Fabrication of Polyvinylpyrrolidone-Stabilized Nano Zero-Valent Iron Supported by Hydrophilic Biochar for Efficient Cr(VI)Removal from Groundwater

摘要

Today,eco-friendly and cost-effective nanomaterials are vital to ultimately removing contaminants from groundwater as an essential part of freshwater.In this study,polyvinylpyrrolidone(PVP)-stabilized nano zero-valent iron(nZVI)supported by hydrophilic wheat straw biochar(HWS)(PVP-nZVI@HWS)was prepared and compared with the nZVI-HWS sample for Cr(VI)removal from aqueous media.The morphology and functional group structure of PVP-nZVI@HWS composites demonstrated that nZVI could be dispersed homogeneously on the hydrophilic biochar substrate by adding PVP(owing to a large number of OH functional groups).Based on BET analysis,despite a minimal reduction in the surface area of the PVP-nZVI@HWS hybrid material compared to the nZVI-HWS sample(7.19m~2g~(-1)),the pore volume and adsorption average pore diameter increased.Superior reduction efficiency(99.63% elimination in only 5 min)of 20 ppm Cr(VI)was achieved using the proposed hybrid material.Pseudo-second-order kinetics(R~2=1)and Langmuir isotherm models(R~2 = 0.9407)were attained via the PVP-nZVI@HWS(0.2 gL~(-1))under groundwater condition(sodium chloride solution at pH = 3.2).In addition,on a large scale,the proposed hybrid material could reduce 97.22% of Cr(VI)in 180 minutes from the water.The mechanism of catalytic and absorption behaviour for two catalysts was compared,and the investigations showed that absorption action for the nZVI-HWS sample,and catalytic behaviour for the PVP-nZVI@HWS hybrid material were predominant.