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Polyacrylamide@Zr(IV) vanadophosphate nanocomposite: Ion exchange properties, antibacterial activity, and photocatalytic behavior
Accepted Manuscript Title: Polyacrylamide@Zr(IV) vanadophosphate nanocomposite: Ion exchange properties, antibacterial activity, and photocatalytic behavior Author: Gaurav Sharma Amit Kumar Mu. Naushad Deepak Pathania Mika Sillanp¨aa¨ PII: DOI: Reference:
S1226-086X(15)00456-6 http://dx.doi.org/doi:10.1016/j.jiec.2015.10.011 JIEC 2680
To appear in: Received date: Revised date: Accepted date:
21-8-2015 30-9-2015 11-10-2015
Please cite this article as: G. Sharma, A. Kumar, Mu. Naushad, D. Pathania, M. Sillanp¨aa¨ , Polyacrylamide@Zr(IV) vanadophosphate nanocomposite: Ion exchange properties, antibacterial activity, and photocatalytic behavior, Journal of Industrial and Engineering Chemistry (2015), http://dx.doi.org/10.1016/j.jiec.2015.10.011 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.
Polyacrylamide@Zr(IV) vanadophosphate nanocomposite: Ion exchange properties, antibacterial activity, and photocatalytic behavior
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School of Chemistry, Shoolini University, Solan -173212, Himachal Pradesh, India
Department of Chemistry, College of Science, Bld.#5, King Saud University, Riyadh, Saudi
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2
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Gaurav Sharma1*, Amit Kumar1, Mu. Naushad2*, Deepak Pathania1, Mika Sillanpää3
3
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Arabia
Laboratory of Green Chemistry, LUT School of Engineerings Science, Lappeenranta University
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of Technology, Sammonkatu 12, FI-50130 Mikkeli, Finland *Email: [email protected], [email protected], +919625310313, +919418807170
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Abstract: Polyacrylamide Zr(IV) vanadophosphate (PAM/ZVP) nanocomposite was synthesized via simple sol-gel method. The synthesized PAM/ZVP nanocomposite was studied for its ion
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exchange properties. The nanocomposite showed higher ion exchange capacity (IEC) compared to its inorganic counterpart Zr(IV) vanadophosphate(ZVP). The nanocomposite was well
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characterized using various techniques viz- TEM, SEM, XRD, and FTIR. The PAM/ZVP showed promising photocatalytic nature for degradation of congo red dye under sunlight. The enhanced dye remediation was observed as material behaved as adsorbent and photocatalyst simultaneously under coupled conditions in dye removal experiments. Thus, PAM/ZVP is a probable superior hybrid photo catalyst for dye waste treatment. Keywords: Nanocomposite; Ion exchange; Congo red; Photocatalyst; Polyacrylamide
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1. Introduction Environmental contamination poses a serious menace to not only human beings but also to flora
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and fauna, as it affects the entire ecosystem directly. The industrial development has been a gift to us in several ways but also has caused a nuisance to us in the form of pollution (air, water, or
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land). This has provoked the researchers all around the world to take notice of the methods used for the removal of pollutants, which prove to be lethal or carcinogenic for human beings [1-2].
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Henceforth, the severity of elegance of remediation methods has increased tremendously.
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Looking at the nanoscale has stimulated the progress and use of novel and economical technologies for adsorptive removal and catalytic degradation of contaminants as well as other
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ecological concerns [3-5]. A polymer-based nanocomposite (PNCs), which has the advantages of both polymers as well as nanoparticles have gained mounting attention in research in present
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times [6]. They present exceptional mechanical properties and compatibility due to their polymer
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matrix, the distinctive chemical physical properties [7-10]. In addition, the nanocomposites
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provide an efficient move toward overcoming the bottleneck troubles of nanoparticles in applications such as separation and recyclability. Wastewater containing persistent organic pollutants can root severe water pollution troubles in the form of reduced light penetration leading to hinders photosynthetic process in water bodies. It is very complicated to treat wastewater which has dye molecules, since the dyes are obstinate pollutants, resistant to aerobic digestion, and highly stable when uncovered to oxidizing agents [11, 12]. Another problem lies in the remediation of wastewaters having high concentrations of dyes. Thus, no single procedure is sufficient for ample treatment. Hence amalgamation of diverse processes is frequently used to attain the preferred water quality in the most inexpensive way. There is a necessity to build up new technologies that are effective and adequate in industrial 2 Page 2 of 30
use. It is now recognized that multifunctional materials behaving as adsorbent, ion exchangers and photocatalyst are of immense importance for waste water decontamination [13-16].
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The latest expansion in this discipline is the conversion of inorganic ion exchange materials into composite ion exchange ones. These composite materials are lucrative for the purpose of
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fabricating high performance or high functional polymeric systems that are probable to offer many possibilities, with superior thermal, chemical and physical stabilities and having excellent
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affinity for heavy metals, dye molecules signifying their utility in environmental applications
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[17-20]. Organic-inorganic nanocomposite ion exchange materials demonstrate the enhancement in there granulometric properties that makes them appropriate for the application in column
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operations. The adding up of an organic polymer also introduces the improved mechanical properties in composite ion exchange materials [21-23].
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Inorganic-organic nanocomposites possess chemical and physical properties that can be tuned by
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the synergetic association of organic and inorganic components at the nanometer scale.
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Nanocomposite ion exchangers have received much consideration because of their good IEC and diversified applications ranging from biomedical field to environmental remediation [24-26].The latest development in this field is potential application of these nanocomposite materials as catalyst in advance oxidation processes. The dual nature of these materials i.e., acting as adsorbent and photocatalyst is one of promising feature which motivates there use in adsoptional@photocatalytic remediation of organic pollutants such as dyes etc. The adsorption and photocatalysis are one off the effective and economical ways for waste water treatments. Thus,
present
need
is
to
fabricate
newer
nanocomposities
with
enhanced
adsoptional@photocatalytic activities.
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One of the largest uses of polyacrylamide is to coagulate and flocculate solids in a liquid, such as in the waste water treatment industry. In addition polyacrylamide products react with water to form meshes, physically trapping small particles into larger aggregated particles. In simple terms
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adsorptive nature of polyacrylamide make it potential counterpart of composite ion exchangers materials [27, 28]. Thus the present study discus the fabrication of Zr (IV) vanadophosphate
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embedded polyacrylamide matrix nanocomposite with enhanced adsoptional@photocatalytic
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effective antibacterial agent against bacterial pathogens.
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activity for photoremediation of congo red dye from water system and simultaneously acting as
2. Materials and Method
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2.1. Materials
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The materials used were acrylamide (CDH India), zirconium oxychloride (CDH India),
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orthophosphoric acid (CDH India), sodium vandate (CDH India), nitric acid (CDH India), hydrochloric acid (CDH India). All other chemicals used were of analytical grade and were used
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without further purification.
The solution of zirconium oxychloride (0.1 M) was prepared in 0.1 M HCl. The solution of acrylamide (0.5,1.0,1.5 and 2.0 M), 0.1 M solution of orthophosphoric acid, 0.1 M solution of sodium vandate were respectively prepared in demineralised water (DMW). 2.2. Synthesis of polyacrylamide zirconium (IV) vandophosphate (PAM/ZVP) The polyacrylamide based nanocomposite was prepared by mixing 0.1 M zirconium oxychloride, 0.1 M orthophosphoric acid, and 0.1M sodium vandate to varying concentration of acrylamide solution dropwise with continuous shaking [29]. The solution mixture pH was set between 0-1
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by adding up 0.1 M HNO3 and temperature was maintained between 30-40ºC. The mixture was stirred constantly for 3 h on the magnetic stirrer and was reserved overnight for digestion. The supernatant liquor was decanted; the precipitates were filtered and washed several times with
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DMW. The precipitates were dried at 50oC and then changed into H+ form by putting the material into 1 M HNO3 solution for 24 h. The precipitates were again filtered and washed with
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DMW several times to remove excess acid. The precipitates were then again dried in an oven at
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the sample with highest IEC was selected for further study.
