Electrocoagulation and electrodecantation were investigated as methods to concentrate solids from the dilute suspensions typically encountered as waste streams of chemical mechanical polishing operations. Model silica and alumina suspension containing particles of approximately 200 nm in diameter were studied. 3 L batches of suspension were subjected to electric fields of several volts per centimeter and monitored for particle removal. Electrodecantation was shown to clarify charge stabilized, low conductivity suspensions (20 mS/cm) without modifying the mean particle size or surface-charge characteristics. The technique is thus suited to circumstances where recycle and reuse of particles is desirable, though the results also show that Joule heating may disrupt the decantation process and so must be controlled in order to apply the method to higher conductivity suspensions. Electrocoagulation was shown to effectively destabilize and clarify high conductivity suspensions (1300 μS/cm), producing aggregates several-fold larger than the primary particle size, which subsequently sedimented from suspension. Intermittent application of the electric field was found to yield superior rates of particle removal while consuming substantially less electrical power (ca. 1 Wh/L of clear solution).
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry