Treatment Of Acid Wastewater And Slag Produced In Copper Smelting Process Using Bipolar Membrane Electrodialysis

Copper has excellent characteristics of ductility,thermal conductivity and chemical stability,which is widely used in electrical,construction,national defense,machinery manufacturing and other industries.At present,the main method of extracting copper from copper ore in China is hydrometallurgy,which produces a lot of acid waste liquid and waste residue.Acidic waste liquid has the characteristics of complex heavy metal species,high acid and sulfate concentration.Discharge of them into the environment will lead to water and soil pollution,affect the growth of animals and plants.Heavy metals can be enriched and accumulated through the food chain and food web,thus threatening the health and safety of human beings.The composition of waste residue is complex and rich in a large number of heavy metals and toxic and harmful substances.Under the action of natural weathering and erosion,it is easy to form dust and cause air pollution.Under the action of rain,it pollutes the surrounding water and soil through surface runoff and underground seepage,and poses a potential threat to the environment and human health.The acid waste liquid and waste residue contain a lot of valuable heavy metals,and its discharge will cause environmental pollution and waste of resources at the same time.Therefore,it is of great economic,environmental and human health significance to explore a method that can treat acid waste liquid waste residue and recycle its resources.Electrodialysis(ED)is a method to separate cation and cation from solution under the action of applied electric field by the selective light transmittance of ion exchange membrane.Because of its characteristics of low environmental pollution,simple operation and green environmental protection,it has been widely paid attention to by researchers.However,due to its disadvantages of low current efficiency and high energy consumption,it is only widely used in seawater desalination and high-salt wastewater treatment.Bipolar membrane electrodialysis(BMED)is a new environmental protection process system composed of bipolar membrane,which can convert the salt in wastewater into the corresponding acid and alkali,and has been widely used in the field of saline wastewater treatment.In this paper,the BMED system is used to treat the acidic waste liquid and waste residue produced in the hydrometallurgical process of copper ore.The research is as follows:(1)Apply the BMED system to treat the acidic waste liquid produced in the hydrometallurgical process of copper oreFirstly study the effect of electrolyte concentration on the device voltage,current density,and heavy metal waste water chamber room more volume than(V_WAC:V_HMC),unit processes for removal of heavy metals,the conductivity and the influence of p H,device voltage and energy consumption,and analyzes the distribution of heavy metals in the whole process-H₂SO₄after processing and recycling.The results showed that the migration rate and current efficiency of heavy metal ions increased with the increase of current density,but the unit energy consumption of waste liquid treatment increased with the increase of current density.The increase of HMC volume in V_WAC:V_HMCis beneficial to the migration of heavy metal ions;Adding multiple treatment units of BMED system in series can increase the amount of waste liquid treatment per unit time,improve the current efficiency of the system and reduce the energy consumption per unit of heavy metal removal.After 40 h,the recovery rate of SO₄^2-ion in the waste solution is 85.9%(the molar concentration of H₂SO₄is about 0.395 mol/L).The concentration of heavy metal ion in the treated acidic waste solution is less than 100 mg/L and the p H value is0.96,which can be used as the acid leaching solution of copper ore.No chemical reagents were added in the whole treatment process,and the treated acidic waste liquid could be reused,thus achieving the purpose of zero discharge of waste liquid.Under the selected experimental conditions,the optimal conditions for BMED system to treat the acidic waste liquid produced in the hydrometallurgical process of copper ore are as follows:electrolyte Na₂SO₄concentration 1.0 mol/L,current density 3.0 m A/cm²and V_WAC:V_HMC=1:15.(2)The BMED system is applied to treat the waste residue produced in the hydrometallurgical process of copper oreThe BMED system is used to first leash the heavy metals in the waste residue,and then the waste residue liquid-solid liquid separation,and finally the supernatant after separation is treated with the BMED system.Firstly,the influence of liquid-solid ratio of waste residue on the voltage of the equipment was studied,and the influence of current density and particle size of waste residue on the leaching of heavy metals from BMED system was investigated,and the heavy metal speciation before and after the desorption and treatment and the distribution of heavy metals after treatment were analyzed.Then the treated waste residue is separated from liquid solid liquid.Finally,the effects of current density,volume ratio of supernatant chamber to heavy metal chamber(V_SFC:V_HMC),multi-unit treatment on heavy metal removal,conductivity and p H of each chamber,device voltage and energy consumption were investigated,and the removal of heavy metals from the waste residue during the whole treatment process was analyzed.The results show that when the liquid-solid ratio of waste residue is 1:1.5,the electroosmotic effect can be slowed down and the voltage of the device can be reduced.Acidic conditions are favorable for the desorption of heavy metals from the waste residue.The desorption process of heavy metals such as Fe,Mg and Ni conforms to the Elovich kinetic equation,while the desorption process of Cd and Cu conforms to the first-order kinetic equation.Under the selected experimental conditions,the optimal leaching conditions of heavy metals in the BMED system are as follows:the concentration of electrolyte Na₂SO₄is 1.0 mol/L,the liquid-solid ratio of the waste residue is 1:1.5,the current density is 3.5 m A/cm²and the particle size of the waste residue is 100 mesh.In the process of treatment,the heavy metals in the waste residue will be converted into exchangeable state Exc,such as Carb,Femnox,OM and Res.Under the selected experimental conditions,the optimal conditions for BMED system to treat the supernatant left over from solid liquid separation of waste residue were as follows:electrolyte Na₂SO₄concentration 1.0 mol/L,current density 3.0 m A/cm²and V_SFC:V_HMC=1:10.After the disposal of the waste residue by the whole unit,most of the heavy metals in the waste residue form hydroxide precipitates dominated by Ca and Fe,and a small amount remains in the waste residue in the form of Res.Moreover,the concentration of Cu in the treated supernatant is 0.84 mg/L and the p H value is 0.77,which can be used as the acid leaching solution of copper ore.No chemical reagents were added in the whole process,and the content of heavy metals in the waste residue after treatment was low and the form was stable,which achieved the purpose of harmless waste residue.