Influence of thermally modified palygorskite on the viability of polycyclic aromatic hydrocarbon-degrading bacteria

Thermal activation of palygorskite is considered as a simple and cost-effective method for modifying its structural and surface properties, which can be congenial for the adsorptive removal of environmental contaminants. However, for a more efficient removal of organic contaminants like polycyclic aromatic hydrocarbons (PAH), clay-microbial synergy combining both adsorption and biodegradation is an emerging strategy. In this study, we investigated the compatibility of heat treated palygorskite products (100-900 degrees C) with a PAH-degrading soil-bacterium Burkholderia sartisoli. The mineralogical and physico-chemical properties were characterised in detail, and the bacterial adhesion to the substrate and their growth were observed in relation to these properties. The major variation in the cation exchange capacity (CEC), surface area, water content and the elemental dissolution in the aqueous medium occurred in the palygorskite products heated at extreme temperature (700-900 degrees C). These changes significantly influenced the bacterial growth and attachment. The maximum viability was imparted by the palygorskite product obtained at 400 degrees C. Dissolution of Al from products heated above 500 degrees C also posed inhibitory effect on bacterial growth in the aqueous media. This study provided valuable information about the mechanisms of bacterial viability as affected by modified clay minerals, which is important for developing a novel clay-modulated-bioremediation technology. (C) 2016 Elsevier B.V. All rights reserved.