Highly effective photocatalytic degradation of methylene blue using PrO2–MgO nanocomposites under UV light

Highly effective photocatalytic degradation of methylene blue using PrO2–MgO nanocomposites under UV light

Journal Pre-proof Highly effective photocatalytic degradation of methylene blue using PrO2–MgO nanocomposites under UV light R. Priya, S. Stanly, Kavi...

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Journal Pre-proof Highly effective photocatalytic degradation of methylene blue using PrO2–MgO nanocomposites under UV light R. Priya, S. Stanly, Kavitharani, Faruq Mohammad, Suresh Sagadevan

PII:

S0030-4026(20)30152-2

DOI:

https://doi.org/10.1016/j.ijleo.2020.164318

Reference:

IJLEO 164318

To appear in:

Optik

Received Date:

18 December 2019

Accepted Date:

25 January 2020

Please cite this article as: R. P, S. S, Kavitharani, Faruq M, Suresh S, Highly effective photocatalytic degradation of methylene blue using PrO2–MgO nanocomposites under UV light, Optik (2020), doi: https://doi.org/10.1016/j.ijleo.2020.164318

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Highly effective photocatalytic degradation of methylene blue using PrO2– MgO nanocomposites under UV light R. Priya1, S. Stanly2, Kavitharani1, Faruq Mohammad3 and Suresh Sagadevan4*

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Department of Chemistry, Veltech High-tech Dr.Rangarajan and Dr.Sakunthala Engineering

College, Avadi, Chennai, Tamil Nadu. Department of applied chemistry, Srivenkateswara Engineering College, Sriperumbudur,

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2

Chennai. 3

Surfactants Research Chair, Department of Chemistry, College of Science, King Saud

University, Riyadh, Kingdom of Saudi Arabia 11451 4*

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Nanotechnology & Catalysis Research Centre, University of Malaya, Kuala Lumpur 50603,

Malaysia

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*Corresponding author E-mail: [email protected]

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Abstract

The present work deals with the synthesis, characterization, and photocatalytic degradation of

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PrO2–MgO nanocomposite where it was formed by the green approach. Following the synthesis, many different kinds of instrumental analysis for the investigation of crystal

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structure, morphology, size, shape, elemental analysis, optical properties, etc. For the

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efficiency testing of PrO2-MgO, the photocatalytic degradation of methylene blue dye in the presence of visible light was used and for that, the spectrophotochemical technique was employed. The rate of dye degradation in accordance with the changes in solution pH, dye concentration, photocatalyst amount, and light intensity was measured, where the results supported 100% degradation under the optimum conditions.

Keywords: Photocatalytic decolourization, Methylene blue dye, PrO2–MgO nanocomposite, green chemistry, UV-vis spectroscopy. 1. Introduction Photocatalysis and its associated technologies offer excellent means for the environmentallyfriendly removal of organochemical pollutants. It has been noted that under ultraviolet (UV)visible light irradiation, the nanostructured semiconductor metal oxide photocatalysts can degrade many different organic pollutants without the formation of greenhouse gas emissions. The

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photocatalysis is a process that involves the breaking down or decomposition of various dyes, organic dirt, and biological species such as harmful fungi and viruses on surfaces with the use of UV or visible light irradiation to make it clean [1-2]. The dyes mostly enter the environment

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through the industrial effluents of textile, paint, wood processing, paper manufacturing etc.

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As of today, there are more than 100,000 dyes accessible commercially and over 100 lakh tonnes of dyes are being produced per year and among that, about 50% are fabric related

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dyes. A majority of these dyes break down in the environment to produce the byproducts which are mostly target organic oriented, mutagenic, cancer-causing, and thus be poisonous

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to life. Hence, it is highly essential to retain the dyes after their use from entering the water streams and for that, the crucial step in the development of simple, cost-effective, and better-

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performing systems for the purification of dyes from wastewater [3]. Many procedures are used for dye degradation including chemical oxidation, flocculation, chemical coagulation,

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membrane filtration, photochemical degradation, and biological degradation [4]. These methods have one or other disadvantages, and none of them is effective in completing the degradation of dyes used for colouring from wastewater. Currently,

