Residual Total Organic Carbon Research Articles

Treatment of Effluent Containing p-Cresol through an Advanced Oxidation Process in a Batch Reactor: Kinetic Optimization

The present research is related to the study of p-cresol oxidation reaction in aqueous phase. Firstly, the conventional advanced oxidation process (AOP) in a lab-scale batch reactor was used, seeking to identify the most impacting process variables and then to propose an optimization approach for ensuring the complete p-cresol degradation and the highest total organic carbon (TOC) conversion. In the AOP with the use of hydrogen peroxide as the oxidizing agent, the oxidation reaction was optimized with the aid of a factorial design, and a maximum TOC conversion of 63% was obtained. The Lumped Kinetic Model (LKM) was used to describe the profile of residual TOC concentration due to chemical species, which were categorized into two groups (refractory and non-refractory compounds). The model was able to satisfactorily describe the profile of the residual fractions of these two classes of organic compounds and allowed estimating the related kinetic constants (k) at two different temperatures, namely (a) 3.19 × 10−1 and 2.82 × 10−3 min−1 for non-refractory and refractory compounds at 80 °C and (b) 4.73 × 10−1 and 5.09 × 10−3 min−1 for the same compound classes at 90 °C, while the activation energy (Ea) of the process was 42.02 and 62.09 kJ mol−1, respectively. The kinetic modeling of organic pollutants oxidation in liquid effluents would allow to perform in situ seawater treatment on vertical reactors installed in offshore platforms and to properly release treated water into the oceans. In this way, ocean contamination caused by the exploration on offshore platforms of oil and natural gas, the main energy sources and vectors in the current world, may be remarkably reduced, thus favoring a more eco-friendly energy production.

Modeling the decomposition signal and correcting bulk organic data from a peat deposit, a case study at low latitudes (Cameroon)

Organic compounds are widely used for paleoclimatic and paleoenvironmental reconstructions. Bulk organic proxies, however, are more complicated to interpret due to the multiple causes of variation in climatic and environmental conditions and the degree of diagenetic alteration. As labile compounds, rich in easily degradable function and generally richer in heteroatoms such as oxygen and nitrogen, decompose, the remaining organic matter becomes progressively richer in refractory carbon and its carbon content increases. Thus, in a peat deposit composed almost entirely of organic matter, total organic carbon (TOC) is expected to increase with time and depth, which could mask the paleoclimatic signal. We propose a simple model for peat sediments to remove the decomposition signal based on a logarithmic function fitted with a partial dataset where decomposition is the main parameter. The subtraction of the obtained logarithmic function to the raw data (i.e., measured data) leads to “residual” data. We discuss the influence of different parameters (water table depth, vegetation, microbial community) on the “residual” data and their possible link to paleoclimatic and paleoenvironmental variations. This method is tested on bulk elemental and isotopic data obtained from a new peat core from the Adamawa Plateau (North-East Cameroon) covering nearly 10 ka cal BP. Comparison with Rock-Eval® parameters highlights similar variations between the Hydrogen Index and residual TOC variations, supporting the interpretation based on residual TOC. Our approach allows to extract paleoenvironmental information from decomposition-prone bulk organic proxies and can be generalized to peat deposits where decomposition plays a major role in controlling bulk data.

Characteristics and Significance of Acid-Soluble Organic Matter in Marine Carbonate Source Rocks

Since the 1950s, major breakthroughs have been made in the field of carbonate oil and gas exploration, and large reservoirs have been found in carbonate strata in many countries; however, the validity of highly evolved carbonate source rocks has been controversial. Because of the loss of organic carbon during acid-solution processing in conventional total organic carbon (TOC) determination, we decided to use a new method of reducing acid-solution losses in order to more effectively quantify acid-soluble organic matter in carbonate rock samples. Different levels of acid-soluble organic matter were present in different types of samples, and there was no positive correlation between the content of acid-soluble organic matter and conventionally measured TOC values. However, the thermal evolutionary maturity of samples with high acid-soluble organic matter content is relatively low, and the high hydrocarbon generation conversion rate of acid-soluble organic matter and conventional TOC in carbonate rocks is an important reason for the low residual TOC in highly evolved carbonate rocks. The new method is helpful in re-evaluating the abundance of organic matter in carbonate rocks and in providing evidence for studying hydrocarbon generation and the hydrocarbon capacity of carbonate source rocks.

