Research On Synergistic Degradation Mechanism And Application Of Laser Cavitation/Activated Carbon Fiber

The organic wastewater treatment technology with high efficiency and environmental protection is the key research object in the field of wastewater treatment recently.The fast-developing industry makes the industrial wastewater containing organic pollutants increase,which poses a more serious threat to the environment and water resources protection.With current wastewater treatment technologies,some conventional technologies have been able to treat inorganic wastewater with simple composition and low concentration,but the more harmful organic wastewater still lacks economic,feasible,efficient and environmentally friendly treatment technology.As an advanced treatment technology,cavitation technology has significant advantages in the degradation of organic wastewater,but its degradation efficiency is low.The activated carbon fiber adsorption method can quickly treat organic wastewater,but the adsorption capacity of activated carbon fiber is limited,and it will lose its activity after adsorption,making it difficult to reactivate.In this paper,a method of laser cavitation/activated carbon fiber synergistic degradation of organic wastewater was proposed.Inactive or deactivated carbon fiber was activated by laser cavitation to adsorb organic wastewater.Finally,the organic wastewater was deeply degraded by laser cavitation and regenerated activated carbon fiber synergistic degradation.The synergistic degradation mechanism and application of laser cavitation/activation carbon fiber were studied.Laser cavitation and shock wave characteristics were measured to analyze the mechanism of laser cavitation degradation by designing experiments.The characteristics of hydroxyl radicals generated in the laser cavitation process were studied,and the influence of the p H value of the solution on the concentration of free radicals was analyzed.Surface morphology change law was tested to analyze the adsorption and degradation mechanism of activated carbon fibers.The synergistic degradation mechanism of carbon fiber by laser cavitation/activation was discussed based on the results of multiple experiments.Methylene blue was selected as an organic wastewater simulant to design experiments to compare the degradation effects of the single method and the synergistic method.The key factors influencing the degradation effect of the synergistic method were obtained.The specific research contents are as follows:(1)Based on the theory of laser cavitation,according to the thermal,chemical and mechanical effects produced by laser cavitation,the principle of laser cavitation degradation and the mechanism of laser cavitation activation of carbon fibers were described,and the theory of adsorption and degradation of activated carbon fibers was introduced to reveal the synergistic degradation mechanism of laser cavitation/activated carbon fibers.The light field on the surface of the carbon fiber material under the action of laser cavitation was simulated,and the local field enhancement effect generated on the surface of the carbon fiber was studied.(2)The effects of laser cavitation were studied,which the laser breakdown and laser cavitation conditions were captured by a high-speed camera.The variation of cavitation effect intensity with laser energy was obtained.The shock wave signal during laser cavitation was detected by optical fiber hydrophone.The signals of plasma shock wave and cavitation collapse shock wave were detected,which the corresponding period of cavitation pulsation was basically consistent with that of laser-induced cavitation pulsation.The chemical effect of laser cavitation was studied by spectrophotometry,and it was found that hydroxyl radicals were generated during laser cavitation.The concentration was positively correlated with laser energy and cavitation time within a certain range,and was affected by the p H value of the solution.It was found that laser cavitation could change the surface morphology of carbon fibers and form micro/nano structures to activate carbon fibers by use scanning electron microscopy.The more times of laser cavitation,the more micro/nano structures and the larger specific surface area.Carbon fibers activated by laser cavitation are timesensitive and deactivated slowly with time increasing.(3)The synergistic degradation mechanism of laser cavitation/activation carbon fiber was revealed.It is found that laser cavitation can induce thermal effect to degrade organic pollutants and stimulate the activation of carbon fibers.The shock wave and microjet generated by laser cavitation break the carbon bonds on the organic molecules and change the surface structure of carbon fibers to activate them.Laser cavitation generates free radicals to degrade organic wastewater and introduces oxygencontaining functional groups on the surface of carbon fiber to improve its activity.The mechanical effect of laser cavitation improves the mass transfer efficiency in the liquid,and the adsorption process of activated carbon fiber accelerates the rate of laser cavitation degradation.The two complement each other and have a synergistic effect on the degradation of organic wastewater.(4)The degradation effect of single method and synergistic method on methylene blue organic wastewater was studied through experiments,and the key factors affecting the degradation effect of synergistic method were obtained.The results show that the laser cavitation/activated carbon fiber synergistic degradation method has significant advantages in the treatment of organic wastewater,with a faster degradation rate and a higher degradation rate.When the laser energy is 48 m J,the laser cavitation/activated carbon fiber can degrade for 30 minutes in different concentrations of methylene blue solution with the degradation rate of more than 90%.The laser cavitation degradation method and the activated carbon fiber adsorption degradation method have a low degradation rate and are difficult to degrade high-concentration organic wastewater.With the increase of laser energy,the degradation effect of laser cavitation/activated carbon fiber was enhanced.High concentration of methylene blue solution requires high laser energy to achieve good degradation effect.