Disclosed herein are methods and systems for treating a waste substance containing perfluoro- and polyfluoroalkyl substances (PFAS). The method includes combining the PFAS with a first amendment in a reactor to create a combination, heating and pressurizing the combination to hydrothermal conditions, and holding the combination at hydrothermal conditions for a holding time sufficient to at least partially mineralize the PFAS to create a treated combination.

Provided is a hexavalent chromium treatment agent capable of penetrating inside of a leather and capable of reducing not only hexavalent chromium present in the vicinity of the surface of the leather but also hexavalent chromium present inside the leather into trivalent chromium. The hexavalent chromium treatment agent of the present invention comprises a hexavalent chromium-reducing compound capable of reducing hexavalent chromium into trivalent chromium, a nonionic surfactant, and an aqueous solvent. The hexavalent chromium-reducing compound preferably comprises an organic compound (A) that has a specific structure capable of acting to reduce hexavalent chromium into trivalent chromium, that has a hydroxyphenyl group, and that has no aldehyde groups and no carboxyl groups.

Provided is a hexavalent chromium treatment agent capable of penetrating inside of a leather and capable of reducing not only hexavalent chromium present in the vicinity of the surface of the leather but also hexavalent chromium present inside the leather into trivalent chromium. The hexavalent chromium treatment agent of the present invention comprises a hexavalent chromium-reducing compound capable of reducing hexavalent chromium into trivalent chromium, a nonionic surfactant, and an aqueous solvent. The hexavalent chromium-reducing compound preferably comprises an organic compound (A) that has a specific structure capable of acting to reduce hexavalent chromium into trivalent chromium, that has a hydroxyphenyl group, and that has no aldehyde groups and no carboxyl groups.

A method of treating, stabilizing, precipitating, or otherwise removing heavy metal ions contained in a contaminated media, which method includes: providing a sodium-iron-sulfide mineral or crystalline phase, either alone or in combination with a pH adjusting substance; contacting said contaminated media containing heavy metal ions with the sodium-iron-sulfide mineral or crystalline phase, either alone or in combination with a pH adjusting substance; and allowing the contaminated media containing the heavy metal ions to react with said sodium-iron-sulfide mineral or crystalline phase, either alone or in combination with a pH adjusting substance, such that the contaminated media containing heavy metal ions form single or mixed metal-sulfide precipitates or co-precipitates.

A method of treating, stabilizing, precipitating, or otherwise removing heavy metal ions contained in a contaminated media, which method includes: providing a sodium-iron-sulfide mineral or crystalline phase, either alone or in combination with a pH adjusting substance; contacting said contaminated media containing heavy metal ions with the sodium-iron-sulfide mineral or crystalline phase, either alone or in combination with a pH adjusting substance; and allowing the contaminated media containing the heavy metal ions to react with said sodium-iron-sulfide mineral or crystalline phase, either alone or in combination with a pH adjusting substance, such that the contaminated media containing heavy metal ions form single or mixed metal-sulfide precipitates or co-precipitates.

An immobilized enzyme electrode includes: an electrode; a redox enzyme that oxidizes or reduces a target molecule; and an electron carrier that performs electron transport between the electrode and the redox enzyme. The electron carrier is immobilized on the electrode via a first linker that is in a form of a chain, and the redox enzyme is immobilized on the electrode via a second linker that is longer than the first linker, the second linker being in a form of a chain.

An immobilized enzyme electrode includes: an electrode; a redox enzyme that oxidizes or reduces a target molecule; and an electron carrier that performs electron transport between the electrode and the redox enzyme. The electron carrier is immobilized on the electrode via a first linker that is in a form of a chain, and the redox enzyme is immobilized on the electrode via a second linker that is longer than the first linker, the second linker being in a form of a chain.

An object of the invention is to provide a heat-resistant hexavalent chromium removal agent, which is capable of remaining in a leather or leather article for a long period of time and stably detoxifying hexavalent chromium over the long term even when a leather or leather article contains hexavalent chromium, and a leather or leather article, in which the hexavalent chromium content is less than 3 ppm. The leather or leather article of the present invention contains at least: an organic compound (A) having a structure shown in chemical formula (1) and hydroxyphenyl but not aldehyde and carboxyl, which organic compound has a property to reduce hexavalent chromium to trivalent chromium; and trivalent chromium, and the hexavalent chromium content determined in accordance with ISO 17075: 2008-02 is less than 3 ppm.

An object of the invention is to provide a heat-resistant hexavalent chromium removal agent, which is capable of remaining in a leather or leather article for a long period of time and stably detoxifying hexavalent chromium over the long term even when a leather or leather article contains hexavalent chromium, and a leather or leather article, in which the hexavalent chromium content is less than 3 ppm. The leather or leather article of the present invention contains at least: an organic compound (A) having a structure shown in chemical formula (1) and hydroxyphenyl but not aldehyde and carboxyl, which organic compound has a property to reduce hexavalent chromium to trivalent chromium; and trivalent chromium, and the hexavalent chromium content determined in accordance with ISO 17075: 2008-02 is less than 3 ppm.

The present disclosure relates to use of rhamnolipid coated nanoparticles of zero valent iron (NZVI), either in its bare form or functionalized with other materials (M) such as trace amounts of a palladium catalyst, for transforming chlorinated solvent pollutants by targeting the non-aqueous phase, which contains said chlorinated solvent pollutants. The method may be useful as water treatment technology for restoration of groundwater resources contaminated with toxic, chlorinated solvent pollutants as well as in the treatment of industrial waste of chlorinated solvents in reactor systems.