Microwave-enforced sorption of heavy metals from aqueous solutions on the surface of magnetic iron oxide-functionalized-3-aminopropyltriethoxysilane

Chemical Engineering Journal 293 (2016) 200–206

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Microwave-enforced sorption of heavy metals from aqueous solutions on the surface of magnetic iron oxide-functionalized-3-aminopropyltriethoxysilane Mohamed E. Mahmoud a,⇑, Mohamed F. Amira a,1, Amal A. Zaghloul a,1, Ghada A.A. Ibrahim b a b

Faculty of Sciences, Chemistry Department, Alexandria University, P.O. Box 426, Ibrahimia 21321, Alexandria, Egypt Faculty of Education, Chemistry and Physics Department, Alexandria University, El-Shatby, Alexandria, Egypt

h i g h l i g h t s

g r a p h i c a l a b s t r a c t


A novel microwave technique for

enforced sorption of heavy metals is reported.
Microwave-assisted synthesis of Nano-Fe3O4–SiO2–NH2 sorbent as a green chemical process is described.
Excellent metal sorption capacity values are established in a short time range 15–25 s.

a r t i c l e

i n f o

Article history: Received 2 January 2016 Received in revised form 16 February 2016 Accepted 17 February 2016 Available online 24 February 2016 Keywords: Microwave-enforced solid phase extraction Microwave-assisted synthesis Nano-Fe3O4–SiO2–NH2 Metal ions

a b s t r a c t A high performance novel extraction method for heavy metal ions from aqueous solutions is investigated using a microwave-assisted heating technique. The selected solid material is a functionalized nanomagnetic iron oxide with 3-aminopropyltriethoxysilane [Nano-Fe3O4–SiO2–NH2] which is synthesized using a microwave-assisted procedure. The metal sorption properties of this magnetic nano-sorbent with four different divalent metal ions, viz. Pb(II), Cu(II), Cd(II) and Hg(II) were evaluated by heating the interacting metal ion solution in contact with the sorbent in a microwave oven for 5–30 s. Pb(II) was found the highest extracted metal ion and the capacity value was identified as 1250 lmol g1 after heating for 5 s, while the equilibrium capacity value was obtained as 1300 lmol g1 at 15 s. The maximum capacity values of Cu(II), Cd(II) and Hg(II) were characterized as 1050, 350 and 350 after microwave heating for 25, 15 and 25 s, respectively. The collected data refer to an excellent and high performance solid phase extraction methodology of heavy metal ions from their matrices in few seconds based on using the microwave-enforced sorption technique. The functionalized Nano-Fe3O4–SiO2–NH2 sorbent was synthesized using the microwave-assisted preparation system and characterized by the FT-IR, SEM, HR-TEM, XRD-method and surface area determination. Ó 2016 Elsevier B.V. All rights reserved.

1. Introduction

⇑ Corresponding author. Tel.: +20 1140933009; fax: +20 3 3911794. 1

E-mail address: [email protected] (M.E. Mahmoud). Tel.: +20 1140933009; fax: +20 3 3911794.

http://dx.doi.org/10.1016/j.cej.2016.02.056 1385-8947/Ó 2016 Elsevier B.V. All rights reserved.

A large number of extraction techniques are well known for their ability to extract the target analytes from their matrices, isolate the product of interest from plant materials or micro-organisms, preconcentrate low concentration levels of some

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pollutants from their environments and purification of some compounds. The classical extraction techniques include liquid–liquid extraction (LLE) [1], accelerated solvent extraction (ASE) [2], soxhlet extraction [3], supercritical fluid extraction (SFE) [4] and pressurized solvent extraction (PSE) [5] as well as others [6]. However, most of these techniques are suffering from timeconsuming and requiring large volumes of hazard solvents. However, advances in extraction techniques are recently focused on the microwave-assisted extraction (MAE) [7–9] and solid phase extraction (SPE) [10–12] as well as solid phase micro-extraction techniques [13,14] due to fast and efficient applications for extraction of the target analytes from their samples or matrices. Each of these techniques is characterized by its own advantages and disadvantages. However, the MAE is the most recently reported which is based on heating the sample under microwave energy for a short period of time to transfer the analyte(s) of interest from its solution to the extracting and partitioning solvent [15]. This technology affords reduction of the amount of solvent by a factor P100 and thus decreases the amount of waste hazard materials due to generation of waste solvents [16,17]. The selection of an extraction technique is mainly based on the time and efficiency of the selected process. Recently, strong emphasis is directed to finding out the most efficient extraction technique to collect the compound of interest from its matrix [18]. However, isolation, extraction and removal of the target species from their samples are heavily dependent on the type and efficiency of the extraction technique, solvent and sample as well as time and speed of the selected technique [19]. The implementation of magnetic nanomaterials in SPE has received considerable interests in recent years due to their advantages as magnetic and nanosized particles [20–25]. Applications of these sorbents in magnetic solid phase extraction (MSPE) technique can eliminate the problems of column packing and phase separation by simply using an external magnetic field [26–29]. The present study is directed to explore a high performance methodology based on the potential implementation and validation of microwave-enforced sorption of some selected heavy metal ions from aqueous solutions on the surface of Nano-Fe3O4–SiO2– NH2 as the target magnetic nanosorbent. The contribution of microwave heating time and temperature factors on the metal capacity values of Pb(II), Cu(II), Cd(II) and Hg(II) were also explored and evaluated in this study. In addition, the examined magnetic nano-sorbent has been also synthesized using a microwaveassisted procedure.

2. Experimental 2.1. Instrumentations The microwave apparatus is a household oven (KOG-1B5H, Korea) and operates with 1400-W output power at a frequency of 2.45 GHz. The Fourier transform infrared (FT-IR) spectra were recorded from KBr pellets using a BRUKER Tensor 37 Fourier transform infrared spectrophotometer. The scanning electron microscope (JSM-6360LA, JEOL Ltd.), (JSM-5300, JEOL Ltd.) and an ion sputtering coating device (JEOL-JFC-1100E) were used to image the surface morphology. High resolution-transmission electron microscopy (HR-TEM, JEM-2100) was used to image the sorbent using scanning image observation device to give bright and dark-field TEM images at 200 kV. The crystalline structure and phase purity of the sorbents were examined using X-ray diffraction (XRD) analysis by Adrukru D8 ADUANCE, X-ray diffractometer using target Cu-Ka. Thermal gravimetric analysis (TGA) of magnetic nano-sorbents were measured using a Perkin-Elmer TGA7 Thermobalance. The surface area analysis was performed

