Parameter optimization and design aspect for electrocoagulation of silica nano-particles in wafer polishing wastewater.
A systematic procedure has been proposed for the design of a multi-channel, continuous-flow electrocoagulation reactor of mono-polar configuration for the removal of sub-micron particles from wastewater. Using the chemical-mechanical-planarization (CMP) process as the target source of wastewater, a series of laboratory-scale studies were conducted to determine the required operating conditions for the efficient removal of the ultrafine particles. These operating criteria included charge loading (> or = 8 F m(-3)), current density (> or = 5.7 A m(-2)), hydraulic retention time (> or = 60 min), as well as the initially operational pH (7 to approximately 10). Furthermore, a steady-state transport equation with second-order reaction kinetics was employed to describe the rate of coagulation as the rate-limiting factor. The actual kinetic constant determined from the laboratory-scale experiments was approximately 1.2 x 10(-21) m3 s(-1), which was three orders of magnitude smaller than that calculated based on Brownian diffusion during the coagulation. The model was subsequently validated with a series of experiments using a pilot-scale electro-coagulation reactor geometrically similar to the laboratory-scale reactor with nearly twenty times volumetric scale-up.
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Department of Environmental Science, Tunghai University, Taichung-Kan Road, Sec. 3, #181, P.O. 818, Taichung City, Taiwan 407, Republic of China. wden@mail.thu.edu.tw
Huang
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D019149:Bioreactors; D004564:Electrocoagulation; D004566:Electrodes; D004867:Equipment Design; D007700:Kinetics; D036103:Nanotechnology; D012822:Silicon Dioxide / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000295:instrumentation* / Q000379:methods*; D014874:Water Pollutants, Chemical; D018508:Water Purification / Q000295:instrumentation* / Q000379:methods*
D014874:Water Pollutants, Chemical; D012822:Silicon Dioxide