s-Triazines are broad-spectrum herbicides used to control weeds in agriculture. The most widely used s-triazine in the United States is atrazine. Accidental spills happen rarely, but such situations are best handled by immobilization of the herbicide coupled with biodegradation to ultimately destroy it. In the present study, adsorption and biodegradation were combined by designing and testing bio-silica particles comprised of tetraethoxysilane (TEOS) mixed with phenyltriethoxysilane (PTES) and s-triazine-degrading bacteria. A previously described TEOS-based method was modified to increase the adsorption affinity of hydrophobic s-triazine herbicides to the particles by partially replacing TEOS with PTES, a hydrophobic organosilane. The bacterium used was Arthrobacter aurescens TC1 that was originally isolated from an herbicide spill site. The biodegradation of s-triazines by this this bacterium is mediated by the enzymes TrzN, AtzB and AtzC, and it is reported to degrade s-triazines faster than other naturally-occurring bacteria. Bio-silica particles were prepared by the sol-gel process using different ratios of PTES and TEOS that were polymerized in the presence of A. aurescens TC1. Scanning electron microscopy revealed the presence of micron-sized spheres with attached bacteria. Electron microscopy with elemental analysis indicated that the spherical particles contained much of the phenyl groups that were presumably derived from the PTES. An optimum ratio of PTES to TEOS that simultaneously enhanced adsorption followed by biodegradation of the s-triazines was obtained. Biodegradation of the s-triazine herbicides was monitored by measuring the products of the enzymes TrzN, AtzB, and AtzC, that were hydroxyatrazine, N-isopropylammelide, and cyanuric acid, respectively. This research presents a novel in situ remediation strategy for s-triazine herbicide spills in which the material can be held in place and then degraded with a single treatment process.

Remediation of s-triazine herbicide spills via adsorption and biodegradation using hydrophobic bio-silica particles

253rd National Meeting (2017)

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