Aqueous Organic Matter Research Articles

Synergistic Catalysis of Water-Soluble Exogenous Catalysts and Reservoir Minerals during the Aquathermolysis of Heavy Oil.

Oil serves as the essential fuel and economic foundation of contemporary industry. However, the use of traditional light crude oil has exceeded its supply, making it challenging to meet the energy needs of humanity. Consequently, the extraction of heavy oil has become crucial in addressing this demand. This research focuses on the synthesis of several water-soluble catalysts that can work along with reservoir minerals to catalyze the hydrothermal cracking process of heavy oil. The goal is to effectively reduce the viscosity of heavy oil and lower the cost of its extraction. Based on the experimental findings, it was observed that when oil sample 1 underwent hydrothermal cracking at a temperature of 180 °C for a duration of 4 h, the amount of water added and catalyst used were 30% and 0.2% of the oil sample dosage, respectively. It was further discovered that the synthesized Mn(II)C was able to reduce the viscosity of oil sample 1 by 50.38%. The investigation revealed that the combination of Mn(II)C + K exhibited a significant synergistic catalytic impact on reducing viscosity. Initially, the viscosity reduction rate was 50.38%, which climbed to 61.02%. Subsequently, when catalyzed by the hydrogen supply agent isopropanol, the rate of viscosity reduction rose further to 91.22%. Several methods, such as freezing point analysis, thermogravimetric analysis, DSC analysis, component analysis, gas chromatography, wax crystal morphology analysis, and GC-MS analysis, were conducted on aqueous organic matter derived from heavy oil after undergoing different reaction systems. These analyses confirmed that the viscosity of the heavy oil was decreased. By studying the reaction mechanism of the model compound and analyzing the aqueous phase, the reaction largely involves depolymerization between macromolecules, breakdown of heteroatom chains, hydrogenation, ring opening, and other related consequences. These actions diminish the strength of the van der Waals force and hydrogen bond in the recombinant interval, impede the creation of a grid-like structure in heavy oil, and efficiently decrease its viscosity.

Oil-Soluble Exogenous Catalysts and Reservoir Minerals Synergistically Catalyze the Aquathermolysis of Heavy Oil.

Oil is the "blood" and economic lifeblood of modern industry, but traditional light crude oil has been over-consumed, and it has been difficult to meet human demand for energy, so the exploitation of heavy oil is particularly important. In this paper, an oil-soluble catalyst was synthesized to catalyze the pyrolysis reaction of heavy oil in collaboration with reservoir minerals, so as to achieve efficient viscosity reduction of heavy oil and reduce production costs. The experimental results showed that Zn(II)O + K had the best synergistic viscosity reduction effect after the aquathermolysis of No. 1 oil sample under the reaction conditions of 180 °C, 4 h, 30% of water, and 0.2% of catalyst, respectively, and the viscosity reduction rate was 61.74%. Under the catalysis of the isopropanol system, the viscosity reduction rate was increased to 91.22%. A series of characterizations such as freezing point, thermogravimetric analysis, DSC analysis, component analysis, gas chromatography, wax crystal morphology analysis, and GC-MS analysis of aqueous organic matter were carried out on heavy oil after reaction by different reaction systems, and it could be verified that the viscosity of heavy oil was reduced. Finally, through the study of the reaction mechanism of the model compound, combined with the aqueous phase analysis, it can be clearly found that the depolymerization between macromolecules, the breaking of heteroatom chains, hydrogenation, ring opening, and other effects mainly occur during the reaction, thereby weakening the van der Waals force and hydrogen bond of the recombinant interval, inhibiting the formation of grid structure in heavy oil and effectively reducing the viscosity of heavy oil.

