DTPA and EGTA as FE(III) complexing agents for enhancing uv/persulfate advanced oxidation process in aqueous sulfamethazine removal / Ng Kuan Aeng

Ng , Kuan Aeng (2023) DTPA and EGTA as FE(III) complexing agents for enhancing uv/persulfate advanced oxidation process in aqueous sulfamethazine removal / Ng Kuan Aeng. Masters thesis, Universiti Malaya.

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Abstract

In recent years, the pollution of pharmaceuticals in the environment has become a growing concern due to their potentially harmful effects on living organisms. Exposure to these pharmaceutically active contaminants has been linked to diverse health consequences. One of the most important point sources is the wastewater treatment plants which are generally not designed to remove such emerging compounds. In this context, a more promising way to treat pharmaceuticals in wastewater is through advanced oxidation processes (AOPs). Fe(II) is one of the frequently used environmentally friendly catalysts in AOPs. However, Fe(II) can be oxidized easily into inactive Fe(III) hydroxide. Consequently, a strategy to produce water-soluble Fe(III) complexes has been proposed to generate Fe(II) in situ during water treatment. When exposed to UV irradiation, these Fe(III) complexes can release Fe(II), which can catalyze the AOPs. So far, ethylenediamine-N,N-disuccinic acid (EDDS), is one of the well-known ligands used to produce water-soluble Fe(III) complex for AOPs. Incorporating water-soluble Fe(III)-EDDS in UV and sunlight-driven AOPs is an effective method for treating organic pollutants in water. However, EDDS is not cost-efficient for water treatment, and cost may limit its application in large-scale water treatment. Therefore, this study explored the potential of diethylenetriaminepentaacetic acid (DTPA) and ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) as an alternative to EDDS. In this study, Fe(III)-DTPA and Fe(III)-EGTA complexes were prepared and employed as catalysts to enhance the performance of UV-activated persulfate (UV/PS) in sulfamethazine removal. The synthesized Fe(III)-DTPA and Fe(III)-EGTA catalysts were characterized using UV-Vis and FTIR spectroscopy. The screening experiment showed that both Fe(III)-DTPA and Fe(III)-EGTA could significantly improve the percentage removal of sulfamethazine in UV/PS, and their performance was comparable with Fe(III)-EDDS. Based on the results, Fe(III)-DTPA released the highest concentration of Fe(II), followed by Fe(III)-EDDS and Fe(III)-EGTA. The optimum ratio of persulfate concentration to the concentration of Fe(III)-DTPA and Fe(III)-EGTA were found to be 100:1 and 100:2.5, respectively. Under the optimized condition obtained using respond surface methodology, the predicted percentage of sulfamethazine removal was ~99% for Fe(III)-DTPA and Fe(III)-EGTA which is similar to Fe(III)-EDDS catalysts. In the experiment, the mean percentage removal of sulfamethazine in the selected real water samples ranged from 93.6 to 99.6%, which is in range with the predicted value. These results suggested that both Fe(III)-DTPA and Fe(III)-EGTA are cost-efficient alternatives to the well-known Fe(III)-EDDS.

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