Time For Complete Degradation Research Articles

THE PREPARATION AND CHARACTERIZATION OF A LANTHANUM-BASED RARE EARTH CONVERSION COATING ON MAGNESIUM ALLOY AZ91D AND ITS DEGRADATION IN 3.5% NaCl SOLUTION

Magnesium alloys have a huge market and broad prospects due to their high specific strength, good ductility, and strong thermal conductivity. However, the active chemical properties of elemental magnesium and the negative standard electrode potential result in magnesium alloys being highly susceptible to corrosion and failure. Chemical conversion treatment of magnesium alloy can improve its corrosion resistance by preparing a chemical conversion film on its surface. Rare earth conversion treatment has the advantages of effortless process, moderate price, no pollution, good corrosion resistance, and synergistic effect with inorganic or organic additives, which is in line with the pursuit of “green chemical” in industrial production. At present, there is little research and application on lanthanum-based rare earth conversion coatings (La-RECC). This paper selects rare earth element lanthanum (La) to prepare La-RECC on the surface of AZ91D magnesium alloy through chemical conversion treatment. The microstructure, chemical composition, and protective properties of La-RECC were discovered, as well as their interrelationships, revealing the degradation process of La-RECC in 3.5% NaCl solution. La-RECC is composed of La(OH)3 and Mg(OH)2, exhibiting a crystal cluster structure with cracks, and there are a large number of needle-like crystals on the crystal cluster of La-RECC, with a thickness of 2.14 [Formula: see text]m. The degradation process of La-RECC can be divided into three stages: Rapid degradation, slow degradation, and complete degradation. The complete degradation time of La-RECC in 3.5% NaCl solution is 82.5[Formula: see text]h.

Green synthesis of magnetic silver nanocomposite: the photocatalytic performance of nanocomposite to decolorize organic dyes

ABSTRACT The magnetite-silver nanocomposites (Fe3O4-Ag NCs) were synthesized via a facile and green process by Citrus sinensis peel extract. The deposition of silver nanoparticles (NPs) was confirmed by observing an absorption peak at the maximum wavelength at 422 nm in the suspension solution of samples, which is related to silver surface plasmon resonance (SPR). The characteristic diffraction patterns of Fe3O4 and Ag phases were characterized utilizing the XRD patterns and the average size of the crystals was 21 nm. The photocatalytic behavior of Fe3O4-Ag NCs was studied for the destruction of three organic dyes methyl green (MG), methyl orange (MO), and methylene blue (MB) below UV radiation. The effect of the amount of photocatalyst and volume of hydrogen peroxide as an oxidant in the process of dye degradation was also investigated. The complete degradation time of dyes MB, MG, and MO under UV irradiation in the presence of 0.002 g Fe3O4-Ag NCs were 57, 33, and 49 min, respectively. The time of degradation reactions showed the high photocatalytic performance of Fe3O4-Ag NCs. These results proved that the synergistic effect of magnetite in the role of supporting the silver NPs was a significant contribution to the excellent decolorization behavior of Fe3O4-Ag NCs.

Exploring Household Composting as an Effective Solution for Urban Waste Management

Organic wastes are generated from many sources’ compiles, solid waste, food, kitchens wastes, etc. Disposal of solid waste is stinging and widespread problem in both urban and rural areas in many developed and developing countries. Collection and disposal of solid waste is one of the major problems of urban environment in most countries worldwide today. Improper Solid Waste Management causes many environmental problems. Traditional composting methods have been common practices in many rural/sub urban areas and requires more time for complete degradation. Traditional method requires large sites for disposal, which nowadays is not possible, as limited spaces are available in the cities. So, here comes the need to find new techniques such as Home Composting. The research focuses on understanding the effectiveness of household composting as a waste management technique for household garbage. Household composting is an attractive method in which small bins can be used as an alternative to composting sites to a small scale. This technique helps to decompose the organic matter in lesser time than the traditional methods. Addition of compost accelerators in the bins increases the decomposition rate. Simply by home composting, the quantity of waste can be reduced. Key Words: Solid Waste Management, Composting, Compost Accelerators, Home Composting, Household Garbage

Obtainment and Inoculation of Acinetobacter pittii Strain JJ-2, and Combined Action with Plants for Formaldehyde and CO2 Removal: A Research Study.

