Percent Of Total Organic Carbon Research Articles

A novel SRP/CdS heterostructure hollow nanospheres for outstanding photocatalytic performance

The construction of non-metals with semiconductors heterostructure has received a lot of interest as a photocatalyst for converting solar energy into hydrogen during the photocatalysis water-splitting process. Herein, we reported for the first time the controlled synthesis of heterostructure SRP/CdS hollow nanospheres via hydrothermal treatment. The results reveal that the surface roughening red phosphorus (SRP) was incorporated between loops of CdS nanospheres, constructing hollow nanosphere structures with suitable diameters. Moreover, the different SRP mass ratios could tune the band gap structures, increase the surface areas, and improve the electron-hole pair separation of the prepared photocatalysts, achieving promising results of the light-harvesting. Interestingly, the optimum heterostructure SRP0.03/CdS hollow nanospheres increases the photocatalytic rate of Rhodamine B (RhB) photodegradation to 1.78 times (88%) compared to pure CdS (78%) with rate constant (k) reaching 1.034 × 10−1 and 0.583 × 10−1 L·mol−1·min−1 for SRP0.03/CdS HNS and CdS NS, respectively. The scavenging experiments reveal that superoxide radicals (•O2–) and holes (h+) are the main active species in RhB photocatalysis. The chemical oxygen demand percent (%COD) and total organic carbon percent (%TOC) was investigated for RhB removal, achieving 77.89% and 65.53%, respectively, showing that RhB mineralization was not complete. Moreover, SRP0.03/CdS HNS achieves superior photoelectrochemical performance including transient photocurrent (17.68 μA/cm2), and current density (39.34 mA/cm2) under light irradiation. Thus, the developed construction of non-metals with semiconductor structures is thought to be a promising heterojunction photocatalyst for addressing hydrogen production issues.

Efficient charge separation and improved photocatalytic activity in Type-II & Type-III heterojunction based multiple interfaces in BiOCl0.5Br0.5-Q: DFT and Experimental Insight

The nanostructured, inner-coupled Bismuth oxyhalides (BiOX0.5X′0.5; X, X’ = Cl, Br, I; X≠X′) heterostructures were prepared using Quercetin (Q) as a sensitizer. The present study revealed the tuning of the band properties of as-prepared catalysts. The catalysts were characterized using various characterization techniques for evaluating the superior photocatalytic efficiency and a better understanding of elemental interactions at interfaces formed in the heterojunction. The material (BiOCl0.5Br0.5-Q) reflected higher degradation of MO (about 99.85%) and BPA (98.34%) under visible light irradiation than BiOCl0.5I0.5-Q and BiOBr0.5I0.5-Q. A total of 90.45 percent of total organic carbon in BPA was removed after visible light irradiation on BiOCl0.5Br0.5-Q. The many-fold increase in activity is attributed to the formation of multiple interfaces between halides, conjugated π-electrons and multiple –OH groups of quercetin (Q). The boost in degradation efficiency can be attributed to the higher surface area, 2-D nanostructure, inhibited electron-hole recombination, and appropriate band-gap of the heterostructure. Photo-response of BiOCl0.5Br0.5-Q is higher compared to BiOCl0.5I0.5-Q and BiOBr0.5I0.5-Q, indicating better light absorption properties and charge separation efficiency in BiOCl0.5Br0.5-Q due to band edge position. First-principles Density Functional Theory (DFT) based calculations have also provided an insightful understanding of the interface formation, physical mechanism, and superior photocatalytic performance of BiOCl0.5Br0.5-Q heterostructure over other samples.

Use of nanoscale zero-valent iron and nanoscale hydrated lime to improve geotechnical properties of gas oil contaminated clay: a comparative study

Soil stabilization using lime has been long used to improve geotechnical characteristics of soil for civil engineering purposes. Unlike lime, as far as known to the authors, there is no specific research for soil improvement by zero-valent iron. In this study nanoscale zero-valent iron (NZVI) particles and nanoscale hydrated lime (NHL) have been used to determine their effects on Atterberg limits, compaction properties, unconfined compressive strength (UCS) and shear strength parameters (c and ϕ) of a gas oil contaminated clay soil. To determine the optimal reaction time and NZVI dosage, percent of total organic carbon in the contaminated soil with 9 % of gas oil was measured. From experimental data, optimum reaction time and NZVI dosage were 24 days and 5 %, respectively. Then, the contaminated samples were prepared by mixing the soil with gas oil in amounts of 0, 3, 6 and 9 % by dry weight. The results showed a decrease in UCS, maximum dry density, optimum moisture content and internal friction angle and an increase in liquid limit (LL), plastic limit (PL) and cohesion. Finally, all contaminated specimens were mixed with 5 % of NZVI. After 24 days an increase in UCS, maximum dry density, optimum water content and shear strength parameters was seen. In addition, a decrease in LL and PL was observed. On the other hand, adding 5 % of NHL to the contaminated soil increased UCS, shear strength parameters, LL, PL, optimum moisture content and decreased plasticity index and maximum dry density of the soil after 24 days.