Sedimentary Characteristics of the Permian Zhesi Formation in Eastern Inner Mongolia, China: Implications for Sedimentary Background and Shale Gas Resource Potential.

Eastern Inner Mongolia of China is located between the Siberian plate, the North China plate, and the Pacific plate and has a complex history of tectonic and sedimentary evolution. The sedimentary strata of the Zhesi Formation in the Middle Permian recorded rich environmental, structural, and petroleum geological information, which has great significance to the Paleozoic geological research in Northeast China. Through field outcrop observation and profile measurement, combined with geochemistry, mineralogy, and the reservoir physical property test, the sedimentary environment, tectonic setting, and shale gas resource potential of the Middle Permian Zhesi Formation are analyzed. The sedimentary facies of the Zhesi Formation are distributed in strips in the northeast direction, mainly developing littoral, shallow marine, and bathyal sedimentary environments. Clastic rock deposits are mainly developed in the littoral facies, carbonate platform and tempestite deposits are mainly developed in the shallow marine facies, and mudstone mixed with turbidite deposits are mainly developed in the bathyal facies. The sedimentary environment and chronological characteristics show that the Paleo-Asian Ocean was not completely closed in the Middle Permian, and its complete closure time should be later. The characteristics of source rocks and the shale gas resource potential in the Solon area are discussed. Controlled by the sedimentary environment, the Solon area mainly deposited thick dark shale mixed with turbidite sandstone, the accumulated thickness of the dark shale is more than 200 m, with an average vitrinite reflectance (Ro) of 2.44%, and the average residual total organic carbon (TOC) content is 0.85%. The average content of brittle minerals is 60.2% and the shale foliation fracture is developed, which is easy to form natural fractures and induced fractures, so the shale has good hydrocarbon generation potential, and the generated shale gas can exist in shale in an adsorbed state and a free state. In addition, the shale gas generated in the shale can migrate to the lenticular turbidite sand body in a short distance to form free shale gas. Therefore, there is a certain shale gas resource potential in the Solon area, and finding a favorable area with high TOC is the key to future exploration of Upper Paleozoic shale gas.

Biological activated carbon filter for greywater post-treatment: Long-term TOC removal with adsorption and biodegradation

Biological activated carbon (BAC) filters can be used to remove residual total organic carbon (TOC) from greywater after a membrane bioreactor. The two main TOC removal processes are adsorption to the granular activated carbon (GAC) and biological degradation. Biodegradation leads to the growth of microorganisms in the filter bed, which can lead to increased pressure loss over the filter bed. However, the roles of sorption and biodegradation in long-term TOC removal and how they complement each other are unclear. We monitored TOC removal from greywater in a BAC filter installed following a membrane bioreactor over more than 900 days. Removal performance depended on the operational time of the BAC filter, the influent TOC concentration, and in the upper part of the filter on the empty bed contact time (EBCT). Across the overall filter, the EBCT did not significantly influence TOC removal, showing that the filter was sufficiently large for the range of flow rates observed. Analysis of the long-term data revealed the equal importance of sorption and biodegradation over the whole operation period and the whole filter bed. Most of the TOC was removed in the upper part of the filter, where biodegradation was the dominant mechanism. In the lower part of the filter, sorption capacity remained and allowed high influent TOC concentrations to be buffered. The generous filter design with low average filtration rates ensured long-term TOC removal. The only maintenance needed was backwashing, which was required only after more than 800 days of operation. Backwashing effectively reduced the pressure loss but had no significant influence on the effluent water quality. Our study shows that BAC filters are a suitable post-treatment step for the treatment of greywater with highly variable flow and TOC concentrations.

