Removal of methylene blue from aqueous media using activated carbon web

Activated carbon web is prepared by controlled pyrolysis of acrylic fibrous waste under the layer of charcoal using physical activation in high-temperature furnace. The carbonization was carried out at 1200 °C under different heating rate (i.e. 150 to 450 °C h^?1) with different holding time (i.e. 0 to 60 min) to decide optimum pyrolysis parameters. The heating rate of 300 °C h^?1 with no holding time revealed higher specific surface area of 280 m² g^?1. The prepared activated carbon web was later employed as adsorbent for removal of methylene blue from aqueous media. The effect of initial dye concentration, adsorbent dosage, stirring speed, and pH of solution was studied. The obtained results were later compared with adsorption isotherms (i.e. Langmuir and Freundlich). The Freundlich model was found to fit closely with results due to heterogeneous adsorption of dye molecules. Finally, virgin activated carbon and dye adsorbed activated carbon were tested for desorption behavior using differential scanning calorimetry and thermo gravimetric analysis. The significant reduction in desorption enthalpy from 172.46 to 52.43 J g^?1 is attributed to less adsorption energies of dye molecules on the surface of activated carbon due to nonhomogeneous distribution of active sites.     

A comparative study of titrimetric and gravimetric methods for the determination of organic carbon in soil

Two gravimetric procedures for determining carbon in soil, one a dry combustion method and the other a wet oxidation method, were compared with seven variants of the titrimetric method, all based on titrimetric determination of the dichromate consumed when soil is heated with dichromate and acid. The coefficients of variation of the methods were, as percentages: dry combustion, 0.76; wet combustion, 1.1; Tinsley I, 1.3; Tinsley II, 1.8; Tinsley III, 0.8; Anne, 1.3; Mebius, 1.8; Walkley and Black, 1.6 and Tyurin, 8.5. Taking the dry combustion method as standard, the percentage recovery of organic carbon from 22 soils was 99 for wet combustion, 95 for Tinsley I, 95 for Tinsley II, 97 for Tinsley III, 93 for Anne, 95 for Mebius, 77 for Walkley and Black and 93 for the Tyurin method. A variant of the Tinsley method (Tinsley III) is proposed as a quick procedure when the accuracy of dry combustion is not essential.     

Gravimetric determination of tannins and their correlations with chemical and protein precipitation methods

Abstract. A method for gravimetric determination of tannins based on binding with insoluble polyvinylpyrrolidone (PVP) is presented. The gravimetric method gives the absolute amount of tannins and avoids problems of standards associated with spectrophotometric methods. The method was applied to nine browse and tree leaves. The values obtained correlate significantly with tannins determined spectrophotometrically, protein precipitation capacities and protein precipitable phenotics. This method together with other tannin assays will be useful in nutritional studies. The present study also demonstrates the different behaviour of tannic acids from different commercial sources towards PVP suggesting the presence of different moieties in tannic acids from different commercial sources and even among batches from the same source thereby affecting the results obtained using the spectrophotometric methods. Use of well-defined tannic acid as a standard in spectrophotometric methods is suggested which will allow meaningful comparison of values obtained from different laboratories.     

In-situ characterization of soil-water content using gas-phase partitioning tracer tests: field-scale evaluation

Field-scale tests were performed to evaluate the effectiveness of the gas-phase partitioning tracer method for in-situ measurement of soil-water content. The tracer tests were conducted before and after a controlled infiltration event to evaluate performance at two water contents. Nonpartitioning (sulfur hexafluoride) and water-partitioning (difluoromethane) tracers were injected into the test zone, and their effluent breakthrough curves were analyzed using the method of moments to calculate retardation factors for difluoromethane. Soil-water contents estimated using the tracer data were compared to soil-water contents obtained independently using gravimetric core analysis, neutron scattering, and bore-hole ground penetrating radar. For the test conducted under drier soil conditions, the soil-water content estimated from the tracer test was identical to the independently measured values of 8.6% (equivalent to water saturation of 23%). For the test conducted under wetter soil conditions, the tracer test derived soil-water content was 81% of the independently measured values of 12.2% (equivalent to water saturation of 32%). The reduced efficacy at the higher soil-water content may reflectthe impact of advective and/ or diffusive mass transfer constraints on gas-phase transport. The results presented herein indicate that the partitioning tracer method is an effective technique to measure soil-water content at the field scale, especially for sites with moderate to low soil-water contents.     

Determination of water activity of canned fish using gravimetric, hygrometric and psychrometric methods

The water activity ( a _w) of canned mackerel, tuna and sardine was determined using three methods: a gravimetric and two instrumental methods. The a _w values obtained by the gravimetric method, which only requires simple laboratory apparatus, were not significantly different from the values obtained by the other two methods, and can be used to determine high a _w values.     

