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This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.
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Titanate nanosheets as highly efficient non-light-driven catalysts for degradation of organic dyes Received 00th January 20xx, Accepted 00th January 20xx
a
a
a
a
a
Chenjuan Zhou, Junjie Luo, Qinqin Chen , Yinzhi Jiang, Xiaoping Dong* and Fangming Cui*
b
DOI: 10.1039/x0xx00000x www.rsc.org/
A novel non-light-driven catalysis by the delaminated two dimensional titanate nanosheets (TNSs) has been explored for degradation of organic dyes with hydrogen peroxide (H2O2). This catalyst can efficiently remove dyes in high concentration and a wide pH range, as well as a long cycle number and a superior universality. As a graphene analogue, two dimensional titanate nanosheets (TNSs) derived from layered precursors are of special importance due to their novel physicochemical properties, such as ultrathin thickness, large surface area and quantum confinement effect.1,2 TNSs-based derivates, for example multilayer films, hollow nanospheres and nanocomposites, have be extensively investigated in nano-electronics, lithium ion batteries, fuel cells, photoluminenscence, photocatalysis and catalysis.3-8 Advanced oxidation processes (AOP) have been considered as a robust strategy for water treatment because of their mild reaction condition, for instance ambient temperature and atmospheric pressure.9,10 As one of the most studied AOP systems, Fenton process involves the decomposing of H2O2 by ferrous ion catalysis to produce strongly oxidative ∙OH radicals, however, meanwhile results in a secondary pollution by homogeneous ferrous catalyst.11,12 Additionally, the required acidic condition (pH below 3)
is also unfavourable for its practical applications. Photocatalytic oxidation provides an alternative route for environment-friendly treating waste water with the produced active species from the 13 photo-excited electron-hole pairs. Currently, the main problems that photocatalysis encountered are the insufficient utilization of solar light and the high recombination ratio of photogenerated 14 charges. Moreover, photocatalytic process cannot proceed once the light irradiation with enough energy is stopped. Therefore, development of efficiently green catalysts with wide application range for wastewater treatments is of urgent importance. Herein, we report a non-light-driven catalytic degradation of organic dyes in a broad pH range by using two-dimensional titanate nanosheets (TNSs) as catalysts and H2O2 as oxidant. As illustrated in scheme 1, the exfoliated TNSs have a unilamellar structure and therefore result in a large surface area (the structure model was exhibited in Fig. S1 ESI†). H2O2 is adsorbed on the surface of TNSs and then is exchanged with the surface ≡Ti-OH groups to form a yellow complex of ≡Ti-OOH.15-17 The activated ≡Ti-OOH groups exhibit strongly oxidative ability that can degrade organic dye molecules to small molecules. In the meantime, ≡Ti-OOH groups are reduced to ≡Ti-OH and the colour is transformed to white again. TNSs were obtained by the soft-chemical delamination of layered protonic titanates (LPT) by ethylamine that was according to our previous reports.18-20 The details of synthetic procedure, physicochemical characterization and catalytic test for degradation of dyes were present in ESI†. As shown in Fig. 1a, the delaminaƟon of LPT formed a stable colloidal suspension and no apparent sedimentation appeared. A clear Tyndall effect was observed, which
Scheme 1 Illustration of non-light driven mechanism for dye degradation by TNSs with H2O2. J. Name., 2013, 00, 1-3 | 1
