Enhanced Degradation of Reactive Black 5 from Aqueous Solution over TiO2 Nanoparticles under UV Light Irradiation: Optimization, Experimental & Theoretical Approaches

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 3, Pages: 1232-1241

J. Environ. Treat. Tech.

ISSN: 2309-1185

Journal web link: http://www.jett.dormaj.com

https://doi.org/10.47277/8(3)1241

Enhanced Degradation of Reactive Black 5 from

Aqueous Solution over TiO Nanoparticles under

UV Light Irradiation: Optimization, Experimental

Theoretical Approaches

2 3

Sabah Shiri , Mohsen Mehdipour Rabori , Zeinab Gholami , Zeinab Rahmati , Moayed

Adiban *, Mansour Sarafraz

Department of Chemistry. Payame Noor University. P.O. Box 19395-4697, Tehran, Iran

Environmental Health Engineering Research Center, Kerman University of Medical Sciences, Kerman, Iran and Department of Environmental Health,

School of Public Health, Kerman University of Medical Sciences, Kerman, Iran

Student Research Committee, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran

Department of Environmental Health Engineering, School of Public Health, Ilam University of Medical Science, Ilam, Iran

Department of Environmental Health Engineering, School of Public Health, Ilam University of Medical Science, Ilam, Iran.

Student Research Committee, School of Public Health and Safety, Shahid Beheshti University of Medical Sciences, Tehran, Iran

Received: 06/01/2020

Accepted: 13/04/2020

Published: 20/09/2020

Abstract

In this study, the elimination of dye from contaminated water was considered by the photocatalytic process with TiO2. The effects

of operational parameters like TiO dosage, initial dye concentration, pH, contact time and temperature on the rate of dye decomposition

are studied. TiO2 nanoparticles were characterized by XRD, FESEM, and FTIR. The Response Surface Methodology was carried out to

investigate the composition effect of input independent factors and removal efficiency (one dependent output response). The F-value

(

315.9), P-value (2.2 × 10−16), multiple R (0.9858), adjusted R (0.9827), and lack of fit (0.494) show that the reduced second-order

model is greatly significant for dye removal by TiO nanoparticles. The efficacy of the process at the optimum operating conditions,

pH=11, TiO dose (0.7 g/l), reaction time (67.5 minutes), Temperature (40 ℃), and initial dye concentration (55 mg/l) was 86.6%. By

using regression coefficients derived from the model and the Solver “Add-ins”, higher removal efficiency was accounted to be 90%.

The results showed that the TiO nanoparticles under UV light irradiation are very proper for reducing the concentration of pollutants in

textile wastewater effluent.

Keywords: TiO

, Photocatalytic degradation, Reactive black 5, Optimization, UV light

Introduction¹

chemical and biological methods (10). Because of the color

stability against biodegradation, often for the removal of dyes

have been used physical and chemical methods such as

coagulation, flocculation, adsorption, chemical oxidation, and

membrane processes. Often decomposition of materials via

conventional treatment processes mayhap difficult. Therefore,

it is essential to use more efficient treatment processes for

demolition of these contaminants (11-14). Among the various

wastewater treatment technologies, some systems such as

advanced oxidation processes (AOPs) due to the production of

very passive and oxidizing free radicals, have gained much

attention. (15-17). In general, among AOPs the semiconductor

photocatalysis is one of the most efficient destructive

technologies for the complete elimination and full

mineralization of undesirable organic pollutants (18-22).

Annually about 70 tons of colors are produced worldwide

1). Dyes, have a complex molecular structure and are often

(

toxic, carcinogenic (production of amine groups in the

anaerobic dec omposition), mutagenic, non-biodegradable and

consistent (2, 3). The use of dye in the textile, leather, paper,

ceramics, cosmetics, ink and plastic industries and the entry

effluents of these industries in water resources, is a major

environmental problem (4, 5). Dye sewage and other effluents

from these industries create several problems in terms of

operation in the wastewater purification (6). Removal of dye

from wastewater is often more important than the removal of

other organic compounds because the presence of small

amounts of dyes (below 1 ppm) is obviously v isible and leaves

a significant impact on the water bodies (7, 8). Discharge of

colored wastewaters to the environment are leading

eutrophication, interference in the ecology, affecting the

intensity of photosynthesis of aquatic plants and algae (9). For

dye removal from wastewater can be used as physical,

Titanium dioxide (TiO ) as a semiconductor photocatalyst due

to high oxidation power, photochemical stability, large surface

area to volume ratio, low toxicity and low cost, are widely used

as catalysts in photocatalysts reactions (23-27). To survey the

Correponding author: (a) Moayed Adiban, Department of Environmental Health Engineering, School of Public Health, Ilam

