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Article

Investigation of Microstructure and Photocatalytic Performance of a Modified Zeolite Supported Nanocrystal TiO2 Composite

by
Gang Liao
*,†,
Wei He
† and
Yuming He
Department of Transportation and Municipal Engineering, Sichuan College of Architectural Technology, Chengdu 610399, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Catalysts 2019, 9(6), 502; https://doi.org/10.3390/catal9060502
Submission received: 9 May 2019 / Revised: 27 May 2019 / Accepted: 30 May 2019 / Published: 31 May 2019
(This article belongs to the Special Issue Photocatalysis and Environment)
Browse Figures
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Abstract

:
A modified zeolite/TiO2 composite (MZTC) was prepared through a method of saturated infiltration and synthesis in situ. The crystalline phase, micromorphology, elementary composition, specific surface area, pore size distribution, chemical bond and band gap variation of the products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), BET specific surface area and pore size distribution analysis (BET), Fourier transform infrared spectroscopy (FTIR) and UV–vis diffuse reflectance spectroscopy (UV-vis DRS), respectively. The microscopic characterization results showed that TiO2 was homogeneously dispersed in the structure of zeolite at the nanoscale range, and a strong chemical bond was established between TiO2 and zeolite. The photocatalytic performance of MZTC was evaluated by studying the degradation rate of methylene blue (MB) dye in aqueous solution under UV-light irradiation. The results of the degradation experiment showed that the MB degradation rate of MZTC-2.5 was the highest, reaching 93.6%, which was 2.4 times higher than hydrolysis TiO2 powder (HTOP) containing the same mass of pure TiO2. The MB degradation rate of MZTC-2.5 still maintained 86.5% after five tests, suggesting the excellent recyclability of MZTC-2.5. The possible mechanism of MB degradation was also discussed.

Graphical Abstract

1. Introduction

In recent decades, the water pollution caused by organic contaminants, such as dyes, antibiotics, polycyclic aromatic hydrocarbons and phenols, is becoming a serious concern worldwide [1,2,3,4]. Scientists have carried out numerous solutions to control the water pollution and several achievements have been made [5,6,7,8,9,10]. Nowadays, whatever technique is applied to purify the contaminated water, consideration must be given to purification efficiency, cost, operability, and durability. Photocatalytic oxidation (PCO) based on TiO2 displays excellent prospects in environmental purification owing to its high efficiency, non-toxicity, low cost, and chemical stability [11,12,13,14]. It is well known that reactive oxygen species (ROS) like ·OH radicals generated on the surface of TiO2 bear strong oxidative power, so most organic-based compounds undergo complete mineralization to end products such as H2O and CO2. To enhance the photocatalytic activity, TiO2 is usually fabricated into nanoparticles or a one-dimensional (1-D) fibrous structure and modified by doping heteroatoms or introducing noble metals [15,16,17]. Although the photocatalytic performance has been improved, there are new challenges appearing along with the wide application of nano-TiO2. The TiO2 nanoparticles are easily agglomerated in water due to high surface energy, which leads to a reduction in photocatalytic efficiency [11]. There is evidence that TiO2 nanoparticles are discharged into aquatic ecosystems during their application [18]. If the nanoparticle can not be removed from water, TiO2 will enter drinking water sources and natural aquatic environments, increasing the risk of exposure to plants, animals and humans [19]. The adsorption capacity of the catalyst towards the pollutant governs the photocatalytic decomposition efficiency, especially at low concentrations. The photocatalytic efficiency of TiO2 is often limited due to its low adsorption ability as well as the low concentration of pollutants in ambient water [20,21,22]. To deal with these new challenges, it is vital to firmly immobilize TiO2 nanoparticles on the substrate and improve the adsorption of the catalyst.
Many materials have been utilized for supporting TiO2 [21,23,24,25,26], among which natural zeolite (NZ) was proven to be the most desirable supporting material due to its high specific surface area, high adsorption capacity, and high stability [27,28,29]. Zeolite supported nano-TiO2 composites have been intensively studied for years and research shows that the hybrid zeolite/TiO2 composites exhibit good photocatalytic degradation performance [24,30,31,32,33]. According to previous works, the outstanding adsorptive ability of zeolite has been commonly used to enhance the photocatalytic activity of zeolite/TiO2 composites, because zeolites act as electron donors and acceptors of moderate strength to the guest species based on the adsorption site and could enrich the pollutants around TiO2 and then accelerate the photocatalytic rate [34,35,36]. The level and nature of the interaction of zeolite and TiO2 determine the microstructures of the zeolite/TiO2 composite, which deeply influence the photocatalytic performance. Domoroshchina et al. [20] thought the interaction between components depends on the methods and conditions for obtaining nanocomposites. There are numerous cavities in the framework of zeolite which can not only act as adsorbers, but provide the possibility to enhance the interaction of TiO2 and zeolite. Currently, most zeolite/TiO2 composites have been synthesized through the sol-gel method at normal pressure and temperature, which is easy to realize [37,38,39,40]. However, most zeolite/TiO2 composites are a mixture of TiO2 and zeolite with altered microstructural characteristics, which is not enough to exploit the advantages of zeolite/TiO2.
In the present study, the aim is to synthesize a composite with high efficiency and stable properties. The method of saturated infiltration and synthesis in situ was proposed. Different from the conventional sol-gel method, NZ was firstly immersed in the TiO2 sol under negative pressure to ensure every cavity was filled with sol and then nanocrystal TiO2 was formed in situ under heat treatment. The physical and chemical properties of MZTC were investigated using a variety of micro characterization methods. The photocatalytic efficiency of MZTC was evaluated by degrading methylene blue (MB) in aqueous solution, which is a representative organic pollutant in the textile wastewater industry.

2. Results and Discussion

2.1. Physicochemical Properties

X-ray diffraction (XRD) patterns of the samples are shown in Figure 1. Compared with commercial TiO2 (P25), HTOP prepared by the sol-gel route is proved to be anatase TiO2. The crystallite size of the HTOP and P25 are about 10 nm and 25 nm, respectively, as calculated by the Scherrer equation [17]. The phase compositions of NZ, MZ and MZTC-2.5 are SiO2 and K2.04Na0.06Al2Si7.8O20.7. The intensity of the diffraction peaks of MZ and MZTC-2.5 are weaker than NZ, because the Si in the zeolite skeleton was selectively dissolved and the chemical-bonding water was destroyed. The X-ray pattern of MZTC-2.5 is almost the same as MN and the characteristic peaks of TiO2 are not observed in the diffraction patterns of MZTC-2.5, which may contribute to the low content and small size of TiO2. The absence of TiO2 characteristic peaks indicate that the nanocrystal TiO2 are well dispersed on the zeolite surface and the growth of large-size TiO2 crystallites is prevented [41], which is conductive to improve the photocatalytic activity of MZTC [42].
Figure 2a,b show the scanning electron microscopy (SEM) images of P25 and HTOP, respectively. It can be observed that P25 is stacked with nanoparticles with a diameter of approximately 25 nm, which is in accordance with the XRD result. The HTOP is of block shape and the TiO2 particles are compacted after calcination of 400 °C. Figure 2c,d show the morphologies of NZ and MZ, respectively. It can be clearly seen that NZ is formed from stacking plate-like units and the surface is regular and smooth. After modification, the surface of MZ is irregular and rough and many micron-sized cavities can be observed. This is because the impurities in the pore were removed, leading to an open and clear pore system, which contribute to the diffusion and adsorption of the pollutant. Figure 2e shows the morphologies of MZTC-2.5. It can be seen that the microstructures of MZTC-2.5 were almost same as MZ and the agglomeration of TiO2 was not observed on the surface of MZTC-2.5, which was also identified by the XRD results. Combined with the micrograph of HTOP, it can be inferred that the absence of the agglomeration of TiO2 was due to the interaction of TiO2 and zeolite, which inhabits the growth of large-size TiO2 crystallites and the agglomeration of TiO2 particles. Three random points on the surface of MZTC-2.5 were selected for energy dispersive spectroscopy (EDS) analysis, the results of which are shown in Figure 2f–h. The content of Ti at each point exceeded 10%, which confirmed that the nano-TiO2 had already been deposited on the structure of MZTC-2.5. The Ti content of the three points was approximately equal to each other, indicating the uniform distribution of TiO2.
The nitrogen adsorption–desorption isotherms of MZ and MZTC-2.5 are presented in Figure 3a. For MZ, the isotherm is of type III and IV (BDDT classification) [43,44]. At low relative pressure, the adsorbed volume of N2 is small, indicating the absence of micropores or the weak force between MZ and N2 (type III). However, at a high relative pressure range (between 0.3 and 0.9), the isotherm displays a small hysteresis loop, confirming the presence of mesopores (type IV). This is also demonstrated by its corresponding pore-size distribution curve