Appl. Sci. 2020, 10, x doi: FOR PEER REVIEW www .mdpi.comjournal applsci [604594]

Appl. Sci. 2020, 10, x; doi: FOR PEER REVIEW www .mdpi.com/journal/ applsci
Article 1
Reusable and Easy Separable Mesoporous TiO 2 2
Particle with High Photocatalytic Activity 3
Hendri Widiyandari 1,*, Iqbal Firdaus 2 Lusi Ernawati3, Ruri Agung Wahyuono4, Agus Purwanto5, 4
and Takashi Ogi6 5
1 Department of Physics, Faculty of Mathematics and Natural Sciences, Sebelas Maret University, 57126, 6
Indonesia ; hendriwidiyandari @staff.uns.ac.id 7
2 Department of Physics, Faculty of Mathematics and Natural Sciences, University of Lampung , 35145, 8
Indonesia ; [anonimizat] 9
3 Department of Chemical Engineering, Institut Teknologi Kalimantan, Balikpapan 76127, Indonesia ; 10
[anonimizat] 11
4 Department of Engineering Physics, Institut Teknologi Sepuluh Nopember, Surabaya 60111, Indonesia ; 12
[anonimizat] 13
5 Department of Chemical Engineering, Faculty of Engineering, Sebelas Maret University, 57126, Indonesia ; 14
[anonimizat] 15
6 Department of Chemical Engineering, Hiroshima University, 739 -8527, Japan ; ogit@hiroshima -u.ac.jp 16
* Correspondence: hendriwidiyandari @staff.uns.ac.id ; Tel.: + 62-271-669-017 (F.L.) 17
Received: date; Accepted: date; Published: date 18
Featured Application: Mesoporous TiO 2 particle has a futured application as a photocatalyst for 19
water treatment process, hydrogen generation, etc . 20
Abstract: This work report s the synthesis of reusable and easily separable mesoporous TiO 2 21
photocatalyst by a simple route of the sol -gel method u sing titanium (IV) isopropoxide and 22
polyethylene glycol (PEG) as a precursor and mesopore template, respectively. The amaranth dye's 23
degradation assesse s the photocatalytic activity of the prepared mesoporous TiO 2 catalyst under 24
simulated irradiation. The results indicate that the crystallinity of TiO 2 could be controlled by the 25
amount of PEG template and the subsequent calcination process after the sol -gel reaction. The as – 26
prepared TiO 2 particles ae characterized by a large surface area and possess a cryst alline phase of 27
anatase and rutile depending on the calcination temperature. The photocatalytic activity of 28
mesoporous TiO 2 under solar simulator irradiation is comparable to the commercial TiO 2, and 29
mesoporous TiO 2 annealed at 600°C exhibit s both easy sep aration and reusability which is 30
indispensable in industrial applications. Moreover, testing in real conditions using sunlight shows 31
that the synthesized material has an excellent photocatalytic activity, which can degrade 10 ppm 32
amaranth solutions in less than 15 minutes. The separation rate of the resultant TiO 2 is about two 33
times faster than the commercial one, while the reusability test demonstrate s that the prepared TiO 2 34
could be used repeatedly, i.e., at least four cycles. 35
Keywords: photocatalytic act ivity, TiO 2 Anatase, polyethylene glycol, reusable .) 36
37
1. Introduction 38
Environmental problems due to liquid waste become a classic problem encountered by urban 39
communities. Various technologies have been developed to overcome this problem, including the 40
Advance Oxidation Process (AOP) [1,2]. AOP utilizing semiconductor photoc atalysts is considered 41
an environmentally friendly technology utilizing hydroxyl free radicals (OH●) to degrade liquid 42
waste [1 –3]. These photocatalysts harvest solar energy to activate the oxidation and reduction 43
processes that are responsible for the rem oval of toxic organic compounds and microorganisms in 44

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liquid waste and water. A wide range of metal oxide semiconductors materials has been explored 45
and exploited as photocatalytic material, including TiO 2, WO 3, metal -doped TiO 2 and WO 3 [4–8]. 46
Nonetheless, the most widely used material is titanium dioxide ( TiO 2). 47