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by the BET method (Nova 3200 Nitrogen physisorption Apparatus, USA). 2.2. Materials Anhydrous ferric chloride (FeCl3), cadmium nitrate, lead nitrate, sodium hydroxide and hydrochloric acid were purchased from BDH Chemicals Ltd, Poole, England. Ferrous chloride (FeCl2) and sodium silicate were purchased from Oxford, India. Copper acetate monohydrate and mercuric chloride were purchased from Riedelde Haën, AG, Seelz-Hannover, Germany. 2.3. Microwave-assisted functionalization and synthesis of NanoFe3O4–SiO2–NH2 sorbent The functionalized magnetite nano-sorbent [Nano-Fe3O4–SiO2– NH2] was prepared by three successive microwave-assisted heating procedures according to the following steps as also shown in Scheme 1. Nano-Fe3O4 was first prepared by the reaction of 0.04 mol of FeCl3 and 0.02 mol of FeCl2 in 50 mL of 0.5 mol L1 HCl solution. This mixture was heated to 80 °C in a microwave oven. 400 mL of 2.0 mol L1 sodium hydroxide solution was then added and followed by heating for one minute at 80 °C. The resulting NanoFe3O4 sorbent was collected using an external magnet, washed several times with distilled water and finally dried at 50 °C. Nano-Fe3O4–SiO2 was synthesized using microwave heating at 80 °C for 2 min of a suspension of 1.0 g of Nano-Fe3O4 in distilled water. 20.0 mL of 1.0 mol L1 sodium silicate solution was added drop by drop with stirring and heating for 30 s. The pH of this mixture was adjusted to 6.0 and the reaction mixture was further heated in the microwave oven for 10 min. The resulting Nano-Fe3O4–SiO2 sorbent was collected, washed several times with distilled water and finally dried at 50 °C until complete dryness. Amino functionalization of Nano-Fe3O4–SiO2–NH2 sorbent was accomplished using the microwave heating approach by surface reaction of 1.0 g sorbent with 2 mL of 3-aminopropyltriethoxysilane as the silylation agent and heating into the microwave oven for three minutes. The reaction contents were left to cool to the room temperature and the heating and cooling processes were repeated several times to obtain Nano-Fe3O4–SiO2–NH2 sorbent. Finally, the produced sorbent was washed with ethanol and diethylether several times and dried at 50 °C. 2.4. Microwave-enforced sorption and solid phase extraction of heavy metals 10 mL of 0.01 mol L1 of the selected metal ion, viz. Pb(II), Cu (II), Cd(II) and Hg(II) was added to 10.0 ± 1.0 mg of Nano-Fe3O4– SiO2–NH2 sorbent in a test tube and heated for the selected time period (5.0–30.0 s) inside a microwave oven at 1400 W. The reaction mixture was filtered and washed with 50 mL of DW. The unextracted metal ion in the filtrate was titrated with a 0.01 mol L1 of EDTA solution using the proper buffer and indicator for each metal ion. 3. Result and discussion 3.1. Microwave synthesis and characterization of Nano-Fe3O4–SiO2– NH2 Synthesis of magnetic Nano-Fe3O4–SiO2–NH2 sorbent was based on the following procedures (Scheme 1). Nano-Fe3O4 sorbent

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Scheme 1. Microwave-assisted synthesis of Nano-Fe3O4–SiO2–NH2 sorbent.

was prepared using a microwave-assisted coprecipitation reaction as described by Eq. (1) [30]:

2FeðIIIÞ þ FeðIIÞ þ 8OH !Nano-Fe3 O4 þ 4H2 O

ð1Þ

The second step in this synthetic route was based on the microwave-assisted reaction of Nano-Fe3O4 with a shielding layer of nano-silicon oxide by the direct reaction with sodium silicate solution using pH 6 for the formation of Nano-Fe3O4–SiO2 sorbent. Nano-Fe3O4 was suggested to bind with sodium silicate in presence of water and microwave heating temperature to produce Nano-Fe3O4–SiO2 via direct chemical and covalent bonding of the silicate ion (SiO2 3 ) with the surface hydroxyl group of NanoFe3O4 as previously described [31]. The third synthetic step was also accomplished by the microwave heating reaction of NanoFe3O4–SiO2 with 3-aminopropyltriethoxy-silane. The hydroxyl groups on the surface of the core/shell magnetite nanoparticles reacted with the alkoxyl groups of the silane molecules leading to the formation of the aimed Nano-Fe3O4–SiO2–NH2 which contains the terminal functional amino groups as shown in Scheme 1. Determination of the surface area of magnetic Nano-Fe3O4–SiO2– NH2 sorbents was accomplished using four different approaches including the multipoint BET method, BJH cumulative desorption method, DH cumulative desorption, t-method of external surface area. Nano-Fe3O4–SiO2–NH2 sorbent was identified to exhibit high surface area value, viz. 3.08  10 m2/g. In addition, Nano-Fe3O4– SiO2–NH2 sorbent was found to exhibit pore volume value corresponding to 9.45  102 cc/g, while the pore size value was characterized as 6.14  101 Å. The FT-IR spectra of successfully synthesized and functionalized magnetic Nano-Fe3O4–SiO2–NH2 is shown in Fig. 1a and confirmed by the presence of two broad absorption bands at 3408 cm1 and 1651 cm1 which are related to the N–H stretching and NH2 bending vibrations of the free amino groups, respectively. The presence of anchored propyl group was also confirmed by the C–H stretching vibrations at 2929 cm1 and 2867 cm1 [32,33]. The absorption peak at nearly 3400 cm1 is mainly due to the intramolecular hydrogen bonding in this nano-sorbent [34]. In addition, a strong characteristic absorption peaks at 570 cm1 is ascribed to the Fe–O bond in the magnetite phase [35]. The surface reaction of

