ES on Degradation of Congo Red

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ScienceDirect Materials Today: Proceedings 19 (2019) 1333–1339

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ICCSE 2018

Photocatalytic Study of ZnO-CuO/ES on Degradation of Congo Red Nurul Fahmi Khairol, Norzahir Sapawe*, Mohamed Danish Universiti Kuala Lumpur Branch Campus Malaysian Institute of Chemical and Bioengineering Technology (UniKL MICET), Lot 1988 Vendor City, Taboh Naning, 78000 Alor Gajah, Melaka, Malaysia

Abstract A preliminary photocatalytic testing toward 1 wt.% ZnO–1 wt.% CuO/ES catalyst was conducted, and compared with 1 wt.% ZnO–ES, 1 wt.% CuO–ES, 1 wt.% ZnO–1 wt.% CuO, ZnO, CuO, and ES. The catalysts were then characterized via Fourier transform infrared spectroscopy (FTIR) to determine the functional group which contribute to the interaction occurs between semiconductors and eggshell (ES). About 83% of Congo red was degraded at pH 5 within 4 hrs of visible light irradiation under 1 g L-1 of 1 wt.% ZnO–1 wt.% CuO/ES catalyst. © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Chemical Sciences and Engineering: Advance and New Materials, ICCSE 2018. Keywords: ZnO-CuO/ES, Electrochemical, Photodegration, Congo Red

1. Introduction Congo red is categorized as azo dye and one of organic substances that can contribute to water pollution as widely utilize in textiles, paper, leathers, additives and analytical chemistry [1]. Overall, over 7 × 105 tons of dyestuff per year were generated and approximately more than 100, 000 commercial dyes can be acquired [2]. Proper treatment is very essential as dyes are carcinogenic, mutagenic, [3] and visible even in low concentration and prevent dissolution of oxygen occur as well become barrier for sunlight to penetrate through waterbodies at once endanger the aquatic life [4-6]. * Corresponding author. Tel.: +6013-5757795 E-mail address: [email protected]

2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Chemical Sciences and Engineering: Advance and New Materials, ICCSE 2018.

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Chemical and biological oxidation, adsorption, coagulation and flocculation, electrochemical, ion exchange, membrane separation and advance oxidation processes (AOPs) are available technologies that can be applying to eliminate organic compound in wastewater especially dyes [7]. AOPs is the most preferable among all these technologies because its advantages in term of cost which relatively inexpensive, conduct in low temperature, and has potential to convert the organic pollutants into harmless CO2 and water [8]. Photocatalyst main component that in AOPs which constructed from semiconductors for examples, TiO2, Ag, WO3, ZnO, ZrO2, SnO2, and CuO [1,4, 9-13]. For the semiconductor, TiO2 and ZnO are conventionally used as catalysts in AOPs. Not only have similar band gap energy as TiO2, ZnO (3.2 eV) seem have several other privileges compared to TiO2 which are cheaper and relatively large quantum efficiency [14]. To improve performance of photocatalytic degradation, the band gap must be lessening and extending the absorbance range to visible region leading to electron–hole pair separation under irradiation which can be achieve by coupling two semiconductors [15]. Previously, there are several that used coupling two semiconductors have been reported such as Au-ZnO, PtZnO, Fe2O3/TiO2, Ag/TiO2, and SnO2-ZnO [14,16-19]. The CuO have superior features of narrow band gap (1.7 eV), non-toxicity, chemical stability, high thermal and electrical conductivities, natural abundance as well as environmental benignity which drawn implementation of this p-type semiconductors in various field [15,20-22]. Recently, there several successful syntheses of ZnO-CuO catalyst by using co-precipitation method, reflux condensation, template assisted growth, thermal evaporation, thermal decomposition, and wet impregnation have been reported but there are limitations [15,20-25]. In addition, previous study mostly focusses on structure shape of the ZnO-CuO and completely dependent on semiconductor only that are costly. Introduce of support can help reduce the utilization of semiconductor amount. Moreover, ZnOelec, EGZnO/HY, CuO/HY, ZnO/MSN, EGZrO2/HY, and EGZrO2–EGZnO/HY catalysts were previously reported used a simple and rapid electrochemical method give nanosized oxide semiconductor and show synergistic correlation of semiconductor and support consequently increased photocatalytic degradation efficiency [2,3,7,26-38]. Hence, this study was proposed eggshell (ES) supported ZnO-CuO generated through a simple electrochemical method and tested for the photocatalytic degradation of Congo red dye. The issue regarding water pollution can be overcome as well new discovery especially on the interaction of semiconductor and support will be achieved. 2. Experimental procedures 2.1. Materials and method Chicken eggshell (ES) were utilized as support for semiconductors and was collected from nearest farm, market, and stall. Plate cells of Platinum (Pt), Zinc (Zn), and Copper (Cu) (Nilaco Metal, Japan) have been used as electrodes. N,N-dimethylformamide (DMF) (Merck), and naphthalene (Fluka) act as solvent and mediator respectively. For adjustment of pH of sample solution, hydrochloric acid (HCl) and sodium hydroxide (NaOH) were used and Congo red was used as chosen organic contaminant. 2.2. Catalyst preparation The collected chicken egg shell (ES) were immersed in the water overnight to eliminate the impurities and followed with dried in oven at 80 ℃ for 24 hrs. Then, the ES were crushed into pieces and grinded. To produce a powder consistent size of 355-600 μm, the ES were sieved and once again oven-dried at 100 ℃ until the weight were constant. Lastly, the resultant ES were stored in a container. A one-compartment cell was setup with pair of electrodes of Pt plate (2 × 2 cm2) and Zn plate (2 × 2 cm2) as cathode and anode respectively immersed in a 10 mL of DMF solution mixed with 0.1 M tetraethylammonium perchlorate (TEAP), 6 mmol naphthalene 15 g of ES. Next, the electrolysis was carrying out under normal atmosphere at 273 K and 120 mA cm-2 of constant current density was applied [2,3,7,26-38]. The produced mixture was impregnated, and oven dried at 378 K overnight. Finally, the calcination process take place at 823 K for 3 hrs to yield grey powder of 1 wt% ZnO/ES catalyst. The steps were repeated for 1 wt% CuO/ES catalyst but, the anode electrodes of Zn plate and Cu plate were used alternately for 1 wt% ZnO-1 wt% CuO/ES catalyst. The run time for

