Diesel Removal Efficiency Research Articles

Simultaneous remediation of diesel-polluted soil and promoted ryegrass growth by non-thermal plasma pretreatment

The remediation of petroleum-polluted soil has garnered significant global attention. In this study, a pot-culture experiment was conducted to assess the feasibility of using non-thermal plasma (NTP) as an efficient and economic-friendly pretreatment method in the phytoremediation of diesel-polluted soil. The remediation effectiveness was evaluated via both the removal of diesel and the ryegrass growth. Specifically, at the 50th d of ryegrass growth, the increase of diesel removal efficiency with NTP pretreatment ranged from 16 % to 30 %. Moreover, both clean and diesel-polluted soils pretreated by NTP promoted the growth of ryegrass in shoot lengths and biomass especially after the 35th d. It was found that nitrate nitrogen fixed by NTP not only stimulated the nitrate reductase activities in leaves and promoted plant growth, but also was transformed to more ammonia nitrogen for organism life activity. Subsequent investigation proved that the related nitrogen-metabolism activities of microbes were enriched in rhizosphere soils with NTP pretreatment. Furthermore, NTP treatment increased the abundance of beneficial microbial communities in diesel soil rhizosphere on the 42nd d of growth period. In addition, changes in the proportions of soil dissolved organic matter indicated enhanced nutrient cycling in soils with NTP pretreatment. These promotional effects underscored the contribution of NTP pretreatment in rapidly detoxifying diesel-contaminated soil within 10 min and accelerated the establishment of ryegrass ecosystem. This study provides valuable insights into the role of nitrogen fixation and offers an efficient and promising advanced approach for the phytoremediation of diesel-polluted soil with NTP pretreatment.

A Comparative Study of Treatment Methods of Raw Sugarcane Bagasse for Adsorption of Oil and Diesel

Current environmental trends show an increase in pollutant concentrations in water bodies. The alarming concern this poses has made it crucial to remove pollutants from water and eliminate them, owing to the host of issues they cause to the ecosystem. While sorption is a popular method of treating wastewater, there are several concerns regarding its accessibility, affordability, efficiency, and functioning toward a circular sustainable economy. The current study focuses on the feasibility of using sugarcane bagasse (SCB) to remove oil and diesel from water and proposes to do so without turning SCB into biochar, contrary to the usual method. Raw SCB was chemically treated using sodium hydroxide and acetic acid. With little pre-treatment, it was found to have improved sorption abilities with low input materials and environmental toxicity. Sorption experiments conducted on treated and untreated SCB showed the effects of different parameters on the oil or diesel removal efficiency. Furthermore, FTIR, BET, and SEM studies were conducted to characterize the intrinsic morphology and structure of the sorbent.

Enhanced bioremediation performance of diesel-contaminated soil by immobilized composite fungi on rice husk biochar

In response to the low removal capacity and poor tolerance of fungi to diesel-contaminated soil, a novel immobilization system using biochar to enhance composite fungi was proposed. Rice husk biochar (RHB) and sodium alginate (SA) were used as immobilization matrices for composite fungi, and the adsorption system (CFI-RHB) and the encapsulation system (CFI-RHB/SA) were obtained. CFI-RHB/SA exhibited the highest diesel removal efficiency (64.10%) in high diesel-contaminated soil over a 60-day remediation period compared to the free composite fungi (42.70%) and CFI-RHB (49.13%). SEM demonstrated that the composite fungi were confirmed to be well attached to the matrix in both CFI-RHB and CFI-RHB/SA. FTIR analysis revealed the appearance of new vibration peaks in diesel-contaminated soil remediated by immobilized microorganisms, demonstrating changes in the molecular structure of diesel before and after degradation. Furthermore, CFI-RHB/SA maintains a stable removal efficiency (>60%) in higher concentrations of diesel-contaminated soil. High-throughput sequencing results indicated that Fusarium and Penicillium played a key role in the removal of diesel contaminants. Meanwhile, both dominant genera were negatively correlated with diesel concentration. The addition of exogenous fungi stimulated the enrichment of functional fungi. The insights gained from experiment and theory help to provide a new understanding of immobilization techniques of composite fungi and the evolution of fungal community structure.