Fig. 1. FT-IR spectrum of (a) Nano-Fe3O4–SiO2–NH2 sorbent and (b) loaded with Pb (II) ion.

silica-coating on the magnetite nanoparticles was confirmed by absorption bands at 1126 cm1 and 1039 cm1 which are assigned to the Si–O–Si and Si–OH bonding, respectively [36]. In addition, the FT-IR of the Nano-Fe3O4–SiO2–NH2 after loading with Pb(II) as the highest extracted metal ion by this sorbent is represented in Fig. 1b for comparison.

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Fig. 2. XRD patterns of magnetic nano-sorbents.

Fig. 3. SEM image of Nano-Fe3O4–SiO2–NH2 sorbent.

Fig. 2 represents the X-ray diffraction patterns of magnetic nano-sorbents. As shown in Fig. 2a, the X-ray diffraction peaks appear at 2h equal to 30.3°, 35.8°, 43.2°, 53.8°, 57.3° and 62.9° are related to their corresponding indices (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1) and (4 4 0), respectively. These peaks are indexed to the highly crystalline cubic structure of Fe3O4 nanoparticles [37]. It is evident from Fig. 2b and c that the same characteristic peaks for Nano-Fe3O4–SiO2 and Nano-Fe3O4–SiO2–NH2 were obtained and these refer to the stability of the crystalline phase of Fe3O4 nano-sorbent during silica coating and surface amino functionalization. The successful coating of silica shell was confirmed by

the presence of the new broad peak at 2h  22–26° which is corresponding to the amorphous peak of SiO2 as shown in Fig. 2b. Thus, it is important to report that the crystal structure of the magnetic core was unchanged during the functionalization process [32]. The morphology and structure of Nano-Fe3O4–SiO2–NH2 sorbent was characterized by the SEM and TEM as shown in Figs. 3 and 4, respectively. The SEM image of Nano-Fe3O4–SiO2–NH2 sorbent exhibited a homogeneous particles distribution in the range of 19–44 nm size. However, the TEM image of Nano-Fe3O4–SiO2– NH2 sorbent gives more and clear evidence for the shape of particles as well as their distributions in the range of 4.71–9.14 nm.

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Fig. 4. TEM image of Nano-Fe3O4–SiO2–NH2 sorbent.

The thermal gravimetric analysis was used to study and evaluate the possible thermal stability/degradation processes of microwave synthesized magnetic nano-sorbent. The TGA thermogram of Nano-Fe3O4–SiO2–NH2 sorbent is shown in Fig. 5. Two thermal degradation steps are evident, the first decomposition step is produced in the temperature range of 24.63–93.29 °C due to the possible desorption of surface loaded water molecules with a percentage loss corresponding to 3.468%. The second decomposition step is mainly focused on the temperature range of 302.08– 441.09 °C with a percentage loss corresponding to 5.220% which is generally produced by the facile thermal decomposition of loaded organic molecule, 3-aminopropyltriethoxysilane, from the surface of Nano-Fe3O4–SiO2–NH2 sorbent [35]. The collected results of microwave synthesized magnetic NanoFe3O4–SiO2–NH2 sorbent confirm the suitability of this technique to design and prepare other new sorbents and biosorbents in a simple, fast and low cost approach. 3.2. Microwave-enforced sorption of heavy metals on the surface of Nano-Fe3O4–SiO2–NH2 sorbent The presented microwave-assisted solid phase extraction technique of heavy metals can be simply referred as a high performance procedure which is based on a short time heating of the target metal ion solution in contact with the selected nanosorbent. The dissolved metal ion in solution is thus allowed to react for a short period of time under the microwave heating energy and finally enforced to bind and sorb on the surface of a solid nanomaterial. This process is highly dependent on the characteristics of the interacting metal ion as well as nano-sorbent. The proposed microwave-enforced sorption and solid phase extraction technique affords a fast equilibrium condition in only few seconds to allow the transfer of metal ion of interest from the sample matrix to the surface of nano-sorbent. This methodology is similar to the microwave-assisted extraction (MAE) technique except that the organic solvent has been replaced by the nano-sorbent in an attempt to establish this procedure as a green extraction process. The suggested microwave-enforced sorption processes of Pb(II), Cu(II), Cd(II) and Hg(II) by Nano-Fe3O4–SiO2–NH2 sorbent were studied and accomplished using a microwave oven adjusted to 1400-W output power. In this experiment, a 10 mL solution of

