High-temperature Distillation Research Articles

Chiral separation by enantioselective inclusion complexation-organic solvent nanofiltration

Enantioselective inclusion complexation (EIC) is a promising technique for chiral resolutions which, since it is not restricted to proton transfer interactions, can in principle be used to resolve compounds with almost any functional group. However, an outstanding difficulty with EIC is the separation of enantiomer from the enantioenriched solid complex, typically performed by distillation. This limits EIC to enantiomers with appreciable volatility, and even for these it would be difficult to operate at large-scale due to high temperature distillation, with concomitant problematic heat transfer and vacuum conditions. Here we report for the first time a novel enantioseparation process which combines the highly enantioselective nature of inclusion complexation with the subsequent separation of enantiomers from a chiral host using solvent decomplexation and organic solvent nanofiltration (OSN). In our proposed process (Fig. 1), a racemate is added to a chiral host suspended in a resolution solvent. The S-enantiomer enantioselectively co-crystallizes with the chiral host while the R-enantiomer remains in the liquid (Step A). Nanofiltration of the resulting resolution suspension elutes the R-enantiomer (Step B), retaining the solid chiral host and the solid chiral host-Senantiomer complex. A decomplexation solvent is then added to dissolve and dissociate the complex into S-enantiomer and host (Step C). This solution is then nanofiltered to elute the S-enantiomer, while the soluble host is retained by the membrane (Step D). The dissolved host is then returned as a suspension in resolution solvent to the next cycle of resolution. This is achieved by exchanging the decomplexation solvent for the resolution solvent via diafiltration (Step E). Since chiral hosts are used in stoichiometric quantities, their recovery and multiple reuse is a further key advantage of separation by OSN.

Refinement of Weak Acid Dissociable (WAD) Method for Measuring Weak Metal Cyanide Complexes in Aqueous Samples

The primary objective of this study was to correct deficiencies that had been identified in the current weakacid dissociable (WAD) cyanide analytical method. These deficiencies became apparent when the method was applied to groundwater and surface water samples dominated by iron–cyanide complexes (>50% of the total cyanide content); the analytical method, as is, is fine for determining WAD cyanide in any aqueous sample where weak metal cyanide complexes and free cyanide ions dominate the cyanide speciation (i.e., iron–cyanide complexes are <50% of the total cyanide content). It was also determined that the means required to correct these deficiencies depended upon which iron–cyanide complex was present (i.e., ferricyanide/ferrocyanide or an iron–pentacyano methylamino species, [Fe(CN)5NHCH3]4−). For the samples dominated by the ferri- and ferrocyanide complexes, addition of the prescribed amount of zinc acetate under mildly acidic conditions was sufficient to entirely remove these complexes from solution via formation of an iron cyanide precipitate. However, the high-temperature distillation step of the analytical method was found to destabilize the iron–cyanide precipitate thus formed, resulting in the recovery of some of this strong acid dissociable cyanide complex as WAD cyanide. To rectify the method deficiency, an intermediate filtration step using a 0.45-micron filter was introduced to remove the precipitate before distillation is performed. A slightly different modified method was required when the iron–cyanide complexes were dominated by the iron–pentacyano methylamino complex, that is, [Fe(CN)5NHCH3]4−. In this instance, it was necessary to add three times the prescribed amount of zinc acetate to remove the complex from the solution. Also, the precipitate was comprised of smaller size particles, and hence, a smaller filter size (0.2 micron) was required to remove the precipitate before distillation. These modifications to the current WAD method provided a more accurate determination of the WAD cyanide content of the sample that is dominated by iron–cyanide complexes, as verified by the EPA-approved available cyanide method OIA-1677. However, for samples dominated by weak metal–cyanide complexes, the current WAD cyanide analytical method is deemed appropriate.

Outline of a nuclear seawater desalination plant for the Shandong Peninsula

A pre-project study of the Shandong nuclear seawater desalination plant was carried out in 2001. The plant will produce 160,000 m³/d of potable water using a 200 MWth nuclear heating reactor, developed by INET, coupled to a high-temperature multi-effect distillation process. This paper presents an outline of the Shandong desalination project, including the main features of the reactor and desalination plants, interface considerations between the reactor and desalination plants and some economic data.

