Remediation Of Hydrocarbons Research Articles

Microbe mediated remediation of dyes, explosive waste and polyaromatic hydrocarbons, pesticides and pharmaceuticals.

Industrialization and human activities have led to serious effects on environment. With the progress taking place in the biodegradation field, it is important to summarize the latest advancement. In this review, we intend to provide insights on the recent progress on the biodegradation of environmental contaminants such as dyes, pesticides, pharmaceuticals, explosive waste and polyaromatic hydrocarbons by microorganisms. Along with the biodegradation of environmental contaminants, toxicity effects have also been discussed.

Induced systemic tolerance mediated by plant-microbe interaction in maize (Zea mays L.) plants under hydrocarbon contamination

The present investigation was committed to examining the effect of soil spiked with diesel contamination (0, 1.5, 2.5, 3.5 g diesel kg−1 soil) on maize (Zea mays L) varieties (MMRI yellow and Pearl white) with or without bacterial consortium (Pseudomonas aeruginosa BRRI54, Acinetobacter sp. strain BRSI56, Acinetobacter sp. strain ACRH80). Seed and soil bacterial inoculation were done. The studied morphological attributes were fresh and dry weight of shoot and root of both maize varieties. The results documented that bacterial consortium caused 21%, 0.06% and 29%, 34% higher shoot and root fresh/dry weights in “Pearl white” and 14%, 15% and 32%, 22% shoot and root fresh/dry weights respectively in MMRI yellow under control conditions. The biochemical attributes of shoot and root were affected negatively by the 3.5 g diesel kg−1 soil contamination. Bacterial consortium enhanced enzymatic activity (APX, CAT, POD, SOD, GR) and non-enzymatic (AsA, GSH, Pro, α-Toco) antioxidant and reduction in oxidative stress (H2O2, MDA) under hydrocarbon stress as compared to non-inoculated ones in both root and shoot organs. Among both varieties, the highest hydrocarbon removal (75, 64, and 69%) was demonstrated by MMRI yellow with bacterial consortium as compare to Pearl white showed 73, 57, 65% hydrocarbon degradation at 1.5 2.5, 3.5 g diesel kg−1 soil contamination. Consequently, the microbe mediated biotransformation of hydrocarbons suggested that the use of PGPB would be the most beneficial selection in diesel fuel contaminated soil to overcome the abiotic stress in plants and successfully remediation of hydrocarbon in contaminated soil.

Plant- and microbe-assisted biochar amendment technology for petroleum hydrocarbon remediation in saline-sodic soils: A review

Soil degradation through salinization and pollution by toxic compounds such as petroleum hydrocarbons (PHCs) in the coastal wetlands has become a significant threat to ecosystem health, biodiversity, and food security. However, traditional remediation technologies can generate secondary pollutants, incur high operating costs, and consume significant quantities of energy. Bioremediation, using plants, biochar, and microbes, is an innovative and cost-effective option to remediate contaminated soils. Biochar, as a plant/microbe growth enhancer, is a promising green approach for the sustainable phytoremediation of PHCs in salinized soils. This review therefore summarizes the effect of plant- and microbe-assisted biochar amendment technology for the remediation of PHCs and salinization. Plant-microbe interactions mediated rhizodegradation despite increasing hydrocarbon sorption. Overall, microbial respiration is more active in biochar amendments, due to faster biodegradation of PHCs and improved soil properties. The use of biochar, plants, and microbes is recommended, as it offers a practical and sustainable option, both ecologically and economically, for the remediation of PHCs and excess salinity. Further development of new green technologies is to be encouraged.

