Removal of Cadmium and Lead Ions from Aqueous Solutions Using Lignin-Cellulose Acetate Composite Extracted from Walnut Shell

Abstract

The composite of partially esterified cellulose (PES) and lignin was extracted from walnut shells using a choline chloride/oxalic acid mixture, known as a deep eutectic solvent (DES). This composite was used to remove heavy metal ions from the water-based mixture. Various physicochemical techniques, including FTIR, FESEM, NMR, BET, and EDX, were utilized to characterize the resulting adsorbent. The adsorption of lead and cadmium ions was modeled using the PSO and Langmuir equations, with the composite adsorbent demonstrating maximum adsorption capacities of 88.49 mg/g for cadmium and 112.36 mg/g for lead. Several factors influencing metal ion adsorption were investigated, including shaking time, temperature, adsorbent dosage, pH, and metal ion concentration. Notably, the absorbent could be regenerated and reused through treatment with 0.1 M hydrochloric acid.