Chlor-alkali Industry Research Articles

An inventory of historical mercury emissions in Maritime Canada: implications for present and future contamination

Mercury is a longstanding concern in Maritime Canada due to high levels of contamination in a number of fish and bird species. The recycled component of past releases of anthropogenic mercury may be a significant source of ongoing pollution in many areas. Historical information on mercury releases can be used to quantify past and present anthropogenic contamination. We present an inventory of historical mercury emissions from anthropogenic sources in Maritime Canada for the years 1800–1995. Long-term trends in mercury emissions and the significance of the cumulative burden of mercury released from local sources are discussed. Emissions are calculated using both historical monitoring data and the application of emission factors. The nature of current anthropogenic sources of mercury is quite different than it was several decades ago when many of the existing policies governing mercury pollution were created. Our inventory illustrates that many of the most significant sources in the past such as the chlor-alkali industry, paint containing mercury additives, and pharmaceuticals, have been largely phased out with fossil fuel combustion and waste disposal remaining as the most significant modern sources. Atmospheric emissions in Maritime Canada peaked in 1945 (>1750 kg year −1), and again between 1965 and 1970 (>2600 kg year −1). Cumulative releases of mercury from anthropogenic sources for the years 1800–1995 were between 115 and 259 t to the atmosphere alone, and 327–448 t when discharges to wastewater and effluents were included. Assuming that only 0.2% ( Nriagu, 1994) of these releases become part of the recycled fraction of current fluxes, we estimate that between 570 and 900 kg Hg year −1 is deposited in Maritime Canada from past anthropogenic sources. Modern sources within Maritime Canada contribute at least 405 kg year −1 to the total annual deposition of 1.71 t over the provinces of New Brunswick, Nova Scotia and Prince Edward Island, leaving ∼735 kg year −1 from natural sources and long-range contamination. Further study is needed to verify these estimates and clarify the significance of natural and long-range sources of mercury in Maritime Canada.

Preparation of an adsorbent by graft polymerization of acrylamide onto coconut husk for mercury(II) removal from aqueous solution and chloralkali industry wastewater

Graft copolymerization of acrylamide onto coconut husk (CH), initiated by the ferrous ammonium sulfate/H2O2 redox initiator system, was studied. To determine the optimum conditions of grafting, the effect of the concentrations of ferrous ammonium sulfate, the monomer, and H2O2 and the time and temperature on percentage of the graft yield was studied. A new adsorbent media having a carboxylate functional group was synthesized by the surface modification of polymer-grafted coconut husk (PGCHCOOH). The mechanism of graft polymerization and surface functionalization is proposed. The material exhibits a very high adsorption potential for Hg(II). The sorption of Hg(II) was found to be dependent on the contact time, concentration, pH, and temperature. Maximum removal of 99.4% with 2 g/L of the sorbent was observed at 125 μmol L−1 Hg(II) concentration at pH 6.0. The slow step which determines the rate of exchange of Hg(II) ions is diffusion through the adsorbent particles. The diffusion coefficients, energy of activation, and entropy of activation were calculated and used to determine the theoretical behavior of the sorption process. The applicability of the Langmuir isotherm established the endothermic character of the adsorption. Acid regeneration was tried for several cycles with a view to recover the adsorbed metal ions and also to restore the sorbent to its original state. The adsorbent efficiency toward Hg(II) removal was tested using synthetic and chloralkali industry wastewaters. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1261–1269, 2000

Preparation of an adsorbent by graft polymerization of acrylamide onto coconut husk for mercury(II) removal from aqueous solution and chloralkali industry wastewater

Graft copolymerization of acrylamide onto coconut husk (CH), initiated by the ferrous ammonium sulfate/H2O2 redox initiator system, was studied. To determine the optimum conditions of grafting, the effect of the concentrations of ferrous ammonium sulfate, the monomer, and H2O2 and the time and temperature on percentage of the graft yield was studied. A new adsorbent media having a carboxylate functional group was synthesized by the surface modification of polymer-grafted coconut husk (PGCHCOOH). The mechanism of graft polymerization and surface functionalization is proposed. The material exhibits a very high adsorption potential for Hg(II). The sorption of Hg(II) was found to be dependent on the contact time, concentration, pH, and temperature. Maximum removal of 99.4% with 2 g/L of the sorbent was observed at 125 μmol L−1 Hg(II) concentration at pH 6.0. The slow step which determines the rate of exchange of Hg(II) ions is diffusion through the adsorbent particles. The diffusion coefficients, energy of activation, and entropy of activation were calculated and used to determine the theoretical behavior of the sorption process. The applicability of the Langmuir isotherm established the endothermic character of the adsorption. Acid regeneration was tried for several cycles with a view to recover the adsorbed metal ions and also to restore the sorbent to its original state. The adsorbent efficiency toward Hg(II) removal was tested using synthetic and chloralkali industry wastewaters. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1261–1269, 2000