Variation of organic matter density with thermal maturity

An estimate or measurement of organic matter density is required for converting between the weight percent of total organic carbon (TOC) and the volume percent of organic matter for wireline log calibration; it is therefore important to recognize when significant changes in organic matter density occur. A method is presented for calculating organic matter density from measurements of crushed-rock dry grain density and Soxhlet-extracted TOC. I have investigated the thermal evolution of organic matter by tracking changes in the intrinsic density of organic matter as a function of thermal maturity. Organic matter density shows two step increases that correspond to the generation of liquid hydrocarbons in the oil window (up to ∼1.2% vitrinite reflectance [Ro]) and the conversion of organic matter to graphitelike carbon (more correctly, “turbostratic carbon”) at high thermal maturity (>4% Ro). Profound structural changes of organic matter may, in part, determine the maturity limits of source-rock tight liquids and shale-gas plays, particularly at high thermal maturity, where gas is hosted within the organic matter–hosted pore system.

Assessment of distribution and sources of pyrogenic carbon in the lower course of the Guadiana River (SW Iberian Peninsula)

PurposeThe main goal of this work was to determine the pyrogenic carbon (PyC) distribution in surficial sediments for the last 40 km of the Guadiana River (SW Iberian Peninsula). In addition, the changes in the contribution of terrestrial and marine organic matter (OM) sources and their relationship with the PyC contents were assessed.Materials and methodsSediments were collected from 22 stations within the lower course of the Guadiana River. All the samples were analyzed for total organic carbon (TOC), total nitrogen (TN), organic carbon to nitrogen atomic ratios (C/N), and stable carbon isotope ratio (δ13C) as indicators of changes in the sources of OM. PyC was determined according to the chemo-thermal oxidation method (CTO-375).Results and discussionTOC ranged from 0.25 to 2.37 %dw. The greatest TOC contents were located in sediments collected at the middle estuary. The C/N values ranged from 7.7 to 12.7, with slight relative increase in the marine input compared to pre-Alqueva times. Similar C/N ranges are representative of native soil OM, lacustrine OM, and local sedimentary OM. The δ 13C values of the sediment samples ranged from –25.0 to –27.6 ‰ illustrating a signature of C3 higher plants, marsh-plants, lacustrine plants, and freshwater algae present in the area of study and in the forests located upstream. PyC ranged between 0.17 and 0.74 gkg−1, with the highest contents measured in samples located close to urbanized areas. Sediments collected at the middle estuary, within a rural area, showed the lowest proportions of PyC relative to the percent of TOC (≤4 % TOC). The negative relationship between PyC to TOC ratio and TOC contents confirmed the selective preservation of PyC to degradation in the sedimentary OM of the Guadiana estuary. The carbon isotope composition of the final material after applying the CTO-375 method (hereafter called δ13CPyC) was ˂–30 ‰, suggesting that the PyC fraction was mainly composed of a mixture of fossil fuels and C3-charred biomass. Nevertheless, selective loss of the less recalcitrant OM fractions due to degradation and/or chemical alteration might contribute to lighter carbon isotope values of PyC.ConclusionsGeochemical data showed that sedimentary OM was composed of a mix of different OM sources, with a slight increase in the marine input after the Alqueva dam went into operation. The PyC content was higher close to urbanized areas of the Guadiana River estuary. The selective preservation of PyC in the sedimentary OM of the Guadiana estuary was observed.

