Preparation, Characterization And Applications Of Multi-Functional Iron Oxides-Impregnated Activated Carbon Materials

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Date
2016-03
Authors
Shah, Irfan
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Universiti Sains Malaysia
Abstract
This study was conducted to investigate the preparation, characterization and different applications of iron oxides-impregnated activated carbon materials (FeACs). The surface of activated carbon (AC) was initially oxidized by using potassium permanganate (KMnO4) followed by the iron impregnation using ferrous sulphate (FeSO4.7H2O) as iron precursor using different molar ratios of the oxidizing agent to the iron precursor to examine the impact of iron impregnation on the physicochemical characteristics of the newly prepared carbon materials. Various characterization techniques such as surface area, SEM, EDX, TEM, HRTEM, SAED, XRD, FTIR, CHN, TCC, TG/DTA, XPS, VSM, TPR/TPD and pHpzc analyses were carried out. The surface impregnation of AC varies the surface area as well as the porosity of the newly prepared materials to a great extent. It depicted an increase in the surface area up to 1640 m2/g for modified AC having molar ratio 0.1 KMnO4 : 0.1 FeSO4.7H2O (B), which was comparatively higher than the raw AC (1094 m2/g). Modified AC having molar ratio 1 KMnO4 : 1 FeSO4.7H2O (E), however, shows a decrease in surface area to 543 m2/g and the highest pore diameter (5.49 nm) as compared to all other materials. Surface morphology of the iron-impregnated materials was nonuniform and depicted the iron particles penetration on the surface and the pores of AC. XRD pattern revealed the presence of iron oxide in the form of Fe2O3 and Fe3O4 in the iron-modified materials. Besides the increased in the surface functional groups, the iron-impregnated materials have shown magnetic character as revealed from VSM analyses. In addition, TPR/TPD results reveal the potential application of FeAC material as heterogeneous catalyst. The iron impregnation of AC also resulted in a drastic change in the pHpzc of the modified materials compared to the AC. The prepared materials were investigated for the adsorption of Methylene Blue (MB) as a model dye. MB removal capacity of AC and E was examined using various parameters such as pH, adsorbent dosage, shaking speed, temperature, initial concentration of dye, contact time and the ionic strength. The MB removal increased with the increase in pH and the dye removal efficiency reached 89 and 95 % for AC and E, respectively. However, MB removal efficiency of E reached 98 % using only 0.2 g, while the similar efficiency was observed by AC at higher AC dosage (1 g). The shaking speed did not show any drastic changes in the MB removal above 400 rpm. Meanwhile, the temperature effect study revealed that MB adsorption on AC and E was exothermic and Langmuir isotherm model was the best to explain the reaction mechanism. In addition, the kinetics studies demonstrated that pseudosecond order kinetic model was the best model fitted to the data analyzed. The regeneration of the spent adsorbent E was successfully applied up to 10 consecutive cycles without any significant loss in its efficiency (≈ 98 %). Another application of the iron-impregnated AC materials is in the catalytic conversion of waste cooking oil (WCO) into biodiesel following the esterification and transesterification. The catalytic potential of E was found the best among all materials with FAME yield of 78 %. In addition, the reusability of E was also evaluated and the Fe modified AC shows consistently high FAME yield, up to 75–78 %, for the first three cycles and reduced to below 50 % in the sixth cycle.
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Carbon materials
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