Abstract
The present study investigated the biosorption capacity of live and dead cells of a novel Bacillus strain for chromium. The optimum biosorption condition was evaluated in various analytical parameters, including initial concentration of chromium, pH, and contact time. The Langmuir isotherm model showed an enhanced fit to the equilibrium data. Live and dead biomasses followed the monolayer biosorption of the active surface sites. The maximum biosorption capacity was 20.35 mg/g at 25 °C, with pH 3 and contact time of 50 min. Strain 139SI was an excellent host to the hexavalent chromium. The biosorption kinetics of chromium in the dead and live cells of Bacillus salmalaya (B. salmalaya) 139SI followed the pseudo second-order mechanism. Scanning electron microscopy and fourier transform infrared indicated significant influence of the dead cells on the biosorption of chromium based on cell morphological changes. Approximately 92% and 70% desorption efficiencies were achieved using dead and live cells, respectively. These findings demonstrated the high sorption capacity of dead biomasses of B. salmalaya 139SI in the biosorption process. Thermodynamic evaluation (ΔG0, ΔH0, and ΔS0) indicated that the mechanism of Cr(VI) adsorption is endothermic; that is, chemisorption. Results indicated that chromium accumulation occurred in the cell wall of B. salmalaya 139SI rather than intracellular accumulation.
Highlights
The bioaccumulation tendency and toxicity of the present heavy metals, such as zinc, mercury, lead, chromium, and cadmium, pose a major threat to the environment [1]
The surface morphology of dead cells analyzed through scanning electron microscopy (SEM) was illustrated before and after the adsorption process (Figure 6A,B)
This phenomenon may be attributed to the coverage of the cell surface with chromium ions, which looked like fat, spongy, and plumped
Summary
The bioaccumulation tendency and toxicity of the present heavy metals, such as zinc, mercury, lead, chromium, and cadmium, pose a major threat to the environment [1]. Chromium is one of the most important hazardous heavy metals in wastewater; this element does not degrade and is highly resistant to oxidation even at high temperatures [2]. Chromium is widely distributed in the environment, among textile industries, petroleum refining, and chemical and electronic manufacturing, as well as agriculture and mining activitie. Chromium is released into the environment through leaching of toxic ingredients, improper disposal practices, leakage, and poor storage tanks, resulting in contaminated ground water and soil at production sites. Chromium pollution poses a serious threat to fish, aquatic biodiversity, and human health. In accordance with the drinking water guidelines, the maximum recommended limit for total Cr is 0.05 mg/L [3]
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