Combined clinoptilolite and Fe(O)OH for efficient removal of Cu(II) and Pb(II) with enhanced solid-liquid separation

This study investigated combining fine clinoptilolite with iron hydroxide coagulant, as a cost-effective, dual-purpose flocculant for enhanced removal of Pb²⁺ or Cu²⁺ ions, along with the solid-liquid separation and physicochemical analysis. For the clinoptilolite, adsorption kinetics fitted a pseudo-second-order (PSO) rate model with higher rate constants for Pb²⁺, while equilibrium adsorption data fitted the Langmuir monolayer model, with Q similar at 18.8 mg/g for Pb²⁺ and 18.3 mg/g Cu²⁺. TEM elemental mapping of the clinoptilolite evidenced areas of K and Fe impurities, while SEM suggested a uniform distribution of aggregates comprising a clinoptilolite core with decorated FeOOH. X-ray diffraction (XRD) indicated the FeOOH phase as α-FeOOH (Goethite) with no change in structure on inclusion of adsorbed Pb²⁺. Combined clinoptilolite-FeOOH flocs were significantly larger than FeOOH only precipitates, while flocs formed from 0.5 wt% FeOOH and 1 wt% clinoptilolite produced the fastest settling rates and greatest consolidation. Compressive yield stress data also correlated with enhanced dewatering of the combined systems, due to the dense clinoptilolite acting as a weighter material. For final metals removal, combined flocs outperformed FeOOH across a broad concentration range, achieving > 98% removal for both Pb²⁺ or Cu²⁺. The greater metals removal combined with denser floc production and improved settling features highlights significantly enhanced performance above that possible from either ion exchange or precipitation alone.

The online version contains supplementary material available at 10.1007/s43938-025-00075-y.