Experimental Simulation of Hydrocarbon Expulsion in Semi-open Systems from Variable Organic Richness Source Rocks

To better understand oil and gas generation and expulsion mechanisms and their controlling factors, two-stage heating program (20 and 5 °C/d) at 11 target temperatures (250–580 °C) have been performed in a semi-open reactor on nine immature lacustrine shale samples from the Triassic Yanchang Formation in Ordos Basin, NW China, with total organic carbon (TOC) contents ranging from 0.5% to 30.0%. The cumulative expelled oil and gas were quantified and correlated with the measured vitrinite reflectance (%Ro) and residual TOC. The amount of expelled oil increases substantially with increasing maturity in the Ro range of 0.5–1.25% and ends at Ro of >1.45%, while the volume of expelled gas increases markedly with maturity when Ro is >1.0%. Organic richness exerts primary control on the expulsion yields, which increase linearly with increasing original TOC (TOCo) per unit weight of rock, whereas the increment decreases with TOCo per unit weight of TOC, once the TOCo content is above 5%. Marked TOC reduction occurs in the Ro of 0.5–1.1% due to oil generation and expulsion, but the trend is reversed in the higher maturity range possibly caused by the simultaneous decomposition of minerals. Numerical correlations among heating temperatures, %Ro, TOC content, and expelled oil and gas yields have been constructed, and the minimum TOC contents for effective oil and gas source rocks have been inferred. The lowest TOC contents of 0.5% and 0.48% are required for oil and gas expulsion in the oil and gas generation window, corresponding to the TOCo of 0.91% and 0.76%, respectively. The minimum TOC content for effective gas source rocks decreases slightly with increasing maturity; however, a much higher TOC cutoff is required for lower maturity level source rocks. Wide range of TOC content variation in our studied samples provides well constraint of organic richness on oil and gas generation and expulsion behaviors and their evolution trajectory during thermal evolution, which will fascinate source rock quality and exploration potential assessment in other source rock systems.

Catalytic activation of PS/PMS over Fe-Co bimetallic oxides for phenol oxidation under alkaline conditions

In this study, we compared the differences between bimetallic oxides FeCo2O4 catalyzing the oxidation of phenol by peroxydisulfate (PS) and peroxymonosulfate (PMS) under near neutral and alkaline conditions. Phenol could be completely oxidized and removed in both PMS and PS systems. X-ray photoelectron spectroscopy (XPS) analysis and density functional theory (DFT) calculations showed that there was a synergistic mechanism between Co and Fe on the catalyst surface. Although the PMS-FeCo2O4 system reached the fastest reaction rate of 1.5 × 10−1 min−1, it showed a higher oxidants consumption and more residual total organic carbon (TOC) (36%) in solutions after reactions. Quenching experiments and electron paramagnetic resonance (EPR) analysis showed that sulfate radical (SO4−), hydroxyl radical (OH) and singlet oxygen (1O2) played important roles in the oxidation of phenol in PMS system. While in the PS-FeCo2O4 system, in addition to free radical reactions, the non-radical mechanisms between PS and the catalyst surface played a major role in phenol oxidation, and the soluble organic matter in the PS system could be completely removed. Thus, PS has a better application prospect in the treatment of phenol. This discovery has certain guiding significance for catalyst modification and doping to improve catalyst activity and the choice of oxidant.

Reactive electrochemical membrane for the elimination of carbamazepine in secondary effluent from wastewater treatment plant

