Batch Extraction Tests Research Articles

Rapid semi-continuous calibration and field test of membrane-enclosed silicone collector as passive water sampler

The new membrane-enclosed silicone collector (MESCO) was, in two different configurations with respect to the thickness of low-density polyethylene membrane used, subject to serial batch extraction tests to obtain (preliminary) sampling rates for estimating water concentrations of selected chlorinated organic compounds and polycyclic aromatic hydrocarbons. This rapid calibration procedure is simple to implement compared to experiments in a flow-through apparatus and yielded reasonable sampling rates in the range of 50 μL–2 mL per hour for the compounds tested. The new MESCO formats were also exposed for 28 days in the polluted creek to test their field performance. For priority contaminants of special interest, α-hexachlorocyclohexane and hexachlorobenzene, the time-weighted average concentrations derived from the freshly calibrated sampling devices agree well with those obtained by conventional water analysis of spot samples.

The application of batch extraction tests for the characterisation of solidified ferro alloy waste products

Leach testing is arguably the best indicator of the effectiveness of pre-landfill treatments, including solidification/stabilisation (S/S), in reducing mobility of waste constituents. The results of leach tests can, however, also be interpreted to provide an understanding of the mechanisms via which toxic species are retained in the S/S product. An understanding of retention mechanisms contributes to the development of improved waste treatment systems. In this paper, we explore the applicability of four extraction tests, Pore Solution Expressions, the TCLP, the Equilibrium Extraction (EE) and the Sequential Chemical Extraction (SCE) for providing a description of the mechanisms of containment within an S/S product. The waste materials explored here are ferrochrome dusts with high levels of metals including Cr and Zn. The errors in results from the pore solution expressions and sequential chemical extractions were too high to draw any quantitative conclusions, although some qualitative comments could be made. The latter observations, however, were consistent with those from the other two tests, and together these build a comprehensive picture of the S/S products. For these specific products, it is suggested that a small amount (∼1%) of the Cr is Cr(VI) which is readily mobile, approximately 5% is Cr(III) which is mobile under acidic conditions and the remainder is a stabile chromite which is not readily mobile. For Zn, however, roughly equal proportions are contained as a species (possibly Zn(OH) 2) whose release is pH dependant, and as a stable, immobile species on the surface of the dust particles.

Rice Bran Oil Extraction in Sri Lanka: Data for Process Equipment Design

Rice bran oil is widely used in pharmaceutical, food and chemical industries due to its unique properties and high medicinal value. In this study, extraction of rice bran oil from various brands of rice bran available in Sri Lanka has been studied and data necessary for extraction, equipment design and process predictions have been determined. Experiments were conducted using a Soxhlet apparatus and a pilot-scale leaching unit, to extract rice bran oil using hexane as the solvent. The key factors controlling the extraction and optimal operating conditions were identified. Analysis of free fatty acid content in the extracted oil showed that steaming is the most effective method of bran pre-treatment. Bran obtained from parboiled paddy has a higher yield of rice bran oil compared with the raw rice bran, despite the oils darker colour. Linoleic, oleic and palmitic acids are the major fatty acid constituents in rice bran oil. Equilibrium data show no preferential adsorption of oil or solvent to the inert bran and approximately constant solid/solution ratios in the underflow raffinate streams. Batch extraction tests showed the rate of extraction decreases with time and the solution approaches saturation at an exponential rate. Mass transfer coefficient was obtained for the system.

Sequential extraction procedure in columns. Part 1: Development and description of a new method