A formaldehyde-degrading bacterium JJ-2 was isolated from the rhizosphere of Chlorophytum and identified as Acinetobacter pittii by colony morphology and 16S rDNA sequence analysis. Further studies showed that under optimal conditions, JJ-2 could maintain activity for six cycles at an initial formaldehyde concentration of 450mgL-1. At the same time, the complete degradation time was shortened from 12 to 6h. When the JJ-2 strain was inoculated into sterile soil, the surface spray method had the best effect, and the removal efficiency of 5ppm formaldehyde increased by 22.63%. In an actual potted plants system colonized with strain JJ-2, the first and second fumigations (without re-inoculation) increased removal by 1.36 times and 0.92 times during the day and 1.27 times and 2.07 times at night. In addition, in the second fumigation, the plant-bacteria combined system was 693.63ppm and the plant system was 715.34ppm, effectively reducing the CO2 concentration. This study provides an economical, ecological, and efficient approach to improve the combined system of plants and bacteria to remove gaseous formaldehyde from indoor air, with a positive impact on carbon neutrality.

Preparation and Degradation Performance Study of P(AM/GG/PEGDA) Nanocomposite Self-Degradation Gel Plugging Material.

Lost circulation is a world-class problem, and the contradiction between plugging and unplugging in reservoirs is a problem that needs to be solved urgently. The traditional LCM is not suitable for reservoirs and the complex subsequent operations. Currently, a self-degrading plugging material is proposed. In this paper, a new self-degradation plugging material, CKS-DPPG, was prepared by AM, GG, nano silica, and PEGDA. The effects of reactant concentration, pH, mineralization, etc., on the swelling and degradation performance of CKS-DPPG were investigated. The plugging capacity was tested by fracture plugging equipment, and the mechanism of self-degradation was revealed. The results show that the CKS-DPPG reached a 50% degradation rate in 54 h and complete degradation in 106 h at 80 °C and pH = 8. Low temperatures, high mineralization, and weak alkaline conditions prolong the complete degradation time of CKS-DPPG, which facilitates subsequent operations. The simulation of the 3 mm opening fracture plugging experiment showed that the pressure-bearing capacity reached 6.85 MPa and that a 0.16 MPa pressure difference could unplug after degradation. The ester bond of PEGDA is hydrolyzed under high-temperature conditions, and the spatial three-dimensional structure of CKS-DPPG becomes linear. The CKS-DPPG can effectively reduce subsequent unplugging operations and lower production costs.

Effect of Crosslinker Types on Temporary Plugging Performance of Degradable Preformed Particle Gels for Unconventional Petroleum Reservoir Development

Temporary plugging agents (TPAs) have been widely used in unconventional petroleum reservoirs to increase the stimulated reservoir volume and generate an easier flow of oil and gas into the production well. The properties of particle-gel-based TPAs include a straightforward injection procedure, excellent deformation, strong plugging strength, and total self-degradation. This study prepared degradable preformed particle gel (DPPG) samples polymerized by two types of crosslinkers (i.e., alcohol ester and alkenoic acid ester) for low-temperature (less than 40 °C) reservoirs. The effects of different crosslinkers in the DPPG compositions on the temporary plugging performance were investigated. Infrared spectrum analysis, differential calorimetry scanning evaluation, static particle gel swelling and degradation performance assessment experiments, and dynamic temporary plugging performance tests were all employed. The results showed that the swelling ratio of DPPGs prepared by the crosslinker containing alcohol ester was larger than that of alkenoate acid ester, but the degradation rate was slower. Among them, when the amount of crosslinker was 0.01 g, the swelling ratio of DPPG prepared using the alcohol ester crosslinker was as high as 40 times, and the complete degradation time could be regulated between 80 and 360 h. When the type of crosslinker was the same, the influence of its molecular weight also significantly affected the performance of the particle gel. The plugging strength of DPPG prepared by different crosslinkers in cores was as high as 20 MPa. The DPPG prepared from the alcohol ester crosslinker caused less damage to the core after being self-degraded and was used as an ideal crosslinker. Infrared spectroscopy and differential scanning calorimetry analysis at the molecular level verified that different types of crosslinkers had apparent effects on the chemical structure stability of the DPPG. In this paper, the influence of the type of crosslinker on the performance of the DPPG was studied, which provides a new idea and theoretical basis for developing a particle gel-based TPA system with programmed self-degradation time at low temperatures.

