CN108529799A - The method that photodissociation network strengthens heavy metal complexing waste water reclaiming - Google Patents

Abstract

The invention discloses a method for resource utilization of heavy metal complex wastewater by photolysis and complexation. The specific steps are as follows: after filtering the complex wastewater containing target heavy metals, adding iron reagents and performing aeration treatment; the step (1) pump the effluent into the photoreactor for photocatalytic decomplexation; pump the effluent of step (2) into the I-level adsorption column filled with type A adsorbent to recover the target heavy metal ions; pump the effluent of step (3) into the filled resin The II-level adsorption column of the B-type adsorbent extracts ferric ions; after the adsorption column in step (4) penetrates, pump the regenerant into the II-level adsorption column for regeneration, and recover the ferric ions for desorption Liquid; the present invention realizes the selective separation of heavy metal ions and externally added Fe(III) ions through the integrated strengthening of photocatalytic decomplexation and the integrated control of selective adsorption process, and realizes the resource utilization of heavy metals and the recycling of iron , greatly reducing drug consumption and energy consumption.

Description

Method of Photodecomplexation Strengthening Recycling of Heavy Metal Complex Wastewater

technical field

The invention relates to a method for photodecomplexation strengthening heavy metal complexation waste water recycling, which belongs to the field of waste water treatment.

Background technique

Complex heavy metals are widely present in natural water bodies and industrial water bodies. NOM and DOM in natural water mostly contain ligand functional groups such as hydroxyl, amino and carboxyl, which can easily form soluble heavy metal chelates with heavy metals, preventing the deposition of heavy metal ions in natural water. In order to ensure the quality of the plating layer during the electroplating process, a large amount of complexing agents need to be added to the plating solution, resulting in the presence of heavy metals in the electroplating wastewater in a complex state. In the presence of inorganic or organic ligands, the mobility of heavy metals is enhanced, which will promote bioabsorption and increase the enrichment of heavy metals. Therefore, compared with ionic heavy metals, complexed heavy metals will have a greater impact on aquatic organisms. Therefore, how to simply and effectively remove complex heavy metals has become a difficult problem to be solved in the field of heavy metal wastewater treatment.

Compared with ionic heavy metals, complexed heavy metals are surrounded by multiple coordination atoms such as N or O to form mononuclear or multinuclear polydentate chelates with high stability coefficients, making it difficult to pass through traditional methods. Coagulation sedimentation, chemical precipitation and ion exchange methods to remove. The chelation adsorption method has a better selective separation effect on free heavy metal ions, but poor selective separation effect on complexed heavy metals, because the complexing agent wraps heavy metal ions in it and completely occupies its coordination. sites, making it impossible to effectively select the adsorption separation. To realize the selective separation of heavy metals, this requires the decomplexation of complexed heavy metals. At present, decomplexation technology can be divided into ligand displacement decomplexation technology, ligand oxidation decomplexation technology and metal ion reduction decomplexation technology according to the decomplexation principle.

Ligand displacement decomplexation technology is to replace the target heavy metal ions by adding metal ions with stronger ligand complexing ability, so as to realize the decomplexation of heavy metals. The ligand oxidation decomplexation technology is to convert the ligand into a product that loses its complexing ability or completely mineralize the ligand compound by oxidizing the ligand compound, breaking the complexation and releasing the heavy metal ions. The metal ion reduction and decomplexation technology is to reduce the complexed heavy metal ions to low-valent metal ions or metal simple substances through reducing reagents, reducing the stability of the complexes, thereby realizing the destabilization and decomplexation of complexed heavy metals. These methods have a more significant effect on the treatment of complexed heavy metals. However, both ligand replacement decomplexation and ligand oxidation decomplexation have the characteristics of large reagent consumption, large waste output, and extensive technology; while metal ion reduction decomplexation technology still has the problem of low purity of recovered metals.

Therefore, seeking an intensive decomplexing coupling heavy metal selective recovery technology has become a demand for the development of contemporary society. Based on this idea, we propose an intensive decomplexation technology of Fe(III) ions and O ₂ co-promoted photocatalysis, which realizes the recycling of Fe(III) ions and the selective recovery of target heavy metals.

