Treatment of Waters Containing the Thiocarbamate Herbicide Molinate through an Adsorption/Bio-Regeneration System using a Low-Cost Adsorbent

Abstract

The feasibility of using recycled granular tire rubber (GTR) to remove molinate from contaminated water bodies was evaluated in this study. Adsorption equilibrium data was well described by a linear isotherm, and the adsorption was completely reversible. Breakthrough curves showed column efficiencies of approximately 40%, based on total capacity, and complete bed regeneration was achieved using clean water. The effluent from the regeneration step was successfully decontaminated using a defined bacterial mixed culture, capable of molinate mineralization. It was shown that this treated water can be used for regenerating a subsequently saturated bed. The GTR adsorbent showed two important features: complete reversibility towards molinate adsorption and stability along successive adsorption/bio-regeneration cycles. Common adsorbents, such as activated carbons and resins, loose performance very quickly under the same conditions, due to irreversible adsorption. Abbreviations and NotationsConcentration of molinate in the column inlet stream (mg dm −3 ) C eq Molinate concentration in the liquid phase, in equilibrium with a concentration q eq of molinate in the adsorbed phase (mg g −1 ) L bBed length (cm) m ads Mass of adsorbent in the bed (g) Q Flow rate (cm 3 s −1 ) q Molinate adsorbed concentration (mg g −1 ) q 0 Molinate adsorbed concentration, in equilibrium with a concentration C 0 of molinate in the liquid phase (mg g −1 ) q bt Bed capacity at breakthrough (mg g −1 ) q bed Total bed capacity based on breakthrough data (mg g −1 ) q eq Molinate adsorbed concentration, in equilibrium with a concentration C eq of molinate in the liquid phase (mg g −1 ) q isot Total bed capacity based on adsorption equilibrium data (mg g −1 ) S Column cross-section (cm 2 ) t Time (s) t bt Breakthrough time (h) Water Air Soil Pollut (

Bacterial diversity and bioaugmentation in floodwater of a paddy field in the presence of the herbicide molinate

“…In our study, this was not a limitation, as in previous work we established a fivemember bacterial mixed culture (named DC) with constitutive capacity to mineralize molinate (Barreiros et al 2003(Barreiros et al , 2008. Culture DC is able to promote molinate degradation under a wide array of abiotic conditions (Carvalho et al 2010;Coelho et al 2006;Silva et al 2004b), without the accumulation of any toxic metabolites (Correia et al 2006). Thus, in the current study we aimed at assessing the ability of culture DC to remove the pesticide from floodwaters, and inferring at the possible perturbations this culture could induce in the autochthonous community.…”

Automotive Wastes

“…The feasibility of using recycled GTR to remove molinate from contaminated water bodies was evaluated (Carvalho et al, 2010). It was found that GTR can be used in a cost-effective treatment system in which molinate is removed from polluted water by adsorption, and the spent adsorbent is regenerated with fresh water.…”