in Figure 3b. The shape of the hysteresis loop is of type H3, which is associated with the stack of plate-like particles, generating slit-like pores [44]. This is also confirmed by the SEM images of MZ. Loading nano-TiO2 on the surface of MZ causes a certain influence on the isotherm. The shape of the isotherm of MZTC-2.5 is similar to MZ, but the hysteresis loop of MZTC-2.5 is larger, suggesting that the pore size distribution range of MZTC-2.5 is wider. This is in accordance with the pore-size distribution curves in Figure 3b. Moreover, the specific surface area of MZTC-2.5 (293 m2g−1) is lower than that of MZ (392 m2g−1), as shown in Table 1. This is closely related to the changes of the pore system of MZ. After saturated infiltration and calcination, the mesopores in MZ were filled with nano-TiO2 particles, thus leading to the formation of stack holes, so the specific surface area of MZ was reduced. The schematic diagram of the nano-TiO2 distribution in MZTC-2.5 is shown in Figure 4. It can be inferred that TiO2 particles are homogeneously dispersed in MZTC-n (n = 0.5, 1, 2.5, 5) at the nanoscale range.
The infrared spectrum of MZTC-2.5 is shown in Figure 5. The middle infrared spectrum region (400–2000 cm−1) displays the features of the chemical bonds of zeolite [45]. The absorption peaks at the range of 400–1200 cm−1 are associated with the Si–O(Si) and Si–O(Al) stretching vibrations inside the (Al,Si)O4 tetrahedrons [46]. The infrared peaks at 1060 cm−1 and 1090 cm−1 are correlated with the Si–O–Si anti-symmetric stretch region of zeolite [47]. The absorption peaks at 400–600 cm−1 are attributed to pseudo-lattice vibrations of structural units [48]. There is a weak absorption peak at 960 cm−1 which is attributed to the anti-symmetric Ti–O–Si stretching modes of a corner-sharing tetrahedral [49,50]. It is confirmed that there is a chemical bond between TiO2 and zeolite. TiO2 particles are firmly fixed on the surface of zeolite with the force of a chemical bond, which is beneficial for the reclamation of photocatalysts.
The results of the UV–vis diffuse reflectance spectra (UV-vis DRS) of HTOP (anatase TiO2) and MZTC-2.5 are shown in Figure 6a. It is obvious that both HTOP and MZTC-2.5 could absorb the UV-light (200–400 nm) and the absorption intensity of HTOP was almost equal to that of MZTC-2.5. The absorption peaks of HTOP and MZTC-2.5 appeared at the wavelengths of 310 nm and 345 nm, respectively. The diffuse reflectance spectra of MZTC-2.5 had a slight shift to longer wavelengths compared with that of HTOP. Similar results could be observed in other research [51,52]. It is indicated that the band-gap of MZTC-2.5 was narrowed and light with lower energy could excite the photoelectron reaction, which was probably ascribed to the existing Ti–O–Si. According to the Kubelka–Munk theory, the band-gap energies of HTOP and MZTC-2.5 could be calculated by a plot of [Ahν]1/2 as a function of hν, as shown in Figure 6b. The calculated band-gap energies of HTOP and MZTC-2.5 are 3.23 eV and 3.10 eV, respectively. Compared with HTOP, the band-gap of MZTC-2.5 had a slight shift towards visible light, which indicated that more light could be used to excite the photocatalysis. Hence, a better photocatalytic performance of MZTC-2.5 could be expected due to the additional state of Ti–O–Si.

