Adsorption of o-tolylthiourea on two polar-modified hyper-cross-linked resins: Equilibrium, thermodynamic and kinetic studies

Abstract

Abstract Two polar monomers, Trimellitic anhydride and o-phthalic anhydride, are employed to copolymerize with the non-porous gel-type chloromethylated poly(styrene-divinylbenzene) (NP-CLPs), and synthesized two polar-modified hyper-cross-lined resins. The resins were efficient for adsorption of o-tolylthiourea, and possessed the largest equilibrium capacity (221.2 mg/g for TMAMR, and 206.7 mg/g for PAMR). The influences of adsorption temperature, solution pH, and salt content of the solution were studied by the static adsorption method. The Freundlich and Langmuir isotherm model were used to fit equilibrium data for all investigative temperatures (288–318 K). The Langmuir model was better than the Freundlich model at 288 K; however, with the increasing temperature the Freundlich and Langmuir models could all well describe the isotherm data. The thermodynamic parameters (ΔH0, ΔS0, and ΔG0) showed that the adsorption of o-tolylthiourea was feasible, exothermic, and spontaneous from 288 K to 318 K. The kinetic data were fitted by pseudo-first order, pseudo-second order, and intraparticle diffusion equations. Differences in adsorption of o-tolylthiourea between TMAMR and PAMR resins were interpreted by the frontier orbital energy level difference between resins and o-tolylthiourea calculated with the semi-empirical method AM1.