Study On The Distribution Characteristics Of Free Radicals And Fenton Oriented Oxidation Of Crude Oil-contaminated Soil

Soil orgnic matter(SOM)is usually tightly integrated with total petroleum hydrocarbon(TPH).SOM is not the object of removal in the process of Fenton oxidation,but SOM will compete with TPH to consume hydroxyl radicals(·OH)to interfere with the removal of TPH.When the content of SOM is high,the amount of·OH consumed is huge(about 30%?80%),only a small amount of hydroxyl radicals are used to oxidize TPH,resulting in a lower oxidation efficiency of TPH.In order to reduce the effect of SOM on·OH consumption during the oxidation of TPH.In this paper,we carried out the oxidation experiment under low H₂O₂ concentration,the100-day bioremediation experiment,the effect experiment of HA content on·OH partitioning and the relationship between·OH partitioning and SOM oxidation in solid phase iron system.Finally,conclusions can be drawn as follows:(1)When the H₂O₂ concentration is too low(25 m M)and iron is excessive(5.8m M),the OH yield is low(1.19 a.u.),but the SOM oxidation efficiency is high and the amount of hydroxyl radicals is distributed(56%).(2)The most reactive functional groups in the SOM that consume hydroxyl radicals are C=O(1650-1960 cm^-1),C-H(2820 cm^-1)in the aldehyde group,N-H(3300-3500 cm^-1),and O-H in alcohol and phenol(3200-3700 cm^-1).(3)The reactive organic substances that are easily consumed by hydroxyl radicals in SOM are protein 1,protein 2,microorganisms and humic acids,and are organic substances that need to be passivated.(4)After adding NaOH to change the functional group of SOM,the oxidation amount of TPH in JS soil was greatly increased,and the oxidation amount of TPH was up to 10109 mg/kg,which was 2.0 times(5078 mg/kg)before the change.In addition,the oxidation of the long-chain hydrocarbon C₂₆-C₃₀ reached 2399-4060 mg/kg,which was 1.0-6.3 times(641-2478 mg/kg)before the change.It is indicated that this functional group regulation by NaOH is successful.This is because NaOH reduces the saturated C-H bond and the O-H bond in the carboxyl group in the SOM organic functional group,reducing the ability of humic acid and fulvic acid to capture free radicals in SOM.The amount of hydroxyl radicals consumed by SOM decreased from80%before the change to 35%after the change,indicating that 45%of the hydroxyl radicals can be transferred from the oxidized SOM to the oxidized crude oil,only 20%before the change.The hydroxyl radicals are used to oxidize crude oil,and up to 65%of hydroxyl radicals are used to oxidize crude oil,which is the reason for the substantial increase in TPH oxidation in JS soil.(5)After Fe changed the functional group of SOM,the oxidation amount of TPH in JS soil increased greatly,and the oxidation amount of TPH reached 19104 mg/kg,which was 2.4 times(7842 mg/kg)before the change.Further,the O-H bond in the carboxyl,the N-H bond,the O-H bond in the alcohol and phenol.Indicating that this functional group regulation by Fe is successful.At this time,the amount of hydroxyl radicals consumed by SOM decreased from 60%before the change to 19%after the change,indicating that 41%of the hydroxyl radicals were transferred from the oxidized SOM to the oxidized crude oil,only 40%before the change.Hydroxyl radicals are used to oxidize crude oil,and up to 81%after the change.This is the reason why the amount of TPH oxidation in JS soil is greatly increased.(6)The·OH strength is low in the chemical oxidation stage,the faster the nutrient mobilization in the early stage of bioremediation,the oxidation amounts of TPH is higher.When the concentration of H₂O₂ is 25 m M,the consumption of ammonia nitrogen reached 558-610 mg/kg 40 days before bioremediation in ZC2 and ZC6 oil contaminated soil.Which were 1.1-1.4 times(424-489 mg/kg)of 50 m M and 1.1-1.2times(501-503 mg/kg)of 100 m M,respectively.The consumption of dissolved organic caron(DOC)reached 7356-7488 mg/kg,which were 1.1-1.2 times of 50 m M(6016-6564 mg/kg)and 1.0-1.2 times(6536-7392 mg/kg)of 100 m M,respectively.The degradation of TPH reached 3783-5317 mg/kg,which were 1.3-1.4 times of 50 m M(2815-3825 mg/kg)and 1.0-1.2 times of 100 m M(3630-4481 mg/kg).