Adsorption of Phosphate by Modified Cassava Stalk

Cassava stalk was modified into an anion exchanger using epichlorohydrin,ethylenediamine and triethylamine, and adsorption ability of the anion exchanger for phosphate was examined through batch experiments. The influence factors on the adsorption,including adsorbent dosage,pH,initial concentration of phosphate and contact time,were tested. Results showed that adsorption ability of modified cassava stalk for phosphate increased,and the best phosphate removal rate of 95% was obtained at 4 g/L of adsorbent dosage and pH range of 3.0~8.0. The adsorption data fitted the Langmuir and Freundlich adsorption isotherm,and the maximum adsorption capacity was 2.58 mmol/g. The adsorption of phosphate onto the adsorbent was a fast adsorption process,reaching balance at 30 min. The second order reaction equation can well reflect the adsorption process,with the equilibrium adsorption amount of Qequite close to the experimental values. The adsorption rate was controlled by inter-particle diffusion,but it was not the only controlling factor.