Abstract: TiO2 is a promising photocatalyst, but the limited contact area of liquid-liquid interface and low catalytic efficiency caused by catalysts with large particle size and uneven distribution restrict the practical application. As an effective process intensification equipment, the impinging stream-rotating packed bed (IS-RPB) overcomes the mixing limitation of traditional stirred tank reactor, and provides a micro-mixing environment at the molecular scale for liquid-liquid two phase, which could reduce the particle size and distribution range. Cu/N-TiO2 nanoparticles were successfully prepared by one-step precipitation method using urea as the nitrogen source, titanyl sulfate as the titanium source, copper chloride as the copper source and ammonium hydroxide as the precipitant in an IS-RPB. The particle size of obtained photocatalyst was about 11.40 nm with narrow size-distribution via SEM and TEM. According to XPS, N replaced part of O, and was uniformly dispersed in the TiO2 lattice in the form of interstitial N and substitutional N. Cu replaced part of Ti and existed in the form of Cu2+. The synergistic effect of these two elements forms a new impurity energy level and reduces band gap energy of TiO2 nanoparticles. The specific surface areas of Cu/N-TiO2 are 152.97 m2/g. The influence of the main factors on the degradation rate was studied, the results showed that the removal efficiency could reach 100% under the optimal operating conditions after 2 hours UV light irradiation. The EPR measurement showed that the superoxide radical (O2-·) played a leading role in the degradation process, while the effect of photogenerated holes (h+) and hydroxyl radicals (OH·) were relatively weak.

Key words: Cu/N-TiO2, co-doping, Impinging stream rotating packed bed, photocatalysis, phenol