Accepted Manuscript Title: Process Intensified Removal of Methyl Violet 2B Using modified Cavity-Bubbles oxidation reactor Authors: Ashish V. Mohod, Shruti P. Hinge, Rajendra S. Raut, Manisha V. Bagal, Dipak Pinjari PII: DOI: Reference:
S2213-3437(17)30692-9 https://doi.org/10.1016/j.jece.2017.12.053 JECE 2100
To appear in: Received date: Revised date: Accepted date:
1-9-2017 20-12-2017 22-12-2017
Please cite this article as: Ashish V.Mohod, Shruti P.Hinge, Rajendra S.Raut, Manisha V.Bagal, Dipak Pinjari, Process Intensified Removal of Methyl Violet 2B Using modified Cavity-Bubbles oxidation reactor, Journal of Environmental Chemical Engineering https://doi.org/10.1016/j.jece.2017.12.053 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Process Intensified Removal of Methyl Violet 2B Using modified Cavity-Bubbles oxidation reactor Ashish V Mohod1, Shruti P Hinge2, Rajendra S Raut1, Manisha V Bagal3* Dipak Pinjari2* 1
Department of Chemical Engineering, AISSMS College of Engineering, Kennedy Road, Near
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RTO, Pune, 411001 (INDIA). Chemical Engineering Department, Institute of Chemical Technology, Matunga, Mumbai-
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400019 (INDIA).
Department of Chemical Engineering, Bharati Vidyapeeth College of Engineering, Navi
*Authors to whom correspondence may be addressed
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Mumbai-4000614 (INDIA).
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Manisha V Bagal: Email:
[email protected]; Contact no: +918108156731
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Dipak Pinjari:Email:
[email protected]; Contact no:+919967719496 Contact Information of Other authors
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Ashish V mohod1, Contact no: +91-8600815435,
[email protected] Shruti P Hinge2, Contact no: +91-9579791983,
[email protected]
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Rajendra S Raut1, Contact no: +91-9850269999,
[email protected] ABSTRACT
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An intensified method for treatment of wastewater containing a commercial dye (Methyl Violet 2B (MV 2B)) has been studied with novel approaches based on UV-air bubble induced oxidation. A modified reactor containing small glass balls was used for this purpose. The
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impact of the operating parameters such as initial concentration and pH as well as the effect of loadings of various catalysts likeTiO2, MnO2, ZnO etc. on the extent of removal of MV 2B dye have been investigated. So as to maximize the efficacy of removal of the dye, the reactor used in the author’s earlier work was modified by incorporating ultraviolet light source in the system. The removal of Methyl Violet (2B) was found to be maximum (96.8%) with the 1
loading of a mixture of TiO2 and MnO2 catalysts. Also, the effect of various metal oxide catalysts on the removal of methyl violet 2B has been observed in the order of TiO2> MnO2>ZnO. Overall, the present investigation established that hybrid processes with the use of optimized loading of catalysts have promising future and can be successfully applied for the
Keywords: Intensification; UV; Oxidation; Methyl Violet 2B; Removal.
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1. Introduction
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removal of toxic dyes from aqueous solution with intensification benefits.
The production of toxic waste is increasing day by day as textile and other industries are growing remarkably. The impact of this toxic waste on the environment is quite quick and
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treacherous. Especially, dyes and pigments which play a vital role in the textile and dyeing
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industry and create a tremendous amount of toxic waste [1]. It has been observed that more
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than ten thousand dyes are currently utilized in the textile industry [2]. The discharge of such
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harmful dyes into the atmosphere creates severe environmental damage. The dyes have strong,
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complex and penetrative color with high mineralization demand. Also, azo dyes and subsequently their resulting products cause the serious carcinogenic effect to the environment
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[1]. The main purpose of the treatment of wastewater is to allow sewage and industrial effluents disposed of without causing unacceptable damage to the human and aquatic life, health or to
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the natural environment. Thus, there is a need to develop a sustainable process intensification technology which will treat the wastewater produced by industry before its disposal into the
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water bodies. Several efforts have been dedicated to develop the intensified process technologies those are ready to minimize the dangerous effects caused by industrial activities. Various processes have been developed to treat the textile wastewater containing dyes which include membrane technology, activated carbon adsorption, chemical precipitation and biological treatment. However, these methods, singularly, are not efficient because of the high 2
salt contents resulting from reactive dying [3] and there are chances of generation of the secondary waste. The biological process is ineffective for the treatment of these dyes because of the requirement of large carbon footprint, less flexibility in the operation with other processes and more time requirement. The other process such as adsorption, electrocoagulation and flocculation [4] used for the treatment of wastewater containing dyes are not effective as
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they produce secondary waste in the form of solid. Thus, it is important to build up critical systems with intensified techniques leading to complete removal of these dyes from the
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effluents without generation of the secondary waste.
