Optimization of Acid Blue 25 removal from aqueous solutions by raw, esterified and protonated Jania adhaerens biomass M. Kousha a , E. Daneshvar a , A.R. Esmaeli a , M. Jokar b , A.R. Khataee c, * a Department of Fisheries, Faculty of Natural Resources, Isfahan University of Technology, Isfahan, Iran b Department of Environmental Science, Faculty of Natural Resources, Isfahan University of Technology, Isfahan, Iran c Department of Applied Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz, Iran article info Article history: Received 25 December 2011 Received in revised form 26 January 2012 Accepted 26 January 2012 Available online 18 February 2012 Keywords: Biosorption Red algae Experimental design Box-Behnken Textile dye abstract Box-Behnken design, which is well suited for fitting a quadratic surface and usually works well for the process optimization, was employed to optimize the removal of Acid Blue 25 (AB25) using untreated, methanol and HCl pretreated red alga, Jania adhaerens. Biomass was pretreated using hydrochloric acid 0.1 M with pure anhydrous methanol for esterification reaction and hydrochloric acid 1 M for proton- ation reaction. The effects of independent parameters such as biomass amount (0.2e1.4 g L 1 ), initial dye concentration (20e100 mg L 1 ) and initial pH of solution (2e6) on the AB25 biosorption were investi- gated through Box-Behnken design. The values of square of correlation coefficient (R 2 ) were 0.9946, 0.9908 and 0.9903 for untreated, methanol and HCl pretreated J. adhaerens biomass, respectively. The results showed that the maximum dye removal efficiency for untreated, methanol and HCl pretreated J. adhaerens biomass was 51.17%, 59.49%, and 85.80%, respectively. These findings revealed that pre- treating biomass by HCl effectively increased AB25 removal from aqueous solution. The present work suggests that J. adhaerens biomass is a suitable biomaterial for dye removal from aqueous solutions. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The textile industries, dye manufacturing industries, paper and pulp mills, tanneries, electroplating factories and food companies are the major sources of dyes that released into the environment through wastewater streams. Removal of dyes from the industrial effluents is a major environmental problem because most of these dyes are toxic and potentially carcinogenic in nature (Pandey et al., 2007; Khataee et al., 2009a, 2009b). The conventional techniques of wastewater treatment usually suffer from some disadvantages, including complicated procedures, formation of by-products, expensive and energy-intensive, limited versatility and less adaptability to a wide range of dye wastewaters (Kaushik and Malik, 2009). Among the numerous techniques of dye removal, adsorption process is an effective alternative treatment for dye removal from wastewater, especially if the adsorbent is cheap and readily available. Adsorption is an interaction of solute molecules with the active surface of the biomass, fixing them in the free sites owing to the action of physical processes (physisorption) and chemical bonds (chemisorption) (Amini and Younesi, 2009). Various adsorbents have been used in adsorption processes including fly ash (Kao et al., 2000; Wang and Wu, 2006), bottom ash (Meshko et al., 2001; Gupta et al., 2005; Pengthamkeerati et al., 2008), zeolite (Meshko et al., 2001), rice hull (Ponnusami et al., 2007), peanut hull (Gong et al., 2005a) and orange peel (Sivaraj et al., 2001). Among biosorbent materials, algae are both economic and eco- friendly as they are abundantly available, have regeneration, metal recovery potentiality, a less volume of chemical and/or biological sludge to be disposed of, high efficiency in dilute effluents and high surface area to volume ratio (Pengthamkeerati et al., 2008; Kousha et al., 2012). Generally, the biosorption rates of algal biomass as sorbents vary depend on the pH value, biomass dose and pollutant concentration (Fereidouni et al., 2009). The marine red alga, J. adhaerens, is one of the ubiquitous macroalga that belongs to genus of Jania sp. and family of Cor- allinaceae. Species of J. adhaerens inhabit a wide range of marine environments in the Pacific, Caribbean, and Gulf of Mexico coasts of North and Central America. This red alga requires attachment to large solid particles and their colony has been observed in the rocky intertidal area (Enriquez et al., 2009). Anthraquinonic dyes, such as Acid Blue 25, represent the second most important class of commercial dyes after azo-compounds. Anthraquinonic dyes are mainly used for dying wool, polyamide * Corresponding author. Tel.: þ98 411 3393165; fax: þ98 411 3340191. E-mail addresses: a_khataee@tabrizu.ac.ir, ar_khataee@yahoo.com (A.R. Khataee). Contents lists available at SciVerse ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod 0964-8305/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.ibiod.2012.01.007 International Biodeterioration & Biodegradation 69 (2012) 97e105