Total Organic Carbon Analysis Research Articles

A portable and smartphone-based plasmonic system for on-site measurement of airborne redox-active compounds by light-initiated redox reaction

The determination of airborne redox-active compounds (ARC) is essential for monitoring adverse environmental changes and understanding the potential impact on human health. With the exception of relying on the common total organic carbon (TOC) analyzer and dithiothreitol (DTT) assay, there is currently no easy-to-use method for quantitative assessment. Herein, a compatible and easy-to-use colorimetric sensing strategy was developed for on-site ARC quantification. This approach integrated a plasmonic sensing system, where the ARC-induced gold nanoparticles (AuNPs) reduction, localized surface plasmon resonance (LSPR), and the light-mediated photochemistry collaborated to achieve a limit of detection (LOD) at 0.05 μg∙mm−2 on the filters. Distinguished from the abovementioned methods, the ARC content can be directly determined by in-situ monitoring the colorimetric reaction on the sampling quartz filters (QF) without additional sample pre-treatment. Apart from utilizing the standard benchtop photodetector (e.g., UV–VIS spectrophotometer), the colorimetric images of AuNP@QF samples could also be imaged by a smartphone camera in a sealed box and analyzed through a smartphone-based application to read the RGB (Red, Green, Blue) values for ARC quantification. The good correlation between the results using the spectrophotometer and smartphone validate the applicability of the AuNP sensor. The smartphone-based method was then deployed to test real-world aerosols collected from Zurich, Bern and Rigi and the results of ARC exhibited a positive correlation with that of PM10. With the advantages of low-cost, easy-operation and no need for pre-treatment, this smartphone-based plasmonic system holds great potential for rapid and portable ARC detection and corresponding air quality assessment.

Experimental and numerical study on diazinon removal using plasma bubble column reactor: Modeling, kinetics, mechanisms, and degradation products

Diazinone is the most commonly used pesticide worldwide. In this study, experimental and numerical analyses were employed to model and optimize the degradation and mineralization of diazinon using remotely generated non-thermal atmospheric pressure plasma. The initial concentration of diazinon, pH of the medium, and flow rate of the plasma feeding gas were considered as the salient factors in the modeling and optimization processes. To our knowledge, this study is the first report on the effects of gas composition and flow rate on the type and concentration of remotely generated reactive nitrogen and oxygen species (RNOS). An air gas composition was adopted as the feeding gas for a custom-made dielectric barrier discharge (DBD) plasma generator. Remotely generated gas plasma was introduced into the reactor through a diffuser located at the bottom of the column reactor, and the degradation of diazinon and its derived products was monitored using GC-MS. The decrease in the total organic carbon (TOC) content of the samples due to plasma treatment was traced using a TOC analyzer. Although 83.11% degradation was observed, the maximum TOC removal using this method was only 39.22%. Subsequently, response surface methodology (RSM) was employed to mathematically model the process and observe the correlations between different parameters. Our results suggested a quadratic model for the degradation and TOC removal of the given treatment methods, which further indicated that the initial concentration of the analyte and pH influenced the degradation efficiency. However, the gas flow rate was identified as an important factor in TOC removal. The energy yield of the treatment procedure was 46.2 (gTOCkW−1h−1), suggesting the potential of DBD plasma for the treatment of diazinon-polluted water.

Characterization and Control of Pore Structural Heterogeneity for Low-Thermal-Maturity Shale: A Case Study of the Shanxi Formation in the Northeast Zhoukou Depression, Southern North China Basin