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Fig. 2 Photographs of (a) TNSs and TNSs-H2O2, (b) rs-TNSs and (c) rs-TNSs-H2O2; (d) UV-vis absorption spectra of TNSs and TNSs-H2O2, and UV-vis diffused-reflection spectra of rs-TNSs and rs-TNSs-H2O2; XPS O1s spectra of (e) TNSs and (f) TNSsH2O2. the meantime, a new peak of 532.2 eV ascribed to O22- group emerged that evidently suggested the graft of ≡Ti-OOH.24 The non-light driven catalytic performance of rs-TNSs (1 g L-1) was demonstrated its colloidal nature. Fig. 1b revealed the atomic force -1 microscope (AFM) image of TNSs that exhibited an extremely thin estimated by degradation of Rhodamine B (RhB 20 mg L ) with -1 thickness of ~1.0 nm and a large lateral size of several hundred H2O2 (0.10 mol L ) in dark (Fig. 3). Preliminary tests proved that RhB nanometres. For facilitating the catalytic test and investigation of could not be removed by individual H2O2 or rs-TNSs. With the reusability for catalyst, we re-stacked TNSs using a hydrochloric acid presence of both rs-TNSs and H2O2, the absorption intensity of RhB solution that was denoted as rs-TNSs. After being re-stacked with solution markedly decreased with the increase of reaction time (Fig. protons, the reassemble of TNSs depicted a loose aggregated 3a). No evident difference appeared in the Fourier transform structure in scanning electron microscopy (SEM) observation (Fig. infrared (FTIR) spectra (Fig. S4 ESI†) of rs-TNSs before and after 1c). Nitrogen sorption data (Fig. S2 ESI†) presented a type IV catalysis reaction, suggesting the stability of catalyst and almost isotherm that suggested a mesoporous structure with large BET complete removal of adsorbed organic compounds. By employing 2 -1 surface area (~ 50 m g ). A clearly stacking of nanosheets was an external standard method in high performance liquid found in the transmission electron microscopy (TEM) image of rs- chromatography (HPLC), the main intermediates (table S5 ESI†) TNSs (Fig. 1d), which implied the structure preservation of intra- were determined as oxalic acid (OA), maleic acid (MA) and player structure of TNSs with the association of X-ray diffraction (XRD) hydroxybenzoic acid (p-HBA). As the reaction proceeding, RhB was results (Fig. S3 ESI†). With the addition of H2O2, the white colour of TNSs and rs-TNSs immediately changed to yellow (Fig. 2a, b and c), which could be ascribed to the modification of ≡Ti-OOH groups on the TNSs surface. Moreover, the preservation for colloidal nature of TNSs-H2O2 indicated the H2O2 treatment had no effect on the structure of TNSs. Excepting for an additionally visible absorption in the TNSs-H2O2 colloid, a similarly spectral shape before and after H2O2 treating was displayed in Fig. 2d that further demonstrated the maintaining of nanosheet structure. The additional shoulder peak in TNS-H2O2 resulted from the exchange of ≡Ti-OH by ≡Ti-OOH. This group substitution was also found in the restacked phases of rs-TNSs and rs-TNSs-H2O2. The modification of ≡Ti-OOH was identified via characterizing the chemical environment of oxygen element by Xray photoelectron spectroscopy (XPS) analysis. As depicted in Fig. 2e, the O1s spectrum of TNSs could be divided into two peaks, Fig. 3 (a) The change of RhB absorption spectra by the nonrespectively centred at 530.1 and 531.6 eV. The former was related light-driven catalysis of rs-TNSs associated with H2O2; activity to Ti-O-Ti situation and the latter was attributed to the surface Ticomparison (b) and the corresponding kinetic data (c) of 21-23 OH. After adsorbing H2O2 on the TNSs surface, the signal of Tidegradation RhB by various catalysts; (d) cyclic performance of rs-TNSs for degradation of RhB. OH drastically weakened in the spectrum of TNSs-H2O2 sample. In Fig. 1 (a) The Tyndall effect and (b) AFM image of TNSs colloidal suspension; (c) SEM and (d) TEM images of rs-TNSs.
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rapidly decomposed to p-HBA that was further degraded to MA and OA. The ratio of (MA + OA)/p-HBA increased with the prolonging of reaction time (Fig. S5 ESI†) indicated the gradual decomposition of dyes to small molecules, which was also been validated by the chemical oxygen demand (COD) investigation (Fig. S6 ESI†). For verifying the mechanism, we checked the H2O2 concentration that was step-by-step consumed with the reaction time (Fig. S7 ESI†). Fig. 3b showed a ~ 50 % decomposition of RhB in the first 20 min and ~ 95 % after 120 min with the catalysis of rs-TNSs. A linear dependence of ln(C/C0) versus time (t) was validated in Fig. 3c, and -1 the rate constant was calculated to be 0.0232 min , which was much higher than those of compared catalysts, including heterogeneous titania-based catalysts of LPT and P25 TiO2 and 2+ Fenton homogeneous catalyst of Fe ions and heterogeneous 2+ catalyst of α-Fe2O3 (table S1 ESI†). A low concentraƟon of Fe (1.0 -1 mg L ) didn’t result in an efficient