2.2. Evaluation of the Photocatalytic Efficiency

The results of the MB degradation experiment are shown in Figure 7a. In order to exclude the influence of the non-photocatalytic effects that could decrease the concentration of MB, the blank experiment was conducted. The result shows that the MB can barely be degraded by UV irradiation without a catalyst. So, the effects of photodegradation can thus be neglected in photocatalysis. The MB concentration has a slight decline with MZTC-0 added, indicating that MZ has a certain adsorption capacity, which contributes to enhance the pollutant concentration around TiO2 [11]. Obviously, the MB degradation rate increased with the amount of loaded TiO2, and MZTC-2.5 showed the highest photocatalytic activity, which could remove MB up to 93.6% within 60 min. However, when the amount of loaded TiO2 was up to 5%, the degradation rate of MZTC-5 was lower. This could be explained as the condition of low TiO2 content, more active sites of TiO2 would be exposed with more TiO2 addition, while on the condition of high TiO2 content, excess TiO2 particles would stack and agglomerate leading to a reduction of exposed active sites. The MB degradation rate of HTOP (68%) was much lower than that of MZTC-2.5 (93.6%). This is because HTOP is prone to agglomeration in water due to the large surface energy, thus leading to a serious reduction of surface area and active sites. The MB degradation rate of NZTC-2.5 was also lower than that of MZTC-2.5, which was related with the mass transfer process. In detail, the micron-sized pores of NZTC-2.5 were obstructed due to impurities, so the transfer efficiency of MB molecules was limited. The first-order reaction kinetics model was used to fit the data obtained from the degradation experiment. The fitting curves are shown in Figure 7b, which display a good linear relationship (R2 > 0.98), indicating that the photocatalytic degradation process of MB conforms to the first-order reaction kinetics. According to the fitting equation (-ln(C/C0) = k·t), the slope represents the reaction rate constant k (min−1). The degradation parameters are shown in Table 2. The reaction rate constant (k, 0.04694 min−1) of MZTC-2.5 is 2.4 times and 1.47 times higher than that of HTOP (k, 0.01959 min−1) and NZTC-2.5 (k, 0.03204 min−1), respectively. The enhanced reaction rate is attributed to the synergistic effect caused by modified zeolite and nano-TiO2. The modified zeolite/TiO2 composite provides abundant TiO2 active sites and a high concentration of pollutant, thus accelerating the photocatalysis reaction.
The results of the recycle degradation experiment of MZTC-2.5 are shown in Figure 8. The first degradation rate reached up to 93.6% for MB within 60 min. However, from the second cycle onwards, the degradation rate decreased slightly and gradually become steady. When the tests were recycled five times, the fifth degradation rate was 86.5%, which indicates the excellent recyclability of MZTC-2.5. The slight decrease in degradation rate is probably due to the occupation of TiO2 active sites by remnant MB or the reaction products.
According to the degradation experiment results, the process of the degradation of MB can be divided into several stages in this study. Firstly, a mass of MB molecules migrate to the surface of MZTC-2.5 from the aqueous environment. Because the MB molecules have an effective molecular diameter of about 0.77 nm, which is smaller than that of MZTC-2.5 with an average pore size of approximately 9.27 nm, the MB molecules could transfer to the pores of MZTC-2.5. Due to the huge specific surface area, the adsorption equilibrium was established in a short time and MB could be stored in the large internal surfaces and on the external surfaces of MZTC-2.5, so the concentration of MB around TiO2 was very high. Once the TiO2 particles were illuminated by UV light, electron (e−)–hole (h+) pairs would be generated on the surface of TiO2, which would react with OH− and the dissolved O2 in the aqueous solution in order to generate ROS such as hydroxide radicals (·OH), superoxide radicals (O2−) and hydrogen peroxide (H2O2) in different chain reactions. The MB would be oxidized into inorganic matter by hydroxide radicals (·OH) as shown in Equation (1) [53,54]:
MB + ·OH → products (CO2 + H2O + NH4+ + NO3− + SO42− + Cl−)
When the adsorbed MB were degraded by hydroxide radicals (·OH), the adsorption equilibrium was broken so that more MB molecules would be captured by MZTC-2.5 and then more MB would be photocatalytically degraded. The process of degradation is shown in Figure 9.

3. Experimental Procedure

3.1. Preparation of MZTC

A certain amount of NZ was immersed in the NaOH aqueous solution (2 mol·L−1) for 6 h with continuous stirring. After alkaline erosion, the zeolite was washed using distilled water until the pH value was 7 or 8 and subsequently calcined at 400 °C for 2 h. The preparation of TiO2 sol was carried out according to the literature [55]. A certain mass of Tetrabutyl Orthotitanate (TBOT) was added into distilled water dropwise with stirring. Nitric acid was also added to inhibit the hydrolysis. The weight ratio of TBOT, distilled water and nitric acid was 1:8:0.08. The white slurry was then heated in the water bath at 40 °C for 24 h until the sol turned light blue and transparent. Some modified zeolite (MZ) and as-prepared TiO2 sol were mixed together with stirring and then treated with ultrasonication for 0.5 h. Afterwards, the mixture was treated in a stainless steel still under negative pressure of 0.07 MPa for 5 h. Finally, the products were dried at 105 °C for 2 h and then calcined at 400 °C for 2 h to obtain the MZTC [42]. The samples were labeled as MZTC-n (n% is the weight percentage of TiO2 sol, i.e., n = 0, 0.5, 1, 2.5, 5). As a control study, the natural zeolite supported TiO2 was also fabricated and labeled as NZTC-2.5 (NZTC=natural zeolite/TiO2 composite). A certain amount of the TiO2 sol was dried at 105 °C for 2 h and then calcined at 400 °C for 2 h to obtain the TiO2 powder, namely hydrolysis TiO2 powder (HTOP). The chemical composition of NZ is shown in Table 3. The composition of all specimens are shown in Table 4.

