Removal mechanism of typical trace organic pollutants in the production of electronic ultrapure water

Based on a 12-inch semiconductor ultrapure water pilot line, the total organic carbon (TOC) removal process and the molecular weight distribution of organic matter in the ultrapure water system were tracked and measured. The effects of irradiation intensity, hydraulic retention time, and molecular bonding energy of organic matter on the removal of typical trace organic pollutants from water were investigated in a TOC-UV unit. The results showed that the two-stage reverse osmosis (RO) system removed 98.5% of the TOC and the water producted by the first stage RO contained 97.3% neutral small molecules with molecular weights below 350 u. Within a certain range to strengthen irradiation intensity and hydraulic residence time in the TOC-UV unit could effectively improve the removal performance of small molecules of organic matter. The best TOC removal effect was achieved when the 185 nm ultraviolet lamp with an irradiation intensity of 2.46 mW/cm2 was selected, and the best removal efficiency was achieved when the retention time was 40 s. The degradation effect of UV on organic matter was significantly affected by the bond energy of the organic pollutants. For low molecular organic matter with high bond energy, such as urea (728 kJ/mol), its removal rate by TOC-UV was low.