Journal of Environmental Sciences 20(2008) 1268–1272 Adsorption of Disperse Blue SBL dye by synthesized poorly crystalline hydroxyapatite BARKA Noureddine 1, * , QOURZAL Samir 1 , ASSABBANE Ali 1 , NOUNAH Abederrahman 2 ,A ˆ IT-ICHOU Yhya 1 1. Materials, Photocatalysis and Environment Team, Department of chemistry. Faculty of Sciences Agadir. BP: 8106 Hay Dakhla, Agadir 80006, Morocco. E-mail: barkanoureddine@yahoo.fr 2. Laboratory of Environmental Sciences. Technology High School, BP. 227, Sal´ e-M´ edina 11000, Morocco Received 6 October 2007; revised 15 January 2008; accepted 19 March 2008 Abstract The present study has been undertaken to evaluate the adsorption in batch mode of a disperse dye (Disperse Blue SBL) by poorly crystalline hydroxyapatite synthesized by coprecipitation between Ca(NO 3 ) 2 and (NH 4 ) 2 HPO 4 reagents in aqueous solution at room temperature. The adsorption experiments were carried out to investigate the factors that influence the dye uptake by the adsorbent, such as the contact time under agitation, adsorbent dosage, initial dye concentration, solution temperature, and pH. The experimental results show that the percentage of dye removal increases with increasing the amount of adsorbent, until the total discoloration. The adsorption isotherms follow the model of Langmuir with a high adsorption capacity. The adsorption was pH and temperature dependent. Key words: hydroxyapatite; Disperse Blue SBL; adsorption isotherm; enthalpy of adsorption Introduction Color is the first indicator of contamination to be rec- ognized in wastewater. Many industries, such as textile, tanning, printing, food, cosmetics, and so on, use organic compounds as dyes to color their final products. In the dyeing section of a textile industry, about 1,000 L of water are used for every 1,000 kg clothes processed (Garg et al., 2004). The presence of these species in wastewater, ever at very low quantities, is highly visible and undesirable; their presence in aquatic systems reduces light penetration, which retard photosynthetic activity and also has a tenden- cy to chelate metal ions producing microtoxicity to fish and other organisms (MacKay et al., 1980). To depollute the dyeing wastewater, a number of methods including chem- ical oxidation and reduction, chemical precipitation and flocculation, photolysis, adsorption, ion pair extraction, electrochemical treatment, and advanced oxidation have been investigated. Most conventional adsorption systems use activated carbon in spite of its higher production cost and regeneration difficulty. Consequently, a number of low cost and easily available materials are being studied for the removal of different dyes from aqueous solutions at differ- ent operating condition (Wong and Hu, 2007; Dogan and Alkan, 2003; Chu and Chen, 2002; Annadurai et al., 2002; Ghosh and Bhattacharyya, 2002; Oscar and Sengil, 2002). In our laboratory, the work is in process to evaluate the * Corresponding author. E-mail: barkanoureddine@yahoo.fr. possibility of the use of synthetic phosphates, essentially hydroxyapatite for wastewater pollution management. Calcium hydroxyapatite (HAP), Ca 10 (PO 4 ) 6 (OH) 2 , is an important inorganic material in biology and chemistry (Elliott, 1994; LeGeros, 1991; Arends et al., 1987). Their availability structure, ionic exchange property, adsorption affinity, and their characteristic to establish bonds with organic molecules of different sizes have conferred to this material to attract more attention during the last two decades. Calcium phosphates, especially apatites, are widely used for chromatographic purposes (Kawazaki, 1991; Gorbunoff, 1984) and are suitable for a number of biomedical applications, e.g., artificial bone and roofs of teeth, as well as a carrier for drug delivery (Barroug and Glimcher, 2002; Cannon and Rajpai, 1995; Aoki, 1994). In addition, this material can be a matrixes efficient of water purification. As of now, this material is much studied in the removal of rare earths and heavy metals (G´ omez del R´ ıo et al., 2004; Krestou et al., 2004; Vega et al., 2003; Misra, 1998; Middelburg and Comans, 1991), but limited studies are investigated in the removal of organic molecules (Raˆ ıs et al., 2001; Bensaoud et al., 1999). The aim of the present study was to determine the optimum conditions for the removal of a disperse dye (Disperse Blue SBL) from aqueous solution by synthesized hydroxyapatite.