Electrochemical activation of hydrogen peroxide, persulfate, and free chlorine using sacrificial iron anodes for decentralized wastewater treatment

Increasing contamination of groundwater by heavy metals could potentially hamper the basic sanitation based on septic system in developing countries. Therefore, this paper evaluated wastewater treatment by electrochemical activation of hydrogen peroxide (EAHP), persulfate (EAP), and free chlorine (EAFC) to simultaneously eliminate aqueous organic matter and heavy metals. Sacrificial iron anodes under galvanostatic regime activated the batch-injected oxidants under uncontrolled pH, to avoid extra cost of control in decentralized processes (e.g., household use) to treat domestic wastewater. Response surface methodology (RSM) was used to determine the optimized conditions for EAP ([persulfate]0 = 25 mM, 24.4 mA/cm2), EAFC ([free chlorine]0 = 35.5 mM, 44.4 mA/cm2), and EAHP ([H2O2]0 = 91.1 mM, 45 mA/cm2) towards total organic carbon (TOC) removal. Treatment of real wastewater under optimum conditions significantly reduced chemical oxygen demand (COD) and TOC in all treatments, complying with lenient effluent standards as well as the added benefit of complete As(V) and Cr(VI) removal. Although EAP and EAFC provided superior removal of TOC (70−75%) and COD (73–100%) within 3 h, respectively, effluent toxicity and operation cost (76–85 USD/m3) were relatively high. EAHP was the best available option to secure non-toxic effluent with the least cost (63 USD/m3).

Greenhouse gases in an urban river: Trend, isotopic evidence for underlying processes, and the impact of in-river structures

Urban rivers are important sources of greenhouse gases (GHGs) to the atmosphere; however, these high dissolved GHGs are not well studied. We report the first detailed investigation on an urban river influenced by wastewater treatment plant (WWTP), dam and aeration device, with a focus on the concentration of GHGs and their underlying microbial processes basing on isotope approaches. The result revealed that these infrastructures influenced carbon and/or nitrogen input and redox condition of the river system, leading to impaction of GHGs concentrations and spatiotemporal pattern. The WWTP effluent was the point-source of N2O loading to rivers, and also contained high NO3– and dissolved organic carbon, creating favorable conditions for denitrification by microbes. We measured isotopic compositions (δ15N-N2O and δ18O-N2O) and site preference (SP) of dissolved N2O to differentiate the relative contribution of N2O production processes and calculate the degree of N2O reduction (Fr). The relative contribution of denitrification increased at downstream and Fr suggested that N2O was produced and consumed by heterotrophic denitrification, resulting in a sink of N2O downstream. The closure of dam increased water residence time, trapped the sediment, accelerated oxygen consumption, and development of anoxic conditions that stimulating the production of CO2 and CH4, as well as consumption of N2O. Aeration devices maintained oxic condition, that slowing the development of the anoxic stage and eliminating the methanic stage at downstream. As a result, CO2 concentrations increased along the river due to production of CO2 via anaerobic and aerobic respiration of aqueous organic matter. CH4 concentrations increased at downstream from organic matter biodegradation under anoxic conditions. The measured dissolved GHGs, especially the upper ranges, correspond to a large oversaturation of surface water with respect to atmospheric equilibrium, leading high fluxes to the atmosphere. Our values are on the high end of estimates reported in the literature among different climate regions, indicating that urban river influenced by various of infrastructures are comparable to those in wetlands and intensively agricultural rivers in terms of GHGs emissions. Urban river should be urgently included in the determination of global carbon and nitrogen budgets from rivers.

Five decades of declining methylmercury concentrations in boreal foodwebs suggest pivotal role for sulphate deposition

