The adsorption of bisphenol A by biochars modified with potassium phosphate
Yue Zhao, Mo Yang, Kezhen Qi, Jing Pan
Abstract
Reed and cattail straws, major wetland waste suitable for preparation of porous adsorption materials, were pyrolyzed at 500℃ with varying durations (4, 5 and 6 h) and then modified by potassium phosphate (K3PO4) with distinct mass ratios to obtain modified biochars to remove BPA. The results showed that the adsorption capacity of reed and cattail straw biochars for BPA is gradually increased during a prolonged contact time, and eventually reaches the adsorption equilibrium at 1440 min, moreover also exhibits an enhancement in the adsorption capacity with the increase of the initial BPA concentration. The maximum adsorption capacity achieved for the biochar derived from reed straws carbonized at 500℃ for 6 h and cattail straws carbonized at 500℃ for 5 h, subsequently modified with potassium phosphate solution, is 1.718 mg/g and 1.254 mg/g, respectively. So, indeed, the addition of K3PO4 resulted in a significant increase in total surface area, pore volume, as well as micropore and mesoporous surface area and volume of the biochars. The adsorption processes were fitted with pseudo-second-order adsorption kinetic models and Freundlich models. Characterization results revealed that porous filling, electrostatic attraction, ligand exchange and surface precipitation were the mechanisms of BPA adsorption.