Abstract
The sorption properties of Shewanella xiamenensis biofilm formed on zeolite (mineral-organic sorbent) as a sorbent have been investigated aiming to determine its suitability for complex zinc-containing effluent treatment. The optimum conditions for metal sorption from synthetic solutions were evaluated by changing the pH, zinc concentration, temperature, and time of sorption. The highest removal of metal ions was attained at pH range 3.0–6.0 within 60–150 min of sorbent-sorbate contact. The results obtained from the equilibrium studies were described using the Langmuir, Freundlich, and Temkin models. Maximum sorption capacity of the sorbent calculated from the Langmuir model changed from 3.4 to 6.5 mg/g. High coefficient of determination values calculated for pseudo-second-order and Elovich models indicate the predominant role of chemisorption in metal removal. Gibbs energy and ∆H° values point at the spontaneous and endothermic character of the sorption. The effect of pH and biosorbent mass on Zn(II) sorption from industrial effluent with an initial Zn(II) concentration of 52.8 mg/L was tested. Maximum removal of zinc ions (85%) was achieved at pH 6.0 by applying a two-step treatment system.
Highlights
The emission of toxic elements in the environment presents a serious risk for the ecological systems and human health, due to the nonbiodegradability of metals and their tendency to accumulate in living organisms, causing different diseases [1]
The sorption properties of Shewanella xiamenensis biofilm formed on zeolite as a sorbent have been investigated aiming to determine its suitability for complex zinccontaining effluent treatment
Images obtained by the confocal laser scanning microscope showed that biofilm covered 81.6% of the surface of zeolite and it consists of bacterial cells (7.3%) and polysaccharides (74.3%), and 18.4% of the surface remained uncovered (Figure 1)
Summary
The emission of toxic elements in the environment presents a serious risk for the ecological systems and human health, due to the nonbiodegradability of metals and their tendency to accumulate in living organisms, causing different diseases [1]. Reduction of the concentration of metal ions released in the environment is a priority task in order to prevent natural water pollution [2]. Zinc, being a vital component of more than 300 metal-enzymes and metal-proteins, is considered a critical element for the growth and development of living organisms [3,4]. It performs several important functions in organisms: structural, catalytic, and protective [5]. Wastewaters containing zinc, among other toxic elements, are generated by mining activity, metallurgy and galvanizing industry, chemical industry, pharmaceutical industry, production of pigments, and pesticides [3,4,6]
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