Hydrophobic modification of sepiolite by fatty acids for efficient oil removal: Influence of the alkyl chain length

Oil pollution has seriously affected the ecological balance, and the development of an efficient and low-cost sorbent material to treat oil pollution is work with practical applications. In this work, a novel hydrophobic sorbent based on natural sepiolite was obtained by modifying with four saturated fatty acids with different carbon chain length and used for oil removal from water. The original and modified samples were tested for SEM, XRD, FTIR, CA, XPS and BET analysis. The results showed that the functional groups of the modifier were successfully grafted onto the sepiolite surface. The sepiolite fibers changed from the original agglomerative morphology to more dispersed with a coarser surface. The contact angle of modified sepiolite was improved greatly compared with the original sepiolite. Among them, octadecanoic acid modified sepiolite (O-SEP), with a lower water contact angle showed the best diesel removal efficiency, indicating that there was no significant positive correlation between the oil sorption efficiency and the value of the contact angle. This study presented a simple and feasible method to produce hydrophobic-based sorbents with good performance based on clay minerals that could be used for oil spill cleaning up.

Dynamics of Functional Genes and Bacterial Community during Bioremediation of Diesel-Contaminated Soil Amended with Compost.

Compost is widely used as an organic additive to improve the bioremediation of dieselcontaminated soil. In this study, the effects of compost amendment on the remediation performance, functional genes, and bacterial community are evaluated during the bioremediation of diesel-contaminated soils with various ratios of compost (0-20%, w/w). The study reveals that the diesel removal efficiency, soil enzyme (dehydrogenase and urease) activity, soil CH4 oxidation potential, and soil N2O reduction potential have a positive correlation with the compost amendment (p < 0.05). The ratios of denitrifying genes (nosZI, cnorB and qnorB) to 16S rRNA genes each show a positive correlation with compost amendment, whereas the ratio of the CH4-oxidizing gene (pmoA) to the 16S rRNA genes shows a negative correlation. Interestingly, the genera Acidibacter, Blastochloris, Erythrobacter, Hyphomicrobium, Marinobacter, Parvibaculum, Pseudoxanthomonas, and Terrimonas are strongly associated with diesel degradation, and have a strong positive correlation with soil CH4 oxidation potential. Meanwhile, the genera Atopostipes, Bacillus, Halomonas, Oblitimonas, Pusillimonas, Truepera, and Wenahouziangella are found to be strongly associated with soil N2O reduction potential. These results provide useful data for developing technologies that improve diesel removal efficiency while minimizing greenhouse gas emissions in the bioremediation process of diesel-contaminated soil.

Dynamics of Functional Genes and Bacterial Community during Bioremediation of Diesel-Contaminated Soil Amended with Compost.

Compost is widely used as an organic additive to improve the bioremediation of diesel-contaminated soil. In this study, the effects of compost amendment on the remediation performance, functional genes, and bacterial community are evaluated during the bioremediation of diesel-contaminated soils with various ratios of compost (0-20%, w/w). The study reveals that the diesel removal efficiency, soil enzyme (dehydrogenase and urease) activity, soil CH4 oxidation potential, and soil N2O reduction potential have a positive correlation with the compost amendment (p < 0.05). The ratios of denitrifying genes (nosZI, cnorB and qnorB) to 16S rRNA genes each show a positive correlation with compost amendment, whereas the ratio of the CH4-oxidizing gene (pmoA) to the 16S rRNA genes shows a negative correlation. Interestingly, the genera Acidibacter, Blastochloris, Erythrobacter, Hyphomicrobium, Marinobacter, Parvibaculum, Pseudoxanthomonas, and Terrimonas are strongly associated with diesel degradation, and have a strong positive correlation with soil CH4 oxidation potential. Meanwhile, the genera Atopostipes, Bacillus, Halomonas, Oblitimonas, Pusillimonas, Truepera, and Wenahouziangella are found to be strongly associated with soil N2O reduction potential. These results provide useful data for developing technologies that improve diesel removal efficiency while minimizing greenhouse gas emissions in the bioremediation process of diesel-contaminated soil.

