| Modification of selenium contaminated water is of great importance for mitigating water shortage. The dope of metal ions during the pyrolysis of biomass can improve the quality of biofuel as well as produce biochar supported nano metal structure.In this study, the low-cost and simple synthesize of biochar supported nZVI(BC-nZVI) through in situ carbothermal reduction of Fe(Ⅲ) preloaded biomass was adapted. BC-nZVI synthesized under different temperatures were characteriz ed to get a better understanding of the formation of nZVI and the transition of the biomass. XRD, SEM and TEM Characterization of the prepared composite showed that zero valent iron particles at the size of tens to hundreds nanometers were embedded in the biochar matrix. Meanwhile, biochar matrix well protected nZVI from the oxidation by air.The removal of Se(Ⅳ)by BC-nZVI in air was first studied. Batch experiments showed that BC-nZVI exhibited good ability for selenite removal despite of high ion strength and excessive co-existing anions. Besides, the effect of solution p H on selenite removal by BC-nZVI was mitigated benefited by the buffering effect of biochar. Further study to investigate the effects of ethylene diamine tetraacetic acid(EDTA)and 1,10-phenanthroline revealed that the process of selenite removal by BC-nZVI was combined of reduction and adsorption.The anoxic removal of Se(Ⅵ) and Se(Ⅳ)was also studied. Batch experiments showed that BC-nZVI exhibited good removal ability toward Se(Ⅵ) and Se(Ⅳ) even in alkaline solution. The less facile of selenate removal was caused by its resistance in the diffusion boundary layer. The removal mechanism was studied: Se(Ⅳ)can be immobilized either by fast adsorption or by firstly being reduced and then d epositing as elemental Se, and the adsorbed Se(Ⅳ) can also be reduced. While the removal rate of Se(Ⅵ) was limited by its resistance in the diffusion boundary layer, once arrived at the BC-nZVI surface, it can be reduced to Se(Ⅳ)followed by immediate adsorption. |
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