Environmental Phosphate Pollution Removal Using a Selectively Permeable Molecularly Imprinted Polymer Membrane
The ability to remove a specific component from its environment has immediate and profound applicability on environmental and medical fronts. Currently, filtering devices that can selectively and completely remove environmental phosphate and nitrate do not exist. Present systems are able to achieve level of 1 mg of phosphorus per liter of water and about 80% nitrogen free. The system described below has the potential to reduce contaminant concentrations to any arbitrary level through staging. Phosphorus and nitrogen are major pollutants that enter our water via runoff from sewage plants and farmland. As nitrates increase, they act as plant nutrients and cause an increase in plant growth. As the plant material dies and decomposes, dissolved oxygen levels decrease. An increase in nitrates may be followed by an increase in phosphates. As phosphates increase and the growth of aquatic plants is encouraged, algal blooms can occur. With the increase in algae growth and decomposition, the dissolved oxygen levels will decrease – causing the death of fish and disruption to the ecosystem. Excessive nitrate levels in drinking water are dangerous to children and can result in the "blue baby" syndrome. According to the Environmental Protection Agency, approximately 40 percent of the Nation's waters still do not meet water quality goals and about half of the Nation's 2000 major watersheds have water quality problems. It is also not possible to remove only the excess iron from the blood of patients with extremely high iron levels, such as suffers of Iron Overload Disease, Hemochromatosis and iron overdose. Treatments include replacement of the fatally iron rich blood by transfusion or chelation therapy. Important electrolytes are lost and introduce additional problems.
The Johns Hopkins University Applied Physics Laboratory has developed filters with selectively permeable molecularly imprinted polymers that are capable of sequestering only targeted molecules such as nitrates, phosphates and iron. These membranes would allow the selective recovery of identified molecules from waste solutions, environmental waters and blood. The captured molecules may be re-used by farmers and industry. Molecular imprinting is a process of making selective recognition sites in synthetic polymers. The process employs a target molecule as a template. The template is surrounded by molecular compliments, which adds stability and improved permeability. Removal of the template leaves behind cavities that exhibit enhanced affinity for rebinding to the target molecule. Various solvent reactions are employed to remove the bound substance when the filter is saturated. At this point, the filter may be reused as may the element that was collected. The membrane can be used as a part of a counter-current flowing extraction system that can be staged to achieve extremely low levels of contamination. The JHU/APL Selectively Permeable Molecularly Imprinted Polymer Membranes for Nitrates and Phosphates are applicable to any water filtration facility. The membrane that selects and filters iron from the blood could be employed in conjunction with transfusion devices. The filtered blood would then be returned to the patient, eliminating the need for additional blood stores.
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