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50ºC. Thus, various samples were synthesized by varying the concentration of acrylamide and
2.3. Ion exchange capacity
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The IEC of the nanocomposite was found by the column method [18]. The 10 g of the
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nanocomposite in H⁺ form (dipped in 0.1 N HNO3 for 24 h) was placed with glass wool
supported at the base of a glass column. 0.1 M NaNO₃ solution was passed slowly by adjusting
the effluent to a speed of 0.5 mL per minutes. The collected effluent was titrated with standard NaOH solution using phenolphthalein. The hydrogen ions released were then calculated. In
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general, the number of "active groups” or "functional groups" in an ion exchange material is equals to its total IEC.
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The IEC in meq/g was calculated as:
2.4. Thermal studies
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10 g of polyacrylamide Zr(IV) vandophosphate was heated at the different temperature in a muffle furnace for 1 h. The change in color and weight of the PAM/ZVP were noted after
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heating. The sample was cooled and the IEC was determined as discussed in section 2.4.
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2.5. Ion exchange capacity with different metal ions The ion exchange capacity of the PAM/ZVP was determined by the column method by using
different alkali and alkaline earth metal ions. In this 10 g of the PAM/ZVP nanocomposite in H⁺
form was used. The different metal ion solutions were passed slowly by adjusting the rate of effluent 0.5 mL per minutes. The IEC was determined as discussed in section 2.4. 2.6. pH titration 6 Page 6 of 30
The pH titration curves were determined by using the method given by Topp and Pepper, 1949 [30]. The 10 g of the material were taken in different flask which had equimolar solution of alkali metal chloride and their hydroxide in different volume ratio but the total volume was kept
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50 mL to sustain the ionic strength constant. The pH of the solution was noted after every 24 h
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for ten days at room temperature. The curves were obtained by plotting pH against the
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milliequivalents of OH⁻ ions added.
2.7. Characterization techniques
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The Fourier transforms infra-red spectra (FTIR) study of material was investigated by using KBr
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method. The X-ray diffraction (XRD) analysis was performed using manganese filtered Cu Kα
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radiation at 298 K. The morphological studies were done using scanning electron microscopy (SEM). The micrographs of material were obtained at diverse magnification. Energy-dispersive X-ray spectroscopy EDX was performed for the elemental analysis of a material. The particle size of the material was inferred using transmission electron microscopy (TEM). 2.8. Photocatalytic activity
The photocatalytic activity of synthesized polyacrylamide Zr (IV) vanadophosphate was demonstrated for the degradation of the Congo red dye. Congo red is an anionic azo dye having IUPAC
name
as
1-napthalenesulfonic
acid,
3,3-(4,4-biphenylenebis(azo))
bis
(4-
aminodisodium) and its structure is depicted as below: 7 Page 7 of 30
NH2 N N
SO3Na
N
NaO3S
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H2N
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N
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Congo Red
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Structure of congo red dye
The experiment was carried out in photoreactor using batch process. The 1.5 x10 -5 M solution of
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congo red dye was made in double distilled water. The 100 mg of polyacrylamide Zr (IV)
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vanadophosphate nanocomposite was added to 200 mL of dye solution and stirred continually.
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Whole arrangement was jacketed in thermostat to maintain constant temperature. The solution was exposed to solar light for photodegradation. At specific time interval aliquot of 2 mL
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solution was withdrawn. The concentration of the congo red in solution was determined by measuring its absorbance at 498 nm using UV-visible spectrophotometer. The degradation percentage was calculated by using following equation [31]:
Where, A0 is initial absorbance and At is the absorbance after time t of congo red dye. 2.9. Antibacterial activity
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The antimicrobial activity of PAM/ZVP material was tested against E.coli and S.aureous bacteria’s. The simple optical density method supported with disc diffusion was performed [6]. The bacteria’s were cultured on the nutrient broth (NB) at 37ºC for 24 h. The muller-hinton agar
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media was prepared and 30 mL of it was poured into petri discs and allowed to solidify. The petri discs were swabbed over the entire surface with bacterial strains. The discs were dipped in
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different concentrations solution of PAM/ZVP and were placed in petri discs. The ethanol
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solution was used as a negative control. The plates were kept at 37ºC for overnight incubation.
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After 24 h of incubation, inhibition zone was measured using measurement scale.
3.1. Synthesis & Ion exchange capacity
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3. Results and discussion
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Polyacrylamide Zr (IV) vanadophosphate (PAM/ZVP) was successfully synthesized by simple
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sol-gel method. The detail synthesis and proposed structure of PAM/ZVP is given in scheme-1. The various sample of nanocomposite were synthesized and Sample-5 was chosen for further
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studies due to its highest IEC among the samples. The nanocomposite showed a significantly higher IEC (1.8 meq g-1) in contrast to its inorganic counterpart (0.84 meq g-1). The enhancement in the IEC of the organic-inorganic PAM/ZVP compared to inorganic part (zirconium (IV) vanadophosphate) might be owing to the binding of polyacrylamide with inorganic zirconium (IV) vanadophosphate. The detailed results are presented in Table-1 [32]. The outcome of temperature on the stability of PAM/ZVP has been shown in Table-2. It is apparent that the IEC decreased with rise in temperature. The effect of the drying temperature on the IEC of the PAM/ZVP was studied by heating the PAM/ZVP for 1 h in a muffle furnace and subsequently the IEC was found after cooling the material at room temperature. The 9 Page 9 of 30
nanocomposite retained about 44.44% of its preliminary IEC up to 300ºC. This clearly indicates that the nanocomposite was stable at high temperature. The material maintained some of its
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initial mass and IEC by heating up to 500ºC. In order to examine the operational capacity of the nanocomposite, the IEC for some mono and
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divalent cations were investigated (Table-3). The order of sequence obtained was K+>Na+, and Ca2+< Ba2+, respectively. As, the hydrated ionic radii for alkali and alkaline earth metal ions
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decrease, the IEC increases [33]. Hence, it may be concluded that the ions with lesser hydrated
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radii enter the pores of the exchanger more easily, consequential the sorption for smaller ions was higher [34, 35]. The interesting feature shown by the PAM/ZVP is that IEC of alkaline earth
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metal ions was higher than alkali metal ions.
The pH titration curve for polyacrylamide Zr (IV) vandophosphate with NaOH-NaCl and KOH-
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KCl system has been shown in Fig.1. The figure indicates the bifunctional nature of the
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nanocomposite. The low initial pH values when no OH- ions were added clearly represents that
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polyacrylamide Zr (IV) vanadophosphate is strong cation exchanger. 3.2. Characterization
The FTIR spectrum Zr (IV) vanadophosphate and polyacrylamide Zr(IV) vanadophosphate is shown in Fig. 2. A peak at 3153 cm-1 indicates the existence of external water molecule [36, 37]. A broad peak seen at 1717cm-1 is the characteristics of the C=O stretching vibration of amide group [38, 39]. Whereas a broad peak at 3611cm-1 corresponds to N-H stretching which confirms the assimilation of acrylamide into the Zr(IV) vanadophosphate [39]. A broad band from 650500 cm-1 at is due to the existence of metal oxide linkage. A peak at 519 cm-1 is due to the Zr-OZr stretching [40]. The sharp peak at 1383cm-1 represents atmospheric CO2 presences [24]. The 10 Page 10 of 30
X-ray diffraction pattern of PAM/ZVP and ZVP nanocomposite was shown in Fig.3a and 3b. The low intensities peaks were observed which supported the semi-crystalline nature of the
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PAM/ZVP and the average crystallite size was found to be 25-32 nm. SEM microphotographs of the ZVP and PAM/ZVP (Fig.4a and 4b,c) clearly indicates the
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binding of organic material with inorganic matrix. The SEM pictures revealed that the surface morphology of nanocomposite materials is entirely dissimilar from inorganic matrix. The SEM
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pictures of ZVP shows smooth surface. While PAM/ZVP shows roughness and increased surface
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area due to the integration of polyacrylamide to the inorganic counterpart ZVP. The EDX (Fig. 4g) pattern shows the peaks for Zr, N, O, C, P, and V. This confirms the formation of
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nanocomposite material. The TEM micrograph (Fig.4d,e,f) shows that the particle size lies in the
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3.3. Dye removal
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range of 20-50 nm hence the synthesized PAM/ZVP is nanocomposite.