A sequential extraction procedure was carried out in columns using reagents that are known to be reliable from batch tests. The intention was to distinguish between different chemical forms of iron and heavy metals in samples from reduced porous aquifers, which demands anaerobic conditions for the extraction procedure and the determination of small amounts of reactive mineral phases in a quartz dominated sediment system. By means of the developed method, anaerobic conditions can be guaranteed in the columns, which could not be realized to full satisfaction in batch tests that were carried out in a glove box. In order to distinguish between the fractions that were water soluble, exchangeable, bound to carbonates and bound to hydroxides, different reagents were pumped through the sediments and sampled after passage of the columns. Sediment samples of 10 kg each were investigated in this way. The extraction steps were known to be complete when analyses revealed that no further major and trace elements were leached out of the columns. This approach enabled well-adjusted amounts of reagents to be used. By means of the sequential extraction procedure in columns the composition of even small amounts of reactive mineral phases can be determined successfully, which contributes to a deeper understanding of the hydrogeochemical processes in aquifers. In batch tests this accuracy cannot be reached because of the surplus of the extraction solution in relation to the amount of sediment (higher solution-sediment ratio). Furthermore, larger samples are much more representative of the composition of the aquifers than smaller ones and the heterogeneity of the sediment does not limit the accuracy of the results as much as in batch tests. In addition, the technique of flushing sediment in a column is much more typical for the situation in an aquifer than suspending a few grams of a sample in the extracting reagents in batch extraction tests. In order to demonstrate the methodical improvements and field applications, the newly developed method was used to investigate the changing binding forms and mobility of iron and trace metals in samples from a lignite overburden dump, which are influenced by pyrite oxidation processes (acidification) followed by the addition of crushed limestone (neutralization) (see "Sequential extraction procedure in columns. Part 2: Application of a new method").

Removal of Aroclor 1016 from contaminated soil by Solvent Extraction Soil Agglomeration Process

This communication reports the results of a study to assess the suitability of the National Research Council of Canada's Solvent Extraction Soil Remediation (SESR) process to effectively remediate soils contaminated with PCBs. A series of small-scale batch extraction tests were carried out using a loamy clay soil sample spiked with Aroclor 1016. The variables examined included the effects of solvent type, water addition, agglomerate size, and extraction additives. Aroclor 1016 recovery rates for the SESR process were higher than those found for high shear agitation of soil slurries without agglomeration and Soxhlet extraction (93.9 ± 1.9, 90.6 ± 1.5 and 82.7 ± 0.9% respectively). A two-stage extraction process, with a series of three wash steps incorporated into the solid–liquid separation operation, produced a treated soil with an average Aroclor 1016 concentration of 49 ± 8 mg/kg on a dry weight basis (95.4 ± 2.4% removed). Key words: PCBs, soil remediation, agglomeration, solvent extraction.

The RCRA Toxicity Characteristic Leaching Procedure (TCLP): A Concept for a New Method

AbstractThe U.S. Environmental Protection Agency has committed to reexamining its use of the Toxicity Characteristic Leaching Procedure (TCLP). The TCLP was developed to support the Resource Conservation and Recovery Act (RCRA) Toxicity Characteristic (40 CFR 261.24) and to help predict whether toxic constituents of solid wastes would be mobilized upon their contact with municipal waste leachate. The method involves a batch extraction test in which wastes are exposed to an aqueous liquid designed to simulate the solvent properties of municipal waste leachates. The resulting extract (i.e., TCLP leachate) is analyzed for the presence of various organic and inorganic contaminants. This article presents a concept for a new method that addresses a number of critical design criteria. The concept is based on a preliminary method developed by the authors as part of a work group chaired by the American Society for Testing and Materials. 2001 © John Wiley & Sons, Inc.

Contamination of a calcareous soil by battery industry wastes. II. Treatment

This study evaluated treatment of a soil that was heavily contaminated by the disposal of waste from a Pb battery industry. The site was of interest from a remediation point of view, since the soil contained substantial quantities of calcareous material. Treatment involved extraction of the metals from the soil using aqueous solutions of EDTA (ethylenediaminetetraacetic acid). The impact of pH, EDTA concentration, and reaction time on the extent of leaching of Pb was evaluated. The leaching efficiency was found to be independent of pH over a range of values from 4 to 8.2. The leaching of Pb and Ca increased with EDTA concentration with 99% of the Pb removed at an EDTA dosage of 3.2 M/kg soil. The removal efficiencies of Cu, Cr, Cd, Ni, and Zn were consistently less than that of Pb; however, with their lower initial concentrations, acceptable levels were achieved for all metals except Cd. A two-reaction model was successfully used to describe the results of a batch extraction test. The results indicated relatively rapid extraction kinetics for a substantial fraction of the Pb contamination. Treatment of the liquid effluent from the soil treatment process with nano-level filtration indicated that both the EDTA and Pb were consistently removed at efficiencies greater than 98%. The nano-filtration process was not affected by pH over a range of values from 4.8 to 7.6.Key words: soil washing, Pb, EDTA, pH effect, kinetic, leachate treatment.

