ORIGINAL PAPER Novel bentonite/zeolite-NaP composite efficiently removes methylene blue and Congo red dyes Mohamed Shaban 1 • Mostafa R. Abukhadra 1,2 • M. G. Shahien 2 • Suzan S. Ibrahim 3 Received: 14 April 2017 / Accepted: 26 July 2017 Ó Springer International Publishing AG 2017 Abstract Synthetic dyes are common water contaminants that impair water quality and cause diseases such as der- matitis, cancer and dysfunction of kidneys. There is therefore a need for adsorbent materials to remove dyes from water. Here a bentonite/zeolite-NaP composite was synthesized by alkaline treatment of bentonite at 150 °C for 4 h. The composite exhibits nearly cubic zeolite-NaP crystals dispersed throughout bentonite aggregates. This composite has 512 m 2 /g surface area, 387 meq/100 g cation exchange capacity and 5.4 nm average pore diam- eter. The composite shows high removal efficiency for methylene blue, of 94%, and Congo red, of 93%, after 720 min at an initial concentration of 5 mg/l. Keywords Bentonite Á Zeolite-NaP Á Dye removal Á Congo red Á Methylene blue Introduction Bentonite clays exhibit unique properties of high adsorp- tion capacity, high cation exchange capacity, high porosity and high surface area. Thus, it is commonly used in water decontamination applications (Kaya and O ¨ ren 2005). Bentonite is composed of smectite minerals in addition to smaller amounts of other clay or non-clay minerals (Rauf and Tahir 2000). Bentonite is modified by several methods to enhance the adsorption capacity, including acid activa- tion, thermal activation and formation of composites (Steudel et al. 2009). Zeolite minerals are nanoporous aluminosilicates and exhibit high ion exchange, sorption, surface area and chemical stability properties (Bohra et al. 2013). Therefore, they are widely used in water treatment applications. Synthetic zeolite was preferred for its high purity and uniform pore size distribution. Zeolite-NaP is one of the common synthetic zeolites, with pore diameter ranging from 0.26 to 0.49 nm (Albert and Cheetham 2000). Composites are materials composed of a minimum two components. They show enhanced physical or chemical properties compared to the individual components (Jay- mand 2014). To the best of our knowledge, the synthesis of a composite from bentonite and zeolite-NaP has not been investigated yet. Thus, the aim of this paper is to synthe- size, for the first time, a bentonite/zeolite-NaP composite and evaluate its adsorption behavior for basic and acidic dyes based on kinetic and equilibrium studies. Experimental Materials Natural bentonite was obtained from bentonite quarry in Egypt with chemical composition of 54.82% SiO 2 , 17.56% Al 2 O 3 , 9.5 Fe 2 O 3 , 2.6% Na 2 O, 2.5% MgO, 2.4 CaO and 1.45% TiO 2 . Synthetic zeolite-NaP was obtained by ‘A and O’ Company. NaOH (97%), methylene blue and Congo red dyes were obtained from Sigma-Aldrich Company, Egypt. & Mostafa R. Abukhadra Abukhadra89@Science.bsu.edu.eg 1 Nanophotonics and Applications Lab, Physics Department, Faculty of Science, Beni-Suef University, Beni Suef 62514, Egypt 2 Geology Department, Faculty of Science, Beni-Suef University, Beni Suef, Egypt 3 Central Metallurgical Research and Development Institute, Helwan, Cairo 11421, Egypt 123 Environ Chem Lett DOI 10.1007/s10311-017-0658-7