Sonophotolytic degradation of synthetic pharmaceutical wastewater: Statistical experimental design and modeling

The merits of the sonophotolysis as a combination of sonolysis (US) and photolysis (UV/H2O2) are investigated in a pilot-scale external loop airlift sonophotoreactor for the treatment of a synthetic pharmaceutical wastewater (SPWW). In the first part of this study, the multivariate experimental design is carried out using Box–Behnken design (BBD). The effluent is characterized by the total organic carbon (TOC) percent removal as a surrogate parameter. The results indicate that the response of the TOC percent removal is significantly affected by the synergistic effects of the linear term of H2O2 dosage and ultrasound power with the antagonistic effect of quadratic term of H2O2 dosage. The statistical analysis of the results indicates a satisfactory prediction of the system behavior by the developed model. In the second part of this study, a novel rigorous mathematical model for the sonophotolytic process is developed to predict the TOC percent removal as a function of time. The mathematical model is based on extensively accepted sonophotochemical reactions and the rate constants in advanced oxidation processes. A good agreement between the model predictions and experimental data indicates that the proposed model could successfully describe the sonophotolysis of the pharmaceutical wastewater.

Aliphatic and polycyclic aromatic hydrocarbons in the surface sediments of the Mediterranean: assessment and source recognition of petroleum hydrocarbons

Coastal marine sediment samples were collected from ten sampling stations along the Egyptian Mediterranean coast in April 2010. All sediment samples were analyzed for aliphatic (C7 to C34) and polycyclic aromatic hydrocarbons (PAHs) as well as total organic carbon (TOC) contents and grain size analysis. Total aliphatic hydrocarbons ranged from 1621.82 to 9069.99 ng/g (dry weight), while aromatic hydrocarbons (16 PAHs) varied between 208.69 and 1020.02 ng/g with an average of 530.68 ± 225.86 ng/g dwt. Good correlations observed between certain PAH concentrations allowed to identify its origin. The average TOC percent was varied from 0.13 to 1.46 %. Principal component analysis was used to determine the sources of hydrocarbon pollutants in sediments of Mediterranean. Additionally, special PAHs compound ratios suggest the petrogenic origins.

Can hydrocarbon source rocks be identified on seismic data?

Hydrocarbon source rocks contain significant volumes of organic matter, are capable of expelling petroleum when heated, and have produced most of the world's known oil volumes. Recently, source rocks have also become recognized as unconventional economic reservoirs. Here we present a new way of identifying, characterizing, and mapping spatial distributions and variations of thick source rocks (>20 m) that is based on seismic data only. This has a significant impact on the prospect risk assessment of petroleum plays. Rock property studies of organic-rich claystones show that the acoustic impedance (AI), which is the product of compressional velocity and density, decreases nonlinearly with increasing total organic carbon (TOC) percent. Claystones mixed with low-density organic matter (TOC > 3%–4%) have significant lower AI and higher intrinsic anisotropy than otherwise similar nonorganic claystones. This gives the top and base source rock reflections characteristic negative and positive high amplitudes, respectively, which dim with increasing reflection angle. In addition, the TOC profile, which is a smoothed TOC percent curve, influences the top and base amplitude responses. An upward-increasing TOC profile has the highest amplitude at the top, while the opposite asymmetry is observed for downward-increasing TOC profiles. By using seismic data, we therefore can map lateral distribution, thickness, variation in TOC profiles, and, with local well calibration, convert AI data to TOC percent. This approach to mapping source rocks may change the way petroleum systems are evaluated.

Holocene paleoenvironmental change in inner continental shelf sediments, Southeastern Mediterranean, Egypt

The palynology of marine sediments from CS Core taken on the inner continental shelf offshore Nile Delta, Southeastern Mediterranean, has been used to reconstruct the regional paleoenvironment during the past 5380 yr BP. This includes detailing the relative abundances of dinoflagellate cysts, acritarchs, prasinophytes and other algal spores, microforaminiferal linings, crustacean eggs, and fungal hyphae. The composition and ecological interpretation of the dinoflagellate cyst assemblages, acritarchs and other non-pollen palynomorphs is discussed. Concentrations of dinoflagellate cysts range from 5926 to 416 specimens per gram of sediment, and the most common taxa were Lingulodinium machaerophorum, Operculodinium centrocarpum, Operculodinium israelianum, Polysphaeridium zoharyi, Spiniferites ramosus, Spiniferites mirabilis, Echinidinium transparantum and Protoperidinum nudum. The assemblages are like those on the Tunisian Shelf, but with more protoperidinioid cysts. It is concluded that the shelf sediments were deposited under suboxic bottom water conditions. A high nutrient supply to the area during the deposition of the CS Core sediments is evidenced by the strong significant correlation ( R-values) between the nutrient-demanding species, L. machaerophorum and P. zoharyi, toxic species, total phosphorous percent (TP%) and total organic carbon percent (TOC%). These data suggest that Nile discharge from the Damietta Channel increased during the past 5830 yr BP and was accompanied by increases in fresh or brackish water algae and fungal hyphae.

