An assessment of zinc oxide nanosheets as a selective adsorbent for cadmium
© Khan et al.; licensee Springer. 2013
Received: 23 July 2013
Accepted: 13 August 2013
Published: 5 September 2013
Zinc oxide nanosheet is assessed as a selective adsorbent for the detection and adsorption of cadmium using simple eco-friendly extraction method. Pure zinc oxide nanosheet powders were characterized using field emission scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The zinc oxide nanosheets were applied to different metal ions, including Cd(II), Cu(II), Hg(II), La(III), Mn(II), Pb(II), Pd(II), and Y(III). Zinc oxide nanosheets were found to be selective for cadmium among these metal ions when determined by inductively coupled plasma-optical emission spectrometry. Moreover, adsorption isotherm data provided that the adsorption process was mainly monolayer on zinc oxide nanosheets.
KeywordsZinc oxide Nanosheets Metal uptake Cd(II) Environmental applications
With the development of industry and economy, environmental problem becomes more and more serious day by day [1–3]. Due to certain man-made activities, numerous hazardous compounds and heavy metals are introduced into the environment which is a concerning matter for monitoring agencies and regulation authorities [4–6]. Among these pollutants, toxic metals are the most sever pollutants and main environmental threat which instigate too many serious public health and cost-cutting problems [7, 8]. Cadmium is known to be as highly toxic as probably carcinogenic for humans and is listed as the sixth most poisonous substance jeopardizing human health. Cadmium is introduced into water bodies from different sources, for example, smelting, metal plating, cadmium-nickel batteries, phosphate fertilizers, mining, pigments, stabilizers, alloy industries, and sewage sludge. The harmful effects of Cd(II) involve a number of acute and chronic disorders such as gastrointestinal irritation, vomiting, abdominal pain, diarrhea, renal damage, emphysema, hypertension, and testicular atrophy [9, 10]. Therefore, separation and determination of Cd(III) in different matrices have continued to be of import.
In addition, the development of simple, rapid, and efficient methods has become of interest for monitoring metal ions in the environment. Several analytical methods have been applied to analyze metal ions in aqueous solutions [7, 8]. However, analytical methods cannot directly measure metal ions, in particular at ultra-trace concentration, in aqueous systems due to the lack of sensitivity and selectivity of these methods. Therefore, an efficient separation procedure is usually required prior to the determination of noble metals for sensitive, accurate, and interference-free determination of noble metals.
Several analytical methods have been utilized for separation of analyte of interest, including liquid/liquid extraction, ion exchange, coprecipitation, cloud-point extraction, and solid-phase extraction (SPE) [11, 12]. SPE is considered to be one of the most powerful techniques because it minimizes solvent usage and exposure, disposal costs, and extraction time for sample preparation. Several adsorbents have appeared because of the popularity of SPE for selective extraction of analytes such polymers, silica, carbon nanotube, etc. [7, 8].
Nanoscience and technology have attracted significant attention due to its potential application in various fields and especially in metal ion adsorption [13, 14]. ZnO, a versatile material, emerges as a challenging prospect in the field of nanotechnology. Nanosized ZnO has been widely used as a catalyst , gas sensor [15, 16], active filler for rubber and plastic, ultraviolet (UV) absorber in cosmetics, and antivirus agent in coating [17, 18] and has more potential application in building functional electronic devices with special architecture and distinctive optoelectronic properties.
In this investigation, we synthesized ZnO nanosheets by stirring method and characterized by X-ray diffraction patterns (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS). ZnO nanosheets were applied to investigate their utility and the analytical efficiency as adsorbent on the selectivity and adsorption capacity of Cd(II). The selectivity of ZnO nanosheets toward eight metal ions, including Cd(II), Cu(II), Hg(II), La(III), Mn(II), Pb(II), Pd(II), and Y(III), was investigated in order to study the effectiveness of ZnO nanosheets on the adsorption of selected metal ions. Based on the selectivity study, the ZnO nanosheets attained the highest selectivity toward Cd(II). Static uptake capacity of ZnO nanosheets for Cd(II) was found to be 97.36 mg g−1. Adsorption isotherm data of Cd(II) with ZnO nanosheets were well fit with the Langmuir adsorption isotherm, strongly confirming that the adsorption process was mainly monolayer on homogeneous adsorbent surfaces.
