Remediation Of Hydrocarbons Research Articles

Isolation, screening and characterization of hydrocarbon-degrading bacteria isolated from oil contaminated soil in Wasit province / Iraq

Eleven soil samples were collected from one of the oil sites in Wasit Governorate.65 bacterial isolates were isolated from soil samples by using BHM with 1% crude oil as carbon source. In primary and secondary screening (10) isolates of bacteria can remediate crude oil. Among the ten isolates, bacterial isolate named HD2 was most effective in bioremediation process. The results of biomass, optical density, and percentage of hydrocarbon remediation of HD2 were (0.63, 1.080 and 67 %) respectively. The results of morphological and biochemical tests showed that the bacterial isolate named HD2 belongs to the species Pseudomonas putida.

A potential remediation of total petroleum hydrocarbon from contaminated soils using surfactant suspended multiwall carbon nanotubes

The spill of crude oil on the soil contaminates it, causing cancer, a dearth of vegetation, livestock deaths, and forced migrations. The petroleum hydrocarbon (TPH) was removed from the soil by ultrasonication of MWCNTs (Multiwalled Carbon Nanotubes) only, MWCNTs + IONP (Iron Oxide Nanoparticles) and MWCNTs + IONP + PEG (Polymer Nanocomposite (P.N.C)) in a laboratory batch adsorption experiment with Triton X 100 surfactant. The effects of contact time, agitation speed, adsorbent dosage and pH was studied. Results showed varied and high removal rate for the three adsorbent suspensions at different parameter. The highest removal percentage was 91.37% at pH 2 for MWCNTs + IONP and 90.72% at 90 min contact time for MWCNT only, while 85.56% was observed for P.N.C at 0.01g adsorbent dosage. However, all three adsorbent suspensions exhibit high removal rates regardless of the parameters studied. In this case, Freundlich's adsorption isotherm was the most accurate description of the process, while pseudo-second order fit the kinetic data more accurately.

Phenanthrene removal from soil washing eluent by Bacillus subtilis embedded in alginate-carboxymethyl cellulose-diatomite beads

ABSTRACT The processes of surfactant-enhanced soil washing have been widely applied to the remediation of polycyclic aromatic hydrocarbon (PAH)-contaminated soil, accompanied by the production of soil washing eluent. In this study, novel composite materials of beads containing alginate, carboxymethyl cellulose and diatomite (SCD) were used to encapsulate Bacillus subtilis to remove phenanthrene (PHE) from simulated soil washing eluent with rhamnolipid. The effects of dosage, pH and temperature on the PHE removal performance were explored, and the optimal PHE removal conditions [SCD bead dose 16.2% (w:v), pH 7.1 and 30.6°C] were determined using response surface methodology. After incubation in simulated soil washing eluent for 7 d, SCD beads removed 84.92% of PHE, which was 49.18% higher than by free bacteria. In addition, SCD beads mainly removed PHE through biodegradation processes, and the degradation rate (1.38 mg L−1 d−1) was higher than that of free bacteria (0.64 mg L−1 d−1). Characterization results revealed that the immobilized substrate provided the micro-environment for bacteria and reduced the intense effect of high rhamnolipid concentration. Reusability results showed that SCD beads could be recycled four times to remove 80.05% of PHE. Collectively, SCD beads have great prospects for the decontamination of soil-washing eluent containing complex components.

Insights into the removal of fluoranthene by sodium percarbonate activation with pyrite: Performance, mechanism, and degradation pathways

