高指数晶面TiO_2对铬的吸附及光催化去除
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摘要
由工业生产引起的铬污染是环境领域面临的一大挑战.二氧化钛(TiO_2)材料因其吸附催化的双重作用在铬的去除方面具有潜在应用前景.利用溶剂热法合成高指数晶面TiO_2{201},对其进行SEM、TEM、XRD及XPS表征,并用于Cr(Ⅲ/Ⅵ)的吸附及Cr(Ⅵ)的光催化还原,以达到从水体中去除铬的目的.所合成的TiO_2{201}为锐钛矿相,呈蒲公英状的层级结构. Langmuir吸附等温线结果表明,TiO_2{201}对Cr(Ⅲ)和Cr(Ⅵ)的最大吸附量分别为22. 7 mg·g-1和13. 2 mg·g-1,Freundlich模型拟合结果表明TiO_2{201}对Cr(Ⅲ)和Cr(Ⅵ)的吸附均易于进行,其1/n均小于0. 5.在紫外光照条件下,TiO_2{201}作为光催化剂可将毒性较强且吸附去除效果较差的Cr(Ⅵ)还原成Cr(Ⅲ),并以Cr(OH)3及Cr2O3的形式沉淀在TiO_2表面,XPS表征结果进一步证实了表面沉淀的存在.为探明TiO_2{201}光催化还原Cr(Ⅵ)的机制,分别研究光生空穴淬灭剂(EDTA-2Na)和光生电子淬灭剂(KBr O3)对Cr(Ⅵ)还原效率的影响,证明Cr(Ⅵ)的还原是由光生电子引起.
Chromium( Cr) contamination caused by industrial manufacturing poses a severe challenge in the environment. Titanium dioxide( TiO_2) has potential application in Cr removal due to its adsorption and photocatalytic performance. High-index TiO_2 with exposed { 201} facet was synthesized using the solvothermal method and characterized by SEM,TEM,XRD,and XPS. The adsorption of Cr( Ⅲ/Ⅵ) and photocatalytic reduction of Cr( Ⅵ) on TiO_2{ 201} was examined for the removal from water. The synthesized TiO_2{ 201} was constructed by a dandelion-like hierarchical structure. The adsorption isotherms of Cr( Ⅲ) and Cr( Ⅵ) on TiO_2{ 201}conformed to the Langmuir model,with maximum adsorption capacities of 22. 7 mg·g-1 and 13. 2 mg·g-1,respectively. The best fitted results from the Freundlich model show that the adsorption of Cr( Ⅲ) and Cr( Ⅵ) on TiO_2{ 201} were favorable with the parameter of 1/n less than 0. 5. The results of photocatalytic reduction show that TiO_2{ 201} can reduce Cr( Ⅵ) to Cr( Ⅲ) under UV irradiation,and Cr( Ⅲ) was further precipitated on the surface of TiO_2 in the form of Cr( OH)3 and Cr2 O3,which was evidenced by XPS characterization. To explore the mechanism of photocatalytic reduction of Cr( Ⅵ),the effect of scavengers for photogenerated holes( EDTA-2 Na) and electrons( KBr O3) on Cr( Ⅵ) reduction was studied,and the results suggested that photogenerated electrons were the main reductant.
Chromium( Cr) contamination caused by industrial manufacturing poses a severe challenge in the environment. Titanium dioxide( TiO_2) has potential application in Cr removal due to its adsorption and photocatalytic performance. High-index TiO_2 with exposed { 201} facet was synthesized using the solvothermal method and characterized by SEM,TEM,XRD,and XPS. The adsorption of Cr( Ⅲ/Ⅵ) and photocatalytic reduction of Cr( Ⅵ) on TiO_2{ 201} was examined for the removal from water. The synthesized TiO_2{ 201} was constructed by a dandelion-like hierarchical structure. The adsorption isotherms of Cr( Ⅲ) and Cr( Ⅵ) on TiO_2{ 201}conformed to the Langmuir model,with maximum adsorption capacities of 22. 7 mg·g-1 and 13. 2 mg·g-1,respectively. The best fitted results from the Freundlich model show that the adsorption of Cr( Ⅲ) and Cr( Ⅵ) on TiO_2{ 201} were favorable with the parameter of 1/n less than 0. 5. The results of photocatalytic reduction show that TiO_2{ 201} can reduce Cr( Ⅵ) to Cr( Ⅲ) under UV irradiation,and Cr( Ⅲ) was further precipitated on the surface of TiO_2 in the form of Cr( OH)3 and Cr2 O3,which was evidenced by XPS characterization. To explore the mechanism of photocatalytic reduction of Cr( Ⅵ),the effect of scavengers for photogenerated holes( EDTA-2 Na) and electrons( KBr O3) on Cr( Ⅵ) reduction was studied,and the results suggested that photogenerated electrons were the main reductant.
