Trace Organics Research Articles

Aerogel volatiles concentrator and analyzer (AVCA) – Collection and concentration of trace volatile organics in aerogel for spectroscopic detection

A study was conducted to determine the efficacy of using silica aerogel to collect and concentrate ambient trace organics for spectroscopic analysis. Silica aerogel was exposed to atmospheres containing trace amounts of polycyclic aromatic and aliphatic hydrocarbons. The organics present were concentrated in the aerogels by factors varying from 10 to more than 1000 over the levels found in the atmospheres, depending on the specific organic present. Since silica aerogel is transparent over a wide range of optical and near infrared wavelengths, UV-induced fluorescence, Raman and infrared spectroscopies were used to detect and identify the organics collected by the aerogel. Measurements were conducted to determine the sensitivity of these spectroscopic methods for determining organics concentrated by aerogels and the effectiveness of this method for identifying systems containing multiple organic species. Polycyclic aromatic hydrocarbons (PAHs) were added to simulated Mars regolith and then vaporized by modest heating in the presence of aerogel. The aerogels adsorbed and concentrated the PAHs, which were detected by induced fluorescence and Raman and FTIR spectroscopies.

The influence of solute polarizability and molecular volume on the rejection of trace organics in loose nanofiltration membrane processes

The removal of trace organic compounds of emerging concern (TrOC) from ground water was evaluated using a split-feed, center exit, nanofiltration (NF) pilot process. Ground water was dosed with varying amounts of bisphenol-A, caffeine, carbamazepine, N,N-diethyl-meta-toluamide, estrone, gemfibrozil, naproxen, sucralose, and sulfamethoxazole between 150 ng/L and 4.5 mg/L, and processed with NF membranes operating at a feed flow rate of 60,636 L/h (267 gpm), a flux rate of 25.6 L m−2 h−1 (15.1 gsfd), and 85% water recovery. TrOC rejection by the NF process ranged from 68% for caffeine to below detection for gemfibrozil and sucralose. Correlations between rejection and various chemical and physical compound properties were investigated. It was found that TrOC rejection correlated well with polarizability (0.94 R2) and molecular volume (0.94 R2), and to a lesser extent hydrophobicity/hydrophilicity (0.87 R2). However, in this work, molecular weight and log D were not well correlated with solute rejection. Analysis of TrOC rejection data collected from five prior independent loose NF research studies representing 61 different TrOCs were found to correlate well with polarizability (0.71 R2) and molecular volume (0.72 R2), suggesting that polarizability and molecular volume are useful in estimating TrOC removal from fresh ground water using loose NF membrane processes.

Modeling the oxidation of phenolic compounds by hydrogen peroxide photolysis

Hydrogen peroxide UV photolysis is among the most widely used advanced oxidation processes (AOPs) for the destruction of trace organics in waters destined for reuse. Previous kinetic models of hydrogen peroxide photolysis focus on the dynamics of hydroxyl radical production and consumption, as well as the reaction of the target organic with hydroxyl radicals. However, the rate of target destruction may also be affected by radical scavenging by reaction products. In this work, we build a predictive kinetic model for the destruction of p-cresol by hydrogen peroxide photolysis based on a complete reaction mechanism that includes reactions of intermediates with hydroxyl radicals. The results show that development of a predictive kinetic model to evaluate process performance requires consideration of the complete reaction mechanism, including reactions of intermediates with hydroxyl radicals.

