Ambient synthesis of La embedded ZIF-8 core-shell adsorbent for selective fluoride removal from Tanzanian geothermal water: Performance, kinetics, and isotherms

초록

Fluoride contamination in drinking water is a serious global health concern, particularly in geogenic hotspots such as Tanzania, where concentrations often exceed the WHO guideline of 1.5 mg L−1. In this study, we report the rational design and room-temperature synthesis of a novel composite adsorbent, La-ZIF-8, for efficient and selective fluoride removal. The material combines the high surface area and porosity of ZIF-8 with the strong fluoride affinity of La³ ⁺ sites, resulting in a hierarchical structure with enhanced adsorption performance. Structural and surface analyses using XRD, SEM, TEM, XPS, and BET confirm successful integration, preserved crystallinity, and uniform elemental distribution. La-ZIF-8 exhibits a high fluoride adsorption capacity of 13.82 mg g⁻¹ and effectively reduces fluoride concentrations in real Tanzanian groundwater samples from 2.1 to 8.7 mg L−1 to below the WHO limit without pH adjustment. Adsorption kinetics and isotherm studies indicate chemisorption-dominated fluoride uptake, well described by the pseudo-second-order and Langmuir models. The material shows excellent selectivity toward fluoride in the presence of common competing anions and maintains over 95 % removal efficiency after five regeneration cycles. These results highlight La-ZIF-8 as a promising, scalable adsorbent for sustainable defluoridation of fluoride-contaminated groundwater. © 2026 Elsevier Ltd.

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