Chemicals and reagents
Zinc nitrate, sodium hydroxide, mercuric nitrate, lanthanum nitrate, palladium nitrate, and yttrium nitrate were purchased from Sigma-Aldrich (Milwaukee, WI, USA). Stock standard solutions of 1,000 mgL−1 Cd(II), Cu(II), Mn(II), and Pb(II) were also obtained from Sigma-Aldrich. All reagents used were of high purity and of spectral purity grade, and doubly distilled deionized water was used throughout.
Preparation of ZnO nanosheets
ZnO nanosheets were synthesized by thermal stirring method in which 0.1 M of zinc nitrate aqueous solution was titrated with 0.1 M solution of NaOH till pH reached above 10 and stirred at 70°C for overnight. White product was washed and dried. The dried product was calcined at 450°C for 4 h.
Possible growth mechanism of ZnO nanosheets
The morphology of the synthesized product was studied at 15 kV using a JEOL Scanning Electron Microscope (JSM-7600 F, Akishima-shi, Japan). XRD was taken with a computer-controlled RINT 2000, Rigaku diffractometer (Shibuya-ku, Japan) using the Ni-filtered Cu-Kα radiation (λ = 0.15405 nm). FT-IR spectrum was recorded in the range of 400 to 4,000 cm−1 on PerkinElmer (spectrum 100, Waltham, MA, USA) FT-IR spectrometer. XPS spectrum was recorded in the range of 0 to 1,350 eV by using Thermo Scientific K-Alpha KA1066 spectrometer (Schwerte, Germany).
Samples preparation and procedure for metal uptake study
Stock solutions of Cd(II), Cu(II), Hg(II), La(III), Mn(II), Pb(II), Pd(II), and Y(III) were prepared in 18.2 MΩ·cm distilled deionized water and stored in the dark at 4°C. For studying the selectivity of ZnO nanosheets toward metal ions, standard solutions of 2 mg L−1 of each metal ion were prepared and adjusted to pH value of 5.0 with a buffered aqueous solution (0.1 mol L−1 CH3COOH/CH3COONa). Standard solutions were adjusted at pH value of 5.0 in order to avoid the formation of suspended gelatinous lanthanides hydroxides with buffer solutions at pH values beyond 5.0. Each standard solution was individually mixed with 25 mg of the ZnO nanosheets. For investigation of the Cd(II) adsorption capacity, standard solutions of 0, 5, 10, 15, 20, 25, 30, 50, 75, 125, and 150 mg L−1 were prepared as above, adjusted to pH value of 5.0 and individually mixed with 25 mg ZnO nanosheets. All mixtures were mechanically shaken for 1 h at room temperature.
Inductively coupled plasma-optical emission spectrometry (ICP-OES) measurements were acquired by use of a Perkin Elmer ICP-OES model Optima 4100 DV (Waltham, MA, USA). The ICP-OES instrument was optimized daily before measurement and operated as recommended by the manufacturers. The ICP-OES spectrometer was used with following parameters: FR power, 1,300 kW; frequency, 27.12 MHz; demountable quartz torch, Ar/Ar/Ar; plasma gas (Ar) flow, 15.0 L min−1; auxiliary gas (Ar) flow, 0.2 L min−1; nebulizer gas (Ar) flow, 0.8 L min−1; nebulizer pressure, 2.4 bars; glass spray chamber according to Scott (Ryton), sample pump flow rate, 1.5 mL min−1; integration time, 3 s; replicates, 3; wavelength range of monochromator, 165 to 460 nm. Selected metal ions were measured at wavelengths of 228.80 nm for Cd(II), 327.39 nm for Cu(II), 194.17 nm for Hg(II), 348.90 nm for La(III), 275.61 nm for Mn(II), 220.35 nm for Pb(II), 340.46 nm for Pd(II), and 361.10 nm for Y(III).
