Utilizing pineapple peel crosslinked chitosan as an eco-friendly biosorbent for heavy metal removal: A circular economy perspective

Abstract

This study fabricated chitosan beads obtained from pineapple peels as sustainable biosorbents for hexavalent chromium (Cr (VI)) extraction from water, thus supporting circular economy initiatives. Heavy metal pollution in water systems is a crucial environmental issue that has serious consequences for human health, aquatic ecosystems, and the overall environment. Heavy metals such as lead (Pb), cadmium (Cd), chromium (Cr), zinc (Zn), and copper (Cu) are particularly problematic since they are non-biodegradable, tend to bioaccumulate in organisms, and have the ability to impair cellular function, posing long-term ecological and public health problems. Two biosorbents, PPA (glutaraldehyde crosslinked) and PPB (citric acid crosslinked), were synthesized and investigated using SEM and FTIR to investigate the structural and functional changes caused by the crosslinking agents. While PPB included more carboxyl groups due to citric acid crosslinking, FTIR analysis confirmed the presence of functional groups required for Cr (VI) binding. With optimal Cr (VI) removal at pH 3.0, testing results revealed maximal adsorption capacities of 18.87 mg/g for PPA and 21.01 mg/g for PPB. Increased availability of functional groups and adsorption surface stability improve PPB performance. Adsorption isotherm analysis revealed that both biosorbents followed the Freundlich model, indicating a heterogeneous adsorption mechanism. Kinetic investigations identified pseudo-first-order chemisorption as the major mechanism. Thermodynamic investigation revealed negative Gibbs free energy values (∆G), confirming the spontaneous nature of Cr (VI) adsorption. With PPB showing improved performance, this study demonstrates the efficacy of chitosan beads generated from pineapple peels as a sustainable and low cost biosorbent for heavy metal cleanup. The findings emphasize the importance of crosslinking agents in improving biosorbent performance, giving valuable information for the development of efficient and cost-effective wastewater treatment methods aligned with sustainability and circular economy concepts.