引文
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[21] Wang L,Zhang C B,Gao F,et al. Algae decorated Ti O2/Ag hybrid nanofiber membrane with enhanced photocatalytic activity for Cr(Ⅵ)removal under visible light[J]. Chemical Engineering Journal,2017,314:622-630.
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[23] Yan L,Du J J,Jing C Y. How Ti O2facets determine arsenic adsorption and photooxidation:spectroscopic and DFT studies[J]. Catalysis Science&Technology,2016,6(7):2419-2426.
[24] Yan L,Tu H W,Chan T S,et al. Mechanistic study of simultaneous arsenic and fluoride removal using granular Ti O2-La adsorbent[J]. Chemical Engineering Journal,2017,313:983-992.
[25] Shi L,Xu C L,Sun X,et al. Facile fabrication of hierarchical BiVO4/Ti O2heterostructures for enhanced photocatalytic activities under visible-light irradiation[J]. Journal of Materials Science,2018,53(16):11329-11342.
[26] Chidambaram D,Halada G P,Clayton C R. Development of a technique to prevent radiation damage of chromate conversion coatings during X-ray photoelectron spectroscopic analysis[J].Applied Surface Science,2001,181(3-4):283-295.
[27] Cao J Y,Zhang Y J,Liu L Q,et al. A p-type Cr-doped Ti O2photo-electrode for photo-reduction[J]. Chemical Communications,2013,49(33):3440-3442.
[2] Velegraki G,Miao J W,Drivas C,et al. Fabrication of 3D mesoporous networks of assembled CoO nanoparticles for efficient photocatalytic reduction of aqueous Cr(Ⅵ)[J]. Applied Catalysis B:Environmental,2018,221:635-644.
[3] Du Y C,Zhang S H,Wang J S,et al. Nb2O5nanowires in-situ grown on carbon fiber:a high-efficiency material for the photocatalytic reduction of Cr(Ⅵ)[J]. Journal of Environmental Sciences,2018,66:358-367.
[4] Zhao D L,Gao X,Wu C N,et al. Facile preparation of amino functionalized graphene oxide decorated with Fe3O4nanoparticles for the adsorption of Cr(Ⅵ)[J]. Applied Surface Science,2016,384:1-9.
[5] Li Y,Cui W Q,Liu L,et al. Removal of Cr(Ⅵ)by 3D Ti O2-graphene hydrogel via adsorption enriched with photocatalytic reduction[J]. Applied Catalysis B:Environmental,2016,199:412-423.
[6] Kumar A,Jena H M. Adsorption of Cr(Ⅵ)from aqueous solution by prepared high surface area activated carbon from Fox nutshell by chemical activation with H3PO4[J]. Journal of Environmental Chemical Engineering,2017,5(2):2032-2041.
[7]陈心满,徐明芳. UV/Ti O2光催化还原Cr(Ⅵ)过程中吸附作用的影响及其消除[J].环境科学,2006,27(5):913-917.Chen X M,Xu M F. Effects of absorption on photo-reduction of Cr(Ⅵ)by UV/Ti O2process and its elimination[J].Environmental Science,2006,27(5):913-917.
[8] Wei M,Wan J M,Hu Z W,et al. Enhanced photocatalytic degradation activity over Ti O2nanotubes co-sensitized by reduced graphene oxide and copper(II)meso-tetra(4-carboxyphenyl)porphyrin[J]. Applied Surface Science,2016,377:149-158.
[9] Li Y N,Chen Z Y,Bao S J,et al. Ultrafine Ti O2encapsulated in nitrogen-doped porous carbon framework for photocatalytic degradation of ammonia gas[J]. Chemical Engineering Journal,2018,331:383-388.
[10] Momeni M M,Nazari Z. Preparation of Ti O2and WO3-Ti O2nanotubes decorated with PbO nanoparticles by chemical bath deposition process:a stable and efficient photo catalyst[J].Ceramics International,2016,42(7):8691-8697.
