Abstract
The biosorption behaviour of arsenic(V) and cadmium(II) ions by unmodified and five types of chemically modified Chlorella vulgaris and Spirulina platensis was investigated. The biosorption rates of As(V) and Cd(II) in binary metal solutions were lower than those in sole metal systems, which exhibited a competition between As(V) and Cd(II) ions to occupy the active sites of the adsorbent. Among the five chemical reagents, NaCl and ZnCl2 were the most suitable modifiers for improving the biosorption performance of C. vulgaris and S. platensis, respectively. The maximum biosorption capacities of As(V) and Cd(II) were: (a) 20.9 and 1.2 mg/g, respectively, for C. vulgaris modified with NaCl; (b) 24.8 and 29.4 mg/g, respectively, for S. platensis modified with ZnCl2, which were much higher than those using other chemically modifying methods. The pseudo-second-order kinetic model fitted well with all the biosorption processes. The SEM analysis revealed that the modification changed the surface morphologies and enhanced the porosity of the algae biomass. The FTIR analysis established the presence of diverse groups of compounds that were largely hydroxyl, carboxylate, amino, and amide groups on the adsorbents that contributed significantly to the upregulated biosorption. This work showed the potential application of chemically modified C. vulgaris and S. platensis biomasses to effectively remove both from water.
Highlights
Arsenic(V) and cadmium(II) are trace elements with bio-accumulative properties that pose a wide range of severe risks to human health and environmental sustainability, due to their non-degradability and persistence [1]
Due to the indiscriminate discharge of wastewater in the environment, As(V) and Cd(II) can percolate into the soil, water bodies, and plants, and enter the human body via drinking and eating [5]. Once these toxicants get into the human system, they induce a series of serious diseases such as “black foot disease” [6] and “Itai-Itai disease” [7]
The Chlorella vulgaris and Spirulina platensis that were purchased from Zhengzhou Wanbo Chemical Products Co., are dominant algae species in the south of China
Summary
Due to the indiscriminate discharge of wastewater in the environment, As(V) and Cd(II) can percolate into the soil, water bodies, and plants, and enter the human body via drinking and eating [5]. Once these toxicants get into the human system, they induce a series of serious diseases such as “black foot disease” [6] and “Itai-Itai disease” [7]. Due to the extremely toxic effects on humans even at low concentration levels, the Chinese Standard “Sanitary
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