Total Organic Carbon Measurements Research Articles

Development of ultrathin 2D layered titanate Pt/K2Ti4O9/rGO nanocomposites for enhanced visible active photocatalytic detoxification of harmful organic pollutants

In this work, different wt. % of rGO-loaded Pt-K2Ti4O9 (x = 2.5, 5, 7.5, 10, and 12.5wt.%) nanocomposites were prepared by a facile hydrothermal process and used for the degradation of two different dyes such as congo red (CR) methylene blue (MB) and tetracycline (TC) antibiotic solution under visible light illumination. The bare K2Ti4O9 (labeled as KTO) and the most active Pt-K2Ti4O9/5% rGO (labeled as Pt-KTO/5% rGO) composite catalysts were thoroughly characterized by XRD, FT-IR, Raman, XPS, FE-SEM with EDS, HR-TEM, UV-DRS, and PL analyses. The photocatalytic activity of Pt-KTO/5% rGO was remarkable compared to bare KTO and other rGO-supported catalysts. Pt-KTO/5% rGO composite photocatalyst showed enhanced photocatalytic degradation of 97%, 99%, & 99% for CR, MB & TC at 180, 120 and 180min, respectively. Mineralization of dyes (TOC of 85%, 87%, and COD of 76%, 79% for CR, MB) and antibiotics (TOC of 78% and COD of 69% for TC) was confirmed by chemical oxygen demand (COD) and total organic carbon (TOC) measurements. The Pt-KTO/5% rGO catalyst showing the highest activity also demonstrates recyclability. A suitable photocatalytic reaction mechanism has been proposed for the higher activity of Pt-KTO/rGO at neutral pH under visible light irradiation.

Chemical oxygen demand and biochemical oxygen demand analysis of discharge waters from laundry industry: monitoring, temporal variability, and biodegradability

In Europe, chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) are used as organic indicators for the analytical characterization of laundry water. However, the values of these indicators are derived from one-off analytical measurements at a defined frequency. In addition, there are few data on the temporal variability of COD and BOD5 parameters and on water biodegradability beyond 5 days. In this work, samples of physicochemical treated wastewater were collected for 1 year and their content in COD and BOD5 measured, with BOD monitored over 35 days. The results showed that, for the 24 samples studied, the average and standard deviation values were 835 ± 176 mg/L for COD and 445 ± 114 mg/L for BOD5, indicating a biodegradability index of 2.0 ± 0.4. The interpretation of the data also indicated that the concentrations were close to emission limit value, particularly for BOD5. BOD21 values were particularly high compared to the initial COD, indicating the biodegradability of water. Laundry effluents were also rich in substances very quickly biodegradable, which has been demonstrated by the values of the ratio between BOD7 and BOD5. However, a significant proportion of surfactants is not degraded, as shown by measurements of total organic carbon and anionic surfactant analysis. The results of this study could help the industrial partner involved in our project to guide its choice of the complementary method to better treat wastewater and to reduce its organic load.

Dissolved Organic Matter Behaviour by Conventional Treatments of a Drinking Water Plant: Controlling Its Changes with EEM-PARAFAC

In the last 20 years, several articles related to the use of fluorescence excitation–emission matrices—parallel factor analysis (EEM-PARAFAC) to monitor dissolved organic matter (DOM) in drinking- and wastewater treatment plants were published. Noteworthy, its use in respective quality control laboratories remains scarce. To extend its popularisation, in this work, EEM-PARAFAC was employed to analyse the DOM composition changes along the different stages of the drinking water treatment plant administrated by Società Metropolitana Acque Torino. The best PARAFAC model was the one of three components, indicating that the Po River is constituted, mainly, by humic acid-like (HA-L) and tryptophan-like (Try-L) substances, the tyrosine-like ones being negligible (Tyr-L). Results indicated that physical treatments (sedimentation) did not produce a reduction in the PARAFAC scores; however, a 50% decay in 254 nm absorbance was observed. Fluorescent DOM was only removed with chemical treatments, obtaining ca. 70% HA-L scores decay with ozonation and 40% with chlorination. Furthermore, although ozonation degraded HA-L substances, the Try-L scores increased by 25%, indicating the transformation of HA-L into smaller molecules. On the contrary, total organic carbon measurements only exhibited a significant change when comparing the treatment plant’s inlet and outlet (approximately a 45% decrease), but not within intermediate processes.

