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A simple synthesis of magnetically modified zeolite
Powder Technology 177 (2007) 99 – 101 www.elsevier.com/locate/powtec
Short communication
A simple synthesis of magnetically modified zeolite In Wook Nah a,⁎, Kyung-Yub Hwang a , Yong-Gun Shul b a
Division of Water Environment Research Center, Korea Institute of Science and Technology, Republic of Korea b Department of Chemical Engineering, Yonsei University, Republic of Korea Received 4 May 2006; received in revised form 10 January 2007; accepted 23 February 2007 Available online 12 March 2007
Abstract A composite of zeolite with magnetite was prepared by urethane coating. Formation of magnetic modified zeolite (MMZ) was confirmed by magnetization measurements and X-ray diffraction (XRD) pattern analysis. Also, scanning electron microscopic (SEM) analysis reveals the presence of zeolite and magnetite particles. It is thought that approximately 16% urethane polymer is retained in composite particle as a result of thermogravimetric analysis (TGA). © 2007 Elsevier B.V. All rights reserved. Keywords: Magnetically modified zeolite; Urethane coatings; Ion exchange
1. Introduction Magnetic carrier methods have been used widely in processes such as the separation of biological cells, the treatment of wastewater, coal desulphurization and mineral processing [1]. The essence of this method is to incorporate a discrete magnetic phase into the weakly or non-magnetic target particles to increase their magnetic susceptibility and to separate these agglomerates by magnetic separation. With this approach, Anand P. [2] could remove virtually all (99.9%) the heavy metals, such as cadmium, copper, nickel and zinc by adsorption onto ferric hydroxide flocs in a pH range of 10.5–11.0. The magnetic phase was obtained from ferric sulphate, as well as a small quantity of magnetite that was added to facilitate high gradient magnetic separation. The composite was prepared by the adhesion of magnetite (Fe3O4) onto zeolite surface by urethane. These coatings, iron oxide onto zeolite require low viscosity to mix well each other. Therefore, reactive thinners are usually used. In the case of reactive polyurethane coatings, a distinction must be made between systems with one or two and more components
⁎ Corresponding author. Division of Water Environment Research Center, KIST, P.O. Box 131, Cheongryang, Seoul, Korea. Tel.: +82 2 958 5828; fax: +82 2 958 5839. E-mail address: [email protected] (I.W. Nah). 0032-5910/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.powtec.2007.02.044
[3]. One-component systems may crosslink by baking or at room temperature. One-component polyurethane coatings which cure at room temperature include those systems with polyunsaturated hydrocarbon chains which crosslink with oxygen. These are produced by, for example, the incorporation of suitable fatty alcohols into the polyurethane polymer. The addition of driers (catalysts) based on salts cobalt, lead and manganese (primary driers) and of magnesium, zinc, calcium and strontium (auxiliary driers) allows these products to crosslink in air. Depending on the resin structure and the ambient conditions, different reactions occur. The crosslinking reaction is usually based on a radical mechanism with secondary reactions yielding ketones, aldehydes and other oxidation products. One-component application has the need for careful predrying of possibly moist pigments [3]. This research examined how to prepare MMZ using urethane by a simple method and characterization of MMZ.
Table 1 Magnetization, magnetic coercivity (Hc) and BET surface area for MMZ Sample
Bulk magnetization (emu/g)
Magnetic coercivity, Hc (Oe)
BET surface area (m2/g)
Magnetite Pure zeolite MMZ
90 0
92 0
9 1
52
84
2.2
100
I.W. Nah et al. / Powder Technology 177 (2007) 99–101
2. Experimental work Zeolite samples used in this study were synthetic zeolite, 200 mesh (74 μm), BET of 1 m2 g− 1 from Wako. Magnetite samples (Bayferrox) were in a range from 1 to 10 μm in size, BET of 9 m2 g− 1 from Bayer 5 g of zeolite was mixed with 5 g of
Fig. 2. XRD patterns for MMZ.
magnetite in 5 g of urethane (UT578, Kumgang Korea Chemical Co.) and 20 g of thinner acting as an adhesive with zeolite and magnetite, which was dried at 60 °C for 5 h by vacuum drying. After drying, MMZ was evidenced from their attraction to a permanent magnet and was grinded by ball milling for 3 h and washed by de-ionized water three times. Surface area (BET) were measured by nitrogen adsorption at 77 K using an ASAP-2010 porosimeter from Micromeritics Corporation, GA. The samples were degassed at 623 K and 1.333 × 10− 3 Pa overnight prior to the adsorption experiments. The morphology analysis was performed on scanning electron microscopy (SEM) analyzer (Hitachi S-4100). X-ray diffraction (XRD) patterns were taken on a Rigaku D/max-2500 instrument with Cu Ka radiation. The magnetic properties were determined by vibrating-sample magnetometer (VSM, Lake shore, 7400, USA, 25 °C). Thermogravimetric analysis (TGA) was measured by thermogravimetric analyzer (TGA 2050,TA Instrument, USA). 3. Results and discussion 3.1. Bulk magnetization, magnetic coercivity and BET surface area of MMZ particles
Fig. 1. SEM images of (a) magnetite, (b) zeolite and (c) MMZ.
