Techno-Economic Comparison of Chromium (VI) Removal from Tannery Wastewater using Graphene Oxide Versus Magnesium Oxide

Author : Moreno, Jenny Lou A.
Major Adviser : Gatdula, Kristel M.
Committee Members : Guerrero, Gino Apollo M.; Bataller, Butch G.
Year : 2021
Month : January
Type : Thesis
Degree: BS
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Techno-economic comparison of chromium (VI) removal from tannery wastewater using graphene oxide (GO) and magnesium oxide (MgO) were done. The effect of operating conditions (adsorbent dosage, contact time, pH) on the Cr (VI) removal efficiency were first compared for the two adsorbents. According to Magana (2019), the highest percent removal of Cr (VI) for GO was observed at pH 3, 5 g/L adsorbent dosage, and 180 minutes contact time with 89.51% percent removal. For MgO, the highest percent removal of Cr (VI) of 81.25% was observed at pH 9, 0.8 g/L adsorbent dosage, and 280 minutes contact time (Dargahi et al., 2015). Both adsorbents obtained their highest percent removal at the highest adsorbent dosage used with GO having the higher adsorbent dosage needed to achieve it highest removal efficiency. For the effect of contact time, both adsorbents showed an increase in the removal percent as the contact time increases, which resulted to MgO having a longer contact time of 280 minutes. For the effect of pH, opposing results were observed for the adsorbents with GO having its highest removal efficiency at a lower pH while the highest removal efficiency for MgO was observed at a higher pH. Cost estimates were also done to compare the capital cost, materials cost, operating cost and total cost of the adsorbents. The same data from Magana (2019) and Dargahi et al. (2015)  were used as assumptions ffor the comparison. The capital cost estimated for GO and MgO were Php 50.86/m³ and Php 66.20/m³, respectively. For the materials cost, it was estimated that GO has Php 60.47/m³ while MgO only has Php 6.81/m³. For the operating cost, Php 73.23/m³ and Php 21.11/m³ were estimated for GO and MgO, respectively. Lastly, the total cost obtained were Php 124.09/m³ for GO and Php 87.31/m³ for MgO. The capital cost for MgO was found to be higher, while the materials cost, operating cost, and total cost were higher for GO. Process and cost efficiencies were also obtained to determine the better adsorbent to be used. The process cycle efficiency obtained were 86.51% and 88.30% for GO and MgO, respectively. For the cost efficiency, the payback period were estimated to be 1.99 years for GO and 0.85 year for MgO. It was found that MgO is the better adsorbent to be used in Cr (VI) removal from tannery wastewater.

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