A bifunctional adsorbent with high surface area and cation exchange property for synergistic removal of tetracycline and Cu2+

Abstract

Abstract A novel bifunctional adsorbent with high surface area and cation exchange character (HAR-2) was prepared via copolymerization and hydrolysis reactions for the coremoval of tetracycline and Cu 2+ . HAR-2 possessed large specific surface area of 394 m 2 /g and high weak cation exchange capacity of 1.06 meq/g. The adsorption kinetics of TC or Cu 2+ fitted both pseudo-first-order and pseudo-second order equations in single-substrate solution, whereas the adsorption kinetics were better described by pseudo-second order model in binary solutions. The adsorption of TC was an exothermic process, while the Cu 2+ adsorption process was endothermic. The adsorption isotherms of TC and Cu 2+ fitted the Langmuir model, suggesting a monolayer adsorption process. The adsorbed amount of TC was pronouncedly enhanced in the presence of Cu 2+ due to the formation of tertiary surface complex HAR–Cu 2+ –TC. Likewise, the adsorption of Cu 2+ was significantly improved by forming HAR–TC–Cu 2+ complex in the presence of TC. The uptake of Cu 2+ increased as pH increased, while the adsorbed amount of TC increased as pH rose from 2 to 3 but decreased when pH was further elevated from 3 to 6. The presence of NaCl exerted no significant influence on the adsorption of TC and negatively affected the adsorption of Cu 2+ . HAR-2 exhibited high stability over 5 repeated uses, only losing 6.3% and 18.4% of the initial adsorption capacity for TC and Cu 2+ , respectively.