The Shanxi Formation layers in the northeast of the Zhoukou Depression, Southern North China Basin, mainly consist of dark mudstone interbed with tight stone and widely developed coal seam, which is a promising target for unconventional oil and gas exploration. A series of geochemical and geological methods were used to analyze the characterization and controls of the pores structural heterogeneity in low-thermal-maturity shale. These methods include the Rock-Eval analysis, total organic carbon (TOC) analysis, scanning electron microscope observation with an energy-dispersive spectrometer (SEM-EDS), X-ray diffraction, and low-pressure N2 adsorption. Based on these measurements, the pore diameter, specific surface area (SSA), and fractal dimension (D) were calculated, and then, the pore structure heterogeneity was analyzed. The result shows the pores of Shanxi Formation shale are mainly interparticle pores with low porosity and low permeability, and the pore structure is highly complex. The average fractal dimension of the micropore and the macropore are both 2.77, but that of the mesopore is 2.65, indicating a less-complex mesopore structure than the micropore and macropore. The S2, S1, and TOC exhibit no clear correlation with SSA and fractal dimension of pores, which proved the little impact of organic matter on the heterogeneity of pore structure in the low-maturity shale of the research area. The illite has a strong effect on the pore structural heterogeneity of Shanxi Formation shale. The samples with high content of illite show higher SSA, better physical properties, and low fractal dimension, reflecting low pore structural heterogeneity. However, the quartz and clay minerals show a slight correlation with SSA and no obvious relationship with the fractal dimension, indicating a little effect of them on the pore structure heterogeneity. The pore structural heterogeneity decreases along with the increase in porosity, while the permeability influenced by a variety of reasons under the compaction shows a poor relationship with SSA and fractal dimension. On the whole, the pore structural heterogeneity decreases for low-thermal-maturity shale with high content of illite and high porosity, which should be considered to be the better unconventional oil and gas reservoir in the research area.

(Digital Presentation) Realistic Molecular Dynamics Modeling of ssDNA/SWCNT Hybrids

Despite the importance of single-wall carbon nanotubes (SWCNTs) coated with short oligos of single-stranded DNA (ssDNA), the structure-specific interactions in these hybrids remain poorly understood. It is known that the interactions can depend on the DNA base sequence and length, and on the nanotube diameter and roll-up angle. To study these phenomena, we are applying a combination of computational and experimental methods. A major goal for guiding and validating molecular dynamics simulations of the hybrid structures is finding the average length of nanotube covered by each ssDNA oligo. We have quantified this by carefully preparing dialyzed aqueous dispersions of SWCNTs in specific oligos and then measuring the absolute mass concentrations of both components using total organic carbon analysis. Corresponding absorption spectra were also measured to deduce ultraviolet SWCNT molar absorptivities (structurally averaged), which in combination with known ssDNA nucleobase absorptivities allow quicker determinations of mass ratios in the hybrids. Our results for a library of hybrids indicate that purine nucleobases on average cover a larger region on the nanotube surface than do pyrimidine nucleobases, as is consistent with the sizes of those aromatic structures. This average coverage is key to developing realistic atomistic molecular dynamics models for the conformations of ssDNA adsorbed on SWCNT sidewalls. Examples of such computed hybrid structures and their significance will be presented.

Pore Structure in Shale Tested by Low Pressure N2 Adsorption Experiments: Mechanism, Geological Control and Application

The N2 adsorption experiment is one of the most important methods for characterizing the pore structure of shale, as it covers the major pore size range present in such sediments. The goal of this work is to better understand both the mechanisms and application of low-pressure nitrogen adsorption experiments in pore structure characterization. To achieve this, the N2 adsorption molecular simulation method, low-pressure N2 adsorption experiments, total organic carbon (TOC) analysis, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and a total of 196 shale samples from the Wufeng–Longmaxi formations in the Sichuan basin have been employed in this study. Based on the analytical data and the simulations, two parameters, the connectivity index and the large pore volume index, are proposed. These parameters are defined as the connectivity of the pore system and the volume of large nanopores (>10 nm) respectively, and they are calculated based on the N2 adsorption and desorption isotherms. The experimental results showed that TOC content and clay minerals are the key factors controlling surface area and pore volume. However, in different shale wells and different substrata (divided based on graptolite zonation), the relative influences of TOC content and clay minerals on pore structure differ. In three of the six wells, TOC content is the key factor controlling surface area and pore volume. In contrast, clay minerals in samples from the W202 well are the key factors controlling pore volume, and with an increase in the clay mineral content, the pore volume increases linearly. When the carbonate content exceeds 50%, the pore volume decreases with an increase in carbonate content, and this may be because in the diagenetic process, carbonate cement fills the pores. It is also found that with increasing TOC content the connectivity index increases and SEM images also illustrate that organic pores have better connectivity. Furthermore, the connectivity index increases as quartz content increases. The large pore volume index increases with quartz content from 0 to 40% and decreases as quartz increases from 40% to 100%. By comparing the pore structure of shale in the same substrata of different shale gas wells, it was found that tectonic location significantly affects the surface area and pore volume of shale samples. The shale samples from wells that are located in broad tectonic zones, far from large-scale faults and overpressure zones, have larger pore volumes and surface areas. On the contrary, the shale samples from shale gas wells that are located in the anticline region with strong tectonic extrusion zones or near large-scale faults have relatively low pore volumes and surface areas. By employing large numbers of shale samples and analyzing N2 adsorption mechanism in shale, this study has expanded the application of N2 adsorption experiment in shale and clarifies the effects of sedimentary factors and tectonic factors on pore structure.