University of Medical Science, Ilam, Iran. E-mail: adiban-m @medilam.ac.ir. (b) Mansour Sarafraz, Student Research Committee,

School of Public Health and Safety, Shahid Beheshti University of Medical Sciences, Tehran, Iran. E-mail:

mansour.sarafraz@yahoo.com

1232

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 3, Pages: 1232-1241

effects of various parameters, the interactions of the

experimental variables and reduce number of required

experiments was used the statistical RSM technique (28). The

RSM is a statistical method that was used for experimental

design to assig the amounts of process factors, experiential

modeling to estimate the relationship among factors and

responses and optimization of the operating conditions in the

independent variables (29). The morphology and structure of

0 t

where C is the initial dye concentration and C , is the

concentration of dye at intervals of the irradiation time. Surface

morphology and characteristics of P-25 TiO nanoparticles

were subjected by using XRD, FESEM and FTIR technology.

X-ray diffraction patterns of the samples were done by an X'

Pert Pro (PerkinElmer, Netherland) diffractometer, with Cu K훼

radiation (λ =1.54060 å), Generator settings = 40 kV, 40 mA

and the 2θ range from 10 to 80°. The average dimension (D) of

particles was calculated based on the diffraction of peak

broadening using the Debye–Scherrer’s Eq 2 (32):

the nanocrystalline TiO were determined by XRD, FESEM

and FTIR. The effect of some parameters such as temperature,

catalyst dosage, the concentration of the dye and time were

푘λ

investigated. The aims of this study were characterized by TiO

퐷 =

(2)

훽푐표푠휃

nanoparticles, investigation of photo-degradation efficiency of

Reactive Black 5 dyes, and optimization of main operational

factors such as TiO2 dosage, solution pH, dye concentration,

time and temperature by RSM. The innovations of this study

were to investigate the effect of the Tio2 / UV process for the

first time on the destruction of dyes with more complex

structures such as Reactive black 5.

where λ is the X-ray wavelength of the Cu Kα radiation (nm),

ꢂ is the peak width of the diffraction peak profile at half the

maximum height, which results from the small crystallite size

(

radians), and K is a coefficient related to a crystalline shape

which is normally equal to 0.9. The morphological features and

surface characteristics of TiO were investigated using a Field

Emission Scanning Electron Microscopy (FESEM) unit

MIRA3, TE-SCAN, Czechoslovakia). Fourier-transform

Materials and methods

(

.1 Materials

infrared spectroscopy (FTIR), is another characterization

technique was obtained using (Spectrum Tow PerkinElmer,

USA). Statistical analysis also was carried out by using the

software R.

De-ionized water is used to prepare all of the chemicals and

standard solutions. Nanoparticles of P-25 TiO (mainly in

anatase form), with an average particle size less than 30 nm, the

specific surface area (BET) of 50±15 m /g and purity greater

than 99.5% from Degussa (Germany) was used as the photo-

catalyst without further treatment. The reactive Black-5 dye

4 5 19 6

with the chemical structure C26H21Na N O S and a molecular

weight of 1029.88 g/mol as the sorbate in this study was

provided from Alvan Sabet in Iran. To immobilization of TiO

on Borosilicate glass plates (150mm × 150mm), commercially

available Titanium powder such as peroxide P25 mixed with a

solvent. Then coating was done by pipetting methods. In

pipetting the substrate was left to dry until most of the solvent

evaporated. After sintering at high temperature (400-600 °C)

the film will adhere to the substrate (30). The distance between

the UV lamps and TiO films were 1.5 cm.

.2 Photocatalytic experiments

The reactor used for photocatalytic oxidation of RB-5 dye

by UV/TiO is shown in Figure 1. This reactor consists of two

outer and inner parts, which A UV-lamp with 128 W medium-

pressure, 220 V and maximum wavelength at 247.3 nm as the

radiation source is placed in the inner part. The outer portion of

the reactor should be contained 2 L solution for keeping the

solution at 25 ±2 °퐶 . All irradiation experiments of dye

solution were performed by stirring 1000 ml of dye solution

Figure 1: Schematic diagram of the experimental photoreactor: (1)

reaction chamber, (2) outlet chamber, (3 cooling water inlet, (4) LED

lamp, (5) cooling water outlet, (6) quartz tube, (7) nano particles, (8)

sampling port, (9) magnet

with immobilized TiO and during the experiment, the solution

in the reactor was constantly stirred. After preparing the Stock

solution (1000 mg/L) of RB-5, photo-degradation dye

experiments of dye were conducted in a batch reactor by using

evaluation of the effect of pH (2 to 11), initial dye

2.3 Experimental Design with Response surface method

(RSM)

RSM is an efﬁcient statistical tool that was employed in the

data analysis, statistical design of the experiments, and

optimizing the operating conditions in independent variables

(33). In RSM two designs have been used, which include: Box

Behnken Design (BBD) and Central Composite Design (CCD).

