Fabrication of Biochar-Modified Alginate Beads and Study of Its Potential for Eliminating SDS from Water

Abstract

Hydrogel-based adsorbents have attracted increasing attention for the removal of surfactants from wastewater; however, limitations related to adsorption efficiency and material cost remain insufficiently addressed. This study investigates the synthesis and performance of biochar-modified alginate hydrogel beads derived from banana peel waste for the removal of sodium dodecyl sulfate (SDS) from aqueous solutions. The adsorbent was characterized using scanning electron microscopy and Fourier transform infrared spectroscopy to examine surface morphology and functional groups involved in adsorption. Batch adsorption experiments were conducted to evaluate the effects of pH, contact time, adsorbent dosage, and initial SDS concentration. Optimal adsorption conditions were identified at pH 8, initial concentration of 20 mg/L, adsorbent dosage of 0.02 g/50 mL, and contact time of 60 min, yielding a maximum adsorption capacity of 64.93 mg/g. Adsorption equilibrium data were best described by the Langmuir isotherm model, indicating monolayer adsorption, while kinetic analysis showed good agreement with the pseudo-second-order model, suggesting chemisorption as the dominant mechanism. Thermodynamic parameters revealed a negative Gibbs free energy change, confirming the spontaneous nature of the adsorption process. Regeneration studies demonstrated that the adsorbent retained appreciable performance over multiple cycles, indicating its potential for reuse. These findings suggest that biochar-modified hydrogel beads provide a sustainable and effective approach for surfactant removal from wastewater.