Abstract
The present work describes the study of mercury Hg(II) and lead Pb(II) removal in single and binary component systems into easily prepared chitosan-iron(III) bio-composite beads. Scanning electron microscopy and energy-dispersive X-ray (SEM-EDX) analysis, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and point of zero charge (pHpzc) analysis were carried out. The experimental set covered pH study, single and competitive equilibrium, kinetics, chloride and sulfate effects as well as sorption–desorption cycles. In single systems, the Langmuir nonlinear model fitted the experimental data better than the Freundlich and Sips equations. The sorbent material has more affinity to Hg(II) rather than Pb(II) ions, the maximum sorption capacities were 1.8 mmol·g−1 and 0.56 mmol·g−1 for Hg(II) and Pb(II), respectively. The binary systems data were adjusted with competitive Langmuir isotherm model. The presence of sulfate ions in the multicomponent system [Hg(II)-Pb(II)] had a lesser impact on the sorption efficiency than did chloride ions, however, the presence of chloride ions improves the selectivity towards Hg(II) ions. The bio-based material showed good recovery performance of metal ions along three sorption–desorption cycles.
Highlights
Heavy metals are potentially toxic to humans; mercury and lead are two of the most harmful metals present in wastewater [1], some studies label these metals as relevant and very toxic elements [2,3]
Chloride(II) nitrate (HgCl2, 99%, (Probus, Barcelona, Spain), lead(II) nitrate (Pb(NO3 )2 ; 98%, Panreac, Barcelona, Spain), chitosan (Aber Technologies, Lannilis, France, MW = 125,000 g·mol−1 was determined by gel permeation chromatography technique, and the degree of acetylation DA = 0.13 was obtained by Fourier transform infrared spectroscopy [16,17]), acetic acid (CH3 COOH, 99.7%, Panreac, Barcelona, Spain), hydrochloric acid
Neat chitosan was dissolved in acetic acid (1% w/w)
Summary
Heavy metals are potentially toxic to humans; mercury and lead are two of the most harmful metals present in wastewater [1], some studies label these metals as relevant and very toxic elements [2,3]. The presence of these metals, in water resources is reported [4,5], it represents a potential risk to our ecosystems. [6], these contaminants can reach the natural waters degrading its quality. The scientific community is constantly developing removal methods, such as adsorption, membrane filtration, electrodialysis, ionic liquids [7,8], towards a suitable solution to this problem. Sorption and biosorption are some of the most promising methods to remove toxic metals. One of the major potential substances is the chitosan, a well-known biopolymer derived from alkaline
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