Optimal Degradation Conditions Research Articles

Coal fly ash-supported ZnO-promoted TiO2 towards UV photocatalytic degradation of anthraquinone dye: Parametric optimization, kinetics and mechanism studies

Heterogeneous photocatalysis via combination of catalyst and UV irradiation is one of the most promising advanced oxidation processes for degradation of water-soluble organic contaminants. Herein, different photocatalysts (ZnO/CFA, TiO2/CFA, and TiO2-ZnO/CFA) were synthesized via sol-gel and impregnation techniques and applied for the degradation of acid blue 25 (AB25) dye in aqueous solution under UV light in a photoreactor. Various spectroscopic techniques (XRF, XRD, BET, FTIR, UV–vis DRS, TEM and EDS) were employed to evaluate the chemical structure, functional groups, textural, and optical properties of the binary and ternary composites. TiO2-ZnO/CFA displayed rapid degradation of AB25 as compared to ZnO/CFA and TiO2/CFA, owing to the dualistic photocatalytic sites. The prepared TiO2-ZnO/CFA composite was used in synergy with the photoreactor for photocatalytic degradation process optimization, and the optimum degradation conditions in relation to initial AB25 concentration (10 mg/L), UV light intensity (18 W/m2), flow rate (12.5 L/h), and irradiation time (150 min) as input parameters were determined using Taguchi design approach. The maximum photocatalytic degradation efficiency was 98.79±0.94% under those aforementioned conditions, indicating that the synergies between the photoreactor and the TiO2-ZnO/CFA photocatalyst resulted in the effective destruction of AB25 dye molecules. Furthermore, the spent photocatalyst was easily removed from the degraded solution and reused up to nine times. After 150 mins of UV irradiation with TiO2-ZnO/CFA photocatalyst, almost complete mineralization of AB25 solution was achieved.

Microbial degradation mechanism and pathway of the insecticide thiamethoxam by isolated Bacillus Cereus from activated sludge

The high water solubility and ecotoxicity of thiamethoxam (TMX) is a potential hazard to ecosystems and human health. Here, a strain of Bacillus cereus with high TMX degradation activity was isolated from the sediment of the A2O process in the wastewater treatment plant and was able to utilize TMX as its sole carbon source. Under different environmental conditions, the degradation efficiency of TMX by Bacillus cereus-S1 (strain S1) ranged from 41.0% to 68.9% after 216 h. The optimum degradation conditions were DO = 3.5 mg/L and pH 9.0. The addition of an appropriate carbon-to-nitrogen ratio could accelerate the degradation of TMX. A plausible biodegradation pathway has been proposed based on the identified metabolites and their corresponding degradation pathways. TMX can be directly converted into Clothianidin (CLO), TMX-dm-hydroxyl and TMX-Urea by a series of reactions such as demethylation, oxadiazine ring cleavage and C=N substitution by hydroxy group. The main products were TMX-dm-hydroxyl and TMX-Urea, the amount of CLO production is relatively small. This study aims to provide a new approach for efficient degradation of TMX; furthermore, strain S1 is a promising biological source for in situ remediation of TMX contamination.

Degrading characteristics of oil‐degrading bacteria and its study of petroleum hydrocarbon metabolites

