Development of sorption technology for the cleanup of pesticide contaminated wastewater

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Virginia Tech

The use of pesticides in agricultural production has led to the contamination of surface and groundwater. There is a need for simple, on site wastewater cleanup procedures to minimize pollution caused by spills and improper disposal of pesticide wastes by pesticide applicators and farmers. Sorption technology may prove a viable alternative to biological wastewater treatment. Properties of the ideal sorbent are (i) a high capacity for the contaminant, (iii) inexpensive and/or regenerable, and (ili) easy to dispose of after use. Our objective was to evaluate Filtrasorb 400 (activated carbon), Ambersorb adsorbents, and thiol derivatized cellulose beads for pesticide adsorption. Also, the use of solid state fermentation as a means of final disposal of pesticide sorbed onto a lignocellulosic matrix was investigated. Adsorptive capacities of Ambersorb adsorbent 572 for dicamba as Banvel 4L and metolachlor as Dual 8E under flow through conditions were three times higher than adsorptive capacities of Filtrasorb 400. Better performance of Ambersorb adsorbents under flow through conditions was likely the result of faster mass transfer kinetics caused by a more favorable pore size distribution in Ambersorb adsorbents. Ambersorb adsorbents are easily regenerable, with a slight loss of adsorptive capacity, using methanol. Thiol derivatized cellulose beads were synthesized using a novel method. Carbonyldiimidazole activated cellulose beads were reacted with aminoethanethiol to yield thiol contents of up to 160 μmoles/mL beads. Sorption of metolachlor by ethanethiol-cellulose beads was primarily the result of chemisorption, although some physisorption may occur. Chemisorption of metolachlor by ethanethiol-cellulose beads is the result of a nucleophilic substitution reaction, immobilizing metolachlor. Chemisorption increased at elevated temperatures and pH. Sorptive capacity of ethanethiol-cellulose beads for metolachlor in batch studies was similar to Ambersorb adsorbent 572. Ethanethiol-cellulose beads may prove a useful sorbent for contaminants containing electrophilic centers, such as atrazine, simazine, alachlor, and metolachlor. Solid state fermentation of carbofuran in a peat matrix showed that a large amount of carbofuran residues became incorporated into organic matter. The formation of carbofuran-7-phenol was necessary for incorporation to occur. Carbofuran-7-phenol likely was incorporated through peroxidase catalyzed oxidative coupling reactions. Solid state fermentation of contaminants that can undergo oxidative coupling, may prove an effective detoxification method.