Condition Optimization, Free Energy Considerations and Isothermal Studies of Zinc Sorption by the Cyanobacterium Anabaena variabilis MEGCH1

Omega Lasienhun Diengdoh, Balakyntiewshisha Lyngdoh Kynshi, Meguovilie Sachu, Mayashree B. Syiem

Abstract: Heavy metal contamination has long been recognized as a significant public health threat, especially in developing nations, and their toxicity consequences are well realized. Traditional remediation methods are either expensive or produce hazardous by-products derogatory to both physical and biological environments. Microbial biosorption has proven to be an effective method of removing heavy metals from contaminated water. The cyanobacterium Anabaena variabilis MEGCH1 was isolated from a coal mine region of Chiehruphi, Jaintia Hills, Meghalaya, and its ability to remove Zn2+ from aqueous solutions was investigated in this study. Zn2+ binding on the cyanobacterial biomass was confirmed by SEM-EDX, and FTIR analysis indicated several negatively charged functional groups on the cell surface that assisted in metal binding. Zn2+ biosorption was impacted by a number of experimental variables, including pH, temperature, inoculum age and size, shaking rate, and contact time. The sorption percentage was dramatically increased when the experimental circumstances were optimized. Thermodynamic analyses demonstrated that the biosorption process was energetically feasible, with a negative free energy change at various temperatures [-6.703 kJ/mol at 308 K (35?C), -6.595 kJ/mol at 303 K (30?C) and -6.486 kJ/mol at 298 K (25?C)]. According to the isotherm modeling research, the Freundlich isotherm (R2 value- 0.9559) matched better than the Langmuir isotherm (R2 value- 0.9427), implying that Zn2+ binding to the organism biomass was a multilayer sorption process. In addition, various other thermodynamic and isothermal parameters indicate favorable binding of Zn2+ on the biomass surface. Further, the organism also revealed a considerable tolerance toward Zn2+ exposure.

Keywords: Anabaena variabilis MEGCH1, zinc sequestration, SEM-EDX and FTIR, Thermodynamics, Freundlich and Langmuir isotherms