| The treatment and remediation of petroleum contaminated soil has become one of the most important environmental problems urgently.At present,activated persulfate advanced oxidation technology is mainly used in the field of sewage treatment,for the soil difficult to degrade organic pollutants research is relatively weak.In this paper,petroleum-contaminated soil was used as the object of study,and diesel as the representative pollutant.The mechanism and the main factors of persulfate activation in the remediation of soil petroleum hydrocarbons were studied by different activation methods such as Fe2+ and Fe3O4.The kinetics and degradation process of persulfate activation were discussed.The main contents are shown as follows:(1)The thermally activated persulfate test showed that the activation temperature was 70 ?,the dosage of sodium persulfate was 0.8 mmol/g,the initial pH was 11,the ratio of soil to water was 2:1,and the diesel removal rate was 76.85%when the reaction was 72 h,and removal speed averaged 33.3 mg/h.Orthogonal test and response surface analysis show that the proportion of soil and water is the main controlling factor,followed by dosage,activation temperature and initial pH.Molecular probe competition experiments show that the main free radicals in the system are sulfuric acid radicals(·SO4-)in the presence of acidic and neutral conditions.Under the condition that pH is alkaline,there are hydroxyl radical(-OH)and ·SO4-.The thermally activated of the persulfate repair process is mainly due to the oxidation of-S04-,the process is an endothermic reaction.The temperature rise is favorable for the degradation.The apparent activation energy is-80.73 KJ/mol.Gas chromatographic(GC)analysis showed that the number of peaks decreased from 88 to 75,significantly reduced the number of diesel components.(2)Fe2+ activated sodium persulfate test showed that the dosage of sodium persulfate was 0.5 mmol/g,the ratio of Fe2+ to sodium persulfate was 1:5,the ratio of soil to water was 2:1,the initial pH was 3,and the temperature was 50 ?.The diesel removal rate was 85.73%when the reaction was 72 h,and removal speed averaged 64.33 mg/h.The average diesel removal rate is about 1.93 times compared to the heat activated persulfate repair process.Orthogonal test and response surface analysis show that pH is the main controlling factor,followed by soil and water ratio,dosage,Fe2+ and Na2S2O8 ratio.Compared with the thermally activated persulfate repair process,the main reason for the pH as the main controlling factor is that the pH determines the form of iron ions in the solution.Acid treatment is the best,and the repair process is still the main oxidation of ·SO4-.GC analysis showed that the number of peaks decreased from 88 to 75,significantly reduced the number of diesel components.(3)Fe3O4 activated sodium persulfate test showed that the dosage of sodium persulfate was 0.5 mmol/g,the ratio of Fe3O4 to sodium persulfate was 1:10,the ratio of soil to water was 2:1,the initial pH was 11,and the temperature was 30 ?.The diesel removal rate was 76.76%when the reaction was 72 h,and removal speed averaged 57.59 mg/h.Compared with the thermal activation and Fe2+ activated persulfate repair process,the average diesel removal rate was about 1.72 and 0.895 times.The orthogonal test and the response surface analysis show that the ratio of Fe3O4 and Na2S2O8 is the main controlling factor,followed by water and soil ratio,dosage,pH.Under alkaline conditions,the repair process is a process of ·OH and ·SO4-together.GC analysis showed that the number of peaks decreased from 88 to 68,significantly reduced the number of diesel components.In conclusion,Fe3O4 activation is more suitable as an alternative remediation technique for diesel contaminated soils.The study will provide reference for chemical remediation of contaminated soil. |
PDF Full Text Request