Novolac is widely used as the primary solid component of most photoresists in semiconductor and microelectronic devices. In this study, novolac resins were prepared by condensation of 35% formaldehyde with phenolic compounds such as m-/p-cresol, 2,5-dimethylphenol and bisphenol A in the presence of oxalic acid as catalyst. The average molecular weight (Mw) of these novolac resins has been varied on the changing of mixing ratio of m-/p-cresol/2,5-dimethylphenol/bisphenol A or formaldehyde/phenolic compound. Also, thermal properties of novolac were observed by TGA.

The photocatalytic degradation of methylene blue(MB) was investigated using TiO2 as photocatalyst and UV radiation. TiO2 supported with activated carbon(AC) was prepared by SOL-GEL method and depended on several parameters such as the mass ratio of TiO2/AC, pH and experimental time. The presence of the anatase and rutile crystal phase was determined by XRD analyses of the prepared TiO2. The degradation of MB with TiO2/AC was about 20% higher than that of AC alone. A variation of photodegradation was negligible under UV radiation conditions ( ≥ 40W). It was experimentally showed that the photodegradation rate was increased with increasing the amount of photocatalyst. The optimal catalyst was prepared by impregmation of 5wt%-TiO2 with AC and was calcined at 300℃, and showed about 99% removal efficiency for 3hrs.