Removal of Cu(II) by loofah fibers as a natural and low-cost adsorbent from aqueous solutions

Abstract

As a natural and low-cost material, loofah fibers were applied as an adsorbent to remove Cu(II) from aqueous solutions. The effect of adsorption conditions, such as pH, foreign ions, humic substances (HS), contact time and temperature on the Cu(II) removal, were investigated intensively. The adsorption of Cu(II) on loofah fibers was strongly dependent on pH and foreign ions, and the adsorption of Cu(II) was increased in the presence of humic acid (HA) at pH<8.0 but decreased at pH>8.0. The Langmuir and Freundlich isotherm models were used to simulate the adsorption isotherms. The simulated adsorption isotherms, which were obtained from Langmuir and Freundlich isotherm models, showed that both of the two models were applicable to this system. On the basis of the experimental data, the Langmuir isotherm model could fit it better according to linear correlation coefficient (R2). The optimum kinetics of adsorption was found to fit the pseudo-second-order kinetic model. The values of ∆H° and ∆G° indicated that the adsorption process was exothermic and spontaneous.