A Quantitative Study of Photocatalytic Reduction of Cr(Ⅵ) by Operando Low-Field NMR Relaxometry

doi:10.11938/cjmr20202815

Abstract

Abstract:

In this work, operando low-field nuclear magnetic resonance (LF-NMR) technology was used to quantitatively study the photocatalytic reduction of Cr(Ⅵ) in a real solid-liquid reaction environment. The performance of Ag/g-C₃N₄ photocatalysts with different loadings of Ag for the photocatalytic reduction of aqueous Cr(Ⅵ) to Cr(Ⅲ) under visible-light irradiation was systematically investigated. The results showed that the addition of Ag cocatalysts (Ag loading amount: 1 wt.%, 2 wt.%, 5 wt.%, and 10 wt.%) significantly enhanced the photocatalytic performance of g-C₃N₄ photocatalysts, while the optimal content of Ag loading was 5 wt.%, which was greater than that of pristine g-C₃N₄ by a factor of 4.0. Furthermore, we carried out a quantitative analysis on the concentration of paramagnetic Cr(Ⅲ) ions in solution by using the transverse relaxation time (T₂) values, and proved the viability of employing operando LF-NMR relaxometry for monitoring the photocatalytic Cr(Ⅵ) reduction performance.

Key words: operando LF-NMR, g-C₃N₄, Ag loading, photocatalytic, Cr(Ⅵ) reduction, transverse relaxation time (T₂)

CLC Number:

O482.53

Xing-xing NIU,Zhi-jie BAI,Yi YANG,Yang-wen GAO,Xue-lu WANG,Ye-feng YAO. A Quantitative Study of Photocatalytic Reduction of Cr(Ⅵ) by Operando Low-Field NMR Relaxometry[J]. Chinese Journal of Magnetic Resonance, 2021, 38(3): 403-413.

