Optimization of synthesis conditions for preparation of radiation grafted polymeric fibers and process variables of adsorption with response surface methodology

Abstract

Radiation-grafted polymeric adsorbents have a high adsorption capacity in purifying effluents from heavy metals. This study investigated adsorption conditions for removing uranium from aqueous nitrate solution using radiation-grafted polymeric adsorbent (PP-g-(PAAc-co-PAm)). The modified fiber (polypropylene) was synthesized with acrylic amide and acrylic acid monomers. The central composite design approach in two stages was used to determine optimal conditions. In the first stage, the effects of three factors such as acrylic amide concentration, sulfuric acid concentration and dose of gamma-ray on adsorbent synthesis were investigated to prepare an appropriate adsorbent. The impacts of three parameters, including the initial aqueous pH, uranium ion concentration, and equilibrium time on adsorption conditions, were studied using a central composite approach in the second stage. The optimum conditions for sulfuric acid concentration, acrylic amide concentration, the dose of gamma-ray, initial aqueous pH, uranium concentration, and time were optimized equally to 59.7% (v/v), 0.08 M, 20 kGy, 7, 80 ppm, and 3 h, respectively. The uranium adsorption yields equal to 62.04% achieved from the quadratic equation agreed with the experimental value equal to 59.07%. The uranium adsorption was attained to 16.79 mg/g with a grafting percentage of 30.58% under the optimum conditions. Kinetics and equilibrium isotherms described experimental data following pseudo-second-order and Langmuir models. Finally, the results showed that the radiation-grafted polymeric adsorbents are effective in uranium uptake from effluents.