Degradable preformed particle gel as temporary plugging agent for low-temperature unconventional petroleum reservoirs: Effect of molecular weight of the cross-linking agent

The development of unconventional petroleum resources has gradually become an important succession for increasing oil production. However, the efficient development of this type of reservoir is paying more and more attention to the application of temporary plugging agents. The use of temporary plugging agents can further expand the stimulated reservoir volume (SRV) and facilitate the flow of oil and gas to the bottom of the well. Particle-gels used as temporary plugging agents have the characteristics of the simple injection process, good deformation, high plugging strength, and complete self-degradation performance, which has been widely applied in recent years. In this paper, five samples of DPPG polymerized by different molecular weights of cross-linking agents were prepared. In addition, infrared spectroscopy analysis, differential calorimetry scanning (DSC) analysis, static particle gel swelling and degradation performance evaluation experiments, and dynamic temporary plugging performance experiments in cores were used to study the influence mechanism of the cross-linking agent molecular weight ( M w ) of the DPPG molecule on its temporary plugging performance. Results show that as the molecular weight of the cross-linking agent (at 0.01 g) in the DPPG molecule decreases from 1000 to 200 Daltons, the fewer cross-linking sites of DPPG, the looser the microscopic three-dimensional mesh structure formed, and the swelling ratio is increased from seven to 33 times. However, the complete degradation time increases from 40 to 210 min. Moreover, the DSC scanning results confirmed that the larger the molecular weight of the cross-linking agent, the worse it is chemical stability and the more prone it to self-degradation. The DPPG particle samples have good temporary plugging performance in reservoir cores. The DPPG prepared by the cross-linking agent with smaller molecular weight has a smaller expansion ratio, higher gel strength, and greater plugging strength in the core. Moreover, the degraded DPPG is less damaging to the cores. However, its slower degradation rate takes a slightly longer time to reach complete degradation. The results of this paper can provide new ideas and a theoretical basis for the development of particle gel-based temporary plugging agents (TPA) with controllable degradation time in low-temperature reservoirs. It can help to expand further the application range of existing DPPG reservoir conditions.

Multifunctional SERS chip mediated by black phosphorus@gold-silver nanocomposites inserted in bilayer membrane for in-situ detection and degradation of hazardous materials

Self-cleaning surface-enhanced Raman scattering (SERS) substrates dependent on versatile two-dimensional semiconductors offer an efficient channel for the sensitive monitoring and timely degradation of hazardous molecules. Herein, a kind of sophisticated SERS-active nanocomposites was developed by incorporating Au-Ag nanoparticles onto black phosphorus (BP) nanosheets via photo-induced self-reduction. Combining the substantial electromagnetic “hot spots” triggered by bimetallic plasma coupling effect and the efficient charge transfer from BP to probe molecules, the proposed nanocomposites featured attractive SERS enhancement, facilitating a limit of detection down to 4.5 × 10−10 M. Attributed to the remarkable restriction of electron-hole recombination stemming from “Schottky contact”, the photocatalytic activity of BP was prominently boosted, demonstrating a complete degradation time as short as 65 min. Furthermore, the disgusting instability of BP was considerably hindered by inserting the nanocomposites into various bilayer matrices with diverse hardness and viscosity inspired by cling film principle. Moreover, a significantly elevated collection rate high to 93.1% for in-situ detection was also achieved by the as-manufactured flexible SERS chips based on tape. This study illustrates a clear perspective for the development of versatile BP-based SERS chips which might facilitate sensitive analysis and treatment of perilous contaminants in complicated real-life scenarios.

Degradation of internal fixation materials based on antibacterial and absorbable silk containing different gentamicin concentrations.