The effect of thickness on the dielectric properties of highly (111) oriented Pb(Zr 0.53Ti 0.47)O 3 thin films prepared by a simple sol–gel route

Lead zirconate titanate Pb(Zr 0.53Ti 0.47)O 3 (PZT) ferroelectric thin films of various thicknesses were grown on Pt(111)/Ti/SiO 2/Si(100) substrates by a simple sol–gel process, without reflux or high temperature distillation to remove water. The thin films were annealed at 550–600 °C in an oxygen atmosphere by rapid thermal annealing (RTA), and highly (111)-oriented PZT thin films have been obtained. The microstructure and surface morphologies of the thin films have studied by X-ray diffraction (XRD) and atomic force microscopy (AFM). AFM images shown that the highly (111) oriented PZT thin films on Pt/Ti/SiO 2/Si substrates with grain sizes of 0.2–0.3 and 2–3 μm, and root mean square roughnesses of 0.92 and 34 nm, for PZT films with thicknesses of 0.3 and 0.56 μm, respectively. The remanent polarization ( P r) and coercive electric field ( E c) values were 32.2 μC/cm 2 and 79.9 kV/cm, 27.7 μC/cm 2 and 54.4 kV/cm; at 100 kHz, the dielectric constant and dissipation factor were 539 and 0.066, 821 and 0.029, respectively, for PZT films with thicknesses of 0.3 and 0.56 μm.

M. Deb (Ed.) Crustal Evolution and Metallogeny in the Northwestern Indian Shield. New Delhi (Narosa Publishing House, Alpha Science International Ltd. Pangbourne, UK. Printed in India), 2000, xii + 516 pp. Price £95. ISBN 1 84265 001 7.

Subtitled ‘A Festschrift for Asoke Mookherjee’ this compilation of 23 papers is the result of a seminar held at Delhi University in December 1996. The papers have been subject to largely local review by authors of other papers in the volume. The Northwestern Indian Shield covers the state of Rajasthan, and parts of northern Gujarat and Madhya Pradesh, also Haryana and Delhi, and an introductory chapter by M. Deb provides a useful brief review of the other chapters putting them into context. Some of the metal deposits of this region were worked in antiquity (at least 400 BC) and none of the deposits described is a recent discovery. S.M. Gandhi details the archaeological evidence for the ancient smelting of copper, lead, silver and zinc, regarding the “complex and sophisticated pyrotechnical operation practiced at Zawar” as ancestral to the high-temperature distillation techniques for zinc manufacture developed in the 19th and 20th centuries. The following nine …

DETERMINATION OF COVALENT AND NONCOVALENT BINDING INTERACTIONS BETWEEN XENOBIOTIC CHEMICALS AND SOIL

Knowledge of the fate of xenobiotics in terrestrial systems is an important aspect of soil science. This paper reviews experimental approaches that have enhanced our understanding of binding interactions between xenobiotic chemicals and soil. First attempts to evaluate the nature of binding focused on the identification of covalently bound or physically sequestered chemicals upon their removal from the soil matrix by alkaline or acid hydrolysis and other release techniques (e.g., high-temperature distillation, supercritical fluid extraction or microwave extraction). The covalent nature of bonds formed was confirmed by model studies in which xenobiotic chemicals, such as phenols or anilines, were allowed to interact with monomeric constituents of humus (e.g., syringic acid or guaiacol). Further studies involved 13 C or 15 N NMR analysis of 13 C- or 15 N-labeled xenobiotics that were bound to natural humic acid or soil. The resolution of NMR spectra was greatly improved by silylation ofthe soil samples and application of 13 C-depleted humic materials. NMR spectroscopy in combination with silylation was also instrumental in the evaluation of physically sequestered chemicals. A coherent theory of sequestration (dual-mode sorption model) was developed based on adsorption isotherms obtained in experiments involving long contact times between xenobiotics and soil. The future of research on binding appears to depend largely on NMR spectroscopy and further progress in our knowledge of humus.