Sodium percarbonate (SPC) induced advanced oxidation processes have been used for the remediation of polycyclic aromatic hydrocarbons (PAHs) contamination, however, the feasibility studies of SPC and pyrite (FeS2) process are scarce. In this work, FeS2 served as a catalyst and reductant to activate SPC for fluoranthene (FLT) removal. 100% FLT removal was obtained at an initial solution pH of 5.90 with FeS2 and SPC dosages of 0.5 g/L and 0.02 mM, respectively, and the influences of initial aqueous solution pH, dissolved oxygen, and various aqueous solution matrixes on FLT degradation were explored. Based on the results of electron paramagnetic resonance detection and scavenging experiments, it was demonstrated that HO•, 1O2, and O2−• played dominant roles in the removal of FLT, whereas CO3−• could only be involved in the ROS proliferative reaction in FeS2/SPC process due to the weak oxidizing capacity. Additionally, three FLT degradation pathways were proposed based on the detected degradation intermediates 1-phenylnaphthalene, indane, and phthalic acid. Finally, the desorption of FLT in soil was investigated by employing surfactants and organic acids, with organic acids being less effective than surfactants. Since the majority of organic acids can be utilized as advanced oxidation process promoters, their practical application is advantageous.

Exploring the bacterial genetic diversity and community structure of crude oil contaminated soils using microbiomics

The impact of environmental pollution in air and water is reflected mainly in the soil ecosystem as it impairs soil functions. Also, since the soil is the habitat for billions of organisms, the biodiversity is in turn altered. Microbes are precise sensors of ecological contamination, and bacteria have a key and important function in terms of bioremediation of the contaminated soil. Hence in the current work, we aimed at assessing the unidentified bacterial population through Illumina MiSeq sequencing technology and their community structural changes in different levels of petroleum-contaminated soil and sludge samples (aged, sludge, and leakage soil) to identify unique bacteria for their potential application in remediation. The studies showed that major bacterial consortiums namely, Proteobacteria (57%), Alphaproteobacteria (31%), and Moraxellaceae (23%) were present in aged soil, whereas Proteobacteria (52%), Alphaproteobacteria (33%), and Rhodobacteraceae (28%) were dominantly found in sludge soil. In leakage soil, Proteobacteria (59%), Alphaproteobacteria (33%), and Rhodobacteraceae (29%) were abundantly present. The Venn diagrams are used to analyze the distribution of abundances in individual operational taxonomic units (OTUs) within three soil samples. After data filtering, they were grouped into OTU clusters and 329 OTUs were identified from the three soil samples. Among the 329, 160 OTUs were common in the three soil samples. The bacterial diversity is estimated using alpha diversity indices and Shanon index and was found to be 4.490, 4.073 and 4.631 in aged soil, sludge soil and leakage soil, respectively and similarly richness was found to be 618, 417 and 418. The heat map was generated by QIIME software and from the top 50 enriched genera few microbes such as Pseudomonas, Bacillus, Mycobacterium, Sphingomonas and Paracoccus, were shown across all the samples. In addition, we also analyzed various physicochemical properties of soil including pH, temperature, salinity, electrical conductivity, alkalinity, total carbon, total organic matter, nitrogen, phosphorus and potassium to calculate the soil quality index (SQI). The SQI of aged, sludge and leakage soil samples were 0.73, 0.64, and 0.89, respectively. These findings show the presence of unexplored bacterial species which could be applied for hydrocarbon remediation and further they can be exploited for the same.

Low-temperature thermally enhanced bioremediation of polycyclic aromatic hydrocarbon-contaminated soil: Effects on fate, toxicity and bacterial communities

Remediation of polycyclic aromatic hydrocarbon (PAH)-contaminated soil using thermal desorption technology typically requires very high temperatures, necessitating coupled microbial treatment for energy and cost reduction. This study investigated the fate and toxicity of PAHs as well as the responses of microbial communities following thermal treatment within a low temperature range. The optimal temperature for PAH mineralization was 20–28 °C, within the growth range of most mesophilic microorganisms. By contrast, 50 °C treatment almost completely inhibited PAH mineralization but resulted in the greatest detoxification effect particularly for cardiotoxicity and nephrotoxicity. A potential increase in toxicity was observed at 28 °C. Co-metabolism and non-extractable residue formation may play an interdependent role in thermally enhanced bioremediation. Moreover, alterations in bacterial communities were strongly associated with PAH mineralization and zebrafish toxicity, revealing that soil microorganisms play a direct role in PAH mineralization and served as ecological receptors reflecting changes in toxicity. Network analysis revealed that Firmicutes formed specific ecological communities at high temperature, whereas Acidobacteria and Proteobacteria act as primary PAH degraders at moderate temperature. These findings will enable better integration of strategies for thermal and microbial treatments in soil remediation.