A Multimedia Fate Model to Support Chemical Management in China: A Case Study for Selected Trace Organics

SESAMe v3.3, a spatially explicit multimedia fate model for China, is a tool suggested to support quantitative risk assessment for national scale chemical management. The key advantage over the previous version SESAMe v3.0 is consideration of spatially varied environmental pH. We evaluate the model performance using estimates of emission from total industry usage of three UV filters (benzophenone-3, octocrylene, and octyl methoxycinnamate) and three antimicrobials (triclosan, triclocarban, and climbazole). The model generally performs well for the six case study chemicals as shown by the comparison between predictions and measurements. The importance of accounting for chemical ionization is demonstrated with the fate and partitioning of both triclosan and climbazole sensitivity to environmental pH. The model predicts ionizable chemicals (triclosan, climbazole, benzophenone-3) to primarily partition into soils at steady state, despite hypothetically only being released to freshwaters, as a result of agricultural irrigation by freshwater. However, further model calibration is needed when more field data becomes available for soils and sediments and for larger areas of water. As an example, accounting for the effect of pH in the environmental risk assessment of triclosan, limited freshwater areas (0.03% or ca. 55 km(2)) in mainland China are modeled to exceed its conservative environmental no-effect threshold. SESAMe v3.3 can be used to support the development of chemical risk assessment methodologies with the spatial aspects of the model providing a guide to the identification regions of interest in which to focus monitoring campaigns or develop a refined risk assessment.

The environmental effect of underground coal gasification semi‐coke on confined groundwater

From the health and environmental point of view, the control of soluble metal elements and organic compounds in underground coal gasification (UCG) by‐product is of great importance for groundwater protection. Unlike the leaching of gasification ash as well as leaching in normal pressure, the leaching of trace elements and organics from UCG semi‐coke into confined groundwater has received little concern. In this research, UCG model test of Inner Mongolia lignite was performed, the obtained UCG semi‐coke was then soaked by applying stainless steel leaching column at 0.5, 1.0, 1.5 and 2.0 MPa with nitrogen as pressurizing agent, the concentrations of trace element and total organic carbons (TOC values) in lixiviums were finally determined by applying ICP‐MS and TOC analyzer to investigate the slight leaching in confined groundwater. The results indicate that Cd, Co, Cr, Ni, Pb and V are undetected in all lixivium samples, and compared with soaking under normal pressure, the concentrations of As, Ba, Mn and Sr are lower in confined water. TOC values in lixivium samples approximately approach to the background value of groundwater, indicating that no extra organic compounds could be leached and TOC values also show the similar changing trend as As, Ba, Mn and Sr behave under normal and high pressures. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1584–1589, 2016

Lander rocket exhaust effects on Europa regolith nitrogen assays

Soft-landings on large worlds such as Europa or our Moon require near-surface retropropulsion, which leads to impingement of the rocket plume on the surface. Surface modification by such plumes was documented on Apollo and Surveyor, and on Mars by Viking, Curiosity and especially Phoenix. The low temperatures of the Europan regolith may lead to efficient trapping of ammonia, a principal component of the exhaust from monopropellant hydrazine thrusters. Deposited ammonia may react with any trace organics, and may overwhelm the chemical and isotopic signatures of any endogenous nitrogen compounds, which are likely rare on Europa. An empirical correlation of the photometrically-altered regions (‘blast zones’) around prior lunar and Mars landings is made, indicating A=0.02T1.5, where A is the area in m2 and W is the lander weight (thus, ~thrust) at landing in N: this suggests surface alteration will occur out to a distance of ~9m from a 200kg lander on Europa.

Elusive anion growth in Titan’s atmosphere: Low temperature kinetics of the C3N[formula omitted] + HC3N reaction

