Investigation into an adsorption and electrochemical regeneration process for the treatment of two trace level pesticides

Krieger, Lisa (2017) Investigation into an adsorption and electrochemical regeneration process for the treatment of two trace level pesticides. Masters thesis, UNSPECIFIED.

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Abstract

The presence of organic micro-pollutants in aquatic systems and drinking water is of concern in most highly populated regions of the planet. Extensive surveys of major river systems in Europe and the United States have measured a wide array of organic contaminants including industrial chemicals, surfactants, pharmaceuticals and pesticides. The European Union’s Water Framework Directive – aimed at achieving good environmental quality of surface waters at the catchment level - has a series of environmental quality standards that must not be exceeded for a wide range of water pollutants, including pesticides and other organic contaminants. To meet these demands and challenges of higher water quality, Arvia Technology Ltd. have developed a novel water treatment process known as the Arvia™ Process. The Arvia Process combines adsorption with in-situ electrochemical regeneration which leads to the electrochemical oxidation of the adsorbed organic contaminant. The aim of the present study was to test the individual stages of the Arvia Process, namely adsorption and electrochemical regeneration of the proprietary adsorbent Nyex™, for its ability to remove and treat two current-use pesticides, atrazine and pirimicarb, at trace level concentrations. Initial adsorption kinetic and isotherm studies indicated that the adsorbent, Nyex, could successfully remove both atrazine and pirimicarb when dissolved in water. This indicated that atrazine and pirimicarb could therefore potentially be removed using a combined adsorption and electrochemical process. During electrochemical regeneration of the adsorbent, ideally the adsorbed organic contaminant should remain adsorbed onto the sorbent and be fully oxidised to H2O, CO2 and inorganic ions. However, in the present study during electrochemical regeneration, adsorbate molecules desorbed from the Nyex surface and were subsequently transferred back into solution. However, some treatment was observed as evidenced by the formation of degradation products. Two atrazine degradation products were formed and were tentatively identified as deethyl-deisopropyl-atrazine and 4-ethylimino-6-isopropylamino-s-triazine. One pirimicarb degradation product was formed and was tentatively identified as 2-methylamino-5,6-dimethylpyrimidin-4-yl-dimethylcarbamate. Since there were only slight modifications to the structures of the original parent compounds, this indicated that the compounds were only partially oxidised. This may be the result of indirect electrochemical oxidation in the liquid phase as during this study there was desorption of the pollutants. This investigation revealed that under the experimental conditions used in the present study electrochemical oxidation could not effectively remove and treat atrazine and pirimicarb at trace level concentrations. The experimental conditions used were likely responsible for the desorption of atrazine and pirimicarb thereby making the assessment of the performance of the system difficult. Future work should consider investigating the present methods under other experimental conditions to improve the treatment and destruction of atrazine and pirimicarb.

Item Type:
Thesis (Masters)
Subjects:
ID Code:
89072
Deposited By:
Deposited On:
06 Dec 2017 12:32
Refereed?:
No
Published?:
Unpublished
Last Modified:
11 Sep 2020 07:07