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photocatalysis is a favourable tool for the degradation of dye colours from effluents taking into consideration of its eco-friendly, economically low, and easily maintainable treatment policies. According to the different researchers, there are various semiconductors including

CuO, Fe2O3, TiO2, and ZnO used as photocatalysts because of their facility to degrade the dye-containing effluents. With the use of these materials, the removal of dye pollutants uses photocatalysts and UV lamp for generating the energy to form oxide radicals [5]. The photocatalysis process is considered to be a proficient method owing to its effective utilization of highly available solar energy and formation of non-toxic mineralized products (such as H2O, CO2 etc) and therefore, the designing of visible light-active photocatalyst materials is a most important objective among the scientific community for the disinfection

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of microorganisms and for the treatment of hazardous pollutants. The photocatalysis is the reaction of light with that of the semiconductor material and which results in the transfer of electrons from the valence band (VB) to the conduction band (CB) to create some superoxide

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anions to further participates in the free radical reactions to finally degrade the dye [6-9]. In the present paper, a novel PrO2–MgO nanocomposite was applied for the removal of colour

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from dye degradation in a short and effective means of the water treatment process. One of

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the studies from a different researcher deals with the studies of MgO nanoparticles and their photocatalytic activity towards the degradation of methylene blue (MB) using UV light in 4 h [10]. To further explore the photocatalytic potency of MgO nanoparticles, the present study

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deals with its nanocomposite formation after the mixing with praseodymium oxide (PrO2) novel photocatalysts. Following the in-depth characterization of the composite, the

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photocatalyst was studied for its photodegradation capability for the degradation of MB using

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UV light for a total of 90 min period. 2. Experimental 2.1 Materials Magnesium

acetate

tetrahydrate

[(CH3CO2)3Pr.H2O],

and

praseodymium

acetate

[C4H14MgO8] of Analytical grade (AR) standard was purchased. Pomegranate, apple, grape, orange, and banana (PAGOB) is a variety of fruit peel waste used and was collected from

senneerkuppam, Chennai, Tamilnadu, India. Double distilled water was used as a solvent and the fruit waste extract as a stabilizing agent. Methylene blue (MB) dye was used for extraction and the UV light used to undergo the degradation process effectively [6]. 2.2 Preparation of extract For the extract preparation, the mixed fruit waste, PAGOB was sliced into tiny particles and dried under sunlight for about 48-50 h in order to remove the moisture from it. The dried particles were ground to powder and kept in an airtight container. Approximately 12 g of

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PAGOB powder was boiled in a solution mixture containing 60 mL distilled water and 30 mL ethanol for 30 min at 70ºC temperature to obtain the PAGOB peel extract and further used for this peel extract for the preparation of mixed oxide nano-sized particles [9]. 2.3 Preparation of PrO2–MgO nanocomposite

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For the formation of PrO2–MgO nanocomposites, equal amounts of praseodymium acetate

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and magnesium acetate tetrahydrate were first dissolved individually in 50 mL distilled water. Now both the solutions mixed together, and stirred well on a magnetic stirrer to form

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the homogeneous solution and further the fruit waste extract was added drop by drop to the homogeneous solution. The reaction temperature was maintained in the range of 60–65°C for

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about 3 h and after the period, the obtained powder was dried at a temperature of 85oC for 6 h in a hot air oven and finally the samples were subjected to a heating temperature of 500oC for

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2 h.

2.4 Testing of photocatalytic activity

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The photocatalytic activity of PrO2–MgO nanocomposite was determined towards the dye degradation and the studies were carried using the UV reactor. The experiments were carried out by mixing the preferred quantity of PrO2–MgO nanocatalyst into 100 mL of MB dye solution and further the optical absorbance with the help of UV-Vis spectrophotometer was measured. The optical properties were used to find the percentage of photocatalytic

degradation [11,12] and the obtained values are used to find the percentage of photocatalytic degradation using the following formula. % of photodegradation = [(Ci- C)/ Ci]x 100 Where, Ci and C correspond to the concentrations before and after the photocatalytic degradation reaction. The removal of colour from MB dye using PrO2–MgO nanocomposite under UV light was

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tested against the changes in parameters like photocatalyst dost, solution pH, dye concentration, reaction time etc. The above parameters are analyzed and found the percentage colour removal of MB dye.