TiO 2 has three typical crystallographic forms, including anatase, rutile, and brookite. The widely 48
used forms for industrial purposes are the anatase and rutile [9, 10]. Some studies have found th at 49
the mixture of anatase and rutile phases is more effective than pure anatase forms [11,12]. The mixed 50
phases enable a rapid electron transfer from rutile to anatase fragment. Furthermore, the mixed 51
phases reduce the recombination of electrons (e -) and h oles (h+) pairs created upon photoexcitation, 52
thereby increasing photocatalytic activity. 53
It is generally known that the photocatalytic activities of TiO 2 depend on various parameters: 54
textural properties, morphology, crystallinity, crystallographic form, crystallite size, surface area, 55
particle size, defect sites, and surface charge [1 –3]. Textural properties particularly exert a significant 56
influence on the catalyst’s photoactivity [13,14], while surface properties also substantially determine 57
the photoca talytic activity. Thus, mesoporous TiO 2 photocatalysts have attracted much attention 58
because of their high surface area, narrow pore size distribution, and tunable pore size while 59
maintaining the crystalline framework [15,16]. Mesoporous also promotes the diffusion of reactants 60
and products, which may provide reactive sites on the surface of photocatalysts [17]. Material with 61
high surface area is one of the keys to produce photocatalyst with high photocatalytic activity. 62
Amongst various preparation methods, sol-gel synthesis is one of many viable options that can 63
produce photocatalysts with a high surface area. Moreover, this method only needs simple 64
equipment and low temperature of preparation [18]. 65
TiO 2 nanoparticle has remarkable photocatalytic activity p roperties due to the large surface area; 66
however, for large -scale water treatment applications, there is a separation problem between 67
photocatalyst material and the treated water [19]. The frequently used centrifugation method spends 68
enormous amounts of en ergy, which is not economically feasible. Thus, photocatalyst nanoparticles 69
must be immobilized, i.e., coated on a surface become a film [20]. Another solution is a magnetically 70
separable photocatalyst [21], fibrous membrane photocatalyst [22], and 3D -hydr ogel photocatalyst 71
[19]. A photocatalyst material that can be separated from the solution allows the material to be reused. 72
Instead of using TiO 2 nanoparticle, TiO 2 mesoporous with bigger particle size, but has a large surface 73
area, has a potential for pra ctical application. 74
In this work, we have developed a sol -gel synthetic route of mesoporous TiO 2 particles with 75
additional polyethylene glycol (PEG) as the organic template. The PEG was used to maintain the 76
porosity even after thermal treatments, such as c alcination [23 –29]. The PEG concentration was varied 77
to investigate the effect of PEG on the microstructural as well as physical properties. Calcination was 78
also undertaken to eliminate organic compounds and applied at different temperatures, including 79
phase transformation and crystallization temperature. The effect of calcination temperatures on the 80
microstructural and physical properties of TiO 2 is discussed and correlated with the photocatalytic 81
activity. More importantly, the mesoporous TiO 2 particles p repared in this work are easily separable 82
from the aqueous suspension and has excellent reusability and thus favourable for its industrial 83
application as photocatalyst. 84
2. Materials and Methods 85
2.1. Preparation of TiO 2 Mesoporous Particle 86
The sol -gel TiO 2 was prepared using Titanium Tetra -Isopropoxide (TTIP, Ti[OCH(CH 3)2]4, 87
Aldrich), a complexing agent of isopropanol (C 3H8O, Merck), distilled water and HNO 3 (Merck). A 88
mixture solution was prepared using 0.5 M TTIP and 7.19 g isopropanol in 60 ml of distilled water. 89
Both mixtures were stirred continuously for an hour before mixing. The 0.13 g HNO3 was added 90
