Boron removal from aqueous solutions by a polyethylenimine-epichlorohydrin resin

The use of a polyethylenimine–epichlorohydrin resin for the boron removal from aqueous solutions (boron concentration: 100–5000 mg L -1 ) of non-adjusted and pre-adjusted pH (pH nat , pH init 8.0, 9.0 and 10.0) aqueous solutions was investigated using a batch technique. The boron concentration in the solutions after sorption was determined photometrically. The results indi­cated that the pH-dependent boron uptake was related to the protonation/depro­tonation of the surface functional groups of the resin and to the boron speciation in solutions of different pH values. The maximum boron sorption capacity observed in solutions of pH 9.0 was 55 mg g -1 exceeding the majority of other commercial or alternative sorbents. Five empirical adsorption equat­ions (Freundlich, Langmuir, Redlich–Peterson, Langmuir–Freundlich and Toth) were applied to the modelling of the boron adsorption equilibrium. The modelling results identified the homogenous boron sorption from acidic and heterogeneous from alkaline solutions. At alkaline pH, the system non-ideality can originate either from the different binding mechanism or from the com­pet­itive sorption of different boron species. The homogenous type boron sorption from acidic solutions was further confirmed by kinetic studies.