Effect of pH on the binding mechanisms in biosorption of Reactive Orange 16 by Corynebacterium glutamicum.

Binding mechanisms of Reactive Orange 16 (RO 16) by the protonated waste biomass of Corynebacterium glutamicum were investigated. The solution pH was found to strongly influence the uptake of RO 16 by C. glutamicum. The biosorption of the dye was reversible at pH <7 but irreversible under basic pH conditions. At acidic pH, the electrostatic interaction was found to be a major binding mechanism. The maximum sorption capacities of the biomass were evaluated to be 156.6+/-6.2 and 64.0+/-2.4 mg/g at pH 2 and 4, respectively. The various forms of RO 16 molecule in aqueous solution were identified by LC/MS to study the hydrolysis of RO 16. FTIR and XPS analyses showed the chemical bonding between biomass surface and dye molecules under basic pH conditions, providing insight to the irreversible binding mechanism.