In this study, numbers of experiments were carried out

according to a CCD for predicting and modeling the

complicated relations between input-independent factors

concentrations (10 to 100 mg L ), contact time (15 to 120

minutes), TiO

dose (0.2 to 1.2 g L ) and temperature (20 to 60

°퐶). According to five variables pH, dye concentration, contact

time, TiO

dose and temperature, to do the tests were

determined 62 runs by using the software R. Dye concentration

for the samples were performed by spectrophotometer

(DR5000, HACH LANGE, USA) according to standard

method at a wavelength of 598 nm (31). For each experiment,

the dye removal percentage (R%) was calculated using Eq. (1):

(pH(X

dose(X

2 3 2

), initial dye concentration(X ), reaction time(X ), TiO

), and temperature(X ) ) and determining the dye

removal efﬁciency(Y) under the optimum operational

conditions (34). The real values of the independent variables

that were used to the experimental design are presented in Table

ꢀ

0−ꢀ푡

푅 =

× 1ꢁꢁ

(1)

ꢀ

1233

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 3, Pages: 1232-1241

Table 1: Coded values of independent variables used for

experimental design

changes were noticed in the surface morphology of the TiO

nanoparticles (Fig. 3C).

Coded level

Variable

-1

values

6.5

50.7

67.5

1.2

120

TiO

(gr L )

0.2

Time (min)

Temp (°퐶)

Conc. RB

(mg L )

100

The Independent variables were varied over five levels as -

, 0, and 1, respectively at the determined ranges based on a set

of preliminary experiments. The experimental design was

conducted using R software for Windows (version 3.0.3:6

March 2014). The total number of experiments according to Eq.

(3) were conducted for the five factors.

Figure 2: XRD pattern of TiO nanoparticles

No: of Experiments = 2 + 2k + 20

(3)

Energy-dispersive X-ray spectroscopy (EDS) is an

analytical technique that performed for the elemental analysis

Totally, 62 runs were designed using a 32 full factorial (the

base design), 10 axial points and 20 replicates in the center

point (35).

of a sample. The EDS spectra of the TiO nanoparticles, before

(B) and after (D) of dye removal in order to survey their

localized elemental information are shown in Fig 3B. Oxygen

A quadratic model as Eq. (4) was used to express the interaction

and Titania are the elements throughout the surface of the TiO

nanoparticles before removing the dye with weight percentages

of 43.1 and 56.9 respectively. Therefore the existence of TiO

was confirmed. After removing the dye O, Ti, C, Na, S, and N

are the elements throughout the surface of the TiO

nanoparticles with weight percentages of 43.6, 42.0, 14.4, 0.1,

.0 and 0.0%, respectively. So after removing the dye wit h TiO

nanoparticles, these elements are added in Fig. 3D (40, 41). To

control frequency changes in the functional group of the

photocatalyst and in order to investigate the surface

between (Y) and (X

, X

and X ):

훾 = 퐵 + ∑^푘퐵 푋 + ∑ 퐵 푋 + ∑

퐾

ꢆ

푘−ꢅ

푘

∑

퐵 푋 푋 + C

푖ꢄꢅ 푗ꢄꢅ 퐼퐽 퐼 퐽

ꢃ

푖ꢄꢅ

푖

퐼

퐼ꢄꢅ 푖푖

푖

(4)

0 i

where B is the intercept value, B , Bii, and Bij refer to the

regression coefficient for linear, second- order, and interactive

effects respectively, X and X are the independent variables,

and C denotes the error of prediction (36-38).

characteristics of the TiO nanoparticles before and after

degradation of reactive black 5 dye, was considered the by

using Fourier transform infrared spectroscopy (FTIR) spectra

Results and discussion

nanoparticles

.1 Characterization of the TiO

Physical, chemical and morphological properties of the

nanoparticles were specified by means of various

in the range of 400-4000 cm (Figures 4A and B). The FTIR

spectrum of TiO nanoparticles before the degradation of dye

illustrates that the peak positions are at 3390, 1631, 792 cm .