Advanced oxidation processes (AOP) produce hydroxyl radicals and could be one of the
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intensified processes to degrade MV 2B. These OH radicals are produced either by using
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chemical oxidants such as O3, H2O2 etc. or by adding the external energy such as ultrasound or
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ultraviolet irradiations with or without the use of catalysts. [5-15]. However, it has been
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observed that the approach of a combination of different AOPs is more competent for
efficiencies. [15-20].
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wastewater treatment than that of individual AOP due to considerably higher energy
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In the present work, cavity-bubbles induced oxidation reactor with glass balls has been used in combination with ultraviolet irradiation. The working principle of this reactor is similar to
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the hydrodynamic cavitation where cavities are generated based on the orifice and venturi. In this work, two mechanisms have been explained which are responsible for the degradation. Use of glass balls and passage for high-velocity air through interstitial areas are creating similar
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conditions to the cavitation. In the first mechanism, when the high-velocity liquid fall on the surface of the glass balls continuously, it might create sufficient shear effects where the conditions of high local temperature and pressure could be developed resulting in the generation of oxidizing radicals. In another mechanism, when air passes through the glass balls, it induces liquid jets, which distribute into many smaller bubbles. The bubble contains some 3
amount vapor and when the inner wall tension reaches a maximum limit, the bigger bubbles break instantly leading to the formation of oxidizing agents. However, UV light is used for the direct oxidation of the dye and also driven for the photo-excitation of the semiconductor. The general mechanism of the formation of oxidizing radicals and their interaction with UV light
H2O + cavity-bubble collapse→ H+ + OH* H2O + cavity-bubble collapse→ ½ H2 + ½ H2O2*
(2)
OH* + Dye → Degradation of the dye
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(1)
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is as follows:
(3)
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The present work is an extension of the work by Mahale D D et al. [23] who investigated
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the degradation of MV 2B dye from aqueous solutions using air bubble-induced oxidation
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using glass balls. It was reported that the removal efficiency of MV 2B from wastewater can
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be enhanced in presence of various process intensifying additives using air bubble oxidation. However, in the present work, authors have intensified the process by modifying the
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equipment. The equipment now operates in a continuous mode and introduces UV light inside the reactor. The objective of the present work was to investigate the effectiveness of cavity-
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bubbles induced reactor by introducing the UV light and also to intensify the operation by
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investigating the effect of catalyst and additives to achieve maximum degradation of a basic dye MV 2B.
MV 2B has been used as a model pollutant for the destruction with the help of modified cavity-
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bubbles induced oxidation with UV irradiation. It is a basic dye with highly brilliant color and intensity and widely used in textiles as a purple dye and in paint and ink as a deep violet. It was also reported that the MV 2B affects the bacterial growth and reaction of photosynthesis by the aquatic plant. MV 2B which can cause irritation of eyes and skin damages. The harmful properties of the MV 2B dye may cause damage to human and aquatic life. Therefore complete 4
removal of MV 2B dye from industrial effluents before disposing into the river is necessary [24-25]. 2. Materials and Methods: 2.1 Materials:
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Methyl Violet 2B (crystal structure) is also called Gentine violet B, methylrosanilinium, basic violet 3. Methyl Violet is an organic compound containing methyl groups. The molecular
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structure of methyl violet 2B has been shown in Fig. 1. The required concentration of aqueous
solution of Methyl Violet 2B was made by using demineralized water. Titanium Dioxide (TiO2), Manganese Oxide (MnO2) and Zinc Oxide (ZnO) were purchased (all of AR Grade)
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from Merck Specialties Pvt. Ltd., Mumbai, India. TiO2 (fine powder with nano-size range)
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used in the present work was a combined of anatase and rutile form. The characterization of
2.2 Equipments and Procedure
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titanium dioxide powder with SEM images was reported in the earlier work [26].
