Cadmium removal using Rhassoul/alginate composite beads: isotherms, kinetics, and thermodynamic study

Cadmium is a threat to human health and the environment. Therefore, there is a need for efficient and sustainable adsorbents to remediate cadmium-contaminated water. This study explores the effectiveness of Rhassoul clay/alginate composite beads in adsorbing cadmium from aqueous solutions, a simple, efficient, and cost-effective water treatment method. Various physicochemical factors influencing the adsorption capacity of the Rhassoul/alginate hybrid composite beads were examined, including adsorbent dosage (0.5–4.0 g/L suspension), contact time (30–360 min), pH (2–7), initial Cd²⁺ concentration (20–200 mg/L), and temperature (25–40 °C). The results revealed an adsorption capacity of 20 mg/g for non-modified Rhassoul clay, while the Rhassoul/alginate composite beads exhibited a significantly higher maximum adsorption capacity of 105 mg/g. Thermodynamic parameters (∆G°, ∆H°, and ∆S°) indicated the process was spontaneous and endothermic.