Efficient Removal of Diclofenac Sodium and Hg(II) on Graphene Oxide/UiO-66-(OH)₂ Composites

Developing efficient adsorbents for removal of organic pollutants and heavy metals is essential for environmental protection. In this study, a series of GO/UiO-66-(OH)₂ composites were synthesized and characterized using XRD, FT-IR, and SEM, confirming enhanced thermal stability, reduced aggregation, and maintained crystallinity of UiO-66-(OH)₂ due to GO incorporation. Batch adsorption experiments showed that GO increased the adsorption capacity, with GO-8/UiO-66-(OH)₂ achieving 324.2 mg/g for diclofenac sodium (DCF) and 429.3 mg/g for Hg²⁺. DCF adsorption was primarily governed by physisorption, while Hg adsorption was chemisorptive, involving strong coordination with oxygen functional groups. Kinetic and isotherm studies revealed the suitability of the pseudo-second-order and Freundlich models, with thermodynamic analysis showing exothermic DCF adsorption and endothermic Hg²⁺ adsorption. The composites also exhibited high selectivity and stable regeneration, making them promising candidates for practical environmental remediation.