Investigation into an adsorption and electrochemical regeneration process
      for the treatment of two trace level pesticides
Creators: name: Krieger, Lisa
Publisher: name: Lancaster University
Year: 2017

description: 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 asthe
      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.