Highly enhanced photocatalytic reduction of Cr(VI) on AgI/TiO2 under visible light irradiation: Influence of calcination temperature

[Display omitted] •β-AgI riched AgI/TiO2 was obtained after simple heat pretreatment at 350°C.•Greatly enhanced visible light response was observed on AgI/TiO2-350.•AgI/TiO2-350 exhibited superior photocatalytic activity and stability.•5 times rate constant for Cr(VI) reduction was achieved.•More ef...

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Veröffentlicht in:Journal of hazardous materials 2016-04, Vol.307, p.213-220
Hauptverfasser: Wang, Qi, Shi, Xiaodong, Xu, Jianjia, Crittenden, John C., Liu, Enqin, Zhang, Yi, Cong, Yanqing
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container_start_page 213
container_title Journal of hazardous materials
container_volume 307
creator Wang, Qi
Shi, Xiaodong
Xu, Jianjia
Crittenden, John C.
Liu, Enqin
Zhang, Yi
Cong, Yanqing
description [Display omitted] •β-AgI riched AgI/TiO2 was obtained after simple heat pretreatment at 350°C.•Greatly enhanced visible light response was observed on AgI/TiO2-350.•AgI/TiO2-350 exhibited superior photocatalytic activity and stability.•5 times rate constant for Cr(VI) reduction was achieved.•More efficient separation and easier transfer of e−–h+ pairs were facilitated. AgI/TiO2 was prepared using a dissolution-precipitation method, followed by calcination at different temperatures (100–700°C). The as-prepared AgI/TiO2 powders were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV–Vis-DRS) and electrochemical impedance spectroscopy (EIS). The results revealed that calcination temperature significantly impacted the visible light absorption of AgI/TiO2 along with a shift from metastable γ-AgI to relatively stable β-AgI. We found that highest photocatalytic reduction rate of Cr(VI) and β-AgI content were obtained for a calcination temperature of 350°C. Furthermore, the pseudo-first order rate constant was five times that for a photocatalyst calcined at 100°C. The dramatically enhanced reduction rate of Cr(VI) was attributed to enhanced visible light absorption and greatly reduced charge transfer resistance, which eventually facilitates more efficient separation and easier transfer of photogenerated electron–hole pairs to the catalyst surface. Other experimental conditions were also carefully investigated and optimized with initial AgI loading percentage (5%), catalyst dosage (1.0g/L), coexisting organics (1.0mmol/L EDTA) and pH (1–2). The optimal AgI/TiO2 exhibited good stability with little change in activity after 5 cycles.
doi_str_mv 10.1016/j.jhazmat.2015.12.050
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AgI/TiO2 was prepared using a dissolution-precipitation method, followed by calcination at different temperatures (100–700°C). The as-prepared AgI/TiO2 powders were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV–Vis-DRS) and electrochemical impedance spectroscopy (EIS). The results revealed that calcination temperature significantly impacted the visible light absorption of AgI/TiO2 along with a shift from metastable γ-AgI to relatively stable β-AgI. We found that highest photocatalytic reduction rate of Cr(VI) and β-AgI content were obtained for a calcination temperature of 350°C. Furthermore, the pseudo-first order rate constant was five times that for a photocatalyst calcined at 100°C. The dramatically enhanced reduction rate of Cr(VI) was attributed to enhanced visible light absorption and greatly reduced charge transfer resistance, which eventually facilitates more efficient separation and easier transfer of photogenerated electron–hole pairs to the catalyst surface. Other experimental conditions were also carefully investigated and optimized with initial AgI loading percentage (5%), catalyst dosage (1.0g/L), coexisting organics (1.0mmol/L EDTA) and pH (1–2). The optimal AgI/TiO2 exhibited good stability with little change in activity after 5 cycles.</description><identifier>ISSN: 0304-3894</identifier><identifier>EISSN: 1873-3336</identifier><identifier>DOI: 10.1016/j.jhazmat.2015.12.050</identifier><identifier>PMID: 26785212</identifier><language>eng</language><publisher>Netherlands: Elsevier B.V</publisher><subject>AgI/TiO2 ; Calcination ; Catalysts ; Cr(VI) reduction ; Electrochemical impedance spectroscopy ; Heat pretreatment ; Light absorption ; Photocatalysis ; Reduction ; Titanium dioxide ; Visible light ; X-rays</subject><ispartof>Journal of hazardous materials, 2016-04, Vol.307, p.213-220</ispartof><rights>2015 Elsevier B.V.