A novel pigeon waste based biochar composite for the removal of heavy metal and organic compound: Performance, products and mechanism

Abstract

Recently, a large number of agricultural wastes have been extensively converted into biochar based materials, these biochar materials have been popularly employed in the removal of various pollutants from environment. Herein, a novel pigeon waste based biochar composite (FeBC) was firstly synthesized and applied for hexavalent chromium (Cr(VI)) and p-nitrophenol (PNP) adsorption in water. The most relevant findings showed that FeBC exhibited a superior performance on Cr(VI) and PNP adsorption compared with pristine biochar. The Cr(VI) monolayer adsorption onto FeBC might be dominant, and Cr(VI) adsorption by FeBC was an endothermic process. Both Cr(VI) and PNP adsorption behavior were well fitted with the pseudo-second-order kinetic model, Elovich, intra-particle diffusion (IPD), liquid film diffusion kinetic (LFD) and chemical reaction models. Both the pathway of PNP degradation and mechanism for Cr(VI) and PNP adsorption over FeBC were proposed. Almost half of Cr(VI) was reduced into Cr2O3 and Cr(OH)3, both reduction and precipitation reactions might be dominant in Cr(VI) adsorption. O2•−, 1 O2 and •OH were involved in PNP removal reaction, but the contribution of •OH was small. The oxidation, π-π interaction and hydrogen bonds interactions might be involved in this PNP removal process, and PNP was oxidized to form several intermediates via hydroxylation and ring cleavage reactions. This study could provide a novel treatment strategy for the simultaneous decontamination of effluents combined with heavy metals and organic compounds in realistic remediation application.