Contents of the invention

Aiming at the deficiencies in the prior art, the invention provides a method for photodecomplexing and enhancing the resource utilization of heavy metal complex wastewater to solve the problems in the prior art.

The invention relates to a method for photodecomplexation to strengthen the resource utilization of heavy metal complex wastewater, specifically based on Fe(III) ions and _O2 co-promoting photocatalytic decomplexation to break the interference of organic acid complexing agents on the adsorption of heavy metals, thereby strengthening chelation The selective adsorption of the target heavy metal ions by the combined adsorbent realizes the low-cost resource utilization of heavy metals under the coexistence of organic acids.

To achieve the above object, the technical scheme adopted in the present invention is as follows:

A method for photodecomplexation strengthening the resource utilization of heavy metal complex wastewater, the specific steps are as follows:

(1) Pretreatment: After filtering complex wastewater containing target heavy metals, adding iron reagents and performing aeration treatment; the added Fe(III) ions have dual functions of ligand replacement decomplexation and photocatalytic decarboxylation. The incoming oxygen acts to enhance the photochemical decarboxylation;

(2) Photocatalytic decomplexation: pump the effluent of step (1) into the photoreactor to carry out photocatalytic decomplexation;

The technical principle of the above process is shown in the following formula:

Cu(II)-EDTA+Fe(III)-→Fe(III)-EDTA+Cu(II) (1-1)

4Fe(II)+4H ⁺ +O ₂ →4Fe(III)+2H ₂ O (1-4)

(3) Heavy metal recovery: the effluent of step (2) is pumped into the I-level adsorption column filled with class A adsorbent, and the target heavy metal ion is recovered; the adsorbent with high selective separation coefficient for the target heavy metal ion is filled therein. Sexual adsorption and recovery of target heavy metal ions;

(4) Iron recovery: pump the effluent from step (3) into the II-stage adsorption column filled with B-type adsorbent, which is filled with an adsorbent with a high-efficiency selective separation coefficient for Fe(III) ions, and extract ferric ions ;

(5) Iron recycling: after the adsorption column in step (4) penetrates, pump regenerant into the II-level adsorption column for regeneration, and recover the desorption solution containing ferric ions.

As an improvement of the present invention, the heavy metal complex wastewater described in the step (1) refers to heavy metal wastewater containing an organic acid complexing agent, wherein the organic acid complexing agent refers to an organic compound containing a carboxyl group in its molecular structure. Acid, preferably EDTA of aminocarboxylic acids, citric acid of hydroxycarboxylic acids.

As an improvement of the present invention, the iron reagent in the step (1) is ferric salt solution, and the ferric salt solution is ferric chloride solution, ferric sulfate solution or ferric nitrate solution, and the ferric reagent The iron ion concentration in the medium is 0.1-1.0mol/L.

As an improvement of the present invention, the molar concentration of the iron reagent in the step (1) is 0.1-1.0 times the molar concentration of the complexing agent in the heavy metal complexing wastewater.

As an improvement of the present invention, the aeration mode in the step (1) is air aeration; the dissolved oxygen concentration in the heavy metal complex wastewater after aeration in the step (1) is 8.0mg/L at normal temperature above.

As an improvement of the present invention, the hydraulic retention time of the heavy metal complex wastewater in the photoreactor in the step (2) is 10-60min.

As an improvement of the present invention, in the step (2), the effective wavelength of the light source of the photoreactor is 200-420nm, and the light source of the photoreactor is a mercury lamp.

As an improvement of the present invention, the type A adsorbent in the step (3) is a chelating adsorbent, and the chelating adsorbent is aminocarboxylic acid resin D463, pyridine resin TP22, pyridine resin M4195, Any one of aminophosphoric acid resin Purolite S950 or amidoxime resin Purolite S910.

As an improvement of the present invention, the target heavy metal ion in the step (1) is one or more of cobalt, copper, zinc, cadmium and lead.

As an improvement of the present invention, the B-type adsorbent in the step (4) is Purolite S957, a phosphine-sulfonic acid resin.

As an improvement of the present invention, the regeneration agent in the step (5) refers to 2%-20%wt dilute sulfuric acid or 5%-20%wt dilute hydrochloric acid or 5%-20%wt dilute nitric acid.

