WO2003056043A1

WO2003056043A1 - Recovery of platinum group metals from mining tails

Info

Publication number: WO2003056043A1
Application number: PCT/BR2002/000123
Authority: WO
Inventors: Juarez Dos Santos Fontana
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-12-31
Filing date: 2002-09-02
Publication date: 2003-07-10
Anticipated expiration: 2004-06-30
Also published as: AU2002325695A1; BR0107258A

Abstract

The present invention was structured by the author to make feasible the industrial recovery of Platinum Group Metals-PGM and oth er noble metals through the processing of spinel minerals. The spinel minerals are rejected in phosphate, titanium, niobium, vanadium, uranium, copper, aluminium, iron, vermiculite, and other mining operations in many places around the world. The spinel minerals are deleterious for the recovery of these mineral goods, so they are settled down in dams or piles. They are not applied for any kind of commercial regular use. The research developed by several mineralogists, including those provided by the inventor, are pointing out that the rejected mining tails rich in spinel minerals, especially those resulting from mining operations related to the magmatic alkalic intrusive rocks, could generate alternative sources for PGM and other noble metals. The preliminary survey performed with the composite samples of the rejected material from four Brazilian mines of phosphate, aluminium, niobium, titanium and uranium were considered very positive. They provide encouragement to proceed with the research, looking to establish an alternative source for the PGM.

Description

"RECOVERY OF PLATINUM GROUP METALS FROM MINING TAILS"

The present patent application provides a description of some combined operations that will result in the recovery of Platinum Group Metals (PGM) and other noble metals by processing some types of mining tails. This innovative mining and metallurgical procedure will provide an alternative source for obtaining those rare metals, so useful in the electronics and environmental industries.

The Platinum Group Metals (PMG) present quite similar physical and chemical properties. The PMG are represented by platinum (Pt), palladium (Pd), Iridium (Ir), rhodium (Rh), ruthenium (Ru) and osmium (Os). Their physical and chemical properties are very peculiar: high hardness; high melting point; low chemical reactivity and high resistance to corrosion.

The most specific property of the PMG is their catalyst quality, the key for the most important field of their industrial application: production of automobile catalytic converters; industrial and home exhausters; ionic exchange batteries, etc. PMG are particularly useful in solving environmental problems related to the control of gas emissions from internal explosion engines, diesel oil burning and stationary engines. The PMG are known as rare and noble elements, because there are few exploitable mineral reserves and their production is concentrated in only two countries: South Africa (Bushveld Complex) and Russia - Siberia (Noril'sk -Talnakh Complex)

All information about PMG is classified, but in 1990 the US Bureau of Mines estimated the world PMG reserve in 66,100 metric tons, contained in sixteen ore bodies. Twelve of them were located in South Africa.

The PMG production from primary ores (whose economic feasibility depends primarily from the PMG output) comes from mining of ore bodies of mafic and/or ultramafic rock origin which are components of stratiform magmatic deposits occurring at the Busveld magmatic intrusion - Merensky Reef, UG-2 and Platreef levels (South Africa) and in the Stillwater magmatic intrusion (United States of America).

They are also recovered as an economic by-product of the mining and metallurgy of nickel, copper and cobalt ore, as is the case in the magmatic intrusions in Sudbury (Canada) or in Noril'sk Talnakh (Russia - Siberia).

Nowadays the yearly world PMG production ranges from 350 to 400 tons, a supply volume that barely meets the world's industrial demand. In fact there is a repressed demand for PMG, resulting in sustained high metal prices.

Considering the high prices of the metal, the short supply and the scarcity of PMG ore occurrence, recycling PMG is becoming an important supply source. The most important recycling process is related to the recovery of PMG from automotive catalytic converter scrap. This process alone is responsible for supplying 6% of the world's platinum demand.

The Republic of South Africa produces almost 70% of the PMG world mining supply. Russia alone was responsible, until 1997, for 15-20% of the PMG world mining output. Russia also furnishes almost 50% of the palladium world demand, because their PMG ores are especially rich in palladium.

The PMG are produced and sold by few and powerful transnational corporations, constituting a cartel.

During the last decades, substantial scientific research conducted by mineralogists from several countries, has indicated the relevance of some types of magmatic minerals showing premature crystallization, such as those of the spinel^* group which, depending on the original magmatic chemical composition, could present high noble metals content (gold, silver and PMG).

* The minerals of the spinel group are defined as premature magmatic minerals. They form isometric (cubic) crystals and present a variable isomorphic chemical composition, with the following variable formula: Xi Y₂ O_4j , where X could be represented by the following ions, alone or combined:

Fe^{2 +}, Mg, Zn, Mn or Ni, and where Y could be the following ions, alone or combined: Al, Fe³⁺ , Cr, Ti, V or Mn.