Assessment of bimetallic Zn/Fe0 nanoparticles stabilized Tween-80 and rhamnolipid foams for the remediation of diesel contaminated clay soil

Diesel contamination of soil due to oil spills, disposal of refinery waste, oil exploration constitutes a major environmental problem. This paper reports the remediation of diesel contaminated clay soil using Zn/Fe0 bimetallic nanoparticle stabilized Rhamnolipid (RMLP) and Tween-80 (TW-80) surfactant foams. Fe0, and Zn (x wt%)/Fe0 (x = 0.2, 2.0, and 10.0) bimetallic nanoparticles are synthesized by using sodium borohydride reduction method. The average particle size (from FESEM) is calculated to be 62, 57, 42 and 35 nm for the Fe0, Zn (0.2)/Fe0, Zn (2)/Fe0 and Zn (10)/Fe0 nanopowders, respectively. The highest foamability and foam stability of 109.6 and 108.5 mL, respectively are observed for the RMLP (12 mg/l) surfactant foam stabilized with 6 mg/l Zn (10)/Fe0 nanoparticles. The surface tension values reduce to the lowest value of 28.1 and 31.4 mN/m with the addition of 6 mg/l of Zn (10)/Fe0 powder in RMLP and TW-80 solutions of 12 mg/l, respectively. The maximum diesel removal efficiency of 83.8 and 59%, is achieved by RMLP (12 mg/l) foam stabilized by Zn (10)/Fe0 nanoparticles (6 mg/l) for the clay soil contaminated with 100 and 500 μl/g of diesel, respectively. The physicochemical properties of the nanoparticles are studied to explain the foam properties and the remediation behavior. These findings regarding the nanoparticle stabilized foams can offer a cost-effective environment friendly commercial solution for soil remediation in the future.

Effect of Novosphingobium sp. CuT1 inoculation on the rhizoremediation of heavy metal- and diesel-contaminated soil planted with tall fescue.

Rhizoremediation is a promising method based on the synergism between plant and rhizobacteria to remediate soil co-contaminated with heavy metals and total petroleum hydrocarbons (TPHs). A plant growth-promoting (PGP) rhizobacterium with diesel-degrading capacity and heavy metal tolerance was isolated from the rhizosphere of tall fescue (Festuca arundinacea L.), after which the effects of its inoculation on rhizoremediation performance were evaluated in heavy metal- and diesel-contaminated soil planted with tall fescue. The bacterial isolate (Novosphingobium sp. CuT1) was characterized by its indole-3-acetic acid (IAA) production, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, and siderophore productivity as PGP traits. CuT1 was able to grow on 1/10 LB-agar plates containing 5mM of Cu or 5mM of Pb. To evaluate the remediation effect of heavy metal- and diesel-contaminated soil by CuT1 inoculation, the experimental conditions were prepared as follows. The soil was artificially contaminated with heavy metals (Cu and Pb) at a final concentration of 500ppm. The soil was then further contaminated with diesel at final concentrations of 0, 10,000, and 30,000ppm. Finally, all plots were planted with tall fescue, a representative hyperaccumulating plant. Compared to the rhizoremediation performance of the co-contaminated soil (Cu + Pb + diesel) without inoculation, the bioavailable Cu concentrations in the soil and the tall fescue biomass were significantly increased in CuT1 inoculation. Additionally, the root growth of tall fescue was also promoted in CuT1 inoculation. Correlation analysis showed that Cu bioavailability and bioconcentration factor were positively correlated with CuT1 inoculation. The diesel removal efficiency showed a positive correlation with CuT1 inoculation, although the diesel removal was below 30%. CuT1 inoculation was positively correlated with IAA and dehydrogenase activity in the soil. Moreover, the dry biomass of the tall fescue's roots was highly associated with CuT1 inoculation. Collectively, our findings suggest that Novosphingobium sp. CuT1 can be utilized as an applicable bioresource to enhance rhizoremediation performance in heavy metal- and TPH-contaminated soils.

Removal of diesel from soil washing effluent by electro-enhanced Fe2+ activated persulfate process