dropwise to the TTIP solution under constant stirring for 2 hours to obtain a clear solution. A 91
separated solution containing 1.2 g and 3 .6 g PEG (MW: 20.000) in 20 ml of distilled water was 92
prepared and added dropwise to obtain TiO 2-1.2 and TiO 2-3.6, respectively. The total solution was 93
kept under continuous stirring for 1 hour at 70 °C. The prepared sol -gel was eventually used to obtain 94

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TiO2 powder by filtering and washing the filtrate. Calcination has been carried out at different 95
temperatures of 450 °C, 500 °C, 600 °C, and 700 °C to modify the structure and phase of TiO 2. 96
2.2. Catalyst Characterization 97
The structure of TiO 2 mesoporous pa rticle was characterized using X -ray powder diffraction 98
(XRD) Shimadzu 7000 with Cu Kα radiation (  = 1.5406 Å). The diffraction pattern was scanned at 99
the angle between 10 and 80 °. The crystallite size was estimated by applying the Scherrer equation. 100
The samples' specific surface area was determined using the N 2 physisorption test, i.e., Brunauer 101
Emmett and Teller (BET) measurement (Nova Instrument). The sample was evacuated at 300 °C 102
before the physisorption test to remove surface water and intercalated water. The samples' surface 103
morphology was characterized using Scanning Electron Microscope (JEOL JSM -6360LA) at an 104
accelerating voltage of 20 kV. UV -Vis Spectrophotometer (Shimadzu, Japan) to measure the optical 105
absorption of the pollutant mo del (amaranth dye). 106
2.3. Photodegradation Test 107
The amaranth (C 20H11N2Na 3O10S3, 90%, Sigma Aldrich, Germany) was used to evaluate the 108
photodegradation activity of mesoporous TiO 2 particles both under sunlight and solar simulator 109
irradiation (PEC -L11, Peccel l Technologies,Inc., Japan). Solar simulator was used to simulate sunlight 110
conditions at AM 1.5G (100 mW/cm2). Prior utilization, the resultant mesoporous TiO 2 particle was 111
sieved, yielding particles with a size of approximately < 74 µm. The photocatalytic reaction was 112
carried out in the pyrex glass equipped with a cooling system to maintain the reaction temperature 113
at 25 °C. Continuous agitation was conducted to provide a homogeneous concentration inside the 114
reactor. 10 ppm of amaranth was mixed with 200 m g TiO 2 in a 100 mL solution. The solution was 115
stirred in the dark for 30 min to provide saturation conditions for the adsorption of dye – 116
photocatalysts and then subjected to UV illumination for 2 h. The solution was sampled and 117
centrifuged at 6000 rpm for 1 5 min to separate the dye solution and photocatalyst. The dye 118
degradation was followed by measuring the dye concentration at room temperature using a UV -Vis 119
spectrophotometer (Shimadzu, Japan). The absorbance was evaluated in the wavelength range of 400 120
to 700 nm as the amaranth peak was found at 520 nm. Photocatalyst material used for re -use tests 121
before being used is first heated at a temperature of 300 °C for 1 hour to remove the organic material 122
attached to the surface of the material. 123
2.4. Separation R ate Determination 124
An aqueous suspension of TiO 2 (size < 74 mm) was prepared, and the resulting suspension was 125
left for 9 hours. The changes in suspension height were recorded every hour. The separation rate 126
between the sol -gel prepared TiO 2, and the commer cial TiO 2 (Merck) was determined by calculating 127
the slope of a linear plot of the suspension height vs. time. 128
3. Result and Discussion 129
3.1. Effect of PEG Addition 130
Figure 1 shows the diffraction pattern of TiO 2 prepared using different amounts of PEG and 131
calcined at 500 °C. The corresponding microstructural properties are summarized in Table 1. The 132
diffraction pattern indicates that the resultant TiO 2 shows a characteristic of the anatase phase (JCPDS 133
