Environmental Advances 2 (2020) 100019 Contents lists available at ScienceDirect Environmental Advances journal homepage: www.elsevier.com/locate/envadv Zeolite synthesis from low-cost materials and environmental applications: A review Abdul Khaleque a , Md Masruck Alam b , Mozammel Hoque b , Shuvodip Mondal a , Jahid Bin Haider a , Bentuo Xu c , M.A.H. Johir d , Aneek Krishna Karmakar b , J.L. Zhou d , Mohammad Boshir Ahmed b,d,e,∗ , Mohammad Ali Moni f a Department of Applied Chemistry and Chemical Engineering, Bangabandhu Sheikh Mujibur Rahman Science and Technology University, Gopalganj 8100, Bangladesh b Department of Applied Chemistry and Chemical Engineering, University of Rajshahi, Rajshahi 6205, Bangladesh c School of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China d Center for Green Technologies, School of Civil and Environmental Engineering, University of Technology Sydney, 15, Broadway, Sydney, NSW 2007, Australia e School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea f WHO Collaborating Centre on eHealth, UNSW Digital Health, School of Public Health and Community Medicine, Faculty of Medicine, UNSW Sydney, Australia a r t i c l e i n f o Keywords: Low-cost raw materials Tetrahedral structure Modified zeolite Hydrothermal method Environmental application a b s t r a c t Zeolites with the three-dimensional structures occur naturally or can be synthesized in the laboratory. Zeolites have versatile applications such as environmental remediation, catalytic activity, biotechnological application, gas sensing and medicinal applications. Although, naturally occurring zeolites are readily available, nowadays, more emphasis is given on the synthesis of the zeolites due to their easy synthesis in the pure form, better ion exchange capabilities and uniform in size. Recently, much attention has also been paid on how zeolite is being syn- thesized from low-cost material (e.g., rice husk), particularly, by resolving the major environmental issues. Hence, the main purpose of this review is to make an effective resolution of zeolite synthesis methods together with po- tential applications in environmental engineering. Among different synthesis methods, hydrothermal method is commonly found to be used widely in the synthesis of various zeolites from inexpensive raw materials such as fly ash, rice husk ash, blast furnace slag, municipal solid waste, paper sludge, lithium slag and kaolin. Besides, future expectation in the field of synthetic zeolites research is also included. 1. Introduction Zeolites, a member of the microporous crystalline aluminosilicates family, also known as “molecular sieves”(Auerbach et al., 2004). Zeo- lite has the three-dimensional structures which are composed of the net- works of [SiO 4 ] 4− and [AlO 4 ] 5− tetrahedral linked to each other with oxygen atoms (Fig. 1a) (Chiang and Chao, 2001). Depending on the structural type, cages are formed by connecting the pore openings of defined sizes (i.e., 0.3-1.0 nm) in the tetrahedral structures. Therefore, a neutral structure is produced by neutralizing the negative charge on the lattice by the positive charge of the cations (Cejka, 2007). The gen- eral chemical composition of a zeolite is Ma/b[(AlO 2 )a(SiO 2 )y].cH 2 O, where M represents either an alkali metal or an alkaline earth metal cation, b represents the valence earth metal cation, c is the amount of water of crystallization per unit cell and a and y represent the total num- ber of the [SiO 4 ] 4− and [AlO 4 ] 5- tetrahedral in a unit cell of the zeolite, respectively (Chiang and Chao, 2001; Lakiss et al., 2020). The ratio y/a ∗ Corresponding author at: Department of Applied Chemistry and Chemical Engineering, University of Rajshahi, Rajshahi 6205, Bangladesh. E-mail address: [email protected] (M.B. Ahmed). ranges from 1.0 to 5.0. But, this value can be changed based on the structure. For example, silica-based zeolite has value of 10.0 to 100. Zeolites occur naturally as well as it can be prepared in the labora- tory. Zeolites are usually divided into two main categories: natural (e.g., clinoptilolite, mordenite and garronite), and the synthetic zeolite (e.g., zeolite A, P, X and Y) (Oruji et al., 2018; Metropoulos et al., 1993). At present, there are over two hundred types of zeolites. These are based on the silica-alumina ratio. It was found that natural zeolites have better resistivity and thermal stability in the different environments. Their thermal stability and chemical resistance increase with the in- crease of silica-alumina ratio as well as in the presence of alkali cations in the zeolite framework (Büchel et al., 2008; Georgiev et al., 2009). A lattice unit, which is the building block of the repeating units and the relationship between the tetrahedral primary building unit (PBU) and secondary building unit (SBU) structure, is shown in Fig. 1b. The SBU is basically the main unit of the zeolite framework. Until now, there are nine known SBUs available (Lakiss et al., 2020). https://doi.org/10.1016/j.envadv.2020.100019 Received 14 August 2020; Received in revised form 11 October 2020; Accepted 24 October 2020 2666-7657/© 2020 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Zeolite synthesis from low-cost materials and environmental applications: A review
May 03, 2023
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