Process for treating cyanide-containing wastewater by ion exchange

Ion exchange process is a process wastewater containing cyanide, cyanide wastewater domestic and industrial gold <br> state of the art typically produced depending on the concentration level of different processing method. When the concentration is high (CN-≮700mg/l), the acidification recovery method with higher investment is generally used as the first treatment method, and the secondary treatment method is performed by the sulfur dioxide-air method or the natural purification method. Since the useful substances in the wastewater are recovered, It has good economic benefits; when the concentration is low (CN-≯200mg/l), it is generally treated with a small investment of chlorine oxidation or sulfur dioxide-air method, and the treated wastewater can be discharged. The treatment cost can also be mined. Accepted by the party. When the wastewater concentration is medium (700mg/l ≥CN-≥200mg/l), the above methods are not ideal, the former has no profit, and the latter has high cost. The mine is difficult to accept.
The treatment method that can recover cyanide and recycle the waste water can recover the useful materials from the waste water and avoid the problem of environmental protection requirements when the waste water is discharged. Such methods include electrodialysis, reverse osmosis, ultrafiltration, extraction, two-step precipitation, and ion exchange. The concentration of impurities such as thiocyanate and arsenate contained in the cyanide-containing wastewater produced by the gold industry. Higher, it has no harmful effect on various ion exchange membranes, because the first three methods can not be industrially applied; the fourth and fifth methods can achieve the purpose of removing impurities, but the anion introduced into the wastewater is too much and sulfuric acid Calcium is often in a state of supersaturation, which tends to crystallize in the pipeline, and blocks the pipeline in severe cases; only the ion exchange method is suitable.
According to reports, a resin produced in France called V912 is more suitable, especially the desorption and regeneration method of the resin is relatively simple, and there is no similar resin in China. Through the experimental research on various domestic anion exchange resins, the desorption regeneration method of domestic resin and the new process of treating cyanide-containing wastewater by ion exchange method were determined. This desorption method and process are suitable for various kinds of cyanide wastewater treatment in gold industry. Desorption and regeneration of anion exchange resin.
Second, the ion exchange method for the treatment of cyanide-containing wastewater principle and process The basic principle of the ion exchange method is that the anion with strong adsorption capacity in the wastewater, when passing through the ion exchange resin, ion exchange with the exchangeable anion on the resin, and finally The impurities in the wastewater are adsorbed on the resin and the anions on the resin are replaced into the treated wastewater. As a result, impurities affecting gold leaching in the wastewater are greatly reduced, and the wastewater is recycled; the resin adsorbed with impurities is desorbed after being saturated to be regenerated, reused, and the desorbed impurities are recovered. Compared with the acidification recovery method, the useful materials in the wastewater are also recovered; at the same time, the wastewater is recycled, and it is not necessary to be treated in depth, so the economic benefit is better than the acidification recovery method, and the investment is small, so it is suitable for treating medium-concentration cyanide-containing wastewater. . The schematic diagram of the process flow for treating wastewater is as follows:
Cyanide-containing wastewater-→Ion exchange resin→ Return to cyanide leaching section absorbent ↓
Sulfuric acid-→acidification desorption---→ copper desorption ← ammonia desorption liquid ↓ ↓
Caustic soda-→cyanide recovery of copper-containing desorbent ↓ ↓
Sodium cyanide heavy precious metal recovery ← extractant ↓
The heavy metal is sold with an ion exchange resin which adsorbs impurities, first desorbed with sulfuric acid, and the cyanide ions adsorbed on the resin are converted into HCN molecules which are not adsorbed by the resin, and the HCN molecules are dissociated from the resin and carried into the desorbed liquid. The HCN-containing desorbed solution can be recovered by acidification recovery to recover HCN, to obtain a concentrated solution of sodium cyanide, and the solution is sent to a cyanidation leaching section. The sulfuric acid desorbing solution desorbs most of the zinc on the resin while desorbing cyanide. The desorbed solution is re-used or discharged by neutralization precipitation after desorption.
After washing the resin after desorption of cyanide, the copper on the resin is hydrolyzed with ammonia, and the copper-containing ammonia solution is separated by copper by extraction, vaporization or sulfide precipitation, and sold as copper sulfate or insoluble sulfide. The ammonia water after decoppering is reused.
The resin after desorption of copper is washed with water and reused.
1. Adsorption process conditions adsorption speed 2-15M3/ht resin (determined by impurity concentration)
Adsorption method fixed bed continuous or fluid bed batch or multi-tank series stirring (depending on the material to be treated is clear liquid or slurry)
No adsorption temperature requirement 2, elution cyanide process conditions, elution mode, continuous stirring, elution, sulfuric acid solution, acidity, pH 1.5~2.5
Elution temperature Normal temperature absorption solution caustic soda concentration 5%-10%
3, elution copper process conditions eluent ammonia concentration 5% ~ 20% (when there is no ammonia, ammonium chloride and sodium hydroxide mixture can be used to elute copper, ammonium chloride concentration 20 ~ 200g / l,
The concentration of sodium hydroxide is 20 to 50 g/l).