Ion-exchange resins bearing thiol groups to remove mercury.: Part 1: synthesis and use of polymers prepared from thioester supported resin

A new synthesis of ion exchange resins containing thiol groups directly bonded on the aromatic ring is described. These resins are used to remove the small quantities of mercury (10 ppm) contained in waste water from chloralkali industries which use a mercury cathode (solvay cell). Optimum conditions have been developed to obtain resins with maximum thiol content groups. Elemental analysis, NMR, and FTIR spectroscopies data have been used to confirm the chemical structure of all products. When used in decontamination of water containing 10 ppm of Hg, we obtained a final Hg concentration of 1 ppb.

99/03400 Radiation exposure of the population in the vicinity of coal-fired power plants

Carbide slag produced from chlor-alkali industry contains high amounts of calcium compounds and can potentially be used as raw material for cement production; however, it contains large amounts of chlorine so it is essential to evaluate the emissions of chlorinated organic pollutants, including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), and polychlorinated naphthalenes (PCNs). A field study of the emission profiles of these pollutants in a cement plant using such slag was performed. The average concentrations of PCDD/Fs, PCBs, and PCNs in stack gases collected at the kiln back end were 6.31, 1.07, and 31.89 pg TEQ m−3, respectively. PCDFs dominated over PCDDs in particulate samples. Di- to pentachlorinated biphenyls were dominant homologs in the particulate samples. MonoCBs were the dominant homolog in stack gases from the kiln back end, and homolog concentrations decreased with increasing chlorine numbers. Mono- and diCNs accounted for 48–98% of PCNs. The estimated toxic equivalents of stack gas emissions of PCNs, classified as new persistent organic pollutants under Stockholm Convention, were unexpectedly higher than those of PCDD/Fs and PCBs. A mass balance indicated that all of the toxic equivalents were reduced by this cement kiln system. The highest 2,3,7,8-PCDD/F output is with clinker.

The economic importance of chlor-alkali industry products, and alternatives to those products, to the Canadian economy

The paper assesses the relative importance of chlor-alkali products as compared to alternatives in the Canadian economy. The findings indicate that the chlor-alkali industry is a small to medium sized industry. In general, currently available alternative products to chlor-alkali products exist, but at additional costs. Speculation, based on economic principles, relative to a hypothetical economic impact analysis of a gradual and selective chlor- alkali product phase-out indicates probable net benefits to society.

Chromatographic determination of anions in industrial salt and sodium chloride brines used in chlor–alkali industry

An ion chromatographic method using an ion-exchange column for the simultaneous analysis of sulphate and chlorate in industrial salt and sodium chloride brines has been developed. A mixed eluent of 2.0 m M sodium carbonate and 0.75 m M sodium bicarbonate is used. The effects of various parameters have been reported and critically discussed. The results are precise and afford simultaneous determinations of sulphate and chlorate.

Electrochemical studies of kerosene-pyrolysedcarbon films

Polycrystalline thin films of conducting carbon are deposited on alumina substrates by the pyrolysis of kerosene vapour at 1000∘C for 2h in argon atmosphere. Preliminary structural analysis is done by XRD, laser-Raman, FTIR and SEM studies. The electrochemical behaviour of as-grown conducting carbon films was investigated in various electrolytes at different pH and the performance was compared with that of platinum and glassy electrodes. The electrochemical window of the kerosene carbon electrode in 100mm H2SO4 was found to be 2.91V which is greater than that of glassy carbon (2.79V) and platinum (2.02V). Cyclic voltammetry reveals that Pt electrode has almost an equal tendency towards hydrogen and oxygen evolution, whereas glassy carbon favours hydrogen evolution and kerosene carbon favours oxygen evolution. It is suggested that the kerosene carbon electrode can be used as an oxygen electrode more efficiently. Unlike diamond films or glassy electrodes, kerosene carbon thin films are of low cost and good stability; they are also easy to grow on various ceramic substrates of any size. Moreover, these electrodes are very economical and promising for application in chlor-alkali industry.