A gravimetric adaptation of the filter paper press method for the determination of water-binding capacity.

A gravimetric adaptation of the filter paper press method for the determination of water-binding capacity in meat was developed and its sensitivity was compared to that of the conventional planimetric technique of the method. Both the gravimetric and planimetric techniques were applied to samples of cooked fish treated with various water binders. The mean results of the samples were grouped and compared using an analysis of variance. In all comparisons, the gravimetric data produced higher F-values than did the planimetric data for the same samples. This indicated greater senstivity for the gravimetric technique.     

Evaluation of methods for measuring particulate matter emissions from gas turbines

The project SAMPLE evaluated methods for measuring particle properties in the exhaust of aircraft engines with respect to the development of standardized operation procedures for particulate matter measurement in aviation industry. Filter-based off-line mass methods included gravimetry and chemical analysis of carbonaceous species by combustion methods. Online mass methods were based on light absorption measurement or used size distribution measurements obtained from an electrical mobility analyzer approach. Number concentrations were determined using different condensation particle counters (CPC). Total mass from filter-based methods balanced gravimetric mass within 8% error. Carbonaceous matter accounted for 70% of gravimetric mass while the remaining 30% were attributed to hydrated sulfate and noncarbonaceous organic matter fractions. Online methods were closely correlated over the entire range of emission levels studied in the tests. Elemental carbon from combustion methods and black carbon from optical methods deviated by maximum 5% with respect to mass for low to medium emission levels, whereas for high emission levels a systematic deviation between online methods and filter based methods was found which is attributed to sampling effects. CPC based instruments proved highly reproducible for number concentration measurements with a maximum interinstrument standard deviation of 7.5%.     

浅谈硫酸根的重量法和容量法测定

硫酸根的重量法和容量法测定各有所长,当硫酸根小于1.00%其容量法测定可以替代重量法,只要相应条件控制好,一样可以获得精确的结果.     

33—A GRAVIMETRIC TECHNIQUE FOR DETERMINING THE MEAN FIBRE DIAMETER OF WOOL

A method is presented for determining the diameter of wool gravimetrically by using fibre snippets instead of full-length fibres. A quantity of the snippets is weighed and then counted with an electronic particle-size analyser (a Coulter Counter). The average length of snippets is obtained by measuring the length of a small random sample. The product of the average snippet length and the number of snippets present in the weighed sample provides an estimate of the total length of the weighed snippets. Hence their mass per unit length can be calculated, and, if the fibre density is known, the r.m.s. diameter can also be determined.

For continuous-filament nylon, the method gives excellent agreement with diameter values obtained by a conventional gravimetric technique. For combed wool, the snippet gravimetric diameter is always less than the projection-microscope diameter, corrected to r.m.s. Some of this difference is attributed to reentries in the wool-fibre surface.     

Optimizing municipal solid waste combustion through organic and elemental carbon as indicators

The temperature, redox conditions, and residence times of the solid waste on the grate and of the raw gas in the secondary combustion zone determine the mineralization processes of organics in municipal solid waste incinerators. An improved knowledge of the influence of these factors on the incineration process might help to optimize incinerators with regard to mineralization efficiency of organics. This paper presents a method for investigating the influence of process parameters on mineralization of organics to CO2 by using the elemental carbon (EC) and organic carbon (OC) concentrations in the solid residues as indicators. The results obtained by experiments in full-scale incinerators show that the EC concentration in these residues is a good indicator of oxygen supply, whereas the OC/EC ratio is a good indicator of temperature in and above the furnace bed. Very effective burnout of the bottom ash up to 0.95 g of TOC (EC + OC) per kilogram of dry matter (DM) and of the electrostatic precipitator (ESP) ash up to 0.24 g of TOC per kilogram of DM was achieved in a full-scale incinerator.     

Qualification of a precise and easy-to-handle sweat casting imprint method for the prediction and quantification of anti-perspirant efficacy

