Research Onnitrate Removal In Groundwater By The Technology Of Electrodeionization Integrated With Electric Catalytic

Due to the unreasonable exploitation of water resources, in our country, human activity has caused serious pollution on groundwater system, which leading to ordeal on production and life. Nitrate pollution has regarded as the first one of the three major pollutants on underground water. The nitrate pollution in north China is serious than the south region. Nitrogen pollution in underground water is mainly caused by human activities, once polluted, it is difficult to recover original state in short period.This issue was based on the technology of electrodeionization integrated with electric catalytic, carried out below experiments: optimization between D407 Ion-exchange resin and 717 Ion-exchange resin, experiment of Ion-exchange resin volume ratio of cation exchange resin and anion exchange resin. Experimental of electrodeionization current efficiency on water nitrate removal, energy saving modification on electrodeionization. The optimization research of removing nitrate wastewater by electric catalytic reduction, and mechanism of Pd/Sn modified ACF electrode on NO3- electric catalytic reduction. Eventually integrated electrodeionization with electric catalytic reduction, under the respective optimization operation, verifiedthe separation and reduction of nitrate effects of the integrated reactor.The results of static adsorption and dynamic adsorption experiments indicated that 717 resin saturated adsorption amount(40.82 mg·g-1) slightly greater than D407 resin adsorption amount(39.21 mg·g-1), but the NO3-adsorption effect of D407 resin is obviously better than 717 resin, under the concentration of 300mg·L-1NO3--N solution, the minimum equilibrium adsorption amount of D407 was 13.28 mg·g-1, 717 largest equilibrium adsorption quantity only 12.75 mg·g-1. And the Langmiur adsorption constants K value of D407 is greater than 717. The presence of Cl-,SO42- ion had less significant influence on D407 resin, but significant influence on 717 resin. Dynamic penetration point of D407 resin was 72 m L·m L-1, 717 was 54 m L·m L-1, after a series of experimental, it actuallyproved that NO3- adsorption effect of D407 resin is obviously better than 717 resin.Through orthogonal experiments and simplify improved of the reactor ultimately got the optimal parameters of electrodeionization as below: Water flow 20 ml·min-1, voltage 35 V, concentration of inflow wastewater 70 mg·L-1, electrode water 50 mg·L-1. Under above conditions, the current efficiency of reactor were more than 70%, NO3- removal rate exceeded 98%, effluent NO3--Nconcentrations was less than 2 mg·L-1, simplify improved of the reactor decreased voltageover 10 V. And achieve the purpose of saving energy and reducing consumption.Combined single factor experiment and orthogonal experiment eventually got the the optimal parameters of electric catalytic reduction as below: current 0.68 A, initialnitrate concentration 250mg·L-1, p H6.4. In this conditions, maximum NO3--N removal of electric catalytic reduction were more than 50 mg, N2 selectivity rate reached 62%, the catalytic activity of the catalyst was to 20 mg(g·h)-1, but the current efficiency is low, less than 10%.Operated integrated reactor under the best parameters condition, the current efficiency were over 70%, NO3- removal rate beyonded 98%, effluent NO3--N concentrations was lower than 2 mg·L-1, water conductivity 14 us·cm-1, final effluent p H 8.74, the quality of yielding water nearly closed to pure water.Run the electric catalytic reduction for 8h, N2 selectivity rate reached56%, the current efficiency reached to 43%. Used 7.2 L, 70 mg·L-1 NO3--N solution as experimental raw water, after 36 h uninterrupted continuous operation test, the total NO3- ions removal achieved 77.78%, and the final N2 selectivity rate reached 67.5%, water conductivity Leveled off after 120 min. But simulated groundwater level Ⅳ water obvious decreased the electric catalytic activity,although there was no significantly affect.In conclusion, technology of electrodeionization integrated with electric catalytic inherited the both advantage of electrodeionization and electric catalytic reduction, efficiently and quickly removed NO3- ions in water, and transformed most of NO3- ions into N2 completely removed. The technology will be improved through further experimental, with obvious advantage thanother denitrification technologies, the method must more ave a good application prospect.