Study On Spray Reactor For Photocatalytic Degradation Of Gas Phase And Liquid Phase Organic Pollutants Using By Nano-TiO₂

Titanium dioxide has received more and more attention in the field of photocatalysis and environmental protection due to its excellent physical and chemical properties.In this paper,a photodegradable multi-phase organic pollutant TiO₂ spray reactor is designed and manufactured for the treatment of waste gas and waste water from chemical and pharmaceutical plants,and the gas and liquid organic pollutants are simulated by xylene and cefoxitin respectively to verify the processing efficiency of the reactor.The effect of the concentration of TiO₂,light intensity,pH value,H₂O₂,and other ionic addition on the photodegradation efficiency of organic pollutants is studied.For the cefoxitin degradation,the intermediate products and degradation mechanism are explored.The practical application of the reactor is analyzed.?1?Degradation of xylene gas:when the reactor is equipped with one lamp,the highest degradation rate of 58.49%is received while the concentration of TiO₂ in the suspension is 0.1w%;At the optimal concentration of TiO₂,the optimal degradation rate of 76.33% and 79.36% is respectively achieved while the pH value of suspension is 2 and 10;the optimal degradation rate of92.7%is acquired while the volume ratio of H₂O₂?30%,m/v?to H₂O is 1:50.When the reactor is equipped with four lamps to increase the light intensity,the highest conversion efficiency of 73.16 is achieved while the concentration of TiO₂ is 0.05 w%.At the optimal concentration of TiO₂,the conversion efficiency of xylene is significantly improved at pH=2 and 10 compared with one lamp,reaching 88.6%and 90.2%,respectively.Because the transition probability of TiO₂ is increased at the high UV intensity,lost of active substances are produced;However,the conversion rate is reduced while the volume ratio of H₂O₂?30%,m/v?to H₂O is 1:50 compared with one lamp,only 77.21%.Because the H₂O₂ can be decomposed under the long-time illumination;In the experiment of Fe³⁺addition,the low concentration of Fe³⁺can promote the conversion rate up to 91.4%,and the concentration of Fe³⁺at this time is 0.001 mol/L.This is because the Fe³⁺is a strong electron trapping agent.However,the conversion rate decreases when the concentration of Fe³⁺continues to increase.This is because high concentration Fe³⁺has a significant absorbance at the electron transition wavelength of TiO₂?384 nm?,which reduces the light intensity.?2?Degradation of cefoxitin:the degradation experiments of cefoxitin are carried out under four lamps.When the concentration of TiO₂ in the suspension is 0.01w%,the optimal conversion rate of cefoxitin is 92.6% within 100 min.At the optimal TiO₂ concentration,the highest degradation efficiency of cefoxitin of 98.6% and 96.6% is achieved at pH=3 and 10,respectively;when the volume ratio of H₂O₂?30%,m/v?to H₂O is 1:40,the optimal degradation rate is 99%.In order to explore its influence mechanism,the intermediate products are analyzed by LC-MS,and the final products are CO₂ and H₂O.In order to accelerate the reaction rate,the effect of the change of pH value on the reaction efficiency during the reaction is studied.It is found that when the pH of the initial suspension is 3,the pH is changed to 10 when the reaction is 40 minutes,and then the pH is changed to 3 when the reaction is 60 minutes,at this condition,the reaction time is reduced by 20%,the complete reaction time is about 80 minutes.