Exploring pre-neolithic environmental dynamics: paleoecology around the Göbekli Tepe based on a multiproxy approach in southeastern Türkiye

Abstract Background and aims Paleoecological findings from soil samples recovered near the Göbekli Tepe indicate an environment that sustains a variety of multiproxy analyses, revealing prominent changes in ecological conditions. Methods Soil samples were collected in the vicinity of the pre-Neolithic site in the Göbekli Tepe. These sediment samples underwent comprehensive analysis utilizing a multiproxy approach, which included pollen analysis, total organic carbon (TOC) and total inorganic carbon (TOC) measurements, and X-ray fluorescence (XRF) elemental analysis. Results Total organic carbon varied significantly in the SK-1 section, with lower levels at the bottom and higher levels at the top. The Ca/Ti ratio, which is indicative of weathering and moisture availability, typically increased in the early Holocene and briefly decreased at approximately 13,354 years BP. The Sr/Ti ratio, related to weathering and erosion processes, also suggests intensified weathering. The presence of deciduous forests and the increase in organic carbon values further support the notion of favorable environmental conditions during the early Holocene. In contrast, the lower levels of SK-1 show lower organic carbon values, lower Ca/Ti and Sr/Ti ratios, and greater abundances of herbaceous plants and steppes, indicating colder and drier conditions at 13,354 years BP. Conclusion A significant increase in organic carbon values and the presence of deciduous Quercus in the upper levels of the SK-3 section suggest a period of increased organic productivity and the existence of deciduous forests during the early Holocene at the Göbekli Tepe.

Solvent screening for the extraction of aromatic aldehydes

The aromatic aldehydes vanillin, syringaldehyde, and p-hydroxybenzaldehyde find applicability in a broad field ranging from additives in food, cosmetics, and fragrances to precursors of electrochemically active substances used in organic redox flow batteries. These aldehydes can be obtained by wet oxidation of lignin a macromolecule present in woody biomass followed by the isolation via solvent extraction from the resulting acidic solutions.The present study investigates solvents grouped by esters, ethers, terpenes, and terpenoids, in addition to 1-octanol for their performance in extraction of the aromatic aldehydes vanillin, p-hydroxybenzaldehyde and syringaldehyde from an acidic aqueous solution. Solvent extractions are performed at 25 and 50 °C in double-walled tempered separation funnels. The overall extraction efficiency is determined by back-extractions performing a pH-swing at 25 °C. Aldehyde concentrations are measured by HPLC-UV. Karl-Fischer titration and total organic carbon measurements are used to account for the mutual solubility.The best-performing solvent in the case of aldehyde yields at low mutual solubility is given by the ester butyl acetate with extraction efficiencies of 96.53 % for p-hydroxybenzaldehyde, and > 95 % and > 93 % for vanillin and syringaldehyde, respectively. The highest overall extraction efficiency among all solvents suitable for alkaline back-extraction is achieved by cyclopentyl methyl ether with 94.73 % for p-hydroxybenzaldehyde, 94.04 % for vanillin and 87.91 % for syringaldehyde. The solvents geraniol, 1-octanol, ethyl acetate, and 2-methyl tetrahydrofuran show increased uptake of water with ethyl acetate, and 2-methyl tetrahydrofuran pointing out a high solvent loss with 9.82 vol% and 15.84 vol%, respectively. The terpene p-cymene showed preferable extraction of vanillin and syringaldehyde over p-hydroxybenzaldehyde with mutual solubility below 0.02 vol%, which makes it and interesting candidate for multistage solvent extraction.