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In the author’s earlier study [23], the maximum degradation of 73.1% of 20 ppm Patent
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blue V solution was obtained using cavity-bubbles induced oxidation without adding any catalyst for reaction time of 180 min in batch mode. However, our main objective is to reduce
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the reaction time and to achieve the maximum efficacy of removal of the dye. To reduce the reaction time, it is important to introduce maximum amount of energy which generates more amount of oxidizing radicals in the solution. Thus, authors modified the earlier cavity-bubbles
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induced oxidation reactor with the addition of UV source. Also, this technique can be useful for the effluent treatment of any industry if it can be operated at a larger volume. But the limitation of the reactor is the size of the reactor; as to induce cavities in the solution thus, it requires certain jet flows inside the reactor. Authors made an attempt to suppress the above limitation by carrying out experiments in a continuous mode. The detailed schematic 5
representation of UV-air bubble oxidation reactor has been depicted in Fig. 2. An ultraviolet lamp was introduced in the central compartment of the reactor and -submerged pump was used to operate the reactor in a continuous mode. The rest of the assembly was kept same as per the previous work [23].
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The effect of process intensifying additives with the range of 0.2–1% (w/v) loading has been investigated. 10 ml of the samples were withdrawn from the solution after regular interval
of 20 min. Before analysis, the samples were filtered using Whatman's filter paper (0.1µm) for
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removal of solid particles. To check the reproducibility, all the experimentally obtained results were checked repeatedly and average values within 2% error bar have been reported in the
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discussion. The samples for treated and untreated solutions were determined for degradation
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under a UV–VIS spectrophotometer (Chemito Spectra scan UV 2600 double beam) at a
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wavelength, λ =675 nm.
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Adsorption studies of MV 2B on catalyst surface of metal oxides were also investigated as a
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preliminary study. In the experimental run, the catalyst of TiO2, ZnO, and MnO2 has been used with 100 ml of the dye solution and the mixture was kept for 24 hours in a dark room. It has
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been observed the change in the dye concentration on the catalyst surface was 4%, 3% and 2% for the catalyst of TiO2, ZnO, and MnO2, respectively. Thus, based on the result of adsorption
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studies, error bars have also been shown to depict the variation, which was within 2% of the reported average value.
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3. Results and Discussions 3.1 Effect of initial dye concentration The effect of initial concentration of MV 2B on the extent of degradation has been investigated with a concentration of 10, 20 and 30 ppm. The obtained results of the effect of initial concentration on the extent of degradation are shown in Fig. 3. It can be observed from
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Fig. 3 that rate of degradation of MV 2B is strongly affected by the initial concentration of dye and the extent of degradation decreases with increase in the initial concentration of dye. Initially, at a lower concentration of the dye, the oxidizing radicals are in excess which to oxidizes higher quantity of dye which is available in the solution and gives maximum degradation of MV 2B. However, with an increase in the concentration of the dye i.e. above
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optimal condition, there is limited availability of the oxidizing species leading to a lower extent of degradation. Hence, lower initial concentration of 10 ppm, was selected for further studies.
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It can also be seen from the figure that the rate of degradation of methyl violet for 10 ppm was 20 times higher than 20 and 30 ppm. The minimum removal of methyl violet at higher
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concentration is due to the fact that production of hydroxyl radicals is reduced with increases
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in the initial concentration of the dye. The possibility of reaction between the dye and oxidizing
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agents may decrease with increasing dye concentration which results in the lower destruction
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of MV 2B.
In comparison with author’s earlier work [23] on cavity-bubbles induced oxidation, similar
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results were obtained. It was reported that maximum extent of degradation of Patent blue V of 57% was obtained at 20 mg/L of initial concentration for a reaction time of 180 min. However,
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in the case of UV-air bubble induced oxidation, the maximum extent of removal of methyl
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violet 2B of 64 % was obtained at 10 ppm. This is due to the fact that initially, the oxidizing agents are in excess because of the combined effect of cavity-bubbles and ultraviolet irradiation, and with an increase in concentration, there is a possibility to oxidize maximum
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amount of the dye solution. However, in case of high concentration of dyes, it has been found that very less penetration of photon will take place using UV as well as solar radiation. As a result of this, a decrease in concentration of OH radicals at higher concentration of MV 2B gives the lower extent of removal at higher loadings.