Vacuum desalination for water purification using waste heat

Vacuum desalination is a process by which water is vaporized at a lower temperature when subjected to vacuum pressure. The heat energy requirement for desalination using a distillation process can be brought down by reducing the boiling temperature. The boiling temperature of seawater can be lowered to as low as 400°C by the creation of a vacuum. Using waste heat from a steam turbine, a pilot study was conducted in the laboratory to investigate the feasibility of using a vacuum desalination process for water supply. The treatment system is designed to minimize the heat requirement. Initially, the seawater is converted to a wet steam in a saturated vapour heater. This vapour heater receives heat from the superheated steam which is due for condensation. The dry component of the wet steam is heated to superheated condition by a superheated vapour heater. This superheated vapour heater receives heat from the waste heat from a steam turbine. Superheated vapour is used to covert incoming seawater to wet steam and then be condensed as the product of the system for potable use. The investigation shows that a vacuum desalination system using turbine exhaust waste steam is possible and has several advantages. Seawater can be boiled at a lower temperature and thus save in energy consumption. Based on experimental results, water boils at 40–90°C at the corresponding vacuum pressure of 0.1–0.7 bar, respectively. The consumption of heat from the waste steam is minimized as the superheated vapour is used to heat the influent seawater. Most of the heat from the waste heat is required to compensate for the heat losses in the system. The energy efficiency of the system depends very much on decreasing the heat losses from the system. It is possible to use nonconventional energy sources such as lower pressure waste steam for vacuum desalination. Hard scale formation in the system can be minimized as scale forming is the major problem in a high temperature distillation process. The qualities of distillates are excellent.

Improved techniques for stable isotope analyses of microlitre quantities of water from fluid inclusions in halite and concentrated brines

A method has been developed to analyze both H- and 0-isotope compositions of saline waters and fluid inclusion brines without significant interference of salts. It involves high-temperature distillation under vacuum and reaction of the extracted water with zinc to produce HZ for H-isotope analyses and with guanidine hydrochloride (GuHCI) to produce CO 2 for O-isotope analyses. prec:isions of ± 2%o and ±0.3%o for 8D- and 8' $O-values, respectively, can be realized with as little as 4 μ1 saline water for bath elements.

Theoretical analysis of a novel modified recirculation multi-stage flash low temperature system

This article analyzes a novel modified recirculation multi-stage flash (MR-MSF) system working in the VC mode with a LiBr-H 2O absorption machine where the condenser and evaporator are replaced by the MR-MSF system. Steam produced in the generator is used for the heat input section while the absorber receives the vapour produced in the last stages of the heat reject section (HRjS). The blowdown from the bottom stage is used as the sink for the HRjS which includes ten stages. The system operates over a new record for the flashing range and low top brine temperature (TBT). Results with a 3000 TR absorption machine showed an expected output of 0.9 mgd at a GOR of 0.7 and a PR of 8.27 for a FR of 6–63°C. The present system provides the possibility of operating with TBT as low as 36°C. This would overcome — or at least minimize — the corrosion and scale problems plaguing conventional high temperature distillation plants.

Thermal evaluation of high temperature distillation under an active mode of operation

The thermal analysis of a double effect distillation unit in active operation is presented, taking into account the system as well as climatic parameters. Analytical expressions for hourly yield from the upper and lower basin and daily efficiency have been derived by using temperature-dependent internal heat transfer coefficients. Numerical calculations have been carried out for the same set of parameters as before [1] for comparison purposes. On the basis of numerical results, it is observed that there is an increase of 20% and 30% in efficiency of a solar distillation unit working under active and passive modes, respectively.