Hydrocarbon Source Rock Evaluation of the Lucaogou Shale in the Periphery of Bogeda Mountain (SE Junggar Basin, China) and Its Implications for Shale Oil Exploration: Insights from Organic Geochemistry, Petrology, and Kinetics Pyrolysis

Since the discovery of the vast Jimusaer shale oilfield in the southeastern Junggar Basin in 2012, there has been considerable interest in neighboring areas around Bogeda Mountain that have shale oil potential. The primary productive interval in the basin, the Middle Permian Lucaogou Formation (P2l), is well-developed in the areas of Qitai, Mulei, Shiqiantan, Chaiwopu, and Miquan. In this study, we conducted an assessment of the hydrocarbon generation potential of the P2l in these five areas and compared it with that of the P2l in the Jimusaer oilfield, which were determined by GC-MS, total organic carbon (TOC) and vitrinite reflectance (Ro) measurements, Rock-Eval pyrolysis, and organic petrology to investigate the type, origin, thermal maturity, hydrocarbon potential, and oil/gas proneness of organic matter in the P2l. Additionally, we applied open-system pyrolysis of hydrocarbon generation kinetics to explore differences in hydrocarbon generation and expulsion across various P2l mudstone/shale in the southeastern Junggar Basin. The findings of this study revealed that the P2l shale in Qitai and Miquan areas contains more abundant and lower thermally mature organic matter (early mature–mature stage), characterized by primarily Type II1–I kerogen, similar to that found in the P2l shale of the Jimusaer oilfield. Conversely, the P2l shale in Mulei, Shiqiantan, and Chaiwopu contains less abundant and more thermally mature organic matter (mainly mature–highly mature stage), dominated by Type II2–III kerogen. Consequently, shale in these areas is considerably less desirable for oil exploration compared to the Jimusaer shale. The semi-deep to deep lake facies in Miquan and Qitai exhibit the most promising exploration potential. This study can serve as a guide for shale oil exploration in the southeastern Junggar Basin.

Total organic carbon measurements reveal major gaps in petrochemical emissions reporting.

Anthropogenic organic carbon emissions reporting has been largely limited to subsets of chemically speciated volatile organic compounds. However, new aircraft-based measurements revealed total gas-phase organic carbon emissions that exceed oil sands industry-reported values by 1900% to over 6300%, the bulk of which was due to unaccounted-for intermediate-volatility and semivolatile organic compounds. Measured facility-wide emissions represented approximately 1% of extracted petroleum, resulting in total organic carbon emissions equivalent to that from all other sources across Canada combined. These real-world observations demonstrate total organic carbon measurements as a means of detecting unknown or underreported carbon emissions regardless of chemical features. Because reporting gaps may include hazardous, reactive, or secondary air pollutants, fully constraining the impact of anthropogenic emissions necessitates routine, comprehensive total organic carbon monitoring as an inherent check on mass closure.

Transformation and aging of organic matter during degradation and preservation in marine sediment of the northern South China Sea

Organic matter (OM) preservation in marine sediments is an important sink in the carbon cycle and the isotopic records of the preserved OM provide useful information on the sources, biodegradation, and transformation of organic carbon during early diagenesis. Here, we present radiocarbon data combined with stable carbon isotope measurements of total organic carbon (TOC) and four organic fractions, namely, total lipids, hydrolysable amino acids (THAAs), humic acids (HAs), and acid-base insoluble OM, separated from four sediment cores collected from the South China Sea (SCS), to reveal their sources and transformation. The total lipids, THAAs, HAs and acid-base insoluble OM fractions account for 1.1 ± 0.4%, 3.1 ± 1.6%, 12.7 ± 9.4% and 61.6 ± 10.0% of the TOC (the percentages of organic fraction in TOC), respectively, and the acid-base insoluble OM is the dominant fraction of TOC preserved in the sediments. Distinct differences in both 13C and 14C values are found among these organic fractions. The δ13C values are more depleted in total lipids and HAs (−23.1‰ to −30.2‰) than in THAAs and the acid-base insoluble OM (−15.3‰ to −20.6‰), which indicates that HAs could be polymerized from lipid-like materials. The acid-base insoluble OM has the lowest Δ14C values (−848‰ to −358‰), with the oldest 14C ages (mean of 7330 years before present) compared to total lipids (−574‰ to −253‰, 3860 years), THAAs (−331‰ to −66‰, 1527 years) and HAs (−569‰ to −168‰, 2916 years) in these sediment cores. The δ13C and Δ14C values of THAA in the sediment are similar to those of pore-water dissolved organic carbon (DOC), indicating that THAA is preferentially degraded and converted to DOC. These results reveal that OM derived from marine and terrestrial sources decompose selectively and contribute differently to the organic fractions during early diagenesis and preservation in marine sediment. The very aged acid-base insoluble fraction is likely formed as a complex of the most refractory OM during microbial degradation and alteration of TOC, representing a major mechanism of OM sequestration in marine sediments.

