Adsorptive Behavior of Arsenic(III) Ions from Aqueous Solution onto Forestry and Agricultural Waste Biochar Pyrolyzed at 400°C

Abstract

Sorption capacity of two different biochar (saw dust and rice straw) was evaluated in the recovery of arsenic from aqueous solutions. Biochar from rice straw and saw dust were obtained from pyrolysis of biomass at 400°C. The optimum sorption conditions were studied for different concentrated monometallic system. Sorption studies were performed at different pH, contracting time and different initial metal ion concentration in the batch mode. The optimum pH was 3 for recovery of As(III) and kinetic studies yielded an optimum equilibrium time of 50-60 minutes with an adsorbent dose of 1 g/L and initial concentration ∼20 mg/L for As(III) ions. As(III) ions in aqueous solution were transported to biochar surface through adsorption and intra-particle diffusion process. Experimental data for As(III) ions was fitted a Langmuir model with R2 value for As(III) 0.969, 0.879 for saw dust and rice straw respectively. The Freundlich constant, KF values for removal of As(III) ions by saw dust and rice straw were 0.9127, 0.8951 respectively. The 1/n value for arsenic ions obtained from saw dust and rice straw were 0.209, 028 and indicate the normal sorption of As(III). The values indicated the affinity of the sorbent towards the uptake of As(III) ions were favorable and rice straw and saw dust biomass can be used to remove Arsenic(III) ions from aqueous phase.