Widespread declines in mercury (Hg) in fish in pristine lakes in Fennoscandia since the 1970s are unexplained. Interactions between climate, atmospheric deposition, and elemental cycling of carbon (C), sulphur (S) and Hg are complex and affect Hg bioaccumulation. A parallel significant decline in methyl-Hg (MeHg) concentrations in aquatic macroinvertebrates (Chironomidae) was found between 1976–78 and 2004–15 in an intensely studied, pristine boreal lake (Langtjern, boreal Fennoscandia). Monitoring at Langtjern demonstrated a four-fold decrease in aqueous sulphate concentrations (SO4, 50-year record), significant lake browning (30-year records), increasing sediment Hg concentrations (50-year record), warming (45-year record) and increased runoff (40-year record). Contrasting Hg trends in biota (downward) and sediment (upward) indicated a disconnect between lake Hg loading and foodweb Hg bioaccumulation. We suggest that reduced SO4-deposition has 1) constrained substrate availability for SO4-reducing methylating bacteria (causing reduced foodweb MeHg exposure despite increased Hg loading to the lake), and 2), increased the binding affinity between aqueous organic matter and Hg species (leading to reduced MeHg bioavailability). The downward MeHg trend at the base of the foodweb at Langtjern is mirrored at higher trophic levels by strong declines in perch (Perca fluviatilis) and pike (Esox lucius) Hg concentrations in boreal Fennoscandia. A plausible explanation is that declining SO4-deposition, rather than climate change or reduced atmospheric Hg, is currently driving reduced MeHg contamination in northern freshwater foodwebs.

Effect of ozonation of swimming pool water on formation of volatile disinfection by-products – A laboratory study

Ozonation experiments were performed using unchlorinated tap water used for filling municipal swimming pools, actual pool water and pool water polluted by addition of fresh tap water and artificial body fluid to evaluate ozone kinetics and water quality effects on formation of volatile disinfection byproducts during subsequent chlorination.The ozone reaction was observed to behave according to first order kinetics. For tap water half-life was 4min whilst polluted and unpolluted pool water exhibited half-life of 8 and 11min, respectively. When ozonation dosage was repeated half-life of ozone was approximated 17–19min in all samples.Subsequent chlorination revealed ozone removed reactivity of dissolved organic carbon toward chlorine for tap and polluted pool water, decreasing formation rate of trihalomethanes (TTHM). In pool water higher rates of TTHM formation was observed after the initial ozone dosage, however this decreased with subsequent treatments. For tap and polluted pool water, ozone reacted directly with the pollutants resulting in a short ozone half-life, removing reactivity towards chlorine oxidation and preventing TTHM production. Conversely for pool water samples, due to the long half-life of ozone, the molecule decomposed to hydroxyl radicals. These in turn reacted with aqueous organic matter increasing chlorine reactivity and rates of TTHM formation. Formation of other non-regulated volatile byproducts (e.g. dichloracetonitrile, trichlorpropanone and trichloronitromethane) was observed to increase in pool water with ozone treatment. Thus, ozonation dosage regimes should be designed such that ozone mostly oxidizes fresh pollutants before chlorine is able to react with it.

Effect of organic matter on CO(2) hydrate phase equilibrium in phyllosilicate suspensions.

In this study, we examined various CO2 hydrate phase equilibria under diverse, heterogeneous conditions, to provide basic knowledge for successful ocean CO2 sequestration in offshore marine sediments. We investigated the effect of geochemical factors on CO2 hydrate phase equilibrium. The three-phase (liquid-hydrate-vapor) equilibrium of CO2 hydrate in the presence of (i) organic matter (glycine, glucose, and urea), (ii) phyllosilicates [illite, kaolinite, and Na-montmorillonite (Na-MMT)], and (iii) mixtures of them was measured in the ranges of 274.5-277.0 K and 14-22 bar. Organic matter inhibited the phase equilibrium of CO2 hydrate by association with water molecules. The inhibition effect decreased in the order: urea < glycine < glucose. Illite and kaolinite (unexpandable clays) barely affected the CO2 hydrate phase equilibrium, while Na-MMT (expandable clay) affected the phase equilibrium because of its interlayer cations. The CO2 hydrate equilibrium conditions, in the illite and kaolinite suspensions with organic matter, were very similar to those in the aqueous organic matter solutions. However, the equilibrium condition in the Na-MMT suspension with organic matter changed because of reduction of its inhibition effect by intercalated organic matter associated with cations in the Na-MMT interlayer.