The photocatalytic remediation of congo red in the existence of PAM/ZVP as a catalyst was
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studied under solar irradiation. The experimental sets were exposed to two reaction conditions: equilibrium adsorption followed by photocatalysis and coupled adsorption and photocatalysis. Equilibrium adsorption followed by photocatalysis In first experimental set conditions, the dye solution containing PAM/ZVP was kept in dark to ascertain adsorption-desorption equilibrium. After that, the suspensions were exposed to natural solar light for advance photodegradation. Fig.5. depicts the removal of congo red by PAM/ZVP suspension in dark and solar light respectively. It was found that only 37% of the dye was adsorbed (Fig 5b) by PAM/ZVP followed by photo catalysis of dye in solar light. 96% of congo red dye was photodegraded (Fig 5d) in 4 h of irradiation. Thus, PAM/ZVP was improved 11 Page 11 of 30
photocatalytic agent than an adsorbent. On the other hand a 10% adsorption (Fig. 5a) and 64% photo catalysis (Fig. 5c) was achieved in the case of ZVP. When PAM/ZVP was irradiated with UV-Vis light electron-hole pairs were generated, which then reacts with water to generate
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hydroxyl and super-oxide radicals leading to disruption of the conjugation in dye molecules and possibly will also mineralize them. However photocatalytic activity was observed less in solar
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light (contains only 3–5% UV). In case of ZVP and PAM/ZVP, we achieved a 10% adsorption of
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congo red (Fig. 5a) and 37% (Fig. 5b) in 1 h when the suspensions sets were kept in dark. The adsorption is higher in case of PAM/ZVP as polyacrylamide gel shows exceptional adsorbing
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properties. The photoremediation progression depends on the amount of dye in bulk solution and on photocatalysts surface [41]. Thus, understanding the adsorption onto PAM/ZVP is critical for
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the detail study of photodegradation activity of the nanocomposite. The total dye amount at any
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time is given by following equation:
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Where, Cb and Cs are the amount of dye in bulk and on the surface of catalyst respectively. The concentration of adsorbed dye onto catalyst surface was found as [42].
Where V is the volume of solution and M is the mass of adsorbent. Cs, C0, and Ce were the amount of dye in solution, initial and at equilibrium respectively. Coupled adsorption and photocatalysis
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To study the outcome of adsorption onto the photodegradation behavior of ZVP and PAM/ZVP, the suspensions consisting of the photocatalysts and congo red dye were exposed to second reaction condition i.e. coupled adsorption and photocatalysis. Fig. 5e and 5f show the extent of
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degradation of congo red dye during coupled process in the presence of ZVP and PAM/ZVP respectively. A whopping 75% and 99% removal of congo red was achieved in 2 h of
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illumination with ZVP and PAM/ZVP respectively. The coupled adsorption and photocatalysis
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of dyes onto PAM/ZVP involves synchronized adsorption of the dye onto photocatalyst and simultaneous generation of electron hole pair from PAM/ZVP on absorption of solar light [31].
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The photoexcitation of organic dye plays a vital role in degradation. The electron transfer form photocatalyst to adsorbed dye molecules leads to formation of adsorbed dye radical cation on
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catalyst surface which further produces free oxygen radical anion thus carrying out the
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degradation of organic dye by disrupting of conjugation in its structure. Generally it is
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understood that photocatalytic competence can be improved by adsorbate adsorption onto the
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catalyst surface [43].
The mechanism for mineralization of congo red dye may possibly be as follows: PAM/ZVP + hʋ
→
PAM/ZVP (e−) + O2
PAM/ZVP (e−) + PAM/ZVP (h+) PAM/ZVP
+*O2−
PAM/ZVP (h+) + OH− → PAM/ZVP
+*OH
Congo red dye + *O2−
→
→ Degraded product
Congo red dye +*OH →
Degraded product
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The mechanism of coupled adsorptional@photocatalysis is also shown in detail in scheme-2. On the other hand it was assumed that once the dye is adsorbed onto PAM/ZVP and system is exposed to solar light, there is a synchronized production of an electron-hole pair in ZVP. This
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brings about the degradation of adsorbed dye more rapidly. There is a generation of OH* free
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radical which leads to disruption of conjugation [44-46].
The PAM/ZVP nanocomposite showed promising antimicrobial activity against E.coli and S.
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aureus (Fig.6). The material was found to be effective at every concentration, but the higher
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concentrations were more effective to strains of bacteria. The concentration of 350µg/mL and 400µg/mL were most effective against E.coli and S. aureus. The potential nano size particles
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clog the active transport channels present in the cell wall and hinder the cell activities [47, 48]. The presences of metals particles such as zirconium, vanadium, and phosphorus may lead to
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cellular poising thus effectively doing the cell lyses. The results indicated the inhibition zone of
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diameter 15 mm, 18 mm, 22 mm for E. coli and 14 mm, 16 mm, 20 mm for S. aureuswas
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reported by well diffusion method respectively showing the effectiveness of PAM/ZVP nanocomposite for inhibiting the growth of bacteria. Conclusion
Polyacrylamide Zr(IV) vanadophosphate nanocomposite was fabricated using simple sol-gel method. The synthesized PAM/ZVP nanocomposite showed high IEC. The synthesis was ascertained by adopting various characterization techniques like SEM, FTIR and XRD. The nanocomposite can bear fairly high temperature as it retains substantial IEC up to 400ºC and its bifunctional nature was proved by pH titration curves. The XRD studies showed that the ion exchange is semi-crystalline in nature. Congo red dye was successfully degraded by it after its
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exposure to sunlight for two h. It is clearly revealed that PAM/ZVP has a good dye removing potential under coupled adsorption and photodegradation. There is low adsorption and simultaneous photodegradation under coupled conditions and this is responsible for good
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photodegradation activity. Thus it implies that PAM/ZVP is a potential advanced nanocomposite photocatalyst for environmental remediation of dye pollutants and also possessed good
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antibacterial activity.
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Acknowledgements
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The authors acknowledge the School of Chemistry, Shoolini University, Solan for providing all necessary research facilities. One of the authors (M. Naushad) acknowledges King
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Saud University, Deanship of Scientific Research, College of Science Research Center for the
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d
Toxicol. Enviro. Chem. 97 (2015) 526-537.
[44] Wan-Kuen Jo, Thillai Sivakumar Natarajan, ACS Appl. Mater. Interfaces, DOI:
Ac ce p
10.1021/acsami.5b03935.
[45] Wan-Kuen Jo, N. Clament Sagaya Selvam, J. Hazard. Mater. 299 (2015) 462–470. [46] L.R. Hou, L. Lian, L.H. Zhang, J.Y. Li, Mater. Lett., 109 (2013) 306-308. [47] R. Katwal, H. Kaur, G. Sharma, M. Naushad, D Pathania, J. Ind. Eng. Chem. 31 (2015) 173184. [48] M.J. Hajipour, K.M. Fromm, A.A. Ashkarran, D.J. de Aberasturi, I.R. de Larramendi, T. Rojo, V. Serpooshan, W.J. Parak, M. Mahmoudi, Trends. Biotechnol. 30 (10) (2012) 499-511.
18 Page 18 of 30
ip t
B
C
D
Temperature in
O
C
Mixing
IEC
volume
(meq/g)
ratio 0.1
0.1
0.1
0
25-30
1:1:1:0
2
0.1
0.1
0.1
0.5
25-30
3
0.1
0.1
0.1
1.0
25-30
4
0.1
0.1
0.1
1.5
25-30
5
0.1
0.1
0.1
2.0
25-30
0.92
Yield (%)
Light yellow
15.5
1:1:1:1
1.2
Light yellow
17.5
1:1:1:1
1.3
Light yellow
19.0
1:1:1:1
1.5
Light yellow
20.5
1:1:1:1
1.8
Light yellow
21.5
d
M
an
1
Appearance
us
S. No. A
cr
Table1. Synthesis conditions for different samples of PAM/ZVP nanocomposite
te
A: 0.1 M zirconium oxychloride in DMW, B: 0.1 M Sodium vanadate in DMW,
Ac ce p
C: 0.1 M Orthophosphoric acid in DMW, D: Acrylamide of different molarities in DMW
19 Page 19 of 30
ip t cr
Heating
Initial
% Wt.
