UC Santa Cruz

A large variety of pharmaceutical classes of drugs (NSAIDs, Beta-blockers, Statins, and others) have been found in aqueous environments at ng/L to μg/L concentrations. While these concentrations are seemingly low in comparison to most of the effective doses for pharmaceuticals, very little is known about chronic low level exposure to these drugs in humans or other animals. Humans will be exposed through their drinking water or bioaccumulation in the food chain. For animals, fish are the main concern for pollutants in an aqueous environment. Millions of people rely on fish heavy diets and could be exposed low levels of a variety of pharmaceuticals by eating. Therefore, it is important to develop materials for sequestering these pollutants. One of the most common methods for pollutant trapping is via anion exchange. Most anion exchange mediums are designed for cationic exchange. However, a large amount of these pharmaceutical wastes exist in an anionic form. A variety of materials exhibit anion exchange properties, such as, organically modified resins, layered double hydroxides (LDHs), or metal organic frameworks (MOFs). We are investigating a new class of cationic materials called layered metal hydroxides (LMHs). They consist of cationic inorganic layers balanced by a variety of organic and inorganic anions. The inorganic layers are exceptionally thermally and chemically stable making them ideal candidates for coupling to raw industrial waste waters. It is highly beneficial to trap the pollution at the source while it is still concentrated, rather than when it has diluted in the environment.

Slug-27 an erbium based LMH with the chemical formula Er12(OH)29(H2O)5(O3SCH2CH2SO3)3.5*4H2O. The +7 charge in the cationic layer is balanced by 3.5 divalent ethanedisulfonate anions. Full anion exchange for a series of α,ω-dicarboxylates is achieved in a 24 hour period at room temperature and shown by a variety of spectroscopic methods. Slug-27 also exhibits interesting rehydration properties after being heated to temperatures of 200˚ C and greater. Future studies on Slug-27 will include the effect of dehydration/rehydration on the exchange properties.