Degradation Of Indigo Carmine Dye Wastewater By Sodium Persulfate And Ozone Systems In Rotor-stator Reactor

With the increasing demand for a better ecological environment,the pollution of dye wastewater has become a severe problem.It is thus urgent to upgrade the wastewater treatment processes.Advanced oxidation processes of persulfate and ozone has broad application prospects in industrial wastewater treatment due to their excellent oxidation ability.In this paper,a combined process of higee advanced oxidation processes and sequencing batch reactor activated sludge process(SBR)for the degradation of indigo carmine(IC)dye wastewater is proposed.Three oxidation processes,S2O82-/Fe2+,O3 and S2O82-/O3/Fe2+,were intensified in a rotor-stator reactor(RSR)to improve the biodegradability and degradation efficiency of a simulated IC dye wastewater.The degradation mechanism and kinetics were also investigated.The main research contents are as follows:1.The decolorization effect of sodium persulfate(PS)activated by six kinds of metal ions to degrade IC wastewater in a stirred tank reactor was ranked as Fe2+>Ag+>Cu2+>Mn2+>Mg2+>Zn2+,and Fe2+was determined as a suitable metal ion to activate PS.It is revealed that the degradation of IC wastewater by PS is a pseudo-first order reaction,and the degradation of IC wastewater by PS/Fe2+ is a pseudo-second-order chemical reaction.2.IC wastewater with a concentration of 200 mg·L-1 was treated by the PS/Fe2+,O3,PS/O3/Fe2+ processes in RSR,and suitable process conditions were proposed.The decolorization efficiency of IC wastewater reached 41.9%by the PS/Fe2+ process when the temperature,PS concentration,Fe2+concentration,rotation speed and liquid flow rate of were 25℃,0.8 mmol·L-1,0.8 mmol·L-1,600 rpm and 30 L·h-1 respectively.The decolorization efficiency of IC wastewater reached 40.0%by the O3 process under the conditions of a temperature,O3 concentration,rotation speed,gas and liquid flow rate of 25℃,2.5 mg·L-1,600 rpm,30 L·h-1 and 30 L·h-1 respectively.The decolorization efficiency of IC wastewater was up to 55.2%by the PS/O3/Fe2+ process at a temperature,PS concentration,Fe2+ concentration,03 concentration,rotation speed and gas-liquid ratio of 25℃,0.2 mmol·L-1,0.05 mmol·L-1,2.5 mg·L-1,600 rpm and 1 respectively.3.The degradation mechanism of IC wastewater by PS/Fe2+,03,PS/O3/Fe2+ processes were deduced by liquid chromatograph-mass spectrometry.The carbon-carbon double bond of IC is attacked firstly by oxidants during the degradation of IC to generate isatin sulfonic acid,which is further oxidized to produce C7H4NO4S-and C8H6N06S-.These two substances are then oxidized separately,with the amino group on the benzene ring oxidized to nitro group to form nitrophenol,and then the benzenediol is oxidized to benzoquinone.The benzene ring subsequently opens to form a chain structure with the carboxyl group,leading to the degradation IC molecule into small molecule compounds.4.Studies on the IC degradation effect by the PS/Fe2+,O3,PS/O3/Fe2+higee oxidation processes in series with SBR indicate that the PS/O3/Fe2+process was the best as a pretreatment means.Upon the treatment of the IC wastewater by the PS/O3/Fe2+ +SBR process,IC and COD degradation efficiencies reach 99.5%and 36.3%respectively.