Propylene glycol-mixed steam enhanced extraction for an efficient and sustainable remediation of PAHs-contaminated soil

An innovative thermal desorption method, propylene glycol (PG)-mixed steam enhanced extraction, is proposed for a highly efficient remediation of polycyclic aromatic hydrocarbons (PAHs)-contaminated soil. It is found that injecting PG-mixed steam into soil column could obtain > 99% removal efficiencies of PAHs either for the pyrene-spiked soil, or for the contaminated field soil with high-molecular-weight PAHs. PG is a safe and low-cost dihydric alcohol with a boiling point higher than water. When the PG-mixed steam penetrated the contaminated soil, the PG vapor preferentially condensed to form a hot liquid with concentrated PG (e.g., from 30 wt% PG in gas phase to 90 wt% PG in the liquid phase), which would significantly solubilize the PAHs and enhance their desorption from soils. The results also revealed that the effluents derived from the PG-mixed steam could be purified by removing the desorbed PAHs using a simple coagulation treatment, and the recovered PG solution could be reused. The plant assay using wheat seeds showed that the remediated soil had a good regreening potential. Our results demonstrate that PG-mixed steam injection is a promising thermal desorption method for an efficient and sustainable remediation of PAHs-contaminated soil.

Quantitative analysis of TCE biodegradation pathway in landfill cover utilizing continuous monitoring, droplet digital PCR and multi-omics sequencing technology

The remediation of volatile chlorinated hydrocarbons in the quasi-vadose zone has become a significant challenge. We applied an integrated approach to assess the biodegradability of trichloroethylene to identify the biotransformation mechanism. The formation of the functional zone biochemical layer was assessed by analyzing the distribution of landfill gas, physical and chemical properties of cover soil, spatial-temporal variations of micro-ecology, biodegradability of landfill cover soil and distributional difference metabolic pathway. Real-time online monitoring showed that trichloroethylene continuously undergoes anaerobic dichlorination and simultaneous aerobic/anaerobic conversion-aerobic co-metabolic degradation on the vertical gradient of the landfill cover system and reduction in trans-1,2-dichloroethylene in the anoxic zone but not 1,1-dichloroethylene. PCR and diversity sequencing revealed the abundance and spatial distribution of known dichlorination-related genes within the landfill cover, with 6.61 ± 0.25 × 104–6.78 ± 0.09 × 106 and 1.17 ± 0.78 × 103–7.82 ± 0.07 × 105 copies per g/soil of pmoA and tceA, respectively. In addition, dominant bacteria and diversity were significantly linked with physicochemical factors, and Mesorhizobium, Pseudoxanthomonas and Gemmatimonas were responsible for biodegradation in the aerobic, anoxic and anaerobic zones. Metagenome sequencing identified 6 degradation pathways of trichloroethylene that may occur in the landfill cover; the main pathway was incomplete dechlorination accompanied by cometabolic degradation. These results indicate that the anoxic zone is important for trichloroethylene degradation.

Ability of marine-derived fungi isolated from polluted saline environment for enzymatic hydrocarbon remediation.

Marine-derived fungi have attracted much attention due to their ability to present a new biosynthetic diversity. About 50 fungal isolates were obtained from Tunisian Mediterranean seawater and then screened for the presence of lignin-peroxidase (LiP), manganese-dependent peroxidase (MnP), and laccase (Lac) activities. The results obtained from both qualitative and quantitative assays showed that four of marine fungi isolates had a high potential to produce lignin-degrading enzymes. They were characterized taxonomically by a molecular method, based on international spacer (ITS) rDNA sequence analysis, as Chaetomium jodhpurense (MH667651.1), Chaetomium maderasense (MH665977.1), Paraconiothyrium variabile (MH667653.1), and Phoma betae (MH667655.1) which have been reported as producers of ligninolytic enzyme in the literature.The enzymatic activities and culture conditions were optimized using a Fractional Factorial design (2 7- 4). Then, fungal strains were incubated with the addition of 1% of crude oil in 50% of seawater for 25days to evaluate their abilities to simultaneously degrade hydrocarbon compounds and to produce ligninolytic enzymes. The strain P. variabile exhibited the highest crude oil degradation rate (48.3%). Significant production of ligninolytic enzymes was recorded during the degradation process, which reached 2730 U/L for the MnP, 410 U/L for LiP, and 168.5 U/L for Lac. The FTIR and GC-MS analysis confirmed that the isolates rapidly biodegrade crude oil under ecological and economic conditions.

