Study On The Enhanced Removal Of Cr(â…¥) In Water By Nanoscale Zero-valent FeO Supported On Bentonite Modified With CTMAB And Its Mechanism

Nanosacle iron particle is a type of reluctant environmental in-situ remediationmetal applied in the underground water and urgent pollution. This nanoscale metal hasbecome a research focus because of its large specific area and high reactivity. But it islimited in application since nanosacle iron particles are easy to aggregate and lackadsorptive capacity in wastes.As host material, the natural mineral bentonite was used to supporte thenanosacle iron particles to resolve the agglomeration problems. The cationicsurfactant CTMAB was applied to modify the bentonite and nanoscale iron particlessimultaneously to enhance the adsorbability and reduced efficiency. The(B-nZVI)/CTMABs were prepared. The properties of the (B-nZVI)/CTMABs throughchanging the molar ratio of FeSO4to NaBH4(represent by N) were analyzed by SEM,XRD and XPS test methods. The efficiency of CrO42-in the water removed bydifferent materials was investigated and the removal mechanism was explored.The reaserch indicated that there existed not only Fe0but also Fe2+in(B-nZVI)/CTMAB of n(FeSO4)/n(NaBH4)=1and the nanoscale iron particles weredispersive and linked themselves on the surface of bentonite. The removal efficiency(84.1%) of Cr(â…¥) in the water was achieved by (B-nZVI)/CTMAB of N=1.Compared with other materials such as raw bentonite, nZVI and unmodified B-nZVI,(B-nZVI)/CTMAB improved the removal efficiency much and the correspondingreaction rates also increased. The pH value and Cr(â…¥) initial concentration have astrong influence on the removal efficiency of Cr(â…¥) in the water. The removal effectof light concentration of simulative underground water containing As(â…¤)(5mg/L),Cr(â…¥)(2mg/L) and the electroplating wastewater containing Cr(â…¥)(5mg/L) by(B-nZVI)/CTMAB were showed good. The specific values were97.2%and96.4%,respectively.The interlayer spacing and specific surface area of modified bentonite bydifferent dosage of CTMAB with a certain extent of improvement were increased and the surface zeta potential changed positive from negative. Furthermore, the nanoscaleiron particles were more dispersive. When the concentration of CTMAB was10g/L,the zeta potential (1.94mV) of10-(B-nZVI)/CTMAB and the Cr(â…¥) removalefficiency were the highest. L-H model indicated that the mechanism of (B-nZVI)/CTMAB removing Cr(â…¥) in the water contained two processes of adsorption andreduction. After reaction, Fe0was oxdated to Fe3+and most Cr(â…¥) was Cr(â…¢), thefinal production was (CrxFe1-x)(OH)3.