Fig. 5. TGA thermogram of Nano-Fe3O4–SiO2–NH2 sorbent.

Table 1 Sorption capacity values of different metal ions by Nano-Fe3O4–SiO2–NH2 sorbent using microwave-assisted solid extraction. Time (s)

Temperature (°C)

Metal capacity in lmol g1 Pb(II)

Cu(II)

Cd(II)

Hg(II)

5 10 15 20 25 30

26 32 38 43 53 65

1250 1250 1300 1200 1200 1200

850 900 950 1000 1050 1050

300 300 350 350 350 350

150 200 250 300 350 350

0.01 mol L1 of either Pb(II), Cu(II), Cd(II) or Hg(II) was added to a 10.0 ± 1.0 mg sample of Nano-Fe3O4–SiO2–NH2 sorbent. The time of reaction in each test was adjusted to 5.0, 10.0, 15.0, 20.0, 25.0 and 30.0 s. The temperatures of these solutions were measured after the selected microwave heating period and these were found as 26 °C, 32 °C, 38 °C, 43 °C, 53 °C and 65 °C, respectively. However, the heating time above 30.0 s was found to partially evaporate the solution. The results of this study are compiled in Table 1 to represent the variation in the determined lmol g1 metal capacity values of Pb

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M.E. Mahmoud et al. / Chemical Engineering Journal 293 (2016) 200–206 Table 2 Comparison of the metal capacity values by Nano-Fe3O4–SiO2–NH2 sorbent with previously reported data. Metal ion

Metal capacity (lmol g1)

Reaction temperature (°C)

Reaction time

Sorption method

Pb(II)

1300 370 450 540

38 25 35 45

15 s 24 h

Microwave technique (This work) Incubation system Ref. [31]

Cu(II)

1050 470 600 690

53 25 35 45

25 s 24 h

Microwave technique (This work) Incubation system Ref. [31]

Cd(II)

350 200 270 330

38 25 35 45

15 s 24 h

Microwave technique (This work) Incubation system Ref. [31]

Hg(II)

300 –

25 –

25 s –

Microwave technique (This work) Incubation system Ref. [31]

