It is an object of the present disclosure to provide a method for inexpensively producing a high-performance barium sulfate powder which is obtained by using inexpensive barium sulfide as a raw material, has a high whiteness degree, and can suppress the generation of volatile components.

A method for producing a barium sulfate powder comprising a step of heat treating a raw barium sulfate powders obtained by using barium sulfide as a raw material at 600 to 1300° C., wherein a retention time X (minutes) at a heat treatment temperature of t ° C. is more than time expressed by the following general formula:

X (minutes)=A×10.sup.6×e.sup.(−0.015×t)

A is 8 or more, and an upper limit of X is 3000 minutes in the formula.

The present invention disclosed use of lactam as a solvent in the preparation of nanomaterials by precipitation method, sol-gel method or high temperature pyrolysis. These methods are able to recycle lactam solvent, which meet requirements of environmental protection.

A method of producing a product inorganic compound including: immersing a raw material inorganic compound having a volume of 10.sup.−13 m.sup.3 or more in an electrolyte aqueous solution or an electrolyte suspension; exchanging anions in the raw material inorganic compound with anions in the electrolyte aqueous solution or the electrolyte suspension; cations in the raw material inorganic compound are exchanged with cations in the electrolyte aqueous solution or the electrolyte suspension; or including a component (that excludes water, hydrogen, and oxygen) in the electrolyte aqueous solution or the electrolyte suspension not included in the raw material inorganic compound in the raw material inorganic compound; and obtaining a product inorganic compound having a volume of 10.sup.−13 m.sup.3 or more from the raw material inorganic compound.

A method of producing a product inorganic compound including: immersing a raw material inorganic compound having a volume of 10.sup.−13 m.sup.3 or more in an electrolyte aqueous solution or an electrolyte suspension; exchanging anions in the raw material inorganic compound with anions in the electrolyte aqueous solution or the electrolyte suspension; cations in the raw material inorganic compound are exchanged with cations in the electrolyte aqueous solution or the electrolyte suspension; or including a component (that excludes water, hydrogen, and oxygen) in the electrolyte aqueous solution or the electrolyte suspension not included in the raw material inorganic compound in the raw material inorganic compound; and obtaining a product inorganic compound having a volume of 10.sup.−13 m.sup.3 or more from the raw material inorganic compound.

A method of pretreatment and bromine recovery of PCB Incineration ash is disclosed that relates to the field of comprehensive recovery of valuable metals by full wet method, especially relates to a method of valuable metals and bromine recovery, precious metals enrichment in pretreatment process of PCB Incineration ash. The major steps includes alkali leaching, Cu extraction back-extraction, neutralization-precipitation to separate, Bromine evaporative crystallization, regeneration, acid pickling, Zn evaporative crystallization, removal of Zn and Cu. Compared with the traditional comprehensive recovery process of ash, the invention can separate bromine from ash and recover valuable metals such as copper, zinc and lead with the maximum extent, at the same time, the enrichment of silver and other precious metals is beneficial to the subsequent recovery of precious metals. It has high added recovery value and no tailless discharge.

An asbestos waste neutralization device, that includes an acid tank and a vat containing a diluted acid solution, in which waste containing asbestos is dipped, the diluted acid solution neutralizing the waste containing asbestos during a neutralization reaction. The device further includes a filtration unit to separate, at the end of the neutralization reaction, solid inert waste from a liquid phase of the acid solution, and a regeneration unit for the liquid phase of the acid solution, which adjusts the hydrogen potential of the liquid phase of the acid solution by adding concentrated acid contained in the acid tank. In addition, the device includes an attenuation sensor for regenerated liquid phase of the acid solution from the regeneration unit, and a selective precipitation unit for the regenerated liquid phase of the acid solution, depending on the degree of attenuation the attenuation sensor senses.

An asbestos waste neutralization device, that includes an acid tank and a vat containing a diluted acid solution, in which waste containing asbestos is dipped, the diluted acid solution neutralizing the waste containing asbestos during a neutralization reaction. The device further includes a filtration unit to separate, at the end of the neutralization reaction, solid inert waste from a liquid phase of the acid solution, and a regeneration unit for the liquid phase of the acid solution, which adjusts the hydrogen potential of the liquid phase of the acid solution by adding concentrated acid contained in the acid tank. In addition, the device includes an attenuation sensor for regenerated liquid phase of the acid solution from the regeneration unit, and a selective precipitation unit for the regenerated liquid phase of the acid solution, depending on the degree of attenuation the attenuation sensor senses.

A method of producing a product inorganic compound including: immersing a raw material inorganic compound having a volume of 10.sup.−13 m.sup.3 or more in an electrolyte aqueous solution or an electrolyte suspension; exchanging anions in the raw material inorganic compound with anions in the electrolyte aqueous solution or the electrolyte suspension; cations in the raw material inorganic compound are exchanged with cations in the electrolyte aqueous solution or the electrolyte suspension; or including a component (that excludes water, hydrogen, and oxygen) in the electrolyte aqueous solution or the electrolyte suspension not included in the raw material inorganic compound in the raw material inorganic compound; and obtaining a product inorganic compound having a volume of 10.sup.−13 m.sup.3 or more from the raw material inorganic compound.

A method of producing a product inorganic compound including: immersing a raw material inorganic compound having a volume of 10.sup.−13 m.sup.3 or more in an electrolyte aqueous solution or an electrolyte suspension; exchanging anions in the raw material inorganic compound with anions in the electrolyte aqueous solution or the electrolyte suspension; cations in the raw material inorganic compound are exchanged with cations in the electrolyte aqueous solution or the electrolyte suspension; or including a component (that excludes water, hydrogen, and oxygen) in the electrolyte aqueous solution or the electrolyte suspension not included in the raw material inorganic compound in the raw material inorganic compound; and obtaining a product inorganic compound having a volume of 10.sup.−13 m.sup.3 or more from the raw material inorganic compound.

Aqueous slurry which includes solid foreign matter and paper dust is pressed by means of a screw press, provided with a mesh having openings not less than 1.5 mm and not greater than 3 mm, to separate the aqueous slurry into the solid foreign matter and the paper dust, and liquid component passing through the mesh. Then, the liquid component is sieved by means of a sieve having openings not greater than 1 mm to separate from the liquid component the solid foreign matter and the paper dust.