Papers by Keyword: Chlorine

Abstract: Malaysia is one of the countries that strongly promotes industrial development. Therefore, industrial activities have grown rapidly since the 1980s. However, since the development of the country's industry, the country has experienced several major accident hazards, thus sacrificing many lives, causing assets and environmental destruction. For example, Bright Sparklers explosion incident that occurred on 7^th of May 1991 in Sungai Buloh had killed 26 people, injuring more than 100 people and damaging more than 200 residential properties. While at Johor Port Sand Warehouse, a large fire had occurred at Petronas terminal and destroyed three storage tanks and 720,000 liters of petroleum and 240,000 of aviation fuel. This fire has resulted in 100 firefighters. In the latest 2018 incident, Malaysia was shocked by a major fire at Kemaman Bitumen Company. The results of these three insights indicate that a comprehensive analysis needs to be made to assess land use and other risk management decisions. Malaysia is the world’s largest rubber glove producer, therefore, the quantity usage of chlorine is high. As noted by Agency for Toxic Substances and Disease Registry, chlorine is harmful to human body when it is handled improperly. In this paper, a study was conducted to assess the impact of the use of chlorine gas at the rubber glove manufacturing plant. Quantitative risk analysis is used as a tool to prevent major failure in storage, production and transportation of chemicals has been issued. Therefore, this paper investigates the consequences of risk posed by chlorine incident release under wind rose effect at rubber glove manufacturing industry.

Abstract: Over 150 μm thick epilayers of 4H-SiC with long carrier lifetime have been grown with a chlorinated growth process. The carrier lifetime have been determined by time resolved photoluminescence (TRPL), the lifetime varies a lot between different areas of the sample. This study investigates the origins of lifetime variations in different regions using deep level transient spectroscopy (DLTS), low temperature photoluminescence (LTPL) and a combination of KOH etching and optical microscopy. From optical microscope images it is shown that the area with the shortest carrier lifetime corresponds to an area with high density of structural defects.

Abstract: The results of investigation of changes in electronic structure and magnetic properties of multilayer graphene nanoclusters (nanographites) occurring during their interaction with adsorbed chlorine molecules are presented. The found reversible decrease in the density of states of current carriers D(E_F) at the Fermi energy E_F can be explained by the spin-splitting of edge π-electron states in nanographites induced by the enhancement of electron-electron interactions due to increase of the D(E_F) at partial transfer of the electron density from nanographites to chlorine adatoms. The revealed irreversible decrease in the concentration of localized spins indicates that the electron spins of 3p-orbitals of chlorine and unpaired (dundling) σ-orbitals of edge carbon atoms are coupled also at this interaction, i.e. the edge covalent compound of nanographite with chlorine forms. Character of changes in the spin-relaxation rate of π-electrons depending on the amount of adsorbed chlorine molecules and on temperature in chlorinated samples are also consistent with the above model of nanographite-chlorine interaction.

Abstract: The influence of chlorine has been investigated for high growth rates of 4H-SiC epilayers on 4o off-cut substrates. Samples were grown at a growth rate of approximately 50 and 100 μm/h and various Cl/Si ratios. The growth rate, net doping concentration and charge carrier lifetime have been studied as a function of Cl/Si ratio. This study shows some indications that a high Cl concentration in the growth cell leads to less availability of Si during the growth process.

Abstract: Oxidant flushing of the raw water distribution system (RWDS) affects the degradation of dissolved organic matter (DOM). The characteristic of DOM after chlorine (NaOCl), chlorine dioxide (ClO₂) and their combination (NaOCl/ClO₂) were evaluated by dissolved organic compound (DOC), spectrophotometry and fluorescence of DOM in simulated RWDS. The results suggested that oxidant flushing had negative effect on DOC removal, especially for NaOCl/ClO₂, but it was resumed with a higher recovery rate compared to ClO₂ and NaOCl. The biodegradable of DOM increased after oxidant flushing, and related to DOC degradaion. Overall fluorescence of DOM intensity has a decrease potential after oxidant flushing, particularly for tryptophan-like fluorescence. These results indicated that NaOCl/ClO₂ has less negative impact on the resume of DOM degradation in RWDS compared with corresponding single oxidant.

