Industrial Chemistry
Open Access

Abstract

Chemical mechanical planarization (CMP), used heavily in integrated circuit (IC) manufacture, generates copious amounts of waste water high in colloidal and reactive silica, which inhibits on-site reuse in cooling operations and ultra-pure water (UPW) production. Silica, when present in cooling water, can reach solubility limits via evaporation and form impervious scale on heat transfer surfaces that decreases efficiency. Silica in reverse osmosis feed-water inhibits aspirations for high rejection and zero liquid discharge (ZLD) due to scale formation. When subjected to RO at high rejection, silica forms difficult-toremove scale on the membrane concentrate side in the form of glassy patches and communities of aggregate particles. Current methods for silica scale mitigation in industry include dosing with chemical anti scalents or complex operating schemes including ion exchange and large pH swings. This work evaluates the implementation of the common chemical coagulant, FeCl3 and highly insoluble Fe (OH)3 in the removal of silica by coagulation and adsorption mechanisms, respectively. FeCl3 was shown to be optimizable for silica colloid coagulation in CMP waste water via charge neutralization resulting in turbidity <10NTU. Adsorption of reactive silica on Fe (OH)3 using a sequencing batch reactor approach exhibited >90% silica removal for the first adsorption cycle, and increased utilization of adsorbent material for subsequent runs in both CMP waste water and RO concentrate.

Biography

Email: ebaca20@unm.edu