Abstract: Peroxydisulfuric acid and salts thereof are produced electrochemically from an aqueous acid sulfate solution in a cascading series of bipolar electrolytic cells having a cell body frames of polyvinyl chloride which are bonded with a vinyl ester polymer. An aqueous solution of peroxydisulfuric acid and salts thereof are withdrawn from the anode compartment of the last cell in the series, and metal impurities are removed by treatment with an ion exchange resin. Hydrogen peroxide is produced by hydrolyzing persulfuric acid and salts thereof. The sulfuric acid produced is recycled to the first cell in the series of cascading electrolytic cells.

Abstract: A method of metallurgically joining dissimilar metal tubes using a connecting member clad metal tube in which the clad metal is the same or similar metal to a metal of one of the dissimilar tubes to be joined and is susceptible to bonding by welding. The underlying clad metal connecting member metal is a dissimilar metal which is susceptible to bonding by soldering.

Abstract: An electrochemical process for the production of a hydroxide solution and a sulfate by the electrolysis of a waste aqueous mixture of oxidizable sulfur impurities in the anode compartment of at least one electrolytic cell while producing a hydroxide solution in the cathode compartment of the cell. The process is particularly applicable to the treatment of spent caustic solutions obtained by scrubbing a hydrocarbon process stream contaminated with oxidizable sulfur impurities. The electrolytic cell used in the electrolysis process of the invention can use either a porous membrane or a cationic permselective membrane to separate the anode and cathode compartments of the electrolysis cell.

Abstract: A monopolar or bipolar filter press electrolyzer. The bipolar filter press electrolyzer can contain a bipolar electrode consisting of a planar metal anode and planar metal cathode electrically connected to respective planar current collectors which can be electrically connected by welding either directly or through an intermediate metal layer different than said metal anode or cathode, or by adhesive bonding utilizing an electrically conductive adhesive. The cell frames can be a molded thermoplastic polymer or laminated thermoplastic or thermosetting polymer sheets. The bipolar electrode assemblies can include at least a pair of thermoplastic or thermosetting cell frame units which can be assembled with either a single gasket or a polymer adhesive.

Abstract: Pulping chemicals and hemicellulose are recovered from a starting solution essentially free of lignin but containing a mixture of hemicellulose and caustic by electrolyzing this solution in the anolyte compartment of an electrolytic cell. By electrolysis, the concentration of caustic in the anolyte is decreased and the concentration of caustic in a catholyte of said cell is increased so as to allow recovery of about 60 to about 80 percent of the caustic present in the hemicellulose caustic starting solution.

Abstract: A process is disclosed for producing a dilute solution of an alkali or alkaline earth metal chlorate from a chlorine and carbon dioxide waste gaseous stream. The process of the invention can be combined in a continuous process for the production of an alkali or alkaline earth metal chlorate for use in a chlorine dioxide generator for the production of chlorine dioxide in which the waste gaseous stream from the chlorine dioxide generator is converted to a dilute solution of an alkali or alkaline earth metal chlorate and passed to an electrochemical cell for the generation of an alkali or alkaline earth metal sodium chlorate, the product of the electrochemical cell being in turn passed to the chlorine dioxide generator.

Abstract: A method has been devised for removing chromium ions from a chromium ion containing liquid and recovering chromium oxide in a usable form by (a) adjusting the temperature of the liquid to an optimal temperature to maximize reduction and simultaneous precipitation of the chromium oxide; (b) adding a reducing agent to the liquid to form a mixture, where the reducing agent is at least one inorganic sulfur compound selected from the group of sulfur compounds where sulfur is in the 4.sup.+ oxidation state; and (c) adjusting the pH of the mixture to a pH between 5 and 7; (d) optionally further adjusting the pH of the mixture to a pH between above 7 to 12; and (e) separating the chromium from the mixture.

Abstract: An integrated process for the production of alkali or alkaline earth metal chlorates and chlorine dioxide in which the chromium compound impurities in the alkali or alkaline earth metal chlorate aqueous solution produced by an electrochemical cell are removed and recycled to the electrochemical cell; a substantially chromium compound free alkali or alkaline earth metal chlorate is converted to chlorine dioxide and by-products; and the by-products are converted to substantially chlorine-free carbon dioxide, which is vented, and a dilute solution of an alkali or alkaline earth metal chlorate, which is recycled to the electrochemical cell.

Abstract: A method has been devised for removing chromium ion from a chromium ion containing liquid and recovering chromium oxide in an usable form by (a) adjusting the temperature of the liquid to an optimal temperature to maximize reduction and simultaneous precipitation of the chromium oxide; (b) adding a reducing agent to the liquid to form a mixture, where the reducing agent is at least one inorganic sulfur compound selected from the group of sulfur compounds where sulfur is in the 4.sup.+ oxidation state and (c) adjusting the pH of the mixture to a pH between 5 and 7.

Abstract: A process for precipitating and removing chromium compounds in which chromium is in the hexavalent state from aqueous liquids, particularly, alkaline earth metal or alkali metal chlorate-rich solutions containing chloride, chlorate, and bichromate ions produced by the electrolysis of brine. In the process, hydroxylamine, hydroxylamine sulfate, hydroxylamine formate or hydroxylamine hydrochloride is used as a reducing agent to react and co-precipitate at a neutral or acid pH with hexavalent chromium ions present in the aqueous liquid, the reaction and precipitation taking place, generally, at a pH of about 4.0 to about 6.5 and, a temperature of about 50.degree. C. to about 100.degree. C. Precipitated oxides and hydroxides of divalent and trivalent chromium can be removed, for instance, by filtration.