Development and performance evaluation of online monitors for near real-time measurement of total and water-soluble organic carbon in fine and coarse ambient PM

In this study, we developed two online monitors for total organic carbon (TOC) and water-soluble organic carbon (WSOC) measurements in fine (dp < 2.5 μm) and coarse (2.5 μm < dp < 10 μm) particulate matter (PM), respectively. Their performance has been evaluated in laboratory and field tests to demonstrate the feasibility of using these monitors to measure near real-time concentrations, with consideration of their potential for being employed in long-term measurements. The fine PM collection setup was equipped with a versatile aerosol concentration enrichment system (VACES) connected to an aerosol-into-liquid-sampler (AILS), whereas two virtual impactors (VIs) in tandem with a modified BioSampler were used to collect coarse PM. These particle collection setups were in tandem with a Sievers M9 TOC analyzer to read TOC and WSOC concentrations in aqueous samples hourly. The average hourly TOC concentration measured by our developed monitors in fine and coarse PM were 5.17 ± 2.41 and 0.92 ± 0.29 μg/m³, respectively. In addition, our TOC readings showed good agreement and were comparable with those quantified using Sunset Lab EC/OC analyzer operating in parallel as a reference. Furthermore, we conducted field tests to produce diurnal profiles of fine PM-bound WSOC, which can show the effects of ambient temperature on maximum values in the nighttime chemistry of the winter, as well as on increased photochemical activities in afternoon peaks during the summer. According to our experimental campaign, WSOC mean values during the study period (3.07 μg/m³ for the winter and 2.7 μg/m³ for the summer) were in a comparable range with those of earlier studies in Los Angeles. Overall, our results corroborate the performance of our developed monitors in near real-time measurements of TOC and WSOC, which can be employed for future source apportionment studies in Los Angeles and other areas, aiding in understanding the health impacts of different pollution sources.

Geochemical evaluation and source rock zonation by multi-layer perceptron neural network technique: a case study for Pabdeh and Gurpi Formations-North Dezful Embayment (SW Iran)

In this study, using a multi-layer perceptron neural network (MLPNN) model, total organic carbon (TOC) and hydrogen index (HI) values for Pabdeh and Gurpi Formations in the oil fields of Naft Sefid (NS-13), Kupal (KL-36, KL-38, and KL-48) and Palangan (PL-2) were calculated in the North Dezful Embayment located in the southwest of Iran. To build the MLPNN model, the geochemical data calculated by the Rock–Eval pyrolysis method (TOC and HI) and the conventional petrophysical well log data, including sonic transit time log (DT), formation density log (RHOB), total resistivity log (RT), spectral gamma-ray log, computed gamma-ray log and neutron porosity log from the NS-13 well were used. The log data were the input layer, and the geochemical data were the output layer of the model. Twenty-four datasets were used for MLPNN training, and seven datasets were used for MLPNN testing. Two hidden layers were considered in this technique. Each hidden layer has an activation function (tanh) and a solver parameter (lbfgs). The accuracy of measurement of TOC and HI indices of Pabdeh and Gurpi Formations in terms of R2 was 0.93 and 0.90, respectively. This model has higher accuracy than the ΔlogR technique (R2: 0.28). Considering the relationships between the input data and other wireline logs is an advantage of this technique. These two formations have five source rock zones. Pabdeh Formation has three zones. The middle zone of the Pabdeh Formation (Pz. II) has the highest TOC (2.6 wt%) and source rock potential. Pabdeh Formation has kerogen type II. Gurpi Formation has a weaker source rock potential than Pabdeh Formation due to its low TOC content (< 1%). Both source rock zones of this formation have low TOC, but in some layers of the lower zone of the Gurpi Formation (Gz. II), high values for TOC were predicted. Gurpi Formation has Kerogen types II and III.

