Removal of toxic heavy metal ions from waste water by functionalized magnetic core–zeolitic shell nanocomposites as adsorbents

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  Removal of toxic heavy metal ions from waste water by functionalized magnetic core–zeolitic shell nanocomposites as adsorbents
           1 3 Environmental Science and PollutionResearch  ISSN 0944-1344Volume 20Number 6 Environ Sci Pollut Res (2013)20:3900-3909DOI 10.1007/s11356-012-1333-y Removal of toxic heavy metal ions fromwaste water by functionalized magneticcore–zeolitic shell nanocomposites asadsorbents Mohsen Padervand & Mohammad RezaGholami           1 3 Your article is protected by copyright andall rights are held exclusively by Springer-Verlag Berlin Heidelberg. This e-offprint isfor personal use only and shall not be self-archived in electronic repositories. If you wishto self-archive your article, please use theaccepted manuscript version for posting onyour own website. You may further depositthe accepted manuscript version in anyrepository, provided it is only made publiclyavailable 12 months after official publicationor later and provided acknowledgement isgiven to the srcinal source of publicationand a link is inserted to the published articleon Springer's website. The link must beaccompanied by the following text: "The finalpublication is available at”.  RESEARCH ARTICLE Removal of toxic heavy metal ions from waste waterby functionalized magnetic core  –  zeolitic shellnanocomposites as adsorbents Mohsen Padervand  &  Mohammad Reza Gholami Received: 27 September 2012 /Accepted: 12 November 2012 /Published online: 27 November 2012 # Springer-Verlag Berlin Heidelberg 2012 Abstract  Functionalized magnetic core  –  zeolitic shell nano-composites were prepared via hydrothermal and precipitationmethods. The products were characterized by vibrating sam- ple magnetometer, X-ray powder diffraction, Fourier trans-form infrared spectroscopy, nitrogen adsorption  –  desorptionisotherms, and transmission electron microscopy analysis.The growth of mordenite nanocrystals on the outer surfaceof silica-coated magnetic nanoparticles at the presence of organic templates was well approved. The removal perfor-manceandtheselectivityofmixedmetalions(Pb 2+ andCd 2+ )inaqueoussolutionwereinvestigatedviathesorptionprocess.The batch methodwas employedtostudy the sorptionkinetic,sorption isotherms, and pH effect. The removal mechanism of metalionswasdonebychem  –   physsorptionandionexchange processes through the zeolitic channels and pores. The exper-imental data were well fitted by the appropriate kinetic mod-els.Thesorptionrateandsorptioncapacityofmetalionscould besignificantlyimprovedbyoptimizingthe parameter values. Keywords  Magneticcore  –  zeoliticshell .Toxicheavymetal ions .Sorption Introduction Elements having atomic weight between 63.5 and 200.6,and a specific gravity greater than 5.0 are known as heavymetals (Srivastava and Majumder  2008). While some of their ions are known to be toxic or carcinogenic, thesemetals are not biodegradable and tend to accumulate inliving organisms. Toxic heavy metals of particular concernin treatment of industrial wastewaters include zinc, copper,nickel, mercury, cadmium, lead, and chromium (Fu andWang 2011). Cadmium, zinc, copper, nickel, lead, mercury,and chromium are often detected in industrial wastewaters,which srcinate from metal plating, mining activities, smelt-ing, battery manufacture, tanneries, petroleum refining, paint manufacture, pesticides, pigment manufacture, print-ing and photographic industries, etc., (Ngah and Hanafiah2008; Jain et al. 1997; Srivastava et al. 1995; Gupta et al. 2009a , Gupta et al. 2007a ; Goyal et al. 2007). Heavy metal ions and the other impurities in wastewater can be removedfrom polluted waters using a wide range of methods such assolvent extraction, precipitation, vacuum evaporation, mem- brane technologies, ionic exchange, and adsorption (Gupta et al.,2000,2006a ,2006b,2007b,c,d,e,2009b,2010;Guptaand Rastogi 2009; Gupta and Sharma  2003; Ali 2010, 2012; Ali et  al. 2012; Mittal et al. 2005; Jain et al. 2004; Kim et al. 2000; Alvarez-AyusoandGarcia-Sanchez2003;Alvarez-Ayusoetal.2003; Erdem et al. 2004). Over the past decades, zeolites have a large applicabilityfor decontamination, purification of urban and industrial re-sidual waters, protection of waste disposal areas, purificationofindustrialgases,etc.Manyresearchersstudiedusingnaturaland