process copper from its residues by adding a solution containing 15-25% sulfuric acid and 30-45% nitric acid is described. The resulting solution is left to rest until the gas release ceases, copper is precipitated and then separated by electrochemical extraction. Treatment with the acid mix improves the return of copper recovered from the electrochemical cell.
However, at this time, no weak acid, such as boric acid, has been used to improve the return of copper recovered from a leaching heap.
Other various uses of boron, boric acid, borax or its derivatives for other industries, such as the aluminum industry, are found in the literature (U.S. Pat. No. 5,332,421, U.S. Pat. No. 6,475,276 B1).
On the other hand, patent EP160463B1 describes a process to produce a leaching solution composed of water, monoethanolamine, and a monoethanolamine salt. The salt is produced by adding an acid, such as carbonic, phosphoric, sulfuric, boric, nitiric, hydrofluoric, chlorhydric, oxalic, malonic, gallic, citric, ascorbic, formic, acetic, or propionic acid, or a mixture of them. However, in the process, the acid is only added to for the purpose of making a salt, and it is not added directly or as a mineral to create the leaching solution. Additionally, in the process, the principal solvent acid mentioned is carbonic acid, which is formed in the process by injecting carbon dioxide and air, thus establishing that the process is thereby easier to control and monitor.
Borate compounds are used in the non-metallic mining industry. One of the main boron compounds is ulexite (NaCaB₅O₉.8H₂O); this naturally-occurring borate is used in non-metallic mining to produce or extract boric acid, borax, and other derivatives.
The use of ulexite has been described on the industrial manufacturing level in agriculture and forestry as fertilizer material.
Other boron derivatives, such as borax and boric acid, have been used as fertilizers and preservatives in the food industry.
Additionally, borax, which is a soluble borate, is used in mining together with ammonium as an iron and steel smelting mixture due to its ability to reduce the mixture melting point and thereby eliminate the iron oxide contaminant from the system. Additionally, the use of borax has been described in the smelting of gold and silver jewelry.
Boric acid, as such, is used in the manufacture of fiberglass, fire retardants, borosilicate glass, soaps, detergents, and certain pharmaceutical products. With regard to boric acid, it is used as an antiseptic, an antibacterial, to formulate insecticides, as well as in buffer solution compounds and as a food preservative. Industrially, boric acid is recognized as raw material in the manufacture of the monofibers that make up textile fiberglass, which is used as the structural base of plastics and circuitry. Additionally, the use of boric acid has been described as a manufacture material for dynamite and weapons of mass destruction.
With regard to another weak acid that is particularly relevant to the invention, such as orthophosphoric acid and its derivatives, the use of polyphosphates due to their high solubility in concentrated liquid fertilizers has been specified, as well as their mining and industrial use as metal chelating agents. Additionally, the use of sodium and calcium polyphosphates in the food industry and in detergent preparation has been described. Other phosphates, in the form of ammonium salts are widely used as raw material in fertilizer manufacturing. In the mining and jewelry industry, phosphate compounds, such as manganese phosphate, are used to prevent metal corrosion and to improve lubrication. Similarly, zinc phosphate is used to prevent metal oxidation. Finally, phosphoric acid, as such, is used as an ingredient in soft drinks, as a water softener, in fertilizer and detergent production, and in the mining industry as an anticorrosive and antireduction substance, and as an agent to prevent gas evaporation.