Color of
IEC for
Retention of
Temperature
Weight
loss of
sample
Na+ ion
IEC (%)
of
sample
0
( c)
Sample
After heating
after
(meq dry
heating
g-1)
M
(gms)
an
S. No
us
Table 2. Effect of temperature on IEC of PAM/ZVP
(%) 50
1
9.89
Light Yellow
1.8
100
2
100
1
13.6
Light Yellow
1.28
71.11
3
200
1
23.5
Light Yellow
0.80
44.44
4
300
1
31.6
Brown
0.54
30.00
5
400
1
42.9
Light Green
0.35
19.44
500
1
49.3
Light Green
0.24
13.33
te
Ac ce p
6
d
1
20 Page 20 of 30
ip t cr us Hydrated
1.33
2.32
1.24
0.97
2.76
1.43
1.43
5.90
1.50
1.06
6.30
1.50
Metal
pH of metal Ionic radii
ion taken
ion
A0
K⁺
6.20
2
Na⁺
6.7
3
Ba²⁺
6.2
4
Ca²⁺
te
d
1
M
S. No
an
Table3. IEC of PAM/ZVP with different metal ions
ionic radii A0
Ac ce p
6.5
IEC (meq/g)
21 Page 21 of 30
0
0
1 0
1 0
2 0
2 0
3
ip t
Acrylamide0
3 0
4 0
4 0
5 0
ZVP
Magnetic Stirrer
Magnetic Stirrer
Zirconium(IV)vandophosphate
d
M
an
H 3 PO 4 + NaVO 3 + ZrOCl 2 .8H 2 O
us
cr
5 0
Polyacrylamide zirconium (IV)vandophosphate
te
PAM/ZVP
Ac ce p
Magnetic Stirrer
NH 2 C
CH
NH 2 C
O
CH 2
ZVP
CH 2
ZVP
NH 2 C
CH
O
NH 2
O
CH 2
CH
C
O
CH 2
CH
NH 2 C CH
NH 2 C
O CH 2
CH
NH 2
C
O CH 2
CH ZVP
ZVP
NH 2
NH 2
NH 2
NH 2
CH
CH 2
C CH
O CH 2
C CH
O CH 2
CH
ZVP
O
Embedded Zirconium (IV)vandophosphate
NH 2
ZVP
C
Polyacrylamide Chains
CH 2
ZVP
ZVP
C
O
C
O CH 2
CH
O CH 2 n
Scheme-1 Synthesis and proposed structure of PAM/ZVP 22 Page 22 of 30
Adsorption Part
Coupled adsorptional@photocatalysisPhotocatalysis Part
CR
O
NH2 C
CH
NH2 C O
CH2
CH
-
ZVP
ZVP
CH
ZVP NH2 C O
CH2
C.B.e
CH
O2
cr
CR
NH2 C
CH2 ZVP
NH2 C
CH
ZVP NH2 C
CH
us
CR
-
e O
CH2
CR
CR
O
CH
ZVP
NH2 C O
CH2
ZVP CH
ZVP NH2 C O
CH2
CR
CR CH2
CR
O
CH
ZVP NH2 C O
CH2
ZVP
CH
OH*
-
e
CH2
ZVP
n
Ac ce p
CR
CH2
NH2 C
te
O
ZVP
CR
e
d
CH
-
CH
CR NH2 C
-
O2*
CH2
CR
CR NH2 C
CH2
O
CR
an
O
M
CR
ip t
+
Adsorbed Congo Red onto polyacrylamide Chains
+
V.B.h
H2O
Embedded Zirconium (IV)vandophosphate photodegrades the adsorbed and in solution Congo red dye
Scheme-2 Coupled adsorption and photocatalysis by PAM/ZVP
23 Page 23 of 30
12 NaOH-NaCl KOH-KCl
cr
8
us
pH
10
ip t
14
6
an
4
2
M
2 4
6
8
10
12
te
d
milli moles of OH ions added/g of exchanger
Fig.1. pH- titration curves of polyacrylamide Zr (IV) vanadophosphate with NaOH-NaCl and
Ac ce p
KOH-KCl
24 Page 24 of 30
35
ZVP PAM/ZVP
ip t
30
25
cr
20
%T
us
15
an
10
0 4000
3500
3000
M
5
2500
2000
1500
1000
500
-1
Ac ce p
te
d
Wavenumber (cm )
Fig.2. FTIR spectra of (a) ZVP (b) PAM-ZVP nanocomposite
25 Page 25 of 30
10
20
30
M
ip t
an
us
cr
Intensity (a.u.)
(a) PAM/ZVP (b) ZVP
40
50
60
70
80
te
d
2
Ac ce p
Fig.3. XRD patterns of (a) ZVP ion exchanger and (b) PAM-ZVP nanocomposite
26 Page 26 of 30
ip t cr us an M d
Fig.4. Scanning electron microphotographs ZVP (a) PAM/ZVP (b,c) Transmission electron
Ac ce p
te
microphotographs (d,e,f), EDX pattern (g) of PAM/ZVP nanocomposite
27 Page 27 of 30
100
(a) Adsorption on ZVP (b) Adsorption on PAM/ZVP
30
80
25
70
cr
50 40
us
15
60
(c) Photocatalysis in presences of ZVP (d) Photocatalysis in presences of PAM/ZVP (e) Coupled adsorptiona-Photocatalysis in presences of ZVP (f) Coupled adsorptiona-Photocatalysis in presences of PAM/ZVP
30
10
20
5
10
0 30 40 50 Time (min)
60
0 0
30
60
M
20
90
120
150
180
210
240
Time (min)
te
d
10
an
20
ip t
90
% Degradation
% Adsorption
35
Ac ce p
Fig.5.(a) Adsorption of Congo red dye onto ZVP in dark (b) Adsorption of Congo red dye onto PAM/ZVP in dark (c) Photocatalysis of Congo red in presence of ZVP on illumination (Initial concentration of MG 10−4M, pH = 6, temperature = 30 ± 0.5◦C) (d) Photocatalysis of Congo red dye in presence of PAM/ZVP on illumination (Initial concentration of MG 10−4M, pH = 6, temperature = 30 ± 0.5◦C) (e) Extent of removal of Congo red Dye by coupled adsorption and photocatalysis in presence of ZVP (f) Extent of removal of Congo red dye by coupled adsorption and photocatalysis in presence of PAM/ZVP (Initial concentration of MG 10−4M, pH = 6, temperature = 30 ± 0.5◦C).
28 Page 28 of 30
ip t cr us an M d te Ac ce p
Fig.6. Antibacterial activity of PAM/ZVP nanocomposite against (a) E.coli and (b) S. aureus
29 Page 29 of 30
Ac ce p
te
d
M
an
us
cr
ip t
Graphical Abstract
30 Page 30 of 30
S1226-086X(15)00456-6 http://dx.doi.org/doi:10.1016/j.jiec.2015.10.011 JIEC 2680
To appear in: Received date: Revised date: Accepted date:
21-8-2015 30-9-2015 11-10-2015
Please cite this article as: G. Sharma, A. Kumar, Mu. Naushad, D. Pathania, M. Sillanp¨aa¨ , Polyacrylamide@Zr(IV) vanadophosphate nanocomposite: Ion exchange properties, antibacterial activity, and photocatalytic behavior, Journal of Industrial and Engineering Chemistry (2015), http://dx.doi.org/10.1016/j.jiec.2015.10.011 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.
