Study On Treatment Of Hexavalent Chromium Wastewater With Polypyrrole Modified Iron Electrode

In recent years,countries around the world have paid more and more attention to the governance wastewater,especially in Cr(Ⅵ)wastewater.Cr(Ⅵ)toxicity is stronger than Cr(III),which will not only cause serious damage to the ecological environment but affect human health.The most common domestic treatment of wastewater is chemical technology,but chemical technology does not only invest chemical agents,but also cannot effectively treat Cr(Ⅵ)wastewater.Therefore,it is practical to select a simple,efficient DC electrocoagulation technology to treat Cr(Ⅵ)in wastewater.Firstly,the electrode plate in the process of DC electrocoagulation technology of Cr(Ⅵ)in wastewater is selected.After the single factor condition change experiment,the response surface optimization experiment of its factors is carried out with Design expert 8.0.6.1 software to explore the influence of various factors on the electrocoagulation experiment,optimize the best treatment parameters,and analyze the characterization mechanism of the flocs obtained from the experiment.In view of the problems of slow reaction rate and excessive loss of iron anode plate in the experimental process of DC electrocoagulation technology of 50 mg/L Cr(Ⅵ)in wastewater,polypyrrole(PPy)with anti-corrosion and electrical conductivity was selected as the modified coating and sodium p-toluenesulfonate as the dopant.PPy modified iron electrode plate was prepared by electrochemical synthesis method,and its effect of removing Cr(Ⅵ)in wastewater,corrosion inhibition efficiency.It is found that the service life of the PPy modified iron anode plate is longer than that of the unmodified iron anode plate.The specific conclusions of this study are as follows:(1)DC electrocoagulation technology deal with Cr(Ⅵ)wastewater experiment select Fe/Fe as the electrode plate,not only high efficiency but low energy consumption.The final optimization results were pH of 6.9 after the response surface optimization experiment,and the electrolysis concentration was 107.2 mmol/L,the Cr(Ⅵ)removal rate was up to 96.5%.The experiment was carried out based on the prediction experimental conditions,and the Cr(Ⅵ)removal rate was 96.3%,and the predicted result was not large,proved that the fitted secondary polynomial model was effective in predicting the reaction process and results of Cr(Ⅵ)in DC electrocoagulation technology removal.(2)In the experiment of iron plate as an anode in DC electrocoagulation technology deal with Cr(Ⅵ)wastewater,by measuring the relationship of the total Cr(Ⅵ),Cr(Ⅵ)and Fe(Ⅱ)and analyzing the characterization results of SEM,EDS,XRD and FTIR,we can see that,the oxidation reaction of iron anode plate produces excessive Fe(Ⅱ).part of Fe(Ⅱ)reduces Cr(Ⅵ)to Cr(Ⅲ),and the other part of Fe(Ⅱ)generates polymer through hydrolysis reaction to adsorb Cr(OH)3.Therefore,the consumption of iron anode is too fast,and the electrode plate needs to be replaced constantly.(3)PPy modified iron plate was prepared by electrochemical synthesis method with sodium p-toluenesulfonate as dopant.The results of EDS and XRD showed that polypyrrole/dopant formed a dense PPy coating on the iron plate by electrochemical method.Through open circuit potential,AC impedance and Tafel experiment,it is found that the potential,Rct and corrosion potential of PPy modified electrode are higher than those of iron electrode,which proves that PPy modified iron electrode has certain anti-corrosion performance than iron electrode.(4)The PPy modified iron electrode was used as the anode in the process of DC electrocoagulation technology to treat Cr(Ⅵ)in wastewater.The best experimental conditions obtained after single factor experiment:when the electrolyte concentration is 80 mmol/L,the pH of wastewater is 7,the current density is 32 A/m2 and the voltage is 4 V,the highest Cr(Ⅵ)removal rate of PPy modified electrode is 96%,which is relatively consistent with the best treatment conditions of unmodified iron anode plate.With the increase of voltage,the corrosion inhibition efficiency first decreases and then tends to be stable.It is proved that PPy modified iron anode has a certain anti-corrosion effect on Cr(Ⅵ)in wastewater in DC flocculation reaction,and improves the removal rate of Cr(Ⅵ)under different pH conditions.