9 Conclusions and Future Recommendations
9.2 Future Recommendations
9.2.1 Batch Adsorption Studies
The batch adsorption studies discussed in this dissertation were conducted at concentrations levels that are well in excess of expected environmental levels. These concentration levels were selected in order to determine adsorption maxima (Cmax) for
the selected compounds with Oasis HLB. Batch adsorption studies conducted with analytes at expected environmental concentrations may provide further information regarding the interaction of the selected analytes with the sorbent. It should be noted, however, that the molecular modelling work still confirms adsorption of the analytes on the sorbent can occur at low concentrations.
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Additionally, it is recommended that further batch adsorption studies be conducted, both with a broader range of analytes and sorbents so as to determine what impact other analyte and sorbent functionalities have on the analyte/sorbent interactions.
Ideally, adsorption studies would be conducted using analytes with a diverse array of functional groups and physicochemical properties; first as single batch adsorption studies followed by multiple component batch adsorption studies. As the POCIS device is likely to encounter a number of different compounds when deployed in atypical aquatic environment, it would be of interest to know if compounds that have a higher affinity for the sorbent (as determined by the initial batch adsorption study) preferentially interacts with the sorbent during the multi-component batch adsorption study.
9.2.2 Molecular Modelling
Whilst the molecular modelling studies detailed in this dissertation provided some useful insights into the interactions between the selected analytes and the sorbent, a degree of automation would greatly improve the process of identifying different possible interaction geometries. This process could also include initial low level optimisation of the resulting complexes (e.g. semi empirical methods) so as to keep computational costs down. Once the initial optimisation process had taken place, energetically favourable complexes could then be selected for further optimisation at a higher level (e.g. hybrid DFT methods such as utilised in this work).
Along with conducting further batch adsorption studies with differing analytes and sorbent types, it is also recommended that corresponding hybrid-DFT studies should also be conducted in order to elucidate the molecular interactions taking place between these additional analytes and sorbents.
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9.2.3 Chlorinated OPFR POCIS Calibration Studies
As the calibration study presented in this dissertation is limited to a single flow through calibration study, future studies involving the use of different water flow rates and water temperatures and salinity levels are required in order to determine the impact that these environmental factors have on the uptake of the chlorinated OPFRs into the standard POCIS.
Furthermore, ideally an in-situ calibration should be conducted to determine the sampling rate of chlorinated OPFR compounds under environmentally relevant conditions. This would help to further validate the use of the standard POCIS as a sampling device for these compounds.
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