Rice husks were tested for arsenic removal from water by Nasir et al. [92]. Maximum adsorption was reported on treatment with 0.01 mol/L of HNO3, HCl, H2SO4 or HClO4 using 1.0 g of adsorbent for 5.97 × 10−3 mol/L of arsenic in 5 min. The Freundlich isotherm was followed over a concentration range of 8.69 × 10−5 to 1.73 × 10−3 mol/L arsenic (l/n = 0.83 and K = 4.43 mmol/g). The uptake of arsenic was found to increase with increasing temperature