Provided are a selective recovery method of vanadium and cesium from a waste sulfuric acid vanadium catalyst by a hydrometallurgical method including water leaching, solid-liquid separation, vanadium solvent extraction, vanadium selective stripping, and cesium alum production, and a high-quality vanadium aqueous solution and cesium alum produced thereby.

A method for determining an average oxidation state (AOS) of a redox flow battery system includes measuring a charge capacity for a low potential charging period starting from a discharged state of the redox flow battery system to a turning point of a charge voltage; and determining the AOS using the measured charge capacity and volumes of anolyte and catholyte of the redox flow battery system. Other methods can be used to determine the AOS for a redox flow battery system or use discharge voltage instead of charging voltage.

A method for determining an average oxidation state (AOS) of a redox flow battery system includes measuring a charge capacity for a low potential charging period starting from a discharged state of the redox flow battery system to a turning point of a charge voltage; and determining the AOS using the measured charge capacity and volumes of anolyte and catholyte of the redox flow battery system. Other methods can be used to determine the AOS for a redox flow battery system or use discharge voltage instead of charging voltage.

Disclosed are a core-shell structure type wave absorbing material and a preparation method therefor. The wave absorbing material has a core-shell structure with two-dimensional transition metal-chalcogen compound nanosheets as cores and hollow carbon spheres as shells. The preparation method includes: dissolving the hollow carbon spheres in a solvent, sequentially adding a transition metal source and a chalcogen source, taking a solvothermal reaction after dissolution through stirring, and then performing posttreatment to obtain the wave absorbing material. The present invention further discloses an application of the wave absorbing material in fields of military and civilian high-frequency electromagnetic compatibility and protection. The core-shell structure type wave absorbing material of the present invention has a density of 0.3 to 1.5 g/cm.sup.3, a maximum reflection loss value and an effective bandwidth of the material can be effectively improved in a frequency range of 2 to 40 GHz, and the core-shell structure type wave absorbing material is an electromagnetic compatibility and protection material capable of meeting requirements of civilian high-frequency electronic devices and military weapons and equipment such as airships and artillery shells.

Disclosed are a core-shell structure type wave absorbing material and a preparation method therefor. The wave absorbing material has a core-shell structure with two-dimensional transition metal-chalcogen compound nanosheets as cores and hollow carbon spheres as shells. The preparation method includes: dissolving the hollow carbon spheres in a solvent, sequentially adding a transition metal source and a chalcogen source, taking a solvothermal reaction after dissolution through stirring, and then performing posttreatment to obtain the wave absorbing material. The present invention further discloses an application of the wave absorbing material in fields of military and civilian high-frequency electromagnetic compatibility and protection. The core-shell structure type wave absorbing material of the present invention has a density of 0.3 to 1.5 g/cm.sup.3, a maximum reflection loss value and an effective bandwidth of the material can be effectively improved in a frequency range of 2 to 40 GHz, and the core-shell structure type wave absorbing material is an electromagnetic compatibility and protection material capable of meeting requirements of civilian high-frequency electronic devices and military weapons and equipment such as airships and artillery shells.

A combustion ash handling method of handling combustion ash discharged from a combustion furnace that combusts a petroleum-based fuel includes: separating the combustion ash into a heavy component and a light component by a dry-type separation technique; feeding the light component to the combustion furnace as a fuel; and recovering the heavy component. A metal such as vanadium is separated and extracted from the heavy component of the combustion ash.

A combustion ash handling method of handling combustion ash discharged from a combustion furnace that combusts a petroleum-based fuel includes: separating the combustion ash into a heavy component and a light component by a dry-type separation technique; feeding the light component to the combustion furnace as a fuel; and recovering the heavy component. A metal such as vanadium is separated and extracted from the heavy component of the combustion ash.

An electrode comprising a space group Pna2.sub.1 VOPO.sub.4 lattice, capable of electrochemical insertion and release of alkali metal ions, e.g., sodium ions. The VOPO.sub.4 lattice may be formed by solid phase synthesis of KVOPO.sub.4, milled with carbon particles to increase conductivity. A method of forming an electrode is provided, comprising milling a mixture of ammonium metavanadate, ammonium phosphate monobasic, and potassium carbonate; heating the milled mixture to a reaction temperature, and holding the reaction temperature until a solid phase synthesis of KVOPO.sub.4 occurs; milling the KVOPO.sub.4 together with conductive particles to form a conductive mixture of fine particles; and adding binder material to form a conductive cathode. A sodium ion battery is provided having a conductive NaVOPO.sub.4 cathode derived by replacement of potassium in KVOPO.sub.4, a sodium ion donor anode, and a sodium ion transport electrolyte. The VOPO.sub.4, preferably has a volume greater than 90 Å.sup.3 per VOPO.sub.4.

A hybrid photoactive heterojunction including a copper vanadate, Cu.sub.2V.sub.2O.sub.7 (CVO) and a zinc vanadate, Zn.sub.2V.sub.2O.sub.6 (ZVO). Particles of the ZVO are dispersed in particles of the CVO to form the hybrid photoactive heterojunction. The hybrid photoactive heterojunction in the form of a photoactive film includes a substrate which is at least partially coated with the hybrid photoactive heterojunction. A method of photodegrading a dye includes contacting the photoactive film and the dye in a solution and exposing the solution to light. A method of photoelectrochemically oxidizing water includes contacting the photoactive film with water in a solution and exposing the solution to light.

A hybrid photoactive heterojunction including a copper vanadate, Cu.sub.2V.sub.2O.sub.7 (CVO) and a zinc vanadate, Zn.sub.2V.sub.2O.sub.6 (ZVO). Particles of the ZVO are dispersed in particles of the CVO to form the hybrid photoactive heterojunction. The hybrid photoactive heterojunction in the form of a photoactive film includes a substrate which is at least partially coated with the hybrid photoactive heterojunction. A method of photodegrading a dye includes contacting the photoactive film and the dye in a solution and exposing the solution to light. A method of photoelectrochemically oxidizing water includes contacting the photoactive film with water in a solution and exposing the solution to light.