Parametric Study on The Removal of Hexavalent Chromium from Synthetic Solution and COD Wastewater by Adsorption Using Rice Straw-Based Activated Carbon
Author : Menor, Christine Joy Angeles
Major Adviser : Migo-Sumagang, Maria Victoria P.
Committee Members : Migo, Veronica P.; Eusebio, Ramon Christian P.
Year : 2019
Month : June
Type : Thesis
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Hexavalent Chromium (Cr (VI)) removal from COD wastewater via adsorption using rice straw-based activated carbon (RSAC) was employed in this study. The RSAC was produced using phosphoric acid as chemical agent, and through thermal activation at 750° C. The removal efficiency of Cr (VI) using alkali precipitation was obtained at 99.63% but the residual Cr (VI) 2.0835 ppm was still above environmental standards (0.1 ppm) thus, further treatment using RSAC was tested. The equilibrium time for adsorption obtained was 90 minutes. The effect of different parameters, such as adsorbent dose (0.1 to 0.5 g RSAC/ 30 mL Cr (VI) solution) and contact time (30 to 150 minutes), were studied. Results show that both parameters have positive direct relationship with the percentage removal of Cr (VI). The percentage removal of Cr (VI) in COD wastewater was 14.10 % which gave a higher final concentration of Cr (VI) than expected. Presence of Ag and Hg in COD wastewater might affect the percentage removal of Cr (VI) using RSAC. The RSAC was also subjected to SEM and XRF analyses, and the SEM micrographs showed that the surface of RSAC have widespread external pores, while the XRF analysis shows that RSAC consists 57.16 carbon. The equilibrium data was also fitted using different isotherms, and was found out that Langmuir gave the best fit, with an R2 value of 0.9432, and a maximum adsorption capacity, qmax, of 13.19 mg Cr (VI) per g RSAC. The separation factor, RL, value of 0.2205 indicates that the adsorption of Cr (VI) onto RSAC is favorable. Freundlich isotherm had the least error among the isotherms with the RMES, AARE and X2, value of 0.0007, 0.1251 and 0.0003, respectively.
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