Chemical Composition Information Research Articles

Texas Department of Transportation Fly Ash Database and the Development of Chemical Composition–Based Fly Ash Alkali-Silica Reaction Durability Index

Chemical compositions of approximately 5,500 fly ash samples from 36 power plants inside and outside Texas, compiled by the Texas Department of Transportation (TxDOT) over 18 years, were statistically analyzed in this study. The variations of oxide contents and their correlations were calculated and compared. Oxide contents of Class F fly ashes were found to be more variable than Class C fly ashes. In general, CaO and MgO contents were higher in Class C fly ashes than in Class F fly ashes, whereas the latter had higher SiO2 content. Other oxide contents of the two classes of fly ashes were comparable. Then, to demonstrate the potential beneficial use of chemical composition information of fly ash, an alkali-silica reaction (ASR) durability index was proposed to predict the comparative performance of fly ash in mitigating ASR in concrete. The index value was calculated using SiO2, Fe2O3, Al2O3, CaO, and equivalent alkali contents. Previously published research on the use of fly ash in mitigating ASR, using standardized tests, was utilized to validate the proposed index. The index was found capable of differentiating fly ashes in the same class. To verify the usefulness of the ASR durability index, tests were carried out in this study using an ASR reactive sand, two portland cements, four Class C fly ashes, and one Class F fly ash. The results were quite promising, and the use of the fly ash ASR durability index is proposed to screen fly ash for laboratory testing and construction.

Progress on chemical pattern recognition in traditional Chinese medicines by multidimensional information of metabolic fingerprinting analysis

As a comprehensive, quantifiable identification method based on the chemical composition information of traditional Chinese medicine (TCM), the fingerprint of traditional Chinese medicine has become an internationally recognized effective way to control the quality of natural medicine. Chemical pattern recognition in traditional Chinese medicines is an important breakthrough for the infiltration between fuzzy and pharmaceutical sciences, has been used in the field of quality assessment and control for traditional Chinese medicine. It has solved the problem of comprehensive analysis with multi-dimensional information, and gradually been accepted by more researchers to in-depth study in the further. With the development of modern chemical analysis and computer techniques, there are more technologies were applied to the establishment of fingerprints of traditional Chinese medicine, more chemometric methods have been applied to the data processing of TCM fingerprint, and more quality identification and assessment for TCM to be achieved. And the technology has matured and achieved a lot. In this paper, we make a review for the chemical pattern recognition in traditional Chinese medicines since it be invented, provide a reference for the further research.

Frost flowers growing in the Arctic ocean‐atmosphere–sea ice–snow interface: 1. Chemical composition

Frost flowers, intricate featherlike crystals that grow on refreezing sea ice leads, have been implicated in lower atmospheric chemical reactions. Few studies have presented chemical composition information for frost flowers over time and many of the chemical species commonly associated with Polar tropospheric reactions have never been reported for frost flowers. We undertook this study on the sea ice north of Barrow, Alaska to quantify the major ion, stable oxygen and hydrogen isotope, alkalinity, light absorbance by soluble species, organochlorine, and aldehyde composition of seawater, brine, and frost flowers. For many of these chemical species we present the first measurements from brine or frost flowers. Results show that major ion and alkalinity concentrations, stable isotope values, and major chromophore (NO3− and H2O2) concentrations are controlled by fractionation from seawater and brine. The presence of these chemical species in present and future sea ice scenarios is somewhat predictable. However, aldehydes, organochlorine compounds, light absorbing species, and mercury (part 2 of this research and Sherman et al. (2012)) are deposited to frost flowers through less predictable processes that probably involve the atmosphere as a source. The present and future concentrations of these constituents in frost flowers may not be easily incorporated into future sea ice or lower atmospheric chemistry scenarios. Thinning of Arctic sea ice will likely present more open sea ice leads where young ice, brine, and frost flowers form. How these changing ice conditions will affect the interactions between ice, brine, frost flowers and the lower atmosphere is unknown.