Results and discussion
Figure 4b shows the typical FT-IR spectra of the ZnO nanomaterial measured in the range of 420 to 4,000 cm−1. The appearance of a sharp band at 495.18 cm−1 in the FT-IR spectrum is indication of ZnO nanosheets which is due to Zn-O stretching vibration . The absorption peaks at 3,477 and 1,612 cm−1 are caused by the O-H stretching of the absorbed water molecules from the environment .
Selectivity study of ZnO nanosheets
Selectivity study of ZnO nanosheets adsorption toward different metal ions at pH 5.0 and 25°C ( N = 5)
Static adsorption capacity
Adsorption isotherm models
where Ce corresponds to the equilibrium concentrations of Cd(II) ion in solution (mg mL−1) and q e is the adsorbed metal ion by the adsorbate (mg g−1). The symbols Qo and b refer to Langmuir constants related to adsorption capacity (mg g−1) and energy of adsorption (L mg−1), respectively. These constants can be determined from a linear plot of Ce/qe against Ce with a slope and intercept equal to 1/Qo and 1/Qob, respectively. Moreover, the essential characteristics of Langmuir adsorption isotherm can be represented in terms of a dimensionless constant separation factor or equilibrium parameter, RL, which is defined as RL = 1/(1 + bCo), where b is the Langmuir constant (indicates the nature of adsorption and the shape of the isotherm); Co the initial concentration of the analyte. The RL value indicates the type of the isotherm, and RL values between 0 and 1 represent a favorable adsorption .
The experimental isotherm data were best fit with the Langmuir equation (Figure 7b) based on the least square fit, confirming the validity of Langmuir adsorption isotherm model for the adsorption process. Consequently, adsorption isotherm data suggested that the adsorption process was mainly monolayer on a homogeneous adsorbent surface. Langmuir constants Qo and b are found to be 99.60 mg g−1 and 0.28 L mg−1, respectively. The correlation coefficient obtained from the Langmuir model is found to be R2 = 0.989 for adsorption of Cd(II) on ZnO nanosheets. Moreover, the Cd(II) adsorption capacity (99.60 mg g−1) calculated from Langmuir equation was consistent with that (97.36 mg g−1) of the experimental isotherm study. The RL value of Cd(II) adsorption on the ZnO nanosheets is 0.03, supporting a highly favorable adsorption process based on the Langmuir classical adsorption isotherm model.
ZnO nanosheets were synthesized by low-temperature eco-friendly method and evaluated their efficiency for selective adsorption and determination of Cd(II) in aqueous solution. Reasonable static adsorption capacities of 97.36 mg g−1 for ZnO nanosheet adsorbent were achieved for Cd(II) in aqueous solution. Adsorption isotherm data of Cd(II) were well fit with the Langmuir classical adsorption isotherm model. Thus, the method may play an important role for using it as an effective approach for a selective adsorption and determination of Cd(II) in complex matrices for a range of several applications.
This project was funded by the Center of Excellence for Advanced Materials Research (CEAMR), King Abdulaziz University, Jeddah, under grant no. (CEAMR-434-01).