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3. Results and discussion 3.1 Physical characterization

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The powdered XRD pattern of PrO2–MgO nanocomposite is displayed in Figure 1 and from

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the figure, the peaks can be assigned to the planes of (1 1 1), (2 0 0), (2 2 0), (3 1 1), (2 2 2), (4 0 0), (3 3 1), (4 2 0), and (4 2 2) correspondingly. The observation of these peak positions corresponds to the cubic structure of PrO2 and is in accordance with the JCPDS 75-0152 data.

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The remaining peaks are assigned to (2 0 0), (2 2 0), (3 1 1), and (2 2 2) planes corresponding

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to the index of the same cubic structure of MgO too as per the JCPDS 89-7746 data.

Counts MgO-PrO 6000

4000

0 20

30

40

50

60

Position [°2θ] (Copper (Cu))

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2000

70

80

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Fig. 1. Powdered XRD pattern of PrO2–MgO nanocomposite.

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Fig. 2 shows the surface morphology of PrO2–MgO nanocomposite studied using the HRSEM analysis and from the figure, the formation of sheet and flake shaped agglomeration

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can be seen from the micrographs. Similarly, the EDAX spectrum of the sample is shown in Fig. 3 and the corresponding peak information relating to the atomic percentage measured for

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the proportion of the components is provided in Table.1 From the analysis, we obtained proof for the presence of respective elements like Mg, Pr, and O in the composite and further found

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that the atomic percentage of Mg (21.8 %) is more than Pr (10.67 %).

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Fig. 2. HRSEM images of PrO2–MgO nanocomposite. cps/eV

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18 16 14

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12 10

6 4

O

Pr

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2

C

Mg

Pr

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8

0

1

2

3

keV

4

5

Fig. 3. EDAX spectrum of PrO2–MgO nanocomposite.

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Table 1. EDAX provided an atomic concentration of elements from the PrO2–MgO composite. Element AN Series Wt. % Wt. % At. % Pr 59 K 41.68 49.18 10.67 Mg 12 K 14.68 17.32 21.80 O 8 K 23.70 27.96 53.45 The TEM analysis for the investigation of size, shape, and morphology for the PrO2–MgO nanocomposite at different magnifications are shown in Fig. 4. From TEM images, it can be

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seen that the nanocomposite is formed as cubic structures. The TEM image of sample (a) claims for the morphology of PrO2–MgO nanocomposite which is an overlap sheet-like structure. Similarly, the TEM images of MgO depict the nanorod with a cubical shape which

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is in accordance with the XRD’s cubic phase (Fig. 1). In addition to that, the TEM images of PrO2–MgO nanocomposite show that the nanorods are embedded in the sheet-like

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morphology.

Fig. 4 TEM images of PrO2–MgO nanocomposite.

3.2 Effect of dose of PrO2–MgO nanocomposite To test the effect of PrO2-MgO catalyst dose towards the degradation of MB dye, the changes in the catalyst dose in the range of 0.1 – 0.8 g is allowed to react with a 100 mL of 40 ppm dye solution at many different pHs (5.2, 4.1, 3.2, and 2.2) for 30 min under visible light at 30ºC was applied. Figure 5 shows the results of the analysis and from the figure, it can be observed that the MB degradation reaction is strongly influenced by the catalyst amount. We found that the increase of catalyst amount from 0.1 to 0.8 g shifted the MB degradation

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percentage from 80 to 100%. Further increase of catalyst amount above 0.8 g did not have an effect on the MB dye degradation and in addition, a pH of 2.2 was investigated to be the most efficient and 5.2 being the least. Hence from the analysis, the efficient photodegradation of

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MB dye is noted with 0.5 g of catalyst dose at a pH of 2.2.

