Adsorption studies of etherdiamine onto modified sugarcane bagasses in aqueous solution Karla Aparecida Guimarães Gusmão, Leandro Vinícius Alves Gurgel, Tânia Márcia Sacramento Melo, Cornélio de Freitas Carvalho, Laurent Frédéric Gil * Departamento de Química, Instituto de Ciências Exatas e Biológicas, Universidade Federal de Ouro Preto, Campus Universitário Morro do Cruzeiro, 35400-000 Ouro Preto, Minas Gerais, Brazil article info Article history: Received 12 February 2013 Received in revised form 13 November 2013 Accepted 20 November 2013 Available online 9 January 2014 Keywords: Adsorption Etherdiamine Flotigam 2835 Modified sugarcane bagasse Iron ore flotation abstract In this study sugarcane bagasse was modified with succinic anhydride and EDTA dianhydride to obtain SCB 2 and EB adsorbents, respectively. These adsorbents were used to remove etherdiamine, which is used for iron ore flotation from single aqueous solutions. The removal and recovery of etherdiamine is important for environmental and economic reasons due to its toxicity and high cost. The results demonstrated that adsorption of etherdiamine by SCB 2 and EB was better fitted by a pseudo-second- order kinetic model than pseudo-first-order and Elovich models. Adsorption isotherms were better fitted by the Langmuir model rather than the Freundlich, Sips, and Temkin models. The maximum adsorption capacities (Q max ) of SCB 2 and EB for etherdiamine adsorption were found to be 869.6 and 1203.5 mg/g, respectively. The calculated DG  values for adsorption of etherdiamine on SCB 2 (22.70 kJ/ mol) and EB (19.10 kJ/mol) suggested that chemisorption is the main mechanism by which etherdi- amine is removed from the aqueous solution for both adsorbents. The high Q max values showed that SCB 2 and EB are potential adsorbents for recovering the etherdiamine and treating effluents produced from iron ore flotation. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Brazil has the fifth largest reserve of iron ore in the world. With a high percentage of iron in iron ores, Brazil is among the largest producers and exporters of iron in the world (Alves, 2006). With the reduction in reserves of high-grade iron ore, concentration processes have become indispensable for mining companies that commercialize iron ore as a raw material to make steel (Filippov et al., 2010; Magriotis et al., 2010). Froth flotation is the most effective method from both the technological and economical points of view for iron ore beneficiation (Lima et al., 2005) and to upgrade the iron concentration (Filippov et al., 2010; Pearse, 2005). Although different flotation methods are available, reverse cationic flotation of quartz is by far the most widely used method to sepa- rate this major contaminant from iron ore (Araujo et al., 2005). Reverse cationic flotation of quartz is accomplished using fatty primary alkylamines partially neutralized with acetic acid, and basically consists of the selective separation of quartz particles from iron oxides (Lima et al., 2005). For this purpose, commercial organic amine salts, known as etheramines, are commonly used (Araujo et al., 2005). These compounds may have one or two amine groups and the overall chemical structure of such organic com- pounds is: [ReOe(CH 2 ) 3 eNHe(CH 2 ) 3 eNH 3 ] þ CH 3 COO  for ether- diamine and [ReOe(CH 2 ) 3 eNH 3 ] þ CH 3 COO  for etheramine (R ¼ alkyl group with carbon number >10), respectively (Araujo et al., 2010). The presence of an ether group in the etheramine chain also increases its solubility in water (Lima et al., 2005). In the flotation process, the fatty amine is added to the system and is adsorbed on the quartz surface, and both are removed from the system as an aqueous pulp. However, at the pH at which this process occurs (close to 10), both quartz (SiO 2 ) and hematite (Fe 2 O 3 ) surfaces are positively charged, and therefore they can adsorb the amine despite its preferential attraction for quartz. In order to avoid competitive iron oxide flotation, starch is used as a depressing agent (Araujo et al., 2010). Globally, iron ore processing consumes 15,000e20,000 tons of etheramine, representing approximately 85 million US dollars (Magriotis et al., 2010). Due to its toxicity to aquatic organisms, high chemical oxygen demand (COD) value, corrosive proprieties and * Corresponding author. Tel.: þ55 31 3559 1717; fax: þ55 31 3559 1707. E-mail address: laurent@iceb.ufop.br (L.F. Gil). Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman 0301-4797/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jenvman.2013.11.040 Journal of Environmental Management 133 (2014) 332e342