Modified cross-linked polyethylenimine for the removal of selenite from mining wastewaters

Abstract

Cross-linked branched polyethylenimine (CPEI) was sulfonated by reaction with 3-chloropropanesulfonyl chloride. The functionalized polymer was used as an adsorbent for the removal of SeO₃²⁻ from aqueous solutions, particularly mining wastewaters. The binding affinity of the synthesized polymer to abstract SeO₃^2– from synthetic solutions and wastewater samples has been assessed as well as its ability to be regenerated for reuse. The process demonstrated that sulfonated cross-linked polyethylenimine (SCPEI) exhibited good affinity to SeO₃^2– with removal efficiency up to 81%. The kinetic rates were modeled using pseudo first-order and pseudo second-order equations. The pseudo second-order equation was found to explain the adsorption kinetics most effectively implying chemisorption. The Langmuir and Freundlich isotherms were used to interpret the adsorption of SeO₃^2– onto the modified polymer. The Freundlich isotherm was found to best fit and describe the experimental data. The thermodynamic study of the adsorption process revealed high activation energies >41 kJ mole⁻¹ which confirm chemisorption as a mechanism of interaction between the adsorbate (SeO₃²⁻) and adsorbent (SCPEI).

Keywords:

• adsorption
• selenium
• sulfonated cross-linked polyethylenimine