Arsenate Adsorption from Aqueous Solution onto Fe(III)-Modified Crop Straw Biochars

Abstract

Abstract Biochars generated from peanut straw (PS) and rice straw (RS) were modified using Fe(III), which were then evaluated for As(V) adsorption in batch experimental systems. Results indicated that noncrystalline Fe hydroxides formed on the biochars during modification, reducing the negative charge on the biochar surface, and consequently the electrostatic repulsion to As(V) adsorption. Adsorption capacities of unmodified biochars for As(V) were low, but Fe(III) modification considerably enhanced As(V) adsorption by the biochars. The Langmuir isotherm fit the adsorption data well and could be used to describe As(V) adsorption by the Fe(III)-modified biochars. Maximum adsorption capacities for As(V), calculated using the Langmuir equation, were 33.7 g/kg for Fe(III)-modified PS biochar and 27.0 g/kg for Fe(III)-modified RS biochar at pH 5.0. As(V) adsorption capacities of both Fe(III)-modified biochars were much greater than that for goethite (13.1 g/kg) at pH 5.0. As(V) was mainly adsorbed by the Fe(II...