Organic carbon and its fractions in paddy soil as affected by different nutrient and water regimes

As an essential indicator of soil quality, soil organic carbon (SOC) and its fractions play an important role in many soil chemical, physical, and biological properties. A 4-year field experiment was conducted to determine the effects of different nutrient and water regimes on paddy soil organic carbon quality by measuring the major SOC fractions. Four nutrient regimes were compared: (i) control; (ii) chemical fertilizers only (CF), (iii) combined application of chemical fertilizers with farmyard manure (FYM) (CM), and (iv) combined application of chemical fertilizers and wheat straw (CS). Two soil water regimes included continuous waterlogging (CWL) and alternate wetting and drying (AWD). The total organic carbon (TOC) and total nitrogen (TN) in paddy soil were 40–60% and 37–67% higher in the combined organic sources and chemical fertilizers treatment against the sole chemical fertilizers treatment (CF), especially under continuous waterlogging (CWL). By fractionalizing SOC, it was observed that, under the water regimes of CWL, easily oxidizable carbon (EOC), particulate organic carbon (POC), light fraction organic carbon (LFOC), microbial biomass carbon (MBC), and mineralizable organic carbon (MNC) in the organically treated paddy soil were significantly ( P<0.05) lower, as compared with alternate wetting and drying (AWD). Especially for CM treatment, EOC, POC, LFOC, MBC, and MNC in the paddy soils under the regime of CWL were 23.5%, 32.7%, 16.3%, 56.8% and 25.1% lower than those by AWD, respectively. The proportions of EOC, POC, LFOC, MBC and MNC as a percent of TOC in the CWL were lower than those in the AWD, especially for the CM treatment. In the water regime of CWL, no significant differences were seen in the corresponding proportion of all the investigated organic fractions to soil total organic carbon (TOC) among the three fertilization treatments, whereas in the AWD, the corresponding proportions of different carbon fractions to TOC in the organic fertilizer treatments were significantly ( P<0.05) higher than those in the chemical fertilizer treatment. Under continuous waterlogging, the proportion of soil water stable aggregate >250 μm (WSA) decreased by 42–45% and clay dispersion ratio ( R CD) increased by 12–38%, as compared to the water regimes of AWD, when FYM or wheat straw was incorporated into paddy soil. Correlation analysis showed that, under the water regimes of AWD, WSA was significantly and positively related to EOC, LFOC and POC with the coefficients ( r) of 0.822, 0.889, 0.912 ( P<0.01), respectively. R CD was negatively correlated to EOC, LFOC and POC with the r=−0.796, −0.854, and −0.897 ( P<0.01), respectively, under AWD. Under the water regimes of CWL, there were no significant ( P<0.05) correlations between WSA as well as R CD and any organic carbon fraction except POC.

Determination of polychlorinated biphenyl congeners in sediment samples of twelve rivers in eastern China

Polychlorinated biphenyl (PCB) congener concentrations and their distributions were determined for the first time in 12 major rivers of eastern China. It was found that the PCB contamination level in those rivers was relatively low compared to the levels reported in most developing countries. Total amount of PCBs in the river sediments ranged from 10 to 22 ng/g dry weight and dichlorodiphenyldichloroethene (DDE) ranged from 0.89 to 7.62 ng/g. The PCB concentrations were basically homogeneous in different rivers; however, they consistently changed with the percent of total organic carbon (TOC). The PCB concentrations and compositions found in the 12 river sediments were very similar, with the tetra‐ and penta‐ groups as the dominants. Given that distributions and contaminant levels in sediments reflect the number of PCBs, the contamination of the 12 major rivers in eastern China is probably due to atmospheric deposition rather than the point source contamination.

Adsorption Equilibria of Natural Organic Matter After Ozonation

The equilibrium adsorption behavior of natural organic matter (NOM) subjected to coagulation and various levels of ozonation and biostabilization was investigated in bench‐scale experiments. The overall adsorbability of NOM increased with coagulation but decreased if coagulation was followed by ozonation and biostabilization. Without adsorption, ozonation was shown to enhance the biodegradability of coagulated NOM; up to 46 percent of total organic carbon was removed at the highest ozone dosage. The adsorption of NOM was described quantitatively by accounting for competitive adsorption among pseudocomponents and by applying concepts of polymer adsorption. Neither approach was entirely satisfactory for obtaining a systematic relationship between adsorbability and ozone dosage.