Photo (Electro) Chemical Removal Of Organic Pollutants Using A Modified Carbon Nanotube Filter

With the acceleration of the industrialization process,a large amount of organic pollutants are discharged into the water body,leading to serious environmental pollution and ecological poisoning problems.Numerous studies have shown that advanced oxidation techniques can achieve oxidative degradation of organic pollutants by producing strongly oxidizing hydroxyl radicals.Among them,the photocatalytic oxidation technology which can effectively utilize sunlight has been widely concerned because of its strong oxidizing ability,non-selectivity,mild reaction conditions,wide application range and no secondary pollution.However,traditional powder photocatalytic systems mainly have three bottlenecks in practical applications:?1?powder photocatalytic materials are difficult to recycle,?2?photogenerated charge complexes are serious,and?3?traditional photocatalytic systems have limited mass transfer effects.In response to the above shortcomings,this paper has carried out the following research:Based on carbon nanotubes?CNTs?with good conductivity and large surface area,the effective loading of nano-TiO₂ and nano-Ag/AgCl photocatalysts was achieved by polydopamine coupling and continuous deposition photoreduction.At the same time,a continuous streamer?electro?catalytic membrane reaction system was designed to effectively improve the mass transfer effect of the system.The degradation properties of the continuous stream photocatalytic system for the target pollutants were investigated by using methylene blue and tetracycline as model compounds.The results show that the removal efficiency of methylene blue of 10 mg·L^-1 can reach 90%in the continuous flow photocatalytic system with Ag/AgCl CNTs filter at a flow rate of 2.0 mL·min^-1 when continuous photocatalysis is carried out with methylene blue as the model compound,more than 70%higher than the traditional sequencing batch reaction system.The TiO₂-CNTs filter has a decolorization rate of 95%for methylene blue in a continuous flow photocatalytic system with a flow rate of 2 mL·min^-1,which is 72%higher than the conventional system.It shows that the convective mass transfer effect of the continuous flow system is obviously better than the diffusion mass transfer effect of the sequencing batch system.When tetracycline is used as a model compound,the TiO₂-PDA-CNTs-H composite filter is in a continuous flow(1.0 mL·min^-1)photocatalytic system,in photocatalysis,electrocatalysis?2.5 V?and photoelectrocatalysis?2.5?.V)The removal rates of 20 mg·L^-1 tetracycline solution were 7.7%,24.3%,and 49.1%,respectively,showing significant photoelectric synergy.Similarly,the removal rates of the 20 mg·L^-1 tetracycline solution of the TiO₂-Ag-PDA-CNTs-H composite filter were 3.3%,20.6%,and 41.0%,respectively.Taking TiO₂-CNTs filter as an example,the experiment of photocatalytic degradation of methylene blue for three consecutive times showed that the degradation efficiency of methylene blue decreased by only9%,indicating that the modified nanotube film has good stability and photocatalytic activity,and is expected to be industrialized.