The most usual spinel minerals are: spinel - MgAl₂O₄, gahnite - ZnAl₂0 _ι hercynite - FeAl₂O₄, magnetite - Fe ⁺Fe³⁺ ₂ 0_4>, chromite - FeCr₂O₄ , franklinite - (Zn, Mn²⁺, Fe²⁺ ) (Fe³⁺, Mn³⁺ )₂ O₄ and magnesium-chromite - Mg Cr₂O . Magnetite, for instance, is an iron oxide that admits partial exchange between the two iron ions Fe²⁺ and Fe³⁺) and other metal ions, inside its crystalline structure. These ion interchanges result in the following general chemical formula for the magnetite: (Fe, Mn, Mg,Zn,Ni)²⁺ (Fe, Al, Cr, Ti, Mn, V)³⁺ ₂ O₄. The most relevant physical and chemical properties of magnetite are: color: black: streak: black; hardness: 51/2 to 61/2; isometric (cubic) crystal system; specific weigh: 5.5 to 6.5 g/cm³, varieties: titanium-magnetite rich in Ti, chromium-magnetite, rich in Cr; peculiar characteristics: strongly magnetic mineral. As defined by the "Glossary of Geology", 1974, published by the American Geological Institute and by the John Betts - Fine Minerals, Online Mineral Gallery home page: ft1 p://minerals.nct/nιincral oxides/magnetitey

Research done by mineralogists reveal that some types of spinel could contain high concentrations of PMG (> 200 ppm = 200 g/t), These PMG contents represent up to 40 times the economic cut-off grade for PMG ores (~ 5 ppm = 5g/t). But if one considers that spinel represents only 1 ,5 to 2% of the whole rock volume, the final rock PMG content will be uneconomic: -4 ppm = 4 g/t (200/50=4). This effect could be explained by the dilution of the PMG content in spinel by a rate ~ 1/50, as a direct result of the low concentration of spinel in the rock (~ 2%).

This fact, viewed as a single piece of information, is no more than a scientific curiosity, but under special conditions this phenomenon, in combination with some natural or artificial processes, could result in high spinel concentration and also in an unusual economic source of PMG.

The fluvial and/or marine dynamics provide a natural concentration process of spinel. The alluvial sediments could have high spinel content resulting in heavy mineral deposits also named black sand deposits. Some alluvial deposits located in Alaska and in the

Canadian east coast, present black sand concentration levels, containing spinel minerals and high gold and PMG content. The Goodnews Bay ore deposit could be pointed out as an example. Mining of its alluvial sediments, rich in spinel, supported the commercial exploitation of gold and PMG during several years. So far the artificial processes for concentration of spinel minerals have not been given any importance. The mining and ore dressing for several kinds of ores, derived from magmatic alkakine rocks, results in huge concentrations of spinel minerals, in several places spread all over the world.

These magmatic alkaline rocks host ores such as aluminium, phosphate, niobium, titanium, iron, uranium, copper, vermiculite, etc. The mining and ore dressing of those ores result in the dismantling and comminution of the rock and the consequent liberation of the spinel minerals. Considering that the spinel minerals are deleterious for the recovery of those mineral goods, they are settled down in a dam or in the mining tail piles. This fact could be observed in the Brazilian mines of phosphate, niobium, aluminium, titanium and uranium. They are located in alkaline magmatic intrusive rocks in Jacupiranga - SP; Araxa - MG; Pocos de Caldas - MG and CatalSo - GO. The same phenomenon occurs in the mine of phosphate, copper, uranium and vermiculite located in the alkaline magmatic intrusion of Palabora, South Africa. It could be also reported in a number of mines all over the world.

The Brazilian operations are continuously mining huge rock volumes along the last thirty years. The mining tail piles of these mines contain more than forty million tons of spinel minerals. The rejected material does not have relevant economic application, in spite of being a costly environmental trouble. The huge mining operation of Palabora, South Africa, produces phosphate, copper, uranium and vermiculite, but also are pilling, along the last forty years, more than 300 million tons of spinel concentrate. Just as in the Brazilian mines, the rejected material does not presents any relevant economic application. The same phenomenon would be registered in dozens of mines, in several countries located in Latin America, North America, Europe, Asia, Africa and Australia.

The main purpose of the present invention patent application is related to the idealization of some combined processes to recover PMG and other noble metals from the spinel minerals settled down in those dams or in the mining tail piles.

Along the last 10 years the inventor developed with her own resources a directed research, supported by the following criteria:

1 ) The alkaline magmatic rocks potentially bear spinel minerals rich in PMG and noble metals; 2) The Brazilian mines of phosphate, aluminium, niobium, titanium and uranium, result in huge volume of spinel concentrates, settled down in tail piles; 3) The mining tails, enriched in spinel minerals, presently do not represent commercial goods, but just a costly environmental trouble.

