ARTICLE IN PRESS JID: JTICE [m5G;December 23, 2016;11:51] Journal of the Taiwan Institute of Chemical Engineers 000 (2016) 1–13 Contents lists available at ScienceDirect Journal of the Taiwan Institute of Chemical Engineers journal homepage: www.elsevier.com/locate/jtice Remediation of waste water by Co–Fe layered double hydroxide and its catalytic activity S.A. Abdel Moaty a,∗ , A.A. Farghali b , M. Moussa a,c , Rehab Khaled d a Materials Science Lab, Chemistry Department, Faculty of Science, Beni-Suef University, Beni Suef, Egypt b Materials Science and Nanotechnology Department, Faculty of Postgraduate Studies for Advanced Sciences, Beni-Suef University, Egypt c Future Industries Institute and School of Engineering, University of South Australia, Mawson Lakes, SA 5095, Australia d Department of Chemistry, Faculty of Science, Beni-Suef University, Beni-Suef, Egypt a r t i c l e i n f o Article history: Received 11 June 2016 Revised 20 November 2016 Accepted 1 December 2016 Available online xxx Keywords: Cobalt–iron LDH MWCNTs Adsorption Cadmium ions Wastewater a b s t r a c t Layered double hydroxide (LDH) nanoparticles have tremendous anion-intercalating property. Co–Fe LDH has been synthesized using the ball milling method. Characterization of Co–Fe LDH was done by XRD, SEM, TEM and FT-IR. The prepared LDH was used, for the first time, as a catalyst for multi-walled carbon nanotubes (MWCNTs) via chemical vapor deposition (CVD) of acetylene at different temperatures (400– 700 °C). Also, the ability of Co–Fe LDH as an adsorbent was investigated for the removal of Cd 2+ ions from aqueous solutions. Various physicoechemical parameters such as pH, initial metal ion concentration, and time were studied. To get the adsorption isotherms, the concentrations of the metal ions ranging from 6 to 18 mg/l were used. The adsorption process follows pseudo-second-order reaction kinetics, as well as Langmuir adsorption isotherms. Interestingly, Co–Fe LDH demonstrated 95% Cd 2+ removal at pH 9 and 6 h which could be applied in wastewater treatment characterized by a high efficiency and low cost. © 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. 1. Introduction Layered materials have been extensively studied in recent years due to the wide range of properties that could be tailored by inter- calation and functionalization (surface chemical modification) re- actions, allowing them to be used in different fields of science and technology. Therefore, the preparation of the layered materials to investigate their properties and applications has been the focus of our research group [1]. Layered double hydroxide (LDH) is a lay- ered inorganic compound that is composed of an ionic lamellar solid that contains infinite layers of brucite-type, positively charged and exchangeable hydrate gallery anions. The ability of LDHs to in- tercalate anions makes them useful as catalysts, tailor made ad- sorbents or precursor materials for oxides. The general formula of LDH is [M II 1−x M III x (OH)] x+ .[(A n− x n ).mH 2 O] x− , where M II and M III are the divalent and trivalent cations, respectively, and A n− is the in- terlayer anion of charge n that leads to the electro-neutrality of the LDH. The coefficient x is equal to the molar ratio [M III /(M II +M III )], and m is the number of water molecules located in the interlayer region with the anions [2,3]. ∗ Corresponding author. E-mail addresses: samah.mohamed@science.bsu.edu.eg, dr.samahchemy2010@yahoo.com (S.A.A. Moaty). Layered double hydroxides (LDHs) are the antitypes of clay minerals. Clay minerals found increasing interest as adsorbents by virtue of their properties, which make them attractive mate- rials for adsorbing heavy metal ions. Adsorption reactions at solid– water interfaces decrease solute mobility and often control the fate, bioavailability, and transport of heavy metal ions such as Zn 2+ ,Cu 2+ ,Pb 2+ and Ni 2+ in the environment [4,5] The adsorption mechanisms of metal ions on the surfaces of clay minerals and others are significant for understanding their fate in the environ- ment. LDHs could adsorb metal cations from aqueous solution in spite of positive layer charge. A major reaction could be surface- induced precipitation that occurs due to localized high pH values and the released carbonate ions available to metal cations. Positive layer charge attracts hydroxide ions around the surfaces of LDH crystals in aqueous solution to induce formation of metal hydrox- ides. Meanwhile, charge-compensating carbonate ion attached on the surface and edge could also contact with metal cations to form insoluble metal carbonates. There is also another possibility to ad- sorb metal cations via diodachy, as suggested by Komarneni et al. [6]. These imply that LDHs could be utilized as an adsorbent for heavy metal cations. However, there are only a few studies on the interaction between LDH and heavy metal cations in solution. The layered structure of layered double hydroxides is destroyed and transformed into mixed oxides with large surface area and good dispersion of metal cations after a controlled thermal treat- ment. This makes them capable of acting as an excellent precursor http://dx.doi.org/10.1016/j.jtice.2016.12.001 1876-1070/© 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Please cite this article as: S.A.A. Moaty et al., Remediation of waste water by Co–Fe layered double hydroxide and its catalytic activity, Journal of the Taiwan Institute of Chemical Engineers (2016), http://dx.doi.org/10.1016/j.jtice.2016.12.001