TiO

techniques including X-ray powder diffraction (XRD),

scanning electron microscopy (FESEM) and Fourier transform

infrared spectroscopy (FTIR). To evaluate the structure, nature

and size of TiO crystalline phases was first performed XRD

analysis as presented in Fig. 2. The XRD analysis illustrates the

diffraction pattern and the mineralogical composition of the

The degradation band at ∼3390 cm was the characteristic

peak of alcohol and phenol groups due to the symmetric

stretching vibration of OH. The intense broad peak at

-1

1631cm is assigned in the bending vibration of the C=O

-1

∼

bond. Furthermore, the small peak at ∼792 cm can be

allocated to the bending vibration of the N–H bond. The FTIR

TiO nanoparticles. According to the Debye– Scherrer formula,

spectrum of TiO nanoparticles after removal of dye shows the

the average crystallite size based on the half-width of the most

intense peak (101) was estimated 30 nm, suggesting an

achievement to nanoscale crystals. In investigate of Figure 1,

can observe several Titania crystalline peaks for sample at 2θ =

-1

peak at 3388, 1628 and 783 cm . The bond at 3388 specifies

OH of alcohol and phenol groups, 1628 shows C –H of amide

group and 783 illustrates N–H of Amine group (42-44).

5.4(101), 37.9(004), 48.0(200), 54.5(211), 62.6(204),

9.5(116) and 75.2(118) [JCPDS No. 71 -1167 were a =

.786Å and c = 9.507Å] which indicates the existence of the

.2 Quadratic models for degradation photocatalytic of dye

via the TiO nanoparticles

To survey the individual and combined effects of variables

on dye removal efficiency, degradation experiments were

carried out at the specified combinations of the physical

parameters. The CCD design matrix was done to evaluate the

contribution of five influential factors including pH, TiO

dosage, time, temperature and dye concentration. The

experimental design of 62 runs along with the experimental and

anatase phase (39). Field emission scanning electron

microscopy, affords topographical and fundamental

information with virtually unlimited depth of field. The

FESEM images of the TiO

C) of degradation process are presented in Fig 3. As observed

in Fig. 3A, nanoparticles are spherical and scattered in different

sizes (20–60 nm). The surface of this TiO nanoparticles shows

nanoparticles before (A) and after

(

the predicted data for the removal of dye by TiO nanoparticles

irregular texture with finer particle size. Further, there are holes

between particles that show the porous structure of this

material. In some places the nanoparticles are compact in mass,

but in general, optimum dispersion of particles in the surface is

observed. After of the degradation process no noticeable

in the CCD experimental design are shown in Table 2. To

identify the optimum conditions, the RSM results need to be

studied along the optimization process (45).

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Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 3, Pages: 1232-1241

Figure 3: FE-SEM image and EDS spectrum of TiO nanoparticles before (A, B), and after (C, D) of dye removal

From Table 2, it can be seen that the dye removal values

are between 26.40% (Run 15) and 86.60% (Run 54). Moreover,

the lowest dye removal efficiency has been understood in runs

numbers 12, 15, 28, 30, 31, 38 and 39, that the main reasons for

decreasing removal, can be lower pH level and/or lower TiO

dosage. When the TiO dose and pH level are low, e.g. run 12,

the synergistic effect was very signiﬁcant and the dye removal

efﬁciency reduced intensity. According to the Table 2, the time

and temperature have low significant effects on dye removal

with TiO

nanoparticles (run numbers of 12, 15 and 38). Run

4 was obvious as optimum condition, because it indicated the

highest removal efﬁciency, and also the pH is a very

fundamental parameter in water treatment plants. However, the

pH, TiO dosage and dye concentration were appropriate as

optimum conditions. The pH in acidic range may induce serious

operational difﬁculties in water treatment processes. So,

economically the conditions for run 54 with pH 11, Initial dye

Figure 4: FT-IR spectra of TiO nanoparticles before (A), and after

B) degradation of dye

(

−1

concentration of 55 mg L , Time of 67.5 min, Temperature of

Dye removal efﬁciency predicted by the model is shown in

the Table 2. When the response predicted by the model and

experimental data acquired in the laboratory have a correlate

linearly, the model is dependable (46). The equations of the

quadratic model, for both coded and uncoded values of the

parameters, are presented at Eqs.4 and 5, respectively.

Therefore, these models can be used for prediction and

optimization (47-49).

−1

dosage of 0.7 g L are the better runs.

