The potential of thermally treated organobentonites to adsorb organic compounds from water

The effects of thermal treatment of selected quaternary ammonium-exchanged bentonites formed with n-hexadecyltrimethylammonium, benzyltrimethylammonium and tetraethylammonium on their adsorption of a series of organic compounds from water were examined. The examined compounds were phenanthrene, atrazine, phenol, and m-nitrophenol, which differ substantially in their molecular structures and are capable of various types of interactions with adsorbents and solvent. The thermal pretreatment of organobentonites and of original bentonite involved 2 h of heating in air at 150, 250, 360 and 420 °C. Heating of organoclays at 150 °C did not cause obvious changes in the structures of the adsorbents but might have enhanced their interactions with organic adsorbates. The extent of the enhancement differed among the adsorbates and could reflect their differing abilities to compete with water molecules for adsorption sites on organoclays. The loss of organic carbon and significant changes in the organoclay chemical structures caused by preheating in air at higher temperatures did not result in significant loss of the organoclay potential to adsorb organic compounds present in the aqueous solution.