Adsorption of Rhodamine B from an aqueous solution onto NaOH-treated rice husk

Batch adsorption of Rhodamine B (RhB) dye from wastewater onto NaOH-treated rice husk (TRH) was investigated at room temperature. Adsorption of RhB onto TRH was proved by using Fourier-transform infrared spectroscopy. The detail morphology of TRH was investigated by employing scanning electron microscopy. The effect of operational factors on the percentage removal of RhB from wastewater by using TRH and adsorption capacity was revealed. The percentage removal of RhB from wastewater was increased with mass of TRH, pH and contact time, whereas declined with temperature and initial concentration of RhB dye solution. Moreover, adsorption capacity was increased with contact time, pH and initial concentration RhB dye solution whereas declined with mass of TRH and temperature. Adsorption kinetics was investigated by employing several model including pseudo-first-order, pseudo-second-order, Elovich model, liquid-film diffusion model, modified Freundlich equation and Bangham equation but experimental data fitted well to pseudo- second- order kinetics (R-2 = 0.997). Experimental data was also explored by using several adsorption isotherms but fitted well to Langmuir adsorption isotherm (R-2 = 0.996). Moreover, the value of mean adsorption energy (E = 1.03 kJ/mol) exhibited that adsorption of RhB onto TRH was physical adsorption process. Adsorption thermodynamics study exhibited that adsorption of RhB from wastewater onto TRH was exothermic and non- spontaneous process.