This study evaluated the feasibility of the electrooxidation process using a sub-stoichiometric titanium oxides (TiOX) reactive electrochemical membrane (REM) as anode for the treatment of a secondary effluent from a wastewater treatment plant. The main objectives were to analyze (i) the degradation of a pharmaceutical pollutant, carbamazepine, added at a concentration of 100 µg L−1, (ii) the mineralization of the residual total organic carbon (TOC = 7 mg L−1), (iii) the formation of toxic by-products and (iv) the energy consumption of the REM process. Two main operating parameters were tested: the current density applied to the REM (74, 149 and 290 A m−2) and the flux of TOC passing through the membrane. The results revealed that the efficiency of the process was maintained above 70% of mineralization and >98% of degradation of carbamazepine until a limiting value of TOC flux was reached. The higher the current density, the higher the limiting value of the TOC flux above which the efficiency decreased. This trend was ascribed to the limitation from the amount of reactive species produced on the REM surface (current limitation instead of mass transport limitation at lower TOC flux). As the energy efficiency strongly increased when applying a higher TOC flux, it is therefore crucial to apply the process around this threshold value. This study also showed that it is possible to control the formation of toxic chlorine-containing by-products (ClO3−, ClO4−, AOCl) by decreasing the current density. This issue is particularly important for such effluents containing a significant amount of Cl− ions. By taking into consideration both advantages and drawbacks, optimal results were obtained with the lowest current density of 73 A m−2 and a TOC flux through the membrane of 4.41 g h−1 m−2 corresponding to 1.34 m3 h−1 m−2. These conditions allowed for >98% degradation of carbamazepine and 70% of mineralization with an energy consumption of 0.15 kWh g−1 of TOC removed (i.e. 0.74 kWh m−3 of treated wastewater).

Production of Poly(3-hydroxybutyrate) (P(3HB)) from Different Agroindustry Byproducts by Bacillus megaterium

The use of plastics, replacing materials such as paper and glass, has become a staple of modern society. A possible alternative is the production of biopolymers, in which case polyhydroxyalkanoates (PHAs) tend to be the most studied class. Among the PHAs, poly(3-hydroxybutyrate) (P(3HB)) is one of the most studied. Bacillus megaterium can utilize a wide range of carbon sources to produce P(3HB) and display high resistance to osmotic pressure and temperature. There are few studies regarding the viability of confectionery wastewater (CWW) and rice parboiling water (RPW) in PHA production; however, data suggests they might be successfully used as culture media for microorganisms. Cultures of B. megaterium were conducted under a 22-factorial design of experiments with different agitation and airflow conditions using mineral medium added with CWW and RPW. Under maximized conditions, it was possible to obtain 7.55 g/L of dry cell biomass, with 50.1% P(3HB) content (3.78 g/L). Kinetic parameters of the maximized culture were also assessed, with the highest productivity (0.146 g/L·h) being found after 20 h of culture. Results found in the tests indicate that CWW and RPW can be used as culture media in P(3HB) production; however further studies are necessary to fully optimize the process, as well as to find alternatives to reduce the amount of residual total organic carbon (TOC) still present in the cultures.

Removal of polyethylene glycols from wastewater: A comparison of different approaches

Physicochemical methods such as adsorption on activated carbon, oxidation with either ozone or Fenton reagent, and chemical precipitation (coagulation), were assessed for the removal of polyethylene glycol (PEG) from wastewater. This contaminant is rarely investigated due to its low toxicity, although its presence limits the use of large water resources. The experimental tests showed that adsorption on activated carbon is well approximated by a Langmuir isotherm, and influenced by contact time, PEG molecular weight, pH, temperature, and initial PEG concentration. Ozonation allowed fragmenting the polymeric chains but was unable to remove completely the PEG, while about 85% of the total organic carbon (TOC) was removed by Fenton oxidation reaction by using a ratio between H2O2 and FeII close to 4. Coagulation did not produce results worthy of note, most likely because the uncharged PEG molecule does not interact with the iron hydroxide flocs. However, when performed after the Fenton oxidation (i.e., by simply raising the pH to values > 8), it allowed a further reduction of the residual TOC, up to 96% of the total, in the best case. Based on the resources used by each process studied and in consideration of the effectiveness of each of them, a semi-quantitative comparison on the sustainability of the different approaches is proposed.