Polyacrylamide@Zr(IV) vanadophosphate nanocomposite: Ion exchange properties, antibacterial activity, and photocatalytic behavior
1
School of Chemistry, Shoolini University, Solan -173212, Himachal Pradesh, India
Department of Chemistry, College of Science, Bld.#5, King Saud University, Riyadh, Saudi
cr
2
ip t
Gaurav Sharma1*, Amit Kumar1, Mu. Naushad2*, Deepak Pathania1, Mika Sillanpää3
3
us
Arabia
Laboratory of Green Chemistry, LUT School of Engineerings Science, Lappeenranta University
an
of Technology, Sammonkatu 12, FI-50130 Mikkeli, Finland *Email: [email protected], [email protected], +919625310313, +919418807170
M
Abstract: Polyacrylamide Zr(IV) vanadophosphate (PAM/ZVP) nanocomposite was synthesized via simple sol-gel method. The synthesized PAM/ZVP nanocomposite was studied for its ion
te
d
exchange properties. The nanocomposite showed higher ion exchange capacity (IEC) compared to its inorganic counterpart Zr(IV) vanadophosphate(ZVP). The nanocomposite was well
Ac ce p
characterized using various techniques viz- TEM, SEM, XRD, and FTIR. The PAM/ZVP showed promising photocatalytic nature for degradation of congo red dye under sunlight. The enhanced dye remediation was observed as material behaved as adsorbent and photocatalyst simultaneously under coupled conditions in dye removal experiments. Thus, PAM/ZVP is a probable superior hybrid photo catalyst for dye waste treatment. Keywords: Nanocomposite; Ion exchange; Congo red; Photocatalyst; Polyacrylamide
1 Page 1 of 30
1. Introduction Environmental contamination poses a serious menace to not only human beings but also to flora
ip t
and fauna, as it affects the entire ecosystem directly. The industrial development has been a gift to us in several ways but also has caused a nuisance to us in the form of pollution (air, water, or
cr
land). This has provoked the researchers all around the world to take notice of the methods used for the removal of pollutants, which prove to be lethal or carcinogenic for human beings [1-2].
us
Henceforth, the severity of elegance of remediation methods has increased tremendously.
an
Looking at the nanoscale has stimulated the progress and use of novel and economical technologies for adsorptive removal and catalytic degradation of contaminants as well as other
M
ecological concerns [3-5]. A polymer-based nanocomposite (PNCs), which has the advantages of both polymers as well as nanoparticles have gained mounting attention in research in present
d
times [6]. They present exceptional mechanical properties and compatibility due to their polymer
te
matrix, the distinctive chemical physical properties [7-10]. In addition, the nanocomposites
Ac ce p
provide an efficient move toward overcoming the bottleneck troubles of nanoparticles in applications such as separation and recyclability. Wastewater containing persistent organic pollutants can root severe water pollution troubles in the form of reduced light penetration leading to hinders photosynthetic process in water bodies. It is very complicated to treat wastewater which has dye molecules, since the dyes are obstinate pollutants, resistant to aerobic digestion, and highly stable when uncovered to oxidizing agents [11, 12]. Another problem lies in the remediation of wastewaters having high concentrations of dyes. Thus, no single procedure is sufficient for ample treatment. Hence amalgamation of diverse processes is frequently used to attain the preferred water quality in the most inexpensive way. There is a necessity to build up new technologies that are effective and adequate in industrial 2 Page 2 of 30
use. It is now recognized that multifunctional materials behaving as adsorbent, ion exchangers and photocatalyst are of immense importance for waste water decontamination [13-16].
ip t
The latest expansion in this discipline is the conversion of inorganic ion exchange materials into composite ion exchange ones. These composite materials are lucrative for the purpose of
cr
fabricating high performance or high functional polymeric systems that are probable to offer many possibilities, with superior thermal, chemical and physical stabilities and having excellent
us
affinity for heavy metals, dye molecules signifying their utility in environmental applications
an
[17-20]. Organic-inorganic nanocomposite ion exchange materials demonstrate the enhancement in there granulometric properties that makes them appropriate for the application in column
M
operations. The adding up of an organic polymer also introduces the improved mechanical properties in composite ion exchange materials [21-23].
d
Inorganic-organic nanocomposites possess chemical and physical properties that can be tuned by
te
the synergetic association of organic and inorganic components at the nanometer scale.
Ac ce p
Nanocomposite ion exchangers have received much consideration because of their good IEC and diversified applications ranging from biomedical field to environmental remediation [24-26].The latest development in this field is potential application of these nanocomposite materials as catalyst in advance oxidation processes. The dual nature of these materials i.e., acting as adsorbent and photocatalyst is one of promising feature which motivates there use in adsoptional@photocatalytic remediation of organic pollutants such as dyes etc. The adsorption and photocatalysis are one off the effective and economical ways for waste water treatments. Thus,
present
need
is
to
fabricate
newer
nanocomposities
with
enhanced
adsoptional@photocatalytic activities.
3 Page 3 of 30
One of the largest uses of polyacrylamide is to coagulate and flocculate solids in a liquid, such as in the waste water treatment industry. In addition polyacrylamide products react with water to form meshes, physically trapping small particles into larger aggregated particles. In simple terms
ip t
adsorptive nature of polyacrylamide make it potential counterpart of composite ion exchangers materials [27, 28]. Thus the present study discus the fabrication of Zr (IV) vanadophosphate
cr
embedded polyacrylamide matrix nanocomposite with enhanced adsoptional@photocatalytic
an
effective antibacterial agent against bacterial pathogens.
us
activity for photoremediation of congo red dye from water system and simultaneously acting as
2. Materials and Method
M
2.1. Materials
d
The materials used were acrylamide (CDH India), zirconium oxychloride (CDH India),
te
orthophosphoric acid (CDH India), sodium vandate (CDH India), nitric acid (CDH India), hydrochloric acid (CDH India). All other chemicals used were of analytical grade and were used
Ac ce p
without further purification.
The solution of zirconium oxychloride (0.1 M) was prepared in 0.1 M HCl. The solution of acrylamide (0.5,1.0,1.5 and 2.0 M), 0.1 M solution of orthophosphoric acid, 0.1 M solution of sodium vandate were respectively prepared in demineralised water (DMW). 2.2. Synthesis of polyacrylamide zirconium (IV) vandophosphate (PAM/ZVP) The polyacrylamide based nanocomposite was prepared by mixing 0.1 M zirconium oxychloride, 0.1 M orthophosphoric acid, and 0.1M sodium vandate to varying concentration of acrylamide solution dropwise with continuous shaking [29]. The solution mixture pH was set between 0-1
4 Page 4 of 30
by adding up 0.1 M HNO3 and temperature was maintained between 30-40ºC. The mixture was stirred constantly for 3 h on the magnetic stirrer and was reserved overnight for digestion. The supernatant liquor was decanted; the precipitates were filtered and washed several times with
ip t
DMW. The precipitates were dried at 50oC and then changed into H+ form by putting the material into 1 M HNO3 solution for 24 h. The precipitates were again filtered and washed with
cr
DMW several times to remove excess acid. The precipitates were then again dried in an oven at
an
the sample with highest IEC was selected for further study.
us
50ºC. Thus, various samples were synthesized by varying the concentration of acrylamide and
2.3. Ion exchange capacity
M
The IEC of the nanocomposite was found by the column method [18]. The 10 g of the
Ac ce p
te
d
nanocomposite in H⁺ form (dipped in 0.1 N HNO3 for 24 h) was placed with glass wool
supported at the base of a glass column. 0.1 M NaNO₃ solution was passed slowly by adjusting
the effluent to a speed of 0.5 mL per minutes. The collected effluent was titrated with standard NaOH solution using phenolphthalein. The hydrogen ions released were then calculated. In
5 Page 5 of 30
general, the number of "active groups” or "functional groups" in an ion exchange material is equals to its total IEC.
an
us
cr
ip t
The IEC in meq/g was calculated as:
2.4. Thermal studies
M
10 g of polyacrylamide Zr(IV) vandophosphate was heated at the different temperature in a muffle furnace for 1 h. The change in color and weight of the PAM/ZVP were noted after
te
d
heating. The sample was cooled and the IEC was determined as discussed in section 2.4.
