Spontaneous decomposition of industrially manufactured aqueous solutions of sodium hypochlorite was studied. The rate constants of the decomposition reactions were calculated for different pH values.In view of the exceedingly high toxicity and volatility of metallic mercury (MPC for habitats 0.0003 mg m !3 ) [1] and its wide use, the problem of efficient salvation in tackling with possible mercury spillage events remains a matter of current interest. For this purpose, new demercurization methods are being developed and the already existing techniques are being improved. At present, the most widely used methods are those in which mercury is oxidized with strong oxidizing agents [2,3]. In developing a demercurizer, with industrially manufactured sodium hypochlorite (HC) solutions as an oxidizing agent, it became necessary to assess the stability of solutions of this kind in storage and to study the oxidizing activity of these industrial solutions at various pH values.HC solutions are nonequilibrium systems that undergo spontaneous decomposition. The problem of spontaneous decomposition of HC solutions has been extensively studied. The influence exerted by the concentration, temperature, and acidity on decomposition processes has been analyzed and the possible mechanisms and kinetic characteristics of decomposition have been reported [4 38]. In the known studies, solutions of both calcium and sodium HC were examined. Model solutions have been mostly studied, with the HC solutions having low concentrations: 0.013 0.20 M in terms of active chlorine.The aim of this study was to assess the stability of industrially manufactured concentrated HC solutions in order to determine the maximum shelf life of solutions of this kind. Another goal was to determine the kinetic characteristics of real solutions used to prepare the demercurizing agent.The choice in developing the demercurizer was made in favor of sodium HC, taking into account its availability as a solution, high content of active chlorine, and high stability against decomposition in an alkaline medium (compared with calcium HC) [9]. The behavior of the solutions was analyzed at two temperatures, 25 and 35oC, in view of the regional climatic conditions (the maximum summer temperature is not, as a rule, higher than 35oC). EXPERIMENTAL As object of study served industrially manufactured (Berezniki Soda Plant Open Joint-Stock Company) sodium HC solution with a concentration of 180 3 200 g l !1 in terms of active chlorine. Model solutions were prepared by passing at (0 35oC) Cl 2 obtained by reacting chemically pure hydrochloric acid with KMnO 4 through a NaOH solution containing no carbonates. The excess amount of the alkali was about 20 g l !1 . The reaction vessel was cooled with a mixture of NaCl and ice. The pH values of the solutions were measured with an EV-74 ionometer with glass and silver chloride electrodes.In stability studies, the alkaline (pH 13.5) HC solutions under study were thermostated in hermetically sealed polyethylene jars for 3 months. The pH value...
This paper describes a fire and explosion suppression formulation with increased flowability that ensures fast operation and high efficiency of an active explosion suppression system (complete fire and explosion suppression time = 2.25 ms; spraying capacity = over 98%). For the first time, the possibility of using mesoporous materials of different structures with high specific surface area as flow additives for these formulations has been reported. This also covers the results of an experimental study on the influence of various mesoporous silica materials used as additives on the rheological characteristics of a monoammonium phosphate (MAP)-based fire and explosion suppressant. Particular attention is paid to analysis of the results of the experiments in which the mesoporous materials are protected from moisture via poly(methylhydrosiloxane) hydrophobic modification. The study of the rheology of powders indicates that the flow parameters depend on the surface characteristics of silica nanoparticles and their size and concentration. The incorporation of superhydrophobized silica into MAP leads to a decrease in the cohesion force and an increase in the flow function ff (composition contact angle > 163°). The amount of superhydrophobic silica also affects the autoadhesion forces between particles. It has been established that the minimum resistance of a fire and explosion suppression powder to the flow occurs when modified nanoparticles with SBA-15-type structure are used as additives. The efficiency of hydrophobized silica materials as additives increases greatly with a decrease in the size of their particle agglomerates. The joint use of SBA-15 and Aerosil 380 silicas makes it possible to improve the rheological properties of the fire and explosion suppression formulation and to significantly increase its flowability.
This paper deals with metal oxides/carbon black (MOs/CB) composites and their influence on the thermal decomposition of ammonium perchlorate. It is shown that the developed synthesis method can be used to form the nanosized metal oxide coating on the surface of the carbon carrier. The SEM and DLS data demonstrate that the particle size for the MOs/CB catalysts ranges from 200 to 500 nm. The XRD analysis has revealed that the bivalent copper and nickel oxides are formed on the surface of the carbon support. The DSC study on the effect of MOs/CB on the thermolysis of ammonium perchlorate shows that the MOs/CB catalysts contribute to a lowering in the peak temperatures of the low and high temperature AP decomposition stages. It has also been found that bioxide MOs / CB catalysts are more efficient in this case than monoxide catalysts. The evaluation of mass spectrometry results for the decomposition products of AP formed in the presence of carbonbased mono-and bioxide catalysts makes it possible to conclude that the carbon base of metal oxide catalysts causes the low-temperature AP decomposition to proceed deep in the composite. MOs/CB catalysts, in turn, ensure a more complete decomposition of ammonium perchlorate followed by the formation of a greater number of oxidized and reduced forms of low molecular weight composites. It has been established that, for bioxide MOs/CB catalysts, the amount of chlorine formed exceeds the corresponding value for pure AP by more than ~4 times.
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