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.

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

Synthesis of biohybrid magnetic chitosan-polyvinyl alcohol/MgO nanocomposite blend for remazol brilliant blue R dye adsorption: solo and collective parametric optimization

Green method to synthesize magnetic zeolite/chitosan composites and adsorption of hexavalent chromium from aqueous solutions.

Green method to synthesize magnetic zeolite/chitosan composites and adsorption of hexavalent chromium from aqueous solutions

Chitosan displays a dual function, acting as both an active ingredient and/or carrier for pharmaceutical bioactive molecules and metal ions. Its hydroxyl- and amino-reactive groups and acetylation degree can be used to adjust this biopolymer’s physicochemical and pharmacological properties in different forms, including scaffolds, nanoparticles, fibers, sponges, films, and hydrogels, among others. In terms of pharmacological purposes, chitosan association with different polymers and the immobilization or entrapment of bioactive agents are effective strategies to achieve desired biological responses. Chitosan biocompatibility, water entrapment within nanofibrils, antioxidant character, and antimicrobial and anti-inflammatory properties, whether enhanced by other active components or not, ensure skin moisturization, as well as protection against bacteria colonization and oxidative imbalance. Chitosan-based nanomaterials can maintain or reconstruct skin architecture through topical or systemic delivery of hydrophilic or hydrophobic pharmaceuticals at controlled rates to treat skin affections, such as acne, inflammatory manifestations, wounds, or even tumorigenesis, by coating chemotherapy drugs. Herein, chitosan obtention, physicochemical characteristics, chemical modifications, and interactions with bioactive agents are presented and discussed. Molecular mechanisms involved in chitosan skin protection and recovery are highlighted by overlapping the events orchestrated by the signaling molecules secreted by different cell types to reconstitute healthy skin tissue structures and components.

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Chitosans and Nanochitosans: Recent Advances in Skin Protection, Regeneration, and Repair

Compared with traditional polymers, biopolymers are more environmentally friendly due to their sustainable sources, easy decomposition and naturally recycled by biological processes. Among all biopolymers, chitosan (CS) proves attractive for several adsorption-related applications such as in gas capture and removal of dyes or heavy metal ions. However, there are considerable drawbacks such as unstable yield, non-uniform sizes, lack of process repeatability, low mechanical strength and chemical resistance. Thus, physical and chemical modifications have been proposed to obtain stable size and improved mechanical property of CS beads, microspheres, film or fiber. This paper introduces the research background of CS and modified CS as an adsorbent and analyzes the modification, application and adsorption mechanism of CS and CS composite materials. The research progress of the adsorption of metal ions, dyes and anions by CS and CS composite materials is reviewed, and the main factors affecting their adsorption performance are summarized. Finally, the development trend of CS as adsorbents is prospected.

Xiaoqi Liu

Papers

Review on preparation and adsorption properties of chitosan and chitosan composites

Green method to synthesize magnetic zeolite/chitosan composites and adsorption of hexavalent chromium from aqueous solutions.

Preparation of magnetic zeolite/chitosan composite using silane as modifier for adsorption of Cr(VI) from aqueous solutions

Magnetic red mud/chitosan based bionanocomposites for adsorption of Cr(VI) from aqueous solutions: synthesis, characterization and adsorption kinetics

Removal of Cr(VI) and Ag(I) by grafted magnetic zeolite/chitosan for water purification: Synthesis and adsorption mechanism.