(II), Cu(II), Cd(II) and Hg(II) versus the change in the microwave heating reaction time and temperature. Several important points can be outlined using the proposed microwave-assisted technique. As a general trend, it is evident that excellent metal sorption capacity values of Pb(II), Cu(II), Cd(II) and Hg(II) by Nano-Fe3O4–SiO2– NH2 sorbent were characterized as 1250, 850, 300 and 150 lmol g1, respectively after only 5.0 s of heating at 26 °C. However, the binding process between Nano-Fe3O4–SiO2–NH2 sorbent and metal ion is mainly attributed to a complex formation mechanism via surface loaded amino groups and metal ion. On the other hand, each metal was found to behave differently under the microwave assisted heating in presence of the Nano-Fe3O4– SiO2–NH2 sorbent. Pb(II) is the highest extracted metal ions at all heating time and temperature values and the maximum metal capacity value was identified as 1300 lmol g1 after heating in the microwave oven for 15 s at 38 °C. It is also evident that the metal capacity value was found to decrease to 1200 lmol g1 upon increasing the heating time above 15 s. This behavior may be attributed to the possible desorption of the adsorbed Pb(II) from the surface of Nano-Fe3O4–SiO2–NH2 sorbent at higher temperature. On the other hand, Cu(II), Cd(II) and Hg(II) were found to reach to the equilibrium conditions and their maximum metal capacity values were found to correspond to 1050 lmol g1 (time = 25 s and temperature = 53 °C), 350 lmol g1 (time = 15 s and temperature = 38 °C), 350 lmol g1 (time = 25 s and temperature = 53 °C), respectively. In addition, no loss of the already adsorbed Cu(II), Cd(II) and Hg(II) from the surface of NanoFe3O4–SiO2–NH2 sorbent upon heating from 53 °C to 65 °C, 38 °C to 65 °C and 53 °C to 65 °C, respectively as listed in Table 1. The outlined results confirm that Cu(II), Cd(II) and Hg(II) are more stable than Pb(II) with respect to their microwave-enforced sorption and solid phase extraction processes by Nano-Fe3O4–SiO2– NH2 sorbent. Finally, the superiority of this methodology has been outlined and compared with previously reported data [31] as listed in Table 2. 4. Conclusion The collected data from this study confirm the validity of microwave-enforced sorption and solid phase extraction technique for metal ions uptake from their aqueous solutions. The preliminary results refer to the possible extraction of heavy metal ions from their matrices in only few seconds. The characterized maximum metal capacity values using microwave-assisted heating and sorption of Pb(II), Cu(II), Cd(II) and Hg(II) by Nano-Fe3O4– SiO2–NH2 sorbent were established in few seconds, viz. 15–25 s. However, more studies are needed to explore and generalize the

applications of this technique for sorption of other organic and inorganic pollutants from their matrices. Several other important experimental controlling parameters must be also investigated. However, some studies are being conducted to address these issues and the results will be published shortly. Acknowledgement The authors of this manuscript acknowledge the time and effort that Dr. Moustafa Elkholy spent as a Ph.D co-supervisor for Ghada A.A. Ibrahim until he deceased last year. References [1] C.R. Vitasari, M. Gramblicˇka, K. Gibcus, T.J. Visser, R. Geertman, B. Schuur, Separating closely resembling steroids with ionic liquids in liquid liquid extraction systems, Sep. Purif. Technol. 155 (2015) 58–65. [2] K. Li, M. Landriault, M. Fingas, M. Llompar, Accelerated solvent extraction, (ASE) of environmental organic compounds in soils using a modified supercritical fluid extractor, J. Hazard. Mater. 102 (2003) 93–104. [3] S. Chen, P.L. Urban, On-line monitoring of Soxhlet extraction by chromatography and mass spectrometry to reveal temporal extract profiles, Anal. Chim. Acta 881 (2015) 74–81. [4] F. Rezaei, Y. Yamini, H. Asiabi, S. Seidi, M. Rezazadeh, Supercritical fluid extraction followed by nanostructured supramolecular solvent extraction for extraction of levonorgestrel and megestrol from whole blood samples, J. Supercrit. Fluids 107 (2016) 392–399. [5] W. Setyaningsih, I.E. Saputro, M. Palma, C.G. Barroso, Pressurized liquid extraction of phenolic compounds from rice (Oryza sativa) grains, Food Chem. 192 (2016) 452–459. [6] H. Wang, J. Ding, Nan Ren, Recent advances in microwave-assisted extraction of trace organic pollutants from food and environmental samples, TrAC Trends Anal. Chem. 75 (2016) 197–208. [7] A. Franco-Vega, N. Ramírez-Corona, E. Palou, A. López-Malo, Estimation of mass transfer coefficients of the extraction process of essential oil from orange peel using microwave assisted extraction, J. Food Eng. 170 (2016) 136–143. [8] N. Mketo, P.N. Nomngongo, J.C. Ngila, An innovative microwave-assisted digestion method with diluted hydrogen peroxide for rapid extraction of trace elements in coal samples followed by inductively coupled plasma-mass spectrometry, Microchem. J. 124 (2016) 201–208. [9] D. Shen, N. Liu, C. Dong, R. Xiao, S. Gu, Catalytic solvolysis of lignin with the modified HUSYs in formic acid assisted by microwave heating, Chem. Eng. J. 270 (2015) 641–647. [10] M.E. Mahmoud, Gehan M. Nabil, Sarah M.E. Mahmoud, High performance nano-zirconium silicate adsorbent for efficient removal of copper (II), cadmium (II) and lead (II), J. Environ. Chem. Eng. 3 (2015) 1320–1328. [11] M.E. Mahmoud, Azza E.H. Abdou, Gehan M. Nabil, Facile microwave-assisted fabrication of nano-zirconium silicate-functionalized-3aminopropyltrimethoxysilane as a novel adsorbent for superior removal of divalent ions, J. Ind. Eng. Chem. 32 (2015) 365–372. [12] T.M. Abdel-Fattah, M.E. Mahmoud, S.B. Ahmed, M.D. Huff, J.W. Lee, S. Kumar, Biochar from woody biomass for removing metal contaminants and carbon sequestration, J. Ind. Eng. Chem. 22 (2015) 103–109. [13] Y. Huang, Q. Zhou, G. Xie, Development of micro-solid phase extraction with titanate nanotube array modified by cetyltrimethylammonium bromide for sensitive determination of polycyclic aromatic hydrocarbons from environmental water samples, J. Hazard. Mater. 193 (2011) 82–89.

