Benzoylthiourea-modified MCM-48 mesoporous silica for mercury(II) adsorption from aqueous solutions

Benzoylthiourea-modified mesoporous silica with cubic structure, MCM-48, was studied as a potential adsorbent for mercury ions from aqueous solutions. The mesopore surface of MCM-48 was decorated with a multifunctional ligand, namely 1-benzoyl-3-propylthiourea, via two-step post-synthesis modification. Grafting the organic moiety inside of the MCM-48 mesopores afforded material with high surface area of 505 m2/g, accessible pores of 2.8 nm, and ligand coverage of 1.55 mmol/g. The specific three-dimensional structure of MCM-48 and the choice of the attached ligand allowed obtaining the maximum adsorption capacity as high as 6.7 mmol Hg2+ per gram of the adsorbent. High adsorption performance of the regenerated material for Hg2+ ions, reflected by only insignificant decrease in its initial adsorption capacity, was observed. About 90% of the initial adsorption capacity was restored after regeneration of the adsorbent with 10% thiourea in 0.05 M HCl in the concentration range of 0–3 mmol Hg2+/l.