Bioavailability of Bound Pesticide Residues and Potential Toxicologic Consequences

ConclusionsThe use of 14C-labeled pesticides has made us aware of the existence of bound residues in edible tissue and plants. These residues would escape detection by the conventional analytical methods and would result in an underestimation of the edible tissue or plant burden of total pesticide residues. The methodology for the analysis of bound pesticide residues is still in the developmental stage. The total 14C-bound residues in tissues and plants are usually estimated by combustion of the extracted material to yield 14CO2. The high temperature distillation technique and supercritical methanol may provide a possible means for the chemical identification of bound residues. However, the application of these techniques to bound residue analysis of other pesticides has not been fully explored.A major portion of bound pesticide residues in plant tissues may be associated with lignin. Thus, lignin formation in plants may serve as a system for plants to store pesticide residues by incorporating them into i...

Transient performance of a high temperature solar distillation system

The solar still coupled to a flat-plate solar collector in a very useful appliance for high temperature distillation. This system gives enhanced distillate output owing to higher water-to-cover temperature difference. Moreover, it could also be used to extract essence of flowers, seeds, roots, etc. essentially required in the processing of cosmatic goods. In this communication, transient performance of the proposed system operating under thermosipnon mode is presented. Explicit expressions have been obtained for the temperatures of various components of the proposed system. System-performance has been explicitly expressed as the daily destillate output and the system efficiency. Effects of both still as well as the collector parameters are incorporated in the analysis. Quantitative assessment of the analytical results were made using meteorological parameters for a typical day in Delhi. The investigations made is worthwhile for optimization of the design parameters of the system. Optimal design of the proposed system is also very useful to cater the needs high temperature distillation in remote regions having no electrical power.

Performance study of a high temperature distillation system

A transient analysis of a solar still integrated with a panel of collectors through a heat exchanger has been developed by incorporating the effect of all possible system parameters. In the present analysis, the effect of temperature dependence of internal heat transfer coefficients on the performance of a solar still have been studied in detail. The theoretical results have also been validated by experimental results through an experiment carried out at CES, IIT Delhi. It is observed that (i) the internal convective and radiative heat transfer coefficients can be considered as constants during operation of the solar still, as considered by earlier workers (M. A. S. Malik, G. N. Tiwari, A. Kumar and M. S. Sodha, Solar Distillation. Pergamon Press, Oxford (1982); Ref. [1]) and (ii) the internal evaporative heat transfer coefficient is a very sensitive parameter of the water and glass temperatures (Fig. 5).

Extractive acetonobutylic fermentation by coupling ultrafiltration and distillation

An extractive acetonobutylic fermentation process is developed by integrating bioproduction, Ultrafiltration, and distillation, providing simultaneous retention of biomass, selective removal of inhibitors from the permeate, as well as separation and purification of acetone-butanol-ethanol solvents. Successive batch fermentations were performed with normal pressure distillation (98 degrees C), which permitted prolonging and enhancing (by a factor of 3) solvent production, with very few volume exchanges of medium (average dilution rate ws 0.002 h(-1)), and recovering on-line concentrated solvents. Different operating conditions were also tested in order to study the presence of extracellular autolytic enzymes as inhibition factors: It was shown that, (1) extracellular autolytic activity remains low during the larger part of fermentations, even without enzyme-inactivating thermotreatment in the distillation boiler, and (2) high-temperature distillation causes deleterious effects to the culture medium for long duration treatments. Progressive improvements of the process were achieved, first, by managing continuous runs, providing a minimum renewal of the culture medium and, mainly, by decreasing temperature and pressure of distilation. Solvent productivity then reached 2.6 g/L h for a 0.036 h(-1) average dilution rate, corresponding to a feed concentration of 156 g/L glucose actually consumed.