AbstractExploring the community characteristics of petroleum degrading bacteria and revealing the types of petroleum metabolites produced by degrading bacteria play an important role in solving the problem of oil pollution. In this study, the bacterial suspension was extracted from the sludge of the sewage treatment plant, and the efficient dominant bacteria were enriched and cultured by microbial screening. The optimal environmental conditions and kinetic behavior of microbial degradation of petroleum hydrocarbons in groundwater were discussed, and the metabolites of microbial degradation of petroleum hydrocarbons were analyzed. The results showed that the optimum degradation conditions of the strain were as follows: bacterial suspension inoculum: 2%, pH: 7, temperature: 30°C, initial concentration of contaminated water sample: 500 mg/L. Under these conditions, the microbial petroleum hydrocarbon degradation efficiency was 84.7% and followed the first‐order kinetics; qualitative and quantitative statistical analysis of the metabolites of the microbial degradation of petroleum hydrocarbons by gas chromatography‐time‐of‐flight mass spectrometry was performed. A total of 10 significantly upregulated products and 12 significantly downregulated products were screened, which were significantly different from the metabolites of the control group. Further microbial community analysis showed that Pseudomonas was dominant in the bacterial suspension, more than 99.5%, which was significantly different from the sludge sample, providing data support for the degradation of petroleum hydrocarbons by Pseudomonas. This study has provided a scientific basis for in situ remediation of petroleum pollution in groundwater.

Boosting tetracycline degradation by integrating MIL-88A (Fe) with CoFe2O4 persulfate activators

Iron-based metal organic framework MIL-88A (Fe)/CoFe2O4 nanocomposites were successfully prepared by hydrothermal synthesis for catalytic degradation of tetracycline (TC) via persulfate (PS) activation process. A comprehensive characterization of the produced materials was conducted to elucidate their surface textures, element composition, and structural features. This comprehensive assessment employed various investigative techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FT-IR), and Brunauer-Emmett-Teller (BET) analysis. The results showed that pristine MIL-88A (Fe), CoFe2O4, and the MIL-88A (Fe)/CoFe2O4 nanocomposites were successfully synthesized with high purity. MIL-88A (Fe)/CoFe2O4 catalyst significantly boosted the TC degradation efficiency with a typical rate exceeding twice that of unique CoFe2O4. The catalytic performance was influenced by several factors, including pH, initial TC concentration, catalyst amount, and persulfate (PS) concentration. The optimal conditions for TC degradation were as follows: pH 6.8, 10 mg/L initial TC concentration, 1.0 mg/L PS concentration, and 250 mg/L MIL-88A (Fe)/CoFe2O4 catalyst. The MIL-88A (Fe)/CoFe2O4-PS system could degrade 90% of 10 mg/L TC at room temperature for 1 h reaction time. The pseudo-second order kinetics described the best the TC degradation process (r2 =0.9466 for optimal conditions), corresponding to a rate constant of 0.0117 L/min.mg. The successful degradation of TC catalyzed by the MIL-88A (Fe)/CoFe2O4-PS was a collaborative effort, with SO4•- radicals leading the charge and HO• radicals contributing a significant role. The impressive ability of MIL-88A (Fe)/CoFe2O4 to degrade TC persisted beyond three cycles, with its efficiency staying above 82%, revealing its robustness and potential for practical applications.

Modeling and Optimization of Hybrid Fenton and Ultrasound Process for Crystal Violet Degradation Using AI Techniques

This study conducts a comprehensive investigation to optimize the degradation of crystal violet (CV) dye using the Fenton process. The main objective is to improve the efficiency of the Fenton process by optimizing various physicochemical factors such as the Fe2+ concentration, H2O2 concentration, and pH of the solution. The results obtained show that the optimal dosages of Fe2+ and H2O2 giving a maximum CV degradation (99%) are 0.2 and 3.13 mM, respectively. The optimal solution pH for CV degradation is 3. The investigation of the type of acid for pH adjustment revealed that sulfuric acid is the most effective one, providing 100% yield, followed by phosphoric acid, hydrochloric acid, and nitric acid. Furthermore, the examination of sulfuric acid concentration shows that an optimal concentration of 0.1 M is the most effective for CV degradation. On the other hand, an increase in the initial concentration of the dye leads to a reduction in the hydroxyl radicals formed (HO•), which negatively impacts CV degradation. A concentration of 10 mg/L of CV gives complete degradation of dye within 30 min following the reaction. Increasing the solution temperature and stirring speed have a negative effect on dye degradation. Moreover, the combination of ultrasound with the Fenton process resulted in a slight enhancement in the CV degradation, with an optimal stirring speed of 300 rpm. Notably, the study incorporates the use of Gaussian process regression (GPR) modeling in conjunction with the Improved Grey Wolf Optimization (IGWO) algorithm to accurately predict the optimal degradation conditions. This research, through its rigorous investigation and advanced modeling techniques, offers invaluable insights and guidelines for optimizing the Fenton process in the context of CV degradation, thereby achieving the twin goals of cost reduction and environmental impact minimization.

