Abstract
The necessity of decontaminating effluents for the dual purpose of environmental beneficiation and valorization of low-grade resources is driving the development of new sorbents. The functionalization of biopolymers is a promising strategy for improving sorption performance. Incorporating magnetic micro-particles offers an opportunity for the facilitated recovery of spent micron-size sorbent. Combining magnetic facilities and biopolymer functionalization represents a winning strategy. Magnetic glycine-grafted chitosan (G@MChs) was synthesized for the sorption of Ni(II), Zn(II), and Hg(II) before being applied to the removal of hazardous and strategic metals from tailing leachates. The sorbent was characterized using Fourier transform infrared spectroscopy and scanning electron microscopy, before and after metal sorption. The acid–base properties of functionalized sorbent were also determined (pHPZC). Uptake kinetics were studied in mono- and multi-component solutions using different equations for kinetic modeling at optimized pH (i.e., pH0: 5.5). Langmuir and Sips equations were applied to model sorption isotherms in single-component solutions. In addition, sorption isotherms in multi-component solutions were used to evaluate the preference for selected metals. Maximum sorption capacities were 0.35 mmol Hg g−1, 0.47 mmol Zn g−1, and 0.50 mmol Ni g−1. Acidified urea solution (pH 2.7) successfully desorbs metal ions from G@MChs (desorption > 90%). The sorbent was tested for the recovery of hazardous and strategic metal ions from acidic leachates of tailings. This study demonstrates the promising performance of G@MChs for the treatment of complex metal-bearing solutions.
Highlights
The increasing demand placed on water supply due to population growth, agriculture needs, and industrial uses has led to the implementation of drastic regulations at international and national levels for the discharge of wastewater into the environment.The accumulation of contaminants, such as heavy metals, in the food chain may explain the special attention they have received from the community and regulators
The sorption of mercury consumes less protons than the binding of other divalent cations. These results offer a first indication as to the preference of the sorbent for metal ions according the series: Hg(II) > Zn(II) > Ni(II)
The grafting of glycine onto magnetic chitosan allows the elaboration of microparticles with enhanced sorption properties for heavy metal removal from aqueous solutions
Summary
The increasing demand placed on water supply due to population growth, agriculture needs, and industrial uses has led to the implementation of drastic regulations at international and national levels for the discharge of wastewater into the environment.The accumulation of contaminants, such as heavy metals, in the food chain may explain the special attention they have received from the community and regulators. For the decontamination of water sources at drinkable levels, membrane techniques are more appropriate, but these techniques are frequently very expensive, and are preferred for the treatment of limited flow rates with low initial metal concentrations. Extractant impregnation of porous resins has been investigated for metal removal; the immobilization of the extractant prevents the release and the loss of hazardous and expensive reagents with optimized transfer properties (driven by the porosity of the supports [3,4,5]). This is an intermediary technique between solvent extraction process and sorption on functional resins. Sorption processes using ionexchange or chelating resins [6,7], carbon-based sorbents [8,9], inorganic supports [10,11,12,13]
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