206

M.E. Mahmoud et al. / Chemical Engineering Journal 293 (2016) 200–206

[14] A.R. Ghiasvand, S. Hajipour, Direct determination of acrylamide in potato chips by using headspace solid phase micro-extraction coupled with gas chromatography-flame ionization detection, Talanta 146 (2016) 417–422. [15] M. Ranic, M. Nikolic, M. Pavlovic, A. Buntic, S. Siler-Marinkovic, S. DimitrijevicBrankovic, Optimization of recent advances in microwave-assisted extraction of natural antioxidants from spent espresso coffee grounds by response surface methodology, J. Clean. Prod. 80 (2014) 69–79. [16] N. Wang, P. Wang, Study and application status of microwave in organic wastewater treatment – a review, Chem. Eng. J. 283 (2016) 193–214. [17] U. Riaz, S.M. Ashraf, S. Kumar, I. Ahmad, Controlling the growth of polycarbazole within the silicate galleries using peroxides via microwaveassisted green synthesis, Chem. Eng. J. 241 (2014) 259–267. [18] Q. Zhang, S. Zhao, J. Chen, L. Zhang, Application of ionic liquid-based microwave-assisted extraction of flavonoids from Scutellaria baicalensis Georgi, J. Chromatogr. B 1002 (2015) 411–417. [19] L. Sanchez-Prado, C. Garcia-Jares, T. Dagnac, M. Llompart, Microwave-assisted extraction of emerging pollutants in environmental and biological samples before chromatographic determination, TrAC Trends Anal. Chem. 71 (2015) 119–143. [20] M. Ghanei-Motlagh, M. Fayazi, M.A. Taher, A. Jalalinejad, Application of magnetic nanocomposite modified with a thiourea based ligand for the preconcentration and trace detection of silver (I) ions by electrothermal atomic absorption spectrometry, Chem. Eng. J. 290 (2016) 53–62. [21] Z. Wei, S. Sandron, A.T. Townsend, P.N. Nesterenko, B. Paull, Determination of trace labile copper in environmental waters by magnetic nanoparticle solid phase extraction and high-performance chelation ion chromatography, Talanta 135 (2015) 155–162. [22] X. Ding, Y. Wang, Y. Wang, Q. Pan, J. Chen, Y. Huang, K. Xu, Preparation of magnetic chitosan and graphene oxide-functional guanidinium ionic liquid composite for the solid-phase extraction of protein, Anal. Chim. Acta 861 (2015) 36–46. [23] J. Gómez-Pastora, E. Bringas, I. Ortiz, Recent progress and future challenges on the use of high performance magnetic nano-adsorbents in environmental applications, Chem. Eng. J. 256 (2014) 187–204. [24] G. Giakisikli, A.N. Anthemidis, Magnetic materials as sorbents for metal/ metalloid preconcentration and/or separation. A review, Anal. Chim. Acta 789 (2013) 1–16. [25] V.K. Gupta, A. Nayak, Cadmium removal and recovery from aqueous solutions by novel adsorbents prepared from orange peel and Fe2O3 nanoparticles, Chem. Eng. J. 180 (2012) 81–90.