Remediation of Polycyclic Aromatic Hydrocarbons Contaminated Soil Using Combined Ozonation and Peroxy-Acid Treatment in the Site of Abadan Oil Refinery

Remediation of Polycyclic Aromatic Hydrocarbons Contaminated Soil Using Combined Ozonation and Peroxy-Acid Treatment in the Site of Abadan Oil Refinery

Remediation of petroleum hydrocarbon-contaminated groundwater by biochar-based immobilized bacteria

It is essential to research the technology for effective remediation of petroleum hydrocarbon-contaminated groundwater because the petroleum hydrocarbon contamination of groundwater is becoming more and more serious. The petroleum hydrocarbon-degrading bacteria screened in this experiment were identified as Pseudomonas spp. by 16 S rDNA sequencing. Using wheat straw biochar as the carrier, a highly stable immobilized bacteria integrating adsorption and degradation was prepared by microbial immobilization technology. The results of scanning electron microscopy and Fourier transform infrared spectroscopy analysis showed that the microorganisms were adsorbed on the biochar. Degradation of petroleum hydrocarbon by immobilized bacteria conformed to the second-order kinetic model. For the manufacture of immobilized bacteria, the following immobilization parameters worked best: immobilization pH of 7 and immobilization time of 24 h. Finally, the produced immobilized bacteria were added to four groundwater samples with various initial concentrations of petroleum hydrocarbon, and it was found that all of the petroleum hydrocarbon degradations were above 95%. The study can serve as a useful resource for groundwater petroleum hydrocarbon remediation technology since the immobilized bacteria can successfully adapt to the groundwater petroleum hydrocarbon environment and significantly reduce the concentration of petroleum hydrocarbon.

Regulating the electrokinetic delivery of Tween 80 and persulfate for remediating low-permeability phenanthrene contaminated soil: Importance of reducing unproductive consumption

Controllable delivery of persulfate (PS) and the enhancement of oxidative availability of pollutants in in-situ oxidative remediation of low-permeability polycyclic aromatic hydrocarbons (PAHs) contaminated soil are crucial. To tackle the above challenges, the coupling of Tween 80 solubilization enhanced oxidation of phenanthrene (PHE) in low-permeability soil under electrokinetic remediation (EKR) was proposed. Firstly, batch degradation experiments showed that the addition of Tween 80 significantly inhibited the degradation of PHE in soil under thermally activated PS, as the dosage of Tween 80 increased from 0 % to 1 % with the corresponding removal rate declining from 99.19 % to 40.90 %. Accordingly, in-situ electrokinetic delivery of Tween 80 and PS was regulated in further EKR, intending to reduce unproductive consumption. PS was more uniformly delivered to the whole remediation regions from the cathode chamber by electromigration, while Tween 80 was transported into the soil from the anode chamber by electroosmosis, which made Tween 80 solubilization and PS oxidation achieve synergistic effect. And the total removal rate of PHE reached 64.90 % under this strategy, which had increased by 415.90 % and 8.76 %− 130.14 % compared with only EKR or EKR coupling single enhanced technology, respectively. After further thermal activation of transported PS at 50 ℃ by electrical resistance heating, the total removal rate of PHE increased to 71.58 %. EPR spectrum indicated that SO4.- and OH. were responsible for the degradation of PHE.

