Adsorption/desorption of cationic dye on surfactant modified mesoporous carbon coated monolith: Equilibrium, kinetic and thermodynamic studies Mohamad Rasool Malekbala a , Moonis Ali Khan b , Soraya Hosseini a , Luqman Chuah Abdullah a,c , Thomas S.Y. Choong a,c, * a Department of Chemical and Environmental Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia b Chemistry Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia c INTROP, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia 1. Introduction Concerning the hazardous effects of dyes on flora and fauna an increasing research has been going on worldwide to control or to minimize them. Dyes even in very low concentrations in water are undesirable [1]. Characteristically dyes are stable molecules, resistant to light, heat and biodegradation [2] making conventional (primary and secondary) treatment techniques unsuitable for water decontamination [3]. Methylene blue (MB), a cationic dye, is usually used as a colouring agent in paper and pulp and textile industries. Although, MB is not regarded as a highly toxic dye, but still MB can have various harmful effects on human beings and animals. The treatment techniques for removing dyes include coagula- tion and flocculation [4], oxidation or ozonation [5,6], membrane separation [7], biosorption [8] and adsorption [9]. Adsorption has an upper hand over the aforementioned processes. Low initial cost, ease of operation, simplicity of the design and flexibility are some of the merits of adsorption process. Currently, carbonaceous materials such as activated carbon are the most widely used adsorbents. However, combustion at high temperature, pore blockage and hygroscopicity [10] are some of the demerits of carbonaceous adsorbents restricting their practical applicability for dyes removal. In addition, most of the carbonaceous materials are micropo- rous highly efficient to remove low molecular weight compounds [11–13]. The dyes and pigments molecular dimensions are close to upper limit of micropore size. For efficient removal of large molecules like dyes and pigments, adsorbents should have a well- developed mesopore structure (pore size of 2–50 nm). Moreover, powder carbonaceous adsorbents cannot be easily regenerated, and can escape through filters, causing handling problems. Therefore, an improved support is required to overcome the problems related to clogging, dispersion of particles and high pressure drop. At the same time they have low mechanical strength that limits their application in certain areas. Studies showed use of carbonaceous materials for dyes removal from aqueous phase [14,15]. However, in some cases the adsorption capacity of these adsorbents due to their low mesopore volume was not high. Journal of Industrial and Engineering Chemistry 21 (2015) 369–377 ARTICLE INFO Article history: Received 27 August 2013 Accepted 25 February 2014 Available online 2 March 2014 Keywords: Mesoporous carbon coated monolith Surfactant (F-127) Methylene blue Desorption Regeneration ABSTRACT Surfactant modified carbon coated monolith was used as an adsorbent for methylene blue (MB) adsorption. Effects of pH, salt, contact time, initial dye concentrations and temperature on dye adsorption were studied. Higher solution pH favoured MB adsorption. Furthermore, kinetics study showed that the adsorption could be better represented by the pseudo-second-order model. Linear and non-linear isotherm studies revealed better fitting of Langmuir model to adsorption data with maximum monolayer adsorption capacity 388 mg/g. The adsorption was found to be spontaneous and endothermic. Desorption studies indicate that 0.1 N HCl exhibits higher elution efficiency (82.1%) with appreciable quantitative MB recovery. ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. * Corresponding author at: Department of Chemical and Environmental Engineering, Universiti Putra Malaysia, 43400 UPM, Seri Kembangan, Selangor, Malaysia. Tel.: +60 3 89466293; fax: +60 3 86567120. E-mail addresses: tsyc2@yahoo.co.uk, csthomas@upm.edu.my (Thomas S.Y. Choong). Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry journal homepage: www.elsevier.com/locate/jiec http://dx.doi.org/10.1016/j.jiec.2014.02.047 1226-086X/ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.