The dominant microbial metabolic pathway of the petroleum hydrocarbons in the soil of shale gas field: Carbon fixation instead of CO2 emissions

In shale gas mining areas, indigenous microorganisms degrade organic pollutants such as petroleum hydrocarbons into carbon dioxide (CO2) and water (H2O) through aerobic metabolism. A large quantity of CO2 emissions will exacerbate the “Greenhouse effect”. Based on the clean sieved soil and oil-based drilling fluid in the shale gas mining area, this experiment set three concentration gradients (3523 ± 159 mg/kg, 8715 ± 820 mg/kg and 22,031 ± 1533 mg/kg) to treat the soil, and each group was disposed for the same amount of time (63 days). By analyzing the dynamic changes of microbial diversity and the abundance of key functional genes for carbon fixation, the impact of petroleum hydrocarbons on carbon fixation potential was discovered, and the natural attenuation law of petroleum hydrocarbons in contaminated soil was explored. It provided the scientific research basis of ecology for the carbon cycle, carbon allocation, and carbon fixation in microbial remediation of petroleum hydrocarbon contaminated soil. The results obtained indicated the following: i) The removal rate of petroleum hydrocarbons under high-concentration pollution (45.33 ± 3.90%) was significantly lower than low and medium-concentration pollution. The TPH concentration removal rate of each group was the largest in the early stage of culture (1-5d), and there was no significant correlation between the TPH content and the community composition (R2 = 0.0736, P > 0.05). ii) Composition and function of Carbon Fixation associated microbiota were assessed by 16S rRNA sequencing and PICRUSt (phylogenetic investigation of communities by reconstruction of unobserved states) analysis. The main carbon fixation pathway in this study is the reductive citric acid cycle, because there was no shortage of enzymes that can affect subsequent reactions.

The catabolic pathways of in situ rhizosphere PAH degraders and the main factors driving PAH rhizoremediation in oil-contaminated soil.

Rhizoremediation is a potential technique for polycyclic aromatic hydrocarbon (PAH) remediation; however, the catabolic pathways of in situ rhizosphere PAH degraders and the main factors driving PAH rhizoremediation remain unclear. To address these issues, stable-isotope-probing coupled with metagenomics and molecular ecological network analyses were first used to investigate the phenanthrene rhizoremediation by three different prairie grasses in this study. All rhizospheres exhibited a significant increase in phenanthrene removal and markedly modified the diversity of phenanthrene degraders by increasing their populations and interactions with other microbes. Of all the active phenanthrene degraders, Marinobacter and Enterobacteriaceae dominated in the bare and switchgrass rhizosphere respectively; Achromobacter was markedly enriched in ryegrass and tall fescue rhizospheres. Metagenomes of 13 C-DNA illustrated several complete pathways of phenanthrene degradation for each rhizosphere, which clearly explained their unique rhizoremediation mechanisms. Additionally, propanoate and inositol phosphate of carbohydrates were identified as the dominant factors that drove PAH rhizoremediation by strengthening the ecological networks of soil microbial communities. This was verified by the results of rhizospheric and non-rhizospheric treatments supplemented with these two substances, further confirming their key roles in PAH removal and in situ PAH rhizoremediation. Our study offers novel insights into the mechanisms of in situ rhizoremediation at PAH-contaminated sites.

A novel modified fenton-like process for efficient remediation of anthracene-contaminated soils before analysis by ultraviolet–visible spectroscopy

Due to the persistence of polycyclic aromatic hydrocarbons (PAHs) in soil and sediments, and their toxic, mutagenic, and carcinogenic effects, the remediation of PAH-contaminated sites is an important role for environment pollution. In this study, the chemical oxidative remediation of anthracene-contaminated soils was investigated by magnetite nanoparticles (Fe3O4) catalyzed Fenton-like oxidation in the presence of hydrogen peroxide 30% (H2O2) and urea-hydrogen peroxide (UHP) at neutral pH. Urea-hydrogen peroxide (UHP), as a safer oxidizing agent, is used for the first time in the Fenton process. The magnetite nanoparticles improved the production of hydroxyl radicals, and the removal of polycyclic aromatic hydrocarbons (anthracene as a model compound) from the soil samples. The structure of Fe3O4 nanoparticles was characterized by FT-IR, XRD, SEM, and vibrating sample magnetometer (VSM). The removal efficiency of anthracene at an initial concentration 2500 (mg kg-1) was 95% for 2.5 mmol by using hydrogen peroxide and 93% for 0.1 mmol of UHP at the optimum oxidation condition. The anthracene reaction was analyzed by ultraviolet-visible spectroscopy (UV-Vis). The UHP safety and efficiency, neutral pH condition, the limited iron leaching and its easy magnetic separation makes magnetite nanoparticles-UHP a promising catalytic system in remediation of polycyclic aromatic hydrocarbons in contaminated soils.