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required to yield 1 wt% ZnO and 1 wt% CuO precursor of 1 wt% ZnO/ES, 1 wt% CuO/ES and 1 wt% ZnO-1 wt% CuO/ES catalysts approximately 932 s and 958 s respectively. The preparation of bare ZnO, CuO, and 1:1 ZnO-CuO also followed same procedures in absence of ES. The required weight percent of the ZnO supported on ES and the time required for the complete electrolysis was calculated based on Faraday’s law of electrolysis [2,3,7,26-38]. 𝑡=

𝑧×𝑛

(1)

where t = total time for the constant current applied (s); F = 96,486 C mol−1, which is the Faraday constant; I = the electric current applied; z = the valency number of ions of substances (electrons transferred per ion); and n = the number of moles of Zn (no of moles, liberated n = m/M). 2.3. Characterization The functional groups of catalysts were identified using a Perkin Elmer Spectrum RX 1 Fourier-transform infrared (FT-IR) Spectrometer using the KBr method with a scan range of 400–4000 cm−1. 2.4. Photocatalytic testing The photodegradation of Congo red (CR) was tested on catalysts using batch reactor where placed in chamber that has been equipped with fluorescent lamp and overlaid with aluminium foil on the inner surface. The adsorptiondesorption was achieved as 0.1 g of catalysts constantly stirred into 100 mL of 10 mg L-1 CR aqueous solution under dark condition with pH 5 at room temperature for 1 hr before illuminated with visible light for 4 hrs. The residual CR concentration at specific time intervals determined by scan 2.5 mL of collected and centrifuged sample through a UV-vis spectrophotometer Lambda EZ 210 with 498 nm of characteristic adsorption band. The degradation percentage was calculated as follow, 𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑜𝑓 𝐶𝑅 𝑑𝑒𝑔𝑟𝑎𝑑𝑎𝑡𝑖𝑜𝑛 % =

