# US 2014/0151302 A1 · Method for treating hexavalent chromium-containing aqueous solution > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0151302 A1 - Document ID: US20140151302A1 - Status: Published application - Kind: A1 - Application number: 14/172,609 - Filed: 2014-02-04 - Published: 2014-06-05 - Earliest claimed: 2012-06-14 - Assignees: Panasonic Corporation - Applicants: Panasonic Corporation - Inventors: Yuko MARUO; Daisuke INO - Web page: https://patentgrep.com/patent/US20140151302A1 ## CPC - C02F 1/444: {by ultrafiltration or microfiltration} - B01D 61/147: {Microfiltration} - B01D 61/16: Feed pretreatment - B01D 63/0822: {Plate-and-frame devices} - B01J 21/063: {Titanium; Oxides or hydroxides thereof} - B01J 29/08: of the faujasite type, e.g. type X or Y - B01J 35/39: Photocatalytic properties - B01J 35/40: characterised by dimensions, e.g. grain size (in a colloidal state B01J35/23; crystallite size B01J35/77) - B01J 35/45: Nanoparticles - B01J 37/06: Washing {(B01J37/0009, B01J37/0018 take precedence)} - B01J 37/343: {of ultrasonic wave energy} - C02F 1/32: with ultraviolet light - C02F 1/70: by reduction {(C02F1/4676 takes precedence)} - C02F 1/725: {by catalytic oxidation} - B01D 2311/04: Specific process operations in the feed stream; Feed pretreatment - B01D 2311/12: Addition of chemical agents - B01D 2311/2619: UV-irradiation - B01D 2311/2638: Reduction - B01D 2315/06: Submerged-type; Immersion type - C02F 2001/007: {Processes including a sedimentation step} - C02F 2101/22: Chromium or chromium compounds, e.g. chromates - C02F 2305/10: Photocatalysts - Y02W 10/37: using solar energy - C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes) - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS - Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT ## Abstract Provided is a method for treating a hexavalent chromium-containing aqueous solution by water treatment employing a titanium dioxide photocatalyst that is excellent in both photocatalytic activity and solid-liquid separation performance. The method according to the present disclosure includes the steps of: adding catalyst particles to the aqueous solution; reducing hexavalent chromium by irradiating the aqueous solution with light having a wavelength of 200 nanometers or more and 400 nanometers or less while stirring the catalyst particles in the aqueous solution; and stopping the stirring and separating the catalyst particles from the aqueous solution by sedimentation. Each catalyst particle is composed only of a titanium dioxide particle and a zeolite particle, the titanium dioxide particle is adsorbed on the outer surface of the zeolite particle, the zeolite particle has a silica/alumina molar ratio of 10 or more, and the catalyst particles are contained in the aqueous solution at a concentration of 0.4 grams/liter or more and 16 grams/liter or less. ## Claims ### Claim 1 A method for treating a hexavalent chromium-containing aqueous solution, comprising: a step a of adding catalyst particles to the aqueous solution; a step b of reducing hexavalent chromium by irradiating the aqueous solution with light having a wavelength of 200 nanometers or more and 400 nanometers or less while stirring the catalyst particles in the aqueous solution; and a step c of stopping the stirring in the step b and separating the catalyst particles from the aqueous solution by sedimentation, wherein each catalyst particle is composed only of a titanium dioxide particle and a zeolite particle, the titanium dioxide particle is adsorbed on an outer surface of the zeolite particle, the zeolite particle has a silica/alumina molar ratio of 10 or more, and the catalyst particles are contained in the aqueous solution at a concentration of 0.4 grams/liter or more and 16 grams/liter or less. ### Claim 2 (depends on 1) The method according to claim 1, comprising a step d of adding again the catalyst particles separated by sedimentation in the step c to the aqueous solution after the step c, wherein the step b and the step c are performed again after the step d. ### Claim 3 (depends on 1) The method according to claim 1, wherein the catalyst particles are separated by sedimentation in a solid-liquid separation vessel including a filtration membrane element in the step c, the method further comprises a step e of producing treated water from the aqueous solution using the filtration membrane element, and the filtration membrane element used in the step e is composed of a plate-shaped frame and sheets of filter paper made of resin and attached to both faces of the frame, and is arranged parallel to a direction in which the catalyst particles are sedimented. ### Claim 4 (depends on 3) The method according to claim 3, comprising a step f of adding again the catalyst particles separated by sedimentation in the step c to the aqueous solution after the step c, wherein the step b, the step c and the step e are performed again after the step f. ### Claim 5 (depends on 1) The method according to claim 1, wherein the zeolite particle is a zeolite particle subjected to a process in which an alumina portion is dissolved by treatment with an acid aqueous solution to introduce an active site for direct adsorption of the titanium dioxide particle, and then the acid aqueous solution adhered to the surface of the zeolite particle is removed by washing with water.