Synthesis, characterization of salicylic-HCHO polymeric resin and its evaluation as a boron adsorbent

In this study, a novel salicylic-HCHO typed functional polymeric spherical resin (DFP) was prepared by inverse suspension polymerization. Starting with 2,4-dihydroxybenzoic acid, phenol and formaldehyde as monomers, using liquid paraffin as dispersed phase, span 80 as dispersant, 2-methoxyethanol as porogen and HCl as catalyst. The resulted polymer resin containing salicylic acid functions showed a powerful adsorption characteristic towards boron. The boron adsorption behavior of the adsorbent was studied in batch mode by varying different parameters such as pH value, initial concentration of boron and the adsorption time under noncompetitive conditions. It was found that the sorbent always maintained high capacity in neutral and alkaline conditions. The adsorption capacity was considerably increased by an increase in the concentration of boric acid. The existence of sodium ion and calcium ion could promote the boron adsorption to some extent. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherms are applied in order to determine the efficiency of DFP used as a boron adsorbent. Results show that the equilibrium data fits Freundlich model well. Gibbs free energy (ΔG), change in enthalpy (ΔH) and change in entropy (ΔS) were calculated. The adsorption process for boron was proved to be a chemical process of an exothermic nature. Kinetics studies demonstrated that boron uptake onto DFP followed the pseudo-second order model. The load capacity was attributed to specific chemical affinity and physical adsorption.

► Salicylic-HCHO typed resin (DFP) was prepared by inverse suspension polymerization.
► The resin containing salicylic acid showed good boron adsorption capability.
► The sorbent (DFP) maintained high capacity in neutral and alkaline conditions.
► Isotherms of boron adsorption could be represented by Freundlich model reasonably.
► Boron uptake onto adsorbents (DFP) followed the pseudo-second order model.