Thermogravimetric studies of benzoylthiourea-modified MCM-41 after adsorption of mercury ions from aqueous solutions

Abstract

High-resolution thermogravimetry (HR TG) was used to study the adsorption of mercury(II) ions by modified MCM-41 material and regeneration of the loaded adsorbent with mercury ions by using different eluents. The weight change curves were measured for MCM-41 samples modified with 1-benzoyl-3-propylthiourea ligand loaded with mercury ions. The differential thermogravimetric (DTG) curves were analyzed to investigate the adsorption of mercury ions by the aforementioned multifunctional ligand and to monitor the decomposition of the metal-ligand complexes. A series of experiments performed for different Hg(2+):ligand ratios allowed us to correlate the adsorption data for mercury ions measured by means of UV spectrophotometry with those obtained by HR TG analysis. The DTG results provided additional information about mercury-ligand interactions as well as the thermal stability of mercury-ligand complexes. This study shows that HR TG is a very attractive technique for studying the adsorption of mercury ions on modified nanoporous silicas and monitoring their regeneration. Since the samples used are small, this method seems to be promising for studying adsorption systems of environmental significance.