Water-based Processes Research Articles

A feasibility and cost comparison of perchloroethylene dry cleaning to professional wet cleaning: case study of Silver Hanger Cleaners, Bellingham, Massachusetts

The Toxics Use Reduction Institute (TURI) has been working with the dry cleaning sector for over 10 years – focusing on the ultimate goal of eliminating the use of perchloroethylene in this sector due to the availability of less toxic, feasible alternatives. Professional wet cleaning has been identified as one of these alternatives and has been a focus of the Institute in recent years. In 2008, the Institute provided a matching grant to Silver Hanger Cleaners in Bellingham, Massachusetts to convert their operations from perchloroethylene-based to water-based processes. Two years of data have been collected from the facility, reflecting one year of solvent use and one year of dedicated professional wet cleaning. The analysis of that data is presented here, including capital costs, performance data and associated costs, operational costs, and resource use and associated costs.

Temperature observations in Antarctic tafoni: implications for weathering, biological colonization, and tafoni formation

Tafoni have long been recognized, measured and discussed within the Antarctic context. However, with respect to the formative processes tafoni still remain somewhat of an enigma. In terms of the weathering attributes of tafoni, one problem is the monitoring of environmental conditions without the transducers themselves altering that environment. The application of ultra-small thermocouples provides an avenue for monitoring of rock surface temperatures without influence on the tafoni environment. At an Antarctic site temperatures were measured both inside and outside of a tafone, with data at 20 second intervals. These data show a spatial variability that may help explain tafoni development, at least in terms of weathering. Humidity data indicate that moisture conditions are very low such that water-based weathering processes are temporally and spatially constrained. The presence of several episodes of extreme temperature variations indicates that thermal stress may be an important contributor to weathering here. It is argued that the absence of any endolithic communities (at this site) within the sandstone, in which the tafoni develop, is a reflection of weathering rates that exceed the ability of organisms to invade and colonize the rock. At the present time, weathering appears to be primarily in the form of granular disintegration and flaking.

The Role of Particle Filtration in Industrial Scale EPD Processes

Electrophoretic deposition or EPD is a well established method for creating decorative and protective coatings and other structures on various electroconductive substrates. The formation of these coatings and structures can be prejudiced by the presence of oversized or contaminant particles as well as excess or contaminant electrolytes resulting in appearance and performance problems in the final product. Nuisance particles come from diverse sources and are an inevitability in industrial environments. Efficient and effective particle capture strategies are therefore essential. In water-based EPD processes, control over the content electrolytes and other continuous phase materials can be accomplished using tangential or cross-flow filtration where the permeate contains the undesirable materials and can be treated or disposed of outside the system. But for particles and other disperse phase materials, dead-end filtration techniques are required. Here the undesirable materials are captured, concentrated and retained on the filter medium within the system. Disposal only occurs as a result of discarding or treating the filter medium itself. Many types of dead-end filtration media are commercially available. Retention size and materials of construction all have relevance for system compatibility and effectiveness of particle capture. Practical experience shows that selection of the correct type of particle filtration optimises process quality. Using inappropriate filter media can be not just ineffective, but actively detrimental. This paper describes commonly available particle filter systems and how they interact with industrial EPD process.

Role of Water in the Physical Stability of Solid Dosage Formulations

The interaction of moisture with pharmaceutical solids is highly crucial to an understanding of water-based processes, for example, manufacturing processes or prediction of solid dosage form stability and shelf life. Both the active pharmaceutical ingredient (API) and excipients in the formulation have different moisture sorption properties that can result in unexpected processing-induced phase transitions and they can affect solid-state phase transitions in the final dosage forms. The character of excipient effects on the stability of formulation. Phase transformations in formulations can lead to instability in physicochemical, biopharmaceutical, and processing properties of products. The aim of the present study was to investigate the water sorption properties of different excipients, model the sorption isotherms, examine the phase transitions, and identify differences of excipients in solid dosage form stability using dynamic vapor sorption analysis, near-infrared spectroscopy, and X-ray diffraction methods. The thermal processing was carried out with a variable temperature X-ray powder diffractometer to compare the dehydration behavior of wet excipients and evaluate solid-state properties during heating. These results showed that despite some limitations, moisture sorption isotherms of excipients are useful in predicting solid-state stability, interactions at early stages of formulation development, and effects of moisture on physicochemical properties of the final dosage forms.

An outbreak of hypersensitivity pneumonitis at a metalworking plant: a longitudinal assessment of intervention effectiveness.