Mechanism of nitro-byproducts formation during persulfate-based electrokinetic in situ oxidation for remediation of anthracene contaminated soil

Persulfate-based electrokinetic (EK) chemical oxidation appears to be a novel and viable strategy for the in situ remediation of polycyclic aromatic hydrocarbons (PAHs) polluted soil; however, the possible toxic byproducts of PAHs have been overlooked. In this study, we systematically investigated the formation mechanism of the nitro-byproducts of anthracene (ANT) during the EK process. Electrochemical experiments revealed that NH4+ and NO2- originating from nitrate electrolyte or soil substrates were oxidized to NO2• and NO• in the presence of SO4•-. Liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS/MS) analysis with 15N labeling revealed the formation of nitro-byproducts (14 kinds), including 1-hydroxy-4-nitro-anthraquinone and its similar derivatives, 4-nitrophenol, and 2,4-dinitrophenol. The nitration pathways of ANT have been proposed and described, mainly including the formation of hydroxyl-anthraquinone-oxygen and phenoxy radicals and the subsequent addition of NO2• and NO•. ANT-based formation of nitro-byproducts during EK, which is usually underestimated, should be further investigated due to their enhanced acute toxicity, mutagenic effects, and potential threat to the ecosystem.

Temporal moment-based approach to understand the dissolved-phase LNAPL recovery and associated characteristics in the porous system under dynamic groundwater table conditions

Abstract The dissolved-phase hydrocarbon recovery can be the first step in decontaminating the soil–water system if spilled with light/dense non-aqueous phase liquid (L/D-NAPL). This study proposes a temporal moment-based approach to investigate the effectiveness of groundwater table manipulations for recovering dissolved-phase byproducts of light non-aqueous phase liquid (LNAPL) from the subsurface system. Temporal moments were computed utilizing experimentally observed and HYDRUS-simulated dissolved-phase toluene concentration data, representative of LNAPL, under stable and dynamic groundwater table fluctuation (GWTF) scenarios. Zeroth temporal moment (ZTM) showed that the hydrocarbon mass recovery varied from 1,804 to 5,190.6 mg/L × h, with the highest variation for the rapid GWTF scenario. An increase in the ZTM of hydrocarbon was observed with an increase in the rate of change of magnitude of the water table and pore velocity fluctuation as in the case of a rapid GWTF as compared to a stable GWTF case. The value of mean residence time for the stable groundwater table case was highest for the entire experimental duration, followed by slow, general, and rapid cases. Temporal moment analysis revealed that the high dissolved-phase hydrocarbon recovery could be achieved by manipulating groundwater table conditions. The present study provides a powerful technique to improve dissolved hydrocarbon remediation in mineral aquifers using hydrological restorations.

Peroxymonosulfate-assisted photocatalysis by a novel Ti3C2-based heterojunction catalyst (g-C3N4/Ti3C2/MnFe2O4) for enhanced degradation of naphthalene

Given the urgency of polycyclic aromatic hydrocarbons (PAHs) remediation and a lack of recoverable efficient catalysts for advanced oxidation processes (AOPs), a novel g-C3N4/Ti3C2/MnFe2O4 (CTM) catalyst based on the co-catalyst function of Ti3C2 (MXene) was fabricated via in situ calcination and liquid surface self-assembly, employed in a peroxymonosulfate (PMS) -assisted photocatalytic system to degrade naphthalene (NAP). Almost 100% of the NAP was removed within 45 min with pseudo-first-order kinetic constants about 2.74 and 1.97 times of those in the absence of Ti3C2 or visible light, respectively, confirming the positive role of the moderate Ti3C2 and the synergism between PMS activation and photocatalysis. The effect of initial solution pH, various inorganic anions, and actual water conditions on the reaction and stability tests revealed the potential of CTM catalysts in practical applications. There existed both free radical and non-radical pathways for NAP degradation, in which singlet oxygen (1O2) was identified as the main reactive oxygen species. This study provided a promising perspective for the rational design of efficient and stable Ti3C2-based heterojunction catalysts and their application in PMS-assisted photocatalytic systems for the effective degradation of persistent organic pollutants.