Hydrothermal construction of flower-like g-C3N4/NiZnAl-LDH S-scheme heterojunction with oxygen vacancies for enhanced visible-light triggered photocatalytic performance

Construction of S-scheme heterojunction with high photocatalytic performance has been regarded as a promising way to treat organic wastewater thoroughly. In the present work, a novel S-scheme heterojunction with oxygen vacancies was successfully constructed between graphitic-carbon nitride(g-C3N4) nanosheets and NiZnAl layered double hydroxide (NiZnAl-LDH) by hydrothermal method. The as-synthesized g-C3N4/NiZnAl-LDH heterojunction displayed superior photocatalytic degradation activity over methyl orange (MO) and tetracycline (TC) aqueous solution compared with the pristine g-C3N4 and NiZnAl-LDH. Dramatically, the sample g-C3N4/NiZnAl-LDH (23%) exhibited the best photocatalytic activity, the photodegradation rate constants are 3.5, 12.7 times and 3.2, 5.5 times to pristine g-C3N4 and NiZnAl-LDH, respectively for the degradation of MO and TC. The enhanced photocatalytic activity is mainly due to the formation of S-scheme heterojunction modified by oxygen vacancy. In addition, a reasonable photocatalytic mechanism was proposed based on the photoluminescence (PL), electrochemical impedance (EIS), transient photocurrent test, active species capture and electron spin response (ESR/EPR) experiments combined with high performance liquid chromatography-mass spectrometry (HPLC-MAS) and total organic carbon (TOC) analysis. This work affords a new approach for the construction of efficient, stable and potential applications of g-C3N4 based S-scheme heterojunction photocatalysts.

Comparative Studies of Photochemical and Electrochemical Methods on Mineralization of Picric Acid

The effluents generated from synthesis and processing plant of Picric acid is reported to be carcinogenic and hence needs to be treated to reduce its concentration below safe discharge limit. Present paper deals with studies on mineralization of Picric acid by adopting photochemical and electrochemical processes and the efficacy of the both processes have been explored in details. Crucial process parameters viz. pH, concentration of oxidizer and catalyst for mineralization of Picric acid are optimized. In photochemical method, It is observed that Picric acid is treated to bring down its concentration from 100 ppm to ≤ 1 ppm under Photo-Fenton process in 2 hrs whereas same treatment carried out under Photo- catalytic process takes only 1 hr. It is also observed that TiO2 xerogel and beads of nano-TiO2 are more efficient compared to that of commercially available TiO2. The TiO2–Polysulfone (PS) beads show less efficiency than TiO2 xerogel. However, the Picric acid oxidation efficiency for TiO2–PS beads is comparable and advantage of TiO2–PS beads is that it can easily be recovered from the treated solution and can be reused in the next experiments. Electrochemical process is user’s friendly and economical. In case of electrochemical treatments at optimized process parameters under Electro-Fenton reaction picric acid is completely mineralized below its drain discharge limit where as under Electro-peroxide reaction picric acid is mineralized upto 3 ppm within 3 hrs. The treated solution has been characterized by using UV-Visible spectrophotometer, High performance Liquid Chromatography (HPLC) and Total Organic Carbon (TOC) Analyzer. The observed results have been interpreted and reported in the present paper.

Advanced Photocatalytic Treatment of Wastewater Using Immobilized Titanium Dioxide as a Photocatalyst in a Pilot-Scale Reactor: Process Intensification.