Odour Problems in Potable Water and its Treatment Options: a Review

Odours in potable waters are the major complaint repeated by customers worldwide. Water utilities have justified or ignored them, because, in most cases, the odorous waters satisfy all of the water laws and registration requirements. For customers however, odour is often the primary judgement of water quality. Odour problems are usually caused by Aqueous Organic Matter (AOM). Furthermore, the AOM can be produced as unexpected by-products (e.g. disinfection by-products) during water treatment processes. Hence, eliminating AOM during water treatment is one of the highest priorities in water utilities. Several investigations have been performed for the identification, characterization, treatment options, and treatability of the AOM. Unfortunately, these researchers have proved that the Conventional Potable Water Treatment (CPWT) processes, which consist of coagulation, sedimentation, rapid media filtration and disinfection, are not suitable for reducing the AOM concentration to a level low enough to alleviate odour problems. These researchers have also justified the introduction of advanced or alternative processes such as granular activated carbon bed adsorption, ozonation and membrane filtration for improving AOM removal. The goal of this review is to look at the research which has been done in this area and to find out the best available operations, in terms of AOM reduction, in current CPWT plants for minimizing odour, that can be performed easily and demand minimum budget and modification. For this purpose, options available such as enhanced coagulation, powdered activated carbon adsorption, oxidation and membrane filtration will be investigated and their efficiencies assessed in comparison with the performance of CPWT processes

Stability and structure of pentavalent antimony complexes with aqueous organic ligands

Despite the rapidly growing concern about antimony pollution of waters and soils, the effect of organic matter on the behavior of this toxic trace element is poorly understood because of a lack of data on Sb V-organic ligand interactions in aqueous solution. We used in situ potentiometry and X-ray absorption spectroscopy (XAS) to measure in aqueous solution at ambient conditions the stability and structure of aqueous complexes formed by pentavalent antimony (Sb V) with low molecular weight organic ligands, such as carboxylic acids (acetic, adipic, malonic, lactic, oxalic, citric and salicylic), phenols (catechol), polyols (xylitol and mannitol), and amines (glycine), which have O- and N-functional groups typical of natural organic matter. Potentiometric titrations from pH 2 to 10 demonstrate negligible Sb V complexing with amine and carboxylic acids with single functional group (acetic acid) or non-adjacent functional groups (adipic acid). In contrast, Sb V forms stable complexes with poly-carboxylic, hydroxy-carboxylic acids, and with aliphatic and aromatic polyol ligands in the pH range typical of natural waters. XAS measurements show that in these species the Sb V atom has a distorted octahedral geometry composed of 6 oxygen atoms forming a five- or six-membered bidendate cycle. Stability constants of Sb V-organic complexes, generated for the first time in this study, were used to model Sb V binding with natural humic acids containing the same functional groups as those used in this work. Our predictions of Sb V binding with natural humic acids indicate that in an aqueous organic-rich solution of 1 μg L − 1 Sb and 20 mg L − 1 dissolved organic carbon (DOC) up to 40% of total Sb binds to aqueous organic matter via carboxyl and hydroxy-carboxyl functional groups at pH ≤ 4, whereas at neutral-to-basic pH this amount does not exceed 5%. These estimations are in agreement with direct dialysis measurements conducted with a purified commercial humic acid. The low affinity of Sb V to organic matter at near-neutral pH contrasts with that of Sb III whose organic complexes may account up to 80% of total Sb in DOC-rich waters. The large differences in Sb III versus Sb V binding to organic matter may be used for tracing in organic-rich sediments and waters the two main Sb oxidation states, which have different toxicities for aquatic organisms.

Biodegradation of Aqueous Organic Matter over Seasonal Changes: Bioreactor Experiments with Indigenous Lake Water Bacteria

Artificial groundwater recharge for drinking water production involves infiltration of surface water through sandy soil and its capture into a groundwater aquifer. The transformation of aqueous organic matter is one of the central issues in this process. The purpose of this work was to assess the potential of indigenous microorganisms in the source water to contribute in the aqueous organic matter biodegradation. For this purpose, microorganisms were enriched from the source water in a fluidized-bed reactor (FBR) and used for kinetic studies on biodegradation of organic matter at ambient temperature range. Lake water (total organic carbon 5.8 mg L−1 ) was continuously fed to the FBR containing porous carrier material to support biomass retention. In the inlet and outlet water there were on average 21±6 and 13±5× 105 cells mL−1 , respectively. Biofilm accumulation (as volatile solids) reached 13.1 mg g−1 dw carrier. In the continuous-flow mode and the batch tests, the highest oxygen consumption rate ap...