Comparison of measured versus modeled TOC in the Tuscaloosa marine shale of Southwestern Mississippi, U.S.A.

This study presents a comparison of measured versus modeled total organic carbon (TOC) in the Upper Cretaceous Tuscaloosa marine shale (TMS) of southwestern Mississippi as a case study to evaluate the effects of mineralogy on the TOC estimated from the ΔlogR method. The ΔlogR method is utilized to calculate TOC, which involves baselining sonic transit time and resistivity log curves in a non-source rock section of the formation. In our application, the well log curves were baselined in the upper TMS, which is described as a non-source rock section, and in the lower TMS above the high resistivity zone (HRZ), which is described as having a higher carbonate content. The ΔlogR calculated TOC values from these two baselining approaches show that the lower baseline results in improved agreement between measured TOC and calculated TOC. This improvement is likely to be due to the lower baseline accounting for the increase in resistivity caused by higher carbonate content, in addition to any presence of TOC. The upper baseline, which has a lower carbonate content, does not account for this resistivity increase. Additionally, sample type appears to affect the comparison of measured and ΔlogR calculated TOC. Most of the samples used in this study are legacy cuttings that were not preserved during storage, exposing the high surface area cuttings to increased rates of oxidation, whereas geophysical logs record the rock properties in situ. To account for this oxidation effect, the difference between the medians of the TMS HRZ TOC core and cuttings values was added to each TOC measurement in this study, resulting in a median measured TOC value that is similar to the median of the lower TMS-baselined ΔlogR calculated TOC value. Overall, this study demonstrates that carbonate content and sample type can affect how well measured and ΔlogR-modeled TOC values compare.

Reconciliation of total particulate organic carbon and nitrogen measurements determined using contrasting methods in the North Pacific Ocean as part of the NASA EXPORTS field campaign

Measurements of particulate organic carbon (POC) are critical for understanding the ocean carbon cycle, including biogenic particle formation and removal processes, and for constraining models of carbon cycling at local, regional, and global scales. Despite the importance and ubiquity of POC measurements, discrepancies in methods across platforms and users, necessary to accommodate a multitude of needs and logistical constraints, commonly result in disparate results. Considerations of filter type and pore size, sample volume, collection method, and contamination sources underscore the potential for dissimilar measurements of the same variable assessed using similar and different approaches. During the NASA EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) 2018 field campaign in the North Pacific Ocean, multiple methodologies and sampling approaches for determining POC were applied, including surface inline flow-through systems and depth profiles using Niskin bottles, in situ pumps, and Marine Snow Catchers. A comparison of results from each approach and platform often resulted in significant differences. Supporting measurements, however, provided the means to normalize results across datasets. Using knowledge of contrasting protocols and synchronous or near-synchronous measurements of associated environmental variables, we were able to reconcile dataset differences to account for undersampling of some particle types and sizes, possible sample contamination and blank corrections. These efforts resulted in measurement agreement between initially contrasting datasets and insights on long-acknowledged but rarely resolved discrepancies among contrasting methods for assessing POC concentrations in the ocean.

