Functionalizing biochar with Mg-Al and Mg-Fe layered double hydroxides for removal of phosphate from aqueous solutions

This study examined phosphate adsorption of bamboo biochar functionalized with varying amount of Mg-Al and Mg-Fe (3:1) layered double hydroxides (LDH). Results indicated that the composite containing 40% Mg-Al LDH exhibited the highest phosphate adsorption with >95% phosphate saturation achieved within 1 h, following the pseudo-second-order kinetics model. Characterization and adsorption isotherm of this composite revealed interlayer anion exchange and surface adsorption as the predominant adsorption mechanism at low phosphate concentrations and phosphate precipitation at high concentrations. A lettuce seedling bioassay further demonstrated that the spent LDH/biochar composite can be recycled as a slow-release fertilizer to enhance food production. (C) 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.