0 ℃ and TiO

.3 Development of regression model equation and model

analysis

The reduced quadratic model was generated by multiple

regression analysis on the experimental data, and are shown in

Table 3. According to the table 3, it is observable that the pH

(

2 2 3

), TiO dosage (X ) and time (X ) are signiﬁcant (p-values <

.05), so three terms available in Table 3 could influence the

model formulation. In this table can be seen that pH (X ), TiO

and 푋 have synergistic

훾 ꢇ푦푒ꢄꢅꢃ.74ꢈ4.343ꢉ ꢈ39.84ꢉ −ꢃ.ꢅꢆꢃ4ꢉ ꢈꢃ.ꢆ68ꢅꢉ ꢈꢃ.497ꢉ ꢉ

ꢊ ꢋ

ꢊ

ꢋ

ꢌ

ꢍ

ꢋ

ꢃ.ꢃ389ꢅꢉꢋꢉꢍꢈꢃ.ꢃꢃꢃ7ꢅ4ꢉꢌꢉꢎ−ꢆꢆ.ꢆ7ꢉꢋ ꢈꢃ.ꢃꢃꢃ8ꢅꢆꢉꢌ −ꢃ.ꢃꢃꢆꢆ8ꢉ

ꢍ

−

ꢆ

2 3 1 2 3 4

dosage (X ), time (X ), X :X , X :X

effect on the response prediction by the model, while X

and 푋 have antagonistic effect.

ꢆ

(4)

, 푋_ꢆ

ꢆ

1235

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 3, Pages: 1232-1241

훾ꢇ푦푒ꢄ6ꢃ.98ꢃ65ꢈꢆꢅ.ꢅꢃ893ꢉ ꢈ4.87979ꢉ ꢈꢃ.93ꢆꢆ5ꢉ ꢈꢅ.ꢅꢅ835ꢉ ꢉ −ꢃ.8754ꢃꢉ ꢉ

ꢋ ꢍ

fit value parameter reflected the variation of response around

the fitted model; this parameter should be insignificant if the

model fits data well (51). According to the ANOVA analysis,

the higher F-value of 315.9 with a p-value lower than 0.0001

as shown in Table 4 indicates that the second-order polynomial

model is statistically signiﬁcant, thus the model 652.17 and

65.83 respectively, that shows the model and the individual

coefﬁcients of the model are more signiﬁcant. The lack of ﬁt

value of the model available in Table 4, i.e. 0.494, indicates the

signiﬁcant correlation between factors and dye removal as a

response.

ꢊ

ꢋ

ꢌ

ꢊ

ꢋ

ꢈꢃ.75ꢃꢅꢅꢉꢌꢉꢎ−5.56679ꢉꢋ ꢈꢆ.ꢆ3775ꢉꢌ −4.6ꢅꢆꢆ5ꢉ

ꢍ

(5)

The model adequacy can be made clear from ANOVA

analysis; R and R adj are presented in Table 4. The ANOVA

analysis is a statistical technique that in this technique,

statistical significance and accuracy of the models can be

predicted via high F, low p-value, correlation coefficient (R),

and the results of lack of fit test (50). Also if p-value less than

.05 shows the model terms are significant and the values

greater than 0.10 indicate they are not significant. The lack of

Table 2: CCD experimental design for RB5 removal by TiO

nanoparticles

Independent factors

Expt.

Pred.

Run

Independent factors

Expt.

Pred.

Run

Remova Remova

l (%)