No. 21 -1272). Typically, PEG incorporation in nanoparticle synthesis improves the hydrophilicity as 134
well as the porosity and further reduces the crystallite size [30,31]. It appears that the addition of PEG 135
leads to an increase of diffraction maximum (011) and a nar rower FWHM, which means the crystallite 136
size is increased. The shift of (011) maximum compared to the standard (011) peak position indicates 137
higher lattice strain and dislocation density in TiO 2-0 and TiO 2-3.6. Both structures show comparable 138
dislocation d ensity of (8.96 – 9.85)×105 lines ‧m-2 that should yield high defect concentration 139
advantageous in photocatalysis. 140

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141
Figure 1. XRD patterns of mesoporous TiO 2 particle with different PEG addition . 142
143
144
Figure 2. SEM images of meporous TiO 2 particle prepared using different PEG addition: (a) 0 g, (b) 145
1.2 g, and (c) 3.6 g. 146
147
Figure 2 displays the morphology of different TiO 2 particles. All morphology shows a fractal 148
surface of TiO 2 particles, but the surface charac teristic indicates a different pore structure. The 149
addition of PEG modifies the morphological structure of TiO 2 to be rougher and opens a more 150
significant number of small and large pores, which should yield a larger surface area [25]. This 151
structural alter ation upon PEG addition into the sol -gel synthesis of TiO 2 can be understood as PEG 152
tends to interact with the hydroxyl groups of TiO 2, leading to the formation of random and complex 153
3D structure. As also found in literature [30 –32], the PEG assisted TiO 2 synthesis resulted in 154
mesoporous particles upon evaporation. 155
Table 1 summarizes the surface properties of TiO 2 upon the addition of different amounts of 156
PEG. Consistent with the microscopic evaluation, the addition of PEG leads to an increase in the 157
spec ific surface area (SSA) of TiO 2. The TiO 2-3.6 has the largest specific surface area of 73.6 m2‧g-1. The 158
addition of PEG does not show any clear trend on the pore size of TiO 2. Nonetheless, all samples 159
exhibit mesopore character, i.e., pore size smaller than 50 nm. Considering the favorable surface 160
characteristic and the higher dislocation density in TiO 2-3.6, this sample will be subjected to further 161
study of different calcinat ion ( vide infra ). 162

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163
Table 1 . Crystallite size ( D) and dislocation density (δ) determined from XRD, and the specific surface 164
area (SSA) as well as pore size of TiO 2 determined from BET and BJH analysis. 165
166
Sample Name PEG
[g] D
[nm] δ
[105×lines/m2] SSA
[m2/g] Pore size
[nm]
TiO 2-0 0 8.21 9.85 69.254 13.3
TiO 2-1.2 1.2 11.08 8.14 67.684 15.4
TiO 2-3.6 3.6 10.56 8.96 73.621 10.9
167
3.2. Effect of Calcination Temperature 168
The microstructural properties of TiO 2 upon calcination at different temperatures was assessed 169
by XRD (Figure 3). The results show that the diffraction patterns of TiO 2 evolve at different 170
temperatures indicating an alteration of the TiO 2 crystal structure. The TiO2 -450 and TiO 2-500 have 171
diffr action patterns corresponding to the anatase phase of TiO 2 with (011) preferred orientation. 172
Meanwhile, TiO 2-600 and TiO 2-700 exhibit a mixed character of the anatase (011) and rutile (110) 173
crystalline phases. The weight percent of anatase phase (FA) was e stimated using equation (1): 174
𝐹𝐴 = 𝐼𝐴 / 𝐼0 = 0.884 𝐼𝐴 / (0.884 𝐼𝐴 + 𝐼𝑅 ) (1)
175
where 𝐹𝐴 is anatase weight percent, 𝐼0 is the total (011) and (110) peak intensity, 𝐼𝐴 , and 𝐼𝑅 are 176
diffraction peak intensities from anatase (011) and rutile (110), respectively. The correction factor of 177
0.884 was measured using known mixtures of pure phases [25]. The calculated mass fraction of the 178
phases is presented in Table 2. 179
Increasing calcination temperature from 450 to 600 °C causes an increase in peak intensity (011). 180