Limitations and potentials of dual-purpose cow herds in Central Coastal Veracruz, Mexico

Feed chemical and kinetic composition and animal performance information was used to evaluate productivity limitations and potentials of dual-purpose member herds of the Genesis farmer organization of central coastal Veracruz, Mexico. The Cornell Net Carbohydrate and Protein System model (Version 6.0) was systematically applied to specific groups of cows in structured simulations to establish probable input–output relationships for typical management, and to estimate probable outcomes from alternative management based on forage-based dietary improvements. Key herd vulnerabilities were pinpointed: chronic energy deficits among dry cows of all ages in late gestation and impeded growth for immature cows. Regardless of the forage season of calving, most cows, if not all, incur energy deficits in the final trimester of gestation; thus reducing the pool of tissue energy and constraining milking performance. Under typical management, cows are smaller and underweight for their age, which limits feed intake capacity, milk production and the probability of early postpartum return to ovarian cyclicity. The substitution of good-quality harvested forage for grazing increased predicted yields by about one-third over typical scenarios for underweight cows. When diets from first parturition properly supported growth and tissue repletion, milk production in second and third lactations was predicted to improve about 60%. Judiciously supplemented diets based on good quality grass and legume forages from first calving were predicted to further increase productivity by about 80% across a three-lactation cow lifetime. These dual-purpose herd owners have large incentives to increase sales income by implementing nutritional strategies like those considered in this study.

Method to isolate and characterize oligomers present in the aqueous phase in emulsion copolymerization

In order to model the entry of radical in emulsion copolymerization, a study of the oligomers present in the aqueous phase is necessary. In this work a new method for separation and characterization of the aqueous phase has been developed. MALDI-ToF-MS was found to be a powerful technique in order to characterize the oligomers present in the aqueous phase. It is for the first time that full chemical composition and molecular weight information of the oligomers present in the aqueous phase in emulsion copolymerization has been obtained. The methodology was shown to be semi-quantitative and several factors were studied, for example temperature effects, interference of latex particles present in serum of the aqueous phase and type of ionizing salt in MALDI. It was shown that the methodology works well, even though we are dealing with small quantities of oligomers and the possibility of mass discrimination in MALDI-ToF-MS.

Volatile organic compounds in pesticide formulations: Methods to estimate ozone formation potential

The environmental fate and toxicity of active ingredients in pesticide formulations has been investigated for many decades, but relatively little research has been conducted on the fate of pesticide co-formulants or inerts. Some co-formulants are volatile organic compounds (VOCs) and can contribute to ground-level ozone pollution. Effective product assessment methods are required to reduce emissions of the most reactive VOCs. Six emulsifiable concentrate pesticide products were characterized for percent VOC by thermogravimetric analysis (TGA) and gas chromatography–mass spectrometry (GC–MS). TGA estimates exceeded GC–MS by 10–50% in all but one product, indicating that for some products a fraction of active ingredient is released during TGA or that VOC contribution was underestimated by GC–MS. VOC profiles were examined using TGA–Fourier transform infrared (FTIR) evolved gas analysis and were compared to GC–MS results. The TGA–FTIR method worked best for products with the simplest and most volatile formulations, but could be developed into an effective product screening tool. An ozone formation potential (OFP) for each product was calculated using the chemical composition from GC–MS and published maximum incremental reactivity (MIR) values. OFP values ranged from 0.1 to 3.1 g ozone g−1 product. A 24-h VOC emission simulation was developed for each product assuming a constant emission rate calculated from an equation relating maximum flux rate to vapor pressure. Results indicate 100% VOC loss for some products within a few hours, while other products containing less volatile components will remain in the field for several days after application. An alternate method to calculate a product OFP was investigated utilizing the fraction of the total mass of each chemical emitted at the end of the 24-h simulation. The ideal assessment approach will include: 1) unambiguous chemical composition information; 2) flexible simulation models to estimate emissions under different management practices; and 3) accurate reactivity predictions.

Improving SERS Detection of Bacillus thuringiensis Using Silver Nanoparticles Reduced with Hydroxylamine and with Citrate Capped Borohydride

The development of techniques that could be useful in fields other than biological warfare agents countermeasures such as medical diagnostics, industrial microbiology, and environmental applications have become a very important subject of research. Raman spectroscopy can be used in near field or at long distances from the sample to obtain fingerprinting information of chemical composition of microorganisms. In this research, biochemical components of the cell wall and endospores of Bacillus thuringiensis (Bt) were identified by surface‐enhanced Raman scattering (SERS) spectroscopy using silver (Ag) nanoparticles (NPs) reduced by hydroxylamine and borohydride capped with sodium citrate. Activation of “hot spots”, aggregation and surface charge modification of the NPs, was studied and optimized to obtain signal enhancements from Bt by SERS. Slight aggregation of the NPs as well as surface charge modification to a more acidic ambient was induced using small‐size borohydride‐reduced NPs in the form of metallic suspensions aimed at increasing the Ag NP‐Bt interactions. Hydroxylamine‐reduced NPs required slight aggregation and no pH modifications in order to obtain high spectral quality results in bringing out SERS signatures of Bt.