6.5

1.2

0.7

1.2

0.7

1.2

0.7

0.2

1.2

0.7

0.2

1.2

0.2

0.7

1.2

0.7

1.2

0.2

1.2

0.7

0.2

1.2

0.2

120

67.5

120

67.5

100

37.1

83.4

61.3

32.6

60.7

78.7

60.9

58.1

66.6

80.3

62.7

27.9

84.8

68.9

26.4

63.3

36.2

77.4

60.3

40.6

79.7

75.9

65.6

78.4

35.7

51.6

38.8

28.5

38.10

81.75

62.06

34.30

62.06

79.13

62.06

68.52

81.38

62.06

32.34

85.18

68.07

28.09

62.06

37.30

81.81

62.06

40.73

82.56

79.19

68.01

78.76

38.23

51.62

36.93

28.91

1.2

0.2

0.7

0.2

1.2

0.2

0.7

1.2

0.7

1.2

0.7

120

67.5 40

120

67.5 40

15 60

67.5 40

100

34.7

70.6

57.8

69.3

34.8

68.5

27.8

30.3

67.2

55.6

33.7

60.6

58.9

59.2

35.3

61.1

59.9

60.5

62.5

61.7

56.8

59.3

86.6

63.3

62.3

63.9

61.5

58.6

34.67

72.32

62.06

68.95

34.73

68.89

28.97

27.66

71.44

62.06

37.36

62.06

40.95

62.06

61.37

62.06

62.67

57.88

61.09

83.17

62.06

63.02

57.01

6.5

67.5

120

67.5

120

67.5

120

67.5

0.7

67.5 40

67.5 20

67.5 40

67.5 60

67.5 40

0.7

6.5

120

0.2

65.2

67.64

6.5

0.7

67.5 40

60.8

62.06

0.2

120

100

31.3

27.9

31.46

28.54

6.5

0.7

120

67.5 40

67.4

63.7

62.06

−1

)

: pH, X

: TiO2 (gr L ), X

: Time (min), X

: Temperature (℃), X

: dye concentration (mg L

Table 3: Regression analysis for the reduced quadratic model

Model term

Intercept

푋_ꢅ

푋_ꢆ

푋₃

Coefficient estimate

60.98065

21.10893

4.87979

0.93225

1.11835

-0.87540

0.75011

-5.56679

2.23775

Std. error

0.42259

0.37638

0.38155

0.37638

0.39375

0.38809

1.13702

1.23870

t-Value

144.3030

56.0848

12.7895

2.4769

2.8402

-2.2232

1.9328

p-Value

2.2×10

0.0166787

0.0065035

0.0307504

0.0589335

1.064×10

0.0768539

0.0004995

푋 : 푋

ꢅ

ꢆ

푋 : 푋

ꢆ

푋 : 푋

ꢆ

푋

-4.8959

1.8056

-3.7235

ꢆ

푋

ꢆ

푋

-4.61225

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Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 3, Pages: 1232-1241

Table 4: Analysis of variance (ANOVA) for the reduced quadratic model

Model formula in RSM

Sum of squares

Mean square

Probability (P)

F-value

critical

First-order response

TWI(x1, x2)

TWI(x2, x5)

TWI(x3, x4)

Pure quadratic response

Residuals

15529.2

53.9

15.0

3105.84

53.89

15.00

10.06

313.54

4.76

652.1796

11.3161

3.1505

2.1130

65.8376

2.40

2.2×10^-¹⁶

0.001482

0.081993

0.152306

10.1

940.3

238.1

148.7

89.4

2.2×10

Lack of fit

Pure error

4.80

4.71

1.0196

2.07

0.494661

Notes: Multiple R-squared: 0.9858, Adjusted R-squared: 0.9827, F-statistic: 315.9on 11 and 50 DF, p-value: < 2.2×10

Moreover F-value of the model is significant (Fcal

150.24 > F0.05, 5, 45 = 4.45) and the lack of ﬁt value of the model

available in Table 4, is not signiﬁcant relative to pure error (Fcal

1.09 < F0.05, 26, 19 = 2.1) that these are indicated corre lation

The percentage of dye removal was altered by varying the

TiO dosage and pH. As can be understood from the figure in

the pH range of 10-11, with an increase of the TiO dosage from

0.8 to 1 gr L , removal efﬁciency was increased from 75 to

80%, in other words, removal efﬁciency increased with

increasing pH. These indications that pH plays an important

role in the degradation process (59). Fig. 6(B) illustrations the

between factors and dye removal as a response (52, 53). In

general, the efﬁciency of the model is explained by R , however

the multiple R-squared values (0.985) close to one and is very

close to the adjusted R-squared value (0.982) anticipated a

satisfactory adjustme nt between quadratic model and

experimental data (54, 55). Pareto analysis using the Eq.7 was

effects of TiO

dosage and dye concentration in the removal

efficiency of photo catalyst process. Based on this figure in the

employed to assess the importance of the role (P

) of the

TiO

dosage of 0.9-1 and at dye concentration of 50-60 mg L

, removal efﬁciencies was increased from 62% to 80%. The

interaction effects of time (X ) and temperature (X ) in Fig.

selected factors (factor i) on the created response.

훽_ꢏ^ꢋ

6(C), illustrations that the percentage of dye removal from 60

to 65% was increased with increasing time from 20 to 120 min.

푃_푖= (_∑_훽_ꢋ)

(7)

ꢏ

Based on the results, it is clear that the TiO dosage and pH are

the most effective variables in the dye removal efficiency (60,

61).