Ac ce p
2.5. Ion exchange capacity with different metal ions The ion exchange capacity of the PAM/ZVP was determined by the column method by using
different alkali and alkaline earth metal ions. In this 10 g of the PAM/ZVP nanocomposite in H⁺
form was used. The different metal ion solutions were passed slowly by adjusting the rate of effluent 0.5 mL per minutes. The IEC was determined as discussed in section 2.4. 2.6. pH titration 6 Page 6 of 30
The pH titration curves were determined by using the method given by Topp and Pepper, 1949 [30]. The 10 g of the material were taken in different flask which had equimolar solution of alkali metal chloride and their hydroxide in different volume ratio but the total volume was kept
ip t
50 mL to sustain the ionic strength constant. The pH of the solution was noted after every 24 h
cr
for ten days at room temperature. The curves were obtained by plotting pH against the
M
an
us
milliequivalents of OH⁻ ions added.
2.7. Characterization techniques
d
The Fourier transforms infra-red spectra (FTIR) study of material was investigated by using KBr
te
method. The X-ray diffraction (XRD) analysis was performed using manganese filtered Cu Kα
Ac ce p
radiation at 298 K. The morphological studies were done using scanning electron microscopy (SEM). The micrographs of material were obtained at diverse magnification. Energy-dispersive X-ray spectroscopy EDX was performed for the elemental analysis of a material. The particle size of the material was inferred using transmission electron microscopy (TEM). 2.8. Photocatalytic activity
The photocatalytic activity of synthesized polyacrylamide Zr (IV) vanadophosphate was demonstrated for the degradation of the Congo red dye. Congo red is an anionic azo dye having IUPAC
name
as
1-napthalenesulfonic
acid,
3,3-(4,4-biphenylenebis(azo))
bis
(4-
aminodisodium) and its structure is depicted as below: 7 Page 7 of 30
NH2 N N
SO3Na
N
NaO3S
cr
H2N
ip t
N
us
Congo Red
an
Structure of congo red dye
The experiment was carried out in photoreactor using batch process. The 1.5 x10 -5 M solution of
M
congo red dye was made in double distilled water. The 100 mg of polyacrylamide Zr (IV)
d
vanadophosphate nanocomposite was added to 200 mL of dye solution and stirred continually.
te
Whole arrangement was jacketed in thermostat to maintain constant temperature. The solution was exposed to solar light for photodegradation. At specific time interval aliquot of 2 mL
Ac ce p
solution was withdrawn. The concentration of the congo red in solution was determined by measuring its absorbance at 498 nm using UV-visible spectrophotometer. The degradation percentage was calculated by using following equation [31]:
Where, A0 is initial absorbance and At is the absorbance after time t of congo red dye. 2.9. Antibacterial activity
8 Page 8 of 30
The antimicrobial activity of PAM/ZVP material was tested against E.coli and S.aureous bacteria’s. The simple optical density method supported with disc diffusion was performed [6]. The bacteria’s were cultured on the nutrient broth (NB) at 37ºC for 24 h. The muller-hinton agar
ip t
media was prepared and 30 mL of it was poured into petri discs and allowed to solidify. The petri discs were swabbed over the entire surface with bacterial strains. The discs were dipped in
cr
different concentrations solution of PAM/ZVP and were placed in petri discs. The ethanol
us
solution was used as a negative control. The plates were kept at 37ºC for overnight incubation.
an
After 24 h of incubation, inhibition zone was measured using measurement scale.
3.1. Synthesis & Ion exchange capacity
M
3. Results and discussion
d
Polyacrylamide Zr (IV) vanadophosphate (PAM/ZVP) was successfully synthesized by simple
te
sol-gel method. The detail synthesis and proposed structure of PAM/ZVP is given in scheme-1. The various sample of nanocomposite were synthesized and Sample-5 was chosen for further
Ac ce p
studies due to its highest IEC among the samples. The nanocomposite showed a significantly higher IEC (1.8 meq g-1) in contrast to its inorganic counterpart (0.84 meq g-1). The enhancement in the IEC of the organic-inorganic PAM/ZVP compared to inorganic part (zirconium (IV) vanadophosphate) might be owing to the binding of polyacrylamide with inorganic zirconium (IV) vanadophosphate. The detailed results are presented in Table-1 [32]. The outcome of temperature on the stability of PAM/ZVP has been shown in Table-2. It is apparent that the IEC decreased with rise in temperature. The effect of the drying temperature on the IEC of the PAM/ZVP was studied by heating the PAM/ZVP for 1 h in a muffle furnace and subsequently the IEC was found after cooling the material at room temperature. The 9 Page 9 of 30
nanocomposite retained about 44.44% of its preliminary IEC up to 300ºC. This clearly indicates that the nanocomposite was stable at high temperature. The material maintained some of its
ip t
initial mass and IEC by heating up to 500ºC. In order to examine the operational capacity of the nanocomposite, the IEC for some mono and
cr
divalent cations were investigated (Table-3). The order of sequence obtained was K+>Na+, and Ca2+< Ba2+, respectively. As, the hydrated ionic radii for alkali and alkaline earth metal ions
us
decrease, the IEC increases [33]. Hence, it may be concluded that the ions with lesser hydrated
an
radii enter the pores of the exchanger more easily, consequential the sorption for smaller ions was higher [34, 35]. The interesting feature shown by the PAM/ZVP is that IEC of alkaline earth
M
metal ions was higher than alkali metal ions.
The pH titration curve for polyacrylamide Zr (IV) vandophosphate with NaOH-NaCl and KOH-
d
KCl system has been shown in Fig.1. The figure indicates the bifunctional nature of the
te
nanocomposite. The low initial pH values when no OH- ions were added clearly represents that
Ac ce p
polyacrylamide Zr (IV) vanadophosphate is strong cation exchanger. 3.2. Characterization
The FTIR spectrum Zr (IV) vanadophosphate and polyacrylamide Zr(IV) vanadophosphate is shown in Fig. 2. A peak at 3153 cm-1 indicates the existence of external water molecule [36, 37]. A broad peak seen at 1717cm-1 is the characteristics of the C=O stretching vibration of amide group [38, 39]. Whereas a broad peak at 3611cm-1 corresponds to N-H stretching which confirms the assimilation of acrylamide into the Zr(IV) vanadophosphate [39]. A broad band from 650500 cm-1 at is due to the existence of metal oxide linkage. A peak at 519 cm-1 is due to the Zr-OZr stretching [40]. The sharp peak at 1383cm-1 represents atmospheric CO2 presences [24]. The 10 Page 10 of 30
X-ray diffraction pattern of PAM/ZVP and ZVP nanocomposite was shown in Fig.3a and 3b. The low intensities peaks were observed which supported the semi-crystalline nature of the
ip t
PAM/ZVP and the average crystallite size was found to be 25-32 nm. SEM microphotographs of the ZVP and PAM/ZVP (Fig.4a and 4b,c) clearly indicates the
cr
binding of organic material with inorganic matrix. The SEM pictures revealed that the surface morphology of nanocomposite materials is entirely dissimilar from inorganic matrix. The SEM
us
pictures of ZVP shows smooth surface. While PAM/ZVP shows roughness and increased surface
an
area due to the integration of polyacrylamide to the inorganic counterpart ZVP. The EDX (Fig. 4g) pattern shows the peaks for Zr, N, O, C, P, and V. This confirms the formation of
M
nanocomposite material. The TEM micrograph (Fig.4d,e,f) shows that the particle size lies in the
te
3.3. Dye removal
d
range of 20-50 nm hence the synthesized PAM/ZVP is nanocomposite.