UV Assisted Photocatalytic Remediation of Polycyclic Aromatic Hydrocarbons (Pahs) in Sewage Sludge Addition Soils Using Synthesized Nanometer Mixed-crystal TiO2: Experiment and Simulation

ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) entering into soils via sewage sludge could be posing arresting environmental risks. Photocatalytic remediation has been considered as a powerful tool of degrading PAHs in soils. In the present study, a synthesized nanometer mixed-crystal TiO2 was employed to investigate its effects on PAHs degradation in soils by Ultra Violet (UV).Two typical substances of PAHs widely detected in sewage sludge (phenanthrene and pyrene), were added into soils from farmland to provide polluted soil for a series of simulated experiments. These polluted soil samples were mixed with five different levels of the synthesized TiO2 (0, 1%, 2%, 3%, and 4%, wet weights) and the decreases of PAHs under different conditions were compared. The results showed that among the five treatments, the activities of the synthesized photocatalysts followed the order of 0<1%<2%<4%<3%, and the 3% of TiO2 addition was determined as the optimum condition. Moreover, it was found that the degradation of PAHs could increase with the increasements of H2O2, photon flux, and humic substances in treated soils. Our findings supports the perspective of using nanometer synthesized mixed-crystal TiO2 in the degradation of PAHs in contaminated soils by sewage sludge addition and provides hints on understanding the mechanism of developing photocatalytic remediation in PAHs-contaminated soils.

Robust bioinspired surfaces and their exploitation for petroleum hydrocarbon remediation.

The current improvement in science and engineering, actively dealing with surfaces and interfaces, turns into a functioning control with a thriving advancement propensity. Superlyophobic/superlyophilic phenomena in surface sciences have pulled in broad considerations of researchers and specialists. Inspired by the natural and living organism, researchers have designed different biomimetic materials with exceptional surface wettability, such as the smart wetting of asymmetric spider silk surfaces. These smart materials with superlyophobic/superlyophilic wettability are generally utilized for water assortment, self-cleaning, fluid transportation and separation, and many researchers' domains. Among them, emulsion separation, including division of oil-water blend, mixtures of immiscible liquids and oil-water emulsions, is highlighted by an increasing number of researchers. Numerous materials with one- and two-dimensional morphology, smart surfaces, and super wettability have been effectively designed and utilized in various scientific research applications. We expect that these bioinspired materials with super wettability can have promising applications in practical for emulsion destabilization and liquid transportation.

Enhanced electrokinetically-delivered persulfate and alternating electric field induced thermal effect activated persulfate in situ for remediation of phenanthrene contaminated clay

Delivering persulfate (PS) efficiently into clay is an unsolved challenge. This study proposes a novel strategy with enhanced electrokinetically -delivery PS into clay by using PS for continuously flushing cathode to inhibit water electrolysis at cathode electrode. On this basis, a novel approach of heating soil by alternating current (AC) was used to thermally activate PS in situ. Results show that the mass transfer efficiency of PS by electroosmotic flow is about 20 times that by electromigration. Moreover, when PS was added in the anode chamber, using PS solution continuously flushing cathode created a relatively balanced the influent and effluent flow rates, significantly improving the mass transfer efficiency of PS. Compared to using NaNO3 solution flushing, a significant increase of 51.7% was achieved, reaching 78.8%, for the phenanthrene (PHE) average degradation rate in soil cell. In contrast, the best overall PHE removal rate was observed, reaching 87.8%, by a cycle strategy of enhanced electrokinetically -delivered PS followed by AC heating applied. Electron paramagnetic resonance spectroscopy analysis showed oxidative radicals (SO4∙−/•OH) were the major species responsible for enhanced PHE degradation. These results demonstrate that this cycle strategy is a viable method for remediation of polycyclic aromatic hydrocarbons in clay.