Slaughterhouse Wastewater Treatment By Anodic Oxidation Using Two Different DSA-Type Anodes

Water is an essential resource for life, the environment and the industrial development; hence the treatment of wastewater has become crucial to ensure a good quality effluent before disposal the municipal sewer systems. The slaughterhouse industry produces a large volume of wastewater due to the slaughtering of animals, meat processing and the cleaning of the slaughterhouse facilities [1]. Treatment and adequate disposal of slaughterhouse wastewater (SW) is a worldwide economy and public health necessity which is regulated by International Standard [2]. SW contains elevated amounts of organic matter and salts. Typical parametrical analyses include pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen (TN), total phosphorous (TP), total organic carbon (TOC) and total suspended solids (TSS) [3]. After preliminary treatment, where most large particles are removed, the coagulation-flocculation technology is the most used primary treatment. However, it produces secondary pollution. Nowadays, electrochemical processes such anodic oxidation (AO) have been considered an alternative technology for the treatment of SW due to its mild operation conditions, quite compact and easy operation and not secondary waste streams among others. AO may oxidize the organic pollutants via two different ways: i) directly oxidized, where electron transfer occurs at the anode surface (M) and/or ii) indirectly oxidized, where the organic pollutants are oxidized through the mediation of some species electro-generated in situ at the anode surface and/or agents in the bulk solution.In this study, a real beef slaughterhouse wastewater presented the following characteristics: TOC (1150 mg L–1), COD (4320 mg L–1), TP (25 mg L–1), TN (72.28 mg L–1), TSS (1433 mg L–1) at pH 7.18 and conductivity of 2.79 mS cm–1. Bright red color was observed at 416 nm (1.24 A.U.) and the presence of coliform bacteria was confirmed (> 1600 MPN). AO tests were carried out in a single open cell compartment in batch operation mode. 0.1 L of SW was introduced into the electrolytic cell with constant stirring to ensure mass transport of the oxidant specie towards/from the anode to the bulk. AO was assessed using two different dimensionally stable anodes (DSA) type anodes: i) Ti/IrO2/Ta2O5 coating (DSA-O2) ii) Ti/Ru0,3Ti0,7O2 (DSA-Cl2). AISI 304 stainless steel plate was used as cathode. The geometrical bare area of both, cathode and anode, was about 5 cm2, having a 1 cm of interelectrode gap. AO experiments were analyzed at different applied current densities (2, 10 and 20 mA cm–2) and supporting electrolyte (0.05 M Na2SO4; 0.05 M NaCl) in order to find the best operating conditions.This study focuses on TOC and COD removal as a function of the current density and the electrolysis time. Minimizing TOC and COD values is the main objective in SW treatment. However, TOC is the most important role to determine the organic compounds in SW. Figure 1 shows the TOC removal during five hours of electrochemical treatment utilizing the two different DSA-type anodes at the higher current density (j = 20 mA cm–2). As can be seen in Figure 1a), EO process using DSA-O2 without supporting electrolyte reached the maximum removal of total organic carbon at the end of the electrolysis time. Residual TOC concentration achieved 232.66 mg L–1 (79.77 % removal efficiency). Figure 1b) displays the TOC abatement from SW using DSA-Cl2 anode. Alike the DSA-O2 the best EO test was the one where not supporting electrolyte was added, the maximum TOC removal efficiency reached 78.62 % (245.89 mg L–1) unlike the other tests using supporting electrolyte.The best operating conditions were found at current density of 20 mA cm–2 without supporting electrolyte. TOC, COD and TP removal efficiency were 79.77% and 78.62 %; 89.22% and 79.4%; 96.0% and 64% using DSA-Cl2 (Ti/Ru0,3Ti0,7O2) and DSA-O2 (Ti/IrO2/Ta2O5), respectively. Moreover, a complete discoloration and disinfection were achieved. Electrochemical oxidation test at best operating conditions gave energy consumption and specific energy consumption values for TOC, COD and TP using DSA-Cl2 and DSA-O2 of 24.5 and 26.5 kW h m–3, 27.1 and 28.9 kW h kgTOC –1, 7.14 and 6.88 kW h kgCOD –1 and, 1531.25 and 1104.17 kW h kgTP –1, respectively.[1] Bustillo-Lecompte C.F., Mehrvar M., 2015. J. Environ. Manag. 161 287–302.[2] US Environmental Protection Agency. Final Rule; Federal Register. 2004;69(173):54476–54555.[3] Bustillo-Lecompte, C.F., Mehrvar, M., 2017. J. Clean. Prod. 141, 278–289. Figure 1