3.2. Characterization

The phase composition of the samples was characterized by X-ray diffraction (D/max2550, RIGAKU, Tokyo, Japan) with a Cu Ka ray source (40 kV and 100 mA) at the speed of 4° min−1 between 10° and 60°. The morphology of the products was observed by a scanning electron microscope (Quanta 200F, FEI, Hillsboro, OR, USA). The surface chemical composition of the samples was analyzed with an energy dispersive spectrometer (Genesis Apollo X/XL, EDAX, Berwyn, PA, USA). The specific surface area and pore size distribution of the as-prepared material were evaluated by a BET automatic nitrogen adsorption specific surface area detector (Beishide 3H-2000PS2, BEISHIDE, Beijing, China). The chemical bond between TiO2 and zeolite was detected by Fourier transform infrared spectroscopy (EQUINOX55, BRUKER, Karlsruhe, Germany). The UV–vis diffuse reflectance spectra (DRS) were measured using a UV–VIS-NIR spectrophotometer (LAMBDA 950, PERKINELMER, Waltham, MA, USA).

3.3. Evaluation of Photocatalytic Degradation Efficiency

The photocatalytic performance of MZTC was evaluated by the MB degradation experiment. One gram of MZTC-n (n = 0, 0.5, 1, 2.5 or 5) was added into 30 mL MB aqueous solution (50 ppm), then the mixture was stirred and left in the dark for about 60 min to establish the adsorption equilibrium. Once the UV-light (125 W, 365 nm) irradiation occurred, the photocatalysis reactions started immediately. During the photocatalysis process, about 1 mL of supernatant was collected every 10 min and transferred to a quartz cuvette for the measurements of the maximum absorbance at 665 nm. According to the Lambert–Beer law, we get the relationship of C = k′A, so the degradation rate of MB was calculated using Equation (2):
C C 0 = A t A 0
where C is the concentration of MB at time t and C0 is the concentration of initial MB. At is the absorbance of the MB aqueous solution at time t and A0 is the absorbance of the initial MB aqueous solution. For comparison, 1 g NZTC-2.5 and 0.06 g HTOP were also tested. The mass of the HTOP used was equal to that of the TiO2 contained in 1 g MZTC-2.5.

4. Conclusions

(1) After the modification of alkali erosion and calcination, the modified zeolite is rough and porous, which is suitable for the sedimentation of nano-TiO2 and the diffusion of pollutants.
(2) Through the method of saturated infiltration and synthesis in situ, the modified zeolite/TiO2 composite has been synthesized. The nano-TiO2 are homogeneously dispersed in the structure of the modified zeolite at the nanoscale range. TiO2 particles are firmly bonded with zeolite with the force of the chemical bond.
(3) Due to the synergistic effect comprising the uniform distribution of TiO2 and the enhanced adsorption capacity, the MB degradation rate of MZTC-2.5 is higher than that of the equal mass of pure TiO2. The MB degradation rate increases with the content of TiO2. MZTC-2.5 performs the best in terms of degradation efficiency, which could reach up to 93.6%.
(4) After five tests, the MB degradation rate of MZTC-2.5 is still 86.5%, proving that MZTC-2.5 has good recyclability.

Author Contributions

Literature search, figures, writing, G.L.; data collection, data analysis, data interpretation, W.H.; study design, Y.H.

Funding

This research was funded by Deyang science and technology plan project, grant number 11021.

Conflicts of Interest

The authors declare no conflict of interest.

