Removal of Cr (III) Ions from Wastewater using Sawdust and Rice Husk Biochar Pyrolyzed at Low Temperature

Abstract

Sorption capacity of two different biochar (saw dust and rice straw) was evaluated in the recovery of chromium from wastewater. The optimum pH was 5-7 for recovery of Cr(III). Optimum yield was received after 1 hour contacting time with an adsorbent dose of 1 g/L and initial concentration was ∼20 mg/L. Cr(III) ions were transported to biochar surface through adsorption and intra-particle diffusion process. Langmuir and Freundlich kinetic parameters indicated that the affinity of the sorbent towards the uptake of Cr(III) ions and adsorptions were favorable. According to FTIR analysis of Cr(III) ions bound to active sites either electrostatic attraction or complexation mechanism. These results indicated that carbonyl, hydroxyl, amine and halides are the main adsorption sites in saw dust and rice straw biochar and these functional groups complexes with Cr(III) ions in the aqueous solution and changed the chemical environment of the functional groups in the biochar.