× 100

(2)

where C0 represents the initial concentration (mg L-1) and Ct denotes a variable concentration (mg L-1). 3. Results and discussion 3.1. Characterization 3.1.1. Vibrational spectroscopy FTIR spectroscopy can determine unique vibrational behavior for each chemical bond contain in materials. Hence, the generated catalysts have gone through FTIR analysis. For all catalyst, the broad band approximately at 3427 cm-1 related to moisture of H2O molecules absorbed on the catalysts surface respectively as shown Fig. 1. At 1547 cm-1, peaks appeared associated to vibration distortion of O-H group on the surface of ZnO, CuO, and ZnOCuO catalysts. Besides, ZnO, and CuO catalysts produced peaks at 486 cm-1 and 529 cm-1 represent Zn-O [39-42] and Cu-O [43-45] vibration respectively. ZnO-CuO catalyst peak identified at 444 cm-1 which broader and less intensity compared bare ZnO catalysts peaks at 486 cm-1 exhibits coupling of ZnO and CuO was successful. The peak of metal-O vibration does not appear after the ZnO and CuO introduced on ES due to small amount of metal loading. Meanwhile, for ES catalysts, a peak was determined at 2516 cm-1 may correspond to hydride vibration [46] and a strong peak at around 1420 cm-1 significantly attributed carbonate minerals within the eggshell matrix [47,48]. There are also two peaks resulted at 876 cm-1 and 712 cm-1 in parallel with the in-plane deformation and out-plane deformation modes of calcium carbonate respectively [47-49]. The peaks at 2516 cm-1, 1420 cm-1, 876 cm-1

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Intensity (a.u.)

and 712 cm-1 shows the correlation between the semiconductor and ES as their intensity drop after ZnO and CuO was deposited on to ES.

Bare ZnO Bare CuO 1:1 ZnO-CuO ES 1 wt% ZnO-ES 1 wt% CuO-ES 1 wt% ZnO-1 wt% CuO/ES 4000

3400

2800 2200 1600 Wavenumber (cm-1 )

1000

400

Fig. 1 FT-IR spectra of catalysts 3.2. Photocatalytic testing The photocatalytic activity of 1 wt% ZnO-1 wt% CuO/ES was attempt with Congo red (CR) dye. The adsorption-desorption equilibrium of all catalysts was accomplished within 1 hr under dark condition. The uptake percentage of CR by adsorption for bare ZnO catalyst (67.37 %) is the highest followed by 1:1 ZnO-CuO (66.20 %), 1 wt% ZnO-1 wt% CuO/ES (39.20 %), 1 wt% CuO/ES (37.09 %), bare CuO (14.55 %), bare ES (13.38 %), and 1 wt% ZnO/ES (11.74 %) as illustrated in Fig. 2. After visible light illumination in 4 hrs, bare ZnO and bare CuO catalysts degrade 81.29 % and 81.87 % of CR two times higher than bare ES (37.67%) catalyst attributed to high photosensivity. Supports material mostly have mesoporous structure, low polar surface and a large surface area, also a high adsorption capacity. In this case, the CR adsorption by bare ES catalyst quite low because was conducted at pH 5 of aqueous solution. As CR is anionic dye, the pHZPC of ES is 6.37 [50], and calcium corbonate (CaCO3) was determined in ES, the adsorption will be favourable at strong acidic condition. The 1 wt% ZnO-1 wt% CuO/ES (83.01 %) give highest removal of CR but only slightly higher compared to others. Meanwhile, 1 wt% ZnO/ES (39.89 %) and 1 wt% CuO/ES (80.22 %) can be seen decline in photodegradation of CR as metals introduce to support probably due the small amount of metal loading. In pros, the ratio of metal use for supported 1 wt% metal to bare catalyst is 1 to 99.

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100 Dark

Removal percentage (%)

80

Visible light

60

40

20

0

Catalysts

Fig. 2 Catalysts performance for CR [pH =5, C0 = 10 mg L-1, W = 1 g L-1] 4. Conclusion Overall, the photocatalytic degradation of CR became more effective with coupling of ZnO and CuO supported on ES as indicated by 1 wt% ZnO-1 wt% CuO/ES catalyst. Even low quantity of metals utilization for 1 wt% ZnO-1 wt% CuO/ES catalyst, the CR removal can reach as same as bare metals that used a lot of metals quantity. The use ES as support are facile, green, and environmentally friendly. For recommendation, the catalysts will undergo several characterizations other than FTIR such as XRD, BET, TGA, FESEM, etc. and carry out the effect of operational parameter for examples pH, metal loading, dosage, and initial concentration. Acknowledgements The authors are grateful for the financial support by the Short Term Research Grant (STRG) from Universiti Kuala Lumpur (Grant No. 17004 & 17029) and Majlis Amanah Rakyat (MARA) Malaysia, the awards of Pinjaman Pengajian Tinggi Perak (Nurul Fahmi Khairol), and also the Universiti Kuala Lumpur Branch Campus Malaysian Institute of Chemical and Bioengineering Technology for their support.