Adding gentamicin to silk fibroin enhances both the antibacterial performance and degradation rate of silk-based materials. The increased material degradation rate can affect the strength of early internal fixation, resulting in internal fixation failure. This study sought to adjust the gentamicin concentration to control the material degradation rate, thereby better meeting clinical application requirements. The in vitro degradation, water absorption rate, and expansion rate of silk-based materials containing different gentamicin concentrations were studied. A gentamicin-loaded silk-based screw was implanted into the femurs of New Zealand rabbits. Micro-computed tomography was used to measure the screw diameter, which was then used to calculate the degradation rate. The specimens were stained with hematoxylin and eosin and Masson's trichrome. The in vitro results revealed increasing material degradation rates with increasing gentamicin concentration but no significant differences in water absorption rates with different gentamicin concentrations. The degradation rates of gentamicin-loaded (4mg/g) silk-based rod-like materials were approximately 11.08% at three months in vitro and 9.4% in the animal experiment. The time for complete degradation was predicted from the fitting curve to be approximately 16months. No inflammatory hyperplasia was observed in bone or soft tissue. The degradation and biocompatibility of the material containing 4mg/g gentamicin meet clinical application requirements, and previous experimental results demonstrate good antibacterial performance of materials containing this gentamicin concentration.

Facile Synthesis of Rapidly Degrading PEG-Based Thiol-Norbornene Hydrogels.

An alternate synthesis route was developed to prepare norbornene-functionalized poly(ethylene glycol) (PEG) from reacting multiarm PEG with carbic anhydride. The macromer, PEGNBCA, permits photo-cross-linking of thiol-norbornene hydrogels with kinetics comparable to conventional PEGNB macromer. In addition, PEGNBCA provides an additional carboxylate group for further conjugation with amine-bearing molecules. Interestingly, PEGNBCA thiol-norbornene hydrogels are highly susceptible to hydrolytic degradation through enhanced ester hydrolysis. The ester linkage is further weakened after the secondary conjugation, resulting in extremely rapid degradation of PEGNB hydrogels. More importantly, the degradation can be readily adjusted via tuning macromer compositions, with complete degradation time ranging from hours to weeks. The PEGNBCA hydrogels are also highly cytocompatible toward various cell types, providing opportunities for future applications in tissue engineering and advanced biofabrication.

The degradation of Alternaria mycotoxins by dielectric barrier discharge cold plasma

In the present study, dielectric barrier discharge cold plasma was explored to treat alternariol (AOH) and alternariol monomethyl ether (AME) and the effect of mycotoxin states and plasma conditions on degradation were evaluated. The results showed that in either a solid state or aqueous solution, 100% AOH and AME were degraded within 180 s and 300 s, respectively. With the increase of voltage, both of AOH and AME degradation increased and reached nearly 100% at 30 kV and 40 kV, respectively. The degradation percentage of two mycotoxins was the highest (100%) in alkaline condition, but lower in neutral and acidic environment. In the presence of catalysts FeSO4 or H2O2, the time for complete degradation of both toxins was shortened. In conclusion, both mycotoxins could be effectively degraded by cold plasma and AOH was easier to be degraded than AME. Besides, the degradation of both toxins could be promoted by higher voltage, alkaline environment and catalysts FeSO4 and H2O2. The results of this study provide a theoretical basis for the removal of Alternaria mycotoxins from food systems and are useful for the investigation of the mechanisms involved in mycotoxin degradation by cold plasma.

Highly Efficient Solar‐Catalytic Degradation of Reactive Black 5 Dye Using Mesoporous Plasmonic Ag/g‐C3N4 Nanocomposites

AbstractAn azo dye, Reactive Black 5 (RB5), was degraded by three photocatalysts of g‐C3N4, Ag(2 %)/g‐C3N4, and Ag(5 %)/g‐C3N4 with the specific surface areas of 34.41, 28.70, and 35.58 m2 g−1 and the band gaps of 2.52, 1.56, and 1.71 eV under sunlight illumination, respectively. The results showed 40 mg/L of g‐C3N4 could degrade completely 10 ppm RB5 at pH 3.4 within 10 min under sunlight irradiation with the first‐order rate constant of 0.312 min−1. Under the same conditions, the complete degradation time of RB5 reduced to 5 and 7 min when the plasmonic nanocomposites of Ag (2 %)/g‐C3N4 and Ag (5 %)/g‐C3N4 were used as photocatalysts, respectively. Ag content had an important influence on the photocatalytic activity of g‐C3N4 against RB5 so that Ag (2 %)/g‐C3N4 possessed the best photocatalytic efficiency with the rate constant of 0.795 min−1. In fact, Ag nanoparticles through the surface plasmon resonance effects and by accepting the photogenerated electrons could improve the visible‐light absorption and increase charge separation of g‐C3N4. The results showed superoxide radical is the main oxidant in the photodegradation of RB5.