removal of RhB. With the 2+ -1 increase of Fe concentration to 10 mg L , a ~ 85% removal of RhB was achieved after 120 min, whereas this high concentration general exceeded the legal limit imposed by directives. On the other hand, as substitutes, both two oxides showed poor catalytic performances for the removal of RhB (the degradation efficiency for P25 and α-Fe2O3 were ~ 8 and 12 % after 120 min, respectively). As the starting material of TNSs, the catalytic activity of LPT was quite low. Kinetics studies revealed that the catalytic activity was improved more than 100 times after its exfoliation and subsequent aggregation to rs-TNSs catalyst. This should be ascribed to their notable difference in morphology, structure, and surface area as described above. The successive test for 10 runs (Fig. 3d) implied that this rs-TNSs catalyst exhibited an extremely high stability and a superior reusability. All of 10 cycles presented > 90 % degradation ratios of RhB, and no obvious decrease was checked. Besides the reusability, some other factors were also investigated, including RhB concentration, H2O2 dosage and the initial pH value of RhB solution (Fig. S8-10, table S2-4 ESI†). H2O2 played a key role in such non-light-driven catalysis for degradation of organic pollutants. No dye molecules were decomposed with the absence of H2O2, and the degradation rate gradually increased with the enhancement of H2O2 dosage (Fig. S8 ESI†). From the viewpoint of reacƟon rate and -1 reagent saving, we chose a 0.10 mol L concentration as the dosage of H2O2. Usually, only dye solutions in a low concentration can be degraded by photocatalysis process. However, this non-light driven catalysis could remove dyes in a wide concentration range from -1 5~25 mg L (Fig. S9 ESI†). Even a ~ 70 % degradation ratio was -1 achieved after 120 min for a high RhB concentration (30 mg L ). In general, the pH value of wastewater is critical for the catalytic efficiency of catalyst. For example, Fenton catalysts only work in an acidic situation. With regard to this rs-TNSs catalyst, it could degrade RhB molecules in a wide initial pH range of dye solution from acidic to basic (Fig. S10 ESI†). The universality of this non-lightdriven catalysis was confirmed by degradation of other organic pollutants in Fig. S11 ESI†, where methyl Orange (MO), methylene blue (MB), malachite green (MG) and methyl violet (MV) were also rapidly removed by rs-TNSs with the assistance H2O2 in dark. In conclusion, we have demonstrated that the delaminated two dimensional TNSs exhibited a superior activity, durability and universality for removal of organic dyes by a non-light-driven catalysis. In comparison with traditional AOP technologies, this
strategy is much more energy-saving than photocatalysis and environmental-friendly than Fenton process for avoiding a secondary pollution. We gratefully acknowledge the financial support from the National Natural Science Foundation of China (51202288), the 521 talent project of ZSTU, the program of Graduate Innovation Research in ZSTU (YCX13001) and the project-sponsored by the Scientific Research Foundation (SRF) for the Returned Overseas Chinese Scholars (ROCS), State Education Ministry (SEM).
Notes and references 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
T. Sasaki, M. Watanabe, H. Hashizume, H. Yamada and H. Nakazawa, J. Am. Chem. Soc., 1996, 118, 8329. T. Tanaka, Y. Ebina, K. Takada, K. Kurashima and T. Sasaki, Chem. Mater., 2003, 15, 3564. L. Wang and T. Sasaki, Chem. Rev., 2014, 114, 9455. I. Y. Kim, Y. K. Jo, J. M. Lee, L. Wang and S. J. Hwang, J. Phys. Chem. Lett., 2014, 5, 4149. R. Ma and T. Sasaki, Adv. Mater., 2010, 22, 5082. M. Osada, Y. Ebina, K. Takada, T. Sasaki, Adv. Mater., 2006, 18, 295. J. H. Kang, S. M. Paek and J. H. Choy, Chem. Commun., 2012, 48, 458. H. N. Kim, T. W. Kim, I. Y. Kim and S. J. Hwang, Adv. Funct. Mater., 2011, 21, 3111. R. Andreozzi, V. Caprio, A. Insola and R. Marotta, Catal. Today, 1999, 53, 51. C. Comninellis, A. Kapalka, S. Malato, S. A. Parsons, I. Poulios and D. Mantzavios, J. Chem. Technol. Biot., 2008, 83, 769. C. Wang, S. Zhang, Y. Sakai and Z. Zhang, Water Sci.Technol., 2014, 69, 1115. G. Zhao, X. Peng, H. Li, J. Wang, L. Zhou, T. Zhao, Z. Huang and H. Jiang, Chem. Commun., 2015, 51, 7489. X. Chen, S. Shen, L. Guo and