Catalytic ozonation of textile wastewater as a polishing step after industrial scale electrocoagulation

The main objective of this study was to develop the treatment system to change wastewater into a reliable source of recyclable water within the textile plant. Therefore, a highly polluted industrial wastewater originated in the dyeing of cotton was subjected to a multi-step treatment. The raw wastewater was characterized by the concentration of Reactive Black 5, the azo dye, as high as 842 mg/L, extreme alkalinity (pH 11.26) and salinity (NaCl concentration 52,290 mg/L). Correspondingly, the chemical oxygen demand (COD) was equal to 3440 mg/L and the total organic carbon (TOC) was 1790 mg/L in this wastewater. This salty, hardly degradable wastewater underwent the electrocoagulation (EC) on an industrial scale in the first step of the treatment. Although the industrial EC resulted in 84% of color removal in a very short time of 8 min, the wastewater was still characterized by an extremally high absorbance which corresponded to 100 mg/L of RB5. Moreover, EC resulted in the occurrence of burdensome by-products, of which one was identified in this study as an aniline derivative. The by-products contributed to high residual COD and TOC after EC (2120 mg/L and 1052 mg/L, respectively). Consequently, the catalytic ozonation was used by us as a second, the polishing, step of the treatment. The catalytic ozonation was found efficient in the removal of the residual color and colorless by-products. The wastewater after catalytic ozonation was colorless and the final COD and TOC decreased to 1283 and 695 mg/L, respectively. The average oxidation state (AOS), spectra analysis, and the toxicity assay showed catalytic ozonation efficient in the by-products oxidation. Consequently, the catalytic action of activated carbon (AC) was proved for the ozonation of textile wastewater. Ultimately, the recycling of purified wastewater into dyeing resulted in a very good color quality of textile samples (DECMC values below limiting value equal to 1.0).

Extended Fenton's process: toward improving biodegradability of drilling wastewater.

In this study, an extended Fenton process was used to improve biodegradability of the waste drilling mud containing bio-refractory polymers. Variation of biodegradability and organics with different molecular weights with the oxidation time were investigated during the Fenton oxidation process. Although the residual total organic carbon (TOC) arrived at a stable level soon after oxidation reaction, organics with the lower molecular weight increased and its biodegradability was improved significantly in the extended oxidation process, which originated from decomposition of residual H2O2 catalyzed by transformation of the Fe3+/Fe2+ and organoradicals. Under the conditions that follow: pH 3.0, H2O2 500 mg L-1, Fe2+ 250 mg L-1, oxidation time 120 min, further TOC removal of 35.9% and biochemical oxygen demand and total organic carbon (BOD/TOC) ratio of 0.83 was achieved. At the biological test, a substantial increase in TOC degradation by biological treatment with extension of Fenton oxidation time was observed. Finally, more than 90% biological removal of the TOC was achieved for the 120 min oxidation treatment. The experimental results highlight that an extended process can be adopted to improve the biodegradability of wastewater by utilization of the slow reaction of hydrogen peroxide with Fe3+ and organoradicals.

Reductive recovery of manganese from low-grade manganese dioxide ore using toxic nitrocellulose acid wastewater as reductant

The hydrometallurgical strategy of extracting Mn from low-grade Mn ores has attracted attention for the production of electrolytic manganese metal (EMM). In this work, the reductive dissolution of low-grade MnO2 ores using toxic nitrocellulose acidic wastewater (NAW) as a reductant was investigated for the first time. Under the optimized conditions of an MnO2 ore dosage of 100 g·L−1, an ore particle size of −200 mesh, concentrated H2SO4-to-NAW volume ratio of 0.12, reaction temperature of 90°C, stirring speed at 160 r·min−1, and a contact time of 120 min, the reductive leaching efficiency of Mn and the total organic carbon (TOC) removal efficiency of NAW reached 97.4% and 98.5%, respectively. The residual TOC of 31.6 mg·L−1 did not adversely affect the preparation of EMM. The current process offers a feasible route for the concurrent realization of the reductive leaching of Mn and the treatment of toxic wastewater via a simple one-step process.