Development of novel kinetic model based on microbiome and biochar for in-situ remediation of total petroleum hydrocarbons (TPHs) contaminated soil

A novel kinetic model has been developed to explain the degradation of total petroleum hydrocarbons. Microbiome engineered biochar amendment may result in a synergistic impact on degradation of total petroleum hydrocarbons (TPHs). Therefore, the present study analyzed the potential of hydrocarbon-degrading bacteria A designated as Aeromonas hydrophila YL17 and B as Shewanella putrefaciens Pdp11 morphological characterized as rod shaped, anaerobic and gram-negative immobilized on biochar, and the degradation efficiency was measured by gravimetric analysis and gas chromatography-mass spectrometry (GC-MS). Whole genome sequencing of both strains revealed the existence of genes responsible for hydrocarbon degradation. In 60 days remediation setup, the treatment consisting of immobilization of both strains on biochar proved more efficient with less half-life and better biodegradation potentials compared to biochar without strains for decreasing the content of TPHs and n-alkanes (C12–C18). Enzymatic content and microbiological respiration showed that biochar acted as a soil fertilizer and carbon reservoir and enhanced microbial activities. The removal efficiency of hydrocarbons was found to be a maximum of 67% in soil samples treated with biochar immobilized with both strains (A + B), followed by biochar immobilized with strain B 34%, biochar immobilized with strain A 29% and with biochar 24%, respectively. A 39%, 36%, and 41% increase was observed in fluorescein diacetate (FDA) hydrolysis, polyphenol oxidase and dehydrogenase activities in immobilized biochar with both strains as compared to control and individual treatment of biochar and strains. An increase of 35% was observed in the respiration rate with the immobilization of both strains on biochar. While a maximum colony forming unit (CFU/g) was found 9.25 with immobilization of both strains on biochar at 40 days of remediation. The degradation efficiency was due to synergistic effect of both biochar and bacteria based amendment on the soil enzymatic activity and microbial respiration.

Filamentous fungi for sustainable remediation of pharmaceutical compounds, heavy metal and oil hydrocarbons.

This review presents a comprehensive summary of the latest research in the field of bioremediation with filamentous fungi. The main focus is on the issue of recent progress in remediation of pharmaceutical compounds, heavy metal treatment and oil hydrocarbons mycoremediation that are usually insufficiently represented in other reviews. It encompasses a variety of cellular mechanisms involved in bioremediation used by filamentous fungi, including bio-adsorption, bio-surfactant production, bio-mineralization, bio-precipitation, as well as extracellular and intracellular enzymatic processes. Processes for wastewater treatment accomplished through physical, biological, and chemical processes are briefly described. The species diversity of filamentous fungi used in pollutant removal, including widely studied species of Aspergillus, Penicillium, Fusarium, Verticillium, Phanerochaete and other species of Basidiomycota and Zygomycota are summarized. The removal efficiency of filamentous fungi and time of elimination of a wide variety of pollutant compounds and their easy handling make them excellent tools for the bioremediation of emerging contaminants. Various types of beneficial byproducts made by filamentous fungi, such as raw material for feed and food production, chitosan, ethanol, lignocellulolytic enzymes, organic acids, as well as nanoparticles, are discussed. Finally, challenges faced, future prospects, and how innovative technologies can be used to further exploit and enhance the abilities of fungi in wastewater remediation, are mentioned.

Hydrocarbon Utilizing and Metal Tolerant Bacteria Simultaneously Degrade Hydrocarbons and Detoxify Metals in Petroleum Contaminated Soil