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It can be noted here that with the number of available OH radicals and dye molecules to be oxidized at the interface of the cavitation bubble offers higher initial extent of removal of the dye due to the presence of higher availability of OH radicals at the surface of the collapsing bubble. However, at higher dye concentration, generation of radicals is less in the bubble and can be easily dispersed into the bulk solution, thus resulting in a lower rate of removal. Hence,
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it is considered that at a lower concentration of dye, the possibility of OH radical to attack on
MV 2B molecule is notably increased which results in the higher rate of removal. In contrast,
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if the concentration of dye is higher then the generation of hydroxyl radicals reduces and reaches its saturation limit.
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The kinetic analysis for the removal of methyl violet 2B using UV-air bubble induced
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oxidation has been investigated using first-order kinetic model and is given as follows: …(1)
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ln (C0/C) = k × t
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Where C0 is the initial concentration and C is the concentration at any time t. The plot of ln (C0/C) i.e. concentration data versus time gives a straight line with the slope which indicates to
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the pseudo-first-order kinetics. The kinetic analysis of MV 2B dye using UV-air bubble oxidation reactor is given in Fig. 4. The first order kinetic rate constant was obtained as 5.0 ×
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3.2 Effect of pH
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10-3 min-1 and R2 =0.99 for an initial concentration of 10 ppm.
The removal of dyes strongly depends upon pH of the solution as it affects the bubble
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dynamics. Various experiments have been conducted to find out the effect of pH (over the range of 2 to 12) on the removal of MV (2B) in the presence of UV light and cavity-bubbles induced oxidation. In all the experiments, the pH values of the dye solution were adjusted by using concentrated H2SO4 and 1 N NaOH solutions. The obtained results have been given in Fig.5 and Table 1. It has been observed from the table that higher removal of dye was obtained
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at neutral conditions of pH rather than that of the acidic and basic condition. The maximum removal of 94 % was obtained at 10 ppm MV 2B at pH 7.2 and the extent of removal decreases as the pH increases. The decrease in the removal rate in basic pH range may be because of the formation of the oxidizing species hydroperoxy anion (HO2-) in an alkaline medium which is the conjugate
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base of H2O2. This HO2- anion have a tendency to react with both the •OH radical as well as
H2O2 molecules, thus, as a result, lowers the rate of oxidation of dye [27-29]. Also in alkaline
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medium, dye molecule gets ionized and remains in the bulk liquid where oxidizing OH radicals are lesser as compared to that at bubble water interface and hence lowering the extent of
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removal of dye.
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In the meantime, for acidic pH, strong acid (H2SO4) was used which possibly creates
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interference in the photon interaction with the dye compound and also increases the high
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concentration of proton in the dye solution, resulting in lower removal efficiency.
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3.3 Effect of presence of catalysts
Many kinds of literature revealed that presence of catalysts such as metal oxides
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enhances the extent of removal of dye. With this background, the same fundamental has been
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used to carry out experiments using cavity-bubbles induced oxidation along with UV irradiation for enhancement in removal efficiency. The effect of loading of solid particles such as nano-sized ZnO powder; TiO2 and MnO2 powder (over the concentration range of 0.2 – 1
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g/L) on the removal of MV 2B and the results have been depicted in the Fig.6. The obtained results show similar trends [23] of enhancement in extent of dye removal with presence of solid catalyst and can be due to the fact that the presence of metal catalyst such as ZnO, TiO 2 and MnO2 favors the dissociation of water molecules thereby increasing the generation of free radicals results in increases the extent of removal of the organic compound.
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Fig.6 shows that only up to an optimum loading of three solid catalysts, the extent of removal increases and beyond that, it decreases. It may be due to raising in the turbidity of the solution at higher loading of solid particles which results in the lesser availability of active sites for removal due to the accumulation of molecules. Also due to the highly turbid suspension at higher loadings of catalyst concentration the farthest catalyst does not get illuminated. [30, 31].
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The results are consistent with the literature [32-35]. Suri et al. [34] investigated the
removal of toluene, trichloroethylene, and methylethylketone with the presence of TiO2 loading
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at various initial concentrations of pollutants.