Removal of ofloxacin using a porous carbon microfiltration membrane based on in-situ generated •OH

This study investigated the removal performance of ofloxacin (OFL) by a novel electro-Fenton enhanced microfiltration membrane. The membranes used in this study consisted of metal-organic framework derived porous carbon, carbon nanotubes and Fe2+, which were able to produce hydroxyl radicals (•OH) in-situ via reducing O2 to hydrogen peroxide. Herein, membrane filtration with bias not only concentrated the pollutants to the level that could be efficiently treated by electro-Fenton but also confined/retained the toxic intermediates within the membrane to ensure a prolonged contact time with the oxidants. After validated by experiments, the applied bias of −1.0 V, pH of 3 and electrolyte concentration of 0.1 M were the relatively optimum conditions for OFL degradation. Under these conditions, the average OFL removal rate could be reach 75% with merely 5% membrane flux loss after 4 cycles operation by filtrating 1 mg/L OFL. Via decarboxylation reaction, piperazinyl ring opening, dealkylation and ipso substitution reaction, etc., OFL could be gradually and efficiently degraded to intermediate products and even to CO2 by •OH. Moreover, the oxidation reaction was preferred to following first-order reaction kinetics. This research verified a possibility for antibiotic removal by electro-enhanced microfiltration membrane.

G-C3N4/graphene oxide/SnFe2O4 ternary composite for the effective sunlight-driven photocatalytic degradation of methylene blue.

A broadly used dye, methylene blue (MB), adversely impacts human health and water resources, which triggers efficient methods for its elimination. Semiconductor-based heterogeneous photocatalysis is an environmentally friendly approach that effectively degrades organic pollutants. The purpose of the current work is to elucidate and validate the application of a promising g-C3N4/GO/SnFe2O4 (CGS) composite for the environmental remediation of methylene blue dye. The ternary CGS composite has been synthesized using a solvothermal approach. The fabricated composites were analyzed through FTIR, XRD, SEM/EDX, UV-VIS spectroscopy, TEM, and XPS. The photoactivity of composites and affecting parameters (pH, H2O2 dosage, composite amount, initial dye concentration, and irradiation time) were observed in sunlight illumination. The optimal conditions for photocatalytic degradation were pH = 5, photocatalyst dosage = 30 mg/100 mL, H2O2 dosage = 6 mM, and initial dye concentration (IDC) of 10 ppm employing ternary CGS composite, and MB dye was degraded effectively within 1 h. Ninety-eight percent degradation efficacy was attained by employing ternary CGS composite under the optimized conditions. Scavenging analysis suggested that •OH radicals were the key reactive oxygen species (ROS) responsible for the photodegradation of MB dye. Furthermore, the CGS nanocomposite exhibited outstanding recyclability of 84% after five consecutive runs, demonstrating its potential for use in practical applications, particularly pollutant removal.

Trinity strategy prepared high-performance biochar for peroxydisulfate activation to degrade tetracycline

