Synthesis of Salicylic Acid-Polystyrene Type Chelate Resin with a New Route

A new route to synthesize salicylic acid-polystyrene type chelate resin is developed. In the presence of Lewis acid catalyst SnCl₄, the chloromethylation reaction of crosslinked polystyrene microspheres (CPS) was first performed using 1,4-bis(chloromethoxy)butane which is un-carcinogenic as a chloromethylation reagent, and the chloromethylated crosslinked polystyrene microspheres (CMCPS) were obtained. Subsequently, the nucleophilic substitution reaction between the benzyl chloride groups on CMCPS microspheres and 5-amino salicylic acid (ASA) was conducted, and chelate resin ASA-CPS was successfully obtained. The effects of main factors on the nucleophilic substitution reaction were examined. The chelating property of the prepared ASA-CPS resin for Fe³⁺ ion was tested preliminarily. The experimental results show that the reaction rate of the nucleophilic substitution reaction between the benzyl chloride groups on CMCPS microspheres and ASA is independent of the concentration of the nucleophilic reagent ASA. Therefore, the reaction is a typical unimolecular substitution reaction, namely, the substitution reaction has a mechanism of S_N1. The solvent with stronger polarity is advantageous to the fracture of C-Cl bond of the benzyl chloride groups, so the polarity of the solvent influences the substitution reaction rate greatly. To increase the reaction temperature also makes for the substitution reaction. The ASA-CPS resin possesses very strong chelating ability towards Fe³⁺ ions by right of the synergism of chelation and electrostatic interaction., and the adsorption capacity can get up to 21 g/100 g.