Retention of samarium ions from aqueous solutions by poly(acrylic acid)-enhanced ultrafiltration

Abstract

Rare earth elements (REE) are widely used in variety of commercial applications, which results in public exposure to them, and it is a matter of concern. Recent studies have demonstrated that the toxicity of (REE) as a group is similar to the toxicity of heavy metals. Many methods were used to remove lanthanides from wastewaters generated from their commercial use. Samarium, a REE, which may be removed from the aqueous solution by polyelectrolyte-enhanced ultrafiltration process, was investigated using poly(acrylic acid) (PAA) with average molecular weight 100,000 Da. The ultrafiltration studies were carried out using a tangential cell system. Polyethersulfone membrane with molecular weight cutoff of 5,000 Da and an effective filtration area of 50 cm2 were used (PES-5). Several parameters, such as transmembrane pressure, PAA concentrations, and pH, have been optimized to improve the retention of the Sm(III) ions. Results shows that the permeate flux increases linearly with increasing transmembrane pressure. It can be seen that with the increase in the concentration of PAA, the Sm(III) ions retention also increases until reaching 80%. A better retention was observed at 2 × 10−4 mol L−1 PAA concentration and 3 bar transmembrane pressure. The pH effect study on samarium ions revealed a maximum retention around 70% for pH 5.