Ion chemistry appears to be deeply involved in the formation of heavy molecules in the upper atmosphere of Titan. These large species form the seeds of the organic aerosols responsible for the opaque haze surrounding the biggest satellite of Saturn. The chemical pathways involving individual anions remain however mostly unknown. The determination of the rates of the elementary reactions with ions and the identification of the products are essential to the progress in our understanding of Titan’s upper atmosphere. We have taken steps in that direction through the investigation of the low temperature reactivity of C3N−, which was tentatively identified in the spectra measured by the CAPS-ELS instrument of the Cassini spacecraft during its high altitude flybys. The reaction of this anion with HC3N, one of the most abundant trace organics in the atmosphere, has been studied over the 49–294 K temperature range in uniform supersonic flows using the CRESU technique. The proton transfer is found to be the main exit channel (>91%) of the C315N− + HC3N reaction. It remains however indistinguishable with the non-isotopically labeled C314N− reactant. The T−1/2 temperature dependence of this proton transfer reaction and its global rate are reasonably well reproduced theoretically using an average dipole orientation model. A minor exit channel, reactive detachment (< 9%), has also been uncovered, although the nature of the neutral products has not been determined. It is concluded that the C314N− + HC3N reaction cannot contribute to the growth of molecular anions in the upper atmosphere of Titan. Due to the low branching into the neutral exit channel, it cannot contribute either to the growth of neutrals even assuming a complete mass transfer.

Treatment of Wastewater from a Dairy Industry Using Rice Husk as Adsorbent: Treatment Efficiency, Isotherm, Thermodynamics, and Kinetics Modelling

Effluent from milk processing unit contains soluble organics, suspended solids, and trace organics releasing gases, causing taste and odor, and imparting colour and turbidity produced as a result of high consumption of water from the manufacturing process, utilities and service section, chemicals, and residues of technological additives used in individual operations which makes it crucial matter to be treated for preserving the aesthetics of the environment. In this experimental study after determination of the initial parameters of the raw wastewater it was subjected to batch adsorption study using rice husk. The effects of contact time, initial wastewater concentration, pH, adsorbent dosage, solution temperature and the adsorption kinetics, isotherm, and thermodynamic parameters were investigated. The phenomenon of adsorption was favoured at a lower temperature and lower pH in this case. Maximum removal as high as 92.5% could be achieved using an adsorbent dosage of 5 g/L, pH of 2, and temperature of 30°C. The adsorption kinetics and the isotherm studies showed that the pseudo-second-order model and the Langmuir isotherm were the best choices to describe the adsorption behavior. The thermodynamic parameters suggested that not only was the adsorption by rice husk spontaneous and exothermic in nature but also the negative entropy change indicated enthalpy driven process.

Technical Brief: Trace Organic Compounds and Implications for Wastewater Treatment

This Technical Brief has been prepared in response to concerns over the presence of trace organic compounds (TO r C) in wastewater, water supplies, and the receiving environment (Associated Press, 2008, WERF 2005, Ternes et al., 2004). The purpose of this brief is to summarize available scientific data on TOrC in wastewater and the receiving environment that can put these concerns into perspective. It begins with information on how we identify and measure the levels of TOrC, then describes the removal of TO r C in typical wastewater treatment processes. The potential human health and ecological effects of TO r C that may be discharged to surface waters and/or taken up in public water supplies is also evaluated. The brief identifies management strategies that are either being considered or implemented along with future research needs. Our society uses tens of thousands of organic chemicals that may ultimately reach municipal wastewater treatment plants and then the surface waters and ground waters that receive treated effluent from those plants. Persistent TO r C can remain in surface water for time periods on the order of days to weeks or months, which allows time for these compounds to travel significant distances downstream. Recalcitrant TO r C in groundwater can persist for even longer periods of time. The land application of biosolids provides another potential pathway for release of TO r C. As a result, aquatic, terrestrial and human populations potentially may be exposed to persistent TO r C in the environment before these compounds attenuate. The ability to detect and measure trace organics in the environment is a critical link to understanding their sources, potential effects, and removal options. The characterization of TO r C in environmental samples is no simple matter, given that approximately 63,000 chemicals are in common use worldwide and that authorities do not yet agree on which TO r C should be monitored in the environment. The analytical methods typically used for environmental characterization and regulatory purposes have predominantly addressed high-use industrial chemicals of demonstrated toxicity. With limited exceptions, these methods cannot satisfy measurement needs for the expanded universe of TO r C. Many individual chemicals have not been addressed in standard environmental analysis methods published by regulatory agencies, and sensitivity towards those that are included is often not adequate. An alternative to measuring TO r C concentrations in surface water, not discussed in detail in this Technical Brief, is modeling such concentrations. This title belongs to WERF Research Report Series ISBN: 9781843395249 (eBook)

