Paraquat removal by free and immobilized cells of Pseudomonas putida on corn cob biochar

Abstract

Paraquat (1,1′-Dimethyl-4,4′-bipyridinium dichloride) is a non-selective contact herbicide with highly toxic and soluble in water. This study aims to compare paraquat removal by free and immobilized cells of Pseudomonas putida on corn cob biochar using three methods: the adsorption method, the covalent bonding method and the entrapment method in aqueous solution. The characteristics of bacteria and biochar were studied using Scanning Electron Microscope (SEM), Brunauer Emmett Teller (BET). The results shown that kinetic and isotherm data were followed the Pseudo-second-order and Langmuir models. The covalent bonding method was the best immobilization cell method with PQ removal at 4.21 mg/g. Moreover, the PQ adsorption capacity of living cells (3.15 mg/g) is higher than the PQ adsorption capacity of dying cells (2.41 (mg/g). The biodegradation pathways of paraquat were elucidated as the intermediate products have been identifield as 4,4-bipyridyl (m/z 155) and malic acid (m/z 133). The study encircles paraquat removal from contaminated environments through biochar adsorption and microbial degradation.

Keywords

• Biochar
• Bacteria
• Paraquat
• Adsorption
• Biodegradation
• Immobilization