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95

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90 85 80 75

5.2 4.1 2.2 3.1

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% OF PHOTOCATALYTIC ACTIVITY

100

70

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65 60

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0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

DOSE OF CATALYST

Fig. 5. Effect of dose of PrO2–MgO nanocomposite.

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3.3 Effect of illumination time Figure 6 shows the relative changes in the photodegradation of MB dye with the PrO2-MgO composite with respect to time was monitored by increasing the irradiation time under the same conditions (100 mL of 40 ppm MB dye solution mixed with 0.5 g of PrO2–MgO nanocomposite catalyst and pH changes) over a 90 min period. From the analysis, we found that the photodegradation of MB dye solution is getting increased with regards to an increase in the illumination time. We found that the most efficient condition is the one with a pH of

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2.2 was the degradation percentage reaching to 100% in just 40-50 min of illumination time. This indicates the relatively high activity for the prepared PrO2-MgO catalyst, enabling for the complete degradation of MB dye in such a short illumination time, where the catalyst has

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100 95

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90 85 80

5.2 4.1 3.1 2.2

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% OF PHOTO CATALYTIC DEGRADATION

active sites for carrying out the reaction [13-14].

75 70

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65

10

20

30

40

50

60

70

80

90

CONTACT TIME (min)

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Fig. 6. Effect of contact time for the degradation of MB dye.

3.4 Effect of dye concentration Figure 7 shows the photocatalytic activity of PrO2-MgO as against the changes in the dye concentration in the range of 10 - 200 ppm under the same experimental conditions (100 mL of 40 ppm solution mixed with 0.5 g catalyst at varying pHs of 5.2, 4.1, 3.1 and 2.1). We

observed from the results that the efficiency of the photocatalyst is inversely proportional to the dye concentration under the tested conditions, i.e. highest activity was observed at 10 ppm dye. On increasing the dye concentration from 10 to 200 ppm, the MB dye degradation efficiency is getting shifted from 100 to 65%. In general for critical degradation, the typical process involves the formation of hydroxyl or superoxy radicals to further participates in the catalytic decolorization reaction [15-16]. When the dye concentration is low, the formed radicals are good enough for the breakdown of dye and so we observed the efficiency to be

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maximum; with increased concentration, higher be the adsorbed organic moieties at the catalyst surface that cannot be handled by the limited catalyst sites and so efficiency got decreased. Thus, the analysis provided the information that a 40 ppm of initial dye

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concentration with 0.5 g of catalyst amount over a 40-50 min reaction time at solution pH 2.2

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can offer a 100% efficiency.

80

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70

5.2 4.1 3.1 2.2

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90

60 50

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% OF PHOTOCATALYTIC ACTIVITY

100

40 30

0

50

100

150

CONCENTRATION (ppm)

Fig. 7. Effect of concentration.

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4. Conclusion In the present paper, the PrO2–MgO nanocomposite was prepared by using multiple fruits peel extract and the physical properties of nanocomposite were thoroughly studied. We provided an approach here for the formation of catalyst that uses the unwanted fruit wastes like the extract of PAGOB and does not require volatile or hazardous chemicals for the reaction. The powdered XRD pattern confirmed for the presence of cubic structure in the composite while the HRSEM revealed for the sheet and flake shaped particles with

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agglomerations. The TEM studies confirmed for the nanocomposite in a rod structure and the cubic phase. On testing of the PrO2–MgO composite towards the photochemical degradation of MB dye under UV light, we found that the material is highly active and the activity is

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influenced by the changes in solution pH, illumination time, catalyst amount, and initial dye concentration. The highest activity is being observed for 0.5 g of a catalyst with a 40 ppm of

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dye concentration over a period of 40-50 min and at a pH of 2.2. From the analysis, it can be confirmed that the developed catalyst can be applied for the economical and environmentally-

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Competing interests:

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friendly removal of toxic dye pollutants from the textile industrial effluents.

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The authors declare no conflict of interest.

Acknowledgements:

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The King Saud University author is grateful to the Deanship of Scientific Research, King Saud University for funding through Vice Deanship of Scientific Research Chairs.

Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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