Study On Removal Of Nitrate From Rural Groundwater By Modified Activated Carbon Fiber Enhanced CDI

As a typical inorganic pollutant that is difficult to remove,nitrate has a great threat to human health.In recent years,the safety of water quality in rural drinking water has gradually received attention.The problem of excessive nitrates is a major problem in solving rural water quality safety.However,conventional conventional water treatment techniques are difficult to remove nitrates.Therefore,this paper will use electrosorption?CDI?technology to treat excessive nitrate in rural drinking water.In order to optimize the electrode with better nitrate removal effect,the paper used three different modification methods?ie NaOH reduction modification,HNO₃ oxidation modification,TiO₂ loading modification?to modify the activated carbon fiber?ACF?.The adsorption results of nitrates showed that when the concentration of sodium nitrate was200 mg/L,the removal rates of the three modified methods changed from 14.9%before unmodified to 27.6%,24.86%,and 13.6%,respectively.Further study on the influencing factors affecting the removal of nitrates,the characterization of the three modified ACF shows that the hydrophilicity of the ACF surface affects the adsorption rate of ACF,the better the hydrophilicity,the faster the adsorption rate.The pore size distribution of the ACF micropores affects the specific capacitance of the ACF electrode,and the specific capacitance determines the adsorption capacity of the ACF electrode for nitrate.Based on the capacitive deionization technology,a set of capacitive deionization?CDI?devices were designed and fabricated,and the operating parameters were explored to obtain the optimal operating parameters of the CDI device:the plate spacing was 3 mm,and the influent flow rate was 50 mL/min.The charging current is 0.4 A and the cut-off voltage is 1.6 V.Further investigation of the factors affecting the desorption time of the CDI device,the desorption of the CDI device suitable for short-circuiting of the electrode,but the difficulty of desorption,the need to use large flow flushing.Under the optimal operating parameters,the adsorption performance of CDI devices on nitrate in simulated water was studied.When the initial concentration of nitrate nitrogen is 30 mg/L,when the deionized water and tap water are used for water distribution,the effluent compliance time of the CDI device is 42 min and 48 min,respectively,and the highest removal rate is 60%.The water volume is 2.1 L and 2.4 L respectivelyBased on the CDI device,a membrane capacitance deionization?MCDI?device was designed and fabricated,and its operating parameters were explored to obtain the optimal operating parameters of the MCDI device:inlet flow rate 50 mL/min,charging voltage1.8.V.Further investigation of the factors affecting the desorption time of the two sets of devices,the MCDI device is desorbed in a manner suitable for reverse voltage,and the backwashing flow rate is 100 mL/min.Under the optimal operating parameters,the adsorption performance of nitrate on the MCDI device in simulated water was studied.When the initial concentration of nitrate nitrogen was 30 mg/L,the effluent compliance time of MCDI device was 66 min and 76 min,respectively,when deionized and tap water were used.The highest removal rates were 80%and 81.67%,respectively.The treated water volumes were 3.3 L and 3.8 L,respectively.Further research on the cost of the two sets of equipment can be obtained.The operating costs of CDI and MCDI devices are0.28 yuan/ton and 0.30 yuan/ton respectively.