An evaluation and comparison of cloud condensation nucleus activity models: Predicting particle critical saturation from growth at subsaturation

The ability of particles to activate and form cloud droplets influences the functioning of the Earth's hydrological cycle. This work links the particle water uptake at subsaturation to the critical supersaturation ratio needed for particles to become cloud condensation nuclei (CCN). Five models using the particle hygroscopic growth at subsaturation for predicting the critical supersaturation needed for droplet activation were applied to a laboratory data set of inorganic and organic compounds and mixtures of them. The data set consisted of hygroscopicity tandem differential mobility analyzer measurements and CCN counter measurements. No chemical composition information was used when applying the models. All models tested were based on modifications of Köhler theory and gave similar results. The agreement between predicted and measured critical supersaturations was good, considering the relatively simple models used. A trend of overestimating the critical supersaturations was observed, typically by ∼15%. The best performing model gave on average only a 4% offset from experimental values; the model with the largest deviation was offset by 20%. A comparison was made between the number of soluble entities (ions or nondissociating molecules) estimated from the particle hygroscopic growth at 90% relative humidity (RH) and the number estimated from the particle critical supersaturation; a ∼35% increase was observed in the effective number of entities in solution when going from 90% RH to activation. For many types of aerosols, differences in the model approaches tested do not induce large differences in the predicted critical supersaturation. However, it is most important to follow the recommendations published with the respective models and not use them indiscriminately.

Transmission electron microscopy study of multilayer p– n hetero-junction La 0.9Sr 0.1MnO 3/SrNb 0.05Ti 0.95O 3 thin films

We have fabricated multilayer p– n hetero-junction structure La 0.9Sr 0.1MnO 3/SrNb 0.05Ti 0.95O 3 colossal magneto-resistivity thin films. The observations of transmission electron microscopy showed that the interfacial structure between La 0.9Sr 0.1MnO 3 and SrNb 0.05Ti 0.95O 3 was of great epitaxy and atomic level smooth. There was a superstructure within La 0.9Sr 0.1MnO 3 thin films which was clarified in terms of the ordered partial substitution of La with Sr at center body of unit cell. Its chemical composition and distribution information investigated by electron energy loss spectrum and element mapping in the multilayer thin films were discussed.

Mapping complex microstructures in powder metallurgy steels

New methods of characterising multiple phase powder metallurgy steels have been investigated. Mapping of microhardness with a lateral resolution of as little as 5 μm and with up to 104 indents can produce distributions of mechanical properties which are characteristic of different steel grades. Maps of these properties can be correlated with the different phases observed in etched microstructures, and quantification of size and interconnectivity of the regions with, for example, different hardness or stiffness is then possible. Electron backscatter diffraction can also produce simultaneously highly detailed maps of the different phases in a powder metallurgy steel with chemical composition information. Percentages of the different phases present can be determined from the crystallography and morphology of the grains observed, but the technique is limited by the speed with which maps can be acquired.

Composition and Morphology of Individual Combustion, Biomass Burning, and Secondary Organic Particle Types Obtained Using Urban and Coastal ATOFMS and STXM-NEXAFS Measurements

Complementary single particle measurements of organic aerosols using aerosol time-of-flight mass spectrometry (ATOFMS) and Scanning Transmission X-ray Microscopy—Near Edge X-ray Absorption Fine Structure (STXM-NEXAFS) are compared to examine the relationships between particle morphologies and chemical composition of particles having similar sources. ATOFMS measurements provide size-resolved chemical composition information for single particles. Measurements from field campaigns in polluted or urban (Riverside/SOAR 2005; Mexico City/MILAGRO 2006; Port of Long Beach 2007) and clean or marine (Arabian Sea/INDOEX 1999; Sea of Japan/ACE-Asia 2001; Trinidad Head/CIFEX 2004) locations illustrate regional differences. The majority (≥ 85 %) of the number of submicron particles are carbonaceous (including elemental and organic carbon), but represent less than 10% of the number of supermicron particles. Organic carbon (OC) particles are classified into three meta-classes corresponding to (1) combustion generated OC/...

