Study On The Treatment Of Arsenic-containing Waste Acid By Copper Flotation Tailings

Waste acid is a main arsenic pollution source in nonferrous smelting industry,which has the characteristics of high arsenic content,strong acid and complex composition.At present,sulfurization method and lime-ferric salt method are commonly used for removal of arsenic from waste acid.There are many problems such as high cost of reagents,hydrogen sulfide generation,neutralizing gypsum slag generation,arsenic-containing slag instability.Therefore,how to achieve green,economic and efficient removal of arsenic from waste acid has become one of the important problems in nonferrous smelting industry.Copper flotation tailings is a solid waste produced in the copper smelting process,which is rich in iron oxides.Due to the lack of waste utilization methods at present,copper flotation tailings are mostly stored in the slag yard,resulting in environmental risks.In this study,take"treating waste with waste"as the starting point,based on arsenic removal technology with ferrous salt,a method using copper flotation tailings as solid iron source for arsenic removal from waste acid was proposed.XRD and XRF analysis showed that there was abundant iron oxide in the copper flotation tailings.The elemental content in the used waste acid was determined by ICP-OES and the acidity by acid-base titration.The initial arsenic concentration was 7260mg/L,and the acidity was 31238 mg/L based on sulfuric acid in the waste acid.Copper flotation tailings can be used as solid iron source to remove arsenic from waste acid under strong acidic conditions.In order to get the optimal arsenic removal efficiency,the arsenic removal efficiency of waste acid under different reaction conditions and the leaching toxicity concentration of arsenic in arsenic-bearing copper flotation tailings after arsenic removal were studied.Results show that the copper flotation tailings/waste acid solid-liquid ratio of 1:5 g/m L,initial p H of 1.5,reaction temperature is 90℃,reaction time is 8 h,30%hydrogen peroxide dosage of 1.7 m L,copper flotation tailings are not filtered after leaching from waste acid the optimum reaction conditions,arsenic removal efficiency of waste acid reached 99.94%,after eliminating arsenic leaching toxicity of arsenic in copper flotation tailings concentration is 2.6336 mg/L.Then raw copper flotation tailings were used to further purified the residual arsenic in the waste acid.After the secondary arsenic removal,the residual arsenic concentration in the waste acid was as low as 0.0279 mg/L.The adsorption kinetics of copper flotation tailings for arsenic removal from waste acid was studied.The results show that the adsorption kinetics of copper flotation tailings for arsenic removal conforms to the second-order adsorption kinetics.The copper flotation tailings containing arsenic after reaction were characterized by XRD,SEM-EDS,XPS,FTIR and PSD under the optimum reaction conditions.The results show that the copper flotation tailings can remove arsenic from the waste acid by adsorption and Fe-As co-precipitation,and the resulting Fe-As precipitates are FeAsO₄·2H₂O and iron arsenate.