In many nations, particularly those experiencing water scarcity, novel approaches are being applied to clean wastewater. Heterogeneous photocatalysis is the most widely used of these approaches because it entails the decomposition of organic molecules into water and carbon dioxide, which is a more ecologically benign process. In our study, we studied the photocatalytic degradation process on the effluent flumequine. This treatment is made through a solar pilot reactor in the presence of immobilized titanium dioxide with three light intensities and two types of water as solvents. A variety of factors that might influence the rate of deterioration, such as flow rate, light intensity, and initial concentration, have been investigated. The maximal degradation of flumequine was achieved at more than 90% after 2.5 h under optimal conditions (an initial concentration of 5 mg/L, three lamp light intensities, and a flow rate of 29 L/h). By combining the oxidized agent H2O2 with this process, the photocatalytic activity was improved further to 97% under the same conditions. The mineralization of this product has also been tested using total organic carbon (TOC) analysis. A high mineralization rate has been recorded at around 50% for a high initial concentration (20 mg/L) at a flow rate of 126 L/h. The results demonstrated the highly effective removal of flumequine and the efficacy of this photocatalytic system.

Synthesis of sodium alginate-polycarboxylate superplasticizer and its tolerance mechanism on montmorillonite

Sodium montmorillonite (MMT) is a major mineral component of clay in manufactured sand which is an economical aggregate in concrete. Its lamellar structure has a negative effect on an important concrete admixtures polycarboxylate superplasticizer (PCE). In this study, sodium alginate (SA), a polysaccharide, was grafted with an unsaturated amide, having a double bond structure, to synthesize the acrylamide modified sodium alginate (Ugi-SA) through the Ugi reaction. Then, Ugi-SA, acrylic acid (AA), and isopentenol polyoxyethylene ether (TPEG) were used to synthesize sodium alginate-polycarboxylate superplasticizer (SPCE) by free radical copolymerization. The structures of Ugi-SA and SPCE were determined by gel permeation chromatography (GPC) and Fourier transform infrared (FT-IR). The fluidity of the montmorillonite (MMT) cement paste with SPCE and the traditional polycarboxylate superplasticizer (TPCE) was investigated. Furthermore, the adsorption behavior of SPCE on MMT was measured by X-ray diffraction (XRD), thermogravimetric analysis (TGA), total organic carbon analyzer (TOC) and the tolerance mechanism of SPCE on MMT was discussed. The FT-IR and GPC results showed that Ugi-SA and SPCE were synthesized successfully. The initial fluidity test results indicated that SPCE had a better dispersion effect and MMT tolerance than TPCE. TGA, TOC and XRD tests showed that the adsorption of SPCE on MMT was much lower than that of TPCE. This study demonstrated that the SA structure of SPCE appears to exhibit a large steric hindrance, which prevents the intercalation of SPCE into MMT.

Photodegradation under UV Light Irradiation of Various Types and Systems of Organic Pollutants in the Presence of a Performant BiPO4 Photocatalyst

In this study, we prepared spheroid microstructures of monoclinic bismuth phosphate BiPO4 by a facile solid-state reaction at 500 °C. The crystal structure was refined using the Rietveld method, where the crystal cell was resolved using a monoclinic system (parameters a, b, c, β) with space group P21/n. SEM images showed that the solid catalyst presented homogeneous morphologies. These BiPO4 microparticles (BiP-500) have been used as photocatalysts to photodegrade, under UV light irradiation, three cationic dyes (Rhodamine B, RhB; Methylene Blue, MB; and Toluidine Blue, TB), three anionic dyes (Congo Red, CR; Orange G, OG; and Methyl Orange, MO) and mixtures of RhB-MB, RhB-OG and MO-OG organic dyes. The photodegradation efficiency of these BiP-500 microparticles is found to be optimal in the case of RhB solutions, RhB-MB and RhB-OG binary mixtures. The BiP-500 catalyst shows a high selectivity for the conversion of the mixture of dyes into CO2 and H2O. Total organic carbon analysis of an anionic dye and a cationic dye (RhB, OG and RhB-MB) confirms the mineralization of the pollutants in the presence of BiP-500 particles. The photocatalytic efficiency of our BiP-500 photocatalyst has been confirmed, with a view to facilitate applications in the field of the depollution of wastewater in the agricultural environment by the degradation of parathion-methyl (PM) as a pollutant.