The RCRA Toxicity Characteristic Leaching Procedure (TCLP): A Concept for a New Method

The U.S. Environmental Protection Agency has committed to reexamining its use of the Toxicity Characteristic Leaching Procedure (TCLP). The TCLP was developed to support the Resource Conservation and Recovery Act (RCRA) Toxicity Characteristic (40 CFR 261.24) and to help predict whether toxic constituents of solid wastes would be mobilized upon their contact with municipal waste leachate. The method involves a batch extraction test in which wastes are exposed to an aqueous liquid designed to simulate the solvent properties of municipal waste leachates. The resulting extract (i.e., TCLP leachate) is analyzed for the presence of various organic and inorganic contaminants. This article presents a concept for a new method that addresses a number of critical design criteria. The concept is based on a preliminary method developed by the authors as part of a work group chaired by the American Society for Testing and Materials. 2001 © John Wiley & Sons, Inc.

Immobilization of mercury(II) in contaminated soil with used tire rubber

The effectiveness of used tire rubber for immobilizing Hg(II) in a contaminated soil was evaluated using batch extraction and field rainwater leaching tests. The contaminated soil was prepared using a clay-loam spiked with mercury oxide or mercury chloride to yield a Hg(II) content of 300 mg/kg. When the contaminated soil was treated with 4% of tire rubber, Hg(II) concentration in an acetic acid leachate was reduced from 3500 ppb down to 34 ppb. Hg(II) concentration in the initial rainwater leachate was reduced from 84 ppb for untreated soil to 1.2 ppb for the rubber-treated soil. After 8 months of rainwater infiltration in the field, Hg(II) concentration decreased to less than 0.2 ppb for the treated soil. The rubber-treatment inhibited the evolution of metallic Hg 0 from the spiked soil samples possibly by retarding the reduction of Hg(II) to Hg 0. Batch extraction and adsorption results indicated that the rubber had high adsorption capacity for Hg(II) when pH values were between 2 and 8.

Trona Mineral Grade Sodium Carbonate As A Process Aid For The Hot Water Process

Abstract Trona is a mineral which contains over 90% of a mixture of sodium carbonate and bicarbonate. It is a raw material used in the production of sodium-containing substances. The batch extraction test results showed that the processibility curves obtained using trona as the process aid for the recovery of Athabasca bitumen from mined oil sands using the hot water process were similar to those for sodium carbonate. To achieve an optimum recovery similar to that by sodium hydroxide, it required a dosage of trona three to four times that of sodium hydroxide. However, since trona is much cheaper than sodium hydroxide and chemical grade alkalines, it makes a promising substitute for sodium hydroxide in the hot water process. Introduction Sodium hydroxide (NaOH) has been the process aid of choice, used in the hot water extraction process. A plant in Fort Saskatchewan has been the sole supplier of NaOH to Syncrude. At this plant, NaOH is a co-product of the chlor-alkali process(l) in chlorine production which is primarily used in the pulp and paper industry. In recent years, many paper mills in Western Canada have adopted non-chlorine based processes due to growing environmental concerns. The declining demand for chlorine has caused a significant reduction in NaOH production and, as a result, the price has escalated. Attempts have been made in the past to seek NaOH replacements. Chemicals which have been tested as process aids in the hot water extraction process include sodium carbonate (Na2C03), sodium bicarbonate (NaHC03), sodium silicate (Na2Si03), and ammonium hydroxide (NH40H)(2,3). These inorganic bases, though not as strong as NaOH, have been shown to be quite effective. Optimum recoveries using these process aids were comparable to that with NaOH, although optimum dosages of these process aids were about two to three times greater than that of NaOH. Economic studies have also been carried out by Syncrude(2) comparing the costs of using NaOH, Na2C03, and NaOH/Na2C03 mixture as process aids. Based on the price ratio of Na2C03 to NaOH as 3/4, it was concluded that the NaOH/Na2C03 mixture could be a viable option. On-site NaOH production via the causticizing process was also considered; this utilizes Na2C03 (soda ash) and calcium hydroxide (quicklime) as feedstocks. However, from an economic point of view, these proposals do not provide the incentive for commercial application since the price of chemical grade Na2C03 is not appreciably lower than that of NaOH. It becomes apparent that the realistic options of substituting or producing NaOH with chemical grade compounds are quite limited. This paper summarizes briefly a recent development on NaOH production, which prompted us to investigate the possibility of substituting NaOH with a raw material sometimes used in NaOH production. Trona Trona is a natural mineral which consists mostly of Na2C03 and NaHC03. The typical composition of trona is shown in Table I. It is used as the raw material for commercial production of sodium-containing compounds, including NaOH(1). It has also been considered as a reagent for scrubbing sulphur dioxide in spray driers(4).