The authors describe a longitudinal assessment of intervention effectiveness in response to an outbreak of hypersensitivity pneumonitis (HP) at a metalworking facility. Thirty-five (29%) of the plant's 120 production workers were given a clinical diagnosis of HP during the two years of the investigation. Although quantitative exposure assessment tools were of limited utility, the investigators successfully used qualitative observations and the patients' return-to-work experiences to iteratively evaluate their exposure control recommendations. Recommended interventions included improving metalworking fluid management practices, enclosing selected metalworking fluid machining operations, eliminating mist cooling, exhausting two additional water-based industrial processes, increasing general dilution ventilation, and worker training. As of November 1999, 26 months into the outbreak, 51 percent (18) of the employees with a clinical diagnosis of hypersensitivity pneumonitis had been able to return to work. The symptom onset of the 35 workers who were given a clinical diagnosis of hypersensitivity pneumonitis during the two-year study period predated the implementation of the interventions. The collaboration of a multidisciplinary team appears to have allowed for successful intervention in this setting. A specific etiological agent(s) associated with the outbreak was not confirmed during the investigation. An acid fast isolate identified as being in the Mycobacterium chelonae group was detected in only one of the submitted metalworking fluid (MWF) sump samples. Longitudinally, there was a statistically significant difference in MWF sump bacteria (X(2) = 286.4, df = 17, p <.0001) and MWF sump fungi (X(2) = 28.1, df = 7, p <.0002). Measured oil mist air levels did not exceed the Occupational Safety and Health Administration's (OSHA's) permissible exposure limit (PEL), and in fact, did not exceed 0.5 mg/m(3).

Equilibrating metal-oxide cluster ensembles for oxidation reactions using oxygen in water.

Although many enzymes can readily and selectively use oxygen in water-the most familiar and attractive of all oxidants and solvents, respectively-the design of synthetic catalysts for selective water-based oxidation processes utilizing molecular oxygen remains a daunting task. Particularly problematic is the fact that oxidation of substrates by O2 involves radical chemistry, which is intrinsically non-selective and difficult to control. In addition, metallo-organic catalysts are inherently susceptible to degradation by oxygen-based radicals, while their transition-metal-ion active sites often react with water to give insoluble, and thus inactive, oxides or hydroxides. Furthermore, pH control is often required to avoid acid or base degradation of organic substrates or products. Unlike metallo-organic catalysts, polyoxometalate anions are oxidatively stable and are reversible oxidants for use with O2 (refs 8,9,10). Here we show how thermodynamically controlled self-assembly of an equilibrated ensemble of polyoxometalates, with the heteropolytungstate anion [AIVVW11O40]6- as its main component, imparts both stability in water and internal pH-management. Designed to operate at near-neutral pH, this system facilitates a two-step O2-based process for the selective delignification of wood (lignocellulose) fibres. By directly monitoring the central Al atom, we show that equilibration reactions typical of polyoxometalate anions keep the pH of the system near 7 during both process steps.

Ambient-proportional sensing control reduces heat tracing costs

The majority of heat tracing applications deal with winterization for water and water-based processes. Whether for piping, tanks or instruments, control of freeze protection systems are often simple, but not energy efficient. The authors present an approach to this basic application which has yielded direct benefits to users through an alternative control method that typically uses a single-pole thermostat to switch a multipole contactor installed between the main circuit breaker and a distribution panel board that energizes multiple heating circuits. This provides control with minimal cost in design and installation.

Direct electrochemistry of nanoparticulate Fe2O3 in aqueous solution and adsorbed onto tin-doped indium oxide

Abstract Nanoparticulate iron oxides occur naturally, for example, in soil, water, and in the cytoplasm of living cells. The redox properties and detection of these nanoparticles are therefore of considerable importance. Understanding and mimicking nanoparticle-based redox reactions may lead to new types of water-based electrochemical processes. In this study, the electrochemical detection of 4­5 nm diameter Fe2O3 nanoparticles dissolved in aqueous buffer solutions is investigated as a model system. Voltammetric experiments with nanoparticulate Fe2O3 are reported based on two complementary approaches: (i) Fe2O3 nanoparticles adsorbed onto tin-doped indium oxide (ITO) electrodes are shown to give well-defined voltammetric reduction responses and (ii) hydrodynamic voltammety in the presence of fast (24 kHz ultrasound-enhanced) mass transport is shown to allow the direct detection of Fe2O3 nanoparticles in solution. Both the adhesion and the electrochemical reactivity of Fe2O3 nanoparticles at ITO electrode surfaces are strongly affected by the solution composition and the pH.

Effect of natural surfactants released from athabasca oil sands on air holdup in a water column

AbstractNatural surfactants released from Athabasca oil sands are a crucial component in water‐based bitumen extraction processes. The effect of natural surfactant released from estuarine and marine oil sands on air holdup was investigated using a water column. The air holdup in the resultant supernatant of the conditioned oil sands slurry was found to be much higher than that in de‐ionized water. A further increase in air holdup was observed with the supernatant obtained from the oil sands slurry conditioned with caustic. Aging of the ore prior to bitumen extraction caused an increase in air holdup. The presence of small amount of fine solids in the supernatant resulted in a higher air holdup for all the cases studied. The present study shows that the higher air holdup and poorer processibility of marine ores, compared with estuarine ores, could be accounted for by the release of larger amount of surface active species and the presence of more fine clays in the ores.