DESCRIPTION OF THE INVENTION

The use of oxygenated and polyoxygenated weak acids, particularly inorganic acids, and more particularly, boric and phosphoric acid, as the proposed use in the invention in the leaching stage or bioleaching stage increases copper recovery from the ore in the leaching or bioleaching stage, and, at the same time, increases the copper concentration of the PLS solution, thereby increasing plant production and productivity without increasing water consumption, plant size, or waste generation.
The purpose of the invention is to incorporate an oxygenated or polyoxygenated weak acid in the irrigation system, or else to add a superior layer of another mineral that can generate a weak oxygenated or polyoxygenated acid to the leaching pile for the purpose of improving copper recovery and increasing the copper concentration in the PLS.
Another priority purpose of the invention is to incorporate a oxygenated or polyoxygenated weak acid to the bioleaching process, either by adding a weak acid directly to the bioleaching heap or else by adding another mineral that can generate the a weak acid for the purpose of improving copper recovery and increasing the copper concentration achieved in the process.
Particularly, the invention concerns the use of boric acid, (in any concentration) its derivatives, minerals containing boron, borax, their derivatives, residues, and solid and liquid waste from plants producing boric acid and borax, and phosphoric acid, their minerals, derivatives, residues, and solid waste in copper mineral leaching or bioleaching, using sulfuric acid or its derivatives.
The invention also concerns the use of phosphoric acid, (in any concentration) its derivatives, minerals containing phosphorus, its derivatives, residues, and solid and liquid waste from plants producing phosphoric acid in copper mineral leaching and bioleaching, using sulfuric acid or its derivatives.
The invention also describes a leaching process in which a necessary amount of oxygenated or polyoxygenated weak acid, or a compound or a mineral that generates the same is added to the leaching process, and, at the same time, sulfuric acid is added to the leaching heap. The necessary amount of weak acid will depend on the characteristics of the mineral to be leached.
Said addition of the weak acid to the leaching heap can occur in conjunction with the sulfuric acid, or it can be added simultaneously using the normal procedures for adding acid to the heap.
However, adding the oxygenated or polyoxygenated weak acid can also occur in situ in the leaching heap, by adding a mineral or a compound that generates said weak acid over the leaching heap. Due to the contact of the mineral or compound that generates the weak acid with sulfuric acid, this process will generate the weak acid in situ.
A similar process can be performed during the bioleaching process, in which the oxygenated or polyoxygenated weak acid can be added directly to the bioleaching process in conjunction with the sulfuric acid, or else it can be obtained in situ in the leaching heap by adding a mineral or compound that generates said weak acid in the leaching heap.
In the invention, boric acid refers to H₃BO₃(trioxoboric (III) acid, B(OH)₃, also called orthoboric acid), or its derivatives. Boron minerals refers, without limitation, to ulexite, colemanite, kernite, pandermite, bakerite, datolite, elbaite, admontite, aksaite, ameghinite, ammonioborite, aristarainite, avogadrite, axinite, bandylite, barberiite, behierite, berborite, biringuccite, boracite, boralsilite, borax, borazon, borcarite, bormuscovite, cahnite, calciborite, carboborite, chambersite, charlesite, congolite, danburite, datolite, diomignite, dravite, dumortierite, eremeevite, ericaite, ezcurrite, fabianite, ferruccite, flolovite, fluoborite, foitite, frolovite, garrelsite, gaudefroyite, ginorite, gowerite, halurgite, hambergite, heidornite, henmilite, hexahydroborite, hydroboracite, hydrochlorborite, hilgardite, holtite, howlite, hulsite, hungchaoite, inderborite, inderite, inyoite, jeremejevite, jimboite, kalborsite, karlite, katoite, kornerupine, kotoite, kurnakovite, lardarellite, ludwigite, lueneburgite, luidwigite, manandonite, mcallisterite, metaborite, meyerhofferite, moydite, nasinite, nifontovite, nobleite, nordenskjoeldine, olenite, oyelite, painite, pentahydroborate, pinnoite, povondraite, preobrazhenskite, priceite, pringleite, probertite, reedmergnerite, rhodozite, rivadavite, roweite, sabinite, sakhite, santite, sassolite, sborgite, schorl, seamanite, searlesite, serendibite, sibirskite, sinhalite, solongoite, spurrite, stillwellite, strontioborite, studenitsite, sturmanite, suanite, sulfoborite, sussexite, szaibelyite, teepleite, tertschite, tincalconite, tunellite, tusionite, tyretskite, uralborite, veatchite, boric vesuvianite, vistepite, volkovskite, vonsenite, warwickite, wawayandaite, wighmanite, wiluite, and wiserite, among others.
Boron compounds refers, without limitation, to borax (Na₂B₄O₇.10H₂O or pentahydrate, sodium borate, sodium tetraborate, sodium heptaoxotetraborate), borates (compounds that contain boron oxoanions, with boron in oxidation state+3), boranes (boron hydrides).
In the invention, phosphoric acid refers to H₃PO₄. (sometimes called orthophosphoric acid), copper compounds refers, without limitation, to: phosphates, phosphonates, phosphoranes, phosphides, sodium hypophosphite, phosphine oxide, phosphorus pentafluoride, phosphorus trichloride, hexafluorophosphoric acid, phosphorus (III) and (V) acid, among others. Phosphorus minerals refers, without limitation, to phosphoric rocks, such as, for example, lignite, andalusite, aheylite, aldermanite, alforsite, alluaudite, althausite, amblygonite, anapaite, apatite, arctite, ardealite, arupite, augelite, autunite, babefphite, barbosalite, baricite, barringerite, bassetite, bauxite, bearthite, belovite, benauite, beraunite, berlinite, bermanite, bertossaite, beryllonite, beusite, biphosphamite, bobierrite, boggildite, bonshtedtite, brabantite, bradleyite, brazilianite, brianite, britholite, Brushite, buchwaldite, cacoxenite, canaphite, cassidyite, chalcosiderite, cheralite, churchite, chlorapatite, coffinite, collinsite, coeruleolactite, corkite, cornetite, crandallite, crawfordite, curetonite, cyrilovite, diadochite, dittmarite, dorfmanite, dufrenite, dumontite, earlshannonite, ehrleite, eosphorite, fairfieldite, farringtonite, florencite, fluellite, fluorapatite, fluorellestadite, foggite, fornacite, francoanellite, fransoletite, frondelite, furongite, gainesite, galileiite, gatehouseite, gatumbaite, giniite, girvasite, glucine, gorceixite, gordonite, goyazite, graftonite, grattarolaite, grayite, hentschelite, herderite, heterosite, hinsdalite, holtedahlite, hopeite, hotsonite, hureaulite, hurlbutite, hydroxylapatite, hydroxylherderite, hydroxyl-piromorphite, isokite, jagowerite, kaluginite, kidwellite, kingite, kingsmountite, kintoreite, kleemanite, kolbeckite, koninckite, kosnarite, kovdorskite, kribergite, kryzhanovskite, kuksite, lacroixite, landesite, laubmanite, laueite, lazulite, lehnerite, lermontovite, leucophosphite, libethenite, likasite, lipscombite, liroconite, lithiophilite, lithiophosphatite, lithiophosphate, lomonosovite, ludlamite, luneburgite, magniotriplite, mahlmoodite, mangangordonite, maricite, matulaite, metaankoleite, metaswitzerite, metatorbenite, metavariscite, metavauxite, mimetite, mitridatite, monazite, monetite, montebrasite, montgomerite, moraesite, moreauite, morinite, mundite, nabaphite, nafedovite, nalipoite, nasicon, nastrophite, natrophilite, natrophosphato, nefedovite, newberyite, niahite, ningyoite, nissonite, olympite, overite, oxyapatite, parafransoletite, parahopeite, paravauxite, parsonite, paulkellerite, petersite, phosphammite, phosphoellenbergerite, phosphoferrite, phosphofibrite, phosphophyllite, phosphorroslerite, phosphosiderite, phosphovanadylite, phosphuranylite, phosinaite, phuralumite, phurcalite, pyromorphite, pyrophosphite, plumbogummite, pretulite, pseudolaueite, pseudomalachite, purpurite, reichenbachite, robertsite, rockbridgeite, rodolicoite, sabugalite, saleeite, sampleite, satterlyite, scholzite, schreibersite, scorzalite, seamanite, segelerite, senegalite, sengalite, sidorenkite, sieleckiite, sigloite, silicocarnotite, spencerite, stercorite, stewartite, strengite, strunzite, struvite, svanbergite, switzerite, taranakite, tarbuttite tavorite, threadgoldite, tinsleyite, tinticite, triangulite, triphylite, triplite, triploidite, trolleite, turquoise, uralolite, ushkovite, vanmeerscheite, variscite, varulite, vashegyite, vayrynenite, veszelyite, viitaniemiite, vitusita, vivianite, vochtenite, voggite, vuonnemite, vyacheslavite, wagnerite, wardite, wavellite, whitmoreite, wolfeite, woodhouseite, wooldridgeite, ximengite, zairite, zapatalite, zodacite.

