MXPA97008114A - Process for the preparation of a disinfectant solution containing chlorine dioxide, for the treatment of a - Google Patents

Abstract

Through the invention, an operation arrangement for an electrically operated window protection device of the type comprising a flexible protection body (1), which is wound on a roller (2) placed on or on a main frame, is provided. horizontal upper or window frame member and at a free end is connected with a lower rail (4) extending in the width of the window. The operating arrangement comprises, for moving the protective body in one direction, a traction element formed with a cord or cords (12, 13, 24) acting on the protective body and being wound on a placed winder device (11, 22, 23) in a lower main frame frame member and with an attached electric drive motor (9). To move the protective body (1) in an unrolled direction, the traction element (12, 13, 24) is, from the winder device, guided along both the opposite main frame and the side frame sections of the frame. window for connecting with the lower rail (4), while the movement of the protective body in the opposite winding direction is a known way to be effected by a spring force acting on the roller (2) during unwinding of the pulling element of the winder device. As a special advantage, the traction element (12, 13, 24) can be connected with a separate bar profile (5) designed for later mounting on a lower rail (4) for a protective device already installed

Description

PROCESS FOR THE PREPARATION OF A DISINFECTANT SOLUTION! WHICH CONTAINS CHLORINE DIOXIDE. FOR THE TREATMENT OF ACTTA Description of the invention Aqueous solutions of chlorine dioxide are frequently used in the water treatment technique due to the high oxidizing power of chlorine dioxide. The field of application in this extends from the disinfection of water for drinking or drinking and bathing water or spas, to the treatment of wastewater and wastewater. In comparison with the classic oxidizing disinfectants such as chlorine and hypochlorite, chlorine dioxide is characterized by an excellent ecological balance. For example, when chlorine dioxide is used, only small or small amounts of AOX ("Adsorbable Organic Halogen Compounds") are formed, a parameter that encompasses all chlorine, bromine and iodine compounds with a great variety of risk potentials. be adsorbed by activated carbon). For example, it is known from the German patent publication DE-PS 843 999 that for the preparation of chlorine dioxide it is possible to start from (chlorites) a chlorite, for example sodium chlorite, and oxidize the latter with an oxidizing agent, for example sodium persulfate (sodium disulfate peroxide), in aqueous solution in accordance with the generic equation 2NaCl02 + Na2S208? 2C102 + 2Na2S04 to obtain chlorine dioxide. In order to obtain a reaction rate as high as possible, in the case of this known process the reaction solution is adjusted to a pH value of 5-9, optionally with the aid of a buffer, contains the oxidizing agent in stoichiometric excess and It can be heated up to 65 ° C to further enhance the reaction. The chlorine dioxide that is formed is continuously expelled from the reaction solution by the introduction of an inert gas, and captured in an absorption tower. Even though this procedure produces chlorine dioxide of very high purity with good yields, referred to the chlorite used, it is strongly limited in its possibility of application and does not lend itself very well to be used "in situ" on an industrial scale - both to the high cost of the apparatuses of the installation for the separation of the chlorine dioxide, as well as due to the high risk of explosion of the chlorine dioxide in gaseous form. And on the other hand, in many cases of application, such as the treatment of drinking water or drinking water, the possibility of renouncing the separation of chlorine dioxide and using the reactive solution as such for disinfection must also be discarded. of the reaction because the solution still contains too much residual chlorite and also has the poisonous impurity of chlorate, which was formed as a by-product. The object of the invention is to improve the known method for obtaining a "single reaction vessel" reaction, so that the reacted reaction solution containing the chlorine dioxide can be used directly as such for disinfection purposes, and directly suitable, for example, for the treatment of drinking water or drinking water. This object is achieved according to the invention by preparing an aqueous reactive solution comprising chlorite and a halogen-free oxidizing agent, containing the oxidizing agent up to twice the stoichiometrically required amount and adjusting to a pH value between 5.5. and 9.5, which is reacted for so long at room temperature until the chlorite has almost completely converted to chlorine dioxide. The invention is based on the knowledge that by means of a consequent conduction of the reaction it is possible to transform the reactive solution into a product solution containing chlorine dioxide that no longer contains practically any residual chlorite (in the ideal case nothing of chlorite), and it is also free of chlorate and other undesirable byproducts. Surprisingly it was discovered that this is possible through the joint action of several factors, namely, Adjust as immediately as possible the pH value of the solution at a pH value of 5.5 to 9.5, preferably 6 to 9, Excess oxidizing agent in a molar ratio of chlorite to the oxidizing agent between 1 and 2, preferably between 1.75 and 2, - Reaction time sufficiently long at room temperature. The commercially available chlorite solutions are kept very alkaline for reasons of inalterability during storage, which results in the reactive solution having a pH value of approximately 12 if no measures are taken to correct this ( at least during the initial phase). With such a high pH value a disproportionation in chlorite and chlorate of the chlorine dioxide formed is inevitable. It was now discovered that with pH values below 9.5 the tendency to disproportionation of chlorine dioxide disappears, but nevertheless the stability of the chlorite solution is sufficiently assured in all cases during the duration of the reaction. Only with pH values below 5.5 is it possible to count on sufficient stability of the chlorite solution. Therefore, the reactive solution is passed as soon as possible to a range of the pH value in which both the educt (chlorite) and the product (chlorine dioxide) are stable, and in which the oxidation reaction it can pass without harmful side reactions (neither of the decomposition of the chlorite product nor of the decomposition of the product chlorine dioxide). Higher temperatures favoring the formation of chlorite are avoided, and sufficient oxidizing agent is made available. With this, almost no chlorate is formed in the reactive mixture, and the chlorite used is almost quantitatively converted to chlorine dioxide. For the preparation of the aqueous reaction mixture, a chlorite solution is conveniently mixed with a solution of the oxidizing agent, the rapid adjustment of the pH value of this mixture, which is important for the success of this process, is carried out by means of a proton donor, which is conveniently in a dissolved state, and which reduces the pH value of the solution. This proton donor can be added in dosed form to the two reagents during the mixing process, but nevertheless it is contained within the solution of the oxidizing agent in a preferred embodiment of the invention. A particular advantage of the invention resides in the fact that a user can be provided with a reactive link constituted by two components, and the user only has to mix these two in a predetermined proportion so that it can be prepared at any time that is required. present the need for a fresh solution of chlorate-free chlorine dioxide. Eventually the component containing the oxidizing agent and the proton donor can be provided in the solid state for the user to transform into a solution, which is particularly convenient when the solution of the oxidizing agent alone can not be maintained sufficiently unchanged. during storage, apart from which boarding costs are also reduced. The chlorite solution can in principle also be prepared by the user himself by dissolving solid sodium chlorite (stabilized with sodium chloride), which however is less convenient because solid sodium chlorite is classified as a hazardous product by the transport companies. The concentration of the chlorite, and therefore the oxidizing agent, in the reactive solution exerts an influence on the development or course of the process. However, it is advisable to avoid concentrations that are too high in order to avoid the formation of too high a concentration of chlorine dioxide in the mixture that reacted. Oxidizing agents which are preferred are peroxide disulfates, but other halogen-free oxidizing agents, such as permanganates, Fenton reagent or ozone, can be used. The oxidizing agent must be sufficient, according to its type and quantity, for the total oxidation of the chlorite in the aqueous reactive mixture, and must be present in excess of the stoichiometry. Then it will not be consumed completely during the reaction in which the chlorine dioxide is formed. This may be convenient in many cases of application, in particular to oxidize in situ with the excess of oxidizing agent the chlorine dioxide which suffered a reduction during the use of the chlorine dioxide solution, for example, due to organic impurities contained in the chlorine dioxide solution. treated water, through which the overall effect of disinfecting and treatment silification is improved. This is considered a special additional advantage of the invention, which is not possible in the case of the known process. For the purposes of the invention, all those substances compatible with the oxidizing agent and chlorite, which have the ability to reduce the pH value of the reactive mixture by the donation of acid protons, are considered as proton donors. Typical examples are sodium hydrosulfate, sodium hydrophosphate and acid salts such as iron (III) chloride or aluminum chloride. Continuing with the development of the idea of the invention, it is convenient to add to the aqueous chlorite solution or to the aqueous solution of the oxidizing agent a buffer substance which forms an effective buffer system between pH 5.5 and pH 9.5 in the reaction mixture. By this, an additional stabilization of the adjusted pH value is obtained. Under the concept or term "buffer substance" are included herein all those compounds that by the donation or absorption of one or several protons can form the acid or conjugate base of an effective buffer system, the system being The buffer must no longer itself comprise the buffer substance. The buffer substance has a basic reaction in the reaction mixture if it is present in the chlorite solution, and has an acid reaction if it is present in the solution of the oxidizing agent. An example of a buffer substance contained in the chlorite solution and which is suitable for the purposes of the invention is sodium carbonate, in which the anion (C03 ~) forms hydrogen carbonate or carbonic acid by absorbing one. or two protons, that is, the base or the conjugate acid of a hydrogen carbonate / carbonic acid buffer. An example of a buffer substance that can be added to the solution of the oxidizing agent is sodium hypophosphate (acid) which forms a carbonated phosphate / bicarbonate phosphate buffer in the reaction mixture. Other buffer systems are also suitable, provided that they form an effective buffer system in the range of pH required, and that they are harmless to drinking or drinking water. Surprisingly, a particularly rapid and especially fully quantitative reaction of the chlorite in chlorine dioxide is obtained if at least catalytic amounts of transition metal ions are introduced into the reaction solution, preferably in the form of silver salts, but also in the form of of iron salts, manganese salts or (as long as this is tolerable for the subsequent application of the chlorine dioxide solution), copper salts. The origin of this effect has not yet been established with accuracy, but it is likely that these ions directly intervene in the mechanism "redox" of the reaction. In principle, they can be added to the reactive mixture at any time, that is, for example, they could already be present in the aqueous solution of chlorite or oxidizing agent. However, a subsequent addition of the ions is also possible. Precipitation products that may eventually be produced as an accompanying product (for example AgCl or the like) in the reaction mixture or product, which would be noticed by a cloudiness, can be separated in the usual way after having been obtained a sufficient degree of reaction. The invention is explained below on the basis of exemplary embodiments.

