A copper integrated electrode with a convertible oxidation state, a preparation method and an application method are provided. The preparation process is based on an electrochemically induced self-growth method. Copper foam is used as a precursor, soaked in a graphene oxide solution, dried, calcined at high temperature and annealed, and then treated with an alkali solution to obtain the copper integrated electrode with the convertible oxidation state. The working electrode prepared by the nano-catalytic material of the present invention has good denitrification performance in the environmental field, which can achieve nearly 100% nitrate removal rate, nearly 100% nitrogen selectivity and long-term stability. These properties are due to the prepared working electrode having an oxidizable copper (I, II/0, I), oxygen vacancy (O) and a one-dimensional nanowire structure. The structure can regulate the adsorption and reduction of intermediate products, resulting in nearly 100% nitrate removal rate and nearly 100% nitrogen selectivity.

An electrochemical system and process are provided to convert an amount of chalcopyrite (CuFeS.sub.2) to a product including copper ions. In an electrochemical reactor, a potential is applied across an anode and a cathode to convert the chalcopyrite to an intermediate, chalcocite (Cu.sub.2S). The anode is covered to prevent contact with the intermediate, thus limiting subsequent conversion of the intermediate to covellite (CuS) in favor of conversion to a material more suited to chemical oxidation, cuprite (Cu.sub.2O). For example, the anode can be covered with one or more layers of filter paper. Upon application of an oxidizing agent, the cuprite is oxidized to produce a product including copper ions. The cathode and covered anode allow for efficient and inexpensive processing. The cost of this technique is comparable to industry standards, and moreover, has a much smaller environmental footprint than heat-based copper extraction.

An electrochemical system and process are provided to convert an amount of chalcopyrite (CuFeS.sub.2) to a product including copper ions. In an electrochemical reactor, a potential is applied across an anode and a cathode to convert the chalcopyrite to an intermediate, chalcocite (Cu.sub.2S). The anode is covered to prevent contact with the intermediate, thus limiting subsequent conversion of the intermediate to covellite (CuS) in favor of conversion to a material more suited to chemical oxidation, cuprite (Cu.sub.2O). For example, the anode can be covered with one or more layers of filter paper. Upon application of an oxidizing agent, the cuprite is oxidized to produce a product including copper ions. The cathode and covered anode allow for efficient and inexpensive processing. The cost of this technique is comparable to industry standards, and moreover, has a much smaller environmental footprint than heat-based copper extraction.

Methods and systems for electrolyte regeneration are provided, which regenerate a spent alkaline electrolyte (SE) comprising dissolved aluminum hydrates from an aluminum-air battery, by electrolysis, to precipitate aluminum tri-hydroxide (ATH) and form regenerated alkaline electrolyte, and adding a same-cation salt to an anolyte used in the electrolysis to supplant a corresponding electrolyte cation. The regeneration may be carried out continuously and further comprise mixing the SE and the same-cation salt in a salt tank configured to deliver the anolyte, removing the regenerated alkaline electrolyte from a catholyte tank configured to deliver the catholyte, and filtering the ATH from a solution delivered from the salt tank to the anolyte. Optionally, the salt may be a buffering salt, and in some cases chemical reactions may be used to enhance the regeneration by electrolysis.

The present invention provides a high-concentration tin sulfonate aqueous solution, in which a divalent tin ion (Sn.sup.2+) concentration is 360 g/L to 420 g/L, a tetravalent tin ion (Sn.sup.4+) concentration is 10 g/L or less, a free methanesulfonic acid concentration is 40 g/L or less, a Hazen unit color number (APHA) is 240 or less, and a turbidity is 25 FTU or less. This aqueous solution is produced such that stannous oxide powder whose temperature is adjusted to a temperature of 10° C. or lower is added to an aqueous methanesulfonic acid solution having a concentration of 60% by mass to 90% by mass when the aqueous solution circulates in a state of being maintained at the temperature of 10° C. or lower, and the stannous oxide powder is dissolved.

