# US 9,751,785 B2 · Photocatalytic reduction of oxo-anions > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,751,785 B2 - Document ID: US9751785B2 - Status: Granted - Kind: B2 - Application number: 14/509,722 - Filed: 2014-10-08 - Published: 2015-04-09 - Granted: 2017-09-05 - Earliest claimed: 2013-10-08 - Assignees: Arizona Board of Regents for and on behalf of Arizona State University - Applicants: Kyle Doudrick; Kiril D. Hristovski; Paul K. Westerhoff - Inventors: Kyle Doudrick; Kiril D. Hristovski; Paul K. Westerhoff - Web page: https://patentgrep.com/patent/US9751785B2 ## CPC - C02F 1/70: by reduction {(C02F1/4676 takes precedence)} - C02F 1/008: {Control or steering systems not provided for elsewhere in subclass C02F} - C02F 1/30: by irradiation - C02F 1/32: with ultraviolet light - C02F 1/444: {by ultrafiltration or microfiltration} - C02F 2101/163: {Nitrates} - C02F 2101/22: Chromium or chromium compounds, e.g. chromates - C02F 2209/003: Downstream control, i.e. outlet monitoring, e.g. to check the treating agents, such as halogens or ozone, leaving the process - C02F 2209/005: Processes using a programmable logic controller [PLC] - C02F 2209/02: Temperature - C02F 2209/06: pH - C02F 2209/15: N03-N - C02F 2209/22: O2 - C02F 2209/40: Liquid flow rate - 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) - Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT ## Abstract A water treatment system including: a flow regulation control system configured to combine oxo-anion-contaminated water with a reduction-promoting agent, a hole scavenger, or both; a reactor fluidically coupled to the flow regulation control system; a first set of system control probes configured to monitor the concentration of oxygen and oxo-anion in the contaminated water; a second set of system control probes configured to monitor concentration of the oxo-anion and reduction products of the oxo-anion in treated effluent from the reactor; and a controller configured to control the flow regulation control system, thereby controlling the flow rate of the contaminated water and the at least one of the reduction-promoting agent and the hole scavenger to the reactor based at least in part on the concentration of oxo-anion and the reduction products of the oxo-anion in the treated effluent. ## Claims ### Claim 1 A water treatment system comprising: a flow regulation control system configured to combine oxo-anion-contaminated water with at least one of a reduction-promoting agent and a hole scavenger; a reactor fluidically coupled to the flow regulation control system, the reactor comprising a photocatalyst, wherein the oxo-anion-contaminated water is treated in the reactor to yield a treated effluent; a first set of system control probes positioned upstream of the flow regulation control system and configured to monitor the concentration of oxygen and oxo-anion reduction products in the oxo-anion-contaminated water; a second set of system control probes positioned downstream of the reactor and configured to monitor concentration of the oxo-anion and oxo-anion reduction products in treated effluent from the reactor; and a controller configured to control the flow regulation control system, thereby controlling the flow rate of the oxo-anion-contaminated water and the at least one of the reduction-promoting agent and the hole scavenger to the reactor based at least in part on the concentration of oxo-anion and reduction productions of the oxo-anion in the treated effluent from the reactor. ### Claim 2 (depends on 1) The water treatment system of claim 1, further comprising a pretreatment unit fluidically coupled to and upstream of the flow regulation control system, wherein the pretreatment unit is configured to remove organic matter from the oxo-anion-contaminated water. ### Claim 3 (depends on 2) The water treatment system of claim 2, wherein the pretreatment unit is configured to remove silica, phosphate, sulfate, iron, arsenate, calcium, or a combination thereof from the oxo-anion-contaminated water. ### Claim 4 (depends on 1) The water treatment system of claim 1, wherein the second set of system control probes monitors at least one of pH and temperature in the treated effluent from the reactor. ### Claim 5 (depends on 1) The water treatment system of claim 1, wherein the flow regulation control system comprises valves, and the valves are controlled by the controller. ### Claim 6 (depends on 1) The water treatment system of claim 1, wherein the controller controls the residence time of the oxo-anion-contaminated water and at least one of the reduction-promoting agent and the hole scavenger in the flow regulation control system. ### Claim 7 (depends on 1) The water treatment system of claim 1, wherein the reactor comprises a light source. ### Claim 8 (depends on 7) The water treatment system of claim 7, wherein the light