Rapid Degradation of Poly(lactic acid) with Organometallic Catalysts.

Poly(lactic acid) (PLA) is an effective sacrificial material for the creation of vascular networks in thermoset polymers and composites. The high thermal stability of PLA limits its applications as an embedded sacrificial template in high-temperature-resistant thermoset matrices. Here, we demonstrate faster and more efficient PLA degradation at temperatures lower than previously reported using two organometallic catalysts: tin(II) oxalate (Sn(Oxa)) and tin(II) acetate (Sn(Ac)2). We process Sn(Oxa) by two separate methods to obtain a significant difference in the specific surface area (SSA) of the catalyst particles and compare PLA degradation performance in a thermogravimetric analysis (TGA) instrument. Changing the SSA of Sn(Oxa) by a factor of ∼20 reduces the PLA degradation onset temperature by 37 °C. The total degradation time of PLA films also decreases after blending with Sn(Oxa) having a higher SSA. We also find Sn(Ac)2 lowers the degradation onset of PLA by 53 °C compared to Sn(Oxa) with a similar SSA. In addition, Sn(Ac)2 decreases the time for complete degradation of PLA films by an order of magnitude compared to Sn(Oxa) at 200 °C. Films with a significantly lower Sn(Ac)2 concentration compared to Sn(Oxa) degrade much faster at lower temperatures up to 160 °C. Finally, PLA films with different loadings of Sn(Ac)2 are embedded in an epoxy thermoset matrix and subsequently vascularized at elevated temperatures in a vacuum oven. Microchannel formation is observed at 170 °C using Sn(Ac)2, reducing the temperature required for vaporization of embedded sacrificial polymer compared to Sn(Oxa) catalyst. Sn(Ac)2 can potentially reduce the energy, time, and amount of catalyst required for degrading PLA into volatile products for sacrificial applications.

Effects of coupling hybrid processes on the treatment of wastewater containing a commercial mixture of diuron and hexazinone herbicides

This work evaluates the effects of coupling Conductive Diamond Electrochemical Oxidation (CDEO) with electrogenerated peroxide (CDEO-H2O2), iron (II) catalyst (electro-Fenton, EF) and UV irradiation (photoelectron-Fenton, PEF) techniques for the treatment of wastewater containing a commercial mixture of Diuron and Hexazinone herbicides. Although the techniques employed in this study exhibited significant differences in terms of current charge, energy consumption and amounts of byproducts formed, they have shown to be capable of degrading and mineralizing both herbicides (Diuron and Hexazinone). The application of electrooxidation technique with and without hydrogen peroxide generation led to the oxidation of both herbicides, where removal rates ranging from 74% to 99% and 77%–92% were obtained for Hexazinone and Diuron, respectively. Hexazinone and Diuron were completely removed after 90 min in the EF process. PEF was found to be the most efficient technique for having drastically reduced the time for complete degradation of the herbicides, although 25% of organic carbon remained in solution after 120 min of electrolysis. Higher rates of herbicides degradation were obtained in this order: PEF > EF > CDEO/H2O2/UV > CDEO/H2O2 > CDEO > UV. The result indicates that the production of oxidants is promoted by the hybrid processes, and this leads to an improvement in the oxidation of the pollutants. The synergistic coefficient obtained for the coupled techniques were higher than one in terms of both herbicides degradation and Total Organic Carbon (TOC) removal. Two important sub-products of reaction were identified, and their degradation route is in agreement with the reports published in the literature. Essentially, this work draws attention to the synergistic effect caused by the coupling of techniques involving the treatment of chemical agents in wastewater and sheds light on how to use this coupling technique for the development of more efficient treatment processes.