However, increased removal of methyl violet 2B with the increase in loading of solid
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catalysts may be due to the increase in the active surface area of a catalyst which leads to
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increase in the availability of active sites on the catalyst surface. Also, observed effect may be
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possible because of the adsorption characteristic of the MV 2B dye on the ZnO powder.
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From the figure, it has also been observed that the optimum value of this different
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catalyst loading was not same for the removal of MV 2B. It has been found that optimum loading of catalyst for nano-sized ZnO and TiO2 powder was found to be i.e. 0.6 gm/L.
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However, in the case of MnO2, the optimum catalyst loading was 0.8 g/L. This may be due to the size of solid particles affecting the specific area of catalyst surface and the extent of
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heterogeneity. The comprehensive characterization of solid catalysts with SEM images for TiO2 particles have been reported in our earlier work [26], where it has been found that the particles are very fine in size and crystalline in nature which can probably offer higher active
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catalyst surface area with lower agglomeration. The crystalline nature of catalyst gives a higher extent of heterogeneity in the present system results in the enhancement in the extent of removal. 3.4. Comparison with cavity-bubbles induced oxidation.
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Photocatalysis is one of the best AOPs which enhances removal of dyes with the help of either UV or solar irradiation using catalysts. In all removal purpose, photocatalysis is dependent photo-excitation of the semiconductor followed by the generation of the electronhole pair on the catalyst surface [36]. In photo removal process, the generation of hydroxyl radicals (OH-) due to the decomposition of water or by reaction of the hole with OH- attacks
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the dye molecules [37]. Based on above mechanisms, the reactor was slightly modified by introducing UV lamp in the center compartment of the reactor and operated at a continuous
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mode. The comparison of the extent of removal and COD studies based on cavity-bubbles
induced oxidation and cavity-bubbles induced photo-oxidation has been given in Table 1. From
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the table, it is clearly established that the cavity-bubbles induced photo-oxidation is more
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prominent over degrading the dye as compared to cavity-bubbles induced oxidation. Also, it
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was observed that all the reaction parameters such as initial dye concentration, pH, catalyst
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loadings etc. are important while degrading the dye using cavity-bubbles induced photooxidation
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In the case of initial concentration and pH, the data obtained using both the reactors are almost similar except for their optimal initial concentration. However, the important thing to
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be noted here is that the enhanced extent of removal was obtained using cavity-bubbles induced
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photo-oxidation as compared to cavity-bubbles induced oxidation. This may be due to the fact that UV irradiation helps to provide additional oxidizing species and thereby increasing the
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extent of removal of dye. It is also seen that the maximum removal of PB V of 77 % was obtained with loading
of 0.3 g/L by cavity-bubbles induced oxidation by passing glass balls; however, with introducing UV irradiation and operation in continuous mode, the maximum removal of methyl violet 2B was 91.3% at the loading of 0.6 g/L of nano-sized ZnO powder.
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In the case of titanium dioxide and manganese oxide, it is clearly observed that the percentage removal of dyes increases linearly with increasing catalyst loading except for ZnO using both the techniques. In the case of optimal catalyst loading of 0.6 g/L of TiO2, the maximum extent of removal of PB V 83 % was obtained using cavity-bubbles induced oxidation, while 95% extent of removal of MV 2B was obtained using cavity-bubbles induced photo-oxidation. This
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may be due to the presence of a solid catalyst which increases the dissociation of water to increase the generation of a number of free radicals, which results in higher removal of the dye.
