Covalent-organic polymer-derived carbons: An effective adsorbent to remove sulfonamide antibiotics from water

A new mesoporous N-doped carbonaceous material was prepared for the first time from a microporous triazine polymer (MCTP) (a covalent-organic polymer) by high-temperature pyrolysis after loading Zn(OH)2. The material, denoted ZCDC, was successfully applied for the adsorptive removal of sulfonamides like sulfamethoxazole (SMX) and sulfachlorpyridazine (SCP) from aqueous solutions. ZCDC showed better performance compared with the carbon prepared from MCTP only (without loading Zn(OH)2) due to the increased mesoporosity. The kinetic studies indicated that a practical equilibrium on ZCDC adsorption can be achieved within 1 h and 4 h for SMX and SCP, respectively. The adsorption isotherms can be fitted with the Langmuir adsorption model and one ZCDC, ZCDC(10), had a maximum adsorption capacity (Q0) of 514 and 430 mg/g for SMX and SCP (at pH 7.0), respectively. Moreover, the ZCDC(10) ranked the third position (with a Q0 value of 514 mg/g), after N-doped beta zeolite-derived carbon and MOF-545, in SMX adsorption. Based on the adsorption and surface charge under wide pH ranges, the adsorption could be attributed to the favorable pore structure, π–π, and H-bonding interactions. The ZCDC(10), showing the excellent performance in sulfonamides adsorption, was easily regenerated by washing with acetone for up to five adsorption-desorption cycles.