Modelling and Kinetics of Cd(II) Biosorption onto Inactive Instant Dry Baker's Yeast

This study presents the modeling and kinetics of Cd(II) High concentrations of toxic heavy metals are being released into the environment from industry activities endangering natural ecosystems and human health worldwide. Moreover, the heavy metals have high mobility in aqueous systems and may present high toxicity Compared with the classical methods used for heavy metals decontamination from wastewaters (i.e. chemical precipitation, ion exchange, solvent extraction, electrochemical technologies, membrane technologies, reverse osmosis, filtration, evaporation, etc) that have several drawbacks (i.e.: incomplete metal removal, high operating costs, high reagent and/or energy requirements, etc.), biosorption is considered a cost-effective, eco-friendly and easy to operate alternative technology It is well known that biomaterials like, bacteria, fungi, yeast, algae, food industry/agricultural waste, plants, animal origin by-products etc. can remove toxic metals and radionuclides, but can also recover precious metals and light metals from aqueous solutions to various extents Although several research groups investigated heavy metal removal by diverse S. cerevisiae types (lab cultivated yeasts, waste from food industry, immobilized yeast, magnetically/ chemically/ thermally modified yeast, commercial baker and brewer yeasts subsequently lab cultivated, fresh/ compressed baker yeast, dry baker yeast, etc.), the biosorption mechanism is not fully understood The aim of this study was to investigate the modeling and kinetics of Cd(II) biosorption (from synthetic aqueous solutions) onto the inactive instant dry baker yeast biomass. The biosorption equilibrium and the nature of the adsorption process (as chemical and/or physical) were evaluated by means of Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models. Experimental part Biosorbent preparation Commercial instant dry baker yeast (S. cerevisiae) purchased from local commercial company was prepared as inactive biomass by oven drying at 105 o C for 24 h Reagents Cadmium stock solution of 1000 mg L -1 was prepared by dissolving 3CdSO 4 · 8H 2 O of analytical reagent grade (Merck, Germany) into distilled water. Cadmium test solutions of different concentrations Equipment The pH values were measured with an Orion 290 A pHmeter. The batch biosorption experiments were conducted by using a Heildorph Vibramax 100 shaker. Cd(II) equilibrium concentrations in liquid phase wer