Example 1

Application of Different Concentrations of Boric Acid to the Analyzed Copper Minerals

General Protocol:
In this example, the samples used in leaching correspond to oxidized copper minerals, mainly chrysocolla (hydrated copper silicate). 40 g of dry, ground mineral was massed from the samples, over which the base leaching solution, composed of 1000 mL of water, 61 mL of 5% H₂SO₄and, as proposed in the invention, variable amounts of boric acid, was added. The resulting mixture was agitated for 30 minutes at room temperature (20-25° C.) After obtaining a pregnant leaching solution (PLS) of copper, a solvent extraction stage followed. For this, a mixture was prepared with CuPRO MEX 3506®, an organic extractant, dissolved to 10% v/v in Escaid® 110 (ExxonMobil Chemical). The extractant solution was mixed with the PLS in agitation for 15 minutes in a decanting funnel, and the phases were separated.
The organic phase contains a high concentration of copper (RE), and it will be used in the stripping stage. The aqueous phase returns to the leaching stage.
Finally, the organic phase is taken to the electrowinning stage using a lean electrolyte (LE) composed by CuSO₄*5H₂O (Cu=33.36 g/L), sulfuric acid (180 g/L) and water. This electrolyte was stripped with loaded organic (LO) solution in a decanting funnel and maintained in agitation for 15 minutes. After the stripping stage, the organic solution was returned to the extraction stage, and the rich electrolyte (with a concentration over 40 g/L) entered the electrowinning stage. At the end of the electrowinning stage, the electrolyte obtained corresponded to the lean electrolyte.
The parameters for copper recovery were established according to the initial mass and the mass recovered in the various stages of the process.
In Table 1, the standardized parameters for the stages included in the leaching process are presented. PLS corresponds to the product obtained after treating the copper mineral with the leaching solution and LE is lean electrolyte.

