The contribution of lignocellulosic constituents to Cr(VI) reduction capacity of biochar-supported zerovalent iron

Biochars (BCs) derived from individual and blending lignocellulosic constituents were prepared to harbor zerovalent iron (ZVI/BC) in an effort to discriminate significance of each constituent or combination in ZVI/BC for Cr(VI) removal. BCs and ZVI/BC were characterized by TGA/GSC, XRD, Raman and BET analyses. Cellulose (BCC) and hemicellulose (BCH)-derived BCs has greater C content, H/C ratio, surface area and mass loss than BCs derived from lignin or lignin-containing biopolymer blends (BCLX). As per sorption and XPS analysis, ZVI/BC demonstrated greater Cr(VI) removal capacity than respective BCs, in which reduction accounted for over 77% Cr(VI) detoxification. Cr(VI) reduction by ZVI harbored by BCC and BCH was 19.72-16.54 g kg(-1), compared to 5.97-4.26 g kg(-1) for BCLX. ZVI/BC prepared by three-biopolymer blends with (12.63 g kg(-1)) or without (12.32 g kg(-1)) mineral approximated pinewood-BC (BCP) (13.02 g kg(-1)) for Cr(VI) reduction, suggesting minerals are not important constituent. Tafel analysis showed BCC and BCH, with lower ID/IG ratio owing to greater graphitization, were more conducible to transfer electron of ZVI in Cr(VI) reduction than BCLX. Thus, cellulose, hemicellulose and lignin can offer a good prediction of property of natural biomass, in which BCC and BCH favor electron transfer of ZVI but BCL is not electroactive. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study demonstrated that biochars derived from cellulose and hemicellulose have higher Cr(VI) removal capacity and are more conducive to electron transfer for ZVI, while biochars derived from lignin perform less effectively.