Augmented complete mineralization of glyphosate in wastewater via microbial degradation post CWAO over supported Fe-CNF

Abstract

Glyphosate, a widely used post emergence broad spectrum herbicide, recognized for its harmful impact on the environment, is sequentially mineralized in a two-step process: catalytic wet air oxidation (cWAO) followed by microbial degradation. Iron nanoparticle (Fe NP)-tipped carbon nanofibers (CNFs) supported over activated carbon beads (ACBs) are used as a cWAO catalyst. Fe-CNF/ACB with a high specific surface area (~296 m2/g), high thermal stability (25–1100 °C) and an increased exposure of the Fe NPs to the surrounding water causes ~70% degradation of the aqueous glyphosate (100 mg/L) in 2 h at 220 °C, 25 bar-air pressure, and 0.75 g/L of catalyst-dose. The residual glyphosate is, however, completely mineralized in the next 2 h at 37 °C, with 100% reduction in total organic carbon content, using a bacterium isolated from the industrial wastewater. The bacterium is phylogenetically identified as Providencia vermicola via 16s rRNA analysis. Non-toxicity of Fe-CNF/ACB towards the isolated bacterial strain eases the sequential remediation process by circumventing the necessity of removing the spent catalyst from the reaction mixture before switching over to microbial degradation. The present approach based on cWAO followed by microbial degradation is indicated to be efficient for the degradation and mineralization of toxic, biorefractory pollutants in wastewater.