Hollow fiber liquid membrane: A promising approach for elimination of pharmaceutical compounds from wastewater

Pharmaceutical compounds present in water pose significant challenges, particularly due to their low concentrations in water streams. Hollow fiber liquid membranes provide a flexible and easily manageable solution, enabling the concentration of specific contaminants. This concentration step significantly improves their effective removal from water systems. The study focused on using hollow fiber liquid membrane technology to effectively remove diclofenac (DCF) and ibuprofen (IBU), two pharmaceutical compounds. A concentration of 40% Cyanex 923 (Cy923) dissolved in kerosene was selected as the preferred extractant due to its stability and quick extraction properties. The stability of the system was tested with a pseudo-emulsion, enabling repeated use of the system. Additionally, an analytical model was developed to calculate the membrane's permeability. In order to enhance the degradation and mineralization of the pharmaceutical compounds and their byproducts, ozonation was integrated with the hollow fiber liquid membrane system in a single system. Measurement of total organic carbon (TOC) revealed a significant reduction of 72% for diclofenac and 57% for ibuprofen with an initial ozone concentration of 10 mg/L and operating under the optimal conditions of hollow fiber liquid membrane.

The design and characterisation of a Z-scheme Bi2O2S/ZnO heterojunction photoanode for the photoelectrochemical removal of ciprofloxacin in synthetic and real wastewater

Towards the engineering of semiconductors for improved visible light photoelectrochemical degradation of organic pollutants in wastewater, we present the preparation of a Z-scheme heterojunction of Bi2O2S and ZnO nanoparticles for the removal of ciprofloxacin from wastewater. The Bi2O2S/ZnO nanocomposite heterojunction was synthesised via an in-situ hydrothermal method and deposited on FTO substrate to form the photoanode. The semiconductors and the photoanodes were characterised with electron microscopy, XRD, photo-electrochemistry, photoluminescence, XPS and UV/Vis diffusive reflectance techniques. The degradation of ciprofloxacin was enhanced by the heterojunction in comparison with the Bi2O2S and ZnO photoanodes. We attribute the enhanced performance to the presence of an internal electric field (IEF), the low rate of recombination of photogenerated electrons and holes, lower charge transfer resistance, and high photocurrent density of the heterojunction based on data from photoluminescence, electrochemical impedance spectroscopy, XPS, and photocurrent response. The extent of mineralisation of ciprofloxacin was calculated as 86 % from total organic carbon (TOC) measurement. LC-MS analysis provided the degradation pathway and premise for the reaction scheme, while quantitative structure–activity relationship (QSAR) model was used to predict the toxicity of the intermediate and by-product. The Bi2O2S/ZnO photoanode was stable after seven treatment cycles. The photoelectrochemical reactor was used in the treatment of ciprofloxacin in real wastewater with 87 % TOC removal. Thus, the paper reveals the performance of a unique Z scheme band gap engineering of semiconductors for application in the removal of pharmaceuticals in wastewater.

Energy efficient sunshine active Ag decorated WO3/HNT nanocomposite for accelerated detoxification of hazardous dye-based emerging pollutant

Herein, we report that the tungsten trioxide (WO3) nanosheets and 2%Ag/15%WO3/HNT (Ag/WO3/HNT) composite photocatalysts were synthesized by the hydrothermal process and solvent evaporation methods. Various characterization techniques such as XRD, FT-IR, FE-SEM, EDS, HR-TEM, and UV-DRS were used to investigate the bulk and surface properties of bare and composite photocatalysts. The photocatalytic performance of halloysite nanotube (HNT), WO3/HNT, and Ag/WO3/HNT composite photocatalysts were evaluated by methylene blue (MB) dye degradation efficiency under solar light irradiation for 90 min. Among the various catalysts, Ag/WO3/HNT photocatalyst showed significant photocatalytic performance (96% degradation for MB dye). The existence of Ag indicates that surface plasmon resonance (SPR) impacts the developed composite and acts as an electron mediator. The scavenger experiment showed that the superoxide radical anions play a significant role in MB degradation under solar light with the most active Ag/WO3/HNT photocatalyst. The degradation of the MB dye has been monitored by Total Organic Carbon (TOC) measurements. The degradation intermediates of MB were analyzed by GC-MS, and a suitable degradation pathway was proposed. The most active Ag/WO3/HNT photocatalyst was also found to be the most stable and recyclable. The trapping experiment with Ag/WO3/HNT composite catalyst has led to the development of a dye degradation mechanism.