Elution-copper mode single-tank intermittent stirring elution or multi-tank continuous stirring elution elution time single tank 1 hour or 1 hour per tank (depending on the nature of the resin used)
The number of elution times during intermittent elution is 2 to 4 times (depending on the copper concentration on the resin)
4, adsorption index copper ≮ 85%
Zinc oxide 90%
5, desorption (elution) indicator copper ≮ 75%
Zinc oxide 80%
III. Equipment investment (100M3/d processing capacity) Estimated serial number Equipment name Specification Quantity Unit price Amount of remittance 10,000 yuan/unit 10,000 1 Adsorption tower Φ1500×3000 1 3 3 Anti-corrosion 2 Cyanide elution tank Φ1500×2500 1 3 3 2.2 KW anti-corrosion 3 hydrogen cyanide blowing tower Φ1000×4000 1 4 4 1.5KW anti-corrosion 4 hydrogen cyanide absorption equipment 1 set 4 4 1.5KW anti-corrosion 5 copper elution tank Φ1500×2500 1 3 3 1.5KW anti-corrosion 6 copper liquid copper removal Equipment 1 set 5 5 1.5KW Anti-corrosion 7 Resin lifting equipment (intermittent) 3 1 3 1.5×3KW Anti-corrosion 8 3M3 resin storage tank 2 1 2 Anti-corrosion 9 Cyanide elution waste treatment tank 1 2 2 0.75KW Anti-corrosion 10 Copper wash Deli preparation tank 1 3 3 1.5KW Anti-corrosion 11 Waste water pump 1 1 1 Anti-corrosion pump 12 Various solution tanks 4 0.5 2 Anti-corrosion 13 Sulfuric acid storage tank 4M3 1 2 2 Anti-corrosion 14 Sulfuric acid pump 1 2 2 Anti-corrosion 15 Other equipment (including ventilation) 6
16 Power Distribution 2
17 piping (anti-corrosion pipe) 2
18 Foundation 5
19 total 54
Fourth, the processing cost estimate (to deal with 100M3 wastewater meter)
No. Material Name Quantity Unit Price Remarks 1 Sulfuric acid 200Kg 0.40 yuan / kg 80 yuan 2 Ammonia water 100kg 0.80 80 yuan 3 Copper removal agent 50kg 3.00 150
4 Acidic Residue Treatment Agent 40
5 power 200KWh 0.60 120
6 Resin consumption 2kg 40.00 80
7 water 5M3 4.00 20
8 Labor 7 25 175
9 Other costs 50
10 Total 795
The average processing cost is 7.95 yuan / M3.
V. Estimation of economic benefits Wastewater composition and addition benefit Wastewater composition 1 Wastewater composition 2
Wastewater composition CN- Cu Au CN- Cu Au
Concentration of constituents (mg/l) 350 200 0.03 600 500 0.03
Recovery rate (%) 95 80 80 95 80 80
Recovery amount (kg/M3) 0.6 0.16 0.024 1.0 0.4 0.024
Unit price (yuan/kg) 9.00 10 70 9 10 70
Amount (yuan / M3) 5.40 1.60 1.92 9 4 1.68
Total amount (yuan / M3) 8.92 14.68
Unit profit (yuan / M3) 0.97 6.73
VI. Conclusion At present, domestic gold mines use chlorine oxidation to treat cyanide-containing wastewater at a cost of about 8-15 yuan/M3. If the extraction method is used, there is no economic benefit due to the low concentration of useful substances. Ion exchange treatment of wastewater is economical and there is a certain profit every year.
It can be seen from the above calculation that the treatment of medium-concentration cyanide-containing wastewater by ion exchange is an ideal treatment method, and the equipment investment can be recovered in more than one year. The raw materials used are all based in China and have good prospects for promotion.
Characteristics of the method and process 1. Ion exchange treatment of cyanide-containing wastewater can not only recycle wastewater but also recycle impurities in wastewater, which is not economically feasible by other methods currently applied in industry. .
2. Due to the strong adaptability of the desorption method, a strong basic anion exchange resin or a weakly basic anion exchange resin may be selected according to the concentration of impurities in the wastewater and the presence or absence of impurities in the wastewater (resisting of resin poisoning). The selection range is large. The selection of a suitable resin according to the nature of the wastewater can achieve the purpose of reducing the processing cost.
3. The use of sulfuric acid as a desorbent for cyanide and zinc has a good effect and low cost. The desorption of copper is made easy, and the copper on the resin can be desorbed with an ammonia solution.
4. The use of ammonia solution to desorb copper has the characteristics of low cost, good desorption effect and low cost. The copper-containing desorbent can be used to produce copper sulfate by extraction, and the copper residue can be obtained by sulfide precipitation method. The copper salt can also be separated by evaporation. No matter which method is used, the ammonia-containing desorbent can be reused, and the desorption cost is reduced.
5. A small amount of cyanide desorption waste liquid (about 2% of the treated wastewater) can be used to precipitate impurities such as zinc oxide in the alkaline wastewater, and then used to dilute the sulfuric acid and resin washing process, so that the ion exchange method has no secondary pollution.

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