Bioremediation of polycyclic aromatic hydrocarbons from an aged contaminated agricultural soil using degrading bacteria and soil amendments

The combined effects of degrading bacteria (Paracoccus sp. LXC), humic acid (HA), and soil amendments, including chicken manure, biochar, and wormcast, were investigated through 84 d of incubation in order to improve the remediation of polycyclic aromatic hydrocarbon (PAH) in aged contaminated agricultural soil. PAH concentrations and dissipation kinetics were analyzed, and the biomass and communities of microorganisms and soil enzyme activities were examined to clarify the possible mechanism. The highest removal efficiency of PAHs was 42.1% when treated with Paracoccus sp. LXC combined with biochar and HA. PAH dissipation was consistent with the first-order kinetics model and the half-life of PAHs decreased from 2323.3 d in the natural attenuation to 103–277 d in the amended microcosms. Soil amendments and HA promoted the development of PAH-degrading bacteria and diversity of bacterial communities in soil but not that of fungi. The removal efficiency of PAHs was positively correlated with the density of PAH-degrading bacteria and soil urease (Ure), dehydrogenase (Deh), and manganese-dependent peroxidase (Mnp) activities (r = 0.824–0.941, p < .01). The Paracoccus sp. LXC apparently removed 2–4-ring PAHs, and biochar and wormcast were effective in removing 2–4-ring and 5–6-ring PAHs, respectively. The combined bioremediation strategy using degrading bacteria with soil amendments and HA has high potential for PAH removal in aged contaminated agricultural soil and the possible mechanism was the combination of bioaugmentation with Paracoccus sp. LXC and biostimulation with HA and soil amendments.

Combination of Nonionic Surfactants with Thermal-activated Persulfate for Simultaneous Removal of Phenanthrene and Pyrene from Alluvial Soil: A Kinetic Study

ABSTRACT Polycyclic aromatic hydrocarbons have adverse effects on the organisms, plants, and soil structure. Therefore, they should be removed by an appropriate and effective method. In this study, simultaneous removal of 500 mg/kgsoil of phenanthrene and pyrene was investigated for the individual and combined application of Tween 80, Triton X-100, and sodium persulfate from the alluvial soil. The results revealed that the maximum removal efficiencies of phenanthrene (94.06 ± 0.30%) and pyrene (90.07 ± 0.19%) were observed in the presence of Triton X-100 + sodium persulfate (0.5 M) within 1 hour, respectively. Also, individual application of surfactants and sodium persulfate had efficiencies of less than 80%. It should be noted that the removal of phenanthrene and pyrene followed the first-order kinetic model. Economic evaluations of combined treatment demonstrated that the application of more proportion of Triton X-100 (10000 mg/L) + less proportion of sodium persulfate (0.3 M) is more cost-effective for the remediation of soil in the field study. Based on the results, the combined application of the washing process by Triton X-100 and persulfate oxidant can significantly improve the removal efficiencies and is a promising technique in the remediation of polycyclic aromatic hydrocarbons contaminated soil.

Design of a Microbial Remediation Inoculation Program for Petroleum Hydrocarbon Contaminated Sites Based on Degradation Pathways.

This paper analyzed the degradation pathways of petroleum hydrocarbon degradation bacteria, screened the main degradation pathways, and found the petroleum hydrocarbon degradation enzymes corresponding to each step of the degradation pathway. Through the Copeland method, the best inoculation program of petroleum hydrocarbon degradation bacteria in a polluted site was selected as follows: single oxygenation path was dominated by Streptomyces avermitilis, hydroxylation path was dominated by Methylosinus trichosporium OB3b, secondary oxygenation path was dominated by Pseudomonas aeruginosa, secondary hydroxylation path was dominated by Methylococcus capsulatus, double oxygenation path was dominated by Acinetobacter baylyi ADP1, hydrolysis path was dominated by Rhodococcus erythropolis, and CoA path was dominated by Geobacter metallireducens GS-15 to repair petroleum hydrocarbon contaminated sites. The Copeland method score for this solution is 22, which is the highest among the 375 solutions designed in this paper, indicating that it has the best degradation effect. Meanwhile, we verified its effect by the Cdocker method, and the Cdocker energy of this solution is −285.811 kcal/mol, which has the highest absolute value. Among the inoculation programs of the top 13 petroleum hydrocarbon degradation bacteria, the effect of the best inoculation program of petroleum hydrocarbon degradation bacteria was 18% higher than that of the 13th group, verifying that this solution has the best overall degradation effect. The inoculation program of petroleum hydrocarbon degradation bacteria designed in this paper considered the main pathways of petroleum hydrocarbon pollutant degradation, especially highlighting the degradability of petroleum hydrocarbon intermediate degradation products, and enriching the theoretical program of microbial remediation of petroleum hydrocarbon contaminated sites.