TABLE 1

Parameters established for the leaching protocol

	Fluid	Parameter	Value

PLS

Cu Concentration

>1.7

g/L

pH

1.7 to 2.0

RE	Cu Concentration	42-46	g/L
	Sulfuric acid	180	g/L
	concentration

Organic	Dilution	CuPro Max to 9%
		v/v in Escaid
		110

In this example, the effects of a leaching solution composed of: water, 5% sulfuric acid, and variable amounts of boric acid were compared with a conventional leaching solution in a copper extraction process. The tests were performed according to the abovementioned general protocol, using a leaching solution composed of 1000 mL of water, 61 mL of 5% sulfuric acid, and variable amounts of boric acid. The overall amount of copper present in the initial mineral, in the post-filter fluid, and in the washing water, as well as the copper concentration in the PLS were measured (Table 2).
The results indicate that by including boric acid in the leaching process, according to the use of the invention, copper recovery increases up to 10% in comparison with a conventional leaching solution (FIG. 2). The highest percentage of recovery was obtained by aggregating 24.86 g of boric acid H₃BO₃(FIG. 2).
Table 2 presents the reactant volumes and masses used in the copper recovery process with the addition of boric acid in the leaching solution. Additionally, the copper concentration in the filtered fluid (PLS) and in the washing water (WW), and the percentage of copper in the remaining gangue were measured.

TABLE 2

Reactant values and copper recovery in test adding
boric acid to leaching solution.

	Cu in		Sulfuric	Boric		Cu in	Cu in	Cu
Ore	initial	Water	acid	acid	Cu	washing	gan-	Recov-
mass	mineral	volume	volume	mass	in	water	gue	ery
(g)	%	(mL)	(mL)	(g)	LF	(g/L)	(%)	(%)

40	1.21	1000	61	0	0.256	0.033	0.57	52.9
40	1.21	1000	61	10	0.248	0.027	0.59	51.2
40	1.21	1000	61	20	0.296	0.027	0.47	61.2
40	1.21	1000	61	30	0.316	0.032	0.42	65.3
40	1.21	1000	61	40	0.304	0.025	0.50	61.8
40	1.21	1000	61	50	0.320	0.022	0.41	66.1

Total Copper Recovery = [ (copper in supply mineral − copper in gangue)/Copper in supply mineral]* 100

Example 2

Effect of Adding Boron Ore in Copper Leaching

Copper mineral, 5% sulfuric acid, and water is mixed with ulexite (sodium pentahydrate borate and calcium) in amounts equivalent to 5, 10, 15, 20, and 25 g of boric acid, respectively.
This mixture is agitated for 30 minutes and then filtered, thereby obtaining the PLS, which is analyzed chemically to determine its copper (Cu) content. The remaining solid (gangue) is washed with 250 mL of water. The washing water (WW) is analyzed chemically to determine is copper content. The wet gangue is dried, weighed, crushed, and homogenized so it can be analyzed chemically to determine its copper content.

TABLE 3

Tests with ulexite

	Equivalent
	boric acid	Cu
Ulexite	mass in	mass in	Cu mass in	Cu mass in	Total copper
mass g	ulexite g	PLS g	WW g	gangue g	recovery %

0	0	0.23	0.0121	0.240	50.41
17.59	5	0.24	0.0122	0.231	52.37
35.18	10	0.25	0.0110	0.226	53.41
52.78	15	0.27	0.0117	0.211	56.48
70.38	20	0.28	0.0121	0.198	59.14
87.97	25	0.29	0.0114	0.192	60.33

Total Copper Recovery = [(copper in supply ore − copper in gangue)/Copper in supply ore] * 100

In FIG. 3, the amount of copper present in the PLS in comparison with the amount of ulexite added can be seen. A significant positive effect in copper recovery in the PLS by adding ulexite to the leaching process is observed.
As a result of the invention, copper mineral leaching is improved by adding the ore from which the weak acid is generated.

Example 3

Effect of Adding Orthophosphoric Acid in the Leaching Solution in the Copper Recovery Process

In this example, the effect of a leaching solution composed of water, 5% sulfuric acid, and variable volumes of technical grade orthophosphoric acid concentrate in the copper mineral refinement process was determined. The new leaching solution was tested by following the abovementioned protocol with a base solution composed of 1000 mL of water, 61 mL of 5% sulfuric acid, and various volumes of orthophosphoric acid added, as shown in Table 7.

TABLE 7

Reactant volumes used in the leaching solution composed
of 85% concentration orthophosphoric acid.

	5% Sulfuric	H₃PO₄
Water volume	acid volume	volume	Total Cu
(mL)	(mL)	(mL)	recovery %

1000	61	0	65.01
1000	61	10	68.90
1000	61	20	72.97
1000	61	30	72.35

The addition of orthophosphoric acid to the leaching solution generated a greater percentage of recovered copper in comparison with a conventional leaching solution (without orthophosphoric acid). The maximum amount of recovered mineral occurred when 20.6 mL of orthophosphoric acid H₃PO₄was added to a concentration of 85 gr/L (FIG. 4).

