Wastewater treatment with flotation reagent

At present, China vein of gold ore and gold sulfide mostly using the flotation process sorting, in the flotation process, adding a large number of flotation reagents. These agents are mainly butyl xanthate, turpentine, individual gold plant using ADDP, and using kerosene as collector. The flotation agent remaining in the dewatering of the flotation tailings and the thickener is discharged to the nearby surface water without treatment, and generally does not meet the discharge standard, causing pollution to the environment. The environmental monitoring results of the following three gold mines indicate that they exceed the national environmental standard limit allowable concentration (0.005 mg/L for butyl xanthate and 0.2 mg/L for turpentine). The monitoring results of flotation agent content are shown in Table 1.

Table 1 Results of flotation agent content monitoring

There are several methods for treating wastewater from flotation reagents.

1. Chemical treatment of wastewater containing flotation reagents

There are five methods for chemical treatment of wastewater containing flotation reagents.

(a) oxidative decomposition: the oxidant used

Liquid chlorine, bleaching powder, sodium hypochlorite, etc. are oxidatively decomposed. Its role is: "active chlorine" destroys the xanthate in the wastewater, so that it is oxidized to non-toxic sulfate, the pH is preferably 7 ~ 8.5 during treatment. The treatment effect is good or bad, mainly depending on the proper use of the reagents. The dosage is too small, the treatment is incomplete; the dosage is too much, and there is “active chlorine” in the purification liquid.

(2) Ozonation

The treatment of xanthate is better and there is no "active chlorine". However, the power consumption is large and has not been widely used in production so far.

(3) Electrolysis

Platinum was used as the electrode, and the DC voltage was 0.5 V, and the current was 40 mA for electrolysis (decomposed xanthate).

(4) Replacement recovery method

In the wastewater containing xanthate and having a precipitate of hydroxide formed by heavy metals, sodium sulfide is added under controlled pH conditions, and the xanthate can be replaced and recycled.

(5) Acidification or alkalization

Adding sulfuric acid (100-200mg/L) to the wastewater from the tailings pond can destroy the yellow medicine in the ore dressing wastewater, so that the effluent water quality meets the national discharge requirements “Class III Water Surface Emission Standard”. Lime may also be added to the tailings pond, and the flotation agent is adsorbed along with the precipitation of the metal hydroxide into the sludge at the bottom of the reservoir.

Second, physical treatment of wastewater containing flotation reagents

(1) Aeration method

The wastewater containing flotation reagents is stored in the tailings pond for a period of time, and after aeration treatment, the flotation agent content can be greatly reduced.

(2) Ultraviolet irradiation method

The use of ultraviolet radiation of 250 to 550 nm can destroy the requirements of the flotation agent in the wastewater to achieve purification.

3. Physical and chemical treatment of wastewater containing flotation reagents

(1) Adsorption method

The adsorbent is made of activated carbon, slag, kaolin, and the like. For example, when kaolin 20g/L, the butyl yellow drug removal rate is 89%, and the turpentine removal rate is 80%.

(2) Cohesion method

The coagulant is added to the wastewater containing the flotation reagent, and the metal in the wastewater and the flotation reagent can be agglomerated and precipitated.

(3) Ion exchange method

The yellow drug-containing wastewater is precipitated, filtered, neutralized, and passed through an AB-17 resin or a cationic resin to remove the xanthate from the wastewater.

At present, pollution pollution in gold production is dominated by cyanide treatment. The sulphide-type gold mines are mostly selected by flotation reagents. The flotation tailings and decontamination wastewater are generally sent to the tailings pond through pipelines without treatment. In the tailings pond, the ground is discharged for a period of time, so that the turpentine can reach the standard in the surface water body, and the yellow medicine does not meet the water quality standard. However, there have been no incidents of poisoning of humans, animals and crops caused by xanthate in gold mines. The reason is that turpentine is easily decomposed and volatile during the tailings inventory, and the xanthate is prone to decomposition reaction in water. A variety of factors are relevant. In the tailings pond, the wastewater contains xanthate below 5mg/L. If the yellow drug is completely decomposed, the CS ₂ is only about 2mg/L (the maximum allowable concentration of CS _{2 in} ground water is 2mg/L). According to the data, the odor and toxicity of xanthate are mainly caused by CS ₂ , so the content of CS ₂ in water is generally not up to the toxic dose.