The present invention provides a high-concentration tin sulfonate aqueous solution, in which a divalent tin ion (Sn.sup.2+) concentration is 360 g/L to 420 g/L, a tetravalent tin ion (Sn.sup.4+) concentration is 10 g/L or less, a free methanesulfonic acid concentration is 40 g/L or less, a Hazen unit color number (APHA) is 240 or less, and a turbidity is 25 FTU or less. This aqueous solution is produced such that stannous oxide powder whose temperature is adjusted to a temperature of 10° C. or lower is added to an aqueous methanesulfonic acid solution having a concentration of 60% by mass to 90% by mass when the aqueous solution circulates in a state of being maintained at the temperature of 10° C. or lower, and the stannous oxide powder is dissolved.

A system for electrohydromodulation of wastewater. In an embodiment, the system comprises an anode in contact with at least one anodic chamber and a cathode in contact with a cathodic chamber. Each anodic chamber and the cathodic chamber are configured to receive a flow of wastewater. A first multivalent cation exchange membrane, between each anodic chamber and the cathodic chamber, allows multivalent cations to pass therethrough while preventing monovalent ions to pass therethrough. A power source is electrically coupled to each anode and the cathode, and is configured to apply a voltage across wastewater in the anodic chamber and the cathodic chamber, to thereby cause multivalent cations in the wastewater to pass through the multivalent cation exchange membrane.

A copper-palladium-loaded mesoporous silicon carbide-based catalyst, a preparation method, and an application thereof are provided. First, a mesoporous silicon carbide material is prepared by using mesoporous silica as a hard template; subsequently, the mesoporous silicon carbide material is mixed with a copper-palladium precursor mixed solution, and dried after the solvent is completely volatilized. The dried powder is successively subjected to calcination with N.sub.2 and reduction with H.sub.2 to finally obtain the copper-palladium-loaded mesoporous silicon carbide-based catalyst. The catalyst is made into an electrode, and the nitrate in water body is catalytically reduced by electrochemical method. The preparation method of the catalyst of the present invention is simple. The catalyst can realize high-efficiency catalytic denitrification at a low metal loading amount, with high selectivity of nitrogen. Moreover, the catalyst has the advantages of high activity, good stability, wide application range and low cost.

A copper-palladium-loaded mesoporous silicon carbide-based catalyst, a preparation method, and an application thereof are provided. First, a mesoporous silicon carbide material is prepared by using mesoporous silica as a hard template; subsequently, the mesoporous silicon carbide material is mixed with a copper-palladium precursor mixed solution, and dried after the solvent is completely volatilized. The dried powder is successively subjected to calcination with N.sub.2 and reduction with H.sub.2 to finally obtain the copper-palladium-loaded mesoporous silicon carbide-based catalyst. The catalyst is made into an electrode, and the nitrate in water body is catalytically reduced by electrochemical method. The preparation method of the catalyst of the present invention is simple. The catalyst can realize high-efficiency catalytic denitrification at a low metal loading amount, with high selectivity of nitrogen. Moreover, the catalyst has the advantages of high activity, good stability, wide application range and low cost.

An ammonia manufacturing apparatus includes: an electrochemical reaction unit including a first electrolytic bath for accommodating a first electrolytic solution, an oxidation electrode disposed in the first electrolytic bath, a second electrolytic bath for accommodating a second electrolytic solution containing nitrogen, an ammonia producing catalyst, and a reducing agent, a reduction electrode disposed in the second electrolytic bath, and a diaphragm, and configured to reduce nitrogen by the ammonia producing catalyst and the reducing agent in the second electrolytic bath to produce ammonia, and reduce the reducing agent oxidized due to the production of ammonia, at the reduction electrode by connecting the oxidation electrode and the reduction electrode to a power supply; a nitrogen supply unit including a nitrogen supply part for dissolving nitrogen in the second electrolytic solution; and an ammonia separation unit including a separation part configured to separate ammonia from the second electrolytic solution.