Effects of the type and structure of modified clays on adsorption performance

The structure and adsorption performance of various clays, bentonite, montmorillonite K10 and montmorillonite KSF, were investigated in this study. The raw clays were modified by polymeric Fe/ Al species, hexadecyl- trimethylammonium (HDTMA) surfactant and a complex of Fe/Al-HDTMA. The X-ray diffraction spectra (XRD) and X-ray fluorescence spectra (XRF) were applied to analyse the structure of the raw and modified clays. Cu and phenol were selected as adsorbates for evaluating the adsorption performance of the raw and modified clays. The results indicated that the basal spacing of the bentonite and montmorillonite K10 reduced to a small extent after modification, and the crystalline configuration may be changed due to the modification process. The greater basal spacing could improve the Cu adsorption but it will be compromised by the physicochemical surface properties of the modified clays when the modifiers posses the specific complexing capacity to the inorganic/organic contaminants. When the basal spacing was smaller, however, the predominant adsorption mechanism could be chemical complexing between clay adsorbents and contaminants. In general the inorganic contaminant (e.g. Cu) tends to be adsorbed by the polymeric Fe/Al species while the organic impurity (e.g. phenol) will be preferably captured by the HDTMA modifier.