• Electro/Fe 2+ /persulfate can efficiently remove diesel from soil washing effluent. • The degradation of diesel was verified by EEM fluorescence spectroscopy. • The reactive radicals formed were identified by EPR technique. • The detoxification of soil washing effluent was evaluated by soil respiration. Electrochemical process coupling with Fe 2+ /persulfate (Fe 2+ /PDS) oxidation was applied to treat soil washing effluent containing diesel and surfactant Tween 80. The influence of several important parameters including anode material, initial pH, current density, Fe 2+ dosage and PDS dosage on the abatement of diesel by electro/Fe 2+ /PDS process was investigated. The results show that the platinum anode (Ti/Pt) could achieve higher removal of diesel in comparison with the tantalum or ruthenium-based (Ti/IrO 2 -Ta 2 O 5 and Ti/IrO 2 -RuO 2 ) anode, and lower initial pH favors diesel decay. There exist the optimal values of electricity intensity, Fe 2+ and PDS dosages for diesel elimination. Under the conditions of pH 0 3.0, 1.0 mM Fe 2+ , 10 mM PDS and 27.8 mA/cm 2 current density, 88.6 % of diesel removal efficiency was obtained while almost 70.0 % of Tween 80 could be recovered. The excitation emission matrix (EEM) fluorescence spectroscopy further verified the degradation of diesel in the electro/Fe 2+ /PDS process. Soil respiration tests were carried out to evaluate the toxicity of the soil washing effluent before and after electro/Fe 2+ /PDS process. The reactive radicals formed were identified by electron paramagnetic resonance (EPR) technique. Briefly, coupling electrolysis with Fe 2+ /PDS oxidation is demonstrated to be an effective method for the abatement of diesel from soil washing effluent with the recovery of surfactant Tween 80.

Remediation of diesel-contaminated soil by alkoxyethanol aqueous two-phase system.

The increasing diesel pollution accidents pose a serious threat to the ecological environment and human health. Remediation of diesel-contaminated soil (DCS) has attracted widespread attention during the past few decades. This work proposed an approach for the remediation of DCS by alkoxyethanol aqueous two-phase extraction (ATPE), which was an application of this small molecule aqueous two-phase system (ATPS). In addition, the influence of temperature, stirring speed, stirring time, and solid-liquid ratio on the removal of diesel was explored respectively. The removal efficiency of diesel could reach more than 97.18% in 18min. Meanwhile, ATPS had high reusability, and the removal efficiency remained above 85.17% in the reuse process. Alkoxyethanol ATPE could effectively remove diesel hydrocarbons with different carbon chain lengths and the remediation process hardly caused residual organic solvents on the soil surface according to the analysis of gas chromatography-mass spectrometry (GC-MS) and Fourier transforms infrared (FT-IR), which could be regarded as the distinct advantage compared to the traditional surfactant washing method and organic solvent extraction method. The study of soil physicochemical properties and wheat germination proved that the soil structure and properties changed little after ATPE remediation. And finally, the mechanism of alkoxyethanol ATPE was intensively discussed according to the remediation characteristic. This work provided an efficient method for the remediation of DCS and widened the application fields of alkoxyethanol ATPS as well.

Optimum conditions of zero-valent iron nanoparticle stabilized foam application for diesel-contaminated soil remediation involving three major soil types

Stability of foam, enhanced by nano zero-valent iron (nZVI) and its optimized constituents, may have significant potential for effective treatment of soil contaminated with diesel oil-a major environmental problem. The optimum diesel removal efficiency from distinct types of soil accomplished by the unique application of such foams as well as the optimum conditions of the foaming constituents have not been reported in literature so far. Hence, in this work, the removal of diesel contaminant from different soil types (desert, coastal, clay soil) is optimized, and the optimized results are reported for the first time, using response surface methodology (RSM), for alkylpolyglucoside phosphate (APG-Ph) foam, stabilized by nZVI. The effect of concentrations of APG-Ph (0.02, 0.04, 0.06, 0.08, and 0.1 volume %) and nZVI (2, 3, and 3.5mg/l) on diesel removal efficacy from soil is studied using Box-Behnken design (BBD) of response surface methodology (RSM). Maximum diesel removal efficiency obtained at a concentration of 0.1 volume % APG-Ph foam with 3.5mg/l nZVI for desert, coastal, and clay soil is 94.6, 95.3, and 57.5%, respectively. The optimum concentrations of APG-Ph and nZVI are found to be 0.98 volume % and 0.8mg/l, respectively. Validation of this optimal condition experimentally results in highest removal efficiency of 98.3, 97.2, and 75.9% for desert, coastal, and clay soil respectively. This is in good agreement with the predicted values by RSM (98.67, 97.57, and 76.85%). The maximum diesel removal efficiency predicted at optimal concentration of APG-Ph and nZVI is significantly larger than the results reported in literature in last three years.

