Research On The Application Of Self-driving MFC-MEC Coupling System To Treat Electroplating Wastewater

Electroplating wastewater usually contains a variety of heavy metals and complexing agents.If discharged directly without treatment,it will pose a threat to human production and life,and on the other hand,it will cause waste of valuable metal resources in electroplating wastewater.Conventional treatment methods for electroplating wastewater include electrolysis,chemical precipitation,solvent extraction,adsorption,etc,which have problems such as high energy consumption,high cost,easy secondary pollution,and difficulty in recycling valuable metal resources.The self-driven MFC-MEC coupling system consists of microbial fuel cell?MFC?and microbial electrolysis cell?MEC?,which is an innovation in the form of a bioelectrochemical system.The MFC processes the heavy metal ions of the high oxidation-reduction potential and generates electric energy to drive the MEC to treat the heavy metal ions of the low oxidation-reduction potential,thereby realizing the reduction and removal of various heavy metal ions.The MFC reactor was constructed to investigate the effects of anode parameters?substrate concentration,sludge inoculum,anode pH?,cathode parameters?cathode pH,ion concentration,cathode material?,reactor volume,pole distance on the electrical properties of MFC and the treatment of copper-containing wastewater.The results showed that MFC had better electricity production performance and copper recovery effect when the concentration of sodium acetate in the substrate was 1 g/L,the volume ratio of activated sludge to substrate was 1:2,the anode pH was 8,the cathode pH was 3,the copper ion concentration was 500 mg/L,the cathode material was carbon paper and the reactor volume was 500 mL.The maximum power density was 6002.5 mW/m² when the pole distance was6 cm,the Cu²⁺removal rate was 99.17%,and the Cu specific yield was 0.9 mol Cu/mol COD,the MFC cathode reduction product was analyzed by XRD,and it was found that the MFC cathode products were mainly copper and cuprous oxide.The experiment also investigated the effects of electrode materials,substrate concentration,catholyte pH,reactor volume,pole pitch and other parameters on the treatment of chromium-containing wastewater by MFC and its electrical properties.The results showed that MFC had better electricity production performance and the chromium treatment effect when the carbon felt was the anode material,the carbon paper was the cathode material,the sodium acetate substrate concentration was 1 g/L,the cathode pH was2,the reactor volume was 250 mL and the pole distance was 8 cm.When the pH of the catholyte was 2,the maximum open circuit voltage of MFC was 1.122V,the maximum power density was 2945 mW/m²,the COD removal rate was 82.22%,and the removal rate of Cr⁶⁺was 96.69%.The MFC cathode product was analyzed by XRD,and Cr³⁺was produced,which proved that MFC could treat chromium-containing wastewater and reduce the toxicity of chromium in wastewater.The MFC-MEC coupling system was constructed to process the simulated electroplating wastewater.The electrical properties and heavy metal treatment effects of the coupled system were investigated by changing the MFC parameters,MEC parameters and coupling modes.1)The coupling system performance was better when the MFC reactor was 500 mL,The specific yield of Cr was 1.6 mol Cr/mol COD,the specific yield of Cd was 0.51 mol Cd/mol COD,the system electron recovery was 55.56%;2)the effect of coupling system on the treatment of chromium-nickel wastewater when the MFC sludge inoculum was 170 mL Preferably,the removal rate of Cr⁶⁺was 93.93%,and the removal rate of Ni²⁺was 83.93%;3)the MFC series stack could increase the voltage across the MEC,but on the other hand,the MFC series connection caused the electron transfer resistance to become larger,making the electrode reaction slower.In turn,the electrical properties were affected.4)When the titanium plate was used as the MEC cathode,the coupling system had better performance.The Cu²⁺removal rate was up to 93.7%,the Cd²⁺removal rate was 51.5%,the Ni²⁺removal rate was 76.28%,and the Zn²⁺removal rate was42.84%.5)The acidic cathode environment was beneficial to the reduction of metal ions in the MEC catholyte.When the pH value of the MEC catholyte was 3,the metal ion removal effect in the coupled system was better,the Cd²⁺removal rate was 82.44%,the Ni²⁺removal rate was 81.59%,and the Zn²⁺removal rate was 47.78%;6)The smaller reactor volume was beneficial to the removal of metal ions.When the MEC reactor volume was 100mL,the wastewater treatment effect was better;7)The parallel coupling mode was more conducive to the reduction and removal of Cu²⁺in MFC,the removal rate of Cu²⁺was above 80%.The experiment used MFC-MEC coupling system to treat the actual electroplating wastewater.When the high concentration copper and nickel wastewater was treated,the specific yield of Cu was 2.17 mol Cu/mol COD,and the specific yield of Ni was 1.54 mol Ni/mol COD.The electron recovery rate was 58.78%,the cathode reduction product of MEC was elemental nickel by XRD;the increase of MFC stack could improve the ability of coupling system to treat electroplating wastewater,the removal rate of Cu²⁺was above99.98%,the removal rate of Ni²⁺was 29.4%;using coupling system to deal with mixing For electroplating wastewater,when the volume of MFC reactor was 500mL,the removal rate of Cu²⁺was 64.63%,the removal rate of Cr⁶⁺was 88.28%,and the removal rates of Cd²⁺,Ni²⁺and Zn²⁺in MEC in series were 62.8%,30.7%and 40.75%,respectively.XRD was used to analyze the cathode product,MFC had CrCu formation,and MEC cathode had ZnS and Cd elemental formation.This showed that the actual electroplating wastewater could be treated by the MFC-MEC coupling system,the metal ion toxicity in the electroplating wastewater could be reduced,and the valuable metals in the electroplating wastewater could be recovered.