Biosorption of cadmium by growing bacteria immobilized on the three magnetic biochars derived from rice straw (MRSB-pellet), sewage sludge (MSSB-pellet), and chicken manure (MCMB-pellet) was investigated, respectively. Total biosorption capacity of the pellets was tested under varying range of pH, culture time, and initial Cd 2+ concentration. The maximum biosorption capacity of 93.02 mg/g was obtained with MRSB-pellet, followed by MSSB-pellet (68.02 mg/g) and MCMB-pellet (63.95 mg/g). The biosorption by these immobilized bacterial pellets was more effective than free bacteria, this enhancement could be the result of simultaneous adsorption and bioaccumulation, mainly resulting from magnetic biochar carrier and active bacteria, respectively. The biosorption process by immobilized pellets was primarily driven by ion-exchange and complexation, which jointly contributed of 73.56% (MRSBpellet) to 78.62% (MSSB-pellet) the total adsorption, while the mechanisms of chemical precipitation and physical adsorption could averagely contribute 6.91% (MSSB-pellet) and 11.24% (MRSB-pellet), respectively. Intracellular accumulation was comparably tiny among these mechanisms accounting for 4.30-5.92% of total biosorption, in turn, it would maintain intracellular Cd 2+ concentration below a toxic threshold to promote cell growth. These suggested that magnetic biochar immobilized bacteria, particularly MRSB-pellet could be used as an effective biosorbent to remove the Cd 2+ from the growth medium. This study further deepened our understanding of biosorption process by microorganism immobilized onto magnetic biochar for the metals removal.

No abstract

Biosorption of cadmium by growing bacteria immobilized on the three magnetic biochars derived from rice straw (MRSB-pellet), sewage sludge (MSSB-pellet), and chicken manure (MCMB-pellet) was investigated, respectively. Total biosorption capacity of the pellets was tested under varying range of pH, culture time, and initial Cd 2+ concentration. The maximum biosorption capacity of 93.02 mg/g was obtained with MRSB-pellet, followed by MSSB-pellet (68.02 mg/g) and MCMB-pellet (63.95 mg/g). The biosorption by these immobilized bacterial pellets was more effective than free bacteria, this enhancement could be the result of simultaneous adsorption and bioaccumulation, mainly resulting from magnetic biochar carrier and active bacteria, respectively. The biosorption process by immobilized pellets was primarily driven by ion-exchange and complexation, which jointly contributed of 73.56% (MRSB-pellet) to 78.62% (MSSB-pellet) the total adsorption, while the mechanisms of chemical precipitation and physical adsorption could averagely contribute 6.91% (MSSB-pellet) and 11.24% (MRSB-pellet), respectively. Intracellular accumulation was comparably tiny among these mechanisms accounting for 4.30-5.92% of total biosorption, in turn, it would maintain intracellular Cd 2+ concentration below a toxic threshold to promote cell growth. These suggested that magnetic biochar immobilized bacteria, particularly MRSB-pellet could be used as an effective biosorbent to remove the Cd 2+ from the growth medium. This study further deepened our understanding of biosorption process by microorganism immobilized onto magnetic biochar for the metals removal.