An Overview of Modified Chitosan Adsorbents for the Removal of Precious Metals Species from Aqueous Media

Abstract

This mini-review provides coverage of chitosan-based adsorbents and their modified forms as sustainable solid-phase extraction (SPE) materials for precious metal ions, such as gold species, and their complexes in aqueous media. Modified forms of chitosan-based adsorbents range from surface-functionalized systems to biomaterial composites that contain inorganic or other nanomaterial components. An overview of the SPE conditions such as pH, temperature, contact time, and adsorbent dosage was carried out to outline how these factors affect the efficiency of the sorption process, with an emphasis on gold species. This review provides insight into the structure-property relationships for chitinaceous adsorbents and their metal-ion removal mechanism in aqueous media. Cross-linked chitosan sorbents showed a maximum for Au(III) uptake capacity (600 mg/g), while S-containing cross-linked chitosan display favourable selectivity and uptake capacity with Au(III) species. Compared to industrial adsorbents such as activated carbon, modified chitosan sorbents display favourable uptake of Au(III) species, especially in aqueous media at low pH. In turn, this contribution is intended to catalyze further research directed at the rational design of tailored SPE materials that employ biopolymer scaffolds to yield improved uptake properties of precious metal species in aqueous systems. The controlled removal of gold and precious metal species from aqueous media is highly relevant to sustainable industrial processes and environmental remediation.

Importance of a nano-sized molybdenum composite synthesized using a microwave oven in the sorption enhancement of Au(iii) from the aqueous phase

“…The binding energy for elements or functionalities on the samples was measured by an X-ray photoelectron spectrometer (XPS, K-Alpha, Thermo Fisher Scientific, USA) with Al Kα (1486.6 eV) radiation as an X-ray source. The XPS data were calibrated using the binding energy of the C 1s peak of the adventitious carbon Given that the uncrosslinked chitosan is soluble under acidic conditions, 30,31 CS and CS-MoCOM cannot be used for sorption experiments. Unless otherwise specified, all sorption experiments were carried out by soaking 3.0 mg nanofiber mat in 90 mL of 1 mg mL −1 HAuCl 4 •4H 2 O solution (concentration of Au(III) is approximately 0.48 mg mL −1 ) at 25 °C, then shaking at 180 rpm for 24 h. According to the pH experiment results (Fig.…”

“…Moreover, chitosan is the only natural cationic polysaccharide among biomacromolecules, which theoretically facilitates Au( iii ) sorption by electrostatic attraction because it is usually present in the form of anions in the aqueous phase. 31 However, chitosan is soluble under acidic condition and has poor mechanical strength, which greatly limits its practical applications.…”

Catechol-Functionalized Chitosan Synthesis and Selective Extraction of Germanium (IV) from Acidic Solutions

“…Chitosan has been used as a solid support for further functionalization with ligands to recover critical elements such as Ge, rare-earth elements, Pd, and Pt . Chitosan is abundant, readily available, cheap, and can be easily functionalized.…”

Preparation of Amphiphilic Chitosan-Loaded Bentonite Adsorbent and Its Performance in Removing Organic Matter from Coking Wastewater

“…The advantages of chitosan include the following characteristics: biodegradability, low toxicity, and easy chemical modification [ 16 ]. CTS has been used in many fields such as food, medicine, cosmetics, and wastewater treatment [ 17 ]. Although the specific surface area of CTS is relatively small, its molecular structure is rich in active groups, which can achieve the migration of pollutants from wastewater through the interaction between acting groups on the adsorbent surface and pollutants [ 18 ].…”