Relating Complex Fluid Composition and Thermophysical Properties with the Advanced Distillation Curve Approach

AbstractComplex fluids have long posed a significant challenge in our ability to characterize and model fluid properties. Here, we consider complex fluids to be mixtures with many components that can differ significantly in polarity and polarizability. The penultimate complex fluid is crude oil, although many other fluids such as finished fuels are also highly complex. We have recently introduced a measurement strategy that can simplify these efforts and provides the added potential of linking chemical composition (i.e. analytical) information with physical property information. In addition to chemical characterization, the approach provides the ability to calculate thermodynamic and transport properties for such complex heterogeneous streams. The technique is based on the advanced distillation curve (ADC) metrology, which separates a complex fluid by distillation into fractions that are sampled, and for which thermodynamically consistent temperatures are measured at atmospheric pressure. The collected sample fractions can be analyzed by any method that is appropriate. Analytical methods we have applied include gas chromatography (with flame ionization, mass spectrometric and sulfur chemiluminescence detection), thin‐layer chromatography, FTIR, Karl Fischer coulombic titrimetry, refractometry, corrosivity analysis, neutron activation analysis and cold neutron prompt gamma activation analysis. We have applied this method on product streams such as finished fuels (gasoline, diesel fuels, aviation fuels, rocket propellants), crude oils (including a crude oil made from swine manure) and waste oil streams (used automotive and transformer oils). In this review, we describe the essential features of the ADC metrology with illustrative examples.

Chemical Composition and Nutrition Information of a Newly Developed Immune Enhancing Power Bar for Immune Deficient Patients

A i mmune enhancing power bar currently developed in the Vaal University of technology were screened for it's nutritional information considering both analytical and calculated nutritional information. It was found that apart of moisture and total carbohydrate which were underestimated, all values of proximate composition were a bit higher than values obtained by calculation, thus overestimated. There is globally a reduction of micro nutrients like the one of Vit. A and E which show a gap of 70% and 48% respectively between calculated values and analytical values. The differences were found to be less significant for all minerals. Despite this, the new power bar can be considered as a powerful immune-enhancing meal, as it present most of required energy and key nutrients needed by people living with HIV/AIDS. However, in order to complete the development process all ingredients used need to undergo further refinement and optimization in the form of chemical and scientific analysis. This newly developed immune enhancing power bar can be linked to a prompt diagnosis and treatment of people living with HIV/AIDS, including use of antiretroviral treatment (ART) when indicated to improve their nutrition and health status.

Nanoscale structures and mechanics of barnacle cement

Polymerized barnacle glue was studied by atomic force microscopy (AFM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and chemical staining. Nanoscale structures exhibiting rod-shaped, globular and irregularly-shaped morphologies were observed in the bulk cement of the barnacle Amphibalanus amphitrite (=Balanus amphitrite) by AFM. SEM coupled with energy dispersive X-ray (EDX) provided chemical composition information, making evident the organic nature of the rod-shaped nanoscale structures. FTIR spectroscopy gave signatures of β-sheet and random coil conformations. The mechanical properties of these nanoscale structures were also probed using force spectroscopy and indentation with AFM. Indentation data yielded higher elastic moduli for the rod-shaped structures when compared with the other structures in the bulk cement. Single molecule AFM force-extension curves on the matrix of the bulk cement often exhibited a periodic sawtooth-like profile, observed in both the extend and retract portions of the force curve. Rod-shaped structures stained with amyloid protein-selective dyes (Congo red and thioflavin-T) revealed that about 5% of the bulk cement were amyloids. A dominant 100 kDa cement protein was found to be mechanically agile, using repeating hydrophobic structures that apparently associate within the same protein or with neighbors, creating toughness on the 1–100 nm length scale.

