SESHA 2003 Symposium - Abstract

Sustainable treatment of HF wastewater from semiconductor Industry using a Crystalactor

Van den Broeck, Kristel; Van Hoornick, Nausikaa; Van Hoeymissen, Jan
(IMEC, Leuven, Belgium)

Sustainable treatment of HF wastewater from semiconductor Industry using a Crystalactor K. Van den Broeck, N. Van Hoornick, J. Van Hoeymissen. Imec, Kapeldreef 75, 3001 Heverlee, Belgium. Within the semiconductor industry, large volumes of HF containing wastewaters need to be treated. The crystalactor is a technique that makes it possible to treat HF wastewater with virtually no waste production. A method based on crystallization of CaF2 on sand particles in a fluidized bed reactor was assessed for the first time with real wastewater originating from a semiconductor prototyping line. Several process parameters were investigated such as influent fluoride concentration, calcium reagent excess, pH, single versus multiple calcium reagent dosing,... It can be concluded that the performance of the CrystalactorŽ is greatly depended on the initial concentrations of calcium and fluoride at the bottom of the reactor (referred to as local saturation). The original hardware design was changed from a single reagent dosing to a multiple reagent dosing to prevent too high local supersaturation values of fluoride and calcium and thus obtain higher CaF2 crystallization efficiencies. Fluoride loads up to 7 kg/m2h were still possible with multiple reagent dosing, compared to a maximum treatable load of 3.5 kg/m2h for single reagent dose. Additionally, an alternative post-treatment process based on replacement of calcite by fluorite in a granular calcite column was tested out.

[abstract as .pdf]