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Catalysts 09 00502 g001 550
Figure 1. X-ray diffraction patterns. (a.u. = arbitrary units).
Figure 1. X-ray diffraction patterns. (a.u. = arbitrary units).
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Catalysts 09 00502 g002a 550Catalysts 09 00502 g002b 550
Figure 2. Scanning electron microscopy (SEM) images: (a) P25; (b) HTOP; (c) NZ; (d) MZ; (e) MZTC-2.5; energy dispersive spectroscopy (EDS) results of MZTC-2.5: (f–h).
Figure 2. Scanning electron microscopy (SEM) images: (a) P25; (b) HTOP; (c) NZ; (d) MZ; (e) MZTC-2.5; energy dispersive spectroscopy (EDS) results of MZTC-2.5: (f–h).
Catalysts 09 00502 g002aCatalysts 09 00502 g002b
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Figure 3. (a) N2 adsorption–desorption isotherms of MZ and MZTC-2.5; (b) pore size distribution curves of MZ and MZTC-2.5.
Figure 3. (a) N2 adsorption–desorption isotherms of MZ and MZTC-2.5; (b) pore size distribution curves of MZ and MZTC-2.5.
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Figure 4. Models of MZ and MZTC.
Figure 4. Models of MZ and MZTC.
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Figure 5. Infrared spectrum of MZTC-2.5.
Figure 5. Infrared spectrum of MZTC-2.5.
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Figure 6. (a) UV–vis diffuse reflectance spectra; (b) Kubelka–Munk (Ahν)1/2 versus energy.
Figure 6. (a) UV–vis diffuse reflectance spectra; (b) Kubelka–Munk (Ahν)1/2 versus energy.
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Figure 7. (a) The MB degradation rate of different samples within 60 min; (b) The corresponding linear fitting curves using the first-order reaction kinetics model.
Figure 7. (a) The MB degradation rate of different samples within 60 min; (b) The corresponding linear fitting curves using the first-order reaction kinetics model.
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Figure 8. Results of the recycle degradation experiment of MZTC-2.5.
Figure 8. Results of the recycle degradation experiment of MZTC-2.5.
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Figure 9. Mechanism of the degradation of MB in aqueous solution.
Figure 9. Mechanism of the degradation of MB in aqueous solution.
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Table
Table 1. Specific surface area (S), pore volume (V) and average pore diameter (D) for MZ and MZTC-2.
Table 1. Specific surface area (S), pore volume (V) and average pore diameter (D) for MZ and MZTC-2.
SampleS (m2g−1) V (cm3g−1) D (nm)
MZ3920.2912.02
MZTC-2.52930.219.27
Table
Table 2. The parameters of the photocatalytic degradation reactions. (k = reaction rate constant; R2= goodness of fit).
Table 2. The parameters of the photocatalytic degradation reactions. (k = reaction rate constant; R2= goodness of fit).
Specimenk (min−1)R2
Blank9.74 × 10−40.98574
MZTC-08.05 × 10−40.98691
HTOP0.019590.98693
NZTC-2.50.032040.99422
MZTC-0.50.029300.99492
MZTC-10.035120.99140
MZTC-2.50.046940.98633
MZTC-50.042140.99194
Table
Table 3. The chemical composition of natural zeolite (wt%).
Table 3. The chemical composition of natural zeolite (wt%).
SiO2Al2O3Na2OCaOK2OMgOFe2O3FeOTiO2P2O5
60~7017.84.22.63.20.81.61.20.60.26
Table
Table 4. Composition of the specimens. (NZTC = natural zeolite/TiO2 composite; MZTC = modified zeolite/TiO2 composite; HTOP= hydrolysis TiO2 powder).
Table 4. Composition of the specimens. (NZTC = natural zeolite/TiO2 composite; MZTC = modified zeolite/TiO2 composite; HTOP= hydrolysis TiO2 powder).
SpecimenNZ Content/wt%MZ Content/wt%TiO2 Content/wt%
HTOP--100
NZTC-2.593.92-6.08
MZTC-0-1000
MZTC-0.5-98.721.28
MZTC-1-97.482.52
MZTC-2.5-93.926.08
MZTC-5-88.5311.47

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Liao, G.; He, W.; He, Y. Investigation of Microstructure and Photocatalytic Performance of a Modified Zeolite Supported Nanocrystal TiO2 Composite. Catalysts 2019, 9, 502. https://doi.org/10.3390/catal9060502

AMA Style

Liao G, He W, He Y. Investigation of Microstructure and Photocatalytic Performance of a Modified Zeolite Supported Nanocrystal TiO2 Composite. Catalysts. 2019; 9(6):502. https://doi.org/10.3390/catal9060502

Chicago/Turabian Style

Liao, Gang, Wei He, and Yuming He. 2019. "Investigation of Microstructure and Photocatalytic Performance of a Modified Zeolite Supported Nanocrystal TiO2 Composite" Catalysts 9, no. 6: 502. https://doi.org/10.3390/catal9060502

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