Direct Determination of Thermodynamic Association Constants of Charge Transfer Complexes Using High Performance Thin Layer Chromatography

Few accurate thermodynamic association constant K DA values of charge transfer complexes (DA) taking donor (D) and acceptor (A) in stoichiometric ratios are available and there is no method to determine directly the concentration of the complexes in solution. HPTLC, an extensively used technique to estimate the amount of trace organics, had been found to be a valuable method to directly determine the compositions and the association constants K DA of the complexes when D and A are in their stoichiometric ratios. HPTLC with a video densitometer was successfully utilized for estimating the concentrations of charge-transfer complexes between isoniazid/nicotinamide with acceptors like p-chloranil, chloranilic acid, tetracyanoethylene and dichlorodicyanobenzoquinone in acetonitrile solution. The compositions of the complexes and the thermodynamic association constants were determined (donor and the acceptors in stoichiometric ratios) by comparing the mobility of the migrated donors (i.e., isoniazid/nicotinamide) in acetonitrile solution from the complexes with the respective blanks. The areas of spots of the donors were measured densitometrically. The K DA values determined using the HPTLC technique were verified and validated using a widely accepted spectrophotometric method. The method can also be utilized for determination of equilibrium constants of the complexes. It is a rapid, economic and eco-friendly method.

Residual archives on organochlorine insecticides in the core sediment of a tropical estuary, India

A comprehensive evaluation of the residual levels of Organochlorine insecticides (OCIs) in the sediment cores of Cochin Estuarine System (CES) is highlighted in this research article. It assessed the distribution pattern and impact of these xenobiotics in this environmental niche. Fifteen persistent organochlorine compounds (OCs) were quantitatively analysed in the six sediment core samples collected from specific sites of CES, during November 2009. Among these contaminants, residual levels of HCH, Cyclodienes and DDT were the dominant entities. According to the sediment quality guidelines (SQGs), the higher concentration of these persistent toxicants found in the CES was enough to pose ecological risk to the bottom dwelling consumers. This study provides a better understanding of these trace organics in the environment and could develop more effective strategies for protecting this vulnerable ecosystem from further pollution. Further, sediment screening bioassays can also be conducted for both sediment quality evaluation and identification of existing potent toxicants.

M-PGMA as a new water treatment agent to remove oxytetracycline from water

Magnetic ion exchange resin is a strong base anion exchange resin with magnetic properties that can be used to remove negatively charged materials from water. Magnetic poly glycidyl methacrylate resin (m-PGMA), a new type of resin, has shown better removal performance for humics than MIEX®. Removal of oxytetracycline (OTC) in water by m-PGMA, and factors influencing the removal, were examined, and in addition, the removal of OTC by MIEX and powdered activated carbon (PAC) were used as a comparison. Results showed that m-PGMA could remove more OTC than MIEX and PAC. The removal performance was greatly affected by dosage of m-PGMA, inorganic anions, organics and pH value. At a contact time of 30 min, the removal rates of OTC were 45%, 52% and 63% when the dosage was 5 ml/L, 10 ml/L and 20 ml/L, respectively. In comparison the removal rate of OTC by MIEX was 45% with a dosage of 10 mL/L and a contact time of 30 min. The removal of OTC was significantly increased when the pH value was above 7.3, as the OTC molecule exists as an anion in alkaline medium. In conclusion, m-PGMA is more effective than MIEX and PAC in the removal of OTC in water, and can be one of the choices to remove trace organics like OTC.