- Khan SB, Faisal M, Rahman MM, Jamal A: Exploration of CeO2 nanoparticles as a chemi-sensor and photo-catalyst for environmental applications. Sci Tot Environ 2011, 409: 2987. 10.1016/j.scitotenv.2011.04.019View ArticleGoogle Scholar
- Khan SB, Akhtar K, Rahman MM, Asisir AM, Seo J, Alamry KA, Han H: A thermally and mechanically stable eco-friendly nanocomposite for chemical sensor applications. New J Chem 2012, 36: 2368. 10.1039/c2nj40549kView ArticleGoogle Scholar
- Khan SB, Rahman MM, Jang ES, Akhtar K, Han H: Special susceptive aqueous ammonia chemi-sensor: extended applications of novel UV-curable polyurethane-clay nanohybrid. Talanta 2011, 84: 1005. 10.1016/j.talanta.2011.02.036View ArticleGoogle Scholar
- Faisal M, Khan SB, Rahman MM, Jamal A: Synthesis, characterizations, photocatalytic and sensing studies of ZnO nanocapsules. Appl Surf Sci 2011, 258: 672. 10.1016/j.apsusc.2011.07.067View ArticleGoogle Scholar
- Dai G, Liu S, Liang Y, Luo T: Synthesis and enhanced photoelectrocatalytic activity of p–n junction Co3O4/TiO2 nanotube arrays. Appl Surf Sci 2013, 264: 157.View ArticleGoogle Scholar
- Faisal M, Khan SB, Rahman MM, Jamal A, Abdullah MM: Fabrication of ZnO nanoparticles based sensitive methanol sensor and efficient photocatalyst. App Surf Sci 2012, 258: 7515. 10.1016/j.apsusc.2012.04.075View ArticleGoogle Scholar
- Khan SB, Alamry KA, Marwani HM, Asiri AM, Rahman MM: Synthesis and environmental applications of cellulose/ZrO2 nanohybrid as a selective adsorbent for nickel ion. Compos Part B-Eng 2013, 50: 253.View ArticleGoogle Scholar
- Asiri AM, Khan SB, Alamry KA, Marwani HM, Rahman MM: Growth of Mn3O4 on cellulose matrix: nanohybrid as a solid phase adsorbent for trivalent chromium. Appl Surf Sci 2013, 270: 539.View ArticleGoogle Scholar
- Leyva-Ramos R, Rangel-Mendez JR, Mendoza-Barron J, Fuentes-Rubio L, Guerrero-Coronado RM: Adsorption of cadmium(II) from aqueous solution on activated carbon. Water Sci Technol 1997, 35: 205.View ArticleGoogle Scholar
- Ensafi AA, Ghaderi AR: On-line solid phase selective separation and preconcentration of Cd(II) by solid-phase extraction using carbon active modified with methyl thymol blue. J Hazard Mater 2007, 148: 319. 10.1016/j.jhazmat.2007.02.037View ArticleGoogle Scholar
- Rahman MM, Khan SB, Marwani HM, Asiri AM, Alamry KA, Al-Youbi AO: Selective determination of gold(III) ion using CuO microsheets as a solid phase adsorbent prior by ICP-OES measurement. Talanta 2013, 104: 75.View ArticleGoogle Scholar
- Rahman MM, Khan SB, Marwani HM, Asiri AM, Alamry KA: Selective iron(III) ion uptake using CuO-TiO2 nanostructure by inductively coupled plasma-optical emission spectrometry. Chem Central J 2012, 6: 158. 10.1186/1752-153X-6-158View ArticleGoogle Scholar
- Xi G, Yi P, Zhu Y, Xu L, Zhang W, Yu W, Qian Y: Preparation of beta-MnO2 nanorods through a gamma-MnOOH precursor route. Mater Res Bull 2004, 39: 1641. 10.1016/j.materresbull.2004.05.014View ArticleGoogle Scholar
- Kamat VP, Huehn R, Nicolaescu R: A sense and shoot approach for photocatalytic degradation of organic contaminants in water. J Phys Chem B 2002, 106: 788. 10.1021/jp013602tView ArticleGoogle Scholar
- Lin HM, Tzeng SJ, Hsiau PJ, Tsai WL: Electrode effects on gas sensing properties of nanocrystalline zinc oxide. Nanostruct Mater 1998, 10: 465. 10.1016/S0965-9773(98)00087-7View ArticleGoogle Scholar