Example 1 Preparation of an aqueous solution containing chlorine dioxide 16. 45 grams of a commercially available aqueous solution of sodium chlorite, containing 300 grams of sodium chlorite per liter of solution (for example Sodium Chlorite 300 W from Degussa) are diluted with water until 900 ml. To this dilute sodium chlorite solution, 2 grams of sodium carbonate are added and dissolved in it. The resulting solution (educte solution 1) has a pH value of about 12. 5.33 grams of peroxide sulfate and 2.15 grams of sodium hypophosphate (acid) are dissolved in 100 ml of water. The pH value of the resulting solution (educte solution 2) is approximately 2. The solution of educte 2 is added to the solution of educte 1 and intermixed with the latter. Within a period of 1 minute the pH value is adjusted to 7.5. This pH value is stabilized by the resulting buffer of sodium carbonate / carbonic acid. Chlorine dioxide develops in the aqueous reaction mixture according to 2 CIO, + S2082 ~? 2 CIO, + 2 SO, 2- Since none of the educts of the indicated reaction equation is in excess, approximately 12 hours are required until they have reacted in their entirety. After the reaction approximately 3 grams of chlorine dioxide are present per liter of solution.

Example 2 Preparation of an aqueous solution containing chlorine dioxide Proceed in the same way as in the example 1, but nevertheless for the preparation of the solution of the educt 1 5.04 grams of a hodgepodge (mixture) of solids containing 80% by weight of sodium chlorite and 20% by weight of sodium chloride are mixed first with 2 g of Sodium carbonate and then with water, until the total volume reaches 900 ml. The mixture of solids and sodium carbonate dissolve in the water, so that in the resulting solution (solution of educt 1) the pH value is adjusted by approximately 12.

Example 3 Catalytic acceleration of the reaction For comparison purposes, an aqueous solution containing chlorine dioxide was prepared on the one hand (a) without the presence of Ag + ions, and on the other hand (b) in the presence of Ag + ions. a) 2.81 g of NaHS04 and 9.5 g of Na2S208 are dissolved in 100 ml of water, whereby the pH value is adjusted by approximately 2. The solution obtained is mixed with 900 ml of an alkaline solution (pH 12), which contains 3 g of C102 ~ and 2 g of Na2C03. In a few seconds the pH of the reactive mixture is adjusted between 7 and 8. After 12 days a reaction rate of 95% is reached, referring to the chlorite. With respect to the development of the reaction, we refer to figure 1 below. The procedure is the same as for (a), but 35 mg of AgN03 are immediately added to the reaction mixture. After 12 days a reaction rate of 99.8% referred to chlorite is reached. With respect to the development of the reaction, we refer to figure 1 below.

