Green synthesis of immobilized hybrid biocomposite from natural waste for dye sequestration: a kinetic and isothermal approach

Abstract

This study investigates the development of a low-cost and sustainable immobilized hybrid biocomposite for the removal of Drimarine Black CL-B (DB CL-B) dye from aqueous solutions. The biocomposite was synthesized using waste-derived granite powder (G) and Syzygium cumini leaf biomass (S), immobilized within a sodium alginate beads matrix (NAB) to obtain GS@NAB biocomposite. The biocomposite was characterized using SEM and FTIR techniques, confirming the surface morphology favorable for adsorption and successful incorporation of functional groups. Batch adsorption experiments were conducted to evaluate the removal efficiency under optimum conditions. The parameters such as adsorbent dosage, contact time, pH, and temperature were optimized to conduct the adsorption experiments. The results showed that the adsorption process followed a pseudo-second-order kinetic model, indicating chemisorption as the dominant mechanism. Equilibrium studies revealed that the adsorption data were best described by the Langmuir isotherm, suggesting monolayer adsorption on a homogeneous surface. Among htree parameter isotherms, Vieth-Sladek offers best fit (R2 = 0.999). While Langmuir describes the dominant adsorption behavior, Vieth–Sladek provides supplementary evidence that the GS@NAB surface contains structurally diverse domains arising from the combined mineral, biomass, and polymeric components. Overall, the developed GS@NAB biocomposite demonstrated effective dye removal performance up to six cycles and offers a cost-effective and environmentally friendly alternative for wastewater treatment applications.