A method and system for electrochemically regenerating hydroxide (MOH) and carbon dioxide (CO.sub.2) from an alkali metal carbonate (M.sub.2CO.sub.3) via an electrochemical reactor that can replace a conventional thermochemical causticizing operation in a DAC system. The electrochemical reactor comprises: a cathode having an inlet for receiving an electrolyte feed stream comprising MOH, M.sub.2CO.sub.3 and H.sub.2O, and an outlet for discharging an electrolyte product stream comprising MOH, M.sub.2CO.sub.3, H.sub.2O and H.sub.2; a porous hydrophilic transport barrier in adjacent contact with the cathode; a porous hydrophilic anode in adjacent contact with the transport barrier configured and operable to generate CO.sub.2 in the presence of MOH while suppressing their recombination; a porous hydrophobic CO.sub.2 and O.sub.2 separation barrier in adjacent contact with the anode; and a product gas exit channel in adjacent contact with the CO.sub.2 and O.sub.2 separation barrier and for discharging an anode product stream comprising at least CO.sub.2.

[Problem] To provide a stacked structure including electrodes that can effectively prevent misalignment between units. [Solution] A stacked structure 2 including electrodes 232, 332, 412, 233, 333, 422, wherein multiple units 23, 33, 24, 41, 42 including flat units are stacked and fastened by fasteners 25, the respective units 23, 33, 24, 41, 42 comprising frame-shaped fastening portions 237a, 237b, 337a, 337b, 247a, 247b, 417a, 417b, 427a, 427b on outer peripheral portions on both surfaces thereof, being stacked by the surfaces of the respective fastening portions 237a, 237b, 337a, 337b, 247a, 247b, 417a, 417b, 427a, 427b being pressed against each other, and being formed so that the width of fastening portions 247a, 247b, 337a, 337b, 427a, 427b on one unit is different from the width of fastening portions 237a, 237b, 417a, 417b on another unit.

The invention describes an electrochemically enabled process for the production of magnesium hydroxide from mineral resources, using acid produced in the electrolysis cell for heap or vat leaching of the mineral resources. The process also enables extraction of nickel, cobalt, iron and silica from the mineral resources, and reduction or elimination of asbestos fiber. The produced magnesium hydroxide is used for carbon dioxide capture and sequestration from gaseous and liquid environments.

The invention describes an electrochemically enabled process for the production of magnesium hydroxide from mineral resources, using acid produced in the electrolysis cell for heap or vat leaching of the mineral resources. The process also enables extraction of nickel, cobalt, iron and silica from the mineral resources, and reduction or elimination of asbestos fiber. The produced magnesium hydroxide is used for carbon dioxide capture and sequestration from gaseous and liquid environments.

Various embodiments relate to methods and systems for removing phosphorus and/or nitrogen from water. A method of removing phosphorus and nitrogen from water includes passing starting material water including nitrogen and phosphorus through an elevated pH phosphorus removal stage. The method includes passing the water through an electrolytic nitrogen removal stage. The method includes passing the water through a galvanic phosphorus removal stage. The water produced by the method has a lower phosphorus concentration and a lower nitrogen concentration than the starting material water.

Various embodiments relate to methods and systems for removing phosphorus and/or nitrogen from water. A method of removing phosphorus and nitrogen from water includes passing starting material water including nitrogen and phosphorus through an elevated pH phosphorus removal stage. The method includes passing the water through an electrolytic nitrogen removal stage. The method includes passing the water through a galvanic phosphorus removal stage. The water produced by the method has a lower phosphorus concentration and a lower nitrogen concentration than the starting material water.

Method and system are disclosed for the production and use of a chemical compound, where a given amount of CO.sub.2 is emitted in the production and the use, including producing a second chemical compound that is required for the production or the use of the first compound, where the production of the second compound consumes CO.sub.2 and sequesters it from the atmosphere so that the total net CO.sub.2 emitted in the production and use of the first compound is now reduced. In one embodiment, the second chemical compound is a negative-CO.sub.2-emissions hydrogen, oxygen or chlorine gas produced in an electrolytic cell.

The present disclosure relates to the field of resource utilization-oriented treatment technologies for wastewater, and more particularly, to a resource utilization-oriented treatment method for a spent electroless nickel plating bath. The method includes oxidation de-complexation, synchronous precipitation of nickel and phosphorus, secondary precipitation of nickel, and resource utilization of sodium salt. In the present disclosure, in a reaction process, no sludge is generated to avoid secondary pollution to the environment. Further, the present disclosure has the advantages of short flow and less chemical use, greatly reducing treatment costs. In this way, this method is a low-cost and clean resource utilization-oriented treatment method capable of achieving resource utilization-oriented recovery of nickel, phosphorus, sodium, sulfate radical, or chlorine in the spent electroless nickel plating bath.

An apparatus and method are provided for the electrochemical production of hydrogen, oxygen and metal hydroxide wherein the metal is derived from a metal silicate. The process involves the electrolysis of a metal salt solution where hydrogen and a metal hydroxide are produced at the cathode, and oxygen, or chlorine, and an acid are produced at the anode. The acid is reacted with a metal silicate producing a soluble metal salt and water that is used in turn to make solid or dissolved metal hydroxide. The net CO.sub.2 and acid gas emissions of the invention and its products may therefore be significantly reduced or turned negative.

An apparatus and method are provided for the electrochemical production of hydrogen, oxygen and metal hydroxide wherein the metal is derived from a metal silicate. The process involves the electrolysis of a metal salt solution where hydrogen and a metal hydroxide are produced at the cathode, and oxygen, or chlorine, and an acid are produced at the anode. The acid is reacted with a metal silicate producing a soluble metal salt and water that is used in turn to make solid or dissolved metal hydroxide. The net CO.sub.2 and acid gas emissions of the invention and its products may therefore be significantly reduced or turned negative.