Simultaneous Removal Of Nitrosamines And Hexavalent Chromium From Water By GAC_Fe(0) System

In view of the health and safety of drinking water caused by the combined pollution of nitrosamines and their toxic enhancing effect substances Cr???in the typical water environment of high-incidence areas of digestive tract tumors,combined with the urgent need for the improvement of national drinking water quality standards,this study proposes GAC_Fe?0?system for simultaneous removal of nitrosamines from water and Cr???complex pollution.The simultaneous removal of nitrosamines and Cr???by GAC_Fe?0?system was studied.The iron-carbon ratio,nitrosamine and Cr???concentration,GAC_Fe?0?dosage,pH,humification were investigated.The effect of acid and other factors on the removal efficiency;the nitrosamine removal process was fitted by pseudo first-order reaction kinetics equation and pseudo-secondary reaction kinetics equation respectively;for further study the removal mechanism,Simultaneous removal of water nitrosamines and their toxicity enhancing effect substances Cr???reaction pathway was explored by the GAC_Fe?0?system.The results are as follows:?1?In the GAC_Fe?0?system,when the iron-carbon ratio is 1:3,the removal efficiency of nitrosamines is the highest.The removal rate of nitrosamines and Cr???promoted each other.When the initial concentration of Cr???was 1 mg/L,the removal efficiency of nitrosamines was the best;with the increase of nitrosamine concentration,The removal rate of Cr???is gradually increased;the increase of pH has no significant effect on the removal rate of nitrosamines,but significantly inhibits the removal of Cr???;the presence of anions inhibits the removal of nitrosamines,but significantly promotes Cr???removal effect;The removal rates of nitrosamines and Cr???were inhibited in the presence of HA.?2?The kinetic analysis showed that the correlation coefficients R₁² of NDMA,NMor,NMEA,NDEA,NDPA and NDBA were 0.9926,0.9805,0.9586,0.8976,0.8135,0.9180,respectively;and the correlation coefficients R₂² were 0.9999,0.9902,0.9898,0.9846,0.9193,0.9710,R₁² is less than R₂²;the correlation coefficient R₁² of Cr???is 0.9993,R₂² is 0.9030,and R₁² is greater than R₂².Therefore,the second-order reaction kinetic equation can better fit the removal process of nitrosamines,and the removal process of Cr???is more consistent with the first-order reaction kinetics equation.?3?The degradation mechanism indicates that most of the nitrosamines and Cr???are first adsorbed by activated carbon,then removed by zero-valent iron,and the rest are directly removed by zero-valent iron;the degradation products are mainly secondary amines and nitrates,nitrite,trivalent chromium and chrome iron complexes...