Table 1 shows for the magnetite, MMZ and pure zeolite a BET surface area of 9, 2.2 and 1 m2 g− 1, respectively. Additionally, for the magnetite, MMZ and pure zeolite, bulk magnetization was 90, 52 and 0 emu/g and magnetic coercivity (Hc) was 92, 84 and 0 Oe,
I.W. Nah et al. / Powder Technology 177 (2007) 99–101
101
There is no significant shift of characteristic peaks of magnetite and zeolite in composite particles, indicating that the reaction has not altered the crystalline structures of the magnetite and zeolite. Therefore, it is concluded that no strong specific chemical interactions occurred between the magnetite and urethane or between zeolite and urethane. 3.4. TGA analysis of MMZ particles
respectively. It is interesting to note that MMZ showed an increase of BET surface area, bulk magnetization and coercivity compared to the pure zeolite. The main reason for the surface area, bulk magnetization and coercivity increases in MMZ is due to the presence of magnetite, which has larger surface area, bulk magnetization and coercivity compared with the pure zeolite.
The urethane polymer content of the composite particles was determined through weight loss at 1000 °C in air using thermogravimetric analysis (TGA). The weight loss curves of magnetite, zeolite and composite particle are shown in Fig. 3. The TGA curves of both pure zeolite and MMZ particle reveal that thermal events occur in two temperature ranges: 25–200 °C and 200–1000 °C. Magnetite shows thermally stable as weight loss is negligible until 1000 °C. In the first zone of Fig. 3(c), the decrease of weight is 7.46% which can be attributed to desorption of water. The second weight loss corresponds to the urethane decomposition. The loss value of MMZ particles is 19.9%. It can be calculated that there is approximately 16% urethane polymer in composite particle after drying, because MMZ is composed of the same amount of magnetite, urethane and zeolite which has approximately 13% water, as shown in Fig. 3(b). As for the stability at different pH, MMZ is more resistant to acid than other magnetic zeolite [4]. Moreover, it is reported that the presence of magnetite and urethane in composite is not inhibiting the adsorption of metal [4].
3.2. Morphology of MMZ particles
4. Conclusion
Fig. 1 presents scanning electron micrographs (SEM) of (a) magnetite, (b) zeolite and (c) composite (MMZ), respectively. The SEM image reveals the presence of zeolite and magnetite particles. Because urethane has the ability to strongly interact zeolite with magnetite through bonding at the interfaces and to be aggregated MMZ agglomerates, and grinding by ball milling allows the formation of fine MMZ particle size (80–100 μm), it is thought that zeolite could interconnect magnetite by urethane acting as adhesive. However, non-uniform distribution of zeolite and magnetite can be confirmed by Fig. 1.
The composite of magnetite onto zeolite surface was prepared by urethane coating. The magnetization measurement shows that magnetic phase is retained in MMZ. SEM images and XRD patterns revealed distinctive morphological and crystalline patterns of magnetite and zeolite composite. The reaction has not altered the morphology and crystalline structure of the parent magnetite and zeolite. In addition, the simple preparation and the good chemical stability could facilitate its application in many fields.
Fig. 3. The weight loss curves of (a) magnetite, (b) zeolite and (c) MMZ.
3.3. X-ray diffraction patterns of MMZ particles XRD results of magnetite, zeolite and their composite MMZ (Fig. 2) showed the characteristic peaks of crystalline magnetite, Fe3O4 at 2θ = 35.44, 62.58, 30.1 and 56.96 and of crystalline Na-aluminosilicate at 2θ = 29.88, 23.92, 27.04, 34.1, 7.04, 10.04, 12.34 and 16.04. The urethane presented an amorphous pattern as expected for polymer.
References [1] P. Parsonage, Coating and carrier methods for enhancing magnetic and flotation separations, Colloid Chem. Miner. Process. Elsevier, Amsterdam, 1992, pp. 331–360. [2] P. Anand, J.E. Etzel, F.J. Friedlaender, Heavy metals removal by high gradient magnetic separation, IEEE Trans. Magn. Mg-21 5 (1985) 2062–2064. [3] Manfred Bock, Polyurethanes for coatings, Vinentz (1998) 42–45. [4] I.W. Nah, K.Y. Hwang, C. Jeon, H.B. Choi, Removal of Pb ion from water by magnetically modified zeolite, Min. Eng. 19 (2006) 1452–1455.
