Synthesis of iron-manganese bimetallic materials supported by activated carbon and application of activated persulfate in the degradation of soil contaminated by crude oil.

Heterogeneous catalytic processes based on zero-valent iron (ZVI) have been developed to treat soil and wastewater pollutants. However, the agglomeration of ZVI reduces its ability to activate persulfate (PS). In this study, a new Fe-Mn@AC activated material was prepared to activated PS to treat oil-contaminated soil, and using the microscopic characterization of Fe-Mn@AC materials, the electron transfer mode during the Fe-Mn@AC activation of PS was clarified. Firstly, the petroluem degradation rate was optimized. When the PS addition amount was 8%, Fe-Mn@AC addition amount was 3% and the water to soil ratio was 3:1, the petroluem degradation rate in the soil reached to the maximum of 85.69% after 96 h of reaction. Then it was illustrated that sulfate and hydroxyl radicals played major roles in crude oil degradation, while singlet oxygen contributed slightly. Finally, the indigenous microbial community structures remaining after restoring the Fe-Mn@AC/PS systems were analyzed. The proportion of petroleum degrading bacteria in soil increased by 23% after oxidation by Fe-Mn@AC/PS system. Similarly, the germination rate of wheat seeds revealed that soil toxicity was greatly reduced after applying the Fe-Mn@AC/PS system. After the treatment with Fe-Mn@AC/PS system, the germination rate, root length and bud length of wheat seed were increased by 54.05%, 7.98 mm and 6.84 mm, respectively, compared with the polluted soil group. These results showed that the advanced oxidation system of Fe-Mn@AC activates PS and can be used in crude oil-contaminated soil remediation.

Metagenomic analysis reveals specific BTEX degrading microorganisms of a bacterial consortium.

Petroleum hydrocarbon contamination is of environmental and public health concerns due to its toxic components. Bioremediation utilizes microbial organisms to metabolism and remove these contaminants. The aim of this study was to enrich a microbial community and examine its potential to degrade petroleum hydrocarbon. Through successive enrichment, we obtained a bacterial consortium using crude oil as sole carbon source. The 16 S rRNA gene analysis illustrated the structural characteristics of this community. Metagenomic analysis revealed the specific microbial organisms involved in the degradation of cyclohexane and all the six BTEX components, with a demonstration of the versatile metabolic pathways involved in these reactions. Results showed that our consortium contained the full range of CDSs that could potentially degrade cyclohexane, benzene, toluene, and (o-, m-, p-) xylene completely. Interestingly, a single taxon that possessed all the genes involved in either the activation or the central intermediates degrading pathway was not detected, except for the Novosphingobium which contained all the genes involved in the upper degradation pathway of benzene, indicating the synergistic interactions between different bacterial genera during the hydrocarbon degradation.

Fingerprint characteristics of refined oils and their traceability in the groundwater environment.

Chemical fingerprinting is essential for identifying the presence and responding to oil spills that frequently contaminate the groundwater environment of refineries. In this study, crude oil and oil products from the atmospheric and vacuum distillation units of a refinery were analyzed by gas chromatography-mass spectrometry (GC-MS) to evaluate their chemical variability before and after refinery. A series of experiments involving evaporation and soil column penetration were conducted to simulate refined oil spilling into groundwater and determine appropriate characteristic ratios (CRs) for principal component analysis (PCA) for oil source identification. The simulated study demonstrated that all products had bell-shaped n-alkane distributions, with dominant peaks that remained unchanged or shifted towards longer chain lengths compared to the source oil. Similarly, naphthalene and dibenzothiophene series remained the main PAH components like the source oil. Ten relatively stable CRs were selected for PCA to identify different oil products through the simulated experiments. The chosen CRs were then utilized to identify the sources for two groundwater oil spills recently occurred, one that occurred in an oil depot area, and another near a continuous catalytic reforming unit in a refinery. This study showed that the components with long-chain n-alkanes (n ≥ C18), pristane, phytane, and phenanthrene and dibenzothiophene series PAHs played an important role in the identification of refined oil products spilling into the groundwater environment. The selected CRs provide an effective tool for rapid and accurate identification of oil spills, especially for newly occurring spills in the groundwater environment, which can aid in developing appropriate response strategies.

[Advances in the bioaugmentation-assisted remediation of petroleum contaminated soil].

Bioremediation is considered as a cost-effective, efficient and free-of-secondary-pollution technology for petroleum pollution remediation. Due to the limitation of soil environmental conditions and the nature of petroleum pollutants, the insufficient number and the low growth rate of indigenous petroleum-degrading microorganisms in soil lead to long remediation cycle and poor remediation efficiency. Bioaugmentation can effectively improve the biodegradation efficiency. By supplying functional microbes or microbial consortia, immobilized microbes, surfactants and growth substrates, the remediation effect of indigenous microorganisms on petroleum pollutants in soil can be boosted. This article summarizes the reported petroleum-degrading microbes and the main factors influencing microbial remediation of petroleum contaminated soil. Moreover, this article discusses a variety of effective strategies to enhance the bioremediation efficiency, as well as future directions of bioaugmentation strategies.

Design of facile technology for the efficient removal of hydroxypropyl guar gum from fracturing fluid.

With the increasing demand for energy, fracturing technology is widely used in oilfield operations over the last decades. Typically, fracturing fluids contain various additives such as cross linkers, thickeners and proppants, and so forth, which makes it possess the properties of considerably complicated components and difficult processing procedure. There are still some difficult points needing to be explored and resolved in the hydroxypropyl guar gum (HPG) removal process, e.g., high viscosity and removal of macromolecular organic compounds. Our works provided a facile and economical HPG removal technology for fracturing fluids by designing a series of processes including gel-breaking, coagulation and precipitation according to the diffusion double layer theory. After this treatment process, the fracturing fluid can meet the requirements of reinjection, and the whole process was environment friendly without secondary pollution characteristics. In this work, the fracturing fluid were characterized by scanning electron microscopy (SEM), Energy dispersive X-ray (EDX), X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy technologies, etc. Further, the micro-stabilization and destabilization mechanisms of HPG in fracturing fluid were carefully investigated. This study maybe opens up new perspective for HPG removal technologies, exhibiting a low cost and strong applicability in both fundamental research and practical applications.