TiO2 -600 contains a fraction of anatase (60.7%) and rutile phases (39.3%), which is reasonable since 181
the phase transformation temperature (anatase to rutile) occurs at above 500 °C and crystallization of 182
rutile phase occurs at ca 600 °C [33]. This phase transformation is due to the re -arranged Ti –O 183
coordination bonds upon calcination [30,31]. Therefore, it was evident that the (110) rutile phase has 184
a higher in tensity than (011) anatase phase upon calcination at 700 °C, which also reflects that the 185
fraction of rutile is higher than that of anatase. Furthermore, increasing calcination temperatures 186
affects the crystal growth, in which crystallinity of TiO 2 is enha nced at a higher temperature. 187
However, it should be noted that calcination at a higher temperature also substantially vanishes the 188
number of defect sites manifested by the dislocation density (Table 2) [34], i.e., the catalytically active 189
sites for photode gradation of organic compound. 190
191
Figure 3. XRD patterns of mesoporous TiO 2 particles annealed at different temperatures. 192

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193
Table 2 . Microstructural and physical properties of mesoporous TiO 2 particles prepared at different 194
calcination temperatures. 195
Sample
Name Fraction [%] D [nm] δ [105×
lines/m2] SSA
[m2/g] Pore size
[nm] Anatase Rutile Anatase Rutile
TiO 2-450 100 – 8.5 – 14.02 94.25 9.70
TiO 2-500 100 – 11.3 – 7.87 84.52 9.74
TiO 2-600 60.68 39.32 27.3 35.5 1.35 34.36 7.80
TiO 2-700 30.68 69.32 34.4 50.2 0.85 20.04 9.44
196
Figure 4 shows the N 2 adsorption/desorption isotherms and the pore size distribution of 197
synthesized TiO 2. According to IUPAC, all samples display type IV physisorption isotherm, which is 198
a characteristic of mesoporous material irrespective of calcination temperature. This result indicates 199
that the calcination process did not significantly change the pore str ucture of TiO 2 as the mesoporous 200
character is maintained. It should be noted that the hysteresis loop (H) at higher relative pressure is 201
differently marked for TiO 2-700. While TiO 2-450 – TiO 2-600 exhibit H1 character of a cylindrical 202
porous network, TiO 2-700 shows an H3 character that reflects a non -rigid aggregate of plate -like 203
particles with slit -like pores. The surface properties, including the specific surface area and the pore 204
size of TiO2, are summarized in Table 2. It appears that the specific surface area decreases when the 205
calcination temperature increases. TiO 2-450 has the highest specific surface area, and the lowest one 206
is TiO2 -700. The pore size in the sample tends to increase with an increase in temperature. This 207
increase in pore size causes a significant decrease in specific surface area, particularly in TiO 2-600 and 208
TiO 2-700. Moreover, increasing of calcination temperature causes porous networks coalescence, thus 209
lowering the sur face area as can be seen from BET measurements [30,31]. 210
211
212
Figure 4. N2 adsorption –desorption isotherms curves: (a) TiO 2-450, (b) TiO 2-500, (c) TiO 2-600, 213
and (d) TiO 2-700. Inset shows the BJH pore distribution. 214

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215
3.3. Photocatalytic activity 216
The photocataly tic activity of different mesoporous TiO 2 particles is investigated through the 217
photodegradation test of amaranth, i.e., an AZO derived organic compound. Figure 5 shows the 218
photocatalytic activity of TiO 2, which were annealed at different temperatures, under the sunlight 219
irradiation. Different calcination temperatures cause differences in the photocatalytic activity of the 220
sample. TiO 2-700 exhibits the slowest degradation of amaranth, which might be due to the significant 221
rutile phase content that is not photoactive. Meanwhile, TiO 2-500 and TiO 2-600 show high 222