S. Mao, Chem. Rev., 2010, 110, 6503. H. Tong, S. Ouyang, Y. Bi, N. Umezawa, M. Oshikiri and J. Ye, Adv. Mater., 2012, 24, 229. H. Boonstra and C.H.A. Mutsaers, J. Phys. Chem., 1975, 79, 1940. X. Li, C. Chen and J. Zhao, Langmuir, 2001, 17, 4118. Y. Jin, G. Zhao, M. Wu, Y. Lei, M. Li and X. Jin, J. Phys. Chem. C, 2011, 115, 9917 J. Fu, Y. Tian, B. Chang, F. Xi and X. Dong, Chem. Eng. J., 2013, 219, 155. Y. Tian, B. Chang, J. Fu, F. Xi and X. Dong, Powder Technol., 2013, 245, 227. J. Luo, Q. Chen and X. Dong, Powder Technol., 2015, 275, 284. Y. Besseklhouad, D. Robert and J.V. Weber, J. Photoch. Photobio. A, 2003, 157, 47. E. Gianotti, C. Bisio, L. Marchese, M. Guidotti, N. Ravasio, R. Psaro and S. Coluccia, J. Phys. Chem. C, 2007, 111, 5083. D. Zhao, G. Sheng, C. Chen and X. Wang, Appl. Catal. B, 2012, 111–112, 303. G. Xiang, D. Wu, J. He and X. Wang, Chem. Commun., 2011, 47, 11456.
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ChemComm Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: C. Zhou, J. Luo, Q. Chen, Y. Jiang, X. Dong and F. Cui, Chem. Commun., 2015, DOI: 10.1039/C5CC03279B.
This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.
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Titanate nanosheets as highly efficient non-light-driven catalysts for degradation of organic dyes Received 00th January 20xx, Accepted 00th January 20xx
a
a
a
a
a
Chenjuan Zhou, Junjie Luo, Qinqin Chen , Yinzhi Jiang, Xiaoping Dong* and Fangming Cui*
b
DOI: 10.1039/x0xx00000x www.rsc.org/
A novel non-light-driven catalysis by the delaminated two dimensional titanate nanosheets (TNSs) has been explored for degradation of organic dyes with hydrogen peroxide (H2O2). This catalyst can efficiently remove dyes in high concentration and a wide pH range, as well as a long cycle number and a superior universality. As a graphene analogue, two dimensional titanate nanosheets (TNSs) derived from layered precursors are of special importance due to their novel physicochemical properties, such as ultrathin thickness, large surface area and quantum confinement effect.1,2 TNSs-based derivates, for example multilayer films, hollow nanospheres and nanocomposites, have be extensively investigated in nano-electronics, lithium ion batteries, fuel cells, photoluminenscence, photocatalysis and catalysis.3-8 Advanced oxidation processes (AOP) have been considered as a robust strategy for water treatment because of their mild reaction condition, for instance ambient temperature and atmospheric pressure.9,10 As one of the most studied AOP systems, Fenton process involves the decomposing of H2O2 by ferrous ion catalysis to produce strongly oxidative ∙OH radicals, however, meanwhile results in a secondary pollution by homogeneous ferrous catalyst.11,12 Additionally, the required acidic condition (pH below 3)
is also unfavourable for its practical applications. Photocatalytic oxidation provides an alternative route for environment-friendly treating waste water with the produced active species from the 13 photo-excited electron-hole pairs. Currently, the main problems that photocatalysis encountered are the insufficient utilization of solar light and the high recombination ratio of photogenerated 14 charges. Moreover, photocatalytic process cannot proceed once the light irradiation with enough energy is stopped. Therefore, development of efficiently green catalysts with wide application range for wastewater treatments is of urgent importance. Herein, we report a non-light-driven catalytic degradation of organic dyes in a broad pH range by using two-dimensional titanate nanosheets (TNSs) as catalysts and H2O2 as oxidant. As illustrated in scheme 1, the exfoliated TNSs have a unilamellar structure and therefore result in a large surface area (the structure model was exhibited in Fig. S1 ESI†). H2O2 is adsorbed on the surface of TNSs and then is exchanged with the surface ≡Ti-OH groups to form a yellow complex of ≡Ti-OOH.15-17 The activated ≡Ti-OOH groups exhibit strongly oxidative ability that can degrade organic dye molecules to small molecules. In the meantime, ≡Ti-OOH groups are reduced to ≡Ti-OH and the colour is transformed to white again. TNSs were obtained by the soft-chemical delamination of layered protonic titanates (LPT) by ethylamine that was according to our previous reports.18-20 The details of synthetic procedure, physicochemical characterization and catalytic test for degradation of dyes were present in ESI†. As shown in Fig. 1a, the delaminaƟon of LPT formed a stable colloidal suspension and no apparent sedimentation appeared. A clear Tyndall effect was observed, which