Claims (2)

1. CLAIMS Process for the preparation of a disinfectant solution containing chlorine dioxide and can be applied directly for the treatment of water, which is characterized in that it comprises the following steps: preparing a reactive aqueous mixture containing chlorite and a free oxidizing agent of halogens, being that the oxidizing agent is contained in an amount that is between one and two times the amount stoichiometrically required to oxidize the chlorite and turn it into chlorine dioxide, - adjust the pH value between 5.5 and 9.5 in the mixture of aqueous reaction, reacting the reaction mixture at room temperature without removing the resulting chlorine dioxide. Process according to claim 1, characterized in that an aqueous solution of the chlorite with a pH value above 9.5 and an aqueous solution of the oxidizing agent are mixed together to prepare the mixture of the aqueous reaction, and the solution of the oxidizing agent contains a proton donor to adjust the pH value.
2. 2. Process according to claim 1 or 2, characterized in that in the aqueous reaction solution it is adjusted to a pH value between 6 and 9. 4. Process according to one of the preceding claims, characterized in that sodium peroxodisulfate is used as the oxidizing agent for the oxidizing agent solution and that the molar ratio of chlorite to peroxodisulphate is adjusted to a value between 1 and 2, preferably between 1.75 and 2. 5. Process according to claim 2, characterized in that the aqueous chlorite solution or the aqueous solution of oxidizing agent comprises a buffer substance, which forms a buffer system in the solution that is effective between pH 5.5 and pH 9.5. 6. Process according to claim 5, characterized in that the aqueous chlorite solution contains sodium carbonate as a buffer substance. 7. Process according to claim 5, characterized in that the aqueous solution of the oxidizing agent contains sodium hypophosphate as a buffer substance. 8. Process according to one of the preceding claims, characterized in that the reaction mixture contains a catalytically effective amount of ions of a transition metal, preferably silver ions or copper ions. 9. Process for the treatment of water characterized in that it comprises the following steps: preparing a reactive aqueous mixture containing chlorite and a halogen-free oxidizing agent, being that the oxidizing agent is contained in an amount that is found between one and two times the amount stoichiometrically required to oxidize the chlorite and convert it to chlorine dioxide, adjust the pH value between 5.5 and 9.5 in the aqueous reaction mixture, react the reaction mixture at room temperature without removing the dioxide Resulting chlorine, mix the reaction mixture containing chlorine dioxide with an aqueous solution to be treated, such as drinking or drinking water, water for baths, use water or sewage. 10. Process according to claim 9, characterized in that the reaction mixture contains a catalytically active amount of transition metal ions, preferably silver ions or copper ions. SUMMARY In the present process, starting from an aqueous reaction solution comprising a chlorite and a halogen-free oxidant agent in stoichiometric excess up to twice. This reactive solution is adjusted to a pH value between 5.5 and 9.5, preferably between 6 and 9, and is reacted for so long at room temperature until the chlorite has almost completely converted to chlorine dioxide. In this way, a solution containing chlorine dioxide free of residual chlorite is obtained, but also free of chlorate and other undesirable byproducts, and which can be used directly as such for water treatment. For the preparation of the reaction mixture, preferably an aqueous solution of the chlorite with a pH value above 9.5 and an aqueous solution of the oxidizing agent are mixed with each other, the pH value of the aqueous reaction mixture being with the help of a proton donor contained in the oxidizing agent solution. The user can therefore conveniently be provided with a reactive link consisting of two components which already only have to mix in a predetermined proportion so that a fresh solution of chlorate-free chlorine dioxide can be prepared therefrom. Additionally, it is convenient to add a buffer substance to the aqueous chlorite solution or to the aqueous solution of the oxidizing agent, which forms an effective buffer system in the reactive mixture between a pH of 5.5 and a pH of 9.5. By this, an additional stabilization of the adjusted pH value is achieved. The preferred presence in the reaction mixture of at least catalytic amounts of silver ions or of other transition metal ions exerts a positive influence on the reaction of chlorite ions to be converted into chlorine dioxide.