Provided is a material that can be used as a potassium secondary battery positive electrode active material (particularly a potassium ion secondary battery positive electrode active material), other than Prussian blue, by using a potassium compound and a potassium ion secondary battery positive electrode active material comprising the potassium compound, the potassium compound being represented by general formula (1):
K.sub.nA.sub.kBO.sub.m,
wherein A is a positive divalent element in groups 7 to 11 of the periodic table; B is positive tetravalent silicon, germanium, titanium or manganese, excluding a case in which A is manganese and B is titanium, and a case in which A is cobalt and B is silicon; n is 1.5 to 2.5; and m is 3.5 to 4.5.

A process of purifying acetic acid is provided. The process includes feeding a stream of acetic acid into a distillation column and distilling acetic acid in the presence of an oxidizing agent in the distillation column, to oxidize oxidizable impurities in the acetic acid, wherein the oxidizing agent is an oxidant capable of cleaving CC bonds. The process further includes removing a distilled acetic acid stream from the distillation column. Further processes for purifying acetic acid and systems for purifying acetic acid are also provided.

The present invention provides a solid-phase catalyst for decomposing hydrogen peroxide comprising a permanganate salt and a manganese (II) salt. The solid-phase catalyst stays a solid state in the form of nanoparticles at the time of hydrogen peroxide decomposition, and thus can be recovered for reuse and also has an excellent decomposition rate. In the method for producing a solid-phase catalyst for decomposing hydrogen peroxide according to the present invention, a solid-phase catalyst is produced from a solution containing a permanganate salt, a manganese (II) salt, and an organic acid, so that the produced solid-phase catalyst is precipitated as a solid component even after a catalytic reaction, and thus is reusable and environmentally friendly, and cost reduction can be achieved through the simplification of a catalyst production technique.

A process of purifying acetic acid is provided. The process includes feeding a feed stream comprising acetic acid into a bottom half of a distillation column and distilling the acetic acid in the presence of a homogeneous oxidizing agent in the distillation column, to oxidize oxidizable impurities in the acetic acid, wherein the homogeneous oxidizing agent is capable of cleaving CC bonds. The process further includes removing a distilled acetic acid stream from the distillation column. Further processes for purifying acetic acid and systems for purifying acetic acid are also provided.

Acoustically active articles having a composition including a nano-structured metal oxide are provided. The nano-structured metal oxide has the formula M1xM2yOz, where M1 is selected from the group consisting of alkali metals, alkaline earth metals, and combinations thereof, M2 is a transition metal or post-transition metal, and M2 has an atomic number no greater than 78. The articles can lower a resonant frequency of a cavity by no less than 50 Hz when the cavity is filled with the article and the resonant frequency is in a range from about 50 Hz to about 1500 Hz.

Positive electrode active material particle powder includes: lithium manganese oxide particle powder having Li and Mn as main components and a cubic spinel structure with an Fd-3m space group. The lithium manganese oxide particle powder is composed of secondary particles, which are aggregates of primary particles, an average particle diameter (D50) of the secondary particles being from 4 m to 20 m, and at least 80% of the primary particles exposed on surfaces of the secondary particles each have a polyhedral shape having at least one plane that is adjacent to two planes.

The disclosure provides a novel positive electrode active material for an aqueous potassium ion battery, and a novel potassium ion secondary battery. The positive electrode active material for an aqueous potassium ion battery is represented by the general formula Li.sub.xMn.sub.2O.sub.4, where 0<x<2. The aqueous potassium ion secondary battery comprises a positive electrode active material represented by the general formula Li.sub.xMn.sub.2O.sub.4 where 0<x<2, and an aqueous electrolyte solution, wherein the aqueous electrolyte solution has a pH of 7.0 to 13.0 and comprises an aqueous solvent and a potassium salt dissolved in the aqueous solvent. The potassium salt is preferably potassium pyrophosphate.

Positive electrode active material particle powder includes: lithium manganese oxide particle powder having Li and Mn as main components and a cubic spinel structure with an Fd-3m space group. The lithium manganese oxide particle powder is composed of secondary particles, which are aggregates of primary particles, an average particle diameter (D50 ) of the secondary particles being from 4 m to 20 m, and at least 80% of the primary particles exposed on surfaces of the secondary particles each have a polyhedral shape having at least one (110) plane that is adjacent to two (111) planes.

Provided are polycrystalline lithium manganese oxide particles represented by Chemical Formula 1 and a method of preparing the same:
Li.sub.(1+x)Mn.sub.(2xyf)Al.sub.yM.sub.fO.sub.(4z)<Chemical Formula 1> where M is any one selected from the group consisting of boron (B), cobalt (Co), vanadium (V), lanthanum (La), titanium (Ti), nickel (Ni), zirconium (Zr), yttrium (Y), and gallium (Ga), or two or more elements thereof, 0x0.2, 0<y0.2, 0<f0.2, and 0z0.2. According to an embodiment of the present invention, limitations, such as the Jahn-Teller distortion and the dissolution of Mn.sup.2+, may be addressed by structurally stabilizing the polycrystalline lithium manganese oxide particles. Thus, life characteristics and charge and discharge capacity characteristics of a secondary battery may be improved.

The present disclosure provides a production system and a production method of potassium manganate, belonging to the technical field of production of potassium manganate. The production system of potassium manganate comprises a hot air generating device, a production device and a circulating air pipeline. The hot air generating device is configured provide hot air in a manner of burning fuel gas. The production device is configured to absorb heat in the hot air generated by the hot air generating device. The circulating air pipeline is configured to introduce the hot air passing through the production device into the hot air generating device to adjust temperature of the hot air.