Hybrid machine learning models for estimating total organic carbon from mineral constituents in core samples of shale gas fields

The analysis of total organic carbon (TOC) contents is an important activity in exploring potentially hydrocarbon-generating intervals. Petroleum source rocks have, by definition, high TOC values due to the accumulation of organic matter in anoxic and low-energy deposition environments over geological time. Such petroleum generation is called conventional because it results from the increasing temperature and pressure conditions during continuous sedimentary burial. On the other hand, unconventional generation refers to reserves formed due to another heat source, for example, associated with intrusive igneous emplacement. In the last decade, there has been a growing economic interest in exploring unconventional hydrocarbon reserves because of the abundance of its occurrences. However, finding ways to assess the total organic carbon (TOC) content at lower cost and time-consuming laboratory experiments is becoming fundamental due to the importance of TOC in the analysis of the composition of these resources. This study predicts TOC using a hybrid approach, integrating machine learning models into a Grey Wolf Optimization Algorithm to adjust their parameters. The performance of four methods was compared: Elastic Net Linear Model, Extreme Learning Machine, Multivariate Adaptive Regression Splines, and Linear Support Vector Regression. The methodology was evaluated by applying core samples of the shale gas field YuDong-Nan belonging to the Sichuan Basin. The results show that the machine learning methods assisted by the evolutionary algorithm could accurately estimate TOC and be used to further exploratory geological analysis, especially those related to the prospects of unconventional oil-gas resources.

Degradation of amoxicillin applying photo-Fenton and acid hydrolysis processes with toxicity evaluation via antimicrobial susceptibility tests

ABSTARCT The antibiotic amoxicillin (AMX) is a semisynthetic aminopenicillin, classified as an β-lactam antibiotic. This work aims to evaluate the AMX degradation (190 mg L–1), in aqueous medium, applying photo-Fenton ([TOC]0 = 100 mgC L−1; FH2O2 = 3.27 mmol min−1; [Fe2+] = 0.27 mmol L−1; pH = 3.0; T = 40°C) and acid hydrolysis processes. Along the experiments, samples were withdrawn and analyzed by a total organic carbon (TOC) analyzer and a liquid chromatography system coupled to diode array (HPLC-DAD) and mass spectrometry (HPLC-MS) detectors. The hydrolysis process proved to be less efficient, because AMX removals greater than 80% were observed only after 24 hours of reaction (pH 2). Conversely, the photo-Fenton process removed completely AMX in just 20 minutes, reaching 85% of TOC removal in 2 hours. Finally, the AMX aqueous solutions treated by the studied processes was also evaluated in respect of its toxicity to some microorganisms, applying two antimicrobial susceptibility tests: disk-diffusion and broth microdilution methods. It was observed that the AMX aqueous solutions, pretreated by the photo-Fenton process, for just 7.5 min of reaction time, did not inhibit the microorganisms growth. The obtained results show that the photo-Fenton process was able to degrade AMX, in a relatively short time, and that the generated degradation products did not inhibit the microorganisms growth, when compared to acid hydrolysis process. Thus, it was verified the potential application of the photo-Fenton system as a pretreatment step to conventional biological oxidation processes for the treatment of industrial wastewaters.

The heterogeneity of lithofacies types, combination modes, and sedimentary model of lacustrine shale restricted by high‐frequency sequence