In this study, a novel high-performance biochar (BNC) was prepared using a trinity strategy of liquid templates, B/N co-doping, and one-step pyrolysis for activating peroxydisulfate (PDS) to degrade tetracycline (TC). The catalytic activity of BNC can be tuned by varying the boron doping ratio and pyrolysis temperature. Of these, the optimized product, BNC-2–900, degraded 80 % of TC (50 mg/L) in 30 min. The high degradation efficiency was attributed to the accelerated electron transfer originated by graphite N, CO, and B-N-C functional groups of BNC, in which the non-radical pathways containing electronic transfer and 1O2-mediated oxidation were indicated as the primary pathways for TC degradation. Furthermore, Box-Behnken design (BBD) was employed to optimize various operating parameters in the BNC/PDS system whereby optimal degradation conditions were determined: Initial TC concentration was 20 mg/L; PDS dosage was 64.57 mg; BNC dosage was 70.91 mg; Temperature was 50 °C; Initial pH was 8.3, where the TC degradation rate reached 100 %. This study provides a novel trinity strategy that combines stability, environmental friendliness, and facility for developing heteroatom-doped carbonaceous catalysts.

A novel pbd gene cluster responsible for pyrrole and pyridine ring cleavage in Rhodococcus ruber A5

Pyridine and pyrrole, which are regarded as recalcitrant chemicals, are released into the environment as a result of industrial manufacturing processes, posing serious hazards to both the environment and human health. However, the pyrrole degradation mechanism and the pyridine-degrading gene in Rhodococcus are unknown. Herein, a highly efficient pyridine and pyrrole degradation strain Rhodococcus ruber A5 was isolated. Strain A5 completely degraded 1000 mg/L pyridine in a mineral salt medium within 24 h. The pyridine degradation of strain A5 was optimized using the BoxBehnken design. The optimum degradation conditions were found to be pH 7.15, temperature 28.06 ℃, and inoculation amount 1290.94 mg/L. The pbd gene clusters involved in pyridine degradation were discovered via proteomic analysis. The initial ring cleavage of pyridine and pyrrole in strain A5 was carried out by the two-component flavin-dependent monooxygenase PbdA/PbdE. The degradation pathways of pyridine and pyrrole were proposed by the identification of metabolites and comparisons of homologous genes. Additionally, homologous pbd gene clusters were found to exist in different bacterial genomes. Our study revealed the ring cleavage mechanisms of pyrrole and pyridine, and strain A5 was identified as a promising resource for pyridine bioremediation.

Boosted electrocatalytic oxidation of organophosphorus pesticides by a novel high-efficiency CeO2-Doped PbO2 anode: An electrochemical study, parameter optimization and degradation mechanisms

This article presents a novel and highly efficient electrocatalytic degradation method for two significant organophosphorus pesticides, fenitrothion (FEN), and methyl parathion (MPN), using a Ti/β-PbO2-CeO2 modified anode (indirect oxidation). A comprehensive electrochemical investigation was also carried out to gain new insight into the redox behavior and destruction pathway of these pesticides (direct oxidation). The study also explores the effects of various operating parameters, such as initial solution pH, applied current density, and initial pesticides concentration, on the conversion-paired electrocatalytic removal process. To further enhance the degradation efficiency, a new configuration of the electrochemical cell was designed, employing two types of electrodes and two independent power supply devices. The conversion paired electrocatalytic degradation process of these pesticides involves first the direct reduction of FEN (or MPN) on a graphite cathode and then the indirect oxidation of reduced FEN (or MPN) by hydroxyl radicals electro generated on the Ti/β-PbO2-CeO2 anode. The synergism of these two processes together will effectively lead to FEN (or MPN) degradation. The degradation percentages of 98% for FEN and 95% for MPN at the optimal conditions for the electrochemical degradation of these pesticides were achieved at pH = 7, initial concentration 50 mg L−1, with a current density of 90 mA cm−2 for direct reduction and 11 mA cm−2 for indirect oxidation. Overall, this study presents a promising and efficient approach for the remediation of organophosphorus pesticide-contaminated environments, offering valuable insights into the electrochemical degradation process and highlighting the potential for practical application in wastewater treatment and environmental protection.

