ROLE OF EXTRACELLULAR POLYMERIC SUBSTANCES IN ADSORPTIVE BINDING OF HEAVY METALS ON TO MICROSYSTISAERUGINOSA

The role of extracellular polymeric substances (EPS) from the cyanobacterial species Microcystis aeruginosa in cadmium, copper, lead, and zinc biosorption is reported in the present work. The biosorption capacity of whole biomass ( Microcystis aeruginosa) and biomass without EPS was investigated by optimizing different experimental conditions like biomass dose, time of contact, pH of suspension, and initial heavy metal ion concentration. FTIR spectra showed that different functional groups like carboxyl, hydroxyl and amide groups are present in biomass with and without EPS which scavenge heavy metals. The Langmuir model was found to be most suitable fit for the biosorption data, with Cd, Cu, Pb, and Zn ions showing maximum removal capacity of 125.0, 71.42, 90.90, and 56.0 mg per gram of whole biomass and 62.50, 50.0, 58.33, and 48.33 mg per gram of biomass without EPS respectively. The Pseudo 2(nd )order kinetic model explains the biosorption data very well for all heavy metals with regression coefficient values of 0.99-1.0 for both the biomasses. The whole biomass intact with EPS showed a greater potential to scavenge heavy metals than the biomass without it. Thus, the role of EPS was demonstrated to be very essential in heavy metal adsorption onto M. aeruginosa biomass.