In 1993 the inventor paid for a field trip to make random samplings in those mining tail piles. Tails were sampled from Mineracao Serrana (Jacupiranga) in the state of Sao Paulo; from Mineracao Arafertil (Araxa- Pocos de Caldas) in the state of Minas Gerais and from Mineragao Catalao (Catalao) in the state of Goias. The objective of the sampling field trip was to verify the potential of the spinel concentrate as an alternative source to recover PMG and noble metals.

During 1993 four compound samples, weighing five kilos each, were sent to Ukraine. The IBCC, the Biocoloidal Chemistry Research Institute of Ukraine in Kiev was hired to perform a comprehensive research, including detailed mineralogical and chemical assays, to identify the total content of PMG and noble metals in the samples. The direct lab cost was US$ 3 thousand.

Along the second semester in 1994, the IBCC scientists performed several lab experiments and assays, with the support of several analytical equipments and lab routines. The data they obtained were so surprising they decided to ask for help from researchers in the Noril'sk Project Organization Crystal - NPO, in Siberia. NPO is recognized worldwide as one of the most qualified centres for PMG assays and metallurgical studies. In the beginning of 1995, after several cross checks, the scientists of IBCC issued official reports about the research they had conducted. The IBCC reports underline the high PMG and noble metal content in several samples (see attached copies of some IBCC reports). The sample collected in Catalao is surprisingly rich in PMG, gold and silver, but its most important feature is its unusual high content of rhodium (Ro), a very scarce and expensive metal.

The Russian and Ukranian scientists were very enthusiastic about the results of the research and strongly recommended its follow- up. They also suggested a continuation of the survey to identify the main ore dressing characteristics of the material and to improve the lab and bench experiments to define the best metallurgical extraction route.

*³ Considering the N.Y. refined metal spot market on December 6th, 2001. Considering the guidelines proposed by the inventor, the data reported by the IBCC makes sense and gives encouragement to proceed with the research. But, the continuation of the survey will require:

1) High investments as risk money. A preliminary estimation indicates an amount from R$ 250 thousand up to R$ 2.5 million;

2) To perform an appropriate survey it will be necessary to hire a multidisciplinary research team, composed by Brazilian and foreign scientists. It will be necessary to open all the classified data, presently controlled by the inventor. 3) To make regular agreements with the mining corporations in charge of the mines which exhibit the appropriate dams or piles of tails enriched in spinel.

4) To protect her previous investment and to assure the exclusive property or privilege to the inventor. In other words, to proceed with the research without the application of a patent of invention, would be equivalent to making public all the knowledge cumulated by the inventor along the last ten years.

The present application for a patent of invention, as defined above, is unpublished and innovative because: 1) It looks to give economic application to mining rejected material, that does not have present relevant commercial destination;

2) It promotes new alternative sources for noble metals and PMG. These metals have a high rate of demand and are endowed with top economic and social relevance for the human society; 3) It establishes a non conventional technical pattern to recover PMG and noble metals because: a) instead to recover the metals from natural orebodies, it is directed to recycling mining rejected material; b) the cost of metal production will be very low, when compared with the conventional mining operation (competitive advantage) and c) should the survey be successful, it would make the dissemination of PMG production centres in several other countries feasible, in addition to South Africa and Russia.

Considering the above data and justification, the inventor asks the present invention patent application, as defined in the following

CLAIMS.

Claims

1) "RECOVERY OF PLATINUM GROUP METALS FROM

MINING TAILS", comprising the processing of spinel minerals accumulated in dams or piles of rejected tails, resulting from phosphate, titanium, aluminium, niobium, iron, copper, uranium, vanadium, vermiculite and other mining operations, connected with alkaline magmatic intrusive rocks, applying extractive pyrometallurgy route.

2) Recovery of Platinum Group Metals and other noble metals from mining tails, comprising the processing of spinel minerals accumulated in dams or piles of rejected tails, resulted from phosphate, titanium, aluminium, niobium, iron, copper, uranium, vanadium, vermiculite and other mining operations, connected with alkaline magmatic intrusive rocks, applying extractive pyrometallurgy route.

3) Recovery of Platinum Group Metals from mining tails, according to claim 1), by the application of extractive hydrometallurgy route.

4) Recovery of Platinum Group Metals and other noble metals from mining tails, according to claim 2), by the application of extractive hydrometallurgy route.

5) Recovery of Platinum Group Metals from mining tails, according to claim 1), by the application of extractive biohydrometallurgy route.

6) Recovery of Platinum Group Metals and other noble metals from mining tails, according to claim 2), by the application of extractive biohydrometallurgy route.