| The rapid development of the tanning industry has also had a certain impact on the environment.During the chrome tanning process,a large amount of chromium-containing wastewater will be discharged.Some of the chromium mainly exists in the form of complex compounds.Substances,it is difficult to remove them by chemical precipitation.Therefore,this study used modified activated carbon to prepare electrode materials and combined with membrane capacitance deionization technology(MCDI)to remove the complexed chromium in the discharged chromium-containing wastewater,which has important theoretical significance and application for achieving the discharge of tannery wastewater.value.In this topic,ethyl orthosilicate is used as an organic synthesis intermediate,and 3-aminopropyltrimethoxysilane is used as a modification modifier to modify the activated carbon powder by amination.The effects of reaction time,reaction temperature and the proportion of modifier preparation on the performance of electrode materials were discussed.Electron microscopy(SEM),infrared spectroscopy(FTIR),specific surface area and pore size measurement were used to characterize the prepared aminated activated carbon.In the application study,the effects of adsorption reaction temperature,solution pH,coexisting ions in the solution on the adsorption of complex chromium were investigated.Adsorption kinetic model and adsorption isotherm model were used to fit and analyze the experimental data.The modified activated carbon is prepared as an electrode,and a circulating membrane capacitor deionization device is assembled.The device is used to remove chromium and optimize the process parameters,and the electrosorption kinetics is studied.The results show that the best preparation conditions for aminated activated carbon are:ammonia water volume is 6 mL,volume ratio of ethyl orthosilicate and 3-aminopropyltrinethoxysilane is 1:0.2,reaction time is 3 h,temperature is at 30?,the adsorption capacity reached 8.5 mg/g under this condition.Through characterization,it was found that the activated carbon was successfully attached to the amino group,and through scanning electron microscopy,it was found that the surface of the activated carbon became rough after modification,the specific surface area decreased,and the pore size increased slightly.The higher the temperature,the more unfavorable is the adsorption of complexed chromium by aminated activated carbon.When the pH is less than 3,the adsorption capacity of chromium is lower.K+and Na+have a greater influence on the adsorption of chromium on the activated carbon than Mg2+.The adsorption kinetics can better fit the quasi-second-order kinetics,indicating that the process of adsorption of complex chromium is mainly chemical adsorption.The adsorption isotherms were fitted with Langmuir and Freundlich models.The correlation coefficients are very high,indicating that the process of adsorbing complex chromium is a combination of single-layer covering and multi-layer adsorption.Add a certain proportion of ethanol,water,polytetrafluoroethylene,and conductive carbon black to the activated carbon powder and mix them evenly.Use a roller machine to tablet the activated carbon to prepare an electrode plate for chromium removal in the MCDI process.The parameters of the membrane capacitor deionization process were optimized.Finally,the power supply voltage was 1.2 V,the initial concentration of the solution was 250 mg/L,and the solution flow rate was 20 mL/min.Under this condition,the maximum electrode adsorption capacity was 7.5 mg/g.The effect of quasi-second-order kinetic fitting on the electrode electro-adsorption process is better.Using this method to treat the low-concentration and stable chromium wastewater discharged from the tanning industry has great application prospects. |
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