Utilization of Agricultural Waste: Chickpea Husk as a Sustainable Adsorbent for Thionine Dye Removal

ABSTRACT This study aimed to evaluate chickpea husk (CH) ( Cicer arietinum ), an agricultural waste, as a sustainable adsorbent for the removal of cationic thionine (TH) dye from aqueous solution. CH was utilized in raw powder form and after pyrolysis at 300°C (CH@300) and 800°C (CH@800). All materials were characterized using Fourier transform infrared spectroscopy, x‐ray diffraction (XRD), surface area analysis Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), energy‐dispersive x‐ray spectroscopy (EDX), and zeta potential. BET surface area analysis revealed that CH has a specific surface area 3.48 m 2 g −1 , whereas CH@300 and CH@800 exhibit 1.78 and 0.082 m 2 g −1 , respectively, indicating reducing in surface area with higher pyrolysis temperature. Among the three adsorbents (CH, CH@300, and CH@800), the raw CH exhibited the highest adsorption efficiency, achieving ∼90% removal of 10 ppm TH dye at 8.5 pH and room temperature, which is higher than of its pyrolyzed samples. The adsorption kinetics of CH adsorbent was fitted best with both linear and nonlinear pseudo‐second‐order with (>0.99) R 2 value for. The CH adsorbent has also shown referability up to three successive cycles. The finding demonstrates that CH is an efficient and sustainable biosorption for TH dye removal. Its high adsorption efficiency and good regeneration ability highlight its potential as a low‐cost material for wastewater application.