A magnetite catalysed heterogeneous solar photo electro-Fenton system enhanced with lanthanum doped bismuth ferrite photoanode for the degradation of aspirin in water

The effect of photoanode on a solar photo electro-Fenton system (SPEF) consisting of a magnetite nanoparticle catalyst impregnated carbon felt cathode is studied by coupling the SPEF system to a lanthanum-doped bismuth ferrite (La-BFO) photoanode. The resulting system, referred to as La-BFO /SPEF, was used in the degradation of acetyl salicylic acid in wastewater. The synthesised La-doped/undoped BFO photoanodes and magnetite nanoparticles were characterised with SEM, XRD and FTIR. The heterogeneous electro-Fenton system was prepared by attaching the magnetite nanoparticle to a carbon felt electrode through magnetisation. The effects of La dopant concentration in the photoanode material (doped and undoped BFO on a fluorine doped tin oxide substrate), pH values, current density and anodic oxidation contribution to the SPEF system were explored through parameters such as total organic carbon (TOC) measurements and mineralization current efficiency. A TOC removal of 68 % and 54 % was recorded for the La-doped photoanode (La-BFO/SPEF) and undoped system (BFO/SPEF) respectively, thus reflecting the contribution from the band gap tuning of the photoanode material. The predominant species in the degradation of acetyl salicylic acid were deduced by radical scavenging experiments. The coupling approach and the irradiation with visible light, enhanced the overall performance of the degradation system.

Congregating Ag into γ-Bi2O3 coupled with CoFe2O4 for enhanced visible light photocatalytic degradation of ciprofloxacin, Cr(VI) reduction and genotoxicity studies

The work attempts to construct a highly effective γ-Bi2O3/CoFe2O4/Ag visible active photocatalyst for the enhanced degradation of ciprofloxacin (CIP) and Cr(VI) reduction. γ-Bi2O3/CoFe2O4/Ag photocatalyst was prepared by simple solid phase and co-precipitation methods. The nanosphere shaped CoFe2O4 photocatalyst are embedded on top of γ-Bi2O3 nanotriangle. The addition of Ag into γ-Bi2O3/CoFe2O4 heterojunction primitively facilitates the photocatalytic activity in higher rate. The quantitative analysis of photocatalyst possesses to have lower e−/h+ recombination rate compared to its counterparts. The prepared γ-Bi2O3/CoFe2O4/Ag photocatalyst showed 96.6% degradation of CIP in 220 min and 99.2% reduction of Cr(VI) in 120 min. Additionally, γ-Bi2O3/CoFe2O4/Ag showed outstanding recyclability and long-term stability with a degradation efficiency of 96.5% even after six cycles. The intermediate products formed were identified and the degradation pathway was elucidated by gas chromatography-mass spectrometry analysis. Total organic carbon measurement was carried over to assess the efficiency of complete degradation and the removal percentage was found to be 98%. The end product toxicity study towards bacteria was proven to have less toxicity level when compared to parent compound. Lastly, the genotoxicity of γ-Bi2O3/CoFe2O4/Ag photocatalyst was tested in Allium cepa and the results confirmed to have no cause of toxicity impacts. Overall, the work not only tends to provide a highly visible active γ-Bi2O3/CoFe2O4/Ag photocatalyst, but also attributes to have no further negative imprints in the environment.

