Parametric Study on the Adsorption of Nitrates from Wastewater Using Activated Carbon and its Recovery by Desorption For Nitrocellulose Production
Author : Barcel, Ranzel Ricko San Pedro
Major Adviser : Carpio, Rowena B.
Committee Members : Capunitan, Jewel A.; Eusebio, Ramon Christian P.
Year : 2019
Month : July
Type : Thesis
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Commercially available activated carbon was used to adsorb nitrates from synthetic and actual wastewater. Equilibrium contact time and effects of adsorbent dose, pH, and initial nitrate concentration were determined. Different adsorption kinetic models (pseudo first-order and pseudo second-order) and adsorption isotherm models (Langmuir and Freundlich) were tested to the data obtained. Results showed that adsorption kinetic follows pseudo second-order with calculated equilibrium concentration of nitrates matching the experimental data. Also, adsorption follows both Langmuir and Freundlich isotherms. Langmuir constants Qₒ and b were calculated at 3.66 mg/g and 0.018 L/mg respectively. Moreover, Freundlich constants K? and 1/n were also calculated at 0.35 and 0.33 respectively. These values were used to calculate the adsorption capacity of activated carbon to nitrates. Parametric study showed that effects of adsorbent dose, initial nitrate concentration, and their interaction were significant. Low and high values of adsorbent dose were used to adsorb and desorb nitrates from actual wastewater. High value (6 g/50 mL adsorbent) adsorbed and desorbed greater amount of nitrates at 332 and 307 mg/L respectively. Desorbed nitrates were further concentrated to 500 mg/L by distillation, the nitrating acid ratio was also adjusted – displacing parts of HNO₃ with the nitrate solution desorbed from activated carbon and was used for the synthesis of nitrocellulose. The nitrocellulose produced was found to contain nitrogen within the industrial standard. This result proves the possibility of recovering nitrate from wastewater as an alternative source of nitrates for various industrial application.
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