An electrochemical process implements, in a decoupled manner, a first step of electrolysis of an electrolyte to produce gaseous oxygen in a chamber and a second step of electrochemical conversion of H+ ions into gaseous hydrogen in a chamber which contains a liquid phase and a gas phase not dissolved in the liquid phase. Gaseous hydrogen produced in the conversion step is partly present in the gaseous headspace of chamber and as bubbles in the electrolyte, and partly dissolved in the electrolyte which is saturated with hydrogen. The electrolyte has at least one redox pair (A/B) forming at least one intermediate vector enabling the decoupling of the first and second steps. The interface between the gas and liquid phases is increased during the second step to accelerate the diffusion, from liquid phase to gas phase, of the dissolved hydrogen able to supersaturate the electrolyte. Pressurized gaseous hydrogen is then collected.

Recovery of noble metals (including the recovery of gold and/or silver from gold and/or silver containing material) is generally described. The gold and/or silver can be recovered selectively, in some cases, such that gold and/or silver are at least partially separated from non-silver and/or non-gold material. Gold and/or silver may be recovered from material using mixtures of acids, in some instances. In some cases, the mixture can comprise nitric acid and at least one supplemental acid, such as sulfuric acid, phosphoric acid, and/or a sulfonic acid. The amount of nitric acid within the mixture can be, in some instances, relatively small compared to the amount of sulfuric acid or phosphoric acid within the mixture. In some cases, the recovery of gold and/or silver using the acid mixtures can be enhanced by transporting an electric current between an electrode and the gold and/or silver of the material. In some cases, acid mixtures can be used to recover silver from particular types of materials, such as material comprising silver metal and cadmium oxide and/or material comprising silver metal and tungsten metal.

Recovery of noble metals (including the recovery of gold and/or silver from gold and/or silver containing material) is generally described. The gold and/or silver can be recovered selectively, in some cases, such that gold and/or silver are at least partially separated from non-silver and/or non-gold material. Gold and/or silver may be recovered from material using mixtures of acids, in some instances. In some cases, the mixture can comprise nitric acid and at least one supplemental acid, such as sulfuric acid, phosphoric acid, and/or a sulfonic acid. The amount of nitric acid within the mixture can be, in some instances, relatively small compared to the amount of sulfuric acid or phosphoric acid within the mixture. In some cases, the recovery of gold and/or silver using the acid mixtures can be enhanced by transporting an electric current between an electrode and the gold and/or silver of the material. In some cases, acid mixtures can be used to recover silver from particular types of materials, such as material comprising silver metal and cadmium oxide and/or material comprising silver metal and tungsten metal.

The present invention relates to a carbon-nanotube/nano-adsorption-material-based electrode and an electrochemical valuable-metal recovery device using the same, and more particularly to an environmentally friendly carbon-nanotube/nano-adsorption-material-based electrode and an electrochemical valuable-metal recovery device using the same, in which valuable metals selectively adsorbed from e-waste wastewater are oxidized using, as an anode, an electrode including carbon nanotubes and a nano adsorption material capable of selectively adsorbing valuable metals and are simultaneously reduced at a cathode, thereby separating and recovering valuable metals.

The present invention relates to a carbon-nanotube/nano-adsorption-material-based electrode and an electrochemical valuable-metal recovery device using the same, and more particularly to an environmentally friendly carbon-nanotube/nano-adsorption-material-based electrode and an electrochemical valuable-metal recovery device using the same, in which valuable metals selectively adsorbed from e-waste wastewater are oxidized using, as an anode, an electrode including carbon nanotubes and a nano adsorption material capable of selectively adsorbing valuable metals and are simultaneously reduced at a cathode, thereby separating and recovering valuable metals.

The invention relates to a method of recovering Pt or Ag or Pt and Ag from a sulfate solution on an electrode. In particular, the invention concerns a method for recovering Pt or Ag or Pt and Ag from base metal bearing process solution, particularly from a hydrometallurgical sacrificial metal bearing solution containing Zn and/or Ni. In general, the method of the present invention can be used for recovery of precious metals, which are dissolvable in sulfuric acid, from sulfate media based solutions. In addition to Pt and Ag, especially Pd should be mentioned. Deposited precious metal(s) can be recovered from the electrode or the deposition containing electrode can be used as such.

The invention relates to a method of recovering Pt or Ag or Pt and Ag from a sulfate solution on an electrode. In particular, the invention concerns a method for recovering Pt or Ag or Pt and Ag from base metal bearing process solution, particularly from a hydrometallurgical sacrificial metal bearing solution containing Zn and/or Ni. In general, the method of the present invention can be used for recovery of precious metals, which are dissolvable in sulfuric acid, from sulfate media based solutions. In addition to Pt and Ag, especially Pd should be mentioned. Deposited precious metal(s) can be recovered from the electrode or the deposition containing electrode can be used as such.

Any metal having a low α-ray emission, the metal being any one of tin, silver, copper, zinc, or indium, wherein an emission of an α-ray after heating the metal at 100° C. in an atmosphere for six hours is 0.002 cph/cm.sup.2 or less. Any metal of tin, silver, copper, zinc and indium each including lead as an impurity is dissolved to prepare a hydrosulfate aqueous solution of the metal and lead sulfate is precipitated and removed in the solution. The lead sulfate is precipitated in the hydrosulfate aqueous solution by adding a lead nitrate aqueous solution including lead having an α-ray emission of 10 cph/cm.sup.2 or less to the hydrosulfate aqueous solution, from which the lead sulfate has been removed, and, at the same time, the solution is circulated while removing the lead sulfate to electrowinning the metal using the hydrosulfate aqueous solution as an electrolytic solution.

Any metal having a low α-ray emission, the metal being any one of tin, silver, copper, zinc, or indium, wherein an emission of an α-ray after heating the metal at 100° C. in an atmosphere for six hours is 0.002 cph/cm.sup.2 or less. Any metal of tin, silver, copper, zinc and indium each including lead as an impurity is dissolved to prepare a hydrosulfate aqueous solution of the metal and lead sulfate is precipitated and removed in the solution. The lead sulfate is precipitated in the hydrosulfate aqueous solution by adding a lead nitrate aqueous solution including lead having an α-ray emission of 10 cph/cm.sup.2 or less to the hydrosulfate aqueous solution, from which the lead sulfate has been removed, and, at the same time, the solution is circulated while removing the lead sulfate to electrowinning the metal using the hydrosulfate aqueous solution as an electrolytic solution.

A method for making a porous metal article of manufacture is provided. The method includes subjecting a saturated aqueous electrolytic solution wherein silver or copper is a donor in a container with two electrodes, where dendrite crystals of silver or copper or silver or copper nanowires are formed and collected. The collected dendrite crystals or nanowires are pressed and sintered, thereafter cooled to room temperature at room temperature and finally pressing the cooled geometric shape to form the porous silver metal article of manufacture. The collected dendrites crystals or nanowires also can be pressed in a carbon based mold or, alternatively, a non-carbon based mold and in vacuum, sintered, cooled to room temperature.