Experimental Study On The Influence Factors And Effect Of Two Kinds Of Refinery Wastewater Treatment By TiO₂ Photocatalytic Suspension System

The reverse osmosis?RO?concentrated water of refinery is the concentrated water produced by double membrane after the secondary biochemical wastewater treatment.Phenol acetone wastewater is derived from the production process of phenol-acetone by cumene.The two kinds of refinery wastewater have the characteristics of large discharge,complex composition of pollutants,difficult to degrade,high salinity and so on.If it is discharged directly into the environment,it will endanger the water environment,and the toxic substances in the wastewater will also affect the health of human beings.Therefore,it is necessary to carry out the deep treatment of the sewage treatment stations in the industrial enterprises to reduce the organic content,to meet emission standards or reuse requirements.The photocatalytic oxidation technology has the advantages of strong catalytic capacity,wide application and no secondary pollution and so on.It is considered to be a promising new water treatment technology for industrial refractory sewage.But its application in practical wastewater is less.So this paper attempts to use the photocatalytic oxidation technology to deal with the actual refinery reverse osmosis?RO?concentrated water and phenol acetone wastewater.The influence and regularity of p H,catalyst type,Ti O₂ dosage,initial concentration,light,ionic species and concentration on influence and law of photocatalytic degradation were studied.The effects of photocatalytic degradation of two kinds of wastewater was investigated.The kinetic model and adsorption model for photocatalytic degradation were discussed.The biodegradability of water samples after photocatalytic treatment was verified,and the effect of photocatalytic ozonation combined process on the degradation of RO concentrated water was investigated by orthogonal experiment.At the same time,the suspension type Ti O₂ was recovered and reused by flocculation and microfiltration separation,to investigate the service life of catalyst.The deactivated photocatalyst was regenerated by four different ways to increase the utilization of the catalyst.?1?The nanometer titanium dioxide?P25?was selected as a catalyst for subsequent experiments by a single factor test.The results of single factor experiments show that P25 can firstly adsorb organics in water,and the adsorption of organics follows pseudo two order kinetics equations.The photocatalytic process conforms to the first order kinetic equation with the reaction time.The initial concentration of organic matter and the type and concentration of inorganic ions in wastewater also affect the photocatalytic degradation efficiency.Under the optimum reaction conditions,the RO concentration of p H was 4.5,the dosage of Ti O₂ was 1g/L,UV light after 8 h,the removal rate of COD was up to 47%.Phenol acetone wastewater in p H=4,Ti O₂ dosage of 2 g/L,UV light after 8 h,the highest COD removal rate is 49%.?2?The B/C of RO concentrated water increased from 0.01 to 0.22 after the photocatalytic treatment.Phenol acetone wastewater B/C increased from 0.16 to 0.54.The results of Fourier transform infrared attenuated total reflection?FITR-ATR?analysis showed that aromatic and unsaturated substances in the water after the photocatalytic treatment have decreased,it is indicated that photocatalytic oxidation of refractory organic matter can be oxidized into biodegradable small molecules,the results are consistent with the enhancetent of biodegradability.After the biological treatment of phenol acetone wastewater after acclimation,the COD remained at 73¹07 mg/L,which laid a good foundation for its application.?3?Treatment of RO concentrated water by photocatalysis-ozone method to further improve the degradation effect of wastewater.The orthogonal experiment with 3 factors and 3levels was designed:the 3 factors were p H,Ti O₂ dosage and ozone dosage.The range analysis and variance analysis show that 3 factors have significant effect on COD removal rate,and the primary order of the effects is the dosage of ozone>p H>Ti O₂,the reaction time is reduced and the processing cost is reduced compared with the photocatalytic alone.Through Fourier transform infrared analysis,the aromatic and unsaturated compounds in water decreased more than photocatalysis alone.The next step is to verify whether to further improve the biodegradability.?4?Two methods of membrane separation and flocculation were used to recycle the suspended Ti O₂,by selecting organic flocculant PAM,The optimum flocculation conditions were obtained by orthogonal experiment,when the dosage of PAM was 12mg/L,the flocculation effect was best in neutral conditions.After 4 times of flocculation recovery,the catalyst was almost inactivated by the accumulation of organic compounds on the surface,which can save 49%input cost by reusing.After the catalyst was separated by 0.45?m microfiltration membrane,the turbidity of the filter is 0NTU,which indicated that it had a good interception effect on Ti O₂,after 5 times the catalyst activity is only the original one third,savings cost is 66%.The comparison of the two methods shows that membrane separation is more beneficial to the reuse of catalyst,because the addition of flocculant can not be separated from the photocatalyst,it will gradually accumulate in the water and then affect the water quality,flocculation recovery can also cause agglomeration of catalyst particles,also it need to adjust the p H to increase processing costs.The membrane can be backwashed by wasterwater to achieve reuesing,the membrane also maintain the stability of catalyst concentration.?5?The catalyst basicly inactivated after reusing 5 times by membrane separation recovey,the deactivated catalyst was regenerated by acid washing,alkali washing,calcination at 400 degrees C and H₂O₂+UV in four ways,the regeneration effect was investigated by COD removal rate of RO concentration.The results showed that the regeneration effect of H₂O₂+UV is the best,and the restoration is the original 83.7%,the calcination and the 2%pickling are the second,and the alkali washing is almost no effect,this is related to adsorption and accumulation in the catalyst surface of intermediate products,inorganic sediments,etc.There are reversible inactivation and irreversible inactivation of deactivation,some regeneration methods only work on reversible inactivation.