Hanafiah, Siti Fatimah Md
(2022)
Adsorption Of Chromium, Cadmium and Manganese Ions Using Nanomagnetic Alumina Composites From An Aqueous Solution.
Masters thesis, Universiti Sains Malaysia.
Abstract
The discharge of chromium (Cr), cadmium (Cd) and manganese (Mn) effluents from industries may cause serious environmental effect on aquatic life and human due to their toxicity and harmful nature. Hence, the removal of these heavy metals from an aquatic system is very crucial. This study aimed to remove Cr, Cd, and Mn ions from an aqueous solution using nanomagnetic alumina (Al) composites using two different methods, namely physical mixing (PM) and chemical precipitation (CP). Nanomagnetic Al composites which were nickel loaded alumina (NiAl), cobalt loaded alumina (CoAl) and iron-loaded alumina (FeAl) were applied in the adsorption process to compare their efficiencies towards Cr, Cd, and Mn ions. The adsorption of Cr, Cd and Mn ions were conducted in a batch system under varying initial pH (3-11), adsorbent dosage (0.01-0.06 g), initial concentration (10-100 mg L-1) and temperature (40-50℃). The adsorbents were characterised using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), Brunauer–Emmett–Teller (BET), X-Ray Photoelectron Spectroscopy (XPS) and Electron Spin Resonance (ESR). The results showed that the nanomagnetic Al composite produced through PM method has a higher adsorption capacity as compared to the CP method. The adsorptivity of those adsorbents toward Cr, Cd and Mn ions was in the following order: FeAl > CoAl > NiAl> Al. FeAl was chosen as the best adsorbent. The characterisation result revealed that adsorptivity was significantly related to the interaction between Al frameworks with the metal composites which increase the magnetism properties especially for FeAl. XRD, FTIR, XPS and ESR analysis explained the occurrence of dealumination of Al and isomorphous substitution of each metal. FeAl was able to remove Cr, Cd and Mn ions with the adsorption capacity of 500.0 mg g-1, 285.7 mg g-1 and 3.883 mg g-1 respectively from an aqueous solution containing initial concentration of 25 mg L-1 at pH7 when using 0.05 g adsorbent, at 30℃ (Cd, Mn) and 40℃ (Cr). The best model for explaining the adsorption of Cr, Cd and Mn ions was the Langmuir model. The kinetics was best described by the pseudo-first-order model, while the thermodynamic study indicated that the adsorption was exothermic for Cr and both Cd and Mn were endothermic. However, the favourability of the adsorption was in the order of Cr>Cd>Mn. For all heavy metals ions, the adsorption process supports the non-spontaneous nature of the system.
Actions (login required)
 |
View Item |
