Surface charge modification of chloromethylated polystyrene beads with NaH for the removal of sulfamonomethoxine

• The surface of chloromethylated polystyrene beads modified by NaH became positive.
• Chloromethylated polystyrene beads modified by NaH can effectively remove sulfamonomethoxine in anionic form from solution.
• The adsorbent could be successfully regenerated using HCl solution.

It is difficult to remove sulfonamide antibiotics in anionic form from aqueous solution. In this study, the surface properties of chloromethylated polystyrene beads (CP) were modified by sodium hydride (CP-M) to enhance sulfamonomethoxine (SMM) removal. The surface of CP-M became positive charged after modification. The effects of contact time, pH, ionic strength, and temperature on removal of SMM by CP-M have been investigated. The pH greatly affected adsorption efficiency, and the amount of SMM adsorbed on CP-M increased at pH levels above its pKa,2 value. SMM in the anionic form was more readily adsorbed onto CP-M compared to those in the cationic and neutral forms, with adsorption predominately occurring via electrostatic interactions. The amount of adsorbed SMM decreased with increasing ionic strength for all four cations studied. Five error functions have been used to treat the kinetic data and equilibrium data using nonlinear optimization techniques. The rate of adsorption was adjusted to a nonlinear pseudo-second-order kinetic model and equilibrium data could be fitted by a linear with intercept model. The thermodynamic parameters indicated that the overall adsorption process was exothermic and spontaneous, with the adsorption mechanism being mainly controlled by an electrostatic attraction force. The adsorbent could be regenerated using HCl solution.

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