(369c) Removal of Nanoparticles In Semiconductor Manufacturing Effluents Using Porous Media Filtration

The use of engineered nanoparticles in industrial manufacturing has rapidly increased due to their unique electronic, optical, thermal and photoactive properties.  Nanoparticles are used in various fields including textiles, biomedical applications, food and agriculture and semiconductor manufacturing.  Frequently used nanoparticles include titania (TiO₂), which is commonly used in pigments and as a photocatalyst, and silica (SiO₂), which is commonly used as an additive in chemical mechanical planarization (CMP) slurries in semiconductor manufacturing.  Along with the benefits these nanoparticles provide, numerous concerns into the environmental, safety, and health effects of the released particles arise.  Understanding the fundamental interactions of these nanoparticles with typical treatment technologies will allow for improved design of abatement technologies.  Porous media filtration is a common technique used to remove particulates from water.  The simplicity and ubiquity of this process makes it ideal for the removal of nanoparticles in waste streams.  The principles of nanoparticle transport in porous media also relate to the environmental fate of these nanoparticles in soil and ground water.

Custom nanoparticles of silica have been developed which have a fluorescent core and controllable final size.  These particles, due to their fluorescence, can be measured at significantly lower concentrations than in current studies.  Additionally, the ability to control the final size of the particles provides a true comparison of size effects on nanoparticle retention.  A test bed, equipped with real-time and on-line spectrometry, was developed and used to study the dynamics of capture and removal of both TiO₂ and these SiO₂ nanoparticles from wastewater.  Studies were conducted comparing the effect of key solution, nanoparticle, and bed characteristics, including pH, ionic strength, the presence of surfactants, heavy metals, and dispersants, as well as particle and collector sizes.  A process model is under development for analysis of data from this novel experimental method and for elucidating the fundamental parameters affecting nanoparticle retention and removal in such systems.