Jalilian Ahmadkalaei, Seyedeh Pegah
(2018)
Integrated physical-Fenton remediation of petroleum-contaminated soil using ethyl lactate as a green solvent.
PhD thesis, University of Nottingham.
Abstract
The huge amount of petroleum hydrocarbons contaminated sites is the heritage of a long history of fossil fuels usage. Reducing petroleum hydrocarbons levels in contaminated soils by Fenton reaction and with the aid of one or two agents such as solvents, surfactants, or vegetable oils has been studied in recent years, with successful reported results. Nonetheless, destruction of the aliphatic fraction of total petroleum hydrocarbon (TPH) by Fenton reaction has been studied to a lesser extent as compared to the aromatic fraction of TPH. Additionally, studies regarding the effect of humic acid (HA) on Fenton reaction reported contradictory results, and more research is necessary to clarify HA effects. Lastly, although achieving the highest efficiency is the main objective of soil remediation technologies, the environmental side effects of the applied processes should be considered as important as the efficiency. In light of these, the main aim of this project was to increase Fenton treatment efficiency by using an environmental friendly solvent, ethyl lactate (EL). The project objectives included determining optimum levels for the reagents of Fenton reaction and desorption process such as hydrogen peroxide (H2O2) and EL, identifying the kinetic of TPH desorption and destruction of petroleum hydrocarbons by Fenton reaction in addition to analysing the effects of EL on these processes. Through desorption tests, EL/water solution demonstrated great ability to increase the removal efficiency and desorption of sorbed TPH. Desorption by EL/water solution consisted of a very fast desorption stage followed by a slow stage. After 30 min of desorption, the removal efficiency of TPH increased from 63% to 81% for EL=25% and EL=100%, respectively. The initial desorption rate for 25% and 100% were 1.625 mg/min and 3.368 mg/min, respectively. The results of batch experiments indicated that EL%=10% was the optimum value for the EL-modified Fenton reaction. After 4 h, an increase in H2O2 concentration from 0.1 M to 2 M at L/S=2 and EL=25% increased the removal efficiency of TPH from 68.41% to 90.21%. HA addition up to 150 mg/l was also studied. For fraction 1, adding HA led to an increase in removal efficiency while for fraction 2, only HA=150mg/l had higher removal efficiency than the HA=0 case and for fraction 3, addition of HA in the studied range could not increase the removal efficiency. A good compatibility of zero-valent iron nanomaterial with H2O2 was proved. Laboratory column experiments were finally carried out to remove petroleum hydrocarbons from diesel-contaminated soil with EL to reproduce the conditions of in-situ treatment. The remaining diesel in soil decreased by increasing H2O2 molarity from 0.1 M to 0.5 M whereas a further increase to 2 M led to an increase in remaining diesel in soil. The stability of H2O2 in EL has been observed which signifies good potential for in-situ applications. Overall, the project has demonstrated the feasibility of EL-modified Fenton reaction for the remediation of petroleum-contaminated soil.
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