A time‐ and cost‐effective sweat casting method using the forearm as test site to assess the efficacy of several anti‐perspirant formulations with a low number of test subjects has been evaluated and qualified. The imprint sweat casting method is based on a 2‐component silcone‐imprint technique to measure the efficacy of more than eight products in parallel with the same test subject. In studies using aluminum chlorohydrate (ACH) formulations as test anti‐perspirants, a clear‐cut correlation could be demonstrated between sweat gland activities measured by the imprint method and gravimetric measurement of sweat gland activities. Concentration‐dependent inhibition of sweat gland activity could be observed with the imprint technique up to an ACH concentration of 15%, and all formulations containing 2% ACH or above resulted in statistically significant reduction of sweat gland activity (P < 0.001) when compared with untreated control areas. Furthermore, the SDs of individual studies using the imprint technique were in a range of ±20% of sweat gland activity, which can be regarded rather low for in vivo measurements of a complex process like sweat secretion. A group‐wise comparison between the measurements of anti‐perspirant activity as determined by the imprint protocol and the Food and Drug Administration (FDA) Guideline compliant gravimetric hot‐room protocol revealed that the test results for anti‐perspirant activity obtained with the imprint protocol are similar to those obtained with the hot‐room protocol. Moreover, the data generated with the imprint protocol have a high predictive value for the outcome of a later guideline‐compliant hot‐room test. As the imprint casting method tends to be a little more sensitive for formulations with low anti‐perspirant activity, and seems to be associated with less interassay variability than the standard gravimetric hot‐room test, the imprint casting method may select products which later fail to pass the standard gravimetric hot‐room test. Meanwhile the imprint sweat casting has proven to be a robust method useful to support efficacy‐oriented product development. Therefore, in later stages of utilization it might even evolve into an efficient claim substantiation tool.     

Modeling kinetics of Cu and Zn release from soils

Kinetics of Cu and Zn release from soil particles was studied using two surface soils with a stirred-flow method. Different solution pH, dissolved organic matter (DOM) concentrations, and flow rates were tested in this study. A model for kinetics controlled sorption/desorption reactions between soils and solutions was globally fit to all experimental data simultaneously. Results were compared to a model that assumes local instantaneous equilibrium. We obtained one unique set of model parameters applicable to different pH, dissolved organic carbon (DOC), and flow conditions. We included DOM complexation of copper ions, which decreased their sorption. The effect of pH was included by assuming proton competition with metal ions for binding sites on soil particles. These results provide the basis for developing predictive models for metal release from soil particles to surface waters and soil solution.     

New starch preparations resistant to enzymatic digestion

BACKGROUND: New starch preparations were produced by thermolysis of potato starch in the presence of inorganic (hydrochloric) and organic (citric and tartaric) acids under controlled conditions. The starch preparations were physicochemically and structurally characterised and analysed for their resistance to enzymatic digestion in vitro. RESULTS: The content of resistant fraction in dextrin D1, obtained by heating starch acidified with hydrochloric and citric acids, determined by the AOAC 2001.03 and pancreatin‐gravimetric methods was similar (～200 g kg^?1). In the case of dextrin D3, obtained by heating starch acidified with hydrochloric and tartaric acids, the result of determination by the pancreatin‐gravimetric method was almost four times higher than that obtained with the AOAC 2001.03 method. The enzymatic tests revealed that dextrin D3 obtained with excess tartaric acid can be classified as RS4, which can only be partially determined by enzymatic‐gravimetric methods. Tartaric acid at high concentration had a significantly stronger influence on starch hydrolysis than citric acid. This was confirmed by chromatographic analysis of dextrins and chemical investigation of the reducing power. CONCLUSION: The results confirmed the possibility of applying dextrins, prepared under specific conditions, as soluble dietary fibre. Copyright © 2011 Society of Chemical Industry     

Comparison and evaluation of methods for including nitrate in the total nitrogen determination of soils

A semimicro modification of the Olsen method was developed to include nitratenitrogen in the total soil nitrogen determination by the standard semimicro-Kjeldahl method. The modified method was found to include nitrate-nitrogen effectively from standard nitrate solutions and soils. It was significantly superior to the commonly used salicylic acid method, which was found to give incomplete recovery of nitrate-nitrogen. In addition, changes in a number of experimental conditions such as amounts of water present and concentrated sulphuric acid used did not affect the results obtained by the modified Olsen method. In comparison with the recently recommended Raney catalysts for nitrate-nitrogen inclusion in the total nitrogen determination of fertilisers, preliminary results using standard nitrate solutions and following their additions to the soil indicate that reduced iron was comparable. Results obtained using glucose as a reducing agent in the standard semimicro-Kjeldahl method suggest that some nitratenitrogen was included by soil organic matter in the normal total soil nitrogen determination.     

Enhancing phenanthrene biomineralization in a polluted soil using gaseous toluene as a cosubstrate

Laboratory experiments were conducted to study the potential of adding gaseous toluene, as a readily degradable carbon source, to enhance phenanthrene mineralization in polluted soil (1,000 mg/kg(dry soil)) aged for 400 days. Experiments were conducted in 0.5-L column reactors packed with a mixture of (80:20 w(wet)/w(wet)) spiked soil and vermiculite and fed with 1 g m(-3)reactor h(-1) toluene load in air. Removal efficiencies of 100% for toluene and greater than 95% for phenanthrene were obtained in 190 h. Evolved CO2 showed that phenanthrene mineralization increased from 39% to 86% in columns treated with gaseous toluene. Phthalic acid was identified as the principal soluble intermediate, which accumulated when no toluene was added. Increased phenanthrene uptake and mineralization with toluene can be attributed to increased biomass and the induction of enzymes involved in the intermediate mineralization. In microcosm experiments, phthalic acid mineralization increased from 19% to 81% within 50 h in the presence of toluene. Experiments with 14C-labeled phenanthrene confirmed the enhancement of phenanthrene mineralization from 45% to 83% in 385 h with toluene as a second carbon source. The results indicate thatthe addition of an appropriate gaseous cosubstrate could be an adequate strategy to enhance mineralization of PAHs in soil.     