Extremophilic Exopolysaccharides: Biotechnologies and Wastewater Remediation.

Various microorganisms thrive under extreme environments, like hot springs, hydrothermal vents, deep marine ecosystems, hyperacid lakes, acid mine drainage, high UV exposure, and more. To survive against the deleterious effect of these extreme circumstances, they form a network of biofilm where exopolysaccharides (EPSs) comprise a substantial part. The EPSs are often polyanionic due to different functional groups in their structural backbone, including uronic acids, sulfated units, and phosphate groups. Altogether, these chemical groups provide EPSs with a negative charge allowing them to (a) act as ligands toward dissolved cations as well as trace, and toxic metals; (b) be tolerant to the presence of salts, surfactants, and alpha-hydroxyl acids; and (c) interface the solubilization of hydrocarbons. Owing to their unique structural and functional characteristics, EPSs are anticipated to be utilized industrially to remediation of metals, crude oil, and hydrocarbons from contaminated wastewaters, mines, and oil spills. The biotechnological advantages of extremophilic EPSs are more diverse than traditional biopolymers. The present review aims at discussing the mechanisms and strategies for using EPSs from extremophiles in industries and environment bioremediation. Additionally, the potential of EPSs as fascinating biomaterials to mediate biogenic nanoparticles synthesis and treat multicomponent water contaminants is discussed.

Lessons learned from 20 years of molecular biological tools in petroleum hydrocarbon remediation

AbstractStakeholders of petroleum hydrocarbon‐contaminated (PHC) sites aim to meet remediation goals cost‐effectively. But contaminated sites are typically complex, and when inefficient remediation strategies are implemented, time and money are wasted. Various strategies can be implemented for site remediation and almost all at some point involve a biological component. Therefore, during site characterization, seeing the complete picture by obtaining multiple lines of evidence—chemistry (concentrations of contaminants and daughter products), geochemistry (redox status, electron acceptors, electron donors), microbiology (species and their genes for catalyzing biodegradation of reactions, i.e., functional genes), and the contaminant degradation ongoing at baseline (stable isotope methods)—is critically important for selecting the best remediation strategy. Additionally, molecular biological evidence is important for monitoring treatment progress and informing decisions to retreat, change treatments, or transition to monitored natural attenuation.

Remediation of polycyclic aromatic hydrocarbons by sulfate radical advanced oxidation: Evaluation of efficiency and ecological impact

Remediation of polycyclic aromatic hydrocarbon (PAH) contamination in soil remains expensive and difficult. Sulfate radical advanced oxidation processes (SR-AOPs) can be used for in situ PAH oxidation but their efficiency and ecological impacts require evaluation. Here, we tested the remediation efficiency and ecological impacts of an SR-AOP combining sodium persulfate and ferrous sulfate (FS), the FS SR-AOP with the chelating agent citric acid (FS+CA), and the FS SR-AOP with chelating agent and the surfactant IGEPALCA-720 (FS+CA+IG) compared with natural attenuation (control, CK). We measured PAH, soil physicochemical properties (pH, soil organic matter [SOM]), and soil biological properties (polyphenol oxidase [PPO] activity, peroxidase [POD] activity, soil microbes) in contaminated soil samples after incubation with FS, FS+CA, FA+CA+IG, or CK for 1, 15, and 30 d. Compared with CK, all SR-AOPs significantly decreased PAH after 1 d, with FS+CA+IG showing the highest efficiency (80.8%) and PAH removal peaking at 15 d. FS+CA+IG treatment reduced SOM the least and soil pH the most; after 30 d, SOM recovered to ~80% of the level observed in CK, but soil pH decreased further. PPO and POD activities were highest after 15 and 30 d of FS+CA+IG treatment. Real-time quantitative PCR demonstrated that SR-AOPs significantly decreased quantities of PAH-degrading bacteria, soil bacteria, fungi, and actinobacteria at 1 d, but after 30 d, the microbes recovered to levels similar to those observed in CK, with no significant differences among SR-AOPs. SR-AOPs reduced bacterial diversity and changed the dominant phylum from Acidobacteria to Firmicutes. In summary, SR-AOP treatment with both the chelating agent and the surfactant produced the best PAH removal and least SOM destruction but the largest pH decrease, although some factors recovered with longer incubation. This study provides key information for improving PAH remediation and evaluating its ecological impact