The photocatalytic remediation of congo red in the existence of PAM/ZVP as a catalyst was
Ac ce p
studied under solar irradiation. The experimental sets were exposed to two reaction conditions: equilibrium adsorption followed by photocatalysis and coupled adsorption and photocatalysis. Equilibrium adsorption followed by photocatalysis In first experimental set conditions, the dye solution containing PAM/ZVP was kept in dark to ascertain adsorption-desorption equilibrium. After that, the suspensions were exposed to natural solar light for advance photodegradation. Fig.5. depicts the removal of congo red by PAM/ZVP suspension in dark and solar light respectively. It was found that only 37% of the dye was adsorbed (Fig 5b) by PAM/ZVP followed by photo catalysis of dye in solar light. 96% of congo red dye was photodegraded (Fig 5d) in 4 h of irradiation. Thus, PAM/ZVP was improved 11 Page 11 of 30
photocatalytic agent than an adsorbent. On the other hand a 10% adsorption (Fig. 5a) and 64% photo catalysis (Fig. 5c) was achieved in the case of ZVP. When PAM/ZVP was irradiated with UV-Vis light electron-hole pairs were generated, which then reacts with water to generate
ip t
hydroxyl and super-oxide radicals leading to disruption of the conjugation in dye molecules and possibly will also mineralize them. However photocatalytic activity was observed less in solar
cr
light (contains only 3–5% UV). In case of ZVP and PAM/ZVP, we achieved a 10% adsorption of
us
congo red (Fig. 5a) and 37% (Fig. 5b) in 1 h when the suspensions sets were kept in dark. The adsorption is higher in case of PAM/ZVP as polyacrylamide gel shows exceptional adsorbing
an
properties. The photoremediation progression depends on the amount of dye in bulk solution and on photocatalysts surface [41]. Thus, understanding the adsorption onto PAM/ZVP is critical for
M
the detail study of photodegradation activity of the nanocomposite. The total dye amount at any
te
d
time is given by following equation:
Ac ce p
Where, Cb and Cs are the amount of dye in bulk and on the surface of catalyst respectively. The concentration of adsorbed dye onto catalyst surface was found as [42].
Where V is the volume of solution and M is the mass of adsorbent. Cs, C0, and Ce were the amount of dye in solution, initial and at equilibrium respectively. Coupled adsorption and photocatalysis
12 Page 12 of 30
To study the outcome of adsorption onto the photodegradation behavior of ZVP and PAM/ZVP, the suspensions consisting of the photocatalysts and congo red dye were exposed to second reaction condition i.e. coupled adsorption and photocatalysis. Fig. 5e and 5f show the extent of
ip t
degradation of congo red dye during coupled process in the presence of ZVP and PAM/ZVP respectively. A whopping 75% and 99% removal of congo red was achieved in 2 h of
cr
illumination with ZVP and PAM/ZVP respectively. The coupled adsorption and photocatalysis
us
of dyes onto PAM/ZVP involves synchronized adsorption of the dye onto photocatalyst and simultaneous generation of electron hole pair from PAM/ZVP on absorption of solar light [31].
an
The photoexcitation of organic dye plays a vital role in degradation. The electron transfer form photocatalyst to adsorbed dye molecules leads to formation of adsorbed dye radical cation on
M
catalyst surface which further produces free oxygen radical anion thus carrying out the
d
degradation of organic dye by disrupting of conjugation in its structure. Generally it is
te
understood that photocatalytic competence can be improved by adsorbate adsorption onto the
Ac ce p
catalyst surface [43].
The mechanism for mineralization of congo red dye may possibly be as follows: PAM/ZVP + hʋ
→
PAM/ZVP (e−) + O2
PAM/ZVP (e−) + PAM/ZVP (h+) PAM/ZVP
+*O2−
PAM/ZVP (h+) + OH− → PAM/ZVP
+*OH
Congo red dye + *O2−
→
→ Degraded product
Congo red dye +*OH →
Degraded product
13 Page 13 of 30
The mechanism of coupled adsorptional@photocatalysis is also shown in detail in scheme-2. On the other hand it was assumed that once the dye is adsorbed onto PAM/ZVP and system is exposed to solar light, there is a synchronized production of an electron-hole pair in ZVP. This
ip t
brings about the degradation of adsorbed dye more rapidly. There is a generation of OH* free
cr
radical which leads to disruption of conjugation [44-46].
The PAM/ZVP nanocomposite showed promising antimicrobial activity against E.coli and S.
us
aureus (Fig.6). The material was found to be effective at every concentration, but the higher
an
concentrations were more effective to strains of bacteria. The concentration of 350µg/mL and 400µg/mL were most effective against E.coli and S. aureus. The potential nano size particles
M
clog the active transport channels present in the cell wall and hinder the cell activities [47, 48]. The presences of metals particles such as zirconium, vanadium, and phosphorus may lead to
d
cellular poising thus effectively doing the cell lyses. The results indicated the inhibition zone of
te
diameter 15 mm, 18 mm, 22 mm for E. coli and 14 mm, 16 mm, 20 mm for S. aureuswas
Ac ce p
reported by well diffusion method respectively showing the effectiveness of PAM/ZVP nanocomposite for inhibiting the growth of bacteria. Conclusion
Polyacrylamide Zr(IV) vanadophosphate nanocomposite was fabricated using simple sol-gel method. The synthesized PAM/ZVP nanocomposite showed high IEC. The synthesis was ascertained by adopting various characterization techniques like SEM, FTIR and XRD. The nanocomposite can bear fairly high temperature as it retains substantial IEC up to 400ºC and its bifunctional nature was proved by pH titration curves. The XRD studies showed that the ion exchange is semi-crystalline in nature. Congo red dye was successfully degraded by it after its
14 Page 14 of 30
exposure to sunlight for two h. It is clearly revealed that PAM/ZVP has a good dye removing potential under coupled adsorption and photodegradation. There is low adsorption and simultaneous photodegradation under coupled conditions and this is responsible for good
ip t
photodegradation activity. Thus it implies that PAM/ZVP is a potential advanced nanocomposite photocatalyst for environmental remediation of dye pollutants and also possessed good
cr
antibacterial activity.
us
Acknowledgements
an
The authors acknowledge the School of Chemistry, Shoolini University, Solan for providing all necessary research facilities. One of the authors (M. Naushad) acknowledges King
M
Saud University, Deanship of Scientific Research, College of Science Research Center for the
Ac ce p
References
te
d
support.
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ip t
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[11] V.K. Gupta, T.A. Saleh, D. Pathania, B.S. Rathore, G. Sharma, Ionics. 21 (2015) 1787-
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[16] W. Cui, W. An, L. Liu, J. Hu, Y. Liang, J. Solid State Chem., 215 (2014) 94-101. [17] G. Sharma, D. Pathania, M. Naushad, Chem. Eng. J. 251 (2014) 413-421. [18] B.S. Rathore, G. Sharma, D. Pathania, SMC Bulletin 4 (2013) 11-16. [19] S.A. Nabi, M. Naushad, Chem. Eng. J. 158 (2015) 100-107. [20] S.A. Nabi, M. Naushad, A.M. Khan, Coll. & Surf. A: Phys. & Eng. Aspects 280 (2006) 66-70. [21] G. Sharma, D. Pathania, M. Naushad, Ionics. 21(2015)1045-1055. [22] S.A. Nabi, Mu. Naushad, Coll. Surf. A: Phys. Eng. Aspects 316 (2008) 217–225. [23] G. Sharma, D. Pathania, M. Naushad, J. Ind. Eng. Chem., 20 (2014) 4482-4490. 16 Page 16 of 30
[24] D. Pathania, G. Sharma, R. Thakur, Chem. Eng. J. 267(2015) 235-244. [25]M. Naushad, Chem. Eng. J. 235 (2014) 100-108.
ip t
[26] B.S. Rathore, G. Sharma, D. Pathania, V.K. Gupta, Carbohydr. Polym. 103 (2014) 221-227.
cr
[27] M. Islam, R. Patel, J. Hazard Mater. 156 (2008) 509-520.
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53(2014)15549-15560.
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[32] D. Pathania, G. Sharma, M. Naushad, V. Priya, Desal. Wat. Treat. (2015) In press, DOI:10.1080/19443994.2014.967731. [33] A.M. Khan, S.A. Ganai, S.A. Nabi, Coll. and Surf. A: Physicochem. Eng. Aspects, 337 (2009) 141-145.