As indicated in Fig. 5, the following sequence was gained

in the terms containing singular factors X (pH, 77.1%) > X

TiO ; 12.31%) > X (Time; 0.15%), which approves that pH

and TiO plays the most important role among these terms. The

quadratic terms have the sequence of X

(

.5 Process Optimization and Confirmation

(3.67%)

(5.35%) > X

(0.86%), while the interaction terms have the sequence of

(0.21%) > X (0.13%) > X (0.1%). So the pH, the

and pH-TiO interaction play the most crucial

The Solver “Add-ins” was used by applying effective

parameters to achieve the optimum degraded condition through

the model equation predicted by RSM. These parameters

3 4

−1

quadratic TiO

contained pH (2-11), TiO dosage (0.2-1.2 g L ), contact time

role in the generated response. The results obtained from the

Pareto method can be well confirmed by the F-values (56, 57).

(15-120 min), temperature (20-60 ℃ ) and the initial dye

concentration (10-100 mg L ). In the optimum conditions, all

-1

parameters simultaneously are favorable criteria, and in the

predicted optimal the maximum removal efficiency was

accounted to be 90%. The predicted optimal conditions by the

.4 Response Surface Methodology and Contour Plotting

In order to study the effects of different parameters and

their interactions on the efficiency of the dye degradation via

TiO nanoparticles, the contour plots which are determinate

based on the model coefﬁcients is shown in Fig. 6(A-C). It is

notable that in these plots the effect of two variables is

investigated while the other parameters are stabled (58). The

effect of TiO dosage and pH solution on the removal efficiency

at the initial time of 67.5 min, temperature of 40 ℃ and dye

concentration of 55 mg L is shown in Fig 6-A.

Solver “Add-ins” were: the pH of 11, TiO dosage of 0.973 g

−1

L , contact time of 120 min, temperature 60℃ and initial dye

-1

concentration of 50.53 mg L . To confirm the validity of the

predicted optimum conditions, laboratory experiments were

accomplished, and the findings indicated that the experimental

data were in good agreement with the above-mentioned optimal

conditions (62-64). To verify the validity of the results

predicted by the model, additional laboratory experiments were

accomplished in four replicates. As it can be understood in

Table 5, experimental data were in good consistency with those

predicted through the regression model. Furthermore, there is

another set of experiments presented in Table 5, which is the

same as the above-mentioned optimal conditions except for

initial pH.

−1

The result indications that the R-squared value of the model

is very near to the adjusted R-squared value. The presence of

significant terms in the model was confirmed by the good

agreement between R adj (0.98) and R pred. (0.98) which is

presented in Fig. 7 (65).

Figure 5: Pareto plot for studying the importance of each variable to

the TiO response in the removal of dye

1237

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 3, Pages: 1232-1241

2 2

Figure 6: Contour plot for the effect of TiO dose and pH (A), dye concentration and TiO dose (B), time and temperature (C)

Table 5: Experimental and predicted values of the responses at the optimal levels predicted by RSM

Dye removal (%)

Dye concentration (mg L^-¹)

TiO

(g L )

Time (min)

120

Temp (℃)

Predicted

67.93

Experimental

87.45

120

65.08

Conclusions

In this survey, the degradation of dye via TiO

nanoparticle

at the solid/aqueous interface was studied. The CCD design

matrix was accomplished to evaluate the relationship between

-1

input-independent factors (pH, TiO dose (g L ), contact time

-1

min), Temperature (℃), and Dye concentrations (mg L )) and

one dependent output response (removal efficiency) on dye

degradation with TiO Photo catalyst. The quadratic equations

(

developed to for this study indicate good correlation between

actual and model predicted values of response. The results such

−16

as P-value (2.2 × 10 ), higher F-value (315.9), R (multiple

R-squared: 0.9858, adjusted R-squared: 0.9827), insignificant

lack of fit (0.494) show that the reduced full second order

model is highly significant for dye removal by TiO

nanoparticles. The closeness of the R-squared value of the

model to the adjusted R-squared value demonstrates that the

quadratic regression related to the reduced full second order

Figure 7: Correlation of actual and predicted removal efficiency for

dye direct blue 71

1238

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 3, Pages: 1232-1241

Bhatnagar A, Minocha A. Assessment of the biosorption

characteristics of lychee (Litchi chinensis) peel waste for the

removal of Acid Blue 25 dye from water. Environmental

technology. 2010;31(1):97-105.

model can be applied for prediction and optimization. The

maximum percentage removal of dye: 86.6% were achieved at

-1

optimum operating conditions, pH=11, TiO

dose (0.7 g L ),

contact time (67.5 min), Temperature ( ꢐꢁ ℃ ), and dye

. Li W, Li D, Chen Z, Huang H, Sun M, He Y, et al. High-efficient

Degradation of Dyes by Zn x Cd1− x S Solid Solutions under

Visible Light Irradiation. The Journal of Physical Chemistry C.

concentrations (55 mg L )), respectively. The maximum

removal efficiency was predicted to be 90%, using regression

coefficients achieved from the model and Solver “Add-ins”.