Scheme 1 Illustration of non-light driven mechanism for dye degradation by TNSs with H2O2. J. Name., 2013, 00, 1-3 | 1
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Fig. 2 Photographs of (a) TNSs and TNSs-H2O2, (b) rs-TNSs and (c) rs-TNSs-H2O2; (d) UV-vis absorption spectra of TNSs and TNSs-H2O2, and UV-vis diffused-reflection spectra of rs-TNSs and rs-TNSs-H2O2; XPS O1s spectra of (e) TNSs and (f) TNSsH2O2. the meantime, a new peak of 532.2 eV ascribed to O22- group emerged that evidently suggested the graft of ≡Ti-OOH.24 The non-light driven catalytic performance of rs-TNSs (1 g L-1) was demonstrated its colloidal nature. Fig. 1b revealed the atomic force -1 microscope (AFM) image of TNSs that exhibited an extremely thin estimated by degradation of Rhodamine B (RhB 20 mg L ) with -1 thickness of ~1.0 nm and a large lateral size of several hundred H2O2 (0.10 mol L ) in dark (Fig. 3). Preliminary tests proved that RhB nanometres. For facilitating the catalytic test and investigation of could not be removed by individual H2O2 or rs-TNSs. With the reusability for catalyst, we re-stacked TNSs using a hydrochloric acid presence of both rs-TNSs and H2O2, the absorption intensity of RhB solution that was denoted as rs-TNSs. After being re-stacked with solution markedly decreased with the increase of reaction time (Fig. protons, the reassemble of TNSs depicted a loose aggregated 3a). No evident difference appeared in the Fourier transform structure in scanning electron microscopy (SEM) observation (Fig. infrared (FTIR) spectra (Fig. S4 ESI†) of rs-TNSs before and after 1c). Nitrogen sorption data (Fig. S2 ESI†) presented a type IV catalysis reaction, suggesting the stability of catalyst and almost isotherm that suggested a mesoporous structure with large BET complete removal of adsorbed organic compounds. By employing 2 -1 surface area (~ 50 m g ). A clearly stacking of nanosheets was an external standard method in high performance liquid found in the transmission electron microscopy (TEM) image of rs- chromatography (HPLC), the main intermediates (table S5 ESI†) TNSs (Fig. 1d), which implied the structure preservation of intra- were determined as oxalic acid (OA), maleic acid (MA) and player structure of TNSs with the association of X-ray diffraction (XRD) hydroxybenzoic acid (p-HBA). As the reaction proceeding, RhB was results (Fig. S3 ESI†). With the addition of H2O2, the white colour of TNSs and rs-TNSs immediately changed to yellow (Fig. 2a, b and c), which could be ascribed to the modification of ≡Ti-OOH groups on the TNSs surface. Moreover, the preservation for colloidal nature of TNSs-H2O2 indicated the H2O2 treatment had no effect on the structure of TNSs. Excepting for an additionally visible absorption in the TNSs-H2O2 colloid, a similarly spectral shape before and after H2O2 treating was displayed in Fig. 2d that further demonstrated the maintaining of nanosheet structure. The additional shoulder peak in TNS-H2O2 resulted from the exchange of ≡Ti-OH by ≡Ti-OOH. This group substitution was also found in the restacked phases of rs-TNSs and rs-TNSs-H2O2. The modification of ≡Ti-OOH was identified via characterizing the chemical environment of oxygen element by Xray photoelectron spectroscopy (XPS) analysis. As depicted in Fig. 2e, the O1s spectrum of TNSs could be divided into two peaks, Fig. 3 (a) The change of RhB absorption spectra by the nonrespectively centred at 530.1 and 531.6 eV. The former was related light-driven catalysis of rs-TNSs associated with H2O2; activity to Ti-O-Ti situation and the latter was attributed to the surface Ticomparison (b) and the corresponding kinetic data (c) of 21-23 OH. After adsorbing H2O2 on the TNSs surface, the signal of Tidegradation RhB by various catalysts; (d) cyclic performance of rs-TNSs for degradation of RhB. OH drastically weakened in the spectrum of TNSs-H2O2 sample. In Fig. 1 (a) The Tyndall effect and (b) AFM image of TNSs colloidal suspension; (c) SEM and (d) TEM images of rs-TNSs.
