Remediation of sodium dodecyl sulfate-contaminated water using biochar derived from lemon peel and incorporated with calcium alginate beads

Surfactants, a vital class of substances widely used in modern life, have detrimental effects on both aquatic life and human health. The current research work discusses a simple and environmentally sustainable method for removing sodium dodecyl sulphate (SDS), an anionic surfactant, from wastewater. For this purpose, lemon peel-derived biochar (LPBC) and calcium alginate (CA) were combined to get a novel composite adsorbent referred to as LPBCCA. Fourier transform infrared spectroscopy and scanning electron microscopy were used to characterize the LPBC, CA, and LPBCCA. The zero point charges of LPBC, CA, and LPBCCA were determined to be 4.3, 8.5, and 7.5, respectively. The batch adsorption experiment showed optimum pH values of 6, 8, and 7 for LPBC, CA, and LPBCCA, respectively. Under optimum conditions the maximum adsorption capacities were found to be 6.29, 1.86, and 42.77 mg/g for LPBC, CA, and LPBCCA, respectively. Isotherm studies suggested that adsorption of SDS on LPBC and CA followed the Temkin adsorption isotherm, while its adsorption on LPBCCA followed the Langmuir adsorption isotherm. The pseudo-second-order equation was more consistent with the adsorption kinetics results for LPBCCA and LPBC, indicating that chemical adsorption dominated the adsorption process. Adsorption on CA obeyed pseudo-first-order kinetics. Thermodynamic investigations revealed that sodium dodecyl sulfate adsorption on LPBC, CA, and LPBCCA was exothermic and spontaneous, with lower temperatures facilitating adsorption. Up to three cycles, LPBCCA has superior regeneration efficiency when compared to LPBC and CA. After three adsorption–desorption cycles, the regeneration analysis revealed that LPBCCA maintained 61% adsorption efficiency, suggesting moderate reusability and potential for recurrent application.