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Microemulsions enhanced bioremediation of polycyclic aromatic hydrocarbons (PAHs) contaminated soil using composting technology
| Content Provider | Semantic Scholar |
|---|---|
| Author | Wong, Siu Yi |
| Copyright Year | 2011 |
| Abstract | Soil contamination with polycyclic aromatic hydrocarbons (PAHs), originated from increasing consumptions of coal and petroleum necessitates to the development of innovative technologies to remove PAHs from soil. Thermophilic bioremediation is regarded as one of the most popular strategies to remediate soil contaminated by PAHs. However, the success of bioremediation has been limited by the low aqueous solubility and poor bioavailability of these hydrophobic organic compounds. Microemulsions which have been successfully employed in soil washing to increase the solubility and desorption of hydrophobic pollutants, were evaluated for their feasibility to improve the biodegradation of PAHs compounds in soil using composting approach. The first phase of the present study aimed at developing microemulsion formulation under thermophilic temperature (55C) and assessing their effect on solubilizing two representative PAHs, phenanthrene (PHE) and benzo[a]pyrene (B[a]P). Tween 80, linseed oil, with the presence of 1-pentanol to serve as a cosurfactant could form oil-in-water microemulsions under thermophilic condition. Solubilization results showed that the behaviours of microemulsions were similar to surfactants, which showed the equilibrium solubility of PAH compounds increased linearly with increasing concentration of surfactant above critical micelle concentration. In addition, the oil concentration was another important factor in enhancing of solubilization of PAHs. With 250 mg L linseed oil, there was no difference between the weight solubilization ratio (WSR) values in microemulsions and Tween 80 alone systems; however, when the oil concentration increased to 500 mg L in microemulsions, the maximum WSR values for PHE and B[a]P were 0.0751 and 0.0133 which were about 1.6 to 2 fold higher than that of their Tween 80 counterparts. Furthermore, the microemulsions containing 1000 mg L linseed oil did not further increase the solubilization. Due to the structure of microemulsions, the WSR values reached a maximum and were constant even the extra amount of oil was added into the system. The feasibility of using oil-in-water microemulsions to enhance the bioremediation of PHE and B[a]P in aqueous system was evaluated in the second phase. No additional benefit was observed on the biodegradation of PHE by adding microemulsions consisting 0.2% and 0.4% Tween 80 to aqueous system, which is likely due to the high aqueous solubility of PHE making it readily accessible for microbial degradation. The stimulatory effect of surface active agents on aqueous biodegradation was more pronounced with the higher molecular weight B[a]P. Additionally, the results clearly indicated that the removal rate of B[a]P in microemulsions was higher than that in their respective Tween 80 solution alone systems. And it is also worth to note that the removal rate of B[a]P increased with increasing oil content and shown a significant difference in both 0.2% and 0.4% Tween 80 microemulsion systems. However, a distinct inhibitory effect on PHE and B[a]P degradation was observed in the presence of 0.4% Tween 80 solution, which reduced the removal rate to half as that of control group, only 34.4% and 18.6% removal of PHE and B[a]P, respectively. This might be due to surfactants which might reduce the cell surface hydrophobicity of Bacillus subtilis (BUM) and as a result, might inhibit the uptake of hydrophobic pollutants. Microemulsions increased the solubilization of PAHs and might simultaneously suppress the negative effects of Tween 80. Therefore, microemulsions could successfully enhance the solubilization of PAHs and subsequently benefit to the biodegradation. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://lib-nt2.hkbu.edu.hk/cil-image/theses/abstracts/b25271015a.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