Calcium superphosphate as an inorganic stabilizer for modified-Fenton treatment of diesel-contaminated soil with two different exogenous iron sources

Catalyzed hydrogen peroxide propagation (CHP) processes are widely applied for the remediation of petroleum hydrocarbon contaminated soils, but greatly limited by the rapid decomposition of H2O2. Although phosphate stabilizer can extend the lifetime of H2O2 in the soil systems, it is unclear about the effect of stabilizers on the processes with different exogenous iron species that are frequently added to accelerate the Fenton-like reactions. Herein, calcium superphosphate (CAP) was used as a H2O2 stabilizer in the modified-Fenton treatment of the diesel spiked soil with two exogenous iron species, a citrate chelated ferric complex (IC) and an iron mineral (γ-Fe2O3 immobilizing on montmorillonite, IB). A ratio of CAP to soil (RCS) at 1/10 can retain 49% of H2O2 within 24 h in the soil. The diesel removal efficiency in the IC based process reached 70% at 10 h after adding 480 mM H2O2 when IC and RCS were 90 mM and 1/10, which is much higher than that in the IB based process. In the latter system, only 23% diesel removal can be achieved at 48 h after adding the same dosage of H2O2 and CAP. This can be attributed to the higher concentration of hydroxyl radicals produced in the former process. The O2 detection showed that CAP can effectively retard H2O2 decomposition into O2 in the both processes. A relatively high dosage of CAP should be applied in the IC process to retain H2O2 and extend ·OH production for diesel degradation, while a relatively low dosage of CAP can promote the diesel removal by altering the O2 production through a superoxide radical mediated pathway.

Application of Fe2O3/ZrO2 loaded polyhedron ball on photocatalytic degradation of diesel pollutants in seawater under visible light.

Fe2O3/ZrO2 nanocomposite photocatalyst was successfully prepared by coprecipitation method for the degradation of diesel pollutants in seawater under visible light. The effects of doping ratio, calcination temperature, photocatalyst dosage, initial diesel concentration, H2O2 concentration, and reaction time on the photocatalytic removal efficiency were investigated. Moreover, the optimal conditions for Fe2O3/ZrO2 nanocomposite photocatalyst to degrade marine diesel pollution were determined. The removal efficiency of diesel by nanocomposite photocatalyst could reach 97.03%. A photocatalyst-loaded polypropylene polyhedral ball was prepared, and the removal efficiency of diesel by photocatalyst-loaded polypropylene polyhedral ball decreased from 99.35 to 68.84% after four recycling cycles.

Optimization of aeration enhanced surfactant soil washing for remediation of diesel-contaminated soils using response surface methodology.

Surfactant-enhanced soil washing has been used for remediation of organic pollutants for an extended period, but its effectiveness and wide application was limited by the high concentration of surfactants utilized. In this work, the efficiency of conventional soil washing performance was enhanced by 12–25% through the incorporation of air bubbles into the low concentration surfactant soil washing system. Surfactant selection pre-experiment using aerated and conventional soil washing reveals Brij 35 > TX100 > Tween 80 > Saponin in diesel oil removal. Optimization of the effect of time, surfactant concentration, pH, agitation speed, and airflow rate in five levels were undertaken using Response Surface Methodology and Central composite design. The optimum degree of variables achieved was 90 min of washing time, 370 mg/l of concentration, washing pH of 10,535 rpm of agitation speed and 7.2 l/min of airflow rate with 79.5% diesel removal. The high predicted R2 value of 0.9517 showed that the model could efficiently be used to predict diesel removal efficiency. The variation in efficiency of aeration assisted and conventional soil washing was variable depending on the type of surfactant, organic matter content of the soil, particle size distribution and level of pollutant weathering. The difference in removal efficiency of the two methods increases when the level of organic matter increases and when the particle size and age of contamination decreases.

Development of a bacterial consortium comprising oil-degraders and diazotrophic bacteria for elimination of exogenous nitrogen requirement in bioremediation of diesel-contaminated soil.

The purpose of this study was to develop an effective bacterial consortium and determine their ability to overcome nitrogen limitation for the enhanced remediation of diesel-contaminated soils. Towards this, various bacterial consortia were constructed using oil-degrading and nitrogen-fixing microbes. The diesel removal efficiency of various developed consortia was evaluated by delivering the bacterial consortia to the diesel-contaminated soils. The consortium Acinetobacter sp. K-6 + Rhodococcus sp. Y2-2 + NH4NO3 resulted in the highest removal (85.3%) of diesel from the contaminated soil. The consortium containing two different oil-degrading microbes (K-6 + Y2-2) and one nitrogen-fixing microbe Azotobactervinelandii KCTC 2426 removed 83.1% of the diesel from the soil after 40days of treatment. The total nitrogen content analysis revealed higher amounts of nitrogen in soil treated with the nitrogen-fixing microbe when compared with that of the soil supplemented with exogenous inorganic nitrogen. The findings in this present study reveal that the consortium containing the nitrogen-fixing microbe degraded similar amounts of diesel to that degraded by the consortium supplemented with exogenous inorganic nitrogen. This suggests that the developed consortium K-6 + Y2-2 + KCTC 2426 compensated for the nitrogen limitation and eliminated the need for exogenous nitrogen in bioremediation of diesel-contaminated soils.

