A radioactively durable melamine-styrene based polymer: Highly efficient removal of 90Sr

Abstract

Removal of strontium has a vital importance for radioactive waste management due to its long half-life. In this context, melamine-styrene based polymer (MSBP) was synthesized and characterized by different spectrophotometric methods. Sr²⁺ ions were removed from the solution using MSBP sorbent. In this respect, adsorption of Sr²⁺ onto melamine-based polymer was studied as a part of pH, amount of adsorbent, initial Sr²⁺ concentration, contact time, temperature and particle size. Also, adsorption rate of radioactive strontium was investigated by using LSC (Liquid Scintillation Counter). The adsorption data were fitted to Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. MSBP sorbent reached maximum adsorption capacity for Sr²⁺ as 142.9 mg.g^-1. Thermodynamic parameters such as free energy (ΔG⁰), entropy (ΔS⁰) and enthalpy (ΔH⁰) of Sr²⁺ adsorption on MSBP were examined at five different temperatures of 293 K, 303 K, 313 K, 323 K and 333 K. 0 < ΔH⁰ values indicated that sorption mechanism presented endothermic feature. 0 > ΔG⁰ and 0 < ΔS⁰ revealed that Sr²⁺ adsorption on MSBP occurred spontaneously and irreversible, respectively. Pseudo first and second orders were investigated as a part of kinetic parameters and seen that pseudo second order was much more convenient for adsorption of Sr²⁺ onto MSBP.

Keywords: Adsorption; Kinetic and thermodynamic parameters; Liquid radioactive waste; Polymeric adsorbent; Strontium.