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References [1] Movahedi M, Mahjoub AR, Janitabar-Darzi S. Photodegradation of Congo red in aqueous solution on ZnO as an alternative catalyst to TiO2. J Iran Chem Soc 2009; 6: 570-577. [2] Sapawe N, Jalil AA, Triwahyono S, Sah RARN, Jusoh NWC, Hairom NHH, Efendi. Electrochemical strategy for grown ZnO nanoparticles deposited onto HY zeolite with enhanced photodecolorization of methylene blue: Effect of the formation of Si–O–Zn bonds. Appl Catal A: Gen 2013; 456:144–158. [3] Jalil AA, Satar MAH, Triwahyono S, Setiabudi HD, Kamarudin NHN, Jaafar NF, Sapawe N, Ahamad R. Tailoring the current density to enhance photocatalytic activity of CuO/HY for decolorization of malachite green. J Electroanal Chem 2013; 701:50–58. [4] Rauf MA, Meetani MA, Hisaindee S. An overview on the photocatalytic degradation of azo dyes in the presence of TiO2 doped with selective transition metals. Desalination 2011; 276: 13-27. [5] Ehishan NS, Sapawe N. Performance studies removal of chromium (Cr6+) and lead (Pb2+) by oil palm frond (OPF) adsorbent in aqueous solution. Mater Today: Proc 2018; 5(10): 21897-21904. [6] Fazry AHZ, Sapawe N, Aziz AIFA, Zainudin MZH, Hafiz MHH, Idris MAF, Hanafi MF, Fozi MFM. Microwave induced HNO2 and H3PO4 activation of oil palm frond (OPF) for removal of malachite green. Mater Today: Proc 2018; 5(10): 22143-22147 [7] Sapawe N, Jalil AA, Triwahyono S. One-pot electro-synthesis of ZrO2–ZnO/HY nanocomposite for photocatalytic decolorization of various dye-contaminants. Chem Eng J 2013; 225: 254–265. [8] Malwal D, Gopinath P. Enhanced photocatalytic activity of hierarchical three-dimensional metal oxide@CuO nanostructures towards the degradation of Congo red dye under solar radiations. Catal Sci Technol 2016; 6: 4458-4472. [9] Kumar P, Govindaraju M, Senthamilselvi S, Premkumar K. Photocatalytic degradation of methyl orange dye using silver (Ag) nanoparticles synthesized from Ulva lactuca. Colloid Surface B 2013; 103: 658-661. [10] Hayat K, Gondal MA, Khaled MM, Yamani ZH, Ahmed S. Laser induced photocatalytic degradation of hazardous dye (Safranin-O) using self synthesized nanocrystalline WO3. J Hazard Mater 2011; 186: 1226–1233. [11] Elango G, Roopan SM. Efficacy of SnO2 nanoparticles towards photocatalytic degradation of methylene blue dye. J Photoch Photobio B 2016; 155: 34-38. [12] Bansal P, Chaudhary GR, Mehta SK. Comparative study of catalytic activity of ZrO2 nanoparticles for sonocatalytic and photocatalytic degradation of cationic and anionic dyes. Chem Eng J 2015; 280: 475–485. [13] Nezamzadeh-Ejhieh A, Karimi-Shamsabadi M. Decolorization of a binary azo dyes mixture using CuO incorporated nanozeolite-X as a heterogeneous catalyst and solar irradiation. Chem Eng J 2013; 228: 631–641. [14] Pawinrat P, Mekasuwandumrong O, Panpranot J. Synthesis of Au–ZnO and Pt–ZnO nanocomposites by one-step flame spray pyrolysis and its application for photocatalytic degradation of dyes. Catal Commun 2009; 10: 1380–1385. [15] Saravanan R, Karthikeyan S, Gupta VK, Sekaran G, Narayanan V, Stephen A. Enhanced photocatalytic activity of ZnO/CuO nanocomposite for the degradation of textile dye on visible light illumination. Mat