Development of the Noble Metal/Oxide Coated Titanium Electrode

The titanium-based electrode was invented some forty years ago. Since then it has been incorporated into a wide variety of industrial processes on a huge scale, principally in the chlor-alkali industry. Deriving from industrial, as opposed to academic, work, the saga of its commercial exploitation has involved patenting and secrecy on a massive scale. Despite there being numerous contributors to the overall technology, just a few individuals are holders of the hundreds of patents that were taken out. It is not intended that this article should contain comprehensive details of patents and other published literature, but rather be an attempt to portray, as accurately as possible, the excitement generated as the technology unfolded. However, it is bound to be inevitable, bearing in mind the complexities and the scope of commercial involvement, that not all readers will be satisfied with every detail, so apologies are offered in advance to those who may inadvertently feel themselves slighted.

Electrochemical Testing and Structural Characterisation of Nickel Based Catalytic Coatings Produced by Direct Spraying

AbstractIn this paper a novel processing technique has been used to produce a range of low overpotential nickel based electrocatalytic coatings for use in the Chlor-alkali industry. These coatings include pure nickel as well as Raney nickel alloys, with particular focus upon the beneficial effects of molybdenum additions to Raney nickel.Structural characterisation of all coatings has been carried out using X-ray diffraction for quantitative phase identification, backed up by optical and electron microscopy for analysis of phase distribution. Measurement of the coatings' electrochemical properties has been performed in fully functioning micro-pilot scale electrolysis cells.

Evolution of mercury contamination in Brazil

This paper reviews the history of Hg contamination in Brazil by characterizing and quantifying two major sources of Hg emissions to the environment: industrial sources and gold mining, industry was responsible for nearly 100% of total Hg emissions from the late 1940's to the early 1970's, when efficient control policies were enforced, leading to a decrease in emissions. Gold mining, on the other hand was nearly insignificant as a Hg source up to the late 1970's, but is presently responsible for over 80% of total emissions. Presently, over 210 t of Hg are released into the environment in Brazil annually. Nearly 170 t come from gold mining operations. 17 t come from chlor-alkali industry and 10 t come from all other industrial uses. Emissions to the atmosphere are the major pathway of Hg releases to the environment and reach over 160 t.yr-1 with approximately 136 t.yr-1 from gold mining.

Contaminação por mercúrio no Brasil: fontes industriais vs garimpo de ouro

This paper reviews the history of Hg contamination in Brazil by characterizing and quantifying two major sources of Hg emissions to the environment: industrial sources and gold mining. Industry was responsible for nearly 100% of total Hg emissions from the late 1940's to the early 1970's, when efficient control policies were enforced, leading to a decrease in emissions. Gold mining, on the other hand was nearly insignificant as a Hg source up to the late 1970's, but presently is responsible for over 80% of total emissions. Presently, over 115 tons of Hg are released into the atmosphere in Brazil annually. Nearly 78 tons come from gold mining operations, 12 tons come from chlor-alkali industry and 25 tons come from all other industrial uses. Inputs to soils and waters however, are still unknown, due to lack of detailed data base. However, emissions from diffuse sources rather than well studied classical industrial sources are probably responsible for the major inputs of mercury to these compartments.

Atmospheric mercury: How much do we really know?

Abstract

Advances in anode monitoring [mercury recycling

Applications for programmable logic controllers and personal computers with the chloralkali industry continue to grow. Older multiplexed monitoring systems are being replaced with high-speed systems that can scan an entire cellroom within 2 s. Average cell voltages can be decreased by 0.25 V DC or more, resulting in significant power savings or production increases. The newer systems can be installed as an upgrade to existing systems to minimize the impact on mercury recovery plant operations.