Lanthanoid behaviour in an acidic landscape

Lanthanoids were studied in a boreal landscape where an abundance of acid sulfate soils and Histosols provide a unique opportunity to increase the understanding of how these metals behave in acidic soils and waters and interact with soil and aqueous organic matter. In the acid sulfate soils lanthanoids are mobile as reflected in high to very high concentrations in soil water and runoff (typically a few mg l −1 but up to 12 mg l −1) and abundant release by several relatively weak extractants (ammonium acetate EDTA, sodium pyrophosphate, hydroxylamine hydrochloride) applied on bulk soil. Normalisation with the lanthanoid pool in the underlying parent materials (sulphide-bearing sediments deposited in brackish-water) and soil water showed that the extensive release/retention in the acidic soil was accompanied by large, and variable, fractionation trends across the lanthanoid series. In low-order streams draining these soils, the lanthanoid concentrations were high and, as indicated by frontal ultrafiltration and geochemical modelling, largely dissolved (<1 kDa) in the form of the species LnSO 4 + and Ln 3+. In other moderately acidic stream waters (pH 4.3–4.6), organic complexation was predicted to be important in the <1 kDa fraction (especially for the heavy lanthanoids) and strongly dominating in the colloidal phase (1 kDa–0.45 μm). Along the main stem of a stream in focus (catchment area of 223 km 2), lanthanoid concentrations increased downstream, in particular during high flows, caused by a downstream increase in the proportion of acid sulfate soils which are extensively flushed during wet periods. The geochemical models applied to the colloidal Ln-organic phase were not successful in predicting the measured fractionation patterns.

Antimony(V) complexing with O-bearing organic ligands in aqueous solution: an X-ray absorption fine structure spectroscopy and potentiometric study

AbstractThe stabilityand structure of aqueous complexes formed by pentavalent antimony (SbV) with simple organic ligands (acetic, adipic, oxalic, citric acids, catechol and xylitol) having O-functional groups (carboxyl, alcoholic hydroxyl, aliphatic and aromatic hydroxyl) typical of natural organic matter (NOM), were determined at 25°C from potentiometric and X-ray absorption fine structure spectroscopy (XAFS) measurements. In organic-free aqueous solutions, spectroscopic data are consistent with the dominant formation of SbV hydroxide species, Sb(OH)5 and Sb(OH)6-, at acid and near-neutral to basic pH, respectively. Potentiometric measurements demonstrate negligible complexing with mono-functional organic ligands (acetic) or those having non-adjacent carboxylic groups (adipic). In contrast, in the presence of poly-functional carboxylic, hydroxyl carboxylic acids and aliphatic and phenolic hydroxyl, SbV forms stable 1:1 or 1:3 complexes in coordination 6 with the studied organic ligands, over a wide pH range pertinent to natural waters (3 ≤ pH ≤ 9). The XAFS measurements show that in these species the central SbV atom has an octahedral geometry with 6 oxygen atoms from hydroxyl moieties and adjacent functional groups (O = C—OH and/or C—OH) of the ligand, forming bidendate chelate cycles. Stability constants for SbV-oxalate complexes generated from potentiometric experiments were used to model SbV complexing with di-carboxylic functional groups of natural humic acids. Our predictions show that in an aqueous solution of pH between 1 and 4 containing 1 μg/l of Sb and 5 mg/l of dissolved organic carbon (DOC), up to 15% of total dissolved Sb maybe bound to aqueous organic matter via di-carboxylic groups.

