Study On Sub- And Supercritical Water Treatment Efficiency Of Typical Antibiotic Simulated Wastewater

Antibiotic wastewater has the characteristics of high organic concentration,strong biological toxicity and poor biodegradability,and its effective treatment has always been a difficult and hot issue in the field of water treatment.Environmentally friendly advanced oxidation technology is a commonly used high-efficiency treatment method,and supercritical water treatment technology is an advanced oxidation technology that specializes in the treatment of refractory and toxic and harmful substances.At present,the degradation efficiency and degradation pathway of some antibiotics in sub/super-critical water systems are still unclear.In this paper,taking tetracycline hydrochloride simulated wastewater as an example,the effects of reaction parameters and oxidation coefficient on the degradation and removal efficiency of tetracycline hydrochloride were explored,and the kinetic equation of tetracycline hydrochloride was established,and its possible degradation in the supercritical water gasification/oxidation process was proposed.way.The application of supercritical water oxidation technology in the treatment of other three typical antibiotic simulated wastewater was further explored,and the degradation pathways of different antibiotics in the supercritical water oxidation process were analyzed.The main research results of this paper are as follows:（1）The sub/supercritical water gasification experiment of tetracycline hydrochlo-ride simulated wastewater was carried out,the effect of reaction parameters on the deg-radation process of tetracycline hydrochloride was clarified,and the degradation kinet-ics was analyzed.The increase of reaction temperature,the prolongation of residence time and the decrease of initial concentration all help to improve the removal rate of tetracycline hydrochloride molecules.Under the conditions of initial concentration of1000 mg/L,reaction temperature of 400℃and reaction time of 140 s,the removal rate of tetracycline hydrochloride was 73.87%.The degradation of tetracycline hydrochlo-ride in sub/supercritical water gasification basically conforms to the first-order degra-dation kinetics,and its frequency factor A=0.03 s^-1 and activation energy E_a=6.14k J/mol.Under the condition of supercritical water gasification,the main degradation products of tetracycline hydrochloride are tricyclic and bicyclic products,and the main degradation pathways include the ring-opening reaction and the cracking process of the central benzene ring.（2）The sub/supercritical water oxidation experiment of tetracycline hydrochloride simulated wastewater was carried out,the effect of reaction parameters and oxidation coefficient on the degradation and removal efficiency of tetracycline hydrochloride was clarified,and the degradation kinetics was analyzed.Under different reaction condi-tions,the removal rate of tetracycline hydrochloride molecule was 100%,but it was not completely mineralized.The increase of the reaction temperature,the increase of the oxidation coefficient and the prolongation of the reaction time all help to improve the removal rate of TOC,COD and TN in the simulated wastewater.Under the same conditions,the removal rates of TOC,COD and TN reached the highest,which were90.12%,83.47%and 27.52%,respectively.The degradation of tetracycline hydro-chloride in sub/supercritical water oxidation also basically conformed to the first-order degradation kinetics,and its frequency factor A=6.71 s^-1 and activation energy E_a=25.66k J/mol.The main degradation products of tetracycline hydrochloride under supercriti-cal water oxidation are monocyclic products and linear compounds.The addition of oxidant greatly promotes the ring-opening reaction of benzene ring.（3）The treatment effect of supercritical water oxidation technology on the simu-lated wastewater of three typical antibiotics,namely penicillin,erythromycin and of-loxacin,was explored,and the degradation pathways of the three antibiotics in the su-percritical water oxidation process were clarified.When the initial concentration of an-tibiotics is 1000-5000 mg/L,the reaction temperature is 400℃,the oxidation coeffi-cient is 1,and the reaction time is 15 min,The COD removal rates of penicillin,eryth-romycin and ofloxacin simulated wastewater were 89.57-92.15%,85.16-89.57%and87.78-90.57%,respectively,indicating that Supercritical water oxidation technology is suitable for the treatment of different types of antibiotic wastewater.The supercritical water oxidation and degradation pathways of different types of antibiotics are different.Penicillin and ofloxacin are based on the benzene ring.The external group of the ben-zene ring undergoes bond breaking and degradation first,and then the benzene ring is degraded by ring opening;In the degradation process,apart from the normal ring-open-ing degradation of itself,some of its intermediate degradation products will also form cyclic substances containing benzene rings,and then these cyclic substances undergo ring-opening degradation.