Evaluating the potential of wax impregnated reactive components for long-term acenaphthene removal

The catalytic oxidation of acenaphthene (ANA) was investigated using a controlled-release persulfate candle (PSC) and Fe(II) candle (Fe(II)C) to provide long-lasting oxidation conditions during groundwater remediation. To the best of our knowledge, this study is the first attempt to compare the pseudo-first-order rate constant (kobs) and % removal of ANA oxidation using PSC/Fe(II)C, PS solution (PSaq)/Fe(II) solution (Fe(II)aq), PSC/Fe(II)aq, and PSaq/Fe(II)C systems. The kobs and % removal of ANA in the PSC/Fe(II)C system exceeded those in the other systems. The optimal degradation conditions used were 0.1 mM ANA; 3.08 mM equilibrium concentration of PS (Ce,PS) released from PSC (controlled-release rate constant, kcr = 7.731 day−1); 5.673 mM equilibrium concentration of Fe(II) (Ce,Fe(II)) released from Fe(II)C (kcr = 3.796 day−1); unadjusted pH (~7.0); and 25 °C. Radical scavenger studies and electron spin resonance (ESR) spectra showed that sulfate (SO4•−) and hydroxyl (•OH) radicals were involved in the ANA oxidation, but •OH was the dominant radical species in the PSC/Fe(II)C system. Cl−, SO42−, and HCO3− acted as radical scavengers. The introduction of hydroxylamine (HA) into the PSC/Fe(II)C system resulted in a notable enhancement of ANA removal efficiency, increasing it from 51.8 % to 82.6 % within 10 min. Additionally, the PSC/Fe(II)C + HA system exhibited a higher Fe(II) consumption efficiency of 96.6 %, surpassing that of the PSC/Fe(II)aq + HA system, which registered an efficiency of 88.6 %. Intermediate byproducts after 24 h of reaction were detected as non-toxic byproducts by liquid chromatography-mass spectrometry (LC-MS). The PSC/Fe(II)C system would be beneficial for the remediation of polycyclic aromatic hydrocarbons in groundwater due to the continuous supply of Fe(II) and PS for a long time.

Submerged arc plasma treatment of landfill leachate with a high proportion of refractory organics: Degradation performance and biodegradability enhancement

Efficient treatment of landfill leachate remains a challenge because of the load and highly stable recalcitrant organics. Herein, pre-treatment of real stabilized leachate was realized in a submerged arc plasma (SAP) reactor to which microbubbles with different carrier gases (air, N2, and O2) were introduced to preserve the subsequent biological process. We performed a detailed parametric analysis (applied voltage, electrode material, carrier gas, and initial pH) to determine the optimum operational conditions of organics degradation and leachate biodegradability improvement. Besides, degradation kinetics, reaction mechanism, and electrical energy consumption were studied during the SAP process. Ion exchange resin was initially used to effectively reduce the ionic strength of the bulk solution to allow expanding the plasma discharge area. The biodegradability of leachate was outstandingly enhanced, as reflected by an increase in BOD5/COD ratio from 0.08 to 0.68 in O2 discharge within 120 min. Meanwhile, stainless-steel as a grounded electrode outperformed aluminum, brass, and copper. The SAP also exhibited excellent performance for organics decomposition, which was found to follow second-order and approximately pseudo-second-order kinetics. Meanwhile, the possible mechanism of organics destruction was proposed based on COD measurements and reactive species trapping experiments, demonstrating the prevailing contribution of H2O2 and 1O2, among others. Nonetheless, the SAP process of leachate treatment required relatively high energy consumption (18,400 kWh/m3). The study demonstrated an effective and robust pre-treatment process for the subsequent bioremediation of landfill leachate containing chemically stable and recalcitrant organics not treatable by conventional techniques.

