A review of LDH-cellulose hybrid adsorbents for organic and inorganic pollutant removal from wastewater.

Abstract

This review reported the recent advances in the synthesis of LDH-cellulose hybrid adsorbents for wastewater treatment. Particular emphasis is placed on the different forms of cellulose employed: microfibrillated cellulose, cellulose nanofibrils, cellulose nanocrystals, and bacterial cellulose, which provide rich functional groups, high specific surface area, biodegradability, and structural flexibility. LDHs, including widely studied MgAl, ZnAl, NiFe, and CaAl layered double hydroxides with variable interlayer anions, have excellent anion exchange capacity, tunable chemical composition, and good binding ability with a wide range of pollutants, while cellulose can offer rich functional groups, high specific surface area, biodegradability, and structural flexibility. Assembling these two building blocks creates an LDH-cellulose composite with adsorption properties, mechanical properties, and ecological safety. Unlike previous reviews, this work integrates a comprehensive analysis of LDH-cellulose hybrid adsorbents by simultaneously addressing synthesis strategies, structural-property relationships, adsorption mechanisms, regeneration and challenges, and future perspectives. The review categorizes the main synthesis strategies, i.e., in situ co-precipitation, impregnation, and hydrothermal processes, indicating how the synthesis routes influence the particle morphology, pollutant dispersion, and pollutant removal capacity. It critically investigates the adsorption processes, i.e., ion exchange, electrostatic interaction, hydrogen bonding, and surface complexation. Finally, the review presents existing limitations like regeneration issues, cost-effectiveness, and applicability in real wastewater systems, and proposes avenues for future research. Briefly put, the article brings to the fore the application of LDH-cellulose composites, engineered from specific cellulose derivatives and LDH compositions, as forward-looking and enhanced-efficiency materials for high-end wastewater treatment.