The second Member of the Funing Formation in the Haian Sag of the Subei Basin is a set of organic‐rich fine‐grained sedimentary rocks, which is a key interval for shale oil exploration. Under the premise of establishing a high‐frequency sequence framework, the fine description of the lithofacies change characteristics of the continental fine‐grained sedimentary rocks is the basis for the prediction of shale oil favourable areas and the optimization of the production horizons. This study is established through wavelet transformation of the natural gamma curve of the high‐frequency sequence framework of the second Member of the Funing Formation, using thin‐section observation, total organic carbon analysis, and X‐ray diffraction experiments to study the lithofacies types and characteristics of fine‐grained sedimentary rocks, and discuss the combination of lithofacies under the high‐frequency sequence framework Mode and influencing factors. The results show that the second Member of Funing Formation is composed of three‐level sequence of low‐level system tract (LST), transgressive system tract (TST), and early high‐level system tract (EHST), corresponding to 6 fourth‐level sequences and 10 fifth‐level sequences. According to the division scheme of “abundance of organic matter + mineral composition + sedimentary structure”, it is found that 12 types of lithofacies were developed in the fine‐grained sedimentary rocks of the second Member of Funing Formation. The lithofacies type is affected by the palaeoenvironment. The organic matter facies are mainly controlled by palaeo‐water depth and palaeo‐redox conditions, the components are mainly controlled by palaeo‐water depth and palaeo‐salinity, and the tectonic facies are mainly controlled by palaeo‐redox and palaeo‐salinity. The lithofacies are regularly superimposed in the high‐frequency sequence framework, and three combination modes of A, B, and C are developed. Among them, the type A lithofacies are developed in the low‐stand system tract, and the type B lithofacies are developed in the transgressive system. The C‐type lithofacies assemblage developed near the largest flooding surface and the early highstand system tract, and combined with palaeoenvironment analysis to establish a lithofacies sedimentary model.

Fabrication of high visible light active LaFeO3/Cl-g-C3N4/RGO heterojunction for solar assisted photo-degradation of aceclofenac

The designing of semiconductor based heterojunction has proved to be an effective strategy for developing more efficient photo-catalyst than single component photo-catalyst. Herein, we report the laboratory scale fabrication of a novel LaFeO3/Cl-g-C3N4/RGO (LCCR) heterojunction with enormous photocatalytic activity. The prepared nano-composite has been characterized using X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM). The LaFeO3/Cl-g-C3N4/RGO (LCCR) nano-heterojunction exhibits excellent photocatalytic activity due to its reduced charge recombination rate. The photocatalytic potential of LCCR was tested for the photo degradation of aceclofenac drug as model pollutant. LCCR with an optimum dosage amount 200 mgL−1 has shown highest degradation of 96.4 % within 90 min of solar light exposure. Various operational parameters such as effect of pH, photocatalyst dosage, pollutant concentration and various ions has been investigated. The photo-degradation outcomes of LCCR nano-composite have been examined in terms of reaction kinetics, active radical identification experiments, high resolution mass spectrometry (HR-MS), chemical oxygen demand (COD) and total organic carbon (TOC) analysis. The photo-degradation experiment followed the pseudo first order kinetics with high rate constant k1 = 0.0461 min−1 and results for TOC and COD analysis shows that 53.2 % of TOC was removed, whereas COD was decreased to 22.4 %. This work shows promising photo-catalyst for treating pharmaceutical effluents.

Molybdenum based nanoporous carbon silica matrix for the oxidation of volatile organic compounds present in the pharmaceutical industry wastewater

Volatile organic compounds (VOCs) are highly volatile in nature and cause significant air pollution in the environment. It is copiously present in evaporate condensate wastewater (ECWW) released by the pharmaceutical industry and can escape into the atmosphere during conventional aerobic wastewater treatment. This study describes the preparation of molybdenum impregnated nanoporous carbon silica matrix (MoNCSM) and its efficiency toward catalytic oxidation of VOCs present in ECWW. It also focuses on the oxidation of the non-VOCs present in ECWW after VOCs removal. The MoNCSM was characterised by Fourier transform infrared spectroscopy, which confirmed the sharp peaks in the region 800–600 cm−1 corresponding to the stretching vibrations of Mo-O-Mo. The X-ray diffraction spectrum of MoNCSM showed 2θ values of 26.38°, 57°, 31.2° for MoO2, and 40.06° for MoO3. The electron paramagnetic resonance spectrum showed the presence of free electrons in MoNCSM at a g-factor of 2.011. The ECWW possessed chemical oxygen demand (COD) of 210,000–240,000 mg L−1, in which 90–92% account for VOCs. The VOCs were separated from ECWW and catalytically oxidised using MoNCSM catalyst. It showed a removal efficiency of 84.8% ± 2.3 in terms of total organic carbon (TOC) in 20 treatment cycles. The remaining non-VOCs containing ECWW were treated by advanced oxidation processes using sequential packed-bed and fluidised bed reactors. Its overall removal efficiency was COD, 98.78%; biochemical oxygen demand, 98.54%; TOC, 99.46%; total Kjeldahl nitrogen, 78.2%, and NH4+-N, 95%, respectively. The catalytic oxidation of VOCs present in ECWW was confirmed using TOC analysis and high-performance liquid chromatography.

