Removal of methylene blue from wastewater using fallen leaves as an adsorbent

Abstract

The potential of the fallen leaves of Platanus as a natural biosorbent was investigated for adsorptive removal of methylene blue (MB) from aqueous solutions. Variables, including solution pH, initial MB concentration, biosorbents dose and ionic strength, were investigate to determine their effects on biosorption. The removal rate at pH = 7 is the maximum value (95.23%). The extent of the MB removal increased with initial MB concentration, biosorbent dose and ionic strength. Furthermore, the fallen leaves could be regenerated through the desorption of MB in deionized water and reused to adsorb the dye again. The equilibrium data could be well interpreted by Temkin isotherm followed by Langmuir and Freundlich isotherms. Lagergren first-order, Ho second-order, and Weber and Morris intraparticle model were used to explain the behavior of the adsorbent, and the kinetic data fitted well with Ho second-order model. The values of activation energy were 14.26 kJ/mol, which indicated that MB biosorption onto the leaves was mainly physical. The thermodynamics parameters: ΔG°, ΔH°, and ΔS° were evaluated, which indicated the biosorption was a spontaneous, endothermic process, meanwhile an increase in temperature was advantaged for leaves to adsorb MB. The results of Fourier transform infrared spectroscopy showed that the functional groups hydroxyl (–OH) and carboxyl (–COOH) may be potential biosorption sites for MB dye.