Organovermiculite as regenerable nanostructured adsorbent for treatment of heavily polluted waste water from coke industry

Abstract

Organically modified vermiculites can be used as nanostructured adsorbents of organic compounds from waters or gaseous phases similarly as organically modified smectites or bentonites. There is a large amount of research data focused on adsorption properties of organoclays, however only a little information is about their post-sorption treatment. This work is focused on study of two possible ways of subsequent processing of organovermiculite after its use as sorbent for heavily polluted waste water. At first, the vermiculite modified with hexadecylpyridinium ions was used in batch static sorption against phenol ammonium water from the coke industry to get highly contaminated sorption material, especially containing organic hydrocarbons and their derivatives. The sorbent is known to have excellent sorption properties; however ecotoxicological characteristics of original material showed that sorbent had hazardous properties even before its utilization. For that reason, it was necessary to design a post-sorption treatment. Two possible methods of treatment were investigated, specifically solvent treatment (with dichloromethane) and thermal treatment (thermodesorption) at temperatures of 300 and 1100 degrees C, respectively. The treated materials were studied using infrared spectroscopy, X-ray diffraction and carbon phase analyses. The solvent treatment confirmed that it is possible to reuse modified vermiculite as adsorbent several times, although adsorption capacity after each extraction decreases. The thermal treatment at 300 degrees C was not sufficient to remove all organic compounds from the vermiculite structure; however at 1100 degrees C the only presence of magnesium silicate, magnesium aluminate and ferric oxide confirmed the formation of an inert material convenient for an environmentally harmless disposal of used adsorbent.