Sci Eng C-Mater 2013; 33: 91–98. [16] Ahmed MA, El-Katori EE, Gharni ZH. Photocatalytic degradation of methylene blue dye using Fe2O3/TiO2 nanoparticles prepared by sol– gel method. J Alloy Compd 2013; 553: 19–29. [17] Mirkhani V, Tangestaninejad S, Moghadam M, Habibi MH, Rostami-Vartooni A. Photocatalytic degradation of azo dyes catalyzed by Ag doped TiO2 photocatalyst. J Iran Chem Soc 2009; 6: 578-587. [18] Uddin MT, Nicolas Y, Olivier C, Toupance T, Servant L, Müller MM, Kleebe H, Ziegler J, Jaegermann W. Nanostructured SnO2−ZnO heterojunction photocatalysts showing enhanced photocatalytic activity for the degradation of organic dyes. Inorg Chem 2012; 51: 7764−7773. [19] Vinodgopal K, Kamat PV. Enhanced Rates of photocatalytic degradation of an azo dye using SnO/TiO2 coupled semiconductor thin films. Environ. Sci. Technol. 1995; 29: 841-845. [20] Mageshwari K, Nataraj D, Pal T, Sathyamoorthy T, Park J. Improved photocatalytic activity of ZnO coupled CuO nanocomposites synthesized by reflux condensation method. J Alloy Compd 2015 625: 362–370. [21] Shirzadi A, Nezamzadeh-Ejhieh A. Enhanced photocatalytic activity of supported CuO-ZnO semiconductors towards the photodegradation of Mefenamic acid aqueous solution as a semi real sample. J Mol Catal A-Chem. 2016; 41: 222-229. [22] Pal S, Maiti S, Maitib UN, Chattopadhyay KK. Low temperature solution processed ZnO/CuO heterojunction photocatalyst for visible light induced photo-degradation of organic pollutants. Cryst Eng Comm 2015; 17: 1464-1476. [23] Sathishkumara P, Sweenaa R, Wub JJ, Anandan S. Synthesis of CuO-ZnO nanophotocatalyst for visible light assisted degradation of a textile dye in aqueous solution. Chem Eng J 2011; 171: 136–140. [24] Li B, Wang Y. Facile synthesis and photocatalytic activity of ZnO-CuO nanocomposite. Superlattice Microst 2010; 47: 615-623. [25] Liu Z, Deng J, Deng J, Li F. Fabrication and photocatalysis of CuO/ZnO nano-composites via a new method. Mater Sci Eng B-Adv 2008; 150: 99–104. [26] Sapawe N, Jaafar NF, Hairom NHH, Satar MAH, Ariffin MN, Triwahyono S, Jalil AA. A facile preparation of nanosized ZnO and its use in photocatalytic decolorization of methyl orange. Mal J Fund Appl Sci 2011; 7: 19-23. [27] Sapawe N, Jalil1 AA, Triwahyono S. Photodecomposition of methylene blue over EGZrO2/HY in aqueous alkaline solution. Mal J Fund Appl Sci 2011; 7: 137-139. [28] Sapawe N, Jalil AA, Triwahyono S, Adam SH, Jaafar NF, Satar MAH. Isomorphous sub substitution of Zr in the framework of aluminosilicate HY by an electrochemical method: Evaluation by methylene blue decolorization. Appl Catal B: Environ 2012; 125: 311-323. [29] Jusoh NWC, Jalil AA, Triwahyono S, Setiabudi HD, Sapawe N, Satar MAH, Karim AH, Kamarudin NHN, Jusoh R, Jaafar NF, Salamun N, Efendi J. Sequential desilication–isomorphous substitution route to prepare mesostructured silica nanoparticles loaded with ZnO and their photocatalytic activity. Appl Catal A: Gen 2013; 468:276–287. [30] Jaafar NF, Jalil AA, Triwahyono S, Muhid MNM, Sapawe N, Satar MAH, Asaari H. Photodecolorization of methyl orange over α-Fe2O3supported HY catalysts: The effects of catalyst preparation and dealumination. Chem Eng J 2012; 191: 112– 122.