</rights><rights>Copyright © 2015 Elsevier B.V. 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AgI/TiO2 was prepared using a dissolution-precipitation method, followed by calcination at different temperatures (100–700°C). The as-prepared AgI/TiO2 powders were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV–Vis-DRS) and electrochemical impedance spectroscopy (EIS). The results revealed that calcination temperature significantly impacted the visible light absorption of AgI/TiO2 along with a shift from metastable γ-AgI to relatively stable β-AgI. We found that highest photocatalytic reduction rate of Cr(VI) and β-AgI content were obtained for a calcination temperature of 350°C. Furthermore, the pseudo-first order rate constant was five times that for a photocatalyst calcined at 100°C. The dramatically enhanced reduction rate of Cr(VI) was attributed to enhanced visible light absorption and greatly reduced charge transfer resistance, which eventually facilitates more efficient separation and easier transfer of photogenerated electron–hole pairs to the catalyst surface. Other experimental conditions were also carefully investigated and optimized with initial AgI loading percentage (5%), catalyst dosage (1.0g/L), coexisting organics (1.0mmol/L EDTA) and pH (1–2). The optimal AgI/TiO2 exhibited good stability with little change in activity after 5 cycles.</description><subject>AgI/TiO2</subject><subject>Calcination</subject><subject>Catalysts</subject><subject>Cr(VI) reduction</subject><subject>Electrochemical impedance spectroscopy</subject><subject>Heat pretreatment</subject><subject>Light absorption</subject><subject>Photocatalysis</subject><subject>Reduction</subject><subject>Titanium dioxide</subject><subject>Visible light</subject><subject>X-rays</subject><issn>0304-3894</issn><issn>1873-3336</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2016</creationdate><recordtype>article</recordtype><recordid>eNqNkUtv1DAUhS0EokPhJ4C8LIukfsVO2KBqVOhIlboZsbUc-6bjUR6D7VQa1vxwnM7AtqyurPudc-VzEPpISUkJldf7cr8zvwaTSkZoVVJWkoq8QitaK15wzuVrtCKciILXjbhA72LcE0KoqsRbdMGkqitG2Qr9vvOPu_6IYdyZ0YLDh92UJmuS6Y_JWxzAzTb5acRTh9fh6sfmM86Pm8fN9dY_MDyPDgJ-8tG3PeA-myXsQzDOm0X1BW_Grp8hWy8G1vTWj88bnGA4QDBpDvAevelMH-HDeV6i7bfb7fquuH_4vlnf3BdWyDoVtKlJBcCIEVLUbf6jYNJ2TnHbCgmSKtuAsWAFYdwRZZrOEMKahlHVuo5foquT7SFMP2eISQ8-Wuh7M8I0R01V9s_RUfofqOI1q-qMv4zKRtKmUSSj1Qm1YYoxQKcPwQ8mHDUlemlV7_W5Vb20qinTudWs-3Q-MbcDuH-qvzVm4OsJgJzek4ego_VL6M4HsEm7yb9w4g9d3rZI</recordid><startdate>20160415</startdate><enddate>20160415</enddate><creator>Wang, Qi</creator><creator>Shi, Xiaodong</creator><creator>Xu, Jianjia</creator><creator>Crittenden, John C.</creator><creator>Liu, Enqin</creator><creator>Zhang, Yi</creator><creator>Cong, Yanqing</creator><general>Elsevier B.V</general><scope>NPM</scope><scope>AAYXX</scope><scope>CITATION</scope><scope>7X8</scope><scope>7ST</scope><scope>7U7</scope><scope>C1K</scope><scope>SOI</scope><scope>7QQ</scope><scope>7SR</scope><scope>7SU</scope><scope>8BQ</scope><scope>8FD</scope><scope>FR3</scope><scope>JG9</scope><scope>KR7</scope></search><sort><creationdate>20160415</creationdate><title>Highly enhanced photocatalytic reduction of Cr(VI) on AgI/TiO2 under visible light irradiation: Influence of calcination temperature</title><author>Wang, Qi ; 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The dramatically enhanced reduction rate of Cr(VI) was attributed to enhanced visible light absorption and greatly reduced charge transfer resistance, which eventually facilitates more efficient separation and easier transfer of photogenerated electron–hole pairs to the catalyst surface. Other experimental conditions were also carefully investigated and optimized with initial AgI loading percentage (5%), catalyst dosage (1.0g/L), coexisting organics (1.0mmol/L EDTA) and pH (1–2). The optimal AgI/TiO2 exhibited good stability with little change in activity after 5 cycles.</abstract><cop>Netherlands</cop><pub>Elsevier B.V</pub><pmid>26785212</pmid><doi>10.1016/j.jhazmat.2015.12.050</doi><tpages>8</tpages></addata></record>
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subjects AgI/TiO2
Calcination
Catalysts
Cr(VI) reduction
Electrochemical impedance spectroscopy
Heat pretreatment
Light absorption
Photocatalysis
Reduction
Titanium dioxide
Visible light
X-rays
title Highly enhanced photocatalytic reduction of Cr(VI) on AgI/TiO2 under visible light irradiation: Influence of calcination temperature
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