Kinetics of Decomposition of Polyethylene Glycol in Electroplating Solution by Ozonation with UV Radiation

The kinetics of the ozonation of polyethylene glycol (PEG) with ultraviolet (UV) radiation in the acid-based electroplating solution of the printed wiring board industry is studied. The substrate prescription of a typical electroplating solution is with pH of 0.18-0.42, [CuSO4·5H2O] of 200 g/L, [H2SO4] of 60 g/L, and [Cl-] of 0.03 g/L. Certainly, the discarded electroplating solution is hard to treat with the common chemical and biological processes because of its acidic and metallic compositions. In addition, it contains valuable substances suitable for recovery and reutilization. One of the most important processes for reviving it is to remove the aged organic additives such as PEG. A two-step reaction mechanism in terms of ozone A and total organic carbon is proposed to express the reaction kinetics of PEG ozonation with UV radiation with intensity [Iuv]. The initial concentration of PEG is 30 mg/L, according to the recipe of a typical electroplating solution, which is equivalent to total organic carbon of 16.3 mg/L. The reaction rate r expressions of the concentrations of the liquid phase ozone CALb, PEG CBLb, and intermediates CILb are rA (=dCALb/dt) = -(kAm + kI[Iuv])CALb - (kR1 + kRI1 [Iuv])CALbCBLb - (kR2 + kRI2[Iuv])CALbCILb, rB (=dCBLb/dt) = -(kR1 + kRI1[Iuv])CALbCBLb, rint (=dCILb/dt) = (kR1 + kRI1[Iuv])CALbCBLb - (kR2 + kRI2[Iuv])CALbCILb, with kAm = 0.0036 s-1, kI = 4.654 × 10-5s-1/(Wm-2), kR1 = 13.525 M-1s-1, kR2 = 0.751 M-1s-1, kRI1 = 0.683 M-1s-1/(Wm-2), and kRI2 = 0.042 M-1s-1/(Wm-2). These reaction kinetic expressions are useful and referable for the proper design of an ozonation system with UV radiation for the treatment of PEG in the printed wiring board electroplating solution.