M.F. Khairol et al. / Materials Today: Proceedings 19 (2019) 1333–1339

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[31] Sapawe N, Hanafi MF. Facile one-pot electrosynthesis of high photoreactive hexacoordinated Si with Zr and Zn catalyst. RSC Adv 2015; 5: 75141-75144. [32] Sapawe N. Effective solar-based iron oxide supported HY zeolite catalyst for the decolorization of organic and simulated dyes. N J Chem 2015; 39: 6377-6387. [33] Sapawe N. Hybridization of zirconia, zinc and iron supported on HY zeolite as a solar-based catalyst for the rapid decolorization of various dyes. N J Chem 2015; 39: 4526-4533. [34] Zamri MSFA, Sapawe N. Performance studies of electrobiosynthesis of titanium dioxide nanoparticles (TiO2) for phenol degradation. Mater Today: Proc 2018; 5(10): 21797-21801. [35] Khairol NF, Sapawe N. Electrosynthesis of ZnO nanoparticles deposited onto egg shell for degradation of Congo red. Mater Today: Proc 2018; 5(10): 21936-21939. [36] Hanafi MF, Sapawe N. Remarkable degradation of methyl orange by tetragonal zirconia catalyst. Mater Today: Proc 2018; 5(10): 2184921852. [37] Hanafi MF, Sapawe N, Rahim MZA, Rahman NN, Rahman AHA, Ahmad AA. Performance of EGZrO2-EGFe2O3/HY as photocatalyst and its efficacy in decolorization of dye-contaminants. Mal J Anal Sci 2016; 20(5): 1052-1058. [38] Sapawe N, Jalil AA, Triwahyono S. Photodecolorization of methylene blue over EGZrO2/EGZnO/EGFe2O3/HY photocatalyst: Effect of radical scavenger. Mal J Fund Appl Sci 2013; 9: 67-73. [39] El-Kemary M, El-Shamy H, El-Mehasse I. Photocatalytic degradation of ciprofloxacin drug in water using ZnO nanoparticles. J Lumin 2010; 13: 2327–2331. [40] Hariharan C. Photocatalytic degradation of organic contaminants in water by ZnO nanoparticles: Revisited. Appl Catal A: Gen 2006; 304: 55–61. [41] Hong RY, Li JH, Chen LL, Liu DQ, Li HZ, Zheng Y, Ding J. Synthesis, surface modification and photocatalytic property of ZnO nanoparticles. Powder Technol 2009;189: 426–432. [42] Nagaraja R, Kottam N, Girija CR, Nagabhushana BM. Photocatalytic degradation of Rhodamine B dye under UV/solar light using ZnO nanopowder synthesized by solution combustion route. Powder Technol 2012; 215-216: 91–97. [43] Meshram SP, Adhyapak PV, Mulik UP, Amalnerkar DP. Facile synthesis of CuO nanomorphs and their morphology dependent sunlight driven photocatalytic properties. Chemical Engineering Journal 2012; 204–206: 158–168. [44] Bhattacharjee A, Ahmaruzzaman M. CuO nanostructures: Facile synthesis and applications for enhanced photodegradation of organic compounds and reduction of p-nitrophenol from aqueous phase. Roy Soc Ch 2016; 6: 41348-41363. [45] Katwal R, Kaur H, Sharma G, Naushad M, Pathania D. Electrochemical synthesized copper oxide nanoparticles for enhanced photocatalytic and antimicrobial activity. J Ind Eng Chem 2015; 31: 173-184. [46] Muhammad IM, El-Nafaty UA, Abdulsalam S, Makarfi YI. Removal of oil from oil produced water using eggshell. Civ Environ. Res 2012; 2: 52-64. [47] Zulfikar MA, Novita E, Hertadi R, Djajanti SD. Removal of humic acid from peat water using untreated powdered eggshell as a low cost adsorbent. Int J Environ Sci Technol 2013; 10: 1357–1366. [48] Tsai WT, Yang JM, Lai CW, Cheng YH, Lin CC, Yeh CW. Characterization and adsorption properties of eggshells and eggshell membrane. Bioresour Technol 2006; 97: 488–493. [49] Eletta OAA, Ajayi OA, Ogunleye OO, Akpan IC. Adsorption of cyanide from aqueous solution using calcinated eggshells: Equilibrium and optimisation studies. J Environ Chem Eng 2016; 4: 1367-1375. [50] Bhaumik R, Mondal NK, Das B, Roy P, Pal KC, Das C, Banerjee A, Datta JK. Eggshell powder as an adsorbent for removal of fluoride from aqueous solution: equilibrium, kinetic and thermodynamic studies. J Chem 2012; 9:1457-1480.