Abstract
The biosorption of hexavalent chromium from aqueous solutions by Opuntia cladodes and ectodermis from cactus fruits was investigated. Both types of biomass are considered low-cost, natural, and ecofriendly biosorbents. Batch experiments were carried out to determine Cr(VI) biosorption capacity and the efficiency of the biosorption process under different pH, initial Cr(VI) concentration, and sorbent dosage. The biosorption of Cr(VI) by Opuntia biomass was highly pH dependent, favoring higher metal uptake at low pH. The higher biosorption capacity was exhibited at pH 2. The optimal conditions were obtained at a sorbent dosage of 1 g L−1 and initial metal concentration of 10 mg L−1. Biosorption kinetic data were properly fitted with the pseudo-second-order kinetic model. The rate constant, the initial biosorption rate, and the equilibrium biosorption capacity were determined. The experimental equilibrium data obtained were analyzed using two-parameter isotherm models (Langmuir, Freundlich, and Temkin). The Langmuir maximum monolayer biosorption capacity (q max) was 18.5 mg g−1 for cladodes and 16.4 mg g−1 for ectodermis. The results suggest that Opuntia biomass could be considered a promising low-cost biosorbent for the ecofriendly removal of Cr(VI) from aqueous systems.
Highlights
The increased industrial activities, indiscriminate use of organic and inorganic fertilizers and pesticides, and disposal of industrial effluents enhance the possibility of pollution and toxicity of heavy metals in environment
This paper presents the use of Opuntia biomass as potential biosorbent for hexavalent chromium removal from aqueous solution
Experiments over a range of pH values (2–7) with 10 mg/L of Cr(VI) concentration in solution in Figure 2 reveal that biosorption uptake of Cr(VI) with Opuntia biomass is clearly pH-dependent
Summary
The increased industrial activities, indiscriminate use of organic and inorganic fertilizers and pesticides, and disposal of industrial effluents enhance the possibility of pollution and toxicity of heavy metals in environment. Due to their extended persistence in biological systems and tendency to bioaccumulate, the contamination of water by toxic heavy metals is a worldwide environmental hazard [1, 2]. Hexavalent chromium is known to have 100-fold more toxicity than trivalent chromium because of its higher water solubility, mobility, and oxidizing power It can act as carcinogen, mutagen, and teratogen in biological systems [8, 9]
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