Risk analysis of a chloralkali industry situated in a populated area using the software package MAXCRED-II

Risk assessment, based on quantitative maximum credible accident analysis (MCAA), has been conducted for a chloralkali industry situated in the midst of densely populated coastal villages. The study has made use of a software package MAXimum CREDible accident analysis version 2 (henceforth referred to as MAXCRED-II) recently developed by us. Among the six different most credible accident scenarios developed using MAXCRED-II, the one envisaging ‘confined vapor cloud explosion followed by fire ball’ (in the hydrogen storage vessel) comes out to be the worst in terms of the highest propensity for damage (overpressure, missile, heat load). It also has the potential of causing domino effect (chain of accidents). The scenario of causing domino effect (chain of accidents). The scenario of ‘continuous release of chlorine from storage vessel’ is the second most disastrous, in terms of lethal toxic load likely over a large distance (3252 meters). In summary, the study reveals that given the masses of materials stored, and the conditions in which they are stored, there is a live risk of accidents in the storage vessels that would have far-reaching consequences. The industry thus poses a great risk to large areas of surrounding including densely populated villages (particularly Chinnakalapet and Kalapet) and the campuses of Pondicherry University and Pondicherry Engineering College. This paper demonstrates the utilizability of MAXCRED-II and also focuses attention on the need to bestow greater effort towards risk assessment. It is hoped that these studies will make plant managers conscious of the serious consequences that can result from accidents in their vulnerable units. Appreciation of the risk, we hope, will prompt them to develop accident prevention strategies and to put in position emergency preparedness plans to cushion the adverse impacts if accidents do occur.

Generalized expressions for estimating the current efficiency of ion-exchange membrane and diaphragm chlor-alkali cells

Comprehensive chlorine and caustic current efficiency equations were derived for ion-exchange membrane and diaphragm chlor-alkali cells using material balances that account for all common and significant reactive brine impurities and their respective interactions with Cl2 and/or NaOH. These generalized equations, formulated in terms of molar flow rates of the species entering, exiting, generated in or consumed in the cells, require a knowledge of the feed and depleted brine compositions to calculate the current efficiency of either an individual electrolyser or an entire circuit. It was shown that the global current efficiency expression can be degenerated to the various currently employed equations in the chlor-alkali industry for estimating the current efficiency with certain assumptions or approximations. These simplified assumptions and approximations, usually involving omission of some brine components or anolyte reactions, were shown to result in differences in the published current efficiency expressions. Disparities between the caustic and chlorine current efficiency of membrane and diaphragm cells were quantified and approaches to achieve either high ηCl2 or ηOH were also outlined. Current efficiency equations, based on an analysis of anode gases and anolyte composition, require an accurate measure of all the components in the feed and depleted brine. A simplified method, which is analytically less cumbersome, is also presented to estimate the caustic current efficiency of ion-exchange membrane chlor-alkali cells.

Atmospheric mercury species over central and Northern Europe. Model calculations and nordic air and precipitation network for 1987 and 1988

A chemical scheme based upon current knowledge of physicochemical forms and transformation reactions of atmospheric mercury has been implemented into a regional pollutant dispersion model for Europe. Existing databases for anthropogenic mercury emissions in Europe have been updated for 1987 and 1988 using new information on source data from eastern European countries including the former German Democratic Republic. Concentrations of total gaseous and particle associated mercury in air and mercury in precipitation calculated by the model are compared with observed values at Roervik in southwestern Sweden, Aspvreten, south of Stockholm and other locations of the Nordic network, on a daily basis. The results show that the model is capable of simulating long-range transport of mercury from Central Europe to Scandinavia including discrete events with peak concentrations in air and precipitation in the range of 10 ng m −3 and 100 ng l −1, respectively. Coinciding observed and calculated peak concentrations indicate that exceptionally high mercury emissions, most probably from chlor-alkali industry and lignite coal combustion in East Germany and Czechoslovakia, must have occurred in 1987 and 1988.

Report of the Electrolytic Industries for the Year 1993

not Available.

Electrochemical Reduction of Liquid CO 2: Drastic Enhancement of Current Density

A novel electrochemical reduction system has been developed in which liquid was reduced electrochemically at a Cu electrode producing , , , and . We have succeeded in reducing with a current density of 420 mA/cm2 and a current efficiency of 85%; the former is higher than that used in industrial electrolyses such as in the chloralkali industry. The Tafel plots indicate that the supply of is no longer limited by its mass transfer.

Mercury toxicokinetics in Wistar rats exposed to elemental mercury vapour: modeling and computer simulation.

The kinetics of total mercury (Hg) absorption, distribution and elimination in Wistar rats exposed for long periods to elemental mercury vapour (Hg zero) in the Idrija mercury mine were studied. From the experimental data base a compartmental model was built as a framework for experimental data interpretation and prediction of organ mercury levels under different conditions. Using the model the exposures of rats under conditions comparable to those of professionally exposed workers (mercury miners, workers in the chloralkali industry) and individuals with amalgam fillings were simulated.