Effect of laccase extracted from fungi using food industrial residues as culture medium on degradation of chlorpyrifos in solution

Chlorpyrifos is one of the most widely used organophosphate insecticides in the world. Its extensive application has resulted in water and soil pollution and even disruption of biogeochemical cycles. In the current study, laccase extracted from the fungus Trametes versicolor using apple pomace as culture medium was used for the degradation of chlorpyrifos in solution. A series of experimental factors affecting enzyme catalysis including pH, temperature, substrate concentration, and enzyme activity were investigated as well as the enzyme degradation kinetics. Results showed that enzyme kinetic parameters such as Vmax and Km were obtained using the Michaelis-Menten equation with the values of 0.313 mg L−1 h−1 and 10.07 mg L−1, respectively. The optimal conditions for effective degradation of chlorpyrifos are pH of 2–6 and temperature of 20 °C with removal percentages of 62.2 %–67.3 % and 76.8 %, respectively. More than 50 % removal of chlorpyrifos was obtained with laccase activity higher than 250 U L−1. The findings suggest that laccase produced by fungi obtained from food processing residues could be a good candidate for chlorpyrifos degradation, especially under acid conditions. This study provides a new perspective on the biodegradation of organophosphate pesticides and a theoretical basis for the practical application of laccase in the remediation of soil and water polluted by chlorpyrifos.

Utilization of Ferrate Ion (FeO42-) as Oxidizing Agent for Reducing Color Intensity of Peat Water

Peat water from Central Kalimantan is generally yellow to brownish-red in color. It causes peat water to not be used as a source of water for daily needs. Humic acid, fulvic acid, and humin are organic compounds that cause peat water to become colored. One alternative step that can be taken for reducing the color intensity of peat water is to degrade color-causing organic compounds by using an oxidizing agent. A hexavalent form of iron ion (Fe6+), commonly called ferrate (FeO42-) in potassium ferrate compound, is a powerful oxidizing agent used in the present study. Potassium ferrate (K2FeO4) was synthesized by a wet oxidation method and characterized using a UV-Vis spectrophotometer and an X-Ray Diffractometer (XRD). The ferrate solution is purplish-red in color with a maximum wavelength of 510 nm. The XRD pattern shows strong diffraction peaks at 2θ which are characteristic of K2FeO4. The ferrate solution was then used to degrade color-causing organic compounds in the peat water from Central Kalimantan. Determination of the optimum degradation conditions was monitored by the absorbance decrease of organic compounds in peat water at a wavelength of 370 nm. The results showed that ferrate solution with a concentration of 80 ppm was able to degrade organic compounds in peat water at pH 8, with a removal efficiency of 100%. Keywords: oxidizing agent, ferrate ion (FeO42-), peat water

Study on synergistic catalytic degradation of wastewater containing polyacrylamide catalyzed by low-temperature plasma-H2O2.

The degradation behavior of polyacrylamide (PAM) solution by low-temperature plasma was investigated, and the effect of some factors that might affect the degradation process was further examined. The PAM solution was treated with low-temperature plasma generated by dielectric barrier discharge (DBD) combined with H2O2 and a Mn + Cu/AC composite catalyst. The optimal conditions for the oxidation degradation of a PAM solution using low-temperature plasma-H2O2-Mn + Cu/AC were determined as follows: initial concentration of 1000mg/L, discharge voltage of 18kV, H2O2 addition of 2%, and catalyst addition of 810mg. The results indicated that the degradation rate increased with the increase of the catalyst dosage at the same discharge time. The degradation rate of 180min increases from 90 to 97.6% with an increase in voltage from 16 to 18kV, and the molecular weight decreases from 2,720,204.23 to 1,370,815.54. The degradation effect caused by the change of H2O2 addition was considerable compared with other factors. When the discharge time was 180min, the degradation rate increased 26.3% with the increase of 1.6% H2O2 addition. Under the optimal process conditions, the addition of the catalyst resulted in a more rapid initial decrease in the pH value of the solution compared to the system without the catalyst.

