KINETICS OF CONGO RED ADSORPTION USING RAW RICE HUSK AS ADSORBENT
Abstract
ABSTRACT
This study examined the adsorption of Congo red dye onto raw rice husk as a low-cost and eco-friendly biosorbent. Fourier Transform Infrared (FTIR) analysis revealed the presence of key functional groups, including hydroxyl (O–H), carbonyl (C=O), and C–O groups, indicating the availability of active binding sites derived from cellulose, hemicellulose, and lignin. These groups facilitate dye uptake through hydrogen bonding and electrostatic attraction. Optimization of process parameters using the Box–Behnken design showed that dye removal efficiency ranged from 7.39% to 75.94%, significantly influenced by adsorbent dosage, dye concentration, agitation speed, and contact time. Analysis of Variance (F = 4.93, p < 0.05) confirmed the model’s adequacy, with adsorbent dosage and dye concentration identified as the most significant factors. The optimal conditions for maximum dye removal (75.67%) were achieved at a dosage of 0.078 g/50 cm³, dye concentration of 60 mg/L, agitation speed of 70 rpm, and contact time of 10 minutes. Kinetic modeling indicated that the pseudo-second-order model (R² = 0.996) best described the adsorption process, suggesting chemisorption as the rate-limiting step involving electron sharing or exchange between dye molecules and surface functional groups. Overall, raw rice husk demonstrated high potential as an efficient, sustainable adsorbent for removing Congo red from aqueous solutions.
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