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In the case of MnO2 solid particles, from the Table 1, it can be seen that similar to TiO2 results, with increasing concentration of MnO2, the rate of removal of MV 2B as well as PB V
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also increases. Higher extent of removal of MV 2B 92% was obtained at 0.6 g/L of MnO2 using
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cavity-bubbles induced oxidation, while the extent of removal of PB V 80% was obtained at
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0.8 g/L of MnO2. The higher extent of removal of MV 2B is due to the fact that it gives extra
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nuclei for the cavitation phenomena thereby increases the cavitational events in the reactor which results in a development of the cavitation activity thereby increase in the number of free
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radicals. Overall, it has been observed that the order of activities for the better extent of removal of MV 2B is TiO2 than MnO2 and then finally by ZnO over a range of 0.1-0.8 g/L. The higher
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extent of removal of MV 2B using TiO2 may be dependent upon the characteristics of a catalyst
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such as a particle size, surface area etc. The obtained outcome are consisted with the reported trends in the literature of Bhaskar
et al [37] which stated that TiO2 was one of the best semiconductors which gives higher efficacy
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as compared to the other semiconductors. In the present work, mineralization study was also carried out based on the COD removal for MV 2B under optimized conditions of reaction for a time of 180 min and the results are presented in the Table 1. From the table, it is clearly observed that using catalyst TiO2
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maximum COD removal of 76% was obtained under cavity-bubbles induced oxidation with UV lamps. The trend of results for COD removal is almost same as like of earlier study [23] which is also depicted in the above table. 3.5. Effect of a combination of metal oxides on the removal of Methyl violet (2B)
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To investigate the effect of a mixture of catalysts on the removal efficiency of MV 2B, experiments were carried out using a mixture of catalysts such as TiO2+ZnO, TiO2+MnO2 and
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MnO2+ZnO using UV-cavity-bubble induced oxidation with small sized glass balls . Fig.7
shows 96% removal of MV 2B using a mixture of an optimum amount of TiO2 and MnO2, 0.6 g/L and 0.8 g/L respectively. Also, it can be seen from the figure that removal of dye using a
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mixture of catalysts (TiO2+MnO2) is greater than that using TiO2 and MnO2 alone. This may
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be attributed to the formation of multivalent Mn-TiO2. The introduction of MnO2 into titanium
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dioxide can alter the coordination environment of titanium in the lattice and transforms energy
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band structure of titanium dioxide.
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Also, the effect of a combination of ZnO+TiO2 catalysts on the extent of removal of MV 2B has been evaluated by performing experiments with a mixture of an optimum amount of Nano
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sized ZnO and TiO2 (0.6 g/L of each catalyst). The results obtained have been given in Fig 8, which shows 81% removal of MV 2B. It has been also observed from Fig 8. that the extent of
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removal of MV 2B at optimum dosing of a mixture of ZnO and TiO2 is less as compared to that of using ZnO alone and TiO2 alone. If ZnO and TiO2 nano composites are brought in contact with humid air, chemical adsorption of water molecule on available sites of oxide
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surface takes place.
The general reaction mechanisms for the direct oxidation of the dye based on the use of holes
can be given by the following equations: MV 2B + hv→ (MV 2B) (e-cb + h+vb)
(4)
With metal oxide 13
h+vb + dye → dye+ →
oxidation of the dye
(5)
The hydroxyl radical is an extremely strong and non selective oxidant (E0= +3.06V) which
h+vb + H2O → H+ + OH*
(6)
h+vb + OH- → OH*
(7)
OH* + Dye → Degradation of the dye
(8)
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leads to the partial or complete mineralization of several organic chemicals [38]
Another reactive intermediate which is responsible for the degradation is hydroxyl radical
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(OH*). It is either formed by the decomposition of water (6) or by reaction of the hole with OH- (7)
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ZnO and TiO2 both have electron vacancies. As a result of above reaction, electrons get
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accumulated at the ZnO and TiO2 surface thereby reducing the resistance of sensing element
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with increase in relative humidity and hence removal decreases. Fig 9 shows extent of removal
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of MV 2B using mixture of optimum loading of nano size ZnO (0.6 g/L)+ MnO2(0.8 g/L), MnO2 (0.8 g/L) alone and ZnO(0.6 g/L) alone. It can be also seen from the figure that the extent
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of removal of MV 2B is slightly increased at optimum dosing of a mixture of ZnO and MnO2 (95%) as compared to that of MnO2 alone (93.1%) and ZnO alone (91.3%). It might be due to
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the fact that the mixtures of photocatalysts (ZnO+MnO2) supply additional oxidizing species
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and thereby increasing the rate of removal of dye. 4. Conclusions
The present work has illustrated the beneficial effects of cavity-bubbles induced
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oxidation using combination of UV and glass balls for removal of Methyl Violet 2B dye and has also established the effect of the various types and loadings of the photocatalysts. 1) The extent of removal using photo air induced cavitation is affected by the initial concentration and pH and hence the proper selection of optimized parameters increases the
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removal of the rate of MV 2B. Maximum extent of removal is obtained at optimized solution pH of 7.2 and initial concentration 10ppm. 2) The optimum loading of solid catalysts (TiO2, MnO2 and ZnO) is necessary to achieve an enhanced rate of removal of MV 2B dye using photo air induced oxidation using glass balls; as the excess loading of the solid catalyst may hinder the penetration of light into the
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reactor.