Meeting multiple water quality objectives through treatment using locally generated char: improving organoleptic properties and removing synthetic organic contaminants and disinfection by-products

A variety of natural and anthropogenic contaminants can compromise the safety and esthetics of surface water collected for drinking and disinfected using chlorine by households in developing communities. While household chlorination is effective against most microbial pathogens, many users find the taste and odor of chlorine unacceptable and revert to drinking untreated water. Moreover, reactions between chlorine and the dissolved organic matter form harmful disinfection by-products (DBPs) such as trihalomethanes (THMs). Char adsorbers have been used to treat drinking water for thousands of years and are still widely used today. Results obtained here demonstrate that locally produced biomass chars (biochars) exhibit removal capacities comparable to those of activated carbon for removal of THMs, synthetic organic chemicals (SOCs) such as warfarin (WFN) (anticoagulant pharmaceutical, rodenticide), and naturally occurring trace organics such as the taste-and-odor compound 2-methylisoborneol (cyanobacterial metabolite). Results show chars can be used effectively to remove objectionable tastes and odors related to chlorine and cyanobacteria, DBPs, and SOCs. The use of char may lead to microbial risk reduction through greater acceptance of chlorine-based disinfection due to improved water esthetics, as well as chemical risk reduction associated with DBP and SOC exposure.

Fate of trace organics in a wastewater effluent dependent stream

Trace organic compounds (TOrCs) in municipal wastewater effluents that are discharged to streams are of potential concern to ecosystem and human health. This study examined the fate of a suite of TOrCs and estrogenic activity in water and sediments in an effluent-dependent stream in Tucson, Arizona. Sampling campaigns were performed during 2011 to 2013 along the Lower Santa Cruz River, where TOrCs and estrogenic activity were measured in aqueous (surface) and solid (riverbed sediment) phases. Some TOrCs, including contributors to estrogenic activity, were rapidly attenuated with distance of travel in the river. Those TOrCs that are not sufficiently attenuated and percolate to ground water have in common low biodegradation probabilities and low octanol–water distribution ratios. Independent experiments showed that attenuation of estrogenic compounds may be due in part to indirect photolysis caused by formation of organic radicals from sunlight absorption. Hydrophobic TOrCs may accumulate in riverbed sediments during dry weather periods, but riverbed sediment quality is periodically affected through storm-related scouring during periods of heavy rainfall and runoff. Taken together, evidence suggests that natural processes can attenuate at least some TOrCs, reducing potential impacts to ecosystem and human health.

Pyrolysis and Char Characterization of Refuse-Derived Fuel Components

This work concentrates on the pyrolysis and char characterization of a refuse-derived fuel (RDF), produced from municipal solid waste, and five of its components, namely, nonpackaging paper, food, textile, low-density polyethylene film, LDPE, and packaging polypropylene wastes. Specifically, this work characterizes physically and chemically the materials, examines the pyrolysis and oxidation patterns of the RDF and its components using thermogravimetric analysis (TGA) and a quartz reactor (QR), respectively, evaluates the reactivity toward oxygen of selected RDF chars at 650 °C in the QR, and characterizes the trace organics emission during the pyrolysis and chars oxidation in the QR by means of gas chromatography coupled with mass spectrometry. The main conclusions of this study are as follows: (1) the pyrolysis and oxidation patterns indicate the presence of low-stability organic components, lignocellulosic materials, and plastics but with the maximum rates occurring at lower temperatures than those reported in the literature; (2) the reactivity toward oxygen of chars at 650 °C revealed that the food waste and the LDPE film waste chars are among the less reactive chars, while the textiles waste and the packaging PP waste chars are among the more reactive chars; the RDF char reactivity resembles mostly that of the nonpackaging paper waste char; (3) analyses of the trace organic elements released reflect the transversal contamination of the different materials that compose RDF, derived from its mixed origin. During both pyrolysis and char combustion, phthalates were the most relevant compounds encountered.

Detection of trace organics in Mars analog samples containing perchlorate by laser desorption/ionization mass spectrometry.