Improving the Screening Process for the Selection of Potato Breeding Lines with Enhanced Polyphenolics Content

Efficient selection of potato varieties with enhanced nutritional quality requires simple, rapid, accurate, and cost-effective assays to obtain tuber chemical composition information. Our objective was to develop simple protocols to determine phenolics, anthocyanins, and antioxidant capacity in polyphenolic extracts of potatoes using Fourier transform infrared spectroscopy combined with multivariate techniques. Lyophilized potato samples (23) were analyzed. Polyphenolic compounds were extracted from potatoes and applied directly applied onto a three-bounce ZnSe crystal for attenuated total reflectance measurements in the infrared region of 4000 to 700 cm (-1). Robust models were generated (r > or = 0.99) with standard error of cross-validation values of 4.17 mg gallic acid equivalent/100 g (total phenolics), 0.87 mg pelargonidin-3-glucoside/100 g (monomeric anthocyanins), and 130.8 mumol Trolox equivalent/100 g (antioxidant capacity) potato powder. In addition, classification models discriminated potato samples at the species and variety level. Application of a simple infrared spectroscopic protocol allowed simultaneous rapid quantification of specific nutritional components in potatoes and efficient selection of value-added potato varieties.

Comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry and simultaneous electron capture detection/nitrogen phosphorous detection for incense analysis

This study reports comprehensive two-dimensional gas chromatography hyphenated to time-of-flight mass spectrometry detection (GC × GC/TOFMS) for characterisation and identification of components generated by four different types of powdered incense headspace (H/S) and incense smoke. GC × GC/TOFMS allowed simultaneous separation and identification of compounds emitted into the atmosphere as a result of combustion of incense powder. The smoke stream comprised compounds originating from the incense powder, and combustion products such as saturated and unsaturated hydrocarbons, essential oil type compounds, nitromusks, fatty acid methyl esters (FAMEs), polycyclic aromatic hydrocarbons (PAHs, which possibly include oxygenated and nitrated PAH), N-heterocyclics, pyrans and furans, which were detected and tentatively identified by GC × GC/TOFMS. GC × GC-electron capture detector/nitrogen phosphorous detector (ECD/NPD) potentially offers the prospect of providing selective chemical compositional information of incense powder and smoke, such as nitrogen-containing (N-containing) and halogenated compounds. Results of GC×GC-ECD/NPD showed that both incense powder and smoke generated emission of N-containing and halogenated compounds. A significant number of halogenated and N-containing compounds were emitted during the incomplete combustion of incense. However, one further objective of this paper is to demonstrate the capacity of comprehensive two-dimensional gas chromatography coupled to specific and/or selective detectors such as those used in this study (GC × GC-ECD/NPD) for the detection of particular classes of compounds such as N-containing and halogenated compounds at trace level concentrations in complex smoke samples.

Distinguishing solid bitumens formed by thermochemical sulfate reduction and thermal chemical alteration

Insoluble solid bitumens are organic residues that can form by the thermal chemical alteration (TCA) or thermochemical sulfate reduction (TSR) of migrated petroleum. TCA may actually encompass several low temperature processes, such as biodegradation and asphaltene precipitation, followed by thermal alteration. TSR is an abiotic redox reaction where petroleum is oxidized by sulfate. It is difficult to distinguish solid bitumens associated with TCA of petroleum from those associated with TSR when both processes occur at relatively high temperature. The focus of the present work was to characterize solid bitumen samples associated with TCA or TSR using X-ray photoelectron spectroscopy (XPS). XPS is a surface analysis conducted on either isolated or in situ (>25 μm diameter) solid bitumen that can provide the relative abundance and chemical speciation of carbon, organic and inorganic heteroatoms (NSO). In this study, naturally occurring solid bitumens from three locations, Nisku Fm. Brazeau River area (TSR-related), LaBarge Field Madison Fm. (TSR-related), and the Alaskan Brooks range (TCA-related), are compared to organic solids generated during laboratory simulation of the TSR and TCA processes. The abundance and chemical nature of organic nitrogen and sulfur in solid bitumens can be understood in terms of the nature of (1) petroleum precursor molecules, (2) the concentration of nitrogen by way of thermal stress and (3) the mode of sulfur incorporation. TCA solid bitumens originate from polar materials that are initially rich in sulfur and nitrogen. Aromaticity and nitrogen increase as thermal stress cleaves aliphatic moieties and condensation reactions take place. Organic sulfur in TCA organic solids remains fairly constant with increasing maturation (<3.4 sulfurs per 100 carbons) due to offsetting preservation and H 2S elimination reactions. In contrast, TSR solid bitumens are sulfur rich and nitrogen poor solids. These heteroatom distributions are attributed to the ability of TSR to incorporate copious amounts of inorganic sulfur (>3.5 to ∼17 sulfur per 100 carbons) into aromatic structures and to the low levels of nitrogen in their hydrocarbon precursors. Hence, XPS results provide organic chemical composition information that helps to distinguish whether solid bitumen, either in situ or removed and concentrated from the rock matrix, was formed via the TCA or TRS process.