Pilot scale application of UV-C/H 2 O 2 for removal of chlorinated ethenes from contaminated groundwater

A field pilot scale UV-C/H 2 O 2 system investigated for treatment of groundwater contaminated with chlorinated ethenes is presented in this study. Groundwater contamination was mainly represented by trichloroethylene and tetrachloroethylene. The pilot scale unit was set up and its suitability was verified during a testing campaign on site. The results of oxidation tests revealed high efficiency in chlorinated ethenes9 removal together with significant decrease of residual total organic carbon content. The presented results emerged from previous unit optimization. Also, economical evaluation of the process is presented.

Evaluation of degradation and kinetics parameters of acid orange 7 through wet air oxidation process

AbstractAmong the industrial effluents presenting constraints to traditional biological treatments, those from textile industries are of particular concern. Wet air oxidation is an effective process that significantly increases biodegradability of the treated effluent. In this study, the advantage of this process was tested for the treatment of acid orange 7, a dye molecule used as a model textile effluent. Different experimental conditions of temperature (200 to 300 °C) and duration of treatment were used to determine its degradation yield during the wet air oxidation process, at a total pressure of 30 MPa. All these conditions led to complete degradation of acid orange 7, but residual Total Organic Carbon always remained. Oxidation byproducts were identified by the means of GC and HPLC analyses. Acetic acid remains the major compound not oxidized. These experiments resulted in the proposal of a reaction scheme associated with kinetic constants. Finally, the optimal conditions for the improvement of the biodegradability of the effluent were determined. This wet air oxidation process could then be coupled with a biological treatment to obtain an overall degradation meeting the criteria for release into the environment.

Removal of organochlorine pesticides from lindane production wastes by electrochemical oxidation.

This study is focused on the effective removal of recalcitrant pollutants hexaclorocyclohexanes (HCHs, isomers α, β, γ, and δ) and chlorobenzenes (CBs) present in a real groundwater coming from a landfill of an old lindane factory. Groundwater is characterized by a total organic carbon (TOC) content of 9mgL-1, pH0 = 7, conductivity = 3.7mScm-1, high salt concentration (SO42-, HCO3-, Cl-), and ferrous iron in solution. The experiments were performed using a BDD anode and a carbon felt (CF) cathode at the natural groundwater pH and without addition of supporting electrolyte. The complete depletion of the four HCH isomers and a mineralization degree of 90% were reached at 4-h electrolysis with a current intensity of 400mA, the residual TOC (0.8mgL-1) corresponding mainly to formic acid. A parallel series reaction pathway was proposed: HCHs and CBs are transformed into chlorinated and hydroxylated intermediates that are rapidly oxidized to non-toxic carboxylic acids and/or mineralized, leading to a rapid decrease in solution pH.

Discrimination of effective source rocks and evaluation of the hydrocarbon resource potential in Marsel, Kazakhstan

Three rounds of exploration in Marsel, Kazakhstan show that the area has good petroleum geological conditions; however, the exploration degree is low and the resource potential is unclear. The total organic carbon (TOC) content is the criteria for effective source rocks and is also the key parameter to calculate the amount of resources; while previous evaluations of the effective source rocks and calculated amounts of resources were based on residual TOC, which gradually decreases with mass hydrocarbon expulsion; therefore, this will inevitably produce errors. For greater accuracy, the TOC recovery coefficient formula was used to recover the residual TOC in Marsel; then, the criteria of the effective source rocks were revised to calculate the Carboniferous and Devonian resources in Marsel. The results are as follows: for the source rocks in Marsel, the TOC recovery coefficient of the Carboniferous source rocks is approximately 1.6, while that for the Devonian is approximately 2.0; the revised lower limit of TOC for the effective source rocks is 0.3% and 0.25% for the Carboniferous and Devonian, respectively; after TOC recovery, the total amount of hydrocarbon expulsion is 26.7 × 1012 m3, the total amount of recoverable resources is 2.62–5.10 × 1012 m3, and the mean is 3.79 × 1012 m3 for the main source rocks. The effective source rocks evaluated based on the recovered TOC and the latter resources could reflect the quantity of source rocks and actual resource potential of Marsel more accurately. This has certain significance for the exploration of areas that have low levels of exploration with an unclear understanding of the resource potential as well as a high degree of thermal evolution and a low quantity of residual TOC.

