Rice straw derived adsorbent for fast and efficient phosphate elimination from aqueous solution

Abstract

Rice straw (RS) is an abundant agricultural residue with plentiful hydroxyl groups. In this study, a low-cost and effective RS-based phosphate adsorbent (RS-PA) was prepared through a three-step reaction process, successively with epichlorohydrin (ECH), ethylenediamine (EDA), and triethylamine (TEA). The elimination process of phosphate was optimized by considering altered adsorption conditions. The successful production of RS-PA was confirmed by FTIR, organic element, and zeta potential analyses. The key factors influencing the phosphate adsorption were the temperature in the second reaction step and EDA dosage. Langmuir isotherm and pseudo-second-order kinetic models predicted the phosphate adsorption on the RS-PA very well. A complete phosphate removal was achieved at 50 mg/L phosphate concentration, 10 g/L adsorbent dosage and 25 ℃ in 10 min. The exothermic nature of phosphate adsorption on RS-PA was confirmed since the temperature rise reduced the adsorption of phosphate on the adsorbent. These results demonstrate that full component rice straw-based phosphate adsorbent was successfully prepared for the removal of phosphorus compounds from waste water.