[26] J. Chen, X. Zhu, Magnetic solid phase extraction using ionic liquid-coated core– shell magnetic nanoparticles followed by high-performance liquid chromatography for determination of Rhodamine B in food samples, Food Chem. 200 (2016) 10–15. [27] S. Zhang, H. Luo, Y. Zhang, X. Li, J. Liu, Q. Xu, Z. Wang, In situ magnetic solid phase extraction coupled with HPLC-ICP-MS for mercury speciation in environmental water, Microchem. J. 126 (2016) 25–31. [28] M.E. Mahmoud, S.B. Ahmed, M.M. Osman, T.M. Abdel-Fattah, A novel composite of nanomagnetite-immobilized-baker’s yeast on the surface of activated carbon for magnetic solid phase extraction of Hg(II), Fuel 139 (2015) 614–621. [29] M.E. Mahmoud, A.A. Yakout, K.H. Hamza, M.M. Osman, Novel nano-Fe3O4encapsulated-dioctylphthalate and linked triethylenetetramine sorbents for magnetic solid phase removal of heavy metals, J. Ind. Eng. Chem. 25 (2015) 207–215. [30] J.B. Mamania, A.J. Costa-Filho, D.R. Cornejo, E.D. Vieira, L.F. Gamarra, Synthesis and characterization of magnetite nanoparticles coated with lauric acid, Mater. Charact. 81 (2013) 28–36. [31] J. Wang, S. Zheng, Y. Shao, J. Liu, Z. Xu, D. Zhu, Amino-functionalized Fe3O4@SiO2 core–shell magnetic nanomaterial as a novel adsorbent for aqueous heavy metals removal, J. Colloid Interface Sci. 349 (2010) 293–299. [32] M. Mahdavi, M.B. Ahmad, M.J. Haron, Y. Gharayebi, K. Shameli, B. Nadi, Fabrication and characterization of SiO2/(3-aminopropyl)triethoxysilanecoated magnetite nanoparticles for lead (II) removal from aqueous solution, J. Inorg. Organomet. Polym. 23 (2013) 599–607. [33] E. Karaoglu, M.M. Summak, A. Baykal, H. Sozeri, M.S. Toprak, Synthesis and characterization of catalytically activity Fe3O4-3-aminopropyl-triethoxysilane/ Pd nanocomposite, Inorg. Organomet. Polym. 23 (2013) 409–417. [34] Y.S. Li, J.S. Church, A.L. Woodhead, Infrared and Raman spectroscopic, studies on iron oxide magnetic nano-particles and their surface modifications, J. Magn. Magn. Mater. 324 (2012) 1543–1550. [35] M.E. Mahmoud, M.S. Abdelwahab, E.M. Fathallah, Design of novel nanosorbents based on nano-magnetic iron oxide-bound-nano-silicon oxideimmobilized-triethylenetetramine for implementation in water treatment of heavy metals, Chem. Eng. J. 223 (2013) 318–327. [36] F. Dang, N. Enomoto, J. Hojo, K. Enpuku, Sonochemical coating of magnetite nanoparticles with silica, Ultrason. Sonochem. 17 (2010) 193–199. [37] X. Du, J. He, J. Zhu, L. Sun, S. An, Ag-deposited silica-coated Fe3O4 magnetic nanoparticles catalyzed reduction of p-nitrophenol, Appl. Surf. Sci. 258 (2012) 2717–2723.