The predicted optimal conditions by the Solver “Add-ins” were

008;112(38):14943-7.

0. Marugán J, López-Muñoz M-J, van Grieken R, Aguado J.

Photocatalytic decolorization and mineralization of dyes with

nanocrystalline TiO2/SiO2 materials. Industrial & Engineering

Chemistry Research. 2007;46(23):7605-10.

1. Devi LG, Kumar SG. Exploring the critical dependence of

adsorption of various dyes on the degradation rate using Ln3+-

TiO2 surface under UV/solar light. Applied Surface Science.

achieved at the pH of 11, TiO

dose of 1 g L , contact time of

20 min, Temperature of ꢑꢁ ℃ and initial dye concentration of

1 mg L . So the results indicate that the photocatalytic process

-1

is very impressive in eliminating dye from contaminated water,

and it has a good efficiency in removing textile dyes.

012;261:137-46.

2. Jiang Y, Luo Y, Zhang F, Guo L, Ni L. Equilibrium and kinetic

studies of CI Basic Blue 41 adsorption onto N, F-codoped flower-

like TiO2 microspheres. Applied Surface Science. 2013;273:448-

Acknowledgement

This study is related to the project NO 904003/81 from the

Student Research Committee, Ilam University of Medical

Sciences, Ilam, Iran. We also appreciate the “Student Research

Committee” and “Research & Technology Chancellor” in Ilam

University of Medical Sciences for their financial support of

this study.

3. Liang C-H, Li F-B, Liu C-S, Lü J-L, Wang X-G. The enhancement

of adsorption and photocatalytic activity of rare earth ions doped

TiO2 for the degradation of Orange I. Dyes and pigments.

008;76(2):477-84.

4. Muthirulan P, Devi CN, Sundaram MM. Synchronous role of

coupled adsorption and photocatalytic degradation on CAC–TiO2

composite generating excellent mineralization of alizarin cyanine

green dye in aqueous solution. Arabian Journal of Chemistry.

Ethical issue

Authors are aware of, and comply with, best practice in

publication ethics specifically with regard to authorship

(avoidance of guest authorship), dual submission, manipulation

of figures, competing interests and compliance with policies on

research ethics. Authors adhere to publication requirements

that submitted work is original and has not been published

elsewhere in any language.

017;10:S1477-S83.

5. Ajoudanian N, Nezamzadeh-Ejhieh A. Enhanced photocatalytic

activity of nickel oxide supported on clinoptilolite nanoparticles

for the photodegradation of aqueous cephalexin. Materials Science

in Semiconductor Processing. 2015;36:162-9.

6. Babaahamdi-Milani M, Nezamzadeh-Ejhieh A. A comprehensive

study on photocatalytic activity of supported Ni/Pb sulfide and

oxide systems onto natural zeolite nanoparticles. Journal of

hazardous materials. 2016;318:291-301.

Competing interests

The authors declare that there is no conflict of interest that

would prejudice the impartiality of this scientific work.

7. Massoudinejad MR, Sadani M, Gholami Z, Rahmati Z, Javaheri M,

Keramati H,et al. Optimization and modeling of photocatalytic

degradation of Direct Blue 71 from contaminated water by TiO

nanoparticles: Response surface methodology approach (RSM).

Iranian Journal of Catalysis. 2019;9(2):121-132.

8. Kordouli E, Bourikas K, Lycourghiotis A, Kordulis C. The

mechanism of azo-dyes adsorption on the titanium dioxide surface

and their photocatalytic degradation over samples with various

anatase/rutile ratios. Catalysis Today. 2015;252:128-35.

9. Belessi V, Romanos G, Boukos N, Lambropoulou D, Trapalis C.

Removal of Reactive Red 195 from aqueous solutions by

adsorption on the surface of TiO2 nanoparticles. Journal of

hazardous materials. 2009;170(2-3):836-44.

0. Carvalho HW, Batista AP, Hammer P, Ramalho TC. Photocatalytic

degradation of methylene blue by TiO2–Cu thin films: Theoretical

and experimental study. Journal of hazardous materials.

Authors’ contribution

All authors of this study have a complete contribution for

data collection, data analyses and manuscript writing.

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