Interactive effect of biochar and compost with Poaceae and Fabaceae plants on remediation of total petroleum hydrocarbons in crude oil contaminated soil

The current study was dedicated to finding the effect of soil amendments (biochar and compost) on plants belonging to Poaceae and Fabaceae families. Plants selected for the phytoremediation experiment included wheat (Triticum aestivum), maize (Zea mays), white clover (Trifolium repens), alfalfa (Medicago sativa), and ryegrass (Lolium multiflorum). The physiological and microbial parameters of plants and soil were affected negatively by the 4 % TPHs soil contamination. The studied physiological parameters were fresh and dried biomass, root and shoot length, and chlorophyll content. Microbial parameters included root and shoot endophytic count. Soil parameters included rhizospheric CFUs and residual TPHs. Biochar with wheat, maize, and ryegrass (Fabaceae family) and compost with white clover and alfalfa (Poaceae family) improved plant growth parameters and showed better phytoremediation of TPHs. Among different plants, the highest TPH removal (68.5 %) was demonstrated by ryegrass with compost, followed by white clover with biochar (68 %). Without any soil amendment, ryegrass and alfalfa showed 59.55 and 35.21 % degradation of TPHs, respectively. Biochar and compost alone removed 27.24 % and 6.01 % TPHs, respectively. The interactive effect of soil amendment and plant type was also noted for studied parameters and TPHs degradation.

Electrokinetic remediation of petroleum hydrocarbon contaminated soil (I)

The remediation of petroleum hydrocarbons (TPH) in a contaminated soil by electrokinetic (EK) treatment was studied in the laboratory. The effects of applying a constant electrical current on soil pH, moisture content, electrical conductivity (EC), temperature, and the concentrations of three fractions of TPH (C10–C16, C17–C34 and C35–C40) were investigated. The experiment was run for seven days and soil samples were collected at the end of the 7 day period for analysis of soil pH and TPH concentration. There were extreme pH conditions near the electrodes. At the end of the experiment there was around a 37% reduction of C10–C16 chain compounds compared to the initial concentration of 164 ± 18 mg/kg. The study investigated TPH remediation to a depth of 24 cm, which is significantly more than most studies of EK remediation of TPH-contaminated soils. We observed reductions in TPH concentrations even at a depth of 24 cm. The spatial distribution of reductions in TPH concentrations was also studied and it was observed that more remediation occurred near the cathodes than near the anodes. Further, the greatest reductions in TPH concentrations were recorded near the electrodes in the lowest and middle parts of the experimental set-up. The application of electrokinetics to remediate TPH-contaminatedsoils could be a viable option as an in situ remediation technology.

Combined remediation of polycyclic aromatic hydrocarbons (PAHs) by plant and immobilized bacteria in contaminated soil

In this study, three dominant bacteria Cellulomonas flavigena (Ⅰ), Cellulomonas flavigena (Ⅱ), Sphingomonas paucimobilis (Ⅲ) from Fire Phoenix rhizosphere soil were used to develop a multi-microbial agent system. For oil-contaminated soil in the Dagang oilfield, the immobilized test bacteria were inoculated into the Fire Phoenix rhizosphere soil to examine the effects of bacterial agents on polycyclic aromatic hydrocarbons (PAHs)-contaminated soil. The results showed that PAHs degradation was promoted under the ⅠⅢ (with an effective number of viable bacteria of 109 cfu·mL-1) and ⅠⅡⅢ (with an effective number of viable bacteria of 107 cfu·mL-1) treatments. The PAHs degradation rates were 32.2% and 41.4%, respectively, being significantly higher than that in the control treatments. The ⅠⅡⅢ treatment significantly promoted the belowground biomass of Fire Phoenix, which was 31.2% higher than that of the control treatment. Our results suggested that the multi-microbial agent constructed by the three dominant bacteria ⅠⅡⅢ could be used as a strengthening method for the remediation of PAHs-contaminated soil by Fire Phoenix, which provided a novel method for microbial enhanced phytoremediation technology.

