Removal Mechanism Of PhACs By Bio-manganese Oxides And Safety Evalution

With the mass production and use of drugs,various pharmaceutically active compounds?PhACs?are frequently detected in aquatic environments around the world,posing a potential threat to the environment,aquatic animals,and plants.Pseudomonas putida through the oxidation of Mn???,to achieve the degradation of organic matter.In this paper,the degradation mechanism of paracetamol?APAP?and 1-naphthol during the oxidation of Mn???by Pseudomonas putida QYS-1 were studied.According to the characteristics of bio-manganese oxides,magnetic bio-manganese oxides with nano-Fe₃O₄ as the dispersed magnetic core was constructed,and the degradation rules of APAP during magnetic bio-manganese oxides recycling were explored.Manganese oxides produced by Pseudomonas putida QYS-1 were characterized.Manganese oxides formed rapidly in the growth curve of Pseudomonas putida QYS-1 within14-16h,accompanied by the rapid decrease of dissolved Mn???and complexed Fe???in the medium.The microstructure of bio-manganese oxides indicates that it is an irregularly shaped particle that aggregates in hills.The rate of APAP and 1-naphthol degradation is related to the rate of manganese oxides formation.The biodegradation rate of bio-manganese oxides was higher for APAP with the initial concentration of 10 mg/L,and the degradation rate was100%after 24h.The degradation rates of 1-naphthol with initial concentrations of 1,5 and 10mg/L were quite different.With the initial concentration of 1-naphthol increasing,the degradation rate decreased from 100%to 70%The bio-manganese oxides after APAP and1-naphthol were dissolved by ascorbic acid,and the presence of APAP and 1-naphthol was not found,indicating that the removal of APAP and 1-naphthol by bio-manganese oxides was not degradation but adsorption.The preparation method of magnetic bio-manganese oxides was studied.The optimum dosage of Fe₃O₄ was 0.5 g/L.The nano-Fe₃O₄ was added into PYCM medium together with bacteria for 40 h.At the initial concentration of 10 mg/L,APAP completely degraded at 10 h,while 1-naphthol was completely undetectable at 1 h.The degradation efficiency of high concentration APAP and 1-naphthol can reach 100%.During the degradation process,it was found that with the increase of the initial concentration of APAP and 1-naphthol,the size of magnetic biogenic manganese oxide gradually increased and the time of complete degradation gradually extended.The degradation rate of APAP gradually decreased from 100%to 32%as the number of APAP cycles degraded by magnetic bio-manganese oxide increased.The mechanism of degradation of APAP by magnetic bio-manganese oxides was explored.It is found that the magnetic organism manganese oxides degrades high concentration of target organics and forms the pore structure gradually evolving from the layered dense structure to the pore honeycomb structure.With the increase of the number of recycling,Mn???in the solution increased continuously,while Mn???in the manganese oxide decreased continuously,indicating that the degradation of the target organism mainly depends on the oxidation of Mn???by Pseudomonas putida QYS-1.The degradation intermediates of APAP and 1-naphthol were analyzed by LC-MS to deduce the possible degradation pathways of APAP and 1-naphthol.