Adsorption of Reactive Red 195 dye from industrial wastewater by dried soybean leaves modified with acetic acid

This study aims mainly to use the soybean leaves (SL), agricultural wastes, as a new low-cost adsorbent for Reactive Red 195 (RR195) dye removal from aqueous solutions. The dried SL was chemically modified by acetic acid (AA) to improve its adsorption capacity. The adsorbent (AA-SL) was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The effects of operational parameters such as contact time, pH, adsorbent dose, initial dye concentration, and temperature were investigated in batch experiments. Adsorption kinetics, isotherm, and thermodynamic of AA-SL have been studied. The AA-SL structure was found to be irregular and porous. FTIR revealed that the surface of AA-SL was abundant in various functional groups. The solution pH strongly affects RR195 removal efficiency. The highest removal efficiency equal to 97.8% was achieved using a solution pH equal to 1 at 50 degrees C. The removal efficiency was increased by increasing the solution temperature. The adsorption of RR195 was decreased from 15.32 to 2.29 mg g(-1) with increasing the adsorbent dose from 0.25 to 3 g L-1, respectively. Increasing initial dye concentration from 5 to 40 mg L-1 resulted in increasing the adsorption capacity from 2.2 to 9.2 mg g(-1), respectively and decreasing the removal rate from 88% to 45.8%, respectively. The adsorption of RR195 onto AA-SL obeyed Langmuir (R-2 = 0.998) and D-R (R-2 = 0.967) models with a theoretical maximum adsorption capacity of about 12 mg g(-1) at 50 degrees C. The experimental data fitted very well with the pseudo-second-order kinetic (R-2 = 0.991). Thermodynamic studies indicated that the reaction is irreversible and endothermic adsorption. AA-SL, as a low-cost material has the potential to be used as a new alternative adsorbent for the removal of RR195 dye from aqueous solutions.