Solvent washing of PCP contaminated soils with anaerobic treatment of wash fluids

ABSTRACT: A solvent washing procedure for the removal of pentachlorophenol (PCP) from contaminated soils is presented. This procedure can be used in both in‐situ and above‐ground soil washing applications. The in‐situ solvent washing (flushing) of soil was simulated by continuously flushing solvent through a packed bed of soil until the effluent PCP concentrations decrease to below the detection limit. The aboveground (ex‐situ) soil washing was simulated by batch tests (reverse isotherms) conducted on PCP contaminated soil. Acetone was found to be less effective than ethanol in flushing PCP from contaminated soil. Soil solvent flushing was evaluated for 20 × 40, 60 × 80, and 100 × 140 U.S. Mesh size soil fractions loaded with 100 ppm of PCP. The flushing solvent, 95% ethanol, was applied at three different flow rates. Lower solvent flow rates were more effective, for the same solvent throughput, than higher flow rates in extracting PCP thus suggesting that desorption kinetics was rate limiting. The 20 × 40 U.S. Mesh soil was flushed with various ethanol and water mixtures; the 75% ethanol solution removed more PCP than other mixtures. Batch extraction tests, conducted on 20 × 40, 100 × 140 U.S. Mesh size soil and the clay fraction of the same soil, revealed that 50% and 75% ethanol and water solutions consistently removed the highest amounts of PCP. The wash fluids were fed to an expanded‐bed anaerobic granular activated carbon (GAC) bioreactor, where the PCP content of the wash fluid was biodegraded and the ethanol served as the primary substrate.

In Support of "The Physical Chemistry of the Hot Water Process"

Abstract Comments raised by Jan Czarnecki and Russel Smith on " The Physical Chemistry of the Hot Water Process" reveal the need for the authors of the original paper(l) to explain in more detail their rationale for developing the stability diagram to predict fines stability during extraction. The first comment relates to the selection of an energy barrier of -400 kT as a reasonable level to differentiate between a stable and coagulated system, In the paper, the authors dearly explained their reasons for adopting the 400 kT level based on a combination of mathematical calculations and batch extraction unit experiments. In view of their explanation, the selection of the transition region from 0 to 400 kT could be regarded as a tit parameter for experimental data rather than a critical level based solely on flocculation kinetics under conditions dominated by Brownian motion. In recognition of the possible misinterpretations that could be made with respect to the critical energy barrier level, in a subsequent paper(2) in which the same model was used to explain the deterioration in processing behaviour due to aging, the authors described the transition region in the following manner. " To allow for the uncertainties in calculating the net interaction between particles, a transition region of 0 to 400 kT was identified in the batch extraction test. In reality, the transition region represents the uncertainty about whether a significant portion of the particles under consideration are dispersed or coagulated". If in fact, the selection of 400 kT is the basis upon which the validity of the conclusions in the paper is judged, a single value between say 0 and 20 kT could be defined as being the demarcation between a stable and a coagulated regime. Identification of the position of that single line on the stability diagram covering the range of panicle sizes and types that are found typically in oil sand would regenerate a zone of uncertainty that is similar to the one in the original diagram. However, by doing so, the authors would be ignoring the effect of hydrodynamic forces on coagulation. This leads to the second point raised by Czarnecki and Smith in which they claim that hydrodyarnic forces cannot drive particles together across a 400 kT energy barrier for the s}'stem under examination. In 1983, Chia and Somasundaran reported enhanced strong agitation between anatase and calcite particles under conditions of intense agitation(3). Rather than interpreting this observation soleIy in terms of increased collision frequency, they related the magnitude of the hydrodynamic forces due to agitation to the net repulsive forces calculated from DLVO theory. The calculations taken from Chia and Somasundaran support our belief that the barrier height to coagulation in our agitated system can exceed the critical level of 20 kT proposed by Czarnecki and Smith. In these calculations, we will cover a range of particle radii from 1 to 10 µm (with a desity of 2.6 g/cm3), conditioning slurry viscosities of 1 to 10 stokes and power inputs (based on BEU measurements) of 10 to 30 N.m/sec.