Potential of surfactant foam stabilized by Ethylene glycol and Allyl alcohol for the remediation of diesel contaminated soil

Abstract Refined petroleum products like diesel oil enters the soil as a result of damaged pipelines and storage tanks. This constitutes a major hazard for the environment as it leads to problems associated with soil contamination. The application and impact of surfactant foam, stabilized by the use of biodegradable additives — Ethylene glycol and Allyl alcohol, for treating diesel contaminated soil is a novel concept and has not been reported so far. The aim of the current work was thus to check the diesel contaminated soil remediation potential with the usage of surfactant foam, stabilized by Ethylene glycol and Allyl alcohol. To better understand the foam properties, experiments were performed by mixing the appropriate quantities of additives and two popular surfactants — Sodium n-dodecyl sulfate (SDS), Tween 80, using Dynamic Foam Analyzer (Kruss, Germany). The stable foams produced were then utilized to treat the diesel contaminated soil and interesting results were obtained. The foam stabilized by surfactant SDS in combination with 0.3 weight% Allyl alcohol showed maximum diesel oil removal efficiency of 62%. Also, surfactant Tween 80 with 0.3 weight% of Allyl alcohol produced the most stable foam with a half-life of 18 mins and resulted in maximum diesel removal efficiency of 71%. SDS, Tween 80 foams stabilized by 0.3 weight% Ethylene glycol however produced much lower diesel removal efficiency. The mechanism of surfactant adsorption onto soil was studied. The surface tension analysis, using the different additives — Ethylene glycol, Allyl alcohol with the surfactant solutions, were performed to check on the mobilization of diesel oil from the soil.

Comparison of zero-valent iron and iron oxide nanoparticle stabilized alkyl polyglucoside phosphate foams for remediation of diesel-contaminated soils

Stable surfactant foam might play a vital role in the effective remediation of diesel oil contaminated soil-a major environmental hazard. This paper, first of its kind, is reporting the remediation of diesel-contaminated desert soil, coastal soil and clay soil by aqueous alkylpolyglucoside phosphate (APG-Ph) surfactant foams stabilized by Fe0 and Fe3O4 nanoparticles. Zero-valent iron (Fe0, ∼28 nm) and iron oxide (Fe3O4, ∼20 nm) nanoparticles are synthesized by liquid-phase reduction and precipitation methods, respectively. The effect of these nanoparticles on foamability, foam stability, surface tension and remediation of diesel-contaminated soils are examined at various concentrations (volume %) of alkylpolyglucoside phosphate (APG-Ph) surfactant and nanoparticles (mg/l). The maximum values of foamability and foam stability recorded for 0.1 vol % APG-Ph foam stabilized by 3.5 mg/l Fe0 are 108.3 and 110.4 mL, respectively. At the same conditions, the Fe3O4 results in 99.4 and 87.5 mL, respectively, depicting the better performance of Fe0. Reduction in surface tension of 0.1 vol % APG-Ph solution (50.75 mN/m) with the addition of 3.5 mg/l Fe0 (9.51 mN/m) and Fe3O4 (19.45 mN/m) nanoparticle is observed. Both the nanoparticles enhance remediation. The foam formed with 0.1 vol % APG-Ph and stabilized by 3.5 mg/l Fe0 shows the maximum diesel removal efficiency of 95.3, 94.6, and 57.5% for coastal soil, desert soil and clay soil, respectively. On the other hand, Fe3O4 (3.5 mg/l) stabilized APG-Ph foam of the same concentration shows merely 76.0, 79.6 and 51.6% diesel removal efficiency for coastal soil, desert soil, and clay soil, respectively. The rate of diesel removal by zero-valent iron and iron oxide nanoparticle stabilized foams are found to be well described by the first order kinetic model. Higher foamability, foam stability, and reducing capacity accompanying lower surface tension, compared to those of the Fe3O4 nanoparticle stabilized foam, could explain higher diesel removal efficiency of the Fe0 nanoparticle stabilized foam.