Photoinduced decarboxylation reactions

Intramolecular photodecarboxylation reactions of potassium ω-phthalimido carboxylates in water or mixtures of water and organic solvents (acetone, acetonitrile) were investigated using an incoherent XeCl excimer radiation source emitting at 308 nm. Electron transfer induced intermolecular addition of alkyl carboxylates to phthalimides likewise proceeded efficiently under these conditions. The reactions can be performed in multigram (i.e. 10–30 g product) quantities using easiliy available substrates such as glutamic acid (for the synthesis of 3), leucine (for 8, 9) or simple alkyl carboxylates (for 11). The advantages of this methodology are: clean and high-yielding reactions, solvent and waste minimization, water-based processes and efficient utilization of photons of defined energy.

Flocculation of lime-treated oil sands tailings

Whole oil sands tailings resulting from water-based bitumen extraction processes can be co-flocculated, after treatment with slaked lime, with low dosages of a high molecular weight anionic polyacrylamide. The resulting composite sand-clay particles settle and dewater rapidly to a stackable product that can be hand-squeezed to 40–83 wt% solids. The final solids content depends on the initial bitumen extraction process used. The procedure is particularly appropriate for use with the alkali recycle process, in which bitumen is extracted from oil sand by flotation after conditioning with dilute alkali at ambient temperatures. Treatment of the resulting tailings with lime is the key step that releases alkali, by ion-exchange mechanisms, into the recyclable process water. This step is the first in the co-flocculation sequence.

Water-soluble photoresins based on polymeric azo compounds

Polymeric azosulfonates lose their water solubility when exposed to UV light due to decomposition of the azo function. This effect can be used in water-based photoprinting processes. Water-soluble copolymers of azosulfonate containing repeat units and methyl methacrylate have been alternatively synthesized by a polymer-analogous reaction [1,2] and by direct copolymerization [3]. Both polymer types have been evaluated for application as photoresins in offset printing processes. The polymer made by copolymerization is superior and shows excellent results for photosensitivity, resolution, film-forming properties, and development in water, as well as for thermal and moisture storage stability.

Formation of diamond films from low pressure radio frequency induction discharges

Diamond films have been deposited in a low pressure, radio frequency (r.f.) induction plasma-assisted chemical vapor deposition system. The r.f.-induction system confines the plasma at the low pressures of operation 0.010–10.00 Torr to permit efficient dissociation of the reactant gases. A variety of chemical systems have been used to deposit diamond, including traditional H 2-CH 4 discharges containing 0.5–2.0% CH 4; H 2-CF 4 discharges containing 4–16% CF 4, and water vapor discharges containing high concentrations of alcohol and/or acetic acid vapors. No molecular hydrogen is admitted to the growth chamber for the water-based processes. The water vapor becomes the functional equivalent of the molecular hydrogen used in more traditional H 2-CH 4 discharges. The success of the low pressure r.f.-induction plasma for diamond growth from the wide variety of chemical systems is predicated on the generation of a high electron density plasma. Parent gaseous molecules are converted into appropriate high temperature stable products such as H, H 2, CO, and C 2H 2 as they traverse the plasma. Quadrupole mass spectroscopy has been used to study the conversion of the water-alcohol vapors to H 2, CO, and C 2H 2 as they pass through the r.f. plasma, 99% of the CH 4O is converted into H 2, H 2O, and C 2H 2. These studies show plasma conversion of H 2O into molecular H 2. The excess oxygen is rapidly converted into CO through interactions of the O, presumably with solid carbon sources. Optical emission from both the water-based discharges and the molecular hydrogen-based discharges shows the propensity for atomic hydrogen generation from these low pressure r.f.-induction discharges.

Comparison of water-based physical separation processes for U.S. tar sands

The development of water-based, physical separation processes for domestic tar sands has been useful in demonstrating the effectiveness of three different processing strategies: the hot-water process, the diluent assisted hot-water process, and the ambient-temperature process. The effectiveness of the process strategies is evaluated and compared at optimum operating conditions with regard to bitumen recovery, concentrate characteristics. Process limitations are described in terms of important tar sand properties: bitumen viscosity, bitumen/sand association, and sand composition/particle size distribution. It is shown that the hot-water process and ambient-temperature process are restricted in their range of application. Both of these processes require a tar sand that possesses a specific set of characteristics. However, the diluent assisted hot-water process has a wider range of application and fewer process limitations when compared to the original hot-water process.

Possible identification of poorly crystalline inorganic matter present in Athabasca oil sands

In Athabasca oil sands there is a fraction of poorly crystalline minerals tightly bound to humic matter. This fraction resists subsequent wetting by water and introduces serious problems in bitumen recovery when using water-based processes. In this study 29Si solid state magic angle spinning (MAS) NMR, infrared spectroscopy and transmission electron microscopy were applied to characterize these minerals isolated from Athabasca oil sands of estuarine and marine origin. It was demonstrated that poorly crystalline inorganic matter present in Athabasca oil sands is comprised of aluminosilicates, most probably allophane-like minerals. Humic matter could interact with this type of material through incorporation of an organic anion as a ligand to a metal ion, coulombic and van der Waals forces and hydrogen bonding.