Owing to having adopted above technique, the present invention compares with prior art, has the beneficial effect as follows:

(1) Photocatalytic decomplexation is promoted by Fe(III) ions and _O2 , which greatly shortens the hydraulic residence time of photodecomposition and effectively saves energy;

(2) Using highly selective adsorbents to recover Fe(III) ions, and then reusing the resin desorption solution as an iron-adding reagent, the recycling of photocatalytic agents is realized, which greatly reduces the dependence of decomplexation technology on the consumption of chemicals;

(3) The recovery of target heavy metal ions by highly selective adsorbents is enhanced by photocatalytic decomplexation, the purity of recovered metals is improved, the effective recovery of resources is realized, and the economic value of the technology is increased.

Description of drawings

Fig. 1 is the contrast figure of chelating adsorption resin performance before and after decomplexation;

Detailed ways

The present invention will be further explained below in combination with specific embodiments.

Embodiment: Cu-EDTA heavy metal complex wastewater

The first step, pretreatment, photocatalytic decomplexation: into 1.0L of Cu-EDTA heavy metal complex wastewater (where the concentration of Cu(II) is 1.0mmol/L, and the concentration of the typical complexing agent EDTA is 2.0mmol/L) Add iron reagent, and maintain the pH of Cu-EDTA complex wastewater between 2.0-4.0, and then expose air to Cu-EDTA heavy metal complex wastewater, so that the concentration of dissolved oxygen in the aerated wastewater can reach 8.0mg/L or more. Then pump the aerated wastewater into a photoreactor with a 300W mercury lamp as the light source and an effective wavelength of the light source of 200-420nm for photocatalytic decomplexation. Comparing the EDTA decomposition rate under several groups of decomplexation parameters in Table 1, it can be found that Fe(III) ions and O ₂ co-promoted photodecomposition technology can better realize the decomposition of EDTA.

Table 1 Decomplexation process control parameters and decomplexation effect

Second step, heavy metal recovery: the Cu-EDTA heavy metal complex wastewater after photodecomplexation (according to the decomplexation condition of sequence number 5, EDTA decomposition rate is 98.7% Cu-EDTA heavy metal complex wastewater), according to the solid-liquid ratio Add 1.0g/L to the first-stage adsorption column equipped with aminocarboxylic acid resin D463, aminophosphoric acid resin PuroliteS950, pyridine resin TP220, pyridine resin M4195 or amidoxime resin PuroliteS910, and maintain Cu -The pH of the EDTA heavy metal complex wastewater is between 5.0-7.0, put it into a constant temperature oscillator at 298K, control the rotation speed at 160rpm, fully oscillate and adsorb for 24h, and obtain the Cu-EDTA heavy metal complex wastewater after absorbing Cu(II). It can be seen from Figure 1 that the adsorption performance of chelating resins to Cu(II) before and after decomplexation under the same conditions can be found that the adsorption performance of several chelating resins to Cu(II) after decomplexation has been greatly improved.

Iron recovery: add the Cu-EDTA heavy metal complex wastewater after adsorbing Cu(II) to the second-stage adsorption column equipped with phosphinesulfonic acid-based resin Purolite S957 according to the solid-to-liquid ratio of 1.0g/L, and maintain the wastewater The pH is between 5.0-7.0, placed in a constant temperature oscillator at 298K, the rotation speed is controlled at 160rpm, the adsorption is fully oscillated for 24h, and the recovery rate of Fe(III) is detected. Comparing the recovery rate of Fe(III) ions in Table 2 below, it can be seen that Purolite S957 has a beneficial recovery effect on Fe(III) ions.

Table 2 Iron recovery effect

The third step, iron recycling: the S957 resin after adsorbing Fe(III) ions (according to the decomplexation conditions of serial number 14, the Fe(III) recovery rate is 98.0% B-type adsorbent after adsorption), using different regeneration methods agent to regenerate it. Comparing the desorption rate of Fe(III) ion in Table 3 below, it can be found that the Fe(III) adsorbed by S957 resin has a good desorption rate.

