Contents lists available at ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay Research Paper Synthesis and characterization of zeolite LTA by hydrothermal transformation of a natural Algerian palygorskite Lamia Dali Youcef a , Alberto López-Galindo b , Cristóbal Verdugo-Escamilla b , Lala Setti Belaroui a,c, ⁎ a Laboratoire de Chimie des Matériaux (LCM), Faculté des Sciences Exactes et Appliquées, Université Oran1, Oran El M'Naouer, Oran BP 1524, Algeria b Instituto Andaluz de Ciencias de la Tierra, Consejo Superior de Investigaciones Científicas-University of Granada, Avda. de las Palmeras, 4, 18100 Armilla, Granada, Spain c Département de Pharmacie, Faculté de Médecine, Université Oran1, BP 1510 Oran El M'Naouer, Oran, Algeria ARTICLE INFO Keywords: Algerian palygorskite Hydrothermal synthesis Zeolite LTA ABSTRACT A palygorskitic-rich Algerian clay (Sif Pal) has been selected as Si source to synthesize zeolite LTA through a hydrothermal treatment by using sodium aluminate. Sif Pal is activated under reflux using hydrochloric acid solutions at different concentrations (4, 6 and 7 mol.L -1 ) in a ratio of 50 g.L -1 and then analysed using XRD, SEM and XRF analysis. The selected product (PalH1) is mixed with NaOH solutions at different concentrations (1, 2, 3, 4 and 5 mol.L -1 ), diverse NaAl 2 O 3 quantities (1, 2, 3 and 5 g) and analysed after several nucleation (1, 2, 3 and 5 h) and crystallization (6, 18 and 24 h) times to check the influence of these parameters on the synthesis of zeolite LTA. To obtain almost pure (> 98%) zeolite LTA, the better experimental conditions were: 3 mol.L -1 of NaOH solutions, 3 g of sodium aluminate, 3 h for nucleation and 24 h for crystallization. 1. Introduction Algeria's economic growth is based on the development of a strong industry aiming to substitute the large amount of imported products. However, in regards to the chemical industry, Algeria focuses on the formulation and not on the production and manufacturing, which leads it to a heavy dependence of other developed countries. According to the International Zeolite Association (2019), until now there are 234 dis- covered zeolite framework type codes. In 2006, however, only 170 molecular sieve structures were registered under the Structure Com- mission of the International Zeolite Association, and only 17 of them have commercial interest (Maesen, 2007). The annual market for syn- thetic zeolites and molecular sieves was developed vastly to 1,800,000 ton worldwide in 2008 (Davis and Inoguchi, 2009). Zeolite LTA is the universal type of synthetic zeolites in the area of detergents and water softening due to its large ion exchange capacity (Maesen and Marcus, 2001), mechanical strength and particular crystal shape in addition to its safety for environment (Hui and Chao, 2006). Zeolites, defined as hydrated aluminosilicate minerals with a three dimensional open structure, are very useful in a large number of en- vironmental, industrial and pharmacological applications because of their high cation exchange capacity, their large surface area, and their structural characteristics which facilitate pollutant absorption and en- capsulation. Synthetic zeolites are used commercially more often than natural zeolites due to their purity and crystallinity, in addition to the uniformity of particle sizes (Breck, 1974; Szostak, 1998). The pre- paration of synthetic zeolites with chemical sources of silica and alu- mina is expensive, hence the need to reduce the cost of preparing these materials using natural sources such as clays. Desirable characteristics of zeolites may be enhanced by synthesis procedures using several source materials such as fly ash (Shigemoto et al., 1993, 1994; Querol et al., 1995, 1997, 2002; Berkgaut and Singer, 1996; Chang and Shih, 1998; Molina and Poole, 2004; Inada et al., 2005; Belviso et al., 2010a, 2010b, 2011), asbestos (Saada et al., 2009), kaolinite (Rocha et al., 1991; Murat et al., 1992; Gualtieri and Bellotto, 1998; Okada et al., 1998; Park et al., 2001; Lapides and Heller- Kallai, 2007; Ríos et al., 2009; Du and Yang, 2010; Gougazeh and Buhl, 2014; Ayele et al., 2015), montmorillonite (Temuujin et al., 2004), palygorskite (Jiang et al., 2011, 2012a, 2012b, 2014), saponite (Okada et al., 2007), sepiolite (Aznar et al., 1996), talc (Yang et al., 2006), and vermiculite (Maqueda et al., 2007; Temuujin et al., 2003), which were used to replace sodium silicate in the synthesis of zeolite LTA for the reduction of synthesis costs and the protection of the environment. Zeolite LTA, also known as zeolite A [Na 12 (Al 12 Si 12 O 48 ).27H 2 O], has a three-dimensional pore structure, with pores running perpendi- cular to each other in the x, y and z planes, and it is made up of sec- ondary building units 4, 6, 8 and 4–4 as an arrangement of β-cage [4 8 6 6 ] pseudo-cornershare via 4–4 structure units showing α- cage [4 12 6 8 https://doi.org/10.1016/j.clay.2020.105690 Received 14 October 2019; Received in revised form 2 May 2020; Accepted 19 May 2020 ⁎ Corresponding authors. E-mail address: belaroui.lalasetti@univ-oran1.dz (L.S. Belaroui). Applied Clay Science 193 (2020) 105690 0169-1317/ © 2020 Elsevier B.V. All rights reserved. T