synthetic zeolites to remove heavy metal ions in theaqueous medium (Langella et al. 2000; Cincotti et al. 2001; Badillo-Almarazetal.2003;Pericetal.2004).Propertiessuch as high surface area, individual micro-pores, a variety of channels, and high resistance make them very useful for industrial applications and academic research.The combination of zeolitic materials with magnetic and/ or active functional groups to form core  –  shell structuredcomposite is undoubtedly of special interest in diagnosticanalysis (Levy et al. 2002), bioseparation (Li et al. 2007), and controlled drug release (Murray et al. 1993; Yang et al.2008; Arruebo et al. 2006) based on their unique magnetic Responsible editor: Vinod Kumar Gupta M. Padervand :  M. R. Gholami ( * )Department of Chemistry, Sharif University of Technology,Azadi Ave, P.O.Box 11365  –  9516, Tehran, Irane-mail: Environ Sci Pollut Res (2013) 20:3900  –  3909DOI 10.1007/s11356-012-1333-y  responsivity, low cytotoxicity, good biocompatibility, andmesoporous properties. Over the past decade, the prepara-tion of multifunctional microspheres consisting of a magne-tite core with a mesoporous shell has been reported (Giri et al. 2005; Zhao et al. 2005; Deng et al. 2008; Guo et al. 2006; Kim et al. 2006). The uniform-sized magnetic particles werenormally prepared via a high-temperature decompositionmethod (Kim et al. 2006), or hydrothermal process (Denget al. 2008). The formation of the core  –  shell nanocompo-sites is conventionally followed by an encapsulation proce-dure, where the magnetite core is encapsulated by a silica layer using a sol  –  gel technique (Piaoping et al. 2009).The aim of the present study was to investigate the heavymetal ions sorption characteristics of structured magneticcore  –  zeolitic shell nanocomposites. The mechanism of heavymetalssorptionoverthedifferentcomposites,sorptionkinetic,and sorption isotherms was discussed. The dependence of sorption rate to the pH of solution was studied too. Experimental Materials, instruments, and methodsReagent grade chemicals such as NaOH, tetramethylammo-niumhydroxide (TMAOH) (10 %  w /  w ), ethylene glycol (EG),cyclohexane, cyclohexanole, C 14 H 22 O(C 2 H 4 O) n  (TritonX-100)100,3-glycidoxypropyltrimethoxysilane(GPTS),glu-tamic acid (GLU) and various salts of polyvalent metals wereused as required. Tetraethylorthosilicate (TEOS) was used asthe silica source. All chemicals were purchased from Merck chemical Co. (Germany) and were used without any further  purification. Water samples contaminated with heavy metalswere prepared using their respective metal ion salts.The X-ray diffraction (XRD) patterns of the prepared sam- ples were recordedon a Bruker D8advance X-ray diffractom-eter with CuK  α  irradiation ( λ 0 0.15406 nm). The Fourier transform infrared spectroscopy(FTIR) spectra wererecordedusing the NB series spectrometer. The specific surface area of the nanocomposites was calculated from the N 2  adsorption  –  desorption isotherm at 77 K, using Belsorp apparatus (Japan).Theaverageparticlesizeandmorphologyofthesampleswereexamined by transmission electron microscope (TEM).MagneticstudieswerecarriedoutonaTOEIVSM-5vibratingsample magnetometer (VSM) at 300 K.Core  –  shell nanocomposites preparation Synthesis of magnetic nanoparticles (NiFe 2 O 4  ) Magnetic nanoparticles were prepared via hydrothermalmethod in a 200-ml stainless steel autoclave with a Teflonliner under autogenous pressure. In a typical procedure, a 50-ml transparent solution containing Ni(NO 3 ) 2  and FeCl 3 (corresponding to Ni 2+ /Fe 3+ molar ratio of 1:2 ) was pre- pared and added to 50 ml of NaOH solution 2 M dropwiseunder magnetic stirring. Then a mixture includes EG andTMAOH was added to the above suspension dropwise.After stirring for 2 h, the resultant mixture was immediatelytransferred into the autoclave and kept at 200 °C for 8 h.After this time, the resulting solid products were collected by filtration, repeatedly washed with double-distilled water,and then dried 80 °C for 6 h. Silica coating of magnetic nanoparticles Silica-coated NiFe 2 O 4  nanoparticles were prepared bywater-in-oil microemulsion approach (Liu et al. 2010) withsome modifications. Cyclohexane (120 mL), cyclohexanol(30 mL) and Triton X-100 (30 mL) were placed in a round- bottom flask and the solution was stirred. Once the mixturewas homogeneous, an aqueous suspension of NiFe 2 O 4 nanoparticles (5 mL) was added to the above solution. Thesuspension