Adsorption removal of chlortetracycline hydrochloride using the poly(styrene-divinylbenzene) matrix from aqueous solution

The adsorption capacities of poly(styrene-divinylbenzene) resins were investigated, and resin SA-2, HZ202 and D101 showed the excellent adsorption property at the low doses of chlortetracycline hydrochloride (CH) solution, while resin D101 had outstanding performance at the high dose. The CH adsorption capacity and removal percentage of the D101 resin were 53.2 mg/g and 73.9%, respectively, when the volume of solution containing 5 mg/mL CH was 30 mL. Subsequently, adsorption kinetics, isotherms and thermodynamics for removal of CH from aqueous solution were studied under the different CH concentration. The adsorption process was complied with the pseudo-second-order model and Langmuir model. The adsorption process was fast, and adsorption equilibrium was achieved within 2 h. Based on the Langmuir model, the maximum adsorption capacities of CH on resin D101 were 118.20 mg/g at 298 K, 104.76 mg/g at 303 K and 91.68 mg/g at 308 K. Thermodynamic parameters calculated from the adsorption data at different temperature and CH concentration showed that the adsorption process was exothermal and spontaneous. The negative increment H also suggested that the main interaction between CH and resin D101 was physical adsorption. The adsorption mechanism was investigated using a scanning electron microscopy, N-2 adsorption-desorption isotherms, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction spectra. Positive effect of Mg2+ on CH adsorption was observed. Resin D101 could be regenerated by ethanol containing 8% MgCl2, and the CH adsorption capacity of resin D101 decreased by 11.3% after five adsorption-desorption cycles, which displayed that the resin D101 was a promising adsorbent for CH removal in industrial applications.