Applied Surface Science 258 (2012) 10002–10011 Contents lists available at SciVerse ScienceDirect Applied Surface Science jou rn al h om epa g e: www.elsevier.com/locate/apsusc Synthesis of high-surface-area -Al 2 O 3 from aluminum scrap and its use for the adsorption of metals: Pb(II