Removal of Pb(II), Zn(II) and Cd(II) ions by insolubilized humic acid

Abstract

Abstract Humic acid from Tafila soil in Jordan has been extracted and insolubilized. 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). Using the batch technique, the adsorption of Pb(II), Cd(II), and Zn(II) by INaTAHA was investigated at various pH values (4.00, 5.00, and 6.00) and temperatures (25.0, 35.0, and 45.0oC). 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 hours for each metal ion fitting the pseudo-second-order model. Langmuir, Freundlich, and Dubinin-Radushkevich adsorption isotherms fitted the metal ion uptake characteristics of INaTAHA. 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.