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ip t
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cr
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18 Page 18 of 30
ip t
B
C
D
Temperature in
O
C
Mixing
IEC
volume
(meq/g)
ratio 0.1
0.1
0.1
0
25-30
1:1:1:0
2
0.1
0.1
0.1
0.5
25-30
3
0.1
0.1
0.1
1.0
25-30
4
0.1
0.1
0.1
1.5
25-30
5
0.1
0.1
0.1
2.0
25-30
0.92
Yield (%)
Light yellow
15.5
1:1:1:1
1.2
Light yellow
17.5
1:1:1:1
1.3
Light yellow
19.0
1:1:1:1
1.5
Light yellow
20.5
1:1:1:1
1.8
Light yellow
21.5
d
M
an
1
Appearance
us
S. No. A
cr
Table1. Synthesis conditions for different samples of PAM/ZVP nanocomposite
te
A: 0.1 M zirconium oxychloride in DMW, B: 0.1 M Sodium vanadate in DMW,
Ac ce p
C: 0.1 M Orthophosphoric acid in DMW, D: Acrylamide of different molarities in DMW
19 Page 19 of 30
ip t cr
Heating
Initial
% Wt.
Color of
IEC for
Retention of
Temperature
Weight
loss of
sample
Na+ ion
IEC (%)
of
sample
0
( c)
Sample
After heating
after
(meq dry
heating
g-1)
M
(gms)
an
S. No
us
Table 2. Effect of temperature on IEC of PAM/ZVP
(%) 50
1
9.89
Light Yellow
1.8
100
2
100
1
13.6
Light Yellow
1.28
71.11
3
200
1
23.5
Light Yellow
0.80
44.44
4
300
1
31.6
Brown
0.54
30.00
5
400
1
42.9
Light Green
0.35
19.44
500
1
49.3
Light Green
0.24
13.33
te
Ac ce p
6
d
1
20 Page 20 of 30
ip t cr us Hydrated
1.33
2.32
1.24
0.97
2.76
1.43
1.43
5.90
1.50
1.06
6.30
1.50
Metal
pH of metal Ionic radii
ion taken
ion
A0
K⁺
6.20
2
Na⁺
6.7
3
Ba²⁺
6.2
4
Ca²⁺
te
d
1
M
S. No
an
Table3. IEC of PAM/ZVP with different metal ions
ionic radii A0
Ac ce p
6.5
IEC (meq/g)
21 Page 21 of 30
0
0
1 0
1 0
2 0
2 0
3
ip t
Acrylamide0
3 0
4 0
4 0
5 0
ZVP
Magnetic Stirrer
Magnetic Stirrer
Zirconium(IV)vandophosphate
d
M
an
H 3 PO 4 + NaVO 3 + ZrOCl 2 .8H 2 O
us
cr
5 0
Polyacrylamide zirconium (IV)vandophosphate
te
PAM/ZVP
Ac ce p
Magnetic Stirrer
NH 2 C
CH
NH 2 C
O
CH 2
ZVP
CH 2
ZVP
NH 2 C
CH
O
NH 2
O
CH 2
CH
C
O
CH 2
CH
NH 2 C CH
NH 2 C
O CH 2
CH
NH 2
C
O CH 2
CH ZVP
ZVP
NH 2
NH 2
NH 2
NH 2
CH
CH 2
C CH
O CH 2
C CH
O CH 2
CH
ZVP
O
Embedded Zirconium (IV)vandophosphate
NH 2
ZVP
C
Polyacrylamide Chains
CH 2
ZVP
ZVP
C
O
C
O CH 2
CH
O CH 2 n
Scheme-1 Synthesis and proposed structure of PAM/ZVP 22 Page 22 of 30
Adsorption Part
Coupled adsorptional@photocatalysisPhotocatalysis Part
CR
O
NH2 C
CH
NH2 C O
CH2
CH
-
ZVP
ZVP
CH
ZVP NH2 C O
CH2
C.B.e
CH
O2
cr
CR
NH2 C
CH2 ZVP
NH2 C
CH
ZVP NH2 C
CH
us
CR
-
e O
CH2
CR
CR
O
CH
ZVP
NH2 C O
CH2
ZVP CH
ZVP NH2 C O
CH2
CR
CR CH2
CR
O
CH
ZVP NH2 C O
CH2
ZVP
CH
OH*
-
e
CH2
ZVP
n
Ac ce p
CR
CH2
NH2 C
te
O
ZVP
CR
e
d
CH
-
CH
CR NH2 C
-
O2*
CH2
CR
CR NH2 C
CH2
O
CR
an
O
M
CR
ip t
+
Adsorbed Congo Red onto polyacrylamide Chains
+
V.B.h
H2O
Embedded Zirconium (IV)vandophosphate photodegrades the adsorbed and in solution Congo red dye
Scheme-2 Coupled adsorption and photocatalysis by PAM/ZVP
23 Page 23 of 30
12 NaOH-NaCl KOH-KCl
cr
8
us
pH
10
ip t
14
6
an
4
2
M
2 4
6
8
10
12
te
d
milli moles of OH ions added/g of exchanger
Fig.1. pH- titration curves of polyacrylamide Zr (IV) vanadophosphate with NaOH-NaCl and
Ac ce p
KOH-KCl
24 Page 24 of 30
35
ZVP PAM/ZVP
ip t
30
25
cr
20
%T
us
15
an
10
0 4000
3500
3000
M
5
2500
2000
1500
1000
500
-1
Ac ce p
te
d
Wavenumber (cm )
Fig.2. FTIR spectra of (a) ZVP (b) PAM-ZVP nanocomposite
25 Page 25 of 30
10
20
30
M
ip t
an
us
cr
Intensity (a.u.)
(a) PAM/ZVP (b) ZVP
40
50
60
70
80
te
d
2
Ac ce p
Fig.3. XRD patterns of (a) ZVP ion exchanger and (b) PAM-ZVP nanocomposite
26 Page 26 of 30
ip t cr us an M d
Fig.4. Scanning electron microphotographs ZVP (a) PAM/ZVP (b,c) Transmission electron
Ac ce p
te
microphotographs (d,e,f), EDX pattern (g) of PAM/ZVP nanocomposite
27 Page 27 of 30
100
(a) Adsorption on ZVP (b) Adsorption on PAM/ZVP
30
80
25
70
cr
50 40
us
15
60
(c) Photocatalysis in presences of ZVP (d) Photocatalysis in presences of PAM/ZVP (e) Coupled adsorptiona-Photocatalysis in presences of ZVP (f) Coupled adsorptiona-Photocatalysis in presences of PAM/ZVP
30
10
20
5
10
0 30 40 50 Time (min)
60
0 0
30
60
M
20
90
120
150
180
210
240
Time (min)
te
d
10
an
20
ip t
90
% Degradation
% Adsorption
35
Ac ce p
Fig.5.(a) Adsorption of Congo red dye onto ZVP in dark (b) Adsorption of Congo red dye onto PAM/ZVP in dark (c) Photocatalysis of Congo red in presence of ZVP on illumination (Initial concentration of MG 10−4M, pH = 6, temperature = 30 ± 0.5◦C) (d) Photocatalysis of Congo red dye in presence of PAM/ZVP on illumination (Initial concentration of MG 10−4M, pH = 6, temperature = 30 ± 0.5◦C) (e) Extent of removal of Congo red Dye by coupled adsorption and photocatalysis in presence of ZVP (f) Extent of removal of Congo red dye by coupled adsorption and photocatalysis in presence of PAM/ZVP (Initial concentration of MG 10−4M, pH = 6, temperature = 30 ± 0.5◦C).
28 Page 28 of 30
ip t cr us an M d te Ac ce p
Fig.6. Antibacterial activity of PAM/ZVP nanocomposite against (a) E.coli and (b) S. aureus
29 Page 29 of 30
Ac ce p
te
d
M
an
us
cr
ip t
Graphical Abstract
30 Page 30 of 30