- Xu JQ: Pan QY, Shun YA, Tian ZZ: Grain size control and gas sensing properties of ZnO gas sensor. Sens Actuators B Chem 2000, 66: 277. 10.1016/S0925-4005(00)00381-6View ArticleGoogle Scholar
- Hu ZS: Oskam G, Searson PC: Influence of solvent on the growth of ZnO nanoparticles. J Colloid Interf Sci 2003, 263: 454. 10.1016/S0021-9797(03)00205-4View ArticleGoogle Scholar
- Chen SJ, Lia LH: Preparation and characterization of nanocrystalline zinc oxide by a novel solvothermal oxidation route. J Cryst Growth 2003, 252: 184. 10.1016/S0022-0248(02)02495-8View ArticleGoogle Scholar
- Khan SB, Faisal M, Rahman MM, Jamal A: Low-temperature growth of ZnO nanoparticles: photocatalyst and acetone sensor. Talanta 2011, 85: 943. 10.1016/j.talanta.2011.05.003View ArticleGoogle Scholar
- Faisal M, Khan SB, Rahman MM, Jamal A: Role of ZnO-CeO2 nanostructures as a photo-catalyst and chemi-sensor. J Mater Sci Technol 2011, 27: 594. 10.1016/S1005-0302(11)60113-8View ArticleGoogle Scholar
- Nandi SK, Chakraborty S, Bera MK, Maiti CK: Structural and optical properties of ZnO films grown on silicon and their applications in MOS devices in conjunction with ZrO2 as a gate dielectric. Bull Mater Sci 2007, 30: 247. 10.1007/s12034-007-0044-3View ArticleGoogle Scholar
- Han DM, Fang GZ, Yan XP: Preparation and evaluation of a molecularly imprinted sol–gel material for on-line solid-phase extraction coupled with high performance liquid chromatography for the determination of trace pentachlorophenol in water samples. J Chromatogr A 2005, 1100: 131–136. 10.1016/j.chroma.2005.09.035View ArticleGoogle Scholar
- Ho Y, Ofomaja AE: Biosorption thermodynamics of cadmium on coconut copra meal as biosorbent. Biochem Eng J 2006, 30: 117–123. 10.1016/j.bej.2006.02.012View ArticleGoogle Scholar
- Salem Z, Allia K: Cadmium biosorption on vegetal biomass. Int J Chem React Eng 2008, 6: 1–9.Google Scholar
- Wang X, Xia S, Chen L, Zhao J, Chovelon J, Nicole J: Biosorption of cadmium(II) and lead(II) ions from aqueous solutions onto dried activated sludge. J Environ Sci 2006, 18: 840–844. 10.1016/S1001-0742(06)60002-8View ArticleGoogle Scholar
- Green-Ruiz C, Rodriguez-Tirado V, Gomez-Gil B: Cadmium and zinc removal from aqueous solutions by Bacillus jeotgali : pH, salinity and temperature effects. Bioresour Technol 2008, 99: 3864–3870. 10.1016/j.biortech.2007.06.047View ArticleGoogle Scholar
- Yu J, Tong MS, Li XB: A simple method to prepare poly(amic acid)-modified biomass for enhancement of lead and cadmium adsorption. Biochem Eng J 2007, 33: 126–133. 10.1016/j.bej.2006.10.012View ArticleGoogle Scholar
- Schiewer S, Patil SB: Pectin-rich fruit wastes as biosorbents for heavy metal removal: Equilibrium and kinetics. Bioresour Technol 2008, 99: 1896–1903. 10.1016/j.biortech.2007.03.060View ArticleGoogle Scholar
- Luo C, Wei R, Guo D, Zhang S, Yan S: Adsorption behavior of MnO2 functionalized multi-walled carbon nanotubes for the removal of cadmium from aqueous solutions. Chem Eng J 2013, 225: 406–415.View ArticleGoogle Scholar
- Kalfa OM, Yalçınkaya O, Turker AR: Synthesis of nano B2O3/TiO2 composite material as a new solid phase extractor and its application to preconcentration and separation of cadmium. J Hazard Mater 2009, 166: 455–461. 10.1016/j.jhazmat.2008.11.112View ArticleGoogle Scholar
- Mobasherpour I, Salahi E, Pazouki M: Removal of divalent cadmium cations by means of synthetic nano-crystallite hydroxyapatite. Desalination 2011, 266: 142–148. 10.1016/j.desal.2010.08.016View ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.