Short communication
A simple synthesis of magnetically modified zeolite In Wook Nah a,⁎, Kyung-Yub Hwang a , Yong-Gun Shul b a
Division of Water Environment Research Center, Korea Institute of Science and Technology, Republic of Korea b Department of Chemical Engineering, Yonsei University, Republic of Korea Received 4 May 2006; received in revised form 10 January 2007; accepted 23 February 2007 Available online 12 March 2007
Abstract A composite of zeolite with magnetite was prepared by urethane coating. Formation of magnetic modified zeolite (MMZ) was confirmed by magnetization measurements and X-ray diffraction (XRD) pattern analysis. Also, scanning electron microscopic (SEM) analysis reveals the presence of zeolite and magnetite particles. It is thought that approximately 16% urethane polymer is retained in composite particle as a result of thermogravimetric analysis (TGA). © 2007 Elsevier B.V. All rights reserved. Keywords: Magnetically modified zeolite; Urethane coatings; Ion exchange
1. Introduction Magnetic carrier methods have been used widely in processes such as the separation of biological cells, the treatment of wastewater, coal desulphurization and mineral processing [1]. The essence of this method is to incorporate a discrete magnetic phase into the weakly or non-magnetic target particles to increase their magnetic susceptibility and to separate these agglomerates by magnetic separation. With this approach, Anand P. [2] could remove virtually all (99.9%) the heavy metals, such as cadmium, copper, nickel and zinc by adsorption onto ferric hydroxide flocs in a pH range of 10.5–11.0. The magnetic phase was obtained from ferric sulphate, as well as a small quantity of magnetite that was added to facilitate high gradient magnetic separation. The composite was prepared by the adhesion of magnetite (Fe3O4) onto zeolite surface by urethane. These coatings, iron oxide onto zeolite require low viscosity to mix well each other. Therefore, reactive thinners are usually used. In the case of reactive polyurethane coatings, a distinction must be made between systems with one or two and more components
⁎ Corresponding author. Division of Water Environment Research Center, KIST, P.O. Box 131, Cheongryang, Seoul, Korea. Tel.: +82 2 958 5828; fax: +82 2 958 5839. E-mail address: [email protected] (I.W. Nah). 0032-5910/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.powtec.2007.02.044
[3]. One-component systems may crosslink by baking or at room temperature. One-component polyurethane coatings which cure at room temperature include those systems with polyunsaturated hydrocarbon chains which crosslink with oxygen. These are produced by, for example, the incorporation of suitable fatty alcohols into the polyurethane polymer. The addition of driers (catalysts) based on salts cobalt, lead and manganese (primary driers) and of magnesium, zinc, calcium and strontium (auxiliary driers) allows these products to crosslink in air. Depending on the resin structure and the ambient conditions, different reactions occur. The crosslinking reaction is usually based on a radical mechanism with secondary reactions yielding ketones, aldehydes and other oxidation products. One-component application has the need for careful predrying of possibly moist pigments [3]. This research examined how to prepare MMZ using urethane by a simple method and characterization of MMZ.
Table 1 Magnetization, magnetic coercivity (Hc) and BET surface area for MMZ Sample
Bulk magnetization (emu/g)
Magnetic coercivity, Hc (Oe)
BET surface area (m2/g)
Magnetite Pure zeolite MMZ
90 0
92 0
9 1
52
84
2.2
100
I.W. Nah et al. / Powder Technology 177 (2007) 99–101
2. Experimental work Zeolite samples used in this study were synthetic zeolite, 200 mesh (74 μm), BET of 1 m2 g− 1 from Wako. Magnetite samples (Bayferrox) were in a range from 1 to 10 μm in size, BET of 9 m2 g− 1 from Bayer 5 g of zeolite was mixed with 5 g of
Fig. 2. XRD patterns for MMZ.
magnetite in 5 g of urethane (UT578, Kumgang Korea Chemical Co.) and 20 g of thinner acting as an adhesive with zeolite and magnetite, which was dried at 60 °C for 5 h by vacuum drying. After drying, MMZ was evidenced from their attraction to a permanent magnet and was grinded by ball milling for 3 h and washed by de-ionized water three times. Surface area (BET) were measured by nitrogen adsorption at 77 K using an ASAP-2010 porosimeter from Micromeritics Corporation, GA. The samples were degassed at 623 K and 1.333 × 10− 3 Pa overnight prior to the adsorption experiments. The morphology analysis was performed on scanning electron microscopy (SEM) analyzer (Hitachi S-4100). X-ray diffraction (XRD) patterns were taken on a Rigaku D/max-2500 instrument with Cu Ka radiation. The magnetic properties were determined by vibrating-sample magnetometer (VSM, Lake shore, 7400, USA, 25 °C). Thermogravimetric analysis (TGA) was measured by thermogravimetric analyzer (TGA 2050,TA Instrument, USA). 3. Results and discussion 3.1. Bulk magnetization, magnetic coercivity and BET surface area of MMZ particles
Fig. 1. SEM images of (a) magnetite, (b) zeolite and (c) MMZ.
