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

• A novel bifunctional adsorbent HAR-2 was successfully prepared.
• The surface area of HAR-2 was 394 m2/g and cation exchange capacity was 1.06 meq/g.
• Both HAR–TC–Cu2+ and HAR–Cu2+–TC complexes were formed on the surface of HAR-2.
• High pH inhibited tetracycline adsorption and salinity suppressed Cu2+ uptake.
• The above inhibitory effect was balanced out in binary system due to complexation.

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 Cu2+. HAR-2 possessed large specific surface area of 394 m2/g and high weak cation exchange capacity of 1.06 meq/g. The adsorption kinetics of TC or Cu2+ 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 Cu2+ adsorption process was endothermic. The adsorption isotherms of TC and Cu2+ fitted the Langmuir model, suggesting a monolayer adsorption process. The adsorbed amount of TC was pronouncedly enhanced in the presence of Cu2+ due to the formation of tertiary surface complex HAR–Cu2+–TC. Likewise, the adsorption of Cu2+ was significantly improved by forming HAR–TC–Cu2+ complex in the presence of TC. The uptake of Cu2+ 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 Cu2+. HAR-2 exhibited high stability over 5 repeated uses, only losing 6.3% and 18.4% of the initial adsorption capacity for TC and Cu2+, respectively.