The Effect Of High Temperature And High Pressure On The Biodegradability Of Sulfonated Asphalt

Sulfonated asphalt is widely used in recent years because of its anti-sloughing,lubrication,emulsification,reduce filtration and high temperature stability.Sulfonated asphalt is mostly brown fragile flake or flowing powder,which has complex structure and compounds of large molecular weight and is mainly composed of asphalt sulfonate,asphalt phenol,inorganic,oxidized asphalt,saturated hydrocarbons,polycyclic aromatic compounds and so on.Sulfonated asphalt,with high color and poor biodegradability,is difficult to degrade organic matter.In this paper,the drilling additive agent sulfonated asphalt was used as the research and its biodegradability was evaluated by aerobic biochemical experiments.The effects of different reaction time,reaction temperature and reaction pressure on the biodegradability of sulfonated asphalts were investigated.The composition and functional groups of sulfonated asphalt were analyzed by FT-IR and GC-MS before and after the reaction.The optimum process conditions(time,temperature and pressure)of sulfonated asphalt treated by HT/HP were achieved using response surface methodology.The optimal culture conditions were as follows:MLSS was 5000 mg·L-1,incubated at 28 ℃ for 48 h.The%COD reduction,CODB/COD and biodegradation rate of aerosolized of sulfonated asphalt was reached the maximum,which was 52.61%,0.55 and 0.0546 h-1 respectively.The effects of reaction time,reaction temperature and reaction pressure on the treatment of sulfonated asphalt were investigated.The results showed that the biodegradability of sulfon ated asphalt was improved remarkably after high temperature and high pressure treatment.Un der the optimum treatment conditions were as follows:reaction time 40 min,reaction tempera ture 220 ℃ and reaction pressure 11 MPa,the COD removal rate was reached 82.25%,CODB/COD was 0.86 and the biodegradability rate was 0.1200 h-1.The aerobic biochemical degrada tion is basically the same,following the first-order reaction kinetics model and the model has good fitting to the actual numerical value.The correlation coefficient was reached a very significant level(R2>0.8409).The biodegradation rate of the treated sulfonated asphalt was higher than that of the untreated sample whose biodegradation rate constant was 0.0546 h-1.the samples were charactered by FT-IR and GC-MS before and after HT/HP treatment.The results showed that after HT/HP treatment,the macromolecule material was cracked to form new molecules,which promoted the biodegradability of sulfonated asphalt.Response Surface Methodology(RSM)and quadratic polynomial regression model were used to optimize the operating parameters.According to the 3D and contour figure,the interaction between reaction temperature and reaction pressure was notable for the%COD reduction,and not remarkable for CODB/COD and the aerobic biodegrading rate.The optimal independent variables of HT/HP reaction process were suggested as following:reaction time of 49.91 min,reaction temperature of 220℃ and reaction pressure of 11 MPa,the experimental values for ratio of CODB to COD(0.8234)was in good agreement with the values predicted from the models(0.8469),with relatively small errors between the predicted and the actual values.