Table 3 The regeneration effect of different regeneration agents on S957

No. 19, Fe(III) desorption rate of 90.8% of the desorption solution was detected, it can be known that the composition of the desorption solution: 0.1-0.25mol/L Fe(III) ions, 0.5-1.0mol/L hydrogen ions And a small amount of EDTA decomposition products, 300-1000mg(TOC)/L. Add Cu-EDTA heavy metal complex wastewater as an iron reagent, and maintain the pH of the wastewater between 1.5-3.5. Comparing the decomposition rate of EDTA in Table 4, it can be found that the desorption solution can also be used as an iron reagent. decomposition.

The decomplexation effect of table 4 desorption solution as iron reagent

The above-described embodiments are only preferred technical solutions of the present invention, and should not be regarded as limitations on the present invention. The protection scope of the present invention should be based on the technical solutions described in the claims, including the equivalent replacement of technical features in the technical solutions described in the claims. The solution is within the scope of protection, that is, equivalent replacement and improvement within this scope are also within the protection scope of the present invention.

Claims (10)

1. A kind of method that photolysis complex strengthens heavy metal complexation waste water recycling, it is characterized in that, concrete steps are as follows: (1) Pretreatment: After filtering complex wastewater containing target heavy metals, add iron reagent and perform aeration treatment; (2) Photocatalytic decomplexation: pump the effluent of step (1) into the photoreactor to carry out photocatalytic decomplexation; (3) Heavy metal recovery: pump the effluent from step (2) into the first-stage adsorption column filled with type A adsorbent to recover the target heavy metal ions; (4) Iron recovery: pump the effluent of step (3) into the II-level adsorption column filled with B-type adsorbent to extract ferric ions; (5) Iron recycling: After the adsorption column in step (4) penetrates, pump regenerant into the II-stage adsorption column for regeneration, and recover the desorption solution containing ferric ions. 2. a kind of method according to claim 1 that photodecomposition strengthens heavy metal complexation waste water recycling, it is characterized in that: the iron reagent in described step (1) is ferric salt solution, and described ferric The salt solution is ferric chloride solution, ferric sulfate solution or ferric nitrate solution, and the iron ion concentration in the iron reagent is 0.1-1.0 mol/L. 3. a kind of photolysis complex according to claim 1 strengthens the method for heavy metal complex waste water recycling, it is characterized in that: the molar concentration of iron reagent in the described step (1) is complexing agent molar concentration in the heavy metal complex waste water 0.1-1.0 times. 4. a kind of method according to claim 1 that photodecomposition strengthens heavy metal complexation waste water recycling is characterized in that: in described step (1), aeration mode is air aeration; In described step (1), After aeration, the dissolved oxygen concentration in the heavy metal complex wastewater is above 8.0 mg/L at room temperature. 5. A kind of method according to claim 1 that photodecomposition strengthens the resource utilization of heavy metal complex wastewater, characterized in that: in the step (2), the hydraulic retention time of heavy metal complex wastewater in the photoreactor is 10 -60min. 6 . A method for photodecomplexing enhanced heavy metal complexation waste water recycling according to claim 1 , characterized in that: in the step (2), the effective wavelength of the light source of the photoreactor is 200-420nm. 7. A kind of photodecomposition strengthening method for resource recovery of heavy metal complex wastewater according to claim 1, characterized in that: the class A adsorbent in the step (3) is a chelating adsorbent, and the chelating The adsorbent is any one of aminocarboxylic acid resin D463, pyridine resin TP22, pyridine resin M4195, aminophosphoric acid resin Purolite S950 or amidoxime resin Purolite S910. 8. A kind of method according to claim 1 that photodecomposition strengthens heavy metal complexation waste water recycling, it is characterized in that: in the described step (1), the target heavy metal ion is cobalt, copper, zinc, cadmium and lead one or more. 9 . A method for photodecomposition-strengthening heavy metal complexation wastewater recycling according to claim 1 , characterized in that: the B-type adsorbent in the step (4) is phosphine-sulfonic acid resin Purolite S957. 10. A kind of method according to claim 1, wherein the method for strengthening the recycling of heavy metal complex wastewater by photolysis, is characterized in that: the regeneration agent in the step (5) refers to 2%-20%wt dilute sulfuric acid or 5%-20%wt dilute hydrochloric acid or 5%-20%wt dilute nitric acid.