photocatalytic activity due to the large fraction of the anatase phase. A large specific surface area of 223
TiO 2-500 has led to the highest photocatalyti c activity among the investigated samples. A quantitative 224
measure of different photocatalytic activity is assessed through the kinetic study. In this work, the 225
first-order kinetics concerning dye concentration was used to fit the data using Eq uation (2): 226
𝐶 = 𝐶0𝑒𝑥𝑝(−𝑘 𝑡) (2)
C0 is the initial amaranth concentration, C is the amaranth concentration at the time t, and k is the 227
first-order rate constant [23]. The value of k was used as a measure of the photocatalytic activity. 228
229
230
Figure 5. Photodegradation of amaranth under sunlight irradiation using mesoporous TiO2 231
particles annealed at different temperatures. 232
233
234
Figure 6. Photocatalytic degradation of amaranth using commercial TiO 2, TiO 2-500, and TiO 2-600 235
under solar simulator. The sample at before and after degradation process (inset) . 236
237

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Figure 6 shows the photocatalytic activity of TiO 2-500 and TiO 2-600 compared with the 238
commercial TiO 2 (Merck, 95% anatase, and 5% rutile) under solar simulator irradiation. The TiO 2- 239
comm exhibits rapid degradation in the first 30 min, which might be due to efficient diffusion and 240
amaranth absorption on the large s urface area of TiO 2-comm. Nonetheless, both the synthesized 241
samples and the commercial one enables photodegradation of amaranth solution into a clear solution 242
in approximately 70 min. The synthesized sample, particularly with larger aggregate size, shows t he 243
same performance as good as the commercial one. A quantitative assessment is reflected by the first – 244
order rate constant ( k) for TiO 2-comm, TiO 2-500, and TiO 2-600, which is found 0.035, 0.059, 0.049 min- 245
1, respectively. Hence, TiO 2-500 and TiO 2-600 have better photocatalytic activity than the commercial 246
one. 247
Overall, TiO 2-500 with 100% anatase content shows the highest photocatalytic activity, which 248
accumulates some virtues: High crystallinity of anatase TiO 2 facilitates rapid charge mobility [37]. 249
Consi derably large surface area (84.523 m2‧g-1) and high dislocation density provide more surface – 250
active sites for photodegradation, and the submicron aggregation promotes light -harvesting 251
enhancement by elastic scattering of the incident light [35, 36]. Interestingly, the photocatalytic 252
activity TiO 2-600 remains quite high despite its smaller specific surface area (34.357 m2‧g-1), which can 253
be ascribed to the staggered band alignment that may exist between anatase and rutile (type -II) in 254
TiO 2-600 [36 ], in which anatase is characterized with the higher electron affinity. This anatase -rutile 255
band alignment paves the efficient separation of photo -excited charge carriers between the anatase 256
and rutile phase, and the recombination reaction is hindered by l owered driving force (ΔG) between 257
the hole in the valence band and excited electron in the trapped state of the conduction band 258
[11,12,37]. The long -lived charge -separated states are known to be the key to the high catalytic activity 259
of TiO2 producing OH● radical in the valence band, i.e., a strong oxidant responsible for the cleavage 260
of azo (–N=N–) bonds [38]. Further loss channel of photocatalytic activity might root from the large 261
aggregates in TiO 2-600, leading to randomly scattered lights that are no l onger all in phase [39], and 262
hence, destructive interference might occur in any directions canceling out the light -harvesting 263
process. 264
3.4. Reusability and separation test of mesoporous TiO 2 particle 265
Following the previous discussion, TiO 2-600 shows the mo st photocatalytic active character, and 266
thus this sample was further subjected to reusability/recyclability test. The photocatalytic activity of 267