Degradation of tetracycline antibiotic utilizing light driven-activated oxone in the presence of g-C3N4/ZnFe LDH binary heterojunction nanocomposite

In the present study, a binary heterojunction nanocomposite composed of graphitic carbon nitride (g-C3N4) and Zn/Fe-contained layered double hydroxide (ZnFe LDH) was employed as heterogeneous catalyst for the decomposition of tetracycline (TC) antibiotic utilizing Oxone and UV light irradiation. The sole use of g-C3N4/ZnFe LDH as adsorbent led to the negligible elimination of TC. In addition, the sole use of Oxone or UV (photolysis) and even their combination were not effective enough to degrade the target pollutant, while the combined process of g-C3N4/ZnFe LDH/Oxone/photolysis revealed significantly enhanced (synergistic) degradation of TC (92.4% within 30 min). Indirect detection tests for the identification of free radical species indicated the major role of both hydroxyl (•OH) and sulfate (SO4•−) radicals in the degradation of TC by the g-C3N4/ZnFe LDH/Oxone/photolysis system. The elimination of TC followed a pseudo-first order kinetic model. The complete degradation of TC (degradation efficiency of 100%) was achieved within the reaction time of 25 min when ultrasound (US) was applied as enhancing agent. Furthermore, the results of total organic carbon (TOC) analysis were used to exhibit progress in the mineralization of the pollutant. The bioassay results indicated the decreased toxicity of the process effluent toward microbial population of Escherichia coli after the treatment.

Spontaneous Adsorption and Efficient Photodegradation of Indigo Carmine under Visible Light by Bismuth Oxyiodide Nanoparticles Fabricated Entirely at Room Temperature

Bismuth oxyiodide (BiOI) is a targeted material for its relative safety and photocatalytic activity under visible light. In this study, a successful simple and energy-saving route was applied to prepare BiOI through a sonochemical process at room temperature. The characterization of the prepared BiOI was conducted by physical means. The transmission electron microscope (TEM) image showed that the BiOI comprises nanoparticles of about 20 nm. Also, the surface area of the BiOI was found to be 34.03 m2 g−1 with an energy gap of 1.835 eV. The adsorption and photocatalytic capacities of the BiOI were examined for the indigo carmine dye (IC) as a model water-pollutant via the batch experiment methodology. The solution parameters were optimized, including pH, contact time, IC concentration, and temperature. Worth mentioning that an adsorption capacity of 185 mg·g−1 was obtained from 100 mg L−1 IC solution at 25 °C within 60 min as an equilibrium time. In addition, the BiOI showed a high degradation efficiency towards IC under tungsten lamb (80 W), where 93% was removed within 180 min, and the complete degradation was accomplished in 240 min. The fabricated BiOI nanoparticles completely mineralized the IC under artificial visible light, as indicated by the total organic carbon analysis.

Effect of polycarboxylate superplasticizers on the growth of ettringite in deionized water and synthetic cement pore solution

Ettringite is the crucial hydrating phase controlling the rheology of the paste at the beginning of the cement hydration. Yet, while previous studies speculate on how the rheology of the paste depends on the morphology and size of ettringite, only limited data examine this question systematically in the C3A-CaSO4 system, probably linked to characterization limitation arising from the heterogeneous of cement paste and a small proportion of ettringite. On the other hand, polycarboxylate ether/ester (PCE) are well known to greatly modified the morphology and size of ettringite. It remains however unclear how PCE adsorption affects the growth of ettringite. In this paper, the effects of dosages of PCE on the growth of ettringite in deionized water and synthetic cement pore solution were investigated by using X-ray diffraction (XRD), thermogravimetry–differential thermogravimetry (TG-DTG) analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microcopy (SEM) and total organic carbon (TOC) analyzer. Adsorption kinetics and isotherms of PCE on the surface of ettringite crystals were also examined. PCE exerted no effect on the types of products, but its adsorption changed the proportion, stability, and morphology of ettringite. Sulfate ions and PCE were adsorbed on the face of rectangular prism of ettringite crystals preferentially, which limited their growth in the {101¯0} faces and resulted in their longitudinal growth. The inhibition effect of PCE on the growth of ettringite crystals is positive correlated with its adsorption amount on ettringite and is weakened as the crystallization time increases. The adsorption kinetics and isotherms of PCE on the surface of ettringite followed the pseudo-second-order and Freundlich equations respectively.

