Slow released nutrient-immobilized biochar: A novel permeable reactive barrier filler for Cr(VI) removal

A novel permeable reactive barrier (PRB) filler, slow released nutrient-immobilized biochar (SRN-IB) was prepared to remove Cr(VI) from aqueous solution. Morganella morganii subsp. was selected as the Cr(VI) reducing strain and the cultural condition was optimized. The highest removal rate was obtained with 4 g/L of glucose, 8 g/L of yeast extract and pH of 7-8. The removal kinetic fitting demonstrated that M. morganii subsp. could remove Cr(VI) from solution more effectively than the traditional PRB filler, zero valent iron. M. morganii subsp. was immobilized on peanut shell biochar through circulatory fixation to prepare IB. SRN was obtained via capturing glucose and yeast extract in agar based on the optimization result to supply nutrition to the strains on biochar. Five ratios of SRN and IB was optimized with column experiment and the best value was 1:1. The breakthrough time and maximum adsorption ability of the SRN-IB bed were also studied with Logistic and Thomas model, which were increased with running time and significantly higher than biochar. High throughput sequencing analysis confirmed that M. morganii subsp. was immobilized on the biochar and became the dominant bacterium in the Cr(VI) treatment process. Furthermore XPS analysis was carried out to reveal the removal mechanism which includes adsorption and reduction of Cr(VI) to Cr(III). (C) 2019 Elsevier B.V. All rights reserved.