Densitometric determination of the fat content of milk and milk products

An automatable method for determining the fat content of milk and milk products was developed using a precise densitometer based on the principle of the resonant frequency U-tube oscillation. The sample is first decomposed with hydrochloric acid and the fat extracted with hexane. The density of the fat/hexane solution obtained varies with the fat content of the sample. Milk, cream and cheese samples were analysed. The mean values from the densitometric determination of the fat content did not differ from the mean values obtained by the corresponding gravimetric reference methods.     

湖南省主要植烟区域土壤有机氮矿化特性研究

以湖南主要烟区植烟土壤为研究对象,采用Warning 淹水培养法,对植烟土壤进行矿化培养试验,深入研究不同烟区土壤有机氮矿化特性。结果表明,湖南省植烟土壤有机氮矿化速率均表现为前期较快,后期缓慢。湘南、湘中、湘西植烟土壤有机氮矿化积累量、矿化速率、矿化势相差较大,且均表现为“湘中>湘南>湘西”。矿化氮与全氮、有机质线性回归结果显示,与矿化氮含量密切相关的依次为活性有机碳>全氮>有机质>腐殖质碳。总体表明,活性有机碳与矿化氮量密切相关,是矿化的主体。     

Sorption isotherms of lupine at different temperatures

Sorption isotherms of lupine at 25, 35, 45 °C were determined. Adsorption and desorption data were obtained at each temperature and no hysteresis was observed. The experimental method was a gravimetric static method. The results were fitted by the Guggenheim–Anderson–deBoer model. The monolayer moisture content (parameter of the model) was constant in the range of temperatures employed with a value of 0.0497 dry basis (d.b.). The isosteric heat of lupine was evaluated at several moisture content using the Clausius–Clapeyron equation and below a moisture content of 0.15 (d.b.) increases appreciably up to around 20 kJ/mol at very low moisture content.     

Activated carbon fiber cloth electrothermal swing adsorption system

Capture and recovery of hazardous air pollutants (HAPs) and volatile organic compounds (VOCs) from gas streams using physical adsorption onto activated carbon fiber cloth (ACFC) is demonstrated on the bench-scale. This system is regenerated electrothermally, by passing an electric current directly through the ACFC. The adsorbate desorbs from the ACFC, rapidly condenses on the inside walls of the adsorber, and then drains from the adsorber as a pure liquid. Rapid electrothermal desorption exhibits such unique characteristics as extremely low purge gas flow rate, rapid rate of ACFC heating, rapid mass transfer kinetics inherent to ACFC, and in-vessel condensation. An existing system was scaled up 500%, and the new system was modeled using material and energy balances. Adsorption isotherms using methyl ethyl ketone (MEK) and ACFC were obtained while electricity passed through the ACFC and at temperatures above MEK's boiling point. These isotherms agreed within 7% to Dubinin-Radushkevich modeled isotherms that were extrapolated from independently determined gravimetric measurements obtained at lower temperatures. Energy and material balances for the electrothermal desorption of organic vapors and ACFC agree to within 7% of experimentally measured values. These results allow the modeling of electrothermal desorption of organic vapors from gas streams with in-vessel condensation to optimize operating conditions of the system during regeneration of the adsorbent.     

Carbon suboxide, a highly reactive intermediate from the abiotic degradation of aromatic compounds in soil

The formation of volatile compounds during abiotic degradation processes of aromatic compounds in soil has been the subject of many experimental studies but should be examined further. In this context, the present work investigates the natural formation of carbon suboxide using the model compounds catechol and 3,5-dichlorocatechol and also a soil sample from a peat bog. The measurements were performed with a purge and trap GC/ MS system following various optimization steps. Under certain conditions, we obtained 16.7 ng of carbon suboxide from a 250 mg soil sample. We also found that the formation of carbon suboxide requires a definite activation energy and that it is rather short-lived in the natural environment. A subsequent reaction to malonic acid is expected in the presence of water. It is shown that iron-(III), hydrogen peroxide, and chloride are prerequisites for its formation. Experimental parameters for the highest yield of carbon suboxide depend on the precise molecular structure of the model compound or on the individual soil sample, respectively. The presented results point to a new degradation process for aromatic compounds in soil.