Recovery of Heavy Metal Ions Using Magnetic Glycine-Modified Chitosan—Application to Aqueous Solutions and Tailing Leachate

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.

Mesoporous Magnetic Cysteine Functionalized Chitosan Nanocomposite for Selective Uranyl Ions Sorption: Experimental, Structural Characterization, and Mechanistic Studies

“…A strong and broad absorption band at 34 cm −1 can be attributed to overlapped bands for -OH and -NH stretching vibrations, well as polysaccharide hydrogen bonds [22]. The high-intensity peaks in 2916, 2873, a 1384 cm −1 were assigned to C-H stretching vibration (CH2 at C-6, symmetric and asy metric) and C-H bending, respectively [7,28]. The significant peak at 1628 cm −1 can attributed to N-H bending vibration (-NH2 and >NH amine bend-in plane deformatio as well as symmetric stretching of (COO − ) carboxylate group grafting [5,7].…”

“…Cysteine was functionalized with cross-linked magnetic chitosan nanocomposite as depicted in Scheme 1 using a generic approach. The cross-linked magnetic chitosan nanocomposite was suspended in aqueous ethanol solution (75 mL, 1:1 in v/v) before 10 mL of epichlorohydrin was added; refluxing the mixture at 65-70 • C for 3 h yielded the desired results [7]. The product was filtered and rinsed thoroughly with ethanol and ultrapure water.…”

“…The K-Alpha spectrometer (Thermo Fisher Scientific, Waltham, MA, USA) was used to acquire X−ray photoelectron spectroscopy (XPS) data using a monochromatic Al Kα-radiation source (200 W). The sorbent's pH point of zero charge (pHPZC) was measured using the pH−drift method [7,8], and the sorbent was equilibrated for 24 h under agitation with a series of 0.1 M NaCl solutions with different initial pH-values (pH0); the equilibrium pH (pHeq) was recorded, and the pHPZC was the pH at which ΔpH = 0. Scheme 1.…”

“…The magnetite can be oxidized to other ferric hydroxide phases, e.g., maghemite by the ion transfer process (Fe [21], goethite (α-FeOOH), and sometimes hematite (4Fe 3 O 4 + 4O 2 → 6Fe 2 O 3 ) [21,24]. To avoid both dissolving in acidic environments, magnetite-chitosan nanocomposites are cross-linked using epichlorohydrin, and sorption capacity loss is prevented when amine groups are included (i.e., aldehyde crosslinking is used) [7]. Further, the crosslinking unifunctional agent is employed to generate covalent connections with the C-atoms attached to chitosan's hydroxyl groups (related to the epoxide ring rupture and a chlorine atom being released) [5].…”

“…Consequently, uranium separation and recovery are important processes in terms of both uranium resource exploitation and environmental preservation. Sorption (sometimes called solid-phase extraction) is a promising method for recovering metal ions from dilute effluents, due to its low environmental impact, quick kinetics, excellent selectivity, ease of handling, and great efficiency [2,[6][7][8][9]. Recent progress in uranium(VI) ion sorption from contaminated water has been conducted using various sorbents such as organic materials, e.g., cellulose/chitosan-based sorbent materials [1-5], functionalized synthetic polymers [1,10], hydrogel [11], and aerogel [12].…”