3) The optimum extent of removal (95%) of MV 2B dye was obtained using TiO2 with the
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optimal catalyst loading of 0.6 g/L. The sort of activities for superior removal of MV 2B is TiO2> MnO2>ZnO.
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4) It is also revealed that combination of two catalysts such as a combination of TiO2-MnO2
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gives maximum removal of MV 2B i.e. 96%.
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Thus, cavity-bubbles induced oxidation using UV and glass balls is an efficient tool for process
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intensification, which can overcome the problem of water deterioration by discharge of effluents containing harmful textile dye like Methyl Violet 2B. Also, it is a promising technique
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[15] E. Rokhina, E. Repo, J. Virkutyte, Comparative kinetic analysis of silent and ultrasound assisted catalytic wet peroxide oxidation of phenol, Ultrasonic Sonochemistry 17 (2010) 541– 546.
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[16] Z. Guo, R. Feng, J. Li, Z. Zheng, Y. Zheng, Degradation of 2,4-dinitrophenol by combining sonolysis and different additives, Journal of Hazardous Materials 158 (2008) 164– 169. [17] B. Banerjee, A. Khode, A. Patil, A. Mohod, P. Gogate, Studies on sonochemical decolorization of wastewaters containing Rhodamine 6G using ultrasonic bath at an operating
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[20]A. Francony, C. Petrier, Sonochemical degradation of carbon tetrachloride in aqueous
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Figure 1: Chemical Structure of Methyl Violet 2B
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Figure 2: Schematic representation of UV- cavity-bubbles oxidation reactor
IP T
List of Figures:
Figure 3: Effect of initial concentration on Methyl Violet (2B) using P UV- cavity-bubbles oxidation reactor (pH = 7)
U
Figure 4: Kinetic analysis for removal of Methyl Violet (2B) dye using UV- cavity-bubbles
A
N
oxidation reactor (pH = 7)
M
Figure 5: Effect of pH on Methyl Violet (2B) using UV- cavity-bubbles oxidation reactor (concentration = 10 ppm)
ED
Figure 6: Effect of catalyst loading on Methyl Violet (2B) using UV- cavity-bubbles oxidation
PT
reactor (pH = 7; concentration = 10 ppm; catalyst loading 0.2-0.8 g/L) Figure 7: Effect of combination of TiO2 and MnO2 on removal of Methyl Violet (2B) using
CC E
UV- cavity-bubbles oxidation reactor (pH = 7; concentration = 10 ppm; catalyst loading 0.6 g/L TiO2 and 0.8 g/L MnO2)
A
Figure 8: Effect of combination of TiO2 and ZnO on removal of Methyl Violet (2B) using UVcavity-bubbles oxidation reactor (pH = 7; concentration = 10 ppm; catalyst loading 0.6 g/L TiO2 and 0.6 g/L ZnO)
19
Fig.9: Effect of combination of MnO2 and ZnO on removal of Methyl Violet (2B) using UVcavity-bubbles oxidation reactor (pH = 7; concentration = 10 ppm; catalyst loading 0.8 g/L
A
CC E
PT
ED
M
A
N
U
SC R
IP T
MnO2 and 0.6 g/L ZnO)
20
SC R
IP T
Figures
A
CC E
PT
ED
M
A
N
U
Fig.1: Chemical Structure of Methyl Violet 2B
Fig. 2: Schematic representation of UV- cavity-bubbles oxidation reactor