Plasmonic effect and bandgap tailoring of Ag/Ag2S doped on ZnO nanocomposites for enhanced visible-light photocatalysis

Ag/Ag2S-ZnO nanocomposites were prepared via a simple hydrothermal process followed by a plasmonic Ag+ reduction through a photo-deposition method. Ag2S was introduced to narrow the overall composite bandgap and activate the surface plasmon resonance (SPR) effect of the Ag+ cation present. The physicochemical properties of the as-synthesised catalysts were characterised by X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM and TEM), Brunauer-Emmett-Teller (BET) analysis. Fourier-transform infrared spectroscopy (FTIR), Ultraviolet diffuse reflectance spectroscopy (UV–vis DRS), photoluminescence emission spectra (PL) and X-ray photoelectron spectroscopy (XPS) was conducted to investigate the photo-absorption and emission spectra of the nanocomposites. The degradation efficiency of all the synthesised catalysts (ZnO, Ag2S, Ag/ZnO and Ag2S/ZnO) prior to the final product, Ag/Ag2S/ZnO was tested and compared. Results showed that the ternary Ag/Ag2S/ZnO achieved a 98 % phenol removal compared to 50 %, 11 %, 64 % and 93 % for ZnO, Ag2S, Ag/ZnO and binary Ag2S/ZnO, respectively. The degradation kinetics followed the Langmuir-Hinshelwood model, which typically describes heterogeneous photocatalytic surface reactions. The linear fits had R2 values higher than 0.97, which confirms the degree of accuracy or statistical fitness to the kinetic model. Degradation scavenger test confirmed the holes (h+) as the main inhibitor and identified the superoxide O2•¯ radical as the main active specie responsible for the degradation. Total organic carbon analysis using the ternary Ag/Ag2S-ZnO catalyst only achieved a 74% phenol mineralization after 24 h of photocatalysis. Recyclability tests showed good phenol removal stability of Ag/Ag2S-ZnO at 41 % after five recycle runs. Hence, a synergistic degradation mechanism responsible for the efficient photo-degradation performance was proposed.

Seasonal and spatial variations of ecological risk from potential toxic elements in the southern littoral zone of İzmir Inner Gulf, Turkey.

This study aims to investigate the ecological risk level of potentially toxic elements (PTEs) in İzmir Inner Gulf. Samples were taken from 16 stations selected in the southern littoral zone of the gulf for four seasons (winter, spring, summer, and autumn). Multi-element, total organic carbon, chlorophyll-a, biogenic silica and carbonate analyses were carried out. To determine contamination level and ecological risks, some indices (enrichment factor, modified hazard quotient and potential risk analysis, toxic risk index, etc.) were calculated. Mo and Pb show significant anthropogenic enrichment in the inner gulf. These are followed by Cu, Cd, and Zn with moderate accumulation. Risk assessment indices point out that Ni, Cr, and Cd have a serious potential to create risk for ecosystem, and these are followed by As, Hg, Pb, Zn, and Cu. According to the spatial distribution, land use maps, and factor analysis, the Cd, Zn, and Cr increases are localized at the mouth of the Poligon Stream. Pb and Cu accumulate at the mouth of four large streams feeding the eastern part of the gulf. Pb and Cu enrichment is associated with traffic and industrial discharges. While one of the sources of Hg is anthropogenic, another source is eutrophication resulting from benthic and planktonic diatom blooms. While Fe and Mn are added to the gulf via rivers as a result of rock and soil erosion, another source is sediment. Cr, As, and Ni come from anthropogenic and lithogenic sources and immobilized in sediment. CO3-2 source is marine (biogenic) and dilutes other immobilized PTEs. It is understood that the peripheral stations rich in allochthonous organic carbon and the stations close to the central area rich in autochthonous organic carbon contribute to the carbon source in question.