Brilliant Green Biosorption from Aqueous Solutions on Okara: Equilibrium, Kinetic and Thermodynamic Studies

Abstract

Brilliant green (BG), a basic dye, is toxic to lung, eye, and skin. This study examines BG biosorption from aqueous solution using soybean milk residue (okara). A series of batch tests were conducted to explore influential factors including pH, biosorbent dose, initial BG concentration, contact time, and temperature. The isotherm data were fitted with Langmuir and Freundlich models. The kinetic data of BG biosorption by okara were analyzed using pseudo-first order and pseudo-second order models. The BG removal efficiency was enhanced at a higher biosorbent dose, contact time, and temperature. Contrarily, the greater BG initial concentration resulted in a decline in BG removal efficacy. In the pH range that BG dye was stable, the highest BG removal was attained at pH 5. The maximum BG adsorption capacity of okara was 64.33 mg/g. Langmuir model (R2 = 0.98) was more appropriate than Freundlich model (R2 = 0.93) in describing isotherm data. Kinetic data was well fitted with Pseudo-second order model (R2 = 0.99). Thermodynamic results suggest the spontaneous and endothermic nature of the GB biosorption. The use of okara as a novel BG biosorbent can help not only wastewater decontamination but also recycling of okara in a green way.

Keywords

• okara
• biosorption
• brilliant green dye
• isotherms
• kinetics