Application of response surface modelling to economically maximize thorium (IV) adsorption

The fibrous adsorbent was synthesized by radiation-induced graft polymerisation with 2-(dimethylamino) ethyl methacrylate (DMAEMA). The fibrous grafted substrate with flexible side functional groups was used as an adsorbent to separate Th(IV) ions from an aqueous solution. The properties of the fibrous adsorbents were evaluated by attenuated total reflectance-Fourier-transform infrared spectroscopy, scanning electron microscopy, water uptake capacity and optical contact angle. The effects of adsorbent dosage, initial concentration, and reaction time on the adsorption capacity of the synthesized fibrous adsorbent were optimized using the Box-Behnken design of response surface methodology (RSM). The quadratic model showed an optimal adsorption capacity of 25.13 mg g(-1) operating at an initial concentration of 5.5 mg L-1, reaction time of 24 h, and adsorbent dosage of 0.002 g at a maximum desirability value of 1. Under these adsorption conditions, the adsorption capacity of 24.87 mg g(-1) was achieved from the experiment indicating good agreement with the predicted value. The applied optimisation procedure of incorporating RSM was effective in achieving the highest adsorption capacity using a minimum adsorbent dosage of only 0.002 g. The results indicate that the use of the fibrous adsorbent is economically promising for the separation of Th(IV) ions.