Integrated fabrication of CMC@UiO-66-NH₂@PEI composite adsorbents for efficient batch and dynamic phosphate capture

Adsorption technology has been regarded as an efficient method for removing low-concentration phosphate ions from water; however, the designed fabrication of expectable sorbents by integrating biomass components and MOFs remains a challenge. Herein, carboxymethylcellulose (CMC) and UiO-66-NH2 were mixed evenly and then dropped into a lanthanum chloride solution to form beads. Subsequently, the formed pellets underwent in situ polymerization using polyethyleneimine (PEI) to modify their surface. This surface modification with PEI aimed to enhance the mechanical stability of the pellets and improve their ability to remove phosphorus. This is an interesting approach to achieving enhanced performance in terms of both mechanical stability and phosphorus removal. We conducted an investigation into the impact of varying MOF contents and PEI concentrations on the adsorption performance. The optimal ratio adsorbent 0.2CUI has a maximum adsorption capacity of 293.27 mg P per g for phosphate. After investigating the impact of pH on the adsorption performance, we have discovered that 0.2CUI is highly effective in adsorbing phosphate across a broad pH spectrum. Adsorption investigations have indicated that the adsorption of phosphate follows the pseudo-second-order kinetic model and the Freundlich isotherm model. Furthermore, the dynamic adsorption performance tests revealed a significant correlation coefficient for the Thomas model. At the same time, cyclic experiments involving adsorption and desorption were conducted to assess the reusability of the prepared hydrogel. The advancement of phosphate adsorbents is approached from a new perspective in this study.