FIGURE DESCRIPTION

FIG. 1. Global process of copper recovery from minerals. The figure shows the stages that comprise the general copper extraction procedure: leaching, extraction, stripping, and electrowinning, as well as the products and intermediate steps for each stage.
FIG. 2. Effect of a leaching solution with boric acid in copper recovery. a) The graphic shows the increase in copper recovery percentage through the addition of boric acid (g) to the leaching solution. b) The curve represents the increase in the copper concentration (g/L) contained in the PLS through the addition of boric acid (g) to the leaching solution during copper recovery.
FIG. 3. Effect of the addition of ulexite on copper recovery in the leaching process. a) The graphic shows the increase in the copper recovery percentage through the addition of ulexite ore to the leaching solution. b) The curve represents the increase in the copper concentration in the PLS through the addition of ulexite ore to the leaching solution during copper recovery.
FIG. 4. Effect of the addition of orthophosphoric acid in a leaching solution on copper recovery. a) The graphic shows the increase in the copper recovery percentage through the addition of orthophosphoric acid (g) to the leaching solution. b) The curve represents the increase in the copper concentration (g/L) in the PLS in comparison with the amount of boric acid (g) added to the leaching solution during the extraction process.

Claims

1. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same COMPRISING an increase in copper recovery from mineral and/or to increase the copper concentration of the pregnant leach solution in the copper leaching process.

2. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper leaching of claim 1 COMPRISING a weak acid that can be, among others, boric acid or phosphoric acid.

3. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper leaching of claim 1 COMPRISING a weak acid that is preferably boric acid, also called orthoboric acid.

4. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper leaching of claim 1 COMPRISING a weak acid that is preferably phosphoric acid, also called orthophosphoric acid.

5. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper leaching of claim 1 COMPRISING a mineral that contains boron or phosphorus.

6. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper leaching of claim 1 COMPRISING a mineral that contains boron.

7. Use of oxygenated and polyoxygenated weak acids, or minerals or compounds that generate the same in the copper leaching of claim 1 COMPRISING a mineral that contains phosphorus.

8. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper leaching of claim 1 COMPRISING a boron ore that can be selected, without limitation, from ulexite, colemanite, kernite, pandermite, bakerite, datolite, elbaite, admontite, aksaite, ameghinite, ammonioborite, aristarainite, avogadrite, axinite, bandylite, barberiite, behierite, berborite, biringuccite, boracite, boralsilite, borax, borazon, borcarite, bormuscovite, cahnite, calciborite, carboborite, chambersite, charlesite, congolite, danburite, datolite, diomignite, dravite, dumortierite, eremeevite, ericaite, ezcurrite, fabianite, ferruccite, flolovite, fluoborite, foitite, frolovite, garrelsite, gaudefroyite, ginorite, gowerite, halurgite, hambergite, heidornite, henmilite, hexahydroborite, hydroboracite, hydrochlorborite, hilgardite, holtite, howlite, hulsite, hungchaoite, inderborite, inderite, inyoite, jeremejevite, jimboite, kalborsite, karlite, katoite, kornerupine, kotoite, kurnakovite, lardarellite, ludwigite, lueneburgite, luidwigite, manandonite, mcallisterite, metaborite, meyerhofferite, moydite, nasinite, nifontovite, nobleite, nordenskjoeldine, olenite, oyelite, painite, pentahydroborate, pinnoite, povondraite, preobrazhenskite, priceite, pringleite, probertite, reedmergnerite, rhodozite, rivadavite, roweite, sabinite, sakhite, santite, sassolite, sborgite, schorl, seamanite, searlesite, serendibite, sibirskite, sinhalite, solongoite, spurrite, stillwellite, strontioborite, studenitsite, sturmanite, suanite, sulfoborite, sussexite, szaibelyite, teepleite, tertschite, tincalconite, tunellite, tusionite, tyretskite, uralborite, veatchite, boric vesuvianite, vistepite, volkovskite, vonsenite, warwickite, wawayandaite, wighmanite, wiluite, and wiserite, among others.

9. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper leaching of claim 1 COMPRISING a phosphorus mineral that can be selected, without limitation, from aheylite, aldermanite, alforsite, alluaudite, althausite, amblygonite, anapaite, apatite, arctite, ardealite, arupite, augelite, autunite, babefphite, barbosalite, baricite, barringerite, bassetite, bauxite, bearthite, belovite, benauite, beraunite, berlinite, bermanite, bertossaite, beryllonite, beusite, biphosphamite, bobierrite, boggildite, bonshtedtite, brabantite, bradleyite, brazilianite, brianite, britholite, brushite, buchwaldite, cacoxenite, canaphite, cassidyite, chalcosiderite, cheralite, churchite, chlorapatite, coffinite, collinsite, coeruleolactite, corkite, cornetite, crandallite, crawfordite, curetonite, cyrilovite, diadochite, dittmarite, dorfmanite, dufrenite, dumontite, earlshannonite, ehrleite, eosphorite, fairfieldite, farringtonite, florencite, fluellite, fluorapatite, fluorellestadite, foggite, fornacite, francoanellite, fransoletite, frondelite, furongite, gainesite, galileiite, gatehouseite, gatumbaite, giniite, girvasite, glucine, gorceixite, gordonite, goyazite, graftonite, grattarolaite, grayite, hentschelite, herderite, heterosite, hinsdalite, holtedahlite, hopeite, hotsonite, hureaulite, hurlbutite, hydroxylapatite, hydroxylherderite, hydroxyl-piromorphite, isokite, jagowerite, kaluginite, kidwellite, kingite, kingsmountite, kintoreite, kleemanite, kolbeckite, koninckite, kosnarite, kovdorskite, kribergite, kryzhanovskite, kuksite, lacroixite, landesite, laubmanite, laueite, lazulite, lehnerite, lermontovite, leucophosphite, libethenite, likasite, lipscombite, liroconite, lithiophilite, lithiophosphatite, lithiophosphate, lomonosovite, ludlamite, luneburgite, magniotriplite, mahlmoodite, mangangordonite, maricite, matulaite, metaankoleite, metaswitzerite, metatorbenite, metavariscite, metavauxite, mimetite, mitridatite, monazite, monetite, montebrasite, montgomerite, moraesite, moreauite, morinite, mundite, nabaphite, nafedovite, nalipoite, nasicon, nastrophite, natrophilite, natrophosphato, nefedovite, newberyite, niahite, ningyoite, nissonite, olympite, overite, oxyapatite, parafransoletite, parahopeite, paravauxite, parsonite, paulkellerite, petersite, phosphammite, phosphoellenbergerite, phosphoferrite, phosphofibrite, phosphophyllite, phosphorroslerite, phosphosiderite, phosphovanadylite, phosphuranylite, phosinaite, phuralumite, phurcalite, pyromorphite, pyrophosphite, plumbogummite, pretulite, pseudolaueite, pseudomalachite, purpurite, reichenbachite, robertsite, rockbridgeite, rodolicoite, sabugalite, saleeite, sampleite, satterlyite, scholzite, schreibersite, scorzalite, seamanite, segelerite, senegalite, sengalite, sidorenkite, sieleckiite, sigloite, silicocarnotite, spencerite, stercorite, stewartite, strengite, strunzite, struvite, svanbergite, switzerite, taranakite, tarbuttite, tavorite, threadgoldite, tinsleyite, tinticite, triangulite, triphylite, triplite, triploidite, trolleite, turquoise, uralolite, ushkovite, vanmeerscheite, variscite, varulite, vashegyite, vayrynenite, veszelyite, viitaniemiite, vitusita, vivianite, vochtenite, voggite, vuonnemite, vyacheslavite, wagnerite, wardite, wavellite, whitmoreite, wolfeite, woodhouseite, wooldridgeite, ximengite, zairite, zapatalite, and zodacite, among others.

10. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper leaching of claim 1 COMPRISING a compound that can be, among others, a boron compound.

11. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper leaching of claim 1 COMPRISING a compound that can be, among others, a phosphorus compound.

12. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper leaching of claim 10 COMPRISING a compound that is a boron compound, selected preferably, without limitation, from borax, borates, and boranes, among others.

13. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper leaching of claim 11 COMPRISING a compound that is a phosphorus compound, selected preferably, without limitation, from phosphonates, phosphoranes, phosphide, sodium hypophosphite, phosphine oxide, phosphorus pentafluoride, phosphorus trichloride, hexafluorophosphoric acid, and phosphorus (III) and (V) acid, among others.

14. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper leaching of claim 1 COMPRISING an increase in copper recovery from said mineral.

15. A copper leaching procedure COMPRISING:

addition of a necessary amount of an oxygenated or polyoxygenated weak acid, or a compound or a mineral that generates the same to said leaching process.

Simultaneously adding sulfuric acid to the leaching heap.

where said necessary amount of oxygenated or polyoxygenated weak acid will depend on the characteristics of said mineral.

16. A copper leaching procedure of claim 14 COMPRISING the addition of an oxygenated or polyoxygenated weak acid, preferably, to said leaching heap.

17. A copper leaching procedure of claim 15 COMPRISING said weak acid, preferably, boric or phosphoric acid.

18. A copper leaching procedure of claim 14 COMPRISING said mineral added to said leaching process.

19. A copper leaching procedure of claim 17 COMPRISING said mineral, preferably, a boron or phosphorus mineral.

20. A copper leaching procedure of claim 17 COMPRISING said compound, preferably, a boron or phosphorus compound.

21. A copper leaching procedure of claim 17 COMPRISING said compound, preferably selected from borax, borates, and boranes, among others.

22. A copper leaching procedure of claim 17 COMPRISING said compound, preferably selected from borax.

23. A copper leaching procedure of claim 17 COMPRISING said compound, preferably selected from phosphates, phosphonates, phosphoranes, phosphites, phosphides, sodium hypophosphite, phosphine oxide, phosphorus pentafluoride, phosphorus trichloride, hexafluorophosphoric acid, and phosphorus (III) and (V) acid, among others.

24. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same COMPRISING an increase in copper recovery from mineral and/or to increase copper concentration of the solution in the copper bioleaching process.

