Treatment of water contaminated with volatile organic compounds (VOCs) is a major problem for the United States chemical industry. Currently, VOCs are removed from moderately contaminated wastewater streams by processes such as steam stripping and from dilute wastewaters by air stripping combined with a carbon adsorption off-gas treatment system. This paper describes the development and performance of a hybrid process that combines air stripping with membrane organic-vapor separation to recover VOCs from the stripper off-gas. A number of prototype systems have been constructed and evaluated. The optimum system appears to be a tray stripper fitted with a high-pressure compression-condensation membrane separation unit. Such a system can remove 95 to 99% of the VOCs present in contaminated water; the removed VOCs are recovered as a liquid condensate. The economics of the technology are competitive with alternative processes, particularly for streams containing more than 500 ppm VOC and having flow rates less than 10 to 30 g a h i n .
SynopsisAniline was polymerized using a static electrochemical cell and a fluidized bed electrode reactor (both static and fluidized beds) to form thin films, respectively, on plate and particulate substrates. Parameters such as reaction time, applied voltage, anolyte Aowrate, and monomer concentration on the rate of polymerization were studied and correlated with polymer film thickness and surface morphology, as observed on a scanning electron microscope. INTRODUCTIONThe variety of possible applications for polyaniline (PA), due to its unique physical and electrical properties, has led to an impressive amount of research. Polyaniline can be formed by chemical1 or electrochemical2 oxidation, and the latter method can involve organic or aqueous solution^.^-^ Depending on the conditions the polymer has been subjected to, PA may act as an insulator, a semiconductor, or even a metal-like conductor.8 The drastic changes in conductivity are due to the combined effects of oxidation and protonic acid doping? Because of this ability to transform PA back and forth between its conducting and insulating forms, PA has been tested for use in microelectronic devices, lo for corrosion protection of electrodes, l1 and for use in rechargeable batteries.12 Other investigations have focused on the effects the chemical transformations have on the electrical conductivity, l3 the molecular structure, l4 the reaction mechanism, l5 the molecular weight distribution, l6 and even the fractal dimension.17Much of the kinetic studies on aniline polymerization has been performed using standard electrochemical cells and rotating disk e1e~trodes.l~ The standard cell can be affected by any mass transfer limitations inherent to the system being studied, while experiments using rotating disk electrodes are better able to demonstrate the effects of mass transfer on the reaction rate. A fluidized bed electrode should also be useful for such demonstrations, but few have discussed using such an electrode for electropolymerization.20s21 A fluidized bed system presents two distinct advantages: ( i ) The continuous disturbance of the bed contributes to the preferred high rates of mass transfer to the surface
Chlorine is manufactured by the electrolysis of brine. The chlorine product is a gas, which is collected, dried, compressed, and cooled to produce a liquid. This paper describes the development and field demonstration of a membrane process to recover chlorine from the liquefaction tail gas of chloralkali plants. The tail gas consists of about 20% chlorine and 50-70% air, with the balance being hydrogen and carbon dioxide. A number of membrane materials can achieve a selectivity of 20 or more for chlorine from nitrogen, but degradation of the membrane materials in the presence of high concentrations of chlorine gas often occurs. However, modified silicone rubber membranes are stable to chlorine gas streams. Silicone rubber composite membranes were prepared and formed into modules of 1-2 m 2 membrane area. The modules were tested in the laboratory and in a field test on a slip stream from a chlorine liquefaction unit. In the laboratory, chlorine/nitrogen membrane selectivities of more than 40 were obtained, but selectivities of 6-10 were measured in the field test. This decrease in selectivity was caused by low gas flow rates through the modules, which resulted in concentration polarization effects. However, the membrane maintained essentially constant fluxes and selectivities in field tests lasting more than 1 month. Calculated plant designs based on a selectivity of 8 are able to recover more than 95% of the chlorine in the tail gas. Typical project payback times based on the value of the recovered chlorine and avoided caustic scrubber chemical use are expected to be 1-2 years.
During 1990, on behalf of DOE's Office of Technology Development, Argonne National Laboratory (ANL) conducted a competitive procurement of research and development projects addressing soil remediation, groundwater remediation, site characterization, and contaminant containment. Fifteen contracts were negotiated in these areas. This report documents work performed as part of the Private Sector Research and Development Program sponsored by the DOE's Office of Technology Development within the Environmental Restoration and W a s t e Management Program. The research and development work described herein was conducted under contract to ANL. On behalf of DOE and ANL, I wish to thank the performing contractor and especially the report authors for their cooperation and their contribution to development of new processes for characterization and remediation of DOE's environmental problems. We anticipate that the R&D investment described here will be repaid many-fold in the application of better, faster, safer, and cheaper technologies.
During 1990, on behalf of DOE's Office of Technology Development, Argonne National Laboratory (ANL) conducted a competitive procurement of research and development projects addressing soil remediation, groundwater remediation, site characterization, and contaminant containment. Fifteen contracts were negotiated in these areas. This report documents work performed as part of the Private Sector Research and Development Program sponsored by the DOE's Office of Technology Development within the Environmental Restoration and W a s t e Management Program. The research and development work described herein was conducted under contract to ANL. On behalf of DOE and ANL, I wish to thank the performing contractor and especially the report authors for their cooperation and their contribution to development of new processes for characterization and remediation of DOE's environmental problems. We anticipate that the R&D investment described here will be repaid many-fold in the application of better, faster, safer, and cheaper technologies.
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