Peat, Rice Husk and Rice Husk Carbon as Low-Cost Adsorbents for Metals from Acidic Aqueous Solutions

Abstract

We assessed the abilities of rice husk (RH), rice husk carbon (RHC), and peat to adsorb Cr, Fe, Mn, Ni, Zn, and Pb from aqueous solutions compared with commercial activated carbon (AC). The sorbent capacities were evaluated by percolation of aqueous solutions containing these six metals through adsorbent columns. Metal concentration was monitored by total reflection X-ray fluorescence (TXRF). Initial metal concentrations added to the columns were between 25 and 50 mg L⁻¹, while those in the treated effluent ranged from 0.004 to 0.96 mg L⁻¹. The adsorption capacities of the sorbents for these metals were examined by non-linear Langmuir and Freundlich models. The maximum adsorptive capacities expressed as individual metal (q_m) sums were 67.7, 86.9, 80, and 44.6 mg g⁻¹ for AC, RHC, peat, and RH, respectively. The resulting isotherm parameters were used to compare the performance of the sorbents and to determine the ΔG values. After percolation through the adsorbent columns, the ecotoxicity of the eluates were determined with the probe Daphnia magna. Effluents from the rice husk sorbent column exhibited the lowest toxicity. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the supplemental file.