Equilibrium and kinetics studies for the adsorption of Basic Red 46 on nickel oxide nanoparticles-modified diatomite in aqueous solutions Reza Khalighi Sheshdeh a, *, Mohammad Reza Khosravi Nikou a , Khashayar Badii b , Nargess Yousefi Limaee b , Gelayol Golkarnarenji c a Gas Engineering Department, Ahwaz Faculty of Petroleum, Petroleum University of Technology (PUT), P.O. Box: 63431, Ahwaz, Iran b Department of Environmental Researches, Institute for Color Science and Technology (ICST), P.O. Box: 16765-654, Tehran, Iran c Institute for Frontier Materials, Deakin University, Geelong VIC 3220, Australia 1. Introduction Synthetic dyes have increasingly been used in the textile and dyeing industries because of their ease and cost-effectiveness in synthesis as well as high stability to light, temperature, detergent and microbial attack which can lead to the discharge of highly polluted effluents [1]. More than 10,000 chemically different dyes are being manufactured, and the world dyestuff and dye intermediates production are estimated to be around 7  10 8 kg per annum [2,3]. Colour as one of the effluent characteristics affects the nature of the water, inhibits sunlight penetration into the stream and reduces the photosynthetic activity [4,5]. Moreover, some dyes are carcinogenic and mutagenic which are generally stable to biological degradation [4,6]. Hence, their removal from aqueous solution, before discharging them into the environment is extremely important [7]. Therefore, the development of efficient, low-cost and environmentally friendly technologies to reduce dye content in wastewater is extremely necessary. New economical, locally available and highly effective biosor- bents are still under development. Furthermore, many treatment systems have been proposed for the removal of synthetic dyes from aqueous solutions. Coagulation [8], flocculation [9], photo- catalytic degradation [10–12], membrane filtration [13], microbi- ological decomposition [14], electrochemical oxidation [15], fungus biosorbent [16] and adsorption [17–25] are the most commonly used methods for removing dyes from waste and effluent systems. The microbiological, photocatalytic and electro- chemical decomposition procedures are not efficient because many dyes cannot be easily decomposed [15]. Adsorption is considered to be particularly competitive, economically efficient and cost-effective process for the removal of dyes, heavy metals and other organic and inorganic hazardous impurities from aqueous solutions. Although activated carbon is the most efficient and popular adsorbent and has been used with great success, the high cost of activated carbon sometimes restricts its application with regard to dye removal [26–33]. Recently, many researchers have attempted to use alternative low-cost sorbents to replace Journal of the Taiwan Institute of Chemical Engineers xxx (2014) xxx–xxx A R T I C L E I N F O Article history: Received 7 October 2013 Received in revised form 27 January 2014 Accepted 25 February 2014 Available online xxx Keywords: Adsorption Diatomite Nickel oxide nanoparticles Isotherm Kinetics Basic Red 46 A B S T R A C T The nickel oxide nanoparticles-modified diatomite (NONMD) as a low-cost adsorbent was investigated for the removal of C.I. Basic Red 46 (BR46) from aqueous solution. Various physico-chemical parameters were studied such as solution pH, adsorbent dosage, adsorbent size, initial dye concentration, temperature, contact time and salt (NaCl, NaHCO 3 and Na 2 SO 4 ). The mean size and the surface morphology of the adsorbent were characterized by SEM, BET, FTIR, XRD, EDX and elemental analysis. The maximum percentage of BR46 dye removal from aqueous solution was 99.48% (124.35 mg/g) when 0.005 g of NONMD was applied at pH 8, temperature 25  1 8C, agitation speed of 200 rpm, initial dye concentration of 25 mg/L, and a mixing time of 60 min. Furthermore, under the same conditions, the maximum adsorption of dye on raw diatomite was 84.49% (105.61 mg/g). The experimental data showed that the adsorption of dye on raw diatomite follows the Langmuir model, but its adsorption on modified diatomite followed the BET model. The kinetics results were found to conform well to pseudo-second order kinetics model with good correlation. Thus, this study demonstrated that the NONMD could be used as a low- cost natural adsorbent for removal of BR46 from aqueous solution. ß 2014 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +98 611 5550868; fax: +98 611 5550868. E-mail address: rezakhalighi@yahoo.com (R. Khalighi Sheshdeh). G Model JTICE-859; No. of Pages 11 Please cite this article in press as: Khalighi Sheshdeh R, et al. Equilibrium and kinetics studies for the adsorption of Basic Red 46 on nickel oxide nanoparticles-modified diatomite in aqueous solutions. J Taiwan Inst Chem Eng (2014), http://dx.doi.org/10.1016/ j.jtice.2014.02.020 Contents lists available at ScienceDirect Journal of the Taiwan Institute of Chemical Engineers jou r nal h o mep age: w ww.els evier .co m/lo c ate/jtic e http://dx.doi.org/10.1016/j.jtice.2014.02.020 1876-1070/ß 2014 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.