RESEARCH ON THE PHYSICAL AND CHEMICAL PROPERTIES OF SEWAGE TREATMENT SLUDGE BIOCHAR AND ITS PREPARATION FOR WASTEWATER

Treatment and recycling of sludge waste have developed into a research focus in recent years. Today, nutrient recovery from wastewater and sludge has received much attention from regulators, academia, industry, and the general public. Institutions and governments around the globe are now seeking innovation to implement a “circular economy” for sewage sludge usage. The development of cost-effective and environmentally friendly disposal processes is necessary to meet political demands. In developing countries, common approaches to the treatment such as incineration and landfilling, cause unwanted secondary pollution. The study aims to determine sewage sludge biochar’s physical and chemical properties and its preparation for wastewater treatment. The chosen chemical properties of sewage sludge biochar were electrical conductivity (EC), total organic carbon (%) content, physical properties were volatile solids, ash content, and also conducted phosphorus leaching experiment. It was determined that by increasing the pyrolysis temperature, the electrical conductivity (from 665 µS/cm to 277 µS/cm) and total organic carbon (from 29.03% to 17.25%) measurements decreased. By increasing the pyrolysis temperature, the ash content (from 50.07% to 69.45%), and volatile solids (from 53.61% to 74.55%) measurements increased.

Fabrication of Ag/WO3/g-C3N4 composites for the photocatalytic degradation of harmful dyes

In the present work, it is noticed that the synthesis of photocatalytic bare and composite materials: i) bare graphitic carbonitride g-C3N4 (GCN), ii) modified with tungsten oxide WO3/g-C3N4 (WGCN), and iii) with both tungsten oxide and silver nanoparticles WO3/Ag/g-C3N4 (WAgGCN), by three different methods: calcination, precipitation, and ultrasonication. Also, their photocatalytic efficiencies were evaluated towards the photodegradation of different dyes under visible, UV, and sunlight irradiations with promising results. Here, the WAgGCN composite showed significant photocatalytic performance to decolorized Methylene Blue (98%) and Crystal Violet (95%), together with high chemical stability and excellent recyclability. The presence of Ag shows the influences of surface plasmon resonance and acts as an electron mediator in the formed heterostructures. The photogenerated holes performed vital roles in the catalytic degradation of dye solutions over the WAgGCN composite catalyst, confirmed by radical trapping experiments. Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD) measurements confirmed the mineralization of the dyes.

Using NIR irradiation and magnetic bismuth ferrite microparticles to accelerate the removal of polystyrene microparticles from the drinking water

Magnetic bismuth ferrite (BiFO) microparticles were employed for the first time for the removal of polystyrene (PS) nano/microplastics from the drinking water. BiFO is formed by porous agglomerates with sizes of 5–11 μm, while the PS nano/microparticles have sizes in the range of 70–11000 nm. X-ray diffraction studies demonstrated that the BiFO microparticles are composed of BiFeO3/Bi25FeO40 (the content of Bi25FeO40 is ≈ 8.6%). Drinking water was contaminated with PS nano/microparticles (1 g L−1) and BiFO microparticles were also added to the contaminated water. Later, the mixture of PS-particles + BiFO was irradiated with NIR light (980 nm). Consequently, PS nano/microparticles melted on the BiFO microparticles due to the excessive heating on their surface. At the same time, the NIR (near infrared) light generated oxidizing agents (∙OH and h+), which degraded the by-products formed during the photocatalytic degradation of PS nano/microparticles. Subsequently, the NIR irradiation was stopped, and a Neodymium magnet was utilized to separate the BiFO microparticles from the water. This last procedure also permitted the removal of PS nano/microparticles by physical adsorption. Zeta potential measurements demonstrated that the BiFO surface was positively charged, allowing the removal of the negatively charged PS nano/microparticles by electrostatic attraction. The combination of the photocatalytic process and the physical adsorption permitted a complete removal of PS nano/microparticles after only 90 min as well as a high mineralization of by-products (≈95.5% as confirmed by the total organic carbon measurements). We estimate that ≈23.6% of the PS nano/microparticles were eliminated by photocatalysis and the rest of PS particles (≈76.4%) by physical adsorption. An outstanding adsorption capacity of 195.5 mg g−1 was obtained after the magnetic separation of the BiFO microparticles from the water. Hence, the results of this research demonstrated that using photocatalysis + physical-adsorption is a feasible strategy to quickly remove microplastic contaminants from the water.