25. Use of weak acids or oxygenated or polyoxygenated minerals or compounds that generate the same in the copper bioleaching of claim 21 COMPRISING a weak acid that can be, among others, boric acid or phosphoric acid.

26. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper bioleaching of claim 24 COMPRISING a weak acid that is preferably boric acid, also called orthoboric acid.

27. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper bioleaching of claim 24 COMPRISING a weak acid that is preferably phosphoric acid, also called orthophosphoric acid.

28. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper bioleaching of claim 24 COMPRISING a mineral that contains boron or phosphorus.

29. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper bioleaching of claim 24 COMPRISING a mineral that contains boron.

30. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper bioleaching of claim 24 COMPRISING a mineral that contains phosphorus.

31. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper bioleaching of claim 24 COMPRISING a boron mineral that can be selected, without limitation, from ulexite, colemanite, kernite, pandermite, bakerite, datolite, elbaite, admontite, aksaite, ameghinite, ammonioborite, aristarainite, avogadrite, axinite, bandylite, barberiite, behierite, berborite, biringuccite, boracite, boralsilite, borax, borazon, borcarite, bormuscovite, cahnite, calciborite, carboborite, chambersite, charlesite, congolite, danburite, datolite, diomignite, dravite, dumortierite, eremeevite, ericaite, ezcurrite, fabianite, ferruccite, flolovite, fluoborite, foitite, frolovite, garrelsite, gaudefroyite, ginorite, gowerite, halurgite, hambergite, heidornite, henmilite, hexahydroborite, hydroboracite, hydrochlorborite, hilgardite, holtite, howlite, hulsite, hungchaoite, inderborite, inderite, inyoite, jeremejevite, jimboite, kalborsite, karlite, katoite, kornerupine, kotoite, kurnakovite, lardarellite, ludwigite, lueneburgite, luidwigite, manandonite, mcallisterite, metaborite, meyerhofferite, moydite, nasinite, nifontovite, nobleite, nordenskjoeldine, olenite, oyelite, painite, pentahydroborate, pinnoite, povondraite, preobrazhenskite, priceite, pringleite, probertite, reedmergnerite, rhodozite, rivadavite, roweite, sabinite, sakhite, santite, sassolite, sborgite, schorl, seamanite, searlesite, serendibite, sibirskite, sinhalite, solongoite, spurrite, stillwellite, strontioborite, studenitsite, sturmanite, suanite, sulfoborite, sussexite, szaibelyite, teepleite, tertschite, tincalconite, tunellite, tusionite, tyretskite, uralborite, veatchite, boric vesuvianite, vistepite, volkovskite, vonsenite, warwickite, wawayandaite, wighmanite, wiluite, and wiserite, among others.

32. Use of oxygenated or polyoxygenated weak acids, or minerals that generate the same in the copper bioleaching of claim 24 COMPRISING a phosphorus mineral that can be selected, without limitation, from aheylite, aldermanite, alforsite, alluaudite, althausite, amblygonite, anapaite, apatite, arctite, ardealite, arupite, augelite, autunite, babefphite, barbosalite, baricite, barringerite, bassetite, bauxite, bearthite, belovite, benauite, beraunite, berlinite, bermanite, bertossaite, beryllonite, beusite, biphosphamite, bobierrite, boggildite, bonshtedtite, brabantite, bradleyite, brazilianite, brianite, britholite, brushite, buchwaldite, cacoxenite, canaphite, cassidyite, chalcosiderite, cheralite, churchite, chlorapatite, coffinite, collinsite, coeruleolactite, corkite, cornetite, crandallite, crawfordite, curetonite, cyrilovite, diadochite, dittmarite, dorfmanite, dufrenite, dumontite, earlshannonite, ehrleite, eosphorite, fairfieldite, farringtonite, florencite, fluellite, fluorapatite, fluorellestadite, foggite, fornacite, francoanellite, fransoletite, frondelite, furongite, gainesite, galileiite, gatehouseite, gatumbaite, giniite, girvasite, glucine, gorceixite, gordonite, goyazite, graftonite, grattarolaite, grayite, hentschelite, herderite, heterosite, hinsdalite, holtedahlite, hopeite, hotsonite, hureaulite, hurlbutite, hydroxylapatite, hydroxylherderite, hydroxyl-piromorphite, isokite, jagowerite, kaluginite, kidwellite, kingite, kingsmountite, kintoreite, kleemanite, kolbeckite, koninckite, kosnarite, kovdorskite, kribergite, kryzhanovskite, kuksite, lacroixite, landesite, laubmanite, laueite, lazulite, lehnerite, lermontovite, leucophosphite, libethenite, likasite, lipscombite, liroconite, lithiophilite, lithiophosphatite, lithiophosphate, lomonosovite, ludlamite, luneburgite, magniotriplite, mahlmoodite, mangangordonite, maricite, matulaite, metaankoleite, metaswitzerite, metatorbenite, metavariscite, metavauxite, mimetite, mitridatite, monazite, monetite, montebrasite, montgomerite, moraesite, moreauite, morinite, mundite, nabaphite, nafedovite, nalipoite, nasicon, nastrophite, natrophilite, natrophosphato, nefedovite, newberyite, niahite, ningyoite, nissonite, olympite, overite, oxyapatite, parafransoletite, parahopeite, paravauxite, parsonite, paulkellerite, petersite, phosphammite, phosphoellenbergerite, phosphoferrite, phosphofibrite, phosphophyllite, phosphorroslerite, phosphosiderite, phosphovanadylite, phosphuranylite, phosinaite, phuralumite, phurcalite, pyromorphite, pyrophosphite, plumbogummite, pretulite, pseudolaueite, pseudomalachite, purpurite, reichenbachite, robertsite, rockbridgeite, rodolicoite, sabugalite, saleeite, sampleite, satterlyite, scholzite, schreibersite, scorzalite, seamanite, segelerite, senegalite, sengalite, sidorenkite, sieleckiite, sigloite, silicocarnotite, spencerite, stercorite, stewartite, strengite, strunzite, struvite, svanbergite, switzerite, taranakite, tarbuttite, tavorite, threadgoldite, tinsleyite, tinticite, triangulite, triphylite, triplite, triploidite, trolleite, turquoise, uralolite, ushkovite, vanmeerscheite, variscite, varulite, vashegyite, vayrynenite, veszelyite, viitaniemiite, vitusita, vivianite, vochtenite, voggite, vuonnemite, vyacheslavite, wagnerite, wardite, wavellite, whitmoreite, wolfeite, woodhouseite, wooldridgeite, ximengite, zairite, zapatalite, and zodacite, among others.

33. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper bioleaching of claim 24 COMPRISING a compound that can be, among others, a boron compound.

34. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper bioleaching of claim 24 COMPRISING a compound that can be, among others, a phosphorus compound.

35. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper bioleaching of claim 33 COMPRISING a compound that is a boron compound, selected preferably, without limitation, from borax, borates, and boranes, among others.

36. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper bioleaching of claim 34 COMPRISING a compound that is a phosphorus compound, selected preferably, without limitation, from phosphonates, phosphoranes, phosphide, sodium hypophosphite, phosphine oxide, phosphorus pentafluoride, phosphorus trichloride, hexafluorophosphoric acid, and phosphorus (III) and (V) acid, among others.

37. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper bioleaching of claim 24 COMPRISING an increase in copper recovery from said mineral.

38. A copper bioleaching procedure COMPRISING:

addition of a necessary amount of an oxygenated or polyoxygenated weak acid, or a compound or a mineral that generates the same to said bioleaching process.

Simultaneously adding sulfuric acid to said bioleaching heap or dump site.

The necessary amount of weak acid added will depend on the characteristics of the mineral to be bioleached.

39. A copper bioleaching procedure of claim 24 COMPRISING the addition of an oxygenated or polyoxygenated weak acid, preferably, to said bioleaching process.

40. A copper bioleaching procedure of claim 25 COMPRISING said weak acid, preferably, boric or phosphoric acid.

41. A copper leaching procedure of claim 24 COMPRISING said mineral added to said bioleaching process.

42. A copper bioleaching procedure of claim 27 COMPRISING said mineral, preferably, a boron or phosphorus mineral.

43. A copper bioleaching procedure of claim 27 COMPRISING said compound, preferably, a boron or phosphorus compound.

44. A copper bioleaching procedure of claim 27 COMPRISING said compound, preferably selected from borax, borates, and boranes, among others.

45. A copper bioleaching procedure of claim 27 COMPRISING said compound, preferably selected from borax.

46. A copper bioleaching procedure of claim 27 COMPRISING said compound, preferably selected from phosphates, phosphonates, phosphoranes, phosphites, phosphides, sodium hypophosphite, phosphine oxide, phosphorus pentafluoride, phosphorus trichloride, hexafluorophosphoric acid, and phosphorus (III) and (V) acid, among others.

47. Use of solid and liquid wastes from plants producing oxygenated or polyoxygenated weak acids and their derivatives COMPRISING an increase in copper recovery from mineral and/or to increase the copper concentration of the pregnant leach solution in said copper leaching process or copper bioleaching process.

48. Use of solid and liquid wastes from plants producing oxygenated or polyoxygenated weak acids and their derivatives COMPRISING an increase in copper recovery from mineral and/or to increase the copper concentration of the pregnant leach solution in said copper leaching process.

49. Use of solid and liquid wastes from plants producing boric acid, borax, and phosphoric acids and their derivatives COMPRISING an increase in copper recovery from mineral and/or to increase the copper concentration of the pregnant leach solution in said copper bioleaching process.

50. Use of oxygenated or polyoxygenated weak acids, or minerals or compounds that generate the same in the copper leaching or bioleaching of claim 1 COMPRISING an acid having a dissociation constant that varies between 1.80×10⁻¹⁶and 55.50, except for carbonic acid.