Abstract: Drinking water supplies continue to be a major source of human disease because many of them remain unsafe and vulnerable. The aim of this study was to investigate the levels of trihalomethanes formation and chemical and microbiological quality through four raw surface waters as well as finished tap waters. The seasonal changes on trihalomethane formation and concentration of organic precursors were examined. Results show that disinfection for Algerian drinking water reduces the risk of pathogenic infection but may pose chemical threat to human health due to high levels of by-products such as trihalomethanes, when the organic and inorganic precursors are present in water. The level of THM precursors vary between different catchment areas and between different water treatment plants, and seasonally. Such work may be interesting to help management strategies and to assist drinking water treatment plants in DBP control processes for increasingly impaired water sources.

Abstract: Copper smelting gas producing sulfuric acid process produces contaminated acid which contains high concentration of fluorine, chlorine, arsenic and copper, zinc, lead, cadmium and other metals. The sulfide precipitation and lime neutralization methods have been used at present. Those methods have some deficiencies as which produces a lot of hazardous and unwieldy solid wastes, spends huge processing cost, reuse difficultly the water after treatment. In this paper, according to characteristics of this kind of smelting contaminated acid, evaporation condensing process and the feasibility of recycling arsenic, sulfuric acid and valuable metals were studied. Under the condition of atmospheric heating evaporation, this study explored the distribution characteristics of fluorine, chlorine, sulfate radical, arsenic in condensate and in concentrate and the crystallization removal rates of arsenic trioxide in concentrate at different temperatures and different enrichment ratios. The results show arsenic, fluorine and chloride have good removal rates from contaminated acid by evaporation condensing process. Temperature at 130°C, enrichment multiple in 6~7, the removal rate of arsenic, fluorine and chlorine reached 62%, 88%, 77%. The results also show evaporation condensing process has good application prospects to treat smelting contaminated acid.

Abstract: An unsymmetrical diarylethene derivative bearing both phenyl and thiophene moieties, in which a cyano group was substituted at the ortho-position of the phenyl ring and a chlorine elements was substituted at the five-position of the thiophene ring, was synthesized. At the same time, its photochromic properties and fluorescence switch were investigated in detail. The results showed that this compound exhibited reversible photochromism, undergoing reversible cyclization and cycloreversion reactions upon alternating irradiation with UV and visible light in solution , and its absorption maxima were observed at 501 nm in hexane. The fluorescence intensity of diarylethene decreased along with the photochromism from open-ring isomer to closed-ring isomer upon irradiation with 254 nm UV light in hexane.

Abstract: In order to study the effect of chlorine (Cl₂) inactivating Cryptosporidium and Giardia in water, different factors as Cl₂ concentration, contact time, pH, temperature, turbidity and organic content which might influence the inactivation were studied by using fluorescence staining method. With the Cryptosporidium and Giardia was 1×10⁶ cysts/mL, turbidity 1.0NTU, temperature 22°C, pH 7.0, and after 280 min reaction, under the condition that the Cl₂ concentrations was 8.0mg/L, the inactivation ratio could be more than 99%. With increases in turbidity, the inactivating effect decreased. If the inactivating time achieved 360 min, it could meet the presetting inactivation ratio with turbidity 0.1~10.0 NTU. The inactivating capability of Cl₂ was found to be stronger under acidic than that under alkalic conditions. Inactivation rate improves with a temperature increase from 5 to 25°C, but decreases beyond this.

Abstract: Sulfate reducing bacteria (SRB) and iron reducing bacteria (IRB) that widely exist in water supply networks are the main microorganisms leading to metal corrosion in pipelines. Chlorine is widely used in drinking water supply systems. The concentration of chlorine with SRB declined rapidly after 10 mins and reached 0 mg/L finally whereas it decreased more slowly with IRB. If the concentration of chlorine is lower than 0.2mg/L, IRB cannot be sterilized. It indicates that at the end of water pipes where the concentration of chlorine is required to be 0.05mg/L, chlorine is not effective since the concentration is below the minimum requirement of removing IRB