Excitation—Emission Matrix Fluorescence Spectroscopy for Natural Organic Matter Characterization: A Quantitative Evaluation of Calibration and Spectral Correction Procedures

The influence of different data collection procedures and of wavelength-dependent instrumental biases on fluorescence excitation-emission matrix (EEM) spectral analysis of aqueous organic matter samples was investigated. Particular attention was given to fluorescence contours (spectral shape) and peak fluorescence intensities. Instrumental bias was evaluated by independently applying excitation and emission correction factors to the raw excitation and emission data, respectively. The peak fluorescence intensities of representative natural organic matter and tryptophan were significantly influenced by the application of excitation and emission spectral correction factors and by the manner in which the raw data was collected. Humification and fluorescence indices were also influenced by emission correction factors but were independent of reference (excitation) intensity normalization or correction. EEM surface contours were dependent on normalization of the fluorescence intensity to the reference intensity but were not influenced by either excitation or emission spectral correction factors. Authors should be explicit in how excitation and emission spectral correction procedures are implemented in their investigations, which will help to facilitate intra-laboratory comparisons and data sharing.

Comparison of Spectrophotometric Methods for Measuring Chlorine Dioxide in Drinking Water

The recognition that chlorine disinfection of drinking water may not be effective in controlling pathogens such as Cryptosporidium may lead to the greater use of stronger alternative disinfectants, such as chlorine dioxide. Typical chlorine dioxide residual concentration requirements for disinfection may extend to less than 0.1 mg l−1, thus requiring very good quantitation methods for optimal process control. Traditional methods have been cumbersome and sometimes inaccurate. This study examined three spectrophotometric methods for measuring chlorine dioxide in the <0.1 mg l−1 to 2 mg l−1 range, using acid chrome violet k (ACVK), lissamine green B, and amaranth reagents. Each method was assessed using both laboratory reagent water and various natural waters to identify the respective linear range, method precision, and the possible interference from natural colour due to aqueous organic matter. Interferences arising from the presence of chlorine, chloramines, chlorite, chlorate, and permanganate were also evaluated, along with the potential need to correct for temperature changes.

The organic geochemistry of a sanitary landfill leachate plume

Leachate from the North Bay municipal landfill has contaminated an unconfined, sandy aquifer throughout the 700 m flow system from the site to a discharge zone at a creek. The major organic contaminants identified are aromatic hydrocarbons, especially substituted benzenes. The high groundwater velocity of about 75 m yr −1 and the low organic sorption properties of the sand have permitted non-transformed contaminants to spread throughout the total flow system. There is considerable temporal and spatial variability in groundwater chemistry. Most of the aqueous organic carbon has a nominal molecular weight of <2000 and the general decrease in the mass of this fraction relative to Cl indicates it is being mineralized significantly during transport. IR spectra indicate a general trend of increased aromaticity and decreased OH content of organic matter along the flow system. The aqueous organic matter has a significant apparent complexing capacity and so it is somewhat surprising that toxic metal concentrations in leachate-impacted groundwaters are low. In the leachate plume, this complexing capacity is taken up by major cations and H + and to a far lesser extent by toxic metals such as Pb, Cd or Zn. Dispersion is clearly responsible for considerable decrease in contaminant concentration along the flow system. Biotransformation under strictly anaerobic conditions has probably caused 1,1,1-trichloroethane and trichloroethylene to be restricted to the immediate vicinity of the landfill. A simple method of comparing the concentrations of pairs of organics at points along the flow system provides relative transformation rates for pairs of organics even with variable inputs from the landfill and dispersive dilution. Relative to ethylbenzene, o-xylene is rapidly lost from this system. O-xylene may be less persistent than m- or p-xylene; a result unexpected from previous studies of these dimethylbenzenes. In the initial, strictly anarobic segment of the flow system 1,2,4-trimethylbenzene and 1,4-dichlorobenzene are equally persistent, but in the final, less anaerobic segment, the former appears to be degraded more rapidly than the latter. Contaminant distributions in aquifers reflect the results of a number of processes integrated in a complex manner and so are difficult to interpret in terms of specific processes. However, they do provide evidence for what processes are most significant in real groundwater systems and they will also provide critical tests of how well laboratory-derived information relates to real groundwater contamination situations.