Figures/Tables 12

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References 35

1	ZHANG K M , WEN Z G . Review and challenges of policies of environmental protection and sustainable development in China[J]. J Environ Manage, 2008, 88 (4): 1249- 1261. doi: 10.1016/j.jenvman.2007.06.019
2	WANG H , YUAN X , WU Y , et al. Facile synthesis of amino-functionalized titanium metal-organic frameworks and their superior visible-light photocatalytic activity for Cr(Ⅵ) reduction[J]. J Hazard Mater, 2015, 286, 187- 194. doi: 10.1016/j.jhazmat.2014.11.039
3	ZHAO Z , AN H , LIN J , et al. Progress on the photocatalytic reduction removal of chromium contamination[J]. Chem Rec, 2019, 19 (5): 873- 882. doi: 10.1002/tcr.201800153
4	HAYASHI H , KATAYAMA S , KOMURA T , et al. Discovery of a novel Sn(Ⅱ)-based oxide β-SnMoO₄ for daylight-driven photocatalysis[J]. Adv Sci, 2017, 4 (1): 1600246. doi: 10.1002/advs.201600246
5	YUAN Y , ZHANG L , XING J , et al. High-yield synthesis and optical properties of g-C₃N₄[J]. Nanoscale, 2015, 7 (29): 12343- 12350. doi: 10.1039/C5NR02905H
6	ZHANG J , ZHANG M , YANG C , et al. Nanospherical carbon nitride frameworks with sharp edges accelerating charge collection and separation at a soft photocatalytic interface[J]. Adv Mater, 2014, 26 (24): 4121- 4126. doi: 10.1002/adma.201400573
7	RAN J , MA T Y , GAO G , et al. Porous P-doped graphitic carbon nitride nanosheets for synergistically enhanced visible-light photocatalytic H₂ production[J]. Energ Environ Sci, 2015, 8 (12): 3708- 3717. doi: 10.1039/C5EE02650D
8	SHI F , CHEN L , CHEN M , et al. A g-C₃N₄/nanocarbon/ZnIn₂S₄ nanocomposite: an artificial Z-scheme visible-light photocatalytic system using nanocarbon as the electron mediator[J]. Chem Commun, 2015, 51 (96): 17144- 17147. doi: 10.1039/C5CC05323D
9	ZHANG P , WANG T , GONG J . Mechanistic understanding of the plasmonic enhancement for solar water splitting[J]. Adv Mater, 2015, 27 (36): 5328- 5342. doi: 10.1002/adma.201500888
10	LIU X , PANG F , HE M , et al. Confined reaction inside nanotubes: New approach to mesoporous g-C₃N₄ photocatalysts[J]. Nano Res, 2017, 10 (11): 3638- 3647. doi: 10.1007/s12274-017-1574-7
11	TEIXEIRA I F , BARBOSA E C M , TSANG S C E , et al. Carbon nitrides and metal nanoparticles: from controlled synthesis to design principles for improved photocatalysis[J]. Chem Soc Rev, 2018, 47 (20): 7783- 7817. doi: 10.1039/C8CS00479J
12	XING J , CHEN J F , LI Y H , et al. Stable isolated metal atoms as active sites for photocatalytic hydrogen evolution[J]. Chem Eur J, 2014, 20 (8): 2138- 2144. doi: 10.1002/chem.201303366
13	CHOI Y , KIM H I , MOON G H , et al. Boosting up the low catalytic activity of silver for H₂ production on Ag/TiO₂ photocatalyst: thiocyanate as a selective modifier[J]. ACS Catal, 2016, 6 (2): 821- 828. doi: 10.1021/acscatal.5b02376
14	LIU W , JIN L , XU J , et al. Insight into pH dependent Cr(Ⅵ) removal with magnetic Fe₃S₄[J]. Chem Eng J, 2019, 359, 564- 571. doi: 10.1016/j.cej.2018.11.192
15	LIU X , LIU B , LI L , et al. Cu₂In₂ZnS₅/Gd₂O₂S: Tb for full solar spectrum photoreduction of Cr(Ⅵ) and CO₂ from UV/vis to near-infrared light[J]. Appl Catal Environ, 2019, 249, 82- 90. doi: 10.1016/j.apcatb.2019.02.061
16	GOMES B F , BURATO J S , SILVA LOBO C M , et al. Use of the relaxometry technique for quantification of paramagnetic ions in aqueous solutions and a comparison with other analytical methods[J]. Int J Anal Chem, 2016, 2016, 8256437.
17	HUA L , CHAN Y C , WU Y P , et al. The determination of hexavalent chromium (Cr⁶⁺) in electronic and electrical components and products to comply with RoHS regulations[J]. J Hazard Mater, 2009, 163 (2): 1360- 1368.
18	KOCK F V C , MACHADO M P , ATHAYDE G P B , et al. Quantification of paramagnetic ions in solution using time domain NMR. PROS and CONS to optical emission spectrometry method[J]. Microchem J, 2018, 137, 204- 207. doi: 10.1016/j.microc.2017.10.013
19	CHENG S , WANG X , LIU B L . Low field-NMR relaxation characteristics of glyceryl oleate system[J]. Chinese J Magn Reson, 2018, 35 (2): 243- 254.