Fabrication of new composite NCuTiO2/CQD for photocatalytic degradation of ciprofloxacin and pharmaceutical wastewater treatment: degradation pathway, toxicity assessment

In this research, the photocatalytic degradation of CIP from aqueous solutions using CQD decorated on N-Cu co-doped titania (NCuTCQD) was made during two synthesis steps by sol–gel and hydrothermal methods. The fabricated catalysts were analyzed using various techniques, including XRD, FT-IR, BET, FESEM, EDX, and DRS. The results showed that N and Cu atoms were doped on TiO2 and CQD was well deposited on NCuT. The investigation of effective operational parameters demonstrated that the complete removal of ciprofloxacin (CIP: 20 mg/L) could be achieved at pH 7.0, NCuTCQD4wt%: 0.8 g/L, and light intensity: 100 mW/cm2 over 60 min reaction time. The O2•– and OH˙ radicals were identified as the primary reactive species during the decontamination process. The synthesized photocatalyst could be recycled after six consecutive cycles of CIP decomposition with an insignificant decrease in performance. Pharmaceutical wastewater was treated through the optimum degradation conditions which showed the photocatalytic degradation eliminated 89% of COD and 75% of TOC within 180 min. In the effluent toxicity evaluation, the EC50 values for treated and untreated pharmaceutical wastewater increased from 62.50% to 140%, indicating that the NCuTCQD4wt%/Vis system can effectively reduce the toxic effects of pharmaceutical wastewater on aquatic environments.

Preparation and potential antitumor activity of alginate oligosaccharides degraded by alginate lyase from Cobetia marina

It is of great significance to develop marine resources and study its potential biological activity by using alginate lyase produced by marine psychrophilic bacteria. In the previous study, a new marine psychrophilic bacterium (Cobetia marina HQZ08) was screened from the growth area of Laminaria japonica, and it was found that the strain could efficiently produce alginate-degrading enzyme (Aly30). In this paper, the ability of Aly30 to degrade alginate was optimized and the optimal degradation conditions were obtained. It was found that the main degradation product of alginate oligosaccharides was trisaccharide. In vitro cell experiments showed that the antitumor activity of low molecular weight alginate oligosaccharides was better than that of high molecular weight alginate oligosaccharides. In summary, Aly30 had the potential to produce alginate oligosaccharides with low degree of polymerization and antitumor activity, which provided a reference for the enzymatic preparation and application of alginate oligosaccharides.

Bioremediation by bacteria isolated from water contaminated with hydrocarbons

Oil pollution is currently a global problem. However, an oil-contaminated ecology is rich in microorganisms that may utilize petroleum oil and hydrocarbons for growth, feeding, and metabolic processes. In the present study, fifty polluted water samples were collected from five stations (ten samples each) in the Al-Fahama oil refinery in eastern Baghdad. The water contamination parameters of these collected water samples were detected. Then, the percentage of water contamination with some heavy metals (zinc, lead, and cadmium) and radioactive elements (uranium, cesium and actinium) was measured. The proportions of these elements were compared within their limits permitted by the World Health Organization (WHO). Fifty-nine bacterial isolates were isolated from polluted water, and 24 isolates of them succeeded in analyzing crude oil. The results of the current study showed that seven isolates belong to the genus Citrobacter amalonaticus (29.16%), six isolates belong to Enterobacter cloacae (25%), three isolates belonged to both Pseudomonas aeruginosa (12.5%) and Ochrobacterum anthropi (12.5%), and human Ochrobacterum. With a percentage of 12.5%, two isolates of Serratia marcescens (8.3%) and one isolate of each Pseudomonas fluorescens, Serratia fonticola, and Burkholderia pseudomallei (4.16%) of each. The optimum of some conditions for the decomposition process was determined in terms of (pH, temperature and crude oil concentration) and the results showed that the optimum degradation conditions were 35°C at pH equal to 7.5 in the presence of 2% of crude oil. Several experiments were conducted to determine the most efficient isolates for oil analysis. Burkholderia pseudomallei and Pseudomonas fluorescens are the most active bacterial species in their oil degradation. Genes responsible for hydrocarbon analysis were revealed in twenty-four bacterial isolates using a polymerase chain reaction (PCR) assay. The results showed that the ALKB gene (alkane hydroxylase) was observed in all bacterial isolates that succeeded in analyzing crude oil with a percentage equal to 100%, NahAc gene (naphthalene dioxygenase) has been recorded in four isolates (16.7%), these four bacterial isolates were Burkholderia pseudomallei, Pseudomonas aeruginosa, Ochrobacterum anthropic, and Pseudomonas fluorescens. Generally, the isolation rate of both C. amalonaticus and E. cloacae isolates was higher than in other studies, which may be due to the hydrocarbon pollution in isolation; both B. pseudomallei and P. fluorescens isolates were the highest active bacterial species in their oil degradation. Genetic results showed that the AlkB gene was the domain compared with other degradation genes used in the current study, followed by NahAc gene. Keywords: Bioremediation, heavy metal, B. pseudomallei, hydrocarbons, crude oil