was continuously stirred for 1 h. Ammonium(4 mL) and TEOS (4 mL) were then added. After themixture was stirred at room temperature for 24 h, the reac-tion solution was decanted with the aid of the magnet. Theobtained silica-coated nanoparticles were redispersed sever-al times in a mixture of double-distilled water and ethanol,separated magnetically, and dried at 80 °C for 12 h. Growth of mordenite nanocrystals on the SiO 2 @NiFe 2 O 4  surface Mordenite nanocrystals were grown on the surface of pri-mary synthesized cores (SiO 2 @NiFe 2 O 4 ) by hydrothermaltreatment and at the presence of organic templates. In a typical procedure, Al(NO 3 ) 3 ·9H 2 O is dissolved in alkalinesolution of NaOH 6 M. TMAOH and EG were added to the prepared solution under stirring. TEOS was added dropwiseto the above solution to obtain a gel where then magnetical-ly stirred for 3 h on a magnetic stirrer. The reluctant mixturewas immediately placed in a 200-ml autoclave which wasthen maintained in a preheated oven at autogenous pressureand static conditions. After the completion of the period of synthesis (24 h and 180 °C), the product was filtered andwashed repeatedly with double distilled water and dried at 90 °C for 10 h. Finally, the solid powder was calcined at 500 °C for 5 h and denoted Z@SiO 2 @NiFe 2 O 4 . Surface modification with GPTS   –  GLU  Z@SiO 2 @NiFe 2 O 4  nanocomposites were modified withGPTS and GLU according to the earlier work with some Environ Sci Pollut Res (2013) 20:3900  –  3909 3901  modifications (Zhiya et al. 2006). GLU was dissolved indouble-distilled water, and the obtained suspension was ad- justedtopH11withNaOH10M.Thesolutionwastransferredintoaflaskbottleplacedintheice-bathat0°C,andGPTSwasslowly added while being stirred. The mixed solution washeated to 65 °C for 2 h by stirring. After adjusting the pH of the prepared solution to 6 with concentrated HCl, anaqueous suspension of Z@SiO 2 @NiFe 2 O 4  was addedand stirred for 12 h. The resulting product was separatedwith the help of the permanent magnet, washed thor-oughly with distilled water, dried at 80 °C for 6 h anddenoted GPTS  –  GLU@Z@SiO 2 @NiFe 2 O 4 . Sorption test  All experiments were carried out in a 1-L batch reactor with the initial X(II) concentration (X 0 Pb and Cd) of 20 mg/L at the initial pH value 5. The sorbent mass wasfixed at 0.1 g. The reactor was stirred with a magneticstirrer operated at 300 rpm. At predetermined time inter-vals, 3 mL samples were taken from the reactor, centri-fuged, and residual X(II) concentration was measuredwith an atomic absorption spectrophotometer. By performing appropriate material balance, the quantity of X(II) adsorbed at the selected time intervals was deter-mined and used for kinetic analysis. Results and discussion Characterization VSM analysis The magnetic properties of the core  –  shell nanocomposites werecharacterized and the results are shown in Fig. 1. Magneticmeasurement shows that pure NiFe 2 O 4 , SiO 2 @NiFe 2 O 4 ,Z@SiO 2 @NiFe 2 O 4,  and GPTS  –  GLU@Z@SiO 2 @NiFe 2 O 4 have magnetic saturation values of 48, 36.1, 15, and 12.5 emu/ g,respectively.Itisimportantthatthegrowthofthezeoliticlayer on the surface decrease the magnetic saturation to less than half.ItshouldalsobenotedthatthemultiplemodifiedNiFe 2 O 4 coresstill show good magnetization, indicating their suitability for using and separation. The magnified hysteresis loops in Fig. 1confirm the superparamagnetic feature for all the samples.Moreover, the multifunctional core  –  shell nanocomposites withhomogenous dispersion exhibit the re-disperse properties and a suitable response to the external magnetic field due to its highmagnetization. -10000 -5000 0 5000 10000-60-40-20 0 204060    M  a  g  n  e   t   i  z  a   t   i  o  n   (  e  m  u   /  g   ) Applied Field(Oe) -10000 -5000 0 5000 10000-40-30-20-10 0 10203040 Applied Field(Oe)    M  a  g  n  e   t   i  z  a   t   i  o  n   (  e  m  u   /  g   ) ab -10000 -5000 0 5000 10000-20-15-505101520 Applied Field(Oe)    M  a  g  n  e   t   i  z  a   t   i  o  n   (  e  m  u   /  g   ) -10000 -5000 0 5000 10000-15-10-5051015 Applied Field(Oe)    M  a  g  n  e   t   i  z  a   t   i  o  n   (  e  m  u   /  g   ) cd -10 Fig. 1  Magnetic saturation results:  a  NiFe 2 O 4 ,  b  SiO 2 @NiFe 2 O 4 ,  c  Z@SiO 2 @NiFe 2 O 4 ,  d  GPTS  –  GLU@Z@SiO 2 @NiFe 2 O 4 3902 Environ Sci Pollut Res (2013) 20:3900  –  3909
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