Depositional environment and geochemical characteristics of the Lower Carboniferous source rocks in the Marsel area, Chu-Sarysu Basin, Southern Kazakhstan

There are two sets of carbonate source rocks in the Lower Carboniferous layers in Marsel: the Visean (C1v) and Serpukhovian (C1sr). However, their geochemical and geological characteristics have not been studied systematically. To assess the source rocks and reveal the hydrocarbon generation potential, the depositional paleoenvironment and distribution of C1v and C1sr source rocks were studied using total organic carbon (TOC) content, Rock-Eval pyrolysis and vitrinite reflectance (Ro) data, stable carbon isotope data, gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analysis data. The data were then compared with well logging data to understand the distribution of high-quality source rocks. The data were also incorporated into basin models to reveal the burial and thermal histories and timing of hydrocarbon generation. The results illustrated that the average residual TOC contents of C1v and C1sr were 0.79% and 0.5%, respectively, which were higher than the threshold of effective carbonate source rocks. Dominated by type-III kerogen, the C1v and C1sr source rocks tended to be gas-bearing. The two source rocks were generally mature to highly mature; the average Ro was 1.51% and 1.23% in C1v and C1sr, respectively. The source rocks were deposited in strongly reducing to weakly oxidizing marine–terrigenous environments, with most organic material originating from higher terrigenous plants and a few aquatic organisms. During the Permian, the deep burial depth and high heat flow caused a quick and high maturation of the source rocks, which were subsequently uplifted and eroded, stopping the generation and expulsion of hydrocarbons in the C1v and C1sr source rocks. The initial TOC fitted by the △logR method was recovered, and it suggests that high-quality source rocks (TOC ≥ 1%) are mainly distributed in the northern and central local structural belt.

Depositional environment and organic matter accumulation of Upper Ordovician–Lower Silurian marine shale in the Upper Yangtze Platform, South China

The main controlling factors of organic matter accumulation in the Upper Ordovician Wufeng–Lower Silurian Longmaxi Formations are complex and remain highly controversial. This study investigates the vertical variation of total organic carbon (TOC) content as well as major and trace element concentrations of four Ordovician–Silurian transition sections from the Upper Yangtze Platform of South China to reconstruct the paleoenvironment of these deposits and to improve our understanding of those factors that have influenced organic matter accumulation in these deposits.The residual TOC content of the Wufeng Formation averages 3.2% and ranges from 0.12 to 6.0%. The overlying lower Longmaxi Formation displays higher TOC content (avg. 4.4%), followed upsection by consistent and lower values that average 1.6% in the upper Longmaxi Formation. The concentration and covariation of redox-sensitive trace elements (Mo, U and V) suggest that organic-rich intervals of the Wufeng Formation accumulated under predominantly anoxic conditions. Organic-rich horizons of the lower Longmaxi Formation were deposited under strongly anoxic to euxinic conditions, whereas organic-poor intervals of the upper Longmaxi Formation accumulated under suboxic conditions. Positive correlations between redox proxies and TOC contents suggest that organic matter accumulation was predominantly controlled by preservation. Barium excess (Baxs) values indicate high paleoproductivity throughout the entire depositional sequence, with an increase in the lower Longmaxi Formation. Increased productivity may have been induced by enhanced P recycling, as evidenced by elevated Corg/Ptot ratios. Mo–U covariation and Mo/TOC values reveal that the Wufeng Formation was deposited under extremely restricted conditions, whereas the Longmaxi Formation accumulated under moderately restricted conditions. During the Late Ordovician, the extremely restricted nature of ocean circulation on the Upper Yangtze Platform in tandem with enhanced stratification of the water column promoted anoxic conditions favorable for the preservation of organic matter. During Early Silurian time, organic matter accumulation was principally controlled by changes in sea level, which affected terrigenous flux, redox conditions, and the degree of nutrition recycling.