Ion transport in natural and engineered membranes: implications for pollutant analysis, toxicity and remediation

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Water contains dissolved ions, which are charged atoms or molecules. For survival organisms need to be able to transport some beneficial ions into their cells, and dispose of toxic ones. It is the biological membranes in aquatic organisms that interface with water and control the transport of dissolved ions to/from the interior of cells. The normal transport across membranes ensures healthy organisms, but if this transport is interrupted toxicity can result. Similarly, engineered membranes can be used to clean waters by excluding pollutants. Understanding the transport of ions across membranes will allow for appropriate protection of aquatic life, but also experimental insights will allow for engineering of membranes for specific contaminant remediation, or even selective and sensitive detection of contaminant ions. To this end, this research proposal is divided into three parts: toxicity, analysis and remediation. TOXICITY. In earlier work in my lab, gill cells were obtained directly from fish to study metal ion transport. This proposed research program will instead investigate cultured cells from continuous cell lines. There is a suggestion that such cell lines might replace animal testing for the assessment of pollutant toxicity. For such testing to be acceptable it is necessary to assess if cell-line derived cells behave chemically similarly to primary cultures. ANALYSIS. In my lab membranes have been used to construct ion selective electrodes for analysis of specific metal ions. Such electrodes include an ionophore (ion-loving compound) that selectively binds only the metal ion of interest. As a new monitoring tool, I propose to build ion-selective membranes into monitoring devices. Replacing membranes in existing monitoring devices with an ion-selective membrane will remove any ambiguity in what species are measured and could revolutionize membrane-based monitoring methods and allow for their wide-spread acceptance for contaminants monitoring. REMEDIATION. Elevated concentrations of phosphate (a negatively charged ion) in surface waters can cause negative impacts, but if the phosphate can be separated it can be recovered as a valuable fertilizer product. Existing wastewater treatment methods result in a high phosphate sludge. The use of membranes to remove phosphate to generate chemically pure fertilizer from wastewater sludge will be explored. If an electric potential is applied to the sludge, the ions will migrate with negative ions moving to the positive electrode. To ensure that the recovery solution include only phosphate a phosphate selective membrane will be used between the treated solids and the receiving electrode. SUMMARY. The research program will be a combination of fundamental studies and applications and provide great learning and training opportunities as well as generating practical solutions to toxicological, analytical and remediation issues in water management.