Table 1 shows for the magnetite, MMZ and pure zeolite a BET surface area of 9, 2.2 and 1 m2 g− 1, respectively. Additionally, for the magnetite, MMZ and pure zeolite, bulk magnetization was 90, 52 and 0 emu/g and magnetic coercivity (Hc) was 92, 84 and 0 Oe,
I.W. Nah et al. / Powder Technology 177 (2007) 99–101
101
There is no significant shift of characteristic peaks of magnetite and zeolite in composite particles, indicating that the reaction has not altered the crystalline structures of the magnetite and zeolite. Therefore, it is concluded that no strong specific chemical interactions occurred between the magnetite and urethane or between zeolite and urethane. 3.4. TGA analysis of MMZ particles
respectively. It is interesting to note that MMZ showed an increase of BET surface area, bulk magnetization and coercivity compared to the pure zeolite. The main reason for the surface area, bulk magnetization and coercivity increases in MMZ is due to the presence of magnetite, which has larger surface area, bulk magnetization and coercivity compared with the pure zeolite.
The urethane polymer content of the composite particles was determined through weight loss at 1000 °C in air using thermogravimetric analysis (TGA). The weight loss curves of magnetite, zeolite and composite particle are shown in Fig. 3. The TGA curves of both pure zeolite and MMZ particle reveal that thermal events occur in two temperature ranges: 25–200 °C and 200–1000 °C. Magnetite shows thermally stable as weight loss is negligible until 1000 °C. In the first zone of Fig. 3(c), the decrease of weight is 7.46% which can be attributed to desorption of water. The second weight loss corresponds to the urethane decomposition. The loss value of MMZ particles is 19.9%. It can be calculated that there is approximately 16% urethane polymer in composite particle after drying, because MMZ is composed of the same amount of magnetite, urethane and zeolite which has approximately 13% water, as shown in Fig. 3(b). As for the stability at different pH, MMZ is more resistant to acid than other magnetic zeolite [4]. Moreover, it is reported that the presence of magnetite and urethane in composite is not inhibiting the adsorption of metal [4].
3.2. Morphology of MMZ particles
4. Conclusion
Fig. 1 presents scanning electron micrographs (SEM) of (a) magnetite, (b) zeolite and (c) composite (MMZ), respectively. The SEM image reveals the presence of zeolite and magnetite particles. Because urethane has the ability to strongly interact zeolite with magnetite through bonding at the interfaces and to be aggregated MMZ agglomerates, and grinding by ball milling allows the formation of fine MMZ particle size (80–100 μm), it is thought that zeolite could interconnect magnetite by urethane acting as adhesive. However, non-uniform distribution of zeolite and magnetite can be confirmed by Fig. 1.
The composite of magnetite onto zeolite surface was prepared by urethane coating. The magnetization measurement shows that magnetic phase is retained in MMZ. SEM images and XRD patterns revealed distinctive morphological and crystalline patterns of magnetite and zeolite composite. The reaction has not altered the morphology and crystalline structure of the parent magnetite and zeolite. In addition, the simple preparation and the good chemical stability could facilitate its application in many fields.
Fig. 3. The weight loss curves of (a) magnetite, (b) zeolite and (c) MMZ.
3.3. X-ray diffraction patterns of MMZ particles XRD results of magnetite, zeolite and their composite MMZ (Fig. 2) showed the characteristic peaks of crystalline magnetite, Fe3O4 at 2θ = 35.44, 62.58, 30.1 and 56.96 and of crystalline Na-aluminosilicate at 2θ = 29.88, 23.92, 27.04, 34.1, 7.04, 10.04, 12.34 and 16.04. The urethane presented an amorphous pattern as expected for polymer.
References [1] P. Parsonage, Coating and carrier methods for enhancing magnetic and flotation separations, Colloid Chem. Miner. Process. Elsevier, Amsterdam, 1992, pp. 331–360. [2] P. Anand, J.E. Etzel, F.J. Friedlaender, Heavy metals removal by high gradient magnetic separation, IEEE Trans. Magn. Mg-21 5 (1985) 2062–2064. [3] Manfred Bock, Polyurethanes for coatings, Vinentz (1998) 42–45. [4] I.W. Nah, K.Y. Hwang, C. Jeon, H.B. Choi, Removal of Pb ion from water by magnetically modified zeolite, Min. Eng. 19 (2006) 1452–1455.