Abstract: Provided is a catalytic activity recovery method of a manganese oxide catalyst, an air-cleaning device using the same, air-cleaning system including the air-cleaning device, and an operation method of air-cleaning device by using the manganese oxide catalyst. The catalytic activity recovery method of a manganese oxide catalyst includes recovering the initial activity of a manganese Ni oxide catalyst by heating a manganese oxide catalyst which has been used to decompose ozone and of which activity is thus reduced by 10% or more compared to the initial ozone decomposition efficiency thereof, at the temperature of 80° C. to 250° C.

Abstract: Provided are an air-cleaning device and method for reducing harmful gas including ethylene and harmful microorganisms, and an air-cleaning system including the air-cleaning device.

Abstract: A reverse electrodialysis device using a precipitation reaction, according to one embodiment of the present invention, comprises a first cell stack alternately forming solid salt chambers and precipitation chambers through cation-exchange membranes and anion-exchange membranes which are alternately provided, and a first water-soluble solid salt and a second water-soluble solid salt which are filled in the solid salt chambers, wherein the first water-soluble solid salt and the second water-soluble solid salt are alternately filled in the solid salt chambers, and can react with each other so as to generate a precipitate in neighboring precipitation chambers when water is supplied.

Abstract: A reverse electrodialysis device using a precipitation reaction, according to one embodiment of the present invention, comprises a first cell stack alternately forming solid salt chambers and precipitation chambers through cation-exchange membranes and anion-exchange membranes which are alternately provided, and a first water-soluble solid salt and a second water-soluble solid salt which are filled in the solid salt chambers, wherein the first water-soluble solid salt and the second water-soluble solid salt are alternately filled in the solid salt chambers, and can react with each other so as to generate a precipitate in neighboring precipitation chambers when water is supplied.

Abstract: A reverse electrodialysis device using a precipitation reaction, according to one embodiment of the present invention, comprises a first cell stack alternately forming solid salt chambers and precipitation chambers through cation-exchange membranes and anion-exchange membranes which are alternately provided, and a first water-soluble solid salt and a second water-soluble solid salt which are filled in the solid salt chambers, wherein the first water-soluble solid salt and the second water-soluble solid salt are alternately filled in the solid salt chambers, and can react with each other so as to generate a precipitate in neighboring precipitation chambers when water is supplied.