Enhanced removal of Pb(II), Zn(II) and Cd(II) ions by insolubilized humic acid: Characterization and sorption behaviors
Omar Alnasra, Fawwaz I. Khalili, F.A. Alhnafat
Abstract
Humic acid from Tafila soil in Jordan has been extracted and insolubilized to investigate the effectiveness for the adsorption and removal of heavy metal ions (Pb(II), Cd(II), and Zn(II)) from aqueous solutions. Fourier transform infrared spectroscopy, thermal gravimetric analysis, elemental analysis, X-ray diffraction, scanning electron microscopy, and differential scanning calorimetry were used to characterize the sodium form of Insolubilized Tafila Humic Acid (INaTAHA). Evaluating its adsorption capacity under various conditions (pH, temperature), the adsorption of Pb(II), Cd(II), and Zn(II) by INaTAHA was investigated. It was observed that INaTAHA has a maximum uptake as follows: Pb(II) > Zn(II) > Cd(II) and the metal ion uptake increased with pH reaching a peak at pH = 6. Kinetic studies results demonstrated that the maximum uptake level requires an equilibrium time of 24 hr for each metal ion fitting the pseudo-second-order model. The activation parameters Ea, ΔG‡, ΔH‡, and ΔS‡ were also calculated. The findings show that physisorption is the mode of adsorption. Using the column technique, the uptake percent with the metal ions is as follows: Pb(II) > Zn(II) > Cd(II). Using 1.0 M HNO3 produced the best percent recovery for the metal ions according to desorption studies.