Microbial degradation of BTEX compounds in groundwater after ozonation process

BTEX (benzene, toluene, ethylbenzene, and xylene) compounds are common in a variety of water resources, including groundwater. However, the ongoing biodegradation processes are not sufficiently effective, and accumulation of these substances occurs. To enhance the biodegradability, ozonation can be used for transformation of these recalcitrant compounds to easily biodegradable organics. This paper is focused on expanding existing knowledge of degrading BTEX substances by ozonation process before biological degradation. Batch experiments were prepared from aquifer sediment with ozonated and non-ozonated groundwater contaminated by 10 mg dm−3 BTEX. The results showed that degradation efficiency of these compounds without previous ozonation was in the first 7 days 9.1% for benzene, 68.4% for toluene, 74.9% for p-xylene, and 89.4% for ethylbenzene. In this process, the complete degradation time for these substances was up to 7 days for ethylbenzene, and 14 days for toluene and p-xylene. Benzene was not degraded even after 21 days of the experiment. In comparison, the ozonation process increased the biological degradation efficiency when all these compounds were completely degraded within 7 days of the experiment. The total number of attached cells was on average 1.2 orders of magnitude higher than in the case of the non-ozonated BTEX samples.

Degradation of Nystatin in aqueous medium by coupling UV-C irradiation, H2O2 photolysis, and photo-Fenton processes.

Oxidative degradation and mineralization of the antifungal drug Nystatin (NYS) was investigated using photochemical advanced oxidation processes UV-C irradiation (280-100nm), H2O2 photolysis (UV/H2O2), and photo-Fenton (UV/H2O2/Fe3+). The effect of operating parameters such as [H2O2], [Fe3+], and [NYS] initial concentrations on degradation efficiency and mineralization ability of different processes was comparatively examined in order to optimize the processes. Photo-Fenton was found to be the most efficient process attaining complete degradation of 0.02mM (19.2mgL-1) NYS at 2min and a quasi-complete mineralization (97%) of its solution at 5h treatment while UV/H2O2 and UV-C systems require significantly more time for complete degradation and lower mineralization degrees. The degradation and mineralization kinetics were affected by H2O2 and Fe3+ initial concentration, the optimum dosages being 4mM and 0.4mM, respectively. Consumption of H2O2 during photo-Fenton treatment is very fast during the first 30min leading to the appearance of two stages in the mineralization. The evolution of toxicity of treated solutions was assessed and confirmed the effectiveness of photo-Fenton process for the detoxification of NYS solution at the end of treatment. Application to real wastewater from pharmaceutical industry containing the target molecule NYS showed the effectiveness of photo-Fenton process since it achieved 92% TOC removal rate at 6-h treatment time.

Promoting the Photo-Fenton catalytic activity with carbon dots: Broadening light absorption, higher applicable pH and better reuse performance

A new visible and near-infrared light-responsive heterogeneous Photo-Fenton catalyst, Fe3O4@Cu2O/carbon quantum dots (CQDs)/nitrogen-doped carbon quantum dots (N-CQDs) (FCCN) was prepared under mild conditions with the structure of double quantum dots growing on the surface of Fe3O4@Cu2O nanoparticles. The prepared FCCN could be used for the degradation of azo compounds, such as methyl orange, acid orange II and mordant yellow 10, even at neutral and alkaline pH (pH: 7–12) with a shortest complete degradation time of 15 min. During the Photo-Fenton process, CQDs and N-CQDs acting as up-converting photo-sensitizers improved the utilization of the light, in which the contribution of N-CQDs was greater than that of CQDs. Besides, CQDs and N-CQDs could transfer photo-generated charges between Cu2O and Fe3O4 for the rapid decomposition of H2O2 to OH. CQDs as solid light-sensitive acid sites could consume OH− and enable the efficient decomposition of H2O2 under alkaline conditions. The magnetism of Fe3O4 made this catalyst easily separated and the insoluble layers of CQDs and N-CQDs allowed it to be repeatedly used without activity change even after 10 cycles. The degradation constant of methyl orange in FCCN/H2O2/light system is 5.4 times higher than that of the Fe3O4@Cu2O/H2O2/light system, indicating that the loaded quantum dots greatly enhanced the photocatalytic activity. The degradation constant in FCCN/H2O2/light system was 2.5 times higher than that of the simple mixture (Fe3O4@Cu2O + CQDs + N-CQDs)/H2O2/light system, which indicated these excellent catalytic performances should come from the synergism effect of all components in FCCN.

