Studies On Degradation Of Florfenicol Using Submerged Ceramic Membrane Photocatalysis Reactor (SCMPR)

With the extensive production and frequent application of antibiotics,the water pollution caused by them is becoming more and more serious,which brings security risks to human health and ecosystem safety.In recent years,photocatalytic oxidation technology and membrane separation technology have been widely applied to treating the persistent organic pollutants of water body.To overcome the drawback that photocatalyst is difficult to be separated and recycled,membrane process is added into photocatalyst system,resulting in the development of membrane photocatalytic reactor?MPR?.In this paper,a self-made coupling photocatalysis and membrane processes system-Submerged Ceramic Membrane Photocatalytic Reactor?SCMPR?was established and used to degrade florfenicol in aqueous solutions.The operating effect of photocatalyzed oxidization,TiO₂retention,membrane pollution and self-cleaning property were investigated under different conditions.Reaction intermediates,mechanisms investigation and degradation pathway were also studied.The main results were showed as follows:?1?Adding TiO₂ into the reaction solution could improve the removal efficiency and ensure the stability of discharge quality,but there existed an optimal dosing quantity of TiO₂,more than which would result in the decrease of degradation;the mineralization efficiency decreased with the increasing of the FFC initial concentration;the optimal reaction time was determined by the combination of light intensity,FFC initial concentration and TiO₂ dosage;the decrease of ultraviolet wavelength and the enhancement of light intensity could promote the removal efficiency of FFC and TOC;the degradation of FFC was more suitable in weak acid conditions,but the condition of strong acid was not good for TOC removal efficiency.According to the range analysis and the variance analysis of L₉?3⁴?orthogonal experiment,the effects of main factors decreased in order:initial FFC concentration>light intensity>pH>TiO₂ dosage.Under the optimal photocatalytic condition(C_FFC=15mg/L,C_TiO2=50mg/L,pH=6.5,irradiation intensity=525W and reaction time=180min),the removal efficiency of FFC and TOC were up to 100%.?2?Both 0.1?m and 1?m pore size of ceramic membrane held the high TiO₂ separation efficiency,but the later had lower membrane flux decline rate and more stable trans-membrane pressure;the effect of liquid flow rate on the TiO₂ retention and membrane pollution was lighter than that of TiO₂ dosage;by using anti-gas to wash the membrane module,the pollution of membrane was weakened,and the water membrane flux could be restored.?3?The formation of organic acids in the degradation led to the decline of solution pH value;three kinds of anions existed in the reaction solution and the primary and secondary order of anions concentration could be ranked as Cl^->SO₄^2->F^-;based on GC/MS and HPLC/QTOF,11major substances including florfenicol were detected during the UV/TiO₂process;Four of the nine substances containing the benzene ring structure were searched with related toxicity records;hydroxyl radical played a leading role in the degradation of florfenicol.