source is selected from the group consisting of a UV light source, a visible light source, a xenon lamp, and a mercury lamp. ### Claim 9 (depends on 7) The water treatment system of claim 7, wherein the controller controls the intensity of the light source. ### Claim 10 (depends on 1) The water treatment system of claim 1, wherein the photocatalyst is immobilized on a UV/visible light-conducting surface. ### Claim 11 (depends on 1) The water treatment system of claim 1, wherein the photocatalyst is suspended in the oxo-anion-contaminated water in the reactor. ### Claim 12 (depends on 1) The water treatment system of claim 1, further comprising a photocatalyst recovery system fluidically coupled to the reactor. ### Claim 13 (depends on 12) The water treatment system of claim 12, wherein the photocatalyst recovery system comprises a microfiltration unit or an ultrafiltration unit. ### Claim 14 (depends on 1) The water treatment system of claim 1, wherein the photocatalyst comprises a catalyst that, upon photon excitation, generates electrons and holes with redox potentials capable of reducing the oxo-anion and its products and oxidizing the hole scavenger, respectively. ### Claim 15 (depends on 1) The water treatment system of claim 1, wherein the oxo-anion is nitrate, and the photocatalyst catalyzes the reduction of nitrate to nitrogen gas and ammonium ions. ### Claim 16 (depends on 1) The water treatment system of claim 1, wherein the reduction-promoting agent reacts on the photocatalyst to limit recombination of photo-excited electrons. ### Claim 17 (depends on 1) The water treatment system of claim 1, wherein the reduction-promoting agent improves the interaction between the oxo-anion, its reduction products, or both with the photocatalyst. ### Claim 18 (depends on 1) The water treatment system of claim 1, wherein the hole scavenger provides an electron with a redox potential sufficient to fill a hole generated in the photocatalyst upon excitation. ### Claim 19 (depends on 17) The water treatment system of claim 17, wherein the hole scavenger is formic acid, sodium formate, or a combination thereof. ### Claim 20 (depends on 1) The water treatment system of claim 1, wherein the oxo-anion comprises nitrate, chromate, or a combination thereof. ### Claim 21 A method of removing oxo-anion from oxo-anion-contaminated water, the method comprising: providing a water treatment system comprising: a flow regulation control system configured to combine oxo-anion-contaminated water with at least one of a reduction-promoting agent and a hole scavenger; a reactor fluidically coupled to the flow regulation control system, the reactor comprising a photocatalyst; a first set of system control probes positioned upstream of the flow regulation control system and configured to monitor the concentration of oxygen and oxo-anion reduction products in the oxo-anion-contaminated water; a second set of system control probes positioned downstream of the reactor and configured to monitor concentration of the oxo-anion and oxo-anion reduction products in treated effluent from the reactor; and a controller configured to control the flow regulation control system, thereby controlling the flow rate of the oxo-anion-contaminated water and the at least one reduction-promoting agent and the hole scavenger to the reactor based at least in part on the concentration of oxo-anion and reduction products of the oxo-anion in the treated effluent from the reactor; flowing the oxo-anion contaminated water and at least one of the reduction-promoting agent and the hole scavenger in the water treatment system to yield a mixture; providing the mixture to the reactor; and photocatalytically reducing the oxo-anion in the mixture within the reactor to yield the treated effluent, wherein the flow rate of the oxo-anion-contaminated water and at least one of the reduction promoting agent and the hole scavenger is automatically controlled by the controller based at least in part on the concentration of oxo-anion and reduction products of the oxo-anion in the treated effluent. ### Claim 22 (depends on 21) The method of claim 21, further comprising homogenizing the mixture and removing oxidants from the mixture before providing the mixture to the reactor. ### Claim 23 (depends on 21) The method of claim 21, wherein the oxo-anion is nitrate, and photocatalytically reducing the nitrate in the nitrate-contaminated water yields nitrogen gas and ammonia. ### Claim 24 (depends on 23) The method of claim 23, wherein an intensity of light in the reactor during the photocatalytic reduction is automatically controlled based at least in part on the concentration of oxo-anion and reduction products of the oxo-anion in the treated effluent. ### Claim 25 (depends on 21) The method of claim 21, wherein the oxo-anion comprises nitrate, chromate, or a combination thereof.