Abstract

The efficiency of low-cost, eco-friendly chitosan groundnut (Arachis hypogaea) shell powder (Ch-GNSP) composite beads were evaluated for the removal of Acid Black 172 (AB-172) dye. The composite was developed by integrating foodgrade chitosan with agro-industrial groundnut shell waste, promoting sustainable biomass valorization for food-processing wastewater management. Parameters such as initial dye concentration, pH, contact time and adsorbent’s dosage were evaluated in the batch adsorption experiments. The maximum removal (89%) was observed at pH 2, with an equilibrium attained at 60 min. The adsorption mechanism followed pseudo-second-order kinetics (R^² = 0.994), signifying chemisorption. The data were most accurately represented by the Langmuir isotherm model (R^² = 0.95), indicating monolayer adsorption with a calculated maximum adsorption capacity (q_m) of 53.30 mg/g (R^L = 0.2855). The separation factor confirmed that the adsorption process was favorable. Desorption of the dye was observed during the experiments for all initial concentrations within the 30 – 180 min interval. At 5 mg/L, desorption increased markedly from 21.9% to 85.3%, representing the highest recovery efficiency among the tested values. The enhanced adsorption performance is attributed to the functional amino groups of chitosan and the porous structural framework of the composite matrix, which provide abundant active binding sites. These results demonstrate that Ch-GNSP beads are effective for anionic dye removal under acidic conditions and hold promise as a sustainable food-compatible adsorbent for wastewater treatment applications, offering a practical solution for the removal of dyes generated by food-processing and related industries with good reusability potential.

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