Tissue‐Specific Sampling for the Estimation of Striped Bass Whole‐Body Proximate Composition

AbstractThe need for precise estimates of chemical components of fish is common among the fields of aquaculture, fish health, and bioenergetics in fisheries management. Proximate composition is a widely used tool for obtaining this level of information but is time consuming and requires homogenization of the entire fish, limiting the ability to obtain additional information from the same individual. Exploratory chemical component analysis of differing body regions of age‐1 (215‐290‐mm) striped bass Morone saxatilis suggests that the abdominal wall (belly flap) is an appropriate surrogate for estimating whole‐body proximate composition. Belly flaps showed strong linear relationships with total lipid composition (R2 = 0.91) and moisture (R2 = 0.82) but were more variable with respect to protein (R2 = 0.22) and ash (R2 = 0.26). Equations derived from these linear relationships allowed for accurate estimation of total‐body energy, water, lipid, dry mass, fat‐free dry mass, and protein (R2 &gt; 0.89). Strong linear relationships were also found for belly flap lipid and moisture and the same components measured in fillets (lipid: R2 = 0.82; moisture: R2 = 0.73). We conclude that sampling an otherwise unused portion of the fish can provide precise chemical compositional information without sacrificing product and can allow for additional information to be obtained from the same organism.

Sorption and desorption of non‐ionic herbicides onto particulate organic matter from surface soils under different land uses

SummaryIn vegetative filter strips used to intercept pesticides present in run‐off, particulate organic matter derived from the vegetation plays an important function in pesticide sorption processes, because it accumulates at the soil surface and quickly responds to changes in land use. Two herbicides with contrasted properties: isoproturon, moderately hydrophobic (log Kow= 2.5), diflufenican, strongly hydrophobic (log Kow= 4.9), and isopropylaniline, a metabolite of isoproturon, were used to characterize the sorption and desorption properties of POM originating from soils under three different land uses: a cropped plot under conventional wheat/maize rotation, an adjacent 10‐year‐old grassed strip and a nearby 80‐year‐old oak/chestnut forest. Chemical structural composition information obtained from solid‐state 13C CPMAS NMR and estimation of hydrophobicity from contact angle measurements were used to explain the different sorption capacities of POM according to their size and origins. Sorption of isoproturon and diflufenican increased with hydrophobicity of POM, which was greater in the forest soil. Aromaticity of POM was positively correlated to sorption coefficients (Koc). Desorption of the more hydrophobic compounds, diflufenican and isopropylaniline was weak for all POM fractions, regardless of their origin and size. On the other hand, desorption of isoproturon depended on land use and POM characteristics. The sorption capacities of POM were not only controlled by their chemical composition, but also by their size, due to a greater number of sorptive sites related to a greater surface area with decreasing particle‐size.

Effects of micropore development on the physicochemical properties of KOH-activated carbons

Effects of micropore development through varying the KOH/char ratio on the porous, electrochemical, electronic, and adsorptive properties for corncob-derived activated carbons (ACs) prepared by means of the KOH activation method were systematically compared. The pore properties of ACs, including BET surface area, total pore volume, micropore volume ratio, bulk density, and product yield based on the raw material were investigated to gain an understanding for the influence of KOH dosage on the pore development. Element analysis and temperature-programming desorption (TPD) were used to obtain the information of chemical composition and surface oxygen functional groups on ACs in order to propose the reaction mechanism of KOH activation. Based on the pore development, KOH-activated carbons can be classified into two groups: a combination of physical activation and chemical KOH etching at low KOH/char ratios (0.5–2) as well as chemically uniform etching at high KOH/char ratios (≥3.0). From the adsorption study for five organics with molecular weights varying from 129 to 466 g/mol, the specific adsorption capacity of ACs for organics is independent of their specific surface area. The specific capacitance of ACs reached a maximum as the KOH/char ratio was equal to 3, attributed to a compromise between the specific surface area and electronic resistance of ACs.