TiO 2-600 during the reusability test is shown in Figure 7. The first -order rate constants (k) of the first, 268
second, third, and forth measurements are 0.0238, 0.0543, 0.0418, and 0.0402 min-1, respectively. It 269
shows that after the repetition of the first measurement, the value of k even increases quite 270
significantly, and only after the repetition of the second and t hird measurements, the value of k 271
decreases but is still better than the first measurement. After three repetitions, the decrease in rate 272
constant is found by about 23%. It can be deduced that the mesoporous TiO 2 synthesized here 273
presents a promising reusa ble performance. 274
275
Fig 7 . Photocatalytic activity of mesoporous TiO 2-600 for reusability test. 276

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277
Fig 8 . Separation process of mesoporous TiO 2 particles in aqueous suspension. 278
279
Furthermore, it should be considered that the mesoporous TiO 2 photocatalyst should be easily 280
separable from the photo -decolored wastewater in its application. Hence, the photocatalyst loss due 281
to wastewater discharge can be prevented, and the photocatalyst can be recycled. It was the same as 282
the photocatalytic activity test. Prior utilization, the resultant mesoporous TiO 2 particle was sieved, 283
yielding particles with a size of approximately < 74 µm. Figure 8 shows the separation rate of 284
mesoporous TiO 2 particles in aqueous suspension. Compared to commercial TiO2 , TiO2 -500 and 285
TiO 2-600 show better separation ability. TiO 2-600 has the highest separation rate as high as 0.87 cm ‧h- 286
1 while the commercial TiO 2 and TiO 2-500 exhibit separation rate of 0.44 and 0.75 cm‧h-1, respectively. 287
The highest separation rate of TiO 2-600 might stem from the higher density (compared to TiO 2-500) 288
due to the presence of ~40% of the rutile phase. 289
4. Conclusions 290
Various mesoporous TiO 2 particle has been successfully prepared using sol -gel method 291
exhibiting high -performance photocatalytic activity and easy separation of the photocatalyst. The 292
addition of PEG during the synthesis enhances the surface area of TiO 2, which is reflected by th e 293
largest specific surface area in TiO 2-3.6. Calcination at different temperatures causes the different 294
formation of TiO 2 phases: calcination at 600 and 700 șC induces the formation of the rutile phase, 295
which amounts to 40 and 70% from the total mass of TiO2, respectively. Amongst the investigated 296
structure, TiO 2-500 shows the highest photocatalytic activity due to the photoactive characteristics of 297
the anatase phase. Nonetheless, TiO 2-600 shows comparably high photocatalytic activity due to the 298
mixture pha ses with a more significant fraction of the anatase phase. Both outperform the 299
photocatalytic activity of commercial TiO 2. The synthesis route developed here yields mesoporous 300
TiO 2 particles with better photocatalytic activity and separation ability than c ommercial TiO 2. 301
Author Contributions: The contribution s of each author are as follows: Conceptualization, H.W .; Methodology, 302
H.W. and I.F. ; Validation, H.W ., and T.O.; Formal Analysis, A.P.; Investigation, I.F.; Resources, A.P.; Data 303
Curation, H.W .; Writing – Original Draft Preparation, H.W .; Writing – Review & Editing, I.F.; L.E. R.A.W.; T.O .; 304
Visualization, A.S.; Supervision, H.W.; Project Administration, H.W .; Funding Acquisition, H.W . and A.P. 305
Funding: This work was funded by Sebelas Maret University under the program for publication grants with 306
decree number: L66/UN27.21/2020. 307
Acknowledgments: The authors gratefully acknowledge the financial support from Sebelas Maret University 308
Indonesia. 309
Conflicts of Interest: The authors declare no competing financial interest or personal relationships that could 310
have appeared to influence the work reported in this paper. 311
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