Biogenic iron oxide nanoparticles and activated sodium persulphate for hydrocarbon remediation in contaminated soil

Biogenic iron oxide nanoparticles synthesized from a locally sourced, readily available plant — Azadirachta indica, were used synergistically with sodium persulphate (PS) to degrade total petroleum hydrocarbons (TPHs) in contaminated soil. A chemometric approach to optimizing the conditions for the degradation of TPH was developed using central composite design (CCD). Characterization of iron oxide nanoparticles was carried out with X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected electron area diffraction (SAED). Analysis of TPH was carried out with gas chromatography flame ionization detector (GC-FID). The optimum condition for the complete degradation of TPH was achieved at pH 6.0 and oxidant dosage of 0.74 M within 14 h and 5 days. Iron nanoparticles AZA FeNP (1:1) and AZA FeNP (2:1) were synthesized by varying the ratio of extract/precursor. The nanoparticles displayed heterogeneous, amorphous morphology with increased agglomeration in AZA FeNP (1:1). AZA FeNP (2:1) XRD spectra exhibited characteristic peaks at 27.0°, 35.4° and 44.5°, which are attributed to iron nanoparticles. TEM and HR-TEM images confirmed spherical nanoclusters’ presence with an average size of 9.3 and 10.0 nm for AZA FeNP (1:1) and AZA FeNP (2:1), respectively. The EDX spectra displayed intense peaks of oxygen, carbon, and iron at 0.4, 0.6 and 6.4 KeV confirming the presence of FeNP. Under optimized conditions, PS alone degraded 68% TPH while 0.07 and 0.15 g/L FeNP achieved ∼93 and 95% degradation, respectively. Additionally, 0.07 and 0.15 g/L FeNP-activated PS achieved ∼99 and 100% TPH degradation, respectively. The outcome of these findings suggests that FeNP synthesized using A. indica successfully catalyzed PS for complete degradation of TPH in crude oil-contaminated soil.

Remediation of phenanthrene contaminated soil through persulfate oxidation coupled microbial fortification

The technology of chemical oxidation coupled microbial remediation of polycyclic aromatic hydrocarbons contaminated soil was efficient and friendly, but the research on the compatibility of chemical oxidation and the bioremediation is insufficient. This study was to explore the compatibility of persulfate oxidation coupled microbial degradation and promote the remediation of phenanthrene contaminated soil. The results showed that the addition of persulfate with the participation of Fe2+ caused the soil environment to be acidic and the soil pH with the lower concentrations (20, 50 mmol/L) of persulfate returned to neutral after 14 days. The content of fulvic-like and humic-like increased after adding persulfate at the same time. Persulfate inhibited the activity of soil dehydrogenase and polyphenol oxidase, simultaneously, the oxidation species generated during the persulfate oxidation process and the acidic environment (pH=4.13) led the soil microbial abundance and diversity to decrease significantly. Besides, the phenanthrene degradation bacterial consortium was screened through a gradual domestication process, which derived from activated sludge in the coking plant wastewater aeration tank of Xuzhou Weitian Chemical Co., Ltd. The efficient degrading bacteria were identified as Pantoea (95%) using high-throughput sequencing, with the 84% degradation rate of phenanthrene after the 7th day. Comparing persulfate oxidation, the removal rate of phenanthrene in the soil was increased by 33% after 63 days of the combined remediation. Adding 20 mmol/L persulfate and inoculating domesticated high-efficiency degrading bacteria Pantoea was recommended in the remediation of PAHs contaminated soil.