Modification of rice husk silica with bovine serum albumin (BSA) for improvement in adsorption of metanil yellow dye

In the present research, bovine serum albumin-modified silica from rice husk has been prepared and examined as adsorbent for removal of the metanil yellow dye. The silica was obtained by purification of silica from the rice husk. Rice husk was heated up at 700 °C for 4 h, the obtained rice husk ash was mixed with NaOH 5% and acidified with HNO3 10% to obtain silica. The modification was carried out by reacting silica with bovine serum albumin, and the amine-functionalized rice husk silica was obtained. The rice husk silica and amine-functionalized rice husk silica were characterized by Fourier-transform infrared, X-ray fluorescence, scanning electron microscopy, and Brunauer–Emmett–Teller. The adsorption study was conducted using batch method and investigated some parameters such as pH, adsorbate concentration, contact time, and temperature. The maximum adsorption capacity of rice husk silica and amine-functionalized rice husk silica was 25.975 and 82.345 mg/g, respectively. The adsorption process of metanil yellow dye onto rice husk silica followed Langmuir isotherm model. Besides, the adsorption of metanil yellow dye onto amine-functionalized rice husk silica was fitted to both Langmuir and Freundlich isotherm models (R2 = 0.99). The kinetic data were well described by the pseudo-second-order (R2 = 0.99) indicated a chemisorption process. The thermodynamic equation showed that the adsorption of metanil yellow dye onto rice husk silica was spontaneous through an endothermic reaction, while the adsorption onto amine-functionalized rice husk silica was spontaneous through exothermic reaction.