A process for using acid to leach metals from metal silicate, oxide, or oxide-hydroxide feedstock with subsequent alkalinization of the leach liquor, thereby bringing target metal ions into solution and separating the metals as hydroxides, oxides, or oxide-hydroxides. Electrodialysis is used to recycle acid and base in the process. Configurations of the electrochemical cell and means of combining cells in stacks and in series are provided that enable production of acid at high concentration allowing for decreased reactor volumes for leaching and precipitation and improved solid/liquid separation characteristics of the leached slurry.

A system for biological methane production and removing carbon dioxide from the methane comprises (a) a primary anaerobic digester adapted and arranged to generate a gaseous mixture comprising methane and carbon dioxide from organic materials; (b) an electrochemical reactor comprising at least one reactor cell including an anode spaced from a cathode by a porous ion exchange resin wafer with a cation exchange membrane between the anode and the resin wafer and a bipolar ion exchange membrane between the cathode and the resin wafer; the electrochemical reactor being adapted and arranged to capture gaseous carbon dioxide within the resin wafer as aqueous bicarbonate, and to electrochemically generate hydrogen gas at the cathode; and (c) a hydrogenotrophic methanogenesis bioreactor adapted and arranged to convert the bicarbonate and hydrogen from the electrochemical reactor to methane. An electrochemical reactor and a method for producing methane with reduced carbon dioxide content also are described.

A carbon dioxide electrolytic device includes: a carbon dioxide electrolysis cell having a cathode and an anode flow path, a cathode, an anode, and a first diaphragm; a first current regulator to supply a first current; a first gas/liquid separator to separate a first fluid from the anode flow path into a first liquid and gas; an electrodialysis cell having, first and second electrodes, first to fourth rooms, and second to fourth diaphragms; a second current regulator to supply a second current; at least one detector out of a first detector to detect a flow rate of the first gas or a concentration of carbon dioxide in the first gas, and a second detector to detect a pH or a concentration of at least one ion in the first fluid; and a first controller to regulate a second current, in accordance with at least one detection signal.

The present invention provides a process for the production of an organic acid from an aqueous medium of a monovalent salt of an organic acid using bipolar electrodialysis via a three compartment electrodialysis unit.

The present invention provides a process for the production of an organic acid from an aqueous medium of a monovalent salt of an organic acid using bipolar electrodialysis via a two compartment electrodialysis unit.

Disclosed are wastewater treatment systems and methods for semiconductor fabrication process. The method comprises performing first concentration on wastewater discharged from a semiconductor process chamber, and performing second concentration on concentrated wastewater or at least a portion of the wastewater concentrated by the first concentration. The step of performing the first concentration includes performing in a first electrodialysis apparatus an ion exchange between the wastewater and first treatment water. The step of performing the second concentration includes allowing the concentrated wastewater to circulate in a second electrodialysis apparatus, allowing second treatment water to circulate in the second electrodialysis apparatus, providing a power to an anode and a cathode of the second electrodialysis apparatus to perform an ion exchange between the second treatment water and the concentrated wastewater, and joining a portion of the concentrated wastewater to the second treatment water.