Effectiveness of Polyurethane Foam Coated Chitosan/MXene Nanoparticles as Low-Cost Adsorbent for Heavy Metal Removal

Abstract

Heavy metal removal from wastewater remains a paramount challenge with rapid industrialization and its ubiquitous utilities. Currently, the generation of clean water and environmental protection are two indispensable/requisite areas for a sustainable society. Two-dimensional (2D) materials' applicability in water treatment is continuously accelerating by enabling new discoveries. Recently, MXenes generated tremendous popularity in the 2D materials family due to unique physicochemical properties and stability that as adsorbents make them attractive for the removal of heavy metals. Although the adsorption performance of MXenes may compete effectively with other nanomaterials adsorbents, the interplay with different materials is insufficient/inadequate/restricted for further development of low-cost material for commercial applications. Herein, a potential MXene (Ti3AlC2) combined with Chitosan, an abundant crustacean’s polymer, as surfactant on polyurethane foam (PUF) for the removal of toxic hexavalent chromium from synthetic wastewater via adsorption process. The sorption capabilities of PUF for wastewater were enhanced using MXene nano-sheets adherence to the pores, while Chitosan beforehand was used as a surfactant for constructive deposition of MXene nano-sheets. Positively charged Chromium (VI) ions are adsorbed on negatively charged MXene via electrostatic attraction and ion exchange mechanism. An assay of assessment is done through a series of batch and fixed-bed column studies using PUF cubes coated with Chitosan and three different layers of MXene over Chitosan. Complete removal of hexavalent chromium in 2 hours has been observed in the batch process, which is quite promising. Detailed characterization techniques were employed to identify elements, structural type, and chemical functionality. Additionally, Langmuir and Freundlich kinetic model for batch operation confirms the chemisorption during the process. Furthermore, briefed fixed bed column experiments were performed to check the continuous operation stability of the adsorbent for future perspective. The experimental study attributed the favorable and economically sustainable aspect of potential adsorbent in water treatment applications as compared to the usage in an individual capacity in powder form.