Abstract: The present invention provides a method for quantitative determination of oxidant which method is capable of accurately and rapidly performing quantitative determination of oxidant at low cost, and an apparatus for quantitative determination of oxidant used in the method. The method for quantitative determination of oxidant according to the present invention is a method for quantitative determination of oxidant performing quantitative determination of oxidant in a sample using a redox reaction, the method including: adding one kind of reducing agent to a sample solution containing one or a plurality of kinds of oxidants having different lifetimes; producing an absorbance curve by measuring a time change in absorbance of the post-color-change or post-coloring reducing agent; and performing the quantitative determination of the oxidant while identifying the oxidant in the sample solution based on the obtained absorbance curve.

Abstract: A liquid treatment method according to an aspect of the present disclosure comprises: starting application of a power between a pair of electrodes to generate plasma, which causes active species to be produced in a liquid; measuring the hydrogen ion concentration in the liquid while the plasma is generated; measuring a time elapsed after the starting the application of the power; and stopping the application of the power when a value calculated by (a) multiplying the hydrogen ion concentration by the elapsed time or (b) integrating the hydrogen ion concentration with respect to the elapsed time is larger than a first threshold.

Abstract: A method according to an aspect of the present disclosure includes filtering plasma-treated water containing hydrogen peroxide which has been produced by generation of plasma in or near water; and applying ultrasound to the plasma-treated water after the filtering.

Abstract: The present invention provides a method for quantitative determination of oxidant which method is capable of accurately and rapidly performing quantitative determination of oxidant at low cost, and an apparatus for quantitative determination of oxidant used in the method. The method for quantitative determination of oxidant according to the present invention is a method for quantitative determination of oxidant performing quantitative determination of oxidant in a sample using a redox reaction, the method including: adding one kind of reducing agent to a sample solution containing one or a plurality of kinds of oxidants having different lifetimes; producing an absorbance curve by measuring a time change in absorbance of the post-color-change or post-coloring reducing agent; and performing the quantitative determination of the oxidant while identifying the oxidant in the sample solution based on the obtained absorbance curve.

Abstract: A liquid treatment apparatus includes a dielectric tube through which water to be treated flows, a first electrode at least a part of which is disposed in the dielectric tube, a second electrode at least a part of which is disposed in the dielectric tube at a position upstream of the first electrode, a gas supplier operative to generate a bubble by supplying a gas into the water to be treated, and a power supply operative to apply a voltage between the first electrode and the second electrode in a state in which the bubble covers a conductor-exposed portion of the first electrode.

Abstract: The present disclosure provides a liquid treatment device, a liquid treatment method, and a plasma treatment liquid each capable of efficiently generating plasma and treating a liquid in a short time period. A liquid treatment device according to the present disclosure includes a first electrode, a second electrode disposed in a liquid to be treated, an insulator disposed around the first electrode with a space between the first electrode and the insulator, the insulator has an opening portion in a position in contact with the liquid to be treated, a power supply that applies voltage between the first electrode and the second electrode, and a supply device supplying a liquid to the space before the power source applies the voltage.

Abstract: A liquid treatment apparatus includes a dielectric tube through which a liquid flows, a first electrode, at least one end of which is disposed in the dielectric tube, a second electrode, at least one end of which is disposed in the dielectric tube, and a power supply for applying a voltage between the first electrode and the second electrode, wherein the dielectric tube has a protrusion projecting outwardly from an inside of the dielectric tube, an inner wall face of the protrusion facing the first electrode.

Abstract: A liquid treatment apparatus according to the present disclosure includes a dielectric tube that defines a channel through which water to be treated flows, the channel being split upstream of the dielectric tube into a first channel and a second channel, the first channel and the second channel being merged with each other downstream of the dielectric tube, a first electrode at least partially disposed within the first channel, a second electrode at least partially disposed within the first channel, a first gas-supply unit that supplies gas to form a gas bubble into water to be treated that flows through the first channel, and a first power-supply that applies a voltage between the first electrode and the second electrode.

Abstract: A liquid treatment unit includes: a treatment tank provided with an inlet and an outlet, the treatment tank having a shape that allows a portion of liquid to be retained; a controller that controls supply of liquid into the treatment tank and ejection of liquid from the treatment tank; and a plasma generator generates plasma in the liquid inside the treatment tank. The plasma generator generates plasma while the controller stops supply of liquid and ejection of liquid. After the liquid has been treated, the controller resumes the supply of liquid, and causes the liquid to be ejected from the treatment tank while allowing a portion of the treated liquid to be retained inside the treatment tank.

Abstract: A liquid treatment unit includes: an inlet for supplying liquid; a flow passage tube connected to the inlet, the flow passage tube defining a circulation flow passage along which the liquid supplied from the inlet circulates; a plasma generator generates plasma in the liquid in at least a partial area of the flow passage tube; a distributor, provided midway in the flow passage tube, for distributing a portion of liquid from the liquid flowing through the flow passage tube; and an outlet, connected to the distributor, for ejecting the portion of liquid from the flow passage tube.

Abstract: The present disclosure provides a liquid treatment device and a liquid treatment method each capable of efficiently generating plasma and treating a liquid in a short time period. A liquid treatment device according to the present disclosure includes a first electrode, a second electrode disposed in a liquid, an insulator disposed surrounding the first electrode through a space, the insulator having an opening portion at a position in contact with the liquid, and a power supply that applies an AC voltage or a pulse voltage between the first electrode and the second electrode.

Abstract: This disclosure of a liquid treatment device includes a first metal electrode having a part disposed in a reaction tank into which a water being treated is filled, a second metal electrode disposed in the reaction tank, an insulator having an opening portion disposed to surround the first metal electrode so that a closed space is formed. A bubble is generated from the closed space to the water being treated via the opening portion. The liquid treatment device also includes a gas supply device that supplies the space with a gas for generating the bubble, and a power supply that applies a voltage between the first metal electrode and the second metal electrode.