Fourier Grain Shape Analysis as a Tool for Indicating Batch Recoveries of Bitumen from Athabasca Tar Sands: ABSTRACT

Effects of weight percent fines have been considered in the past as important factors in controlling the recoveries of bitumen from tar sands using batch extractors. However, in the marine sands of the Athabasca deposit, fines break down as a predictor of batch recovery; in some places even low fines tar sands do not yield acceptable batch bitumen recoveries. It was predicted that a sand unit high in rough-surfaced, diagenetically altered grains would yield low primary bitumen recovery. Scanning electron microscopy of the solids from batch extraction tests revealed that quartz grains with very rough, pitted, and overgrown surfaces retain bitumen. (These solids appear to be transported preferentially with the bitumen to froth and secondary tailings.) Grains with smooth sur aces were found to be dominant in primary tailings. Fourier grain-shape analysis was employed to identify tar sand shape types since scanning electron microscopy inspections are time-consuming and expensive. Five grain shape families were so identified and verified by SEM. Two types of grains unaltered by diagenesis are very fresh, rounded, sub-aerially abraided grains, and fresh, angular grains with concoidal fractures. Three other grain shape families represent particles whose surfaces were strongly modified by diagenesis. The diagenesis was found to be primarily overgrowth: (1) rough silica plastering with a sponge-like appearance, producing high surface areas; (2) silica plastering with multiple crystals; and (3) complete simple overgrowth. Fourier grain-shape analysis yields the proportion of high surface area grains in 900 grain samples taken from marine sand intervals of 3 cores. That proportion, plotted versus weight percent primary recovery by batch extraction, indicates that when the proportion of high energy grains exceeds 40%, primary recoveries were less than 80 wt. %. (Primary recovery, in contrast, shows no relationship to weight percent fines for these marine sands and cannot be used as a batch recovery indicator.) The results suggest the feasibility of predicting recovery in advance of mining, thus permitting adjustments to mining/extraction strategies. It must be kept in mind, however, that extrapolation of bitumen recovery results from bench-scale batch tests to large-scale continuous units is not straightforward. End_of_Article - Last_Page 549------------

Extraction of sugar from cane in the diffusion process

The development of a mathematical model to represent the extraction of sugar from sugar cane is described. The model which has previously been applied to laboratory batch extraction tests is based on the assumption that extraction occurs according to two parallel first-order processes, corresponding to displacement-washing and diffusional processes. The model is formulated for the unsteady state extraction of sugar from a packed bed of prepared cane and is shown to represent accurately experimental results obtained in a fixed bed pilot plant diffuser. Comparison of the parameter values estimated from this data with the results of the laboratory extraction tests shows that extraction is generally more efficient in a well-mixed environment than a packed bed. Results from the pilot plant diffuser show evidence of the effects of liquid hydrodynamics in the bed which are interpreted in tenns of liquid holdup and liquid-solid contacting.

Application of Amine and Phosphonate Extractants to Transplutonium Element Production

The Tramex process, in which trivalent actinides are extracted into tertiary amine hydrochloride from concentrated lithium chloride solution, was developed for isolation of transplutonium elements from irradiated High Flux Isotope Reactor targets. Tests made in laboratory scale mixer-settlers gave americium losses of about 0.01% and fission product decontamination factors of equal to or greater than 104. Nickel was the only contaminant that followed the transplutonium elements through the Tramex process. No serious radiation induced effects were noted in 1- to 10-ml batch extraction tests at activity levels up to the proposed processing level of 10 w/liter. A process was developed for splitting transplutonium elements into two fractions. Transcurium elements are extracted into rnono-2-ethyl-hexyl phenyl phosphonic acid from dilute hydrochloric acid while americium-curium and nickel contaminant from the Tramex process remain in the aqueous phase. Demonstration in a 10-ml batch countercurrent extraction with simulated feed containing tracers gave a californium loss of about 0.1% and an americium decontamination factor of 10/sup 3/. Important variables for both extraction processes are discussed. (auth)