Petroleum contamination to our biosphere particularly soil and water is due to release of petroleum products from petrochemical industries and is now a day’s biggest problem to the mankind. Present work was conducted to assess capability of hydrocarbon-utilizing and metal tolerant bacteria to degrade hydrocarbons and remediate metals in the soil contaminated with petroleum with the aim to form super bio-inoculants to restore soil to its original state. In order to achieve above goal, petroleum contaminated soil was observed for hydrocarbons using GC-MS, a total of 25 hydrocarbons were found in petroleum polluted soil with hydrocarbon concentration of 3738 mg/kg. Petroleum polluted soil was also observed for total bacterial population which was observed as 2.10 × 106 CFU/g of soil. Strains YSA-7 and YSA-8 showed highest potential for hydrocarbon-utilization with an absorbance of 0.681 and 0.614 respectively. Strains were also highly tolerant to Cu and Zn with tolerance of 600 µg/ml (Cu) and 1500 µg/ml (Zn) by strain YSA-7 and 700 µg/ml (Cu) and 1800 (Zn) µg/ml by strain YSA-8. Strains YSA-7 and YSA-8 were identified by 16 SrRNA as Lysinibacillus fusiformis and Stenotrophomonas maltophilia, respectively. After 20 days of incubation, Lysinibacillus fusiformis strain YSA-7 and Stenotrophomonas maltophilia YSA8 degraded all twenty-five (25) compounds but there was complete degradation of 13 compounds by strain YSA-7 and 17 compounds by strain YSA-8 using GC-MS. Both strains (YSA-7 and YSA8) were significant and efficient for removing Cu and Zn using mechanism of biosorption at different pH, metal concentrations and time of incubation. Remediation of hydrocarbons and metals under in vitro conditions suggests that the inoculation of such bacteria to petroleum contaminated soil possessing mixture of contaminants such as hydrocarbons and metals can remove such pollutants from contaminated environment and can restore such habitat to its original state.

Solubilization and remediation of polycyclic aromatic hydrocarbons in groundwater by cationic surfactants coupled nanobubbles: Synergistic mechanism and application

Polycyclic aromatic hydrocarbons pose a severe threat to groundwater and the soil environment. Improving the efficiency of the surfactant-enhanced remediation (SER) technique is a research hotspot. Nanobubbles (NBs) were introduced to enhance the solubilization effect of cationic surfactant dodecyltrimethylammonium bromide (DTAB) on phenanthrene (PHE). The interaction between NBs and DTAB was favorable in reducing the critical micelle concentration of DTAB. The equilibrium solubilization of DTAB to PHE was upgraded by up to 30.4% with the synergy of NBs. The effect of DTAB concentration on the stability of NBs was an essential reason for the different upgrade rates. The kinetic study showed that the process of equilibrium solubilization was accelerated, while NBs were “consumed”. Based on the classic DLVO framework, OH– and inorganic ions in groundwater can participate in the formation of micelles and change the double electric layer thickness of bubbles, which are the key factors affecting the stability of NBs. The results revealed the colloidal interface characteristics and the particle behavior of micelles with NBs, providing new insight into the combined application of micelles or vesicles with NBs.

Experimental investigation on electromagnetic induction thermal desorption for remediation of petroleum hydrocarbons contaminated soil

A novel electromagnetic induction low temperature thermal desorption treatment (EMI LTTD) for petroleum hydrocarbons contaminated soil was introduced in this work. The removal rate of total petroleum hydrocarbons (TPH) under various factors, the morphology changes of soils as well as removal mechanism were investigated. Results suggested that increasing the heating temperature significantly increased the removal rate of TPH. At the beginning of 20 min, most of hydrocarbons (93.44–96.91 wt%) was removed with the temperature ranged from 200 °C to 300 °C. Besides, the initial contaminants concentration, particle size and thickness of soil slightly influenced the removal rate of TPH. Desorption kinetic study demonstrated that first-order model was well-described for desorption behavior. Response surface methodology analysis showed the temperature of 216 °C, the residence time of 21 min and the moisture content of 18% was an optimum condition recommended for potentially practical application. Under this condition, the results for the composition of hydrocarbons based on carbon number fractions indicated that the fractions of C10∼C16, C17∼C22 still existed in soil, while C23∼C28 was not detected after EMI LTTD treatment. Proposed mechanism was both hydrocarbons removed by evaporation at any temperature, while parts of heavy hydrocarbons was cracked within the soil close to induction medium, resulting in re-adsorption of light hydrocarbons. A buckwheat germination and growth test indicated that soil treated by EMI LTTD was potential in reutilization for planting.