Synthesis of a La(OH)3 nanorod/walnut shell biochar composite for reclaiming phosphate from aqueous solutions

Abstract

A La(OH)3 nanorod/walnut shell biochar composite (LN-WB) was successfully prepared by a parallel flow co-precipitating method and used to reclaim phosphate. LN-WB effectively adsorbed phosphate over a wide pH range (from 3 to 11) and when the initial phosphorus concentration was 10 mg P/L, the removal efficiency was close to 100 %. According to the Langmuir model, the adsorption capacity of LN-WB for phosphate was 75.08 mg P/g, corresponding to a molar ratio of P/La as high as 1.27. The adsorption process fit pseudo-second-order kinetics well and was mainly controlled by chemisorption. The loading efficiency of La on WB was up to 73.89 %. In initial solutions of pH = 3 and pH = 11, most of the La was retained on the biochar after phosphate adsorption. Characterization results indicated that the adsorption mechanism of phosphate on LN-WB was mainly electrostatic attraction, surface precipitation, and ligand exchange.