[11] Sun Q,Hu X L,Zheng S L,et al. Influence of calcination temperature on the structural, adsorption and photocatalytic properties of Ti O2nanoparticles supported on natural zeolite[J].Powder Technology,2015,274:88-97.
[12] Liu H, Liu S, Zhang Z L, et al. Hydrothermal etching fabrication of Ti O2@graphene hollow structures:mutually independent exposed{001}and{101}facets nanocrystals and its synergistic photocaltalytic effects[J]. Scientific Reports,2016,6:33839.
[13] Lara M A,Sayagués M J,Navío J A,et al. A facile shapecontrolled synthesis of highly photoactive fluorine containing Ti O2nanosheets with high{001}facet exposure[J]. Journal of Materials Science,2018,53(1):435-446.
[14] Lu D Z,Chai W Q,Yang M C,et al. Visible light induced photocatalytic removal of Cr(Ⅵ)over Ti O2-based nanosheets loaded with surface-enriched CoOxnanoparticles and its synergism with phenol oxidation[J]. Applied Catalysis B:Environmental,2016,190:44-65.
[15] Han J C,Chen G J,Qin L P,et al. Metal respiratory pathwayindependent cr isotope fractionation during Cr(Ⅵ)reduction by Shewanella oneidensis MR-1[J]. Environmental Science&Technology Letters,2017,4(11):500-504.
[16] Song J Y,Yan L,Duan J M,et al. Ti O2crystal facet-dependent antimony adsorption and photocatalytic oxidation[J]. Journal of Colloid and Interface Science,2017,496:522-530.
[17] Chen M,Ma J Z,Zhang B,et al. Facet-dependent performance of anatase Ti O2for photocatalytic oxidation of gaseous ammonia[J]. Applied Catalysis B:Environmental,2018,223:209-215.
[18] Kebir M,Trari M,Maachi R,et al. Relevance of a hybrid process coupling adsorption and visible light photocatalysis involving a new hetero-system CuCo2O4/Ti O2for the removal of hexavalent chromium[J]. Journal of Environmental Chemical Engineering,2015,3(1):548-559.
[19] Xue C,Zhang T X,Ding S J,et al. Anchoring tailored lowindex faceted BiOBr nanoplates onto Ti O2nanorods to enhance the stability and visible-light-driven catalytic activity[J]. ACS Applied Materials&Interfaces,2017,9(19):16091-16102.
[20] Wu Z B, Yuan X Z, Zeng G M, et al. Highly efficient photocatalytic activity and mechanism of Yb3+/Tm3+codoped In2S3from ultraviolet to near infrared light towards chromium(VI)reduction and rhodamine B oxydative degradation[J].Applied Catalysis B:Environmental,2018,225:8-21.
[21] Wang L,Zhang C B,Gao F,et al. Algae decorated Ti O2/Ag hybrid nanofiber membrane with enhanced photocatalytic activity for Cr(Ⅵ)removal under visible light[J]. Chemical Engineering Journal,2017,314:622-630.
[22] Mohamed A,Osman T A,Toprak M S,et al. Visible light photocatalytic reduction of Cr(Ⅵ)by surface modified CNT/titanium dioxide composites nanofibers[J]. Journal of Molecular Catalysis A:Chemical,2016,424:45-53.
[23] Yan L,Du J J,Jing C Y. How Ti O2facets determine arsenic adsorption and photooxidation:spectroscopic and DFT studies[J]. Catalysis Science&Technology,2016,6(7):2419-2426.
[24] Yan L,Tu H W,Chan T S,et al. Mechanistic study of simultaneous arsenic and fluoride removal using granular Ti O2-La adsorbent[J]. Chemical Engineering Journal,2017,313:983-992.
[25] Shi L,Xu C L,Sun X,et al. Facile fabrication of hierarchical BiVO4/Ti O2heterostructures for enhanced photocatalytic activities under visible-light irradiation[J]. Journal of Materials Science,2018,53(16):11329-11342.
[26] Chidambaram D,Halada G P,Clayton C R. Development of a technique to prevent radiation damage of chromate conversion coatings during X-ray photoelectron spectroscopic analysis[J].Applied Surface Science,2001,181(3-4):283-295.
[27] Cao J Y,Zhang Y J,Liu L Q,et al. A p-type Cr-doped Ti O2photo-electrode for photo-reduction[J]. Chemical Communications,2013,49(33):3440-3442.
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