21
70 10 PPM 20 PPM 30 PPM
50 40
IP T
30 20 10 0 0
20
40
60
80
100
SC R
Extent of Degradation,%
60
120
160
180
200
N
U
Reaction Time, min
140
reactor
1.2
20 ppm 30 ppm
=
7)
y = 0.0057x R² = 0.9918
PT
y = 0.0051x R² = 0.9711
0.6
CC E
Ln (C0/C)
0.8
ED
10 ppm 1
(pH
M
oxidation
A
Fig.3: Effect of initial concentration on Methyl Violet (2B) using UV- cavity-bubbles
0.4
y = 0.0029x R² = 0.984
A
0.2
0 0
20
40
60
80
100
120
140
160
180
200
Treatment Time, min
22
Fig. 4: Kinetic analysis for removal of Methyl Violet (2B) dye using UV- cavity-bubbles oxidation reactor (pH = 7)
100
IP T
90
70
SC R
60 50 40 30
U
Extent of Degradation, %
80
N
20
0 2
4
M
0
A
10
6
8
10
12
pH
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Fig.5: Effect of pH on Methyl Violet (2B) using UV- cavity-bubbles oxidation reactor
A
CC E
PT
(concentration = 10 ppm)
23
100 90
70 60 ZnO
50
TiO2
40
IP T
Extent of Degradation, %
80
MnO2
30
10 0 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
N
U
Catalyst Loading, g/L
SC R
20
A
Fig.6: Effect of catalyst loading on Methyl Violet (2B) using UV- cavity-bubbles oxidation
A
CC E
PT
ED
M
reactor (pH = 7; concentration = 10 ppm; catalyst loading 0.2-0.8 g/L)
24
97
96
95
IP T
Extent of Degradation %
98
94
SC R
93
92
U
91
MnO2
TiO2+MnO2
N
TiO2
A
Various Catalysts
M
Fig.7: Effect of combination of TiO2 and MnO2 on removal of Methyl Violet (2B) using
ED
UV- cavity-bubbles oxidation reactor (pH = 7; concentration = 10 ppm; catalyst loading
A
CC E
PT
0.6 g/L TiO2 and 0.8 g/L MnO2)
25
100
IP T
90
85
80
SC R
Extent of Degradation %
95
U
75
N
70 TiO2
ZnO
TiO2+ZnO
M
A
Various Catalysts
ED
Fig.8: Effect of combination of TiO2 and ZnO on removal of Methyl Violet (2B) using UV- cavity-bubbles oxidation reactor (pH = 7; concentration = 10 ppm; catalyst loading
A
CC E
PT
0.6 g/L TiO2 and 0.6 g/L ZnO)
26
96
94 93 92
IP T
Extent of Degradation %
95
91
89 MnO2
ZnO
SC R
90
MnO2 + ZnO
N
U
Various Catalysts
A
Fig.9: Effect of combination of MnO2 and ZnO on removal of Methyl Violet (2B) using
A
CC E
PT
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0.8 g/L MnO2 and 0.6 g/L ZnO)
M
UV- cavity-bubbles oxidation reactor (pH = 7; concentration = 10 ppm; catalyst loading
27
Table 1: Summary of the results Parameter
N
Cavity-
COD
Parameter
Cavity-bubbles
bubbles
Removal
induced
induced
(%)
oxidation
(Batch
Operation )
Operation )
Methyl Violet 2B
Patent Blue
dye removal (%)
dye
A 4
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Concentration,
Concentration,
ppm
ppm
20
57.38
30
52.24
10 36.6
20
N
21.21
30
A
10
58.45
40.3
37.62
pH
2.2
58.34
2.2
91.1
4.2
73.14
4.2
93.4
7.2
50
36.6
7.2
94.1
9.2
60.46
9.2
82.3
11.2
30.63
11.2
63.7
ED
M
pH
64.0
U
Initial
ZnO Loading
ZnO Loading
(g/L)
(g/L)
CC E
3
Initial
PT
2
(%)
(Continuous
removal (%) 1
photo- Removal
oxidation
V
COD
IP T
S
0.2
39.917
0.2
75.0
0.3
77.15
0.4
90.8
0.4
71
0.6
92.3
0.5
33.33
0.8
74.98
0.6
25.36
49.5
TiO2 Loading
TiO2 Loading
(g/L)
(g/L)
0.2
22.2
0.2
49.9
0.3
25.68
0.4
63.7
42.3
59.6
28
46.26
0.6
95.2
0.5
56.46
0.8
79.95
0.6
83.45
76.1
MnO2
MnO2
Loading
Loading
(g/L)
(g/L) 49.73
0.2
72
0.3
67.8
0.4
82.5
0.4
72.37
0.6
92.2
0.5
79
0.8
94.0
0.6
80.73
61.6
68.8
SC R
0.2
IP T
60.5
1.0
84.3
A
CC E
PT
ED
M
A
N
U
5
0.4
29