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rapidly decomposed to p-HBA that was further degraded to MA and OA. The ratio of (MA + OA)/p-HBA increased with the prolonging of reaction time (Fig. S5 ESI†) indicated the gradual decomposition of dyes to small molecules, which was also been validated by the chemical oxygen demand (COD) investigation (Fig. S6 ESI†). For verifying the mechanism, we checked the H2O2 concentration that was step-by-step consumed with the reaction time (Fig. S7 ESI†). Fig. 3b showed a ~ 50 % decomposition of RhB in the first 20 min and ~ 95 % after 120 min with the catalysis of rs-TNSs. A linear dependence of ln(C/C0) versus time (t) was validated in Fig. 3c, and -1 the rate constant was calculated to be 0.0232 min , which was much higher than those of compared catalysts, including heterogeneous titania-based catalysts of LPT and P25 TiO2 and 2+ Fenton homogeneous catalyst of Fe ions and heterogeneous 2+ catalyst of α-Fe2O3 (table S1 ESI†). A low concentraƟon of Fe (1.0 -1 mg L ) didn’t result in an efficient removal of RhB. With the 2+ -1 increase of Fe concentration to 10 mg L , a ~ 85% removal of RhB was achieved after 120 min, whereas this high concentration general exceeded the legal limit imposed by directives. On the other hand, as substitutes, both two oxides showed poor catalytic performances for the removal of RhB (the degradation efficiency for P25 and α-Fe2O3 were ~ 8 and 12 % after 120 min, respectively). As the starting material of TNSs, the catalytic activity of LPT was quite low. Kinetics studies revealed that the catalytic activity was improved more than 100 times after its exfoliation and subsequent aggregation to rs-TNSs catalyst. This should be ascribed to their notable difference in morphology, structure, and surface area as described above. The successive test for 10 runs (Fig. 3d) implied that this rs-TNSs catalyst exhibited an extremely high stability and a superior reusability. All of 10 cycles presented > 90 % degradation ratios of RhB, and no obvious decrease was checked. Besides the reusability, some other factors were also investigated, including RhB concentration, H2O2 dosage and the initial pH value of RhB solution (Fig. S8-10, table S2-4 ESI†). H2O2 played a key role in such non-light-driven catalysis for degradation of organic pollutants. No dye molecules were decomposed with the absence of H2O2, and the degradation rate gradually increased with the enhancement of H2O2 dosage (Fig. S8 ESI†). From the viewpoint of reacƟon rate and -1 reagent saving, we chose a 0.10 mol L concentration as the dosage of H2O2. Usually, only dye solutions in a low concentration can be degraded by photocatalysis process. However, this non-light driven catalysis could remove dyes in a wide concentration range from -1 5~25 mg L (Fig. S9 ESI†). Even a ~ 70 % degradation ratio was -1 achieved after 120 min for a high RhB concentration (30 mg L ). In general, the pH value of wastewater is critical for the catalytic efficiency of catalyst. For example, Fenton catalysts only work in an acidic situation. With regard to this rs-TNSs catalyst, it could degrade RhB molecules in a wide initial pH range of dye solution from acidic to basic (Fig. S10 ESI†). The universality of this non-lightdriven catalysis was confirmed by degradation of other organic pollutants in Fig. S11 ESI†, where methyl Orange (MO), methylene blue (MB), malachite green (MG) and methyl violet (MV) were also rapidly removed by rs-TNSs with the assistance H2O2 in dark. In conclusion, we have demonstrated that the delaminated two dimensional TNSs exhibited a superior activity, durability and universality for removal of organic dyes by a non-light-driven catalysis. In comparison with traditional AOP technologies, this
strategy is much more energy-saving than photocatalysis and environmental-friendly than Fenton process for avoiding a secondary pollution. We gratefully acknowledge the financial support from the National Natural Science Foundation of China (51202288), the 521 talent project of ZSTU, the program of Graduate Innovation Research in ZSTU (YCX13001) and the project-sponsored by the Scientific Research Foundation (SRF) for the Returned Overseas Chinese Scholars (ROCS), State Education Ministry (SEM).
Notes and references 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
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