Title: Characterisation of nano-sized particles in chemical mechanical polishing wastewater

Authors: Noor Aina Binti Mohamad Zuki; Norli Ismail; Fatehah Mohd Omar

Addresses: School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia ' School of Industrial Technology, Universiti Sains Malaysia, 11800 Gelugor, Penang, Malaysia ' School of Civil Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang, Malaysia

Abstract: Treatment of chemical mechanical polishing (CMP) wastewater and fluoride-containing wastewater in semiconductor manufacturing are conventionally separated. The combined treatment of these two streams of wastewater was studied in terms of zeta potential and z-average hydrodynamic diameter profiles as a function of pH 2 to 12. Optimum pH for CMP wastewater was at pH 6 with zeta potential value of −10 mV and mean particle size of 180 d.nm. Meanwhile, for fluoride-containing wastewater the optimum pH obtained was at pH 9 with zeta potential of 10 mV and mean particle size of 5,214 d.nm. These two streams were combined together at their respective optimum pH and resulted a zeta potential value of 0.55 mV and mean particle size of 12,590 d.nm. Results indicated that the combined treatment for both polishing and fluoride-containing wastewater were beneficial as a larger flocs of fluorosilicate 26(SiF₆²⁻) was generated without the presence of coagulation chemicals. It is proposed that positively charged particles present in fluoride-containing wastewater become adsorbed on the surface of silica nanoparticles in CMP wastewater in which act as nuclei and enhances flocculation since repulsive force of both wastewater is decreased.

Keywords: semiconductor wastewater; chemical mechanical polishing; CMP; pH; zeta potential; particle size; aggregation; disaggregation.

DOI: 10.1504/IJEE.2019.099996

International Journal of Environmental Engineering, 2019 Vol.10 No.1, pp.33 - 46

Received: 01 Jan 2018
Accepted: 16 Sep 2018
Published online: 03 Jun 2019 *

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