Alginate/Phosphine-Functionalized Chitosan Beads Towards the Removal of Harmful Metal Ions from Aqueous Medium

Journal of Polymers and the Environment(2022)

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Among the many strategies utilized to improve the adsorption capacity of adsorbent materials, the modification of their chemical nature has been widely exploited, especially considering the polysaccharide-based adsorbents. Based on this, a phosphine-functionalized chitosan derivative (CSPPh 2 ) was associated with alginate (Alg), resulting in beads that were utilized to adsorb Cd 2+ and Al 3+ from water. After a complete characterization [Fourier transformed infra-red (FTIR), X-ray diffraction (XRD), thermogravimetric analyses (TGA/DTG), scanning electron microscopy (SEM), swelling analysis, and pH of point of zero charge (pH PZC )], adsorption experiments were performed to determine the optimal operational conditions. Under similar conditions, the Alg/CSPPh 2 showed superior adsorption performance compared to the beads prepared using raw chitosan. Moreover, the maximum adsorption capacities for Cd 2+ (78.2 mg/g) and Al 3+ (81.5 mg/g) were computed to Alg/CSPPh 2 beads under mild conditions (pH 6.0, 25 °C, 50 mg of adsorbent). The adsorption process for both metals was well-fitted by the pseudo-first-order kinetics and Freundlich isotherm model. Overall, the adsorption of these metals on Alg/CSPPh 2 occurred via physical interaction forces, and the functional groups on the beads, including the –PPh 2 groups, have a pivotal role as binding sites. The post-utilized beads could be regenerated and reused up to 5 times consecutively with a slight decrease in their removal capacity. This study demonstrated that these original beads containing phosphine-functionalized chitosan are enhanced adsorbents to remove metal ions of different valences from the water environment.
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Key words
Adsorption, Polysaccharides, Aluminum, Cadmium, Reuse, Tap-water
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