	成实, 王欣, 刘宝林. 油酸甘油酯体系的低场核磁共振弛豫特性研究[J]. 波谱学杂志, 2018, 35 (2): 243- 254.
20	LIU Z J , YANG D , SHAO J X , et al. Evolution of pore connectivity in the fushun oil shale by low-field nuclear magnetic resonance spectroscopy[J]. Chinese J Magn Reson, 2019, 36 (3): 309- 318.
	刘志军, 杨栋, 邵继喜, 等. 基于低场核磁共振的抚顺油页岩孔隙连通性演化研究[J]. 波谱学杂志, 2019, 36 (3): 309- 318.
21	BERNHEIM R A , BROWN T H , GUTOWSKY H S , et al. Temperature dependence of proton relaxation times in aqueous solutions of paramagnetic ions[J]. J Chem Phys, 1959, 30 (4): 950- 956. doi: 10.1063/1.1730133
22	BLOEMBERGEN N , PURCELL E M , POUND R V . Relaxation effects in nuclear magnetic resonance absorption[J]. Phys Rev, 1948, 73 (7): 679- 712. doi: 10.1103/PhysRev.73.679
23	ZHAO C , WANG Z , LI X , et al. Facile fabrication of BUC-21/Bi₂₄O₃₁Br₁₀ composites for enhanced photocatalytic Cr(Ⅵ) reduction under white light[J]. Chem Eng J, 2020, 389 (123431)
24	FU Y , ZHU J , HU C , et al. Covalently coupled hybrid of graphitic carbon nitride with reduced graphene oxide as a superior performance lithium-ion battery anode[J]. Nanoscale, 2014, 6 (21): 12555- 12564. doi: 10.1039/C4NR03145H
25	MA S , ZHAN S , JIA Y , et al. Enhanced disinfection application of Ag-modified g-C₃N₄ composite under visible light[J]. Appl Catal Environ, 2016, 186, 77- 87. doi: 10.1016/j.apcatb.2015.12.051
26	QIN J , HUO J , ZHANG P , et al. Improving the photocatalytic hydrogen production of Ag/g-C₃N₄ nanocomposites by dye-sensitization under visible light irradiation[J]. Nanoscale, 2016, 8 (4): 2249- 59. doi: 10.1039/C5NR06346A
27	YI J , SHE X , SONG Y , et al. A silver on 2D white-C₃N₄ support photocatalyst for mechanistic insights: synergetic utilization of plasmonic effect for solar hydrogen evolution[J]. RSC Adv, 2016, 6 (113): 112420- 112428. doi: 10.1039/C6RA23964A
28	JIN J , LIANG Q , DING C , et al. Simultaneous synthesis-immobilization of Ag nanoparticles functionalized 2D g-C₃N₄ nanosheets with improved photocatalytic activity[J]. J Alloys Comp, 2017, 691, 763- 771. doi: 10.1016/j.jallcom.2016.08.302
29	FAISAL M , ISMAIL A A , HARRAZ F A , et al. Synthesis of highly dispersed silver doped g-C₃N₄ nanocomposites with enhanced visible-light photocatalytic activity[J]. Mater Des, 2016, 98, 223- 230. doi: 10.1016/j.matdes.2016.03.019
30	ZHANG Y , WU J , DENG Y , et al. Synthesis and visible-light photocatalytic property of Ag/GO/g-C₃N₄ ternary composite[J]. Mater Sci Eng: B, 2017, 221, 1- 9. doi: 10.1016/j.mseb.2017.03.013
31	COBRA P F , GOMES B F , MITRE C I N , et al. Measuring the solubility product constant of paramagnetic cations using time-domain nuclear magnetic resonance relaxometry[J]. Microchem J, 2015, 121, 14- 17. doi: 10.1016/j.microc.2015.02.002
32	KOCK F V C , COLNAGO L A . Rapid and simultaneous relaxometric methods to study paramagnetic ion complexes in solution: An alternative to spectrophotometry[J]. Microchem J, 2015, 122, 144- 148. doi: 10.1016/j.microc.2015.05.003
33	KOCK F V , MONARETTO T , COLNAGO L A . Time-domain NMR relaxometry as an alternative method for analysis of chitosan-paramagnetic ion interactions in solution[J]. Int J Biol Macromol, 2017, 98, 228- 232. doi: 10.1016/j.ijbiomac.2017.01.083
34	GOMEZ V , LARRECHI M S , CALLAO M P . Chromium speciation using sequential injection analysis and multivariate curve resolution[J]. Anal Chim Acta, 2006, 571 (1): 129- 35. doi: 10.1016/j.aca.2006.04.065
35	SOARES R , CASTRO CARNEIROA M , IN S COUTO MONTEIRO M , et al. Simultaneous speciation of chromium by spectrophotometry and multicomponent analysis[J]. Chem Spec Bioavailab, 2015, 21 (3): 153- 160.

紫外分光光度法Cr(Ⅲ)体系		紫外分光光度法Cr(Ⅵ)-Cr(Ⅲ)混合体系		LF-NMR法Cr(Ⅲ)体系		LF-NMR法Cr(Ⅵ)-Cr(Ⅲ)混合体系
Cr(Ⅲ)浓度/(mg/L)	Cr(Ⅲ)-EDTA吸光度	Cr(Ⅵ)-Cr(Ⅲ)浓度/(mg/L)	Cr(Ⅲ)-EDTA吸光度	Cr(Ⅲ)浓度/(mg/L)	T₂/s	Cr(Ⅵ)-Cr(Ⅲ)浓度/(mg/L)	T₂/s
1	0.007	20-0	0	1	1.528	20-0	3.105
5	0.024	15-5	0.021	5	0.623	15-5	0.604
10	0.038	10-10	0.044	10	0.375	10-10	0.363
15	0.056	5-15	0.056	15	0.276	5-15	0.267
20	0.066	0-20	0.066	20	0.216	0-20	0.216

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