Enhanced Removal of BTEX, TCE, and cis-DCE Mixture using Pseudomonas sp. Immobilized in Scrap Tires

Scrap tires and Pseudomonas sp. isolated from a gasoline contaminated soil were used for the enhanced removal of a mixture of BTEX (benzene, toluene, ethylbenzene, and xylenes), cis-1,2-dichloroethylene (cis-DCE), and trichloroethylene (TCE) from aqueous solutions. Adsorption of these volatile organic compounds (VOCs) onto tires was greatly affected by contact time and the maximum adsorption was reached within 1 day. The Freundlich isotherm model best fitted the experimental data, based on its relatively high values of correlation coefficients (0.886-0.990). The constant 1/n was determined by the slopes of each plot, and the obtained values for BTEX compounds (0.19-0.49) and cis-DCE / TCE (2.41 / 1.32) suggested favourable and unfavourable removals, respectively. The adsorptive capacity (Kf) was obtained from the intercepts (23.12 - 2.24 x 10-4 mg g-1) and the adsorption affinity followed the order of toluene> benzene> m,p-xylene> o-xylene> ethylbenzene> TCE> cis-DCE. The scrap tires also showed a good capacity of enhancing the bioremoval process through immobilization (attachment) of microorganisms. For the BTEX removal, up to 95% of benzene, toluene, ethylbenzene, and xylenes were removed after 5 days when 80 mg g-1 tires together with microorganisms were employed. TCE and cis-DCE were also removed 75 and 60%. Results show that the scrap tire is a good candidate to enhance the removal of such VOCs as BTEX, cis-DCE, and TCE from liquids, due to its remarkable adsorption properties as well as the capability to attach microorganisms.