Remediation of diesel-contaminated soil by low-temperature thermal desorption

Site contamination by petroleum hydrocarbons is a widespread environmental problem in the world. One of the methods used to cleanup petroleum compounds from contaminated soils is low-temperature thermal desorption (LTTD) that uses heat to evaporate volatile pollutants from the soil. The remediation of contaminated soil by diesel using the LTTD method was studied. The effect of temperature (180 and 340 °C), residence time (from 5 to 20 min) and soil texture (two different types containing sand, Bentonite clay and Kaolinite clay) was investigated. By using the LTTD method, the maximum removal efficiency of diesel from soil type A (30% sand, 50% Kaolinite, 20% Bentonite) was 95.6% at 340 °C during a period of 20 min. Moreover, the diesel removal rate was higher in samples containing a higher percentage of Kaolinite than of Bentonite. By applying a temperature range of 180–340 °C to soils contaminated by diesel with an initial concentration of 20,000 mg kg−1, the cleanup standards of diesel range organics contaminated soils can be achieved after 23 min. The costs of thermal remediation may be reduced by reusing the waste heat generated in several industries and may cover the required heat for the LTTD process and the selected range of temperature.

Potential microbial consortium involved in the biodegradation of diesel, hexadecane and phenanthrene in mangrove sediment explored by metagenomics analysis

Hydrocarbon contamination is a serious problem that degrades the quality of mangrove ecosystems, and bioremediation using autochthonous bacteria is a promising technology to recover an impacted environment. This research investigates the biodegradation rates of diesel, hexadecane and phenanthrene, by conducting a microcosm study and survey of the autochthonous microbial community in contaminated mangrove sediment, using an Illumina MiSeq platform. The biodegradation rates of diesel, hexadecane and phenanthrene were 82, 86 and 8 mg kg−1 sediment day−1, respectively. The removal efficiencies of hexadecane and phenanthrene were >99%, whereas the removal efficiency of diesel was 88%. A 16S rRNA gene amplicon sequence analysis revealed that the major bacterial assemblages detected were Gammaproteobacteria, Deltaproteobacteria, Alphaproteobacteria. The bacterial compositions were relatively constant, while reductions of the supplemented hydrocarbons were observed. The results imply that the autochthonous microorganisms in the mangrove sediment were responsible for the degradation of the respective hydrocarbons. Diesel-, hexadecane- and phenanthrene-degrading bacteria, namely Bacillus sp., Pseudomonas sp., Acinetobacter sp. and Staphylococcus sp., were also isolated from the mangrove sediment. The mangrove sediment provides a potential resource of effective hydrocarbon-degrading bacteria that can be used as an inoculum or further developed as a ready-to-use microbial consortium for the purpose of bioremediation.

선박용 고속 디젤엔진에 적용한 디젤미립자 필터의 측정방법에 따른 입자상물질 저감효율 비교 연구

본 연구에서는 입자상물질 저감을 위해 개발한 디젤미립자 필터를 선박용 고속 디젤엔진에 적용하여 측정방법에 따른 저감효율을 비교 분석하였다. 시험에 사용된 엔진은 최고출력 403 kW의 4행정 기계식 선박용 고속 디젤엔진이며, 선박 엔진의 부하와 회전속도 제어를 위해 AC 동력계를 사용하였다. 선박 엔진 시험주기인 E3 cycle의 네 운전조건에서 저감효율을 측정하였으며, 측정방법으로는 입자상물질 및 soot의 저감특성을 살펴보기 위해 분류희석 방법과 광흡수법이 적용된 계측기를 각각 이용하였다. 디젤미립자 필터 적용에 따른 저감효율 측정 결과, 엔진허용 배압을 충족함과 동시에 입자상물질의 경우 76 ~ 91 %, soot(≈블랙카본)은 90 %이상 확인할 수 있었다. 이 결과로부터, 선박용 디젤엔진에서 배출되는 입자상물질 및 soot 저감기술로 디젤미립자 필터 적용 가능성을 확인할 수 있었다. 또한, 측정방법별 저감효율이 상이한 결과로부터 측정방법의 단일화 필요성을 확인할 수 있었다.