Enhanced paraquat removal from contaminated water using cell-immobilized biochar

The efficient performance of cell-immobilized biochar in removing paraquat (PQ) from contaminated water is described in this work. Pseudomonas putida was immobilized onto coconut fiber-derived biochar (BC) using the adsorption method and the covalent binding method. The FTIR spectrum analysis revealed that the main adsorption mechanism of bacteria and BC relates to the interaction between cell surface proteins and the functional group on biochar. The pseudo-second-order model could explain the kinetics of simultaneous adsorption and biodegradation of cell immobilization on BC. Cell-immobilized biochar using the covalent bonding method and adsorption method exhibited superior PQ removal capacity with 30–35% increases in efficiency compared with simple biochar. After 48 h using cell-immobilized biochar, the PQ was transformed to 4,4-bipyridyl and malic acid as detected by GC/MS. From the PQ kinetic removal rate and bacterial retention, the covalent binding method with 16.79 mg/g paraquat adsorption capacity and 0.626 g/mg/h kinetic rate constant is considered as the best cell-immobilization method for the immobilization technique. The cell immobilization on biochar using both the adsorption method and the covalent binding method can support bacteria to degrade PQ into small molecular substances in water treatment processes.