Study On The Treatment Of Heavy Metal Wastewater Containing Salt By CDI-EDI Combined Process

In recent years,with the improvement of people's risk awareness,zero-emission of salt heavy metal wastewater has received attention.However,due to the adsorption competition and solubilization effect of salt ions,the difficulty of removing heavy metal ions is obviously improved.The capacitive deionization process was studied combine with electrodeionization method in this paper.The copper-containing simulated wastewater and nickel-containing electroplating wastewaters were investigated by self-made CDI-EDI reaction device.The deion mechanism and efficiency of the reaction device were inspected.The effect of the cation exchange and electromigration at the anode chamber and the electro-adsorption at the cathode chamber to removal heavy metal ions were explored respectively.The 2.0 cm×2.0 cm electrodes were selected through the orthogonal experiment of the three-electrode system.The Ti/CAC capacitance electrode was filtrated with big specific surface area,high specific capacitance,stable performance and easy preparation.The best scan speed was 5.0 mV/s,and the scan voltage was-0.30~0.30 V in the cyclic voltammetry experiment.The charge and discharge specific capacity of the Ti/CAC capacitance electrode was respectively about 138.7 F/g and 139.5 F/g when the electrolyte was 1.0 mol/L Na2SO4 solution,the continuous current was 50 mA and the voltage limit was 0.20 V.The deionization effect at the anode chamber,cathode chamber and concentrated chamber were studied respectively using the self-made CDI-EDI reaction device to dispose salt heavy metal wastewater with 5.0 cm×10.0 cm Ti/CAC capacitance electrodes as the reaction electrodes.The cation exchange resin was the main role of removal heavy metal ions at the anode chamber.The cation exchange effect could remove 63.3% Cu2+ when the cathode chamber and anode chamber were filled with 5.0 mL of the anion resin and cationic resin respectively,and 50.0 mg/L Cu2+ solution was treated without electricity.The cationic resin and anion resin were regenerated well with 9.0 mA current,and the removal efficiency of Cu2+ were stable after the regeneration.For the electromigration process,when the influent concentration of Cu2+ solution was 235 mg/L at the anode chamber and the concentration of Na2SO4 solution was 0.20 mol/L at the concentrate chamber,the current of 4.0 mA could be used to avoid electrolysis water reaction for a better removal of Cu2+at the anode chamber with stable effluent.In addition,the adsorption efficiency of the cathode to heavy metal ions was improved by increasing the adsorption time or the number of adsorption tandem devices.The better removal rate of Cu2+ in simulated wastewater was obtained by using CDI-EDI device combined the effects of cation exchange with electromigration at the anode chamber and the effect of electroadsorption at the cathode chamber.The removal rates of Cu2+ in the effluent from the anode and cathode chambers arrived at 96.40% and 87.40%,respectively,when those chambers were filled with 12.0 mL of resin to treat Cu2+ solution 50.0 mg/L with 2.0 mA current after 22.5 min.For the electroplating wastewater containing Ni2+ 389.4 mg/L,after enhanced precipitation and microfiltration treatment,the average concentration of Ni2+ at the anode chamber and cathode chamber were reduced to 1.61 mg/L and 2.01 mg/L by CDI-EDI combination process,respectively.The CDI-EDI device was operatedefficiently with low energy consumption.The resin could be regenerated online,and the recycled liquid and concentrated liquid could be recycled to achieve the purpose of enrichment of heavy metals and salts.The whole operation process had no secondary pollution,which provided new technical and data support for the treatment of heavy metal industrial wastewater.