Evidence from recent Mars missions indicates the presence of perchlorate salts up to 1 wt % level in the near-surface materials. Mixed perchlorates and other oxychlorine species may complicate the detection of organic molecules in bulk martian samples when using pyrolysis techniques. To address this analytical challenge, we report here results of laboratory measurements with laser desorption mass spectrometry, including analyses performed on both commercial and Mars Organic Molecule Analyzer (MOMA) breadboard instruments. We demonstrate that the detection of nonvolatile organics in selected spiked mineral-matrix materials by laser desorption/ionization (LDI) mass spectrometry is not inhibited by the presence of up to 1 wt % perchlorate salt. The organics in the sample are not significantly degraded or combusted in the LDI process, and the parent molecular ion is retained in the mass spectrum. The LDI technique provides distinct potential benefits for the detection of organics in situ on the martian surface and has the potential to aid in the search for signs of life on Mars.

Use of biomimetic forward osmosis membrane for trace organics removal

The use of forward osmosis for the removal of trace organics from water has recently attracted considerable attention as an alternative to traditional pressure driven membrane filtration. However, the existing forward osmosis membranes have been found to be ineffective at rejecting small neutral organic pollutants, which limits the applicability of the forward osmosis process. In this study a newly developed biomimetic membrane was tested for the removal of three selected trace organics that can be considered as a bench marking test for a membrane׳s ability to reject small neutral organic pollutants in aqueous solution. The performance of this membrane was compared with a standard cellulose acetate forward osmosis membrane. The aquaporin membrane was found to have rejection values above 97% for all three trace organics, which was significantly higher than the cellulose acetate membrane. This difference is caused by differences in the transport mechanisms. For the cellulose acetate membrane rejection is controlled by steric hindrance, which results in a size dependent rejection of the trace organics, whereas rejection by the aquaporin membrane is controlled by diffusion of the trace organics. Furthermore, the aquaporin membrane was found to have a higher pure water flux.

Are Trace Organic Compounds (TOrCs) a Risk to Your Aquatic Life? A Framework for Evaluating the Potential Effects of Trace Organics

Are Trace Organic Compounds (TOrCs) a Risk to Your Aquatic Life? A Framework for Evaluating the Potential Effects of Trace Organics

Mechanism of removal of pharmaceuticals and personal care products by nanofiltration membranes

Much attention has been paid to pharmaceuticals and personal care products (PPCPs). Nanofiltration (NF) is a new type of separation technology developed between ultrafiltration and reverse osmosis (RO) in the mid-1980s, which is a continuation and development branch of the ultra-low pressure RO technology. PPCPs are a kind of water ubiquitous trace organics, and there are some disadvantages of the PPCPs, such as recalcitrance, accumulation of biological toxicity and long-term dangers, which gradually attracts the attention of the scientific community due to the harm to the environment and ecosystems. This paper analyses the latest research progress in this country and overseas, introducing the advantages on removal of the PPCPs by NF membranes, also recommending the mechanism of the removal process and influencing factors. The direction of future research is proposed as well.

Treatment of cosmetic wastewater by a full-scale membrane bioreactor (MBR).

This work evaluates the treatment of wastewater from a personal care products factory by a full-scale side-stream membrane bioreactor (MBR) intermittently fed. The wastewater contained particulate and soluble chemical oxygen demand (COD) which is partially removed by physicochemical pretreatment. Steady removal efficiencies above 98 % were achieved for BOD5, COD and suspended solids. Fats, oils and grease present in the raw wastewater were also successfully removed. The MBR was operated at an average permeate flux of 12 L/m2 · h (LMH) working at a transmembrane pressure of 272 ± 97 mbar. The soluble microbial products concentration remained fairly stable at 175 ± 25 and 85 ± 15 mg/L for proteins and carbohydrates, respectively. This maintained the filtration characteristics of the mixed liquor unaltered over a long-term basis, which was evidenced by a constant permeability of 43 ± 19 LMH/bar. Most of the trace organics detected in the wastewater were completely removed and only some fragrances were detected in the permeate at trace concentrations.