Preparation and dye adsorption properties of activated carbon/clay/sodium alginate composite hydrogel membranes

Abstract

A hydrogel membrane was prepared using activated carbon and sodium dodecyl sulphate modified montmorillonite clay incorporated into sodium alginate polymer. The activated carbon was prepared from a locally available susbine plant. The physiochemical characteristics of the synthesized hydrogel membrane were investigated using FTIR, SEM, EDX, and TGA techniques. The performance of the membrane was evaluated as an adsorbent by methyl red adsorption from water. The adsorption behavior of the hydrogel membrane was investigated under varying conditions of pH (2–10), membrane dose (0.0025–0.015 mg g⁻¹), equilibrium adsorption time (30–360 minutes), solution temperature (25–45 °C) and dye concentration (100–500 mg L⁻¹). The maximum adsorption capacity of the hydrogel membrane was 248.13 mg g⁻¹. The kinetics of methyl red adsorption on hydrogel membrane best followed the pseudo-second order (PSO). The equilibrium adsorption results suggested that it obeyed the Freundlich isotherm very closely (R² = 0.994). The thermodynamics of methyl red adsorption on the hydrogel membrane revealed that the adsorption was spontaneous (ΔS° = 16.15 kJ K⁻¹ mol⁻¹), favorable (ΔG° = −3.51 kJ mol⁻¹), and endothermic (ΔH° = −1.48 kJ mol⁻¹) in nature. These investigations suggested that the fabricated hydrogel membrane could be suitably used for methyl red adsorption from the solution.