Optimizing the degradation of aflatoxin B1 in corn by Trametes versicolor and improving the nutritional composition of corn.

Corn, being an important grain, is prone to contamination by aflatoxin B1 (AFB1 ), and AFB1 -contaminated corn severely endangers the health of humans and livestock. Trametes versicolor, a fungus that can grow in corn, possesses the ability to directly degrade AFB1 through its laccase. This study aimed to optimize the fermentation conditions for T. versicolor to degrade AFB1 in corn and investigate the effect of T. versicolor fermentation on the nutritional composition of corn. AFB1 -contaminated corn was used as the culture substrate for T. versicolor. A combination of single-factor experiments and response surface methodology was employed to identify the optimal conditions of AFB1 degradation. The optimal conditions of AFB1 degradation were as follows: 9 days of fermentation, a fermentation temperature of 26.7 °C, a moisture content of 70.5% and an inoculation amount of 4.9 mL (containing 51.99 mg of T. versicolor mycelia). With the optimal conditions, the degradation rate of AFB1 in corn could reach 93.01%, and the dry basis content of protein and dietary fiber in the fermented corn was significantly increased. More importantly, the lysine content in the fermented corn was also significantly increased. This is the first report that direct fermentation of AFB1 -contaminated corn by T. versicolor not only efficiently degrades AFB1 but also improves the nutritional composition of corn. These findings suggest that the fermentation of corn by T. versicolor is a promising, environmentally friendly and efficient approach to degrade AFB1 and improve the nutritional value of corn. © 2023 Society of Chemical Industry.

Simultaneous degradation of contaminants of emerging concern and disinfection by solar photoelectro-Fenton process at circumneutral pH in a solar electrochemical raceway pond reactor

Simultaneous contaminants of emerging concern (CECs) removal and wild microorganisms’ inactivation was evaluated by applying solar photoelectro-Fenton (SPEF) process in actual secondary effluent collected from a real municipal wastewater treatment plant (MWWTP). 20 L of a mixture of four CECs was used as model pollutants (200 μg/L of acetaminophen, caffeine, sulfamethazine, and sulfamethoxazole each one). The SPEF process was carried out on fully sunny days, at circumneutral pH using the complex Fe3+-EDDS, in a solar electrochemical – raceway pond reactor (SEC-RPR). Initially, the optimal conditions for CECs degradation were determined using a response surface model based on current density, iron complex concentration and Fe3+-EDDS addition time (to allow previous accumulation of H2O2) as model inputs. A current density of 24.6 mA/cm2, a Fe3+-EDDS complex concentration of 0.089 mM and 3.8 min of previous H2O2 accumulation were the resulting optimum conditions that were afterwards applied for the simultaneous degradation of the CECs synthetic mixture and wild microorganisms inactivation in actual secondary effluent. About 85% CECs removal and complete E. coli inactivation were achieved in 30 min, approximately, while E. faecalis and total coliforms could be inactivated under detection limit in 60 min and 75 min, respectively.