Activation of peroxymonosulfate by magnetic carbon supported Prussian blue nanocomposite for the degradation of organic contaminants with singlet oxygen and superoxide radicals

In order to develop efficient and green catalyst for organic pollutants removal, magnetic carbon supported Prussian blue nanocomposite Fe3O4@C/PB was prepared for the first time. The performance of Fe3O4@C/PB in activating peroxymonosulfate (PMS) for the degradation of 2,4-dichlorophenol (2,4-DCP) was investigated. 2,4-DCP could be effectively degraded under the “Fe3O4@C/PB + PMS” system within a broad pH range of 2–9. Without pH adjustment (pH 3), 2,4-DCP (20 mg/L) was completely degraded in 50 min along with a 70% removal of TOC; while the required time for complete degradation of 2,4-DCP was shortened to 40 min under initial solution pH at 7. Fe3O4@C/PB could also activate PMS for the degradation of phenol, Acid Orange II, Reactive brilliant red X-3B, Rhodamine B and Methylene blue. The degradation rates higher than 95% could be achieved for all these contaminants within the time scale of 15–60 min. The studies of radical-quenching and electron paramagnetic resonance demonstrated that singlet oxygen (1O2) and superoxide radicals (O2−), rather than sulfate (SO4−) and hydroxyl (OH) radicals, were the dominant species responsible for the oxidation of organic pollutants. The plausible mechanism of the catalytic degradation was proposed and the enhanced activity of Fe3O4@C/PB was assumed to be related to the increased electron transfer owing to the synergic effect between the magnetic carbon and the mixed-valence units in PB. Fe3O4@C/PB is promising in wastewater treatment owing to its high efficiency, excellent stability and reusability, environmental friendliness and magnetic separability.

Bioconversion of chicken feathers by Bacillus aerius NSMk2: A potential approach in poultry waste management

About 73 bacterial strains were isolated from poultry dump sites in Punjab and an isolate showing high keratinolytic activity was identified as Bacillus aerius NSMk2. Strain showed prompt hydrolysis of white chicken feathers on minimal salt medium (MSM) after 5 days of cultivation. Melanized chicken, pigeon and duck feathers could also be degraded by bacteria with high activity to duck and pigeon feathers. MSM supplemented with fructose and beef extract supported higher feather keratinase production and improved degradation of white chicken feathers. Feather concentration 1.375%, pH 7.5 and temperature 35 °C showed maximum feather keratinase activity (127.63 U/ml) after 2 days which was 7-fold higher than activity on minimal salt medium. Time for complete degradation of white chicken feathers was reduced to 3 days on optimized medium. The results of present investigation showing potential keratinolytic ability of Bacillus aerius NSMk2 could provide an environmental friendly approach for bioconversion of poultry waste.

Immobilization of laccase on the fibrous polymer-grafted film and study of textile dye degradation by MALDI–ToF-MS

This study assessed the immobilization of laccase on fibrous polymer-grafted polypropylene chloride film and the removal of three different dyes (i.e., Procion Green H4G, Brilliant Blue G, and Crystal Violet) using immobilized laccase. The polypropylene chloride (PP) film and poly(glycidylmethacrylate)-grafted (PP-g-pGMA) film were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and contact angle studies. The PP-g-pGMA film was used for the direct immobilization of laccase. The amount of immobilized enzyme and the enzyme activity on the film were found to be 1.185μg/cm2 and 1.71×10−2U/cm2 film, respectively. The retained activity of the immobilized laccase was 72.3%. The optimal conditions for the free and immobilized enzymes and the kinetic parameters were determined. Additionally, the thermal, storage, and operational stabilities of the immobilized laccase were increased compared with those of the free form. Kinetic parameters Vmax and Km values were determined as 23.4U/mg protein and 0.38mmol/L for free enzyme and 17.5U/mg protein and 0.53mmol/L for the immobilized laccase, respectively. The removal of the tested dyes with the immobilized laccases was evaluated in batch system and enzyme reactor. The maximum enzymatic removal of tested dyes was achieved at a pH of 5.5 and a temperature of 30°C. The complete degradation time of the tested dyes was determined by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI–ToF-MS). These results indicate that the immobilized laccase system can be effectively used for the removal of dyes, and it has a great potential for various biotechnological applications.