Dual removal of Thallium (Tl <sup>+</sup> ) and Auramine O using alginate-coated iron oxide nanocomposites for sustainable wastewater treatment
Fawziah A. Al‐Salmi, Eman Fayad, Mahmoud F. Mubarak, Mohamed Hemdan
Abstract
The presence of thallium (Tl+) and Auramine O (AO) in water sources poses significant ecological and human health hazards due to their extreme toxicity, long-term stability, and tendency to bioaccumulate in living organisms. This research introduces an innovative alginate-functionalised iron oxide nanocomposite (Alg-Fe3O4 NC) designed for the concurrent elimination of Tl+ and AO from aqueous environments. Detailed characterisation through SEM, XRD, FTIR, TGA, and BET analyses validated its mesoporous architecture, robust physicochemical stability, and substantial surface area (242.44 m2/g). The adsorption experiments demonstrated that the nanocomposite achieved maximum uptake capacities of 95.86 mg/g for Tl+ and 138.44 mg/g for AO. The process adhered to the Langmuir isotherm model (R2 = 0.998 for Tl+, 0.997 for AO), confirming monolayer adsorption on a uniform surface. Kinetic analysis indicated that adsorption followed the Pseudo-Second-Order (PSO) model (R2 = 0.995 for Tl+, 0.993 for AO), implying a chemisorption-dominated mechanism governed by electrostatic interactions, ion exchange, and hydrogen bonding. Thermodynamic analysis (ΔH° = 22.85 kJ/mol for Tl+, 28.64 kJ/mol for AO) demonstrated an endothermic and spontaneous adsorption process. The nanocomposite retained 91.47% (Tl+) and 90.11% (AO) removal efficiency after six cycles, confirming its excellent reusability. In contrast to traditional adsorbents, the engineered Alg-Fe3O4 nanocomposite demonstrates enhanced adsorption efficiency, establishing it as a highly effective, economical, and environmentally sustainable material for wastewater treatment applications.