Physicochemical Isotope anomalies

Isotopic composition of refractory elements can be modified, by physical processes such as distillation and sputtering, in unexpected patterns. Distillation enriches the heavy isotopes in the residue and the light isotopes in the vapour. However, current models appear to be inadequate to describe the detailed mass dependence, in particular for large fractionations. Coarse- and fine-grained inclusions from the Allende meteorite exhibit correlated isotope effects in Mg both as mass-dependent fractionation and residual anomalies. This isotope pattern can be duplicated by high temperature distillation in the laboratory. A ubiquitous property of meteoritic inclusions for Mg as well as for most of the other elements, where measurements exist, is mass-dependent fractionation. In contrast, terrestrial materials such as microtektites, tektite buttons as well as lunar orange and green glass spheres have normal Mg isotopic composition. A subset of interplanetary dust particles labelled as chondritic aggregates exhibit excesses in 26Mg and deuterium anomalies. Sputtering is expected to be a dominant mechanism in the destruction of grains within interstellar dust clouds. An active proto-sun as well as the present solar-wind and solar-flare flux are of sufficient intensity to sputter significant amounts of material. Laboratory experiments in Mg show widespread isotope effects including residual 26Mg excesses and mass dependent fractionation. It is possible that the 26Mg excesses in interplanetary dust is related to sputtering by energetic solar-wind particles. The implication of the laboratory distillation and sputtering effects are discussed and contrasted with the anomalies in meteoritic inclusions and other extraterrestrial materials we have access to.

Thermal modelling of high temperature distillation

This communication presents a comparative study of a single basin solar still under various modes of operation. A simple transient analysis of all the modes under the same meteorological conditions has been presented. The water depth in the solar still and the absorptivity of the basin liner along with the water flow over the glass cover of the still has been found to affect the daily distillate production of the system considerably. The thermosyphon mode enhances the daily distillate production. It has also been observed that the evaporative heat transfer coefficient is a very strong function of temperature.

Isotope anomalies induced in laboratory distillation

We have carried out high-temperature distillation experiments at 5 × 10−5 torr on terrestrial pyroxene crystals and measured24Mg, 25Mg and 26Mg simultaneously using a 61-cm multi-cup mass spectrometer. The raw data were corrected for isotope fractionation using the power law and the Rayleigh law. Regardless of the correction procedure, the sample residues are depleted in 26Mg and the condensates are enriched in 26Mg, relative to non-distilled standards. These effects mimic the 'isotope anomalies' in Mg observed in Allende coarse- and fine-grained inclusions, previously attributed to nucleosynthetic processes involving 26Al.

High temperature distillation process with sea water feed decalcification pretreatment

The performance ratio of a desalination plant can be increased to reach 16–18 by coupling it with a decalcification pretreatment by ion exchange of the sea-water make-up, so making MSF comparable with RO from energetic point of view. A new strong cationic resin DECAL has been tailored; its main features are high selectivity towards the calcium ion and low concentration of the regenerating brine. These characteristics make it compatible with the normal operating range of multiflash plants and very suitable for the above service, when compared with other resins. The optimum coupling conditions of the whole plant, as has been pointed out, lie between 140°C and 150 °C for the top brine temperature and 2 to 2.5 for the brine concentration factor. In these conditions it is possible to operate with sea water-resin bed ratio higher than 20.

Studies on bound 14C-prometryn residues in soil and plants

A high-temperature distillation technique was developed for determining and chemically identifying the bound (nonextractable) residues of 14C-prometryn in an organic soil and plants. A considerable portion of the bound 14C residues in the incubated organic soil was identified as prometryn. These residues were absorbed by plants grown in the soil. Hono-and di- N -dealkylated metabolites of prometryn were present in the plant bound 14C residues and a major portion of bound residues as associated with lignin. Soil-bound 14C residues were also released from soil by microbes. The bound 14C residues in soil were associated with humin, humic acid, and fulvic acid fractions. Thermoanalytical methods were used to obtained information on the nature and location of 14C bound residues in soil and humic materials.

Calcium sulfate hemihydrate scaling threshold enhancement by magnesium ion augmentation

Efficient high temperature distillation of sea water cannot be realized without development of scale control systems for calcium sulfate. This paper describes a new concept of scaling threshold enhancement based on complexing a portion of dissolved sulfate ion in the form of stable MgSO o ion pairs. Complexing may be accomplished by augmentation of feed water with magnesium ion recovered and recycled from distilling plant blowdown. This “tying up” of sulfate ion results in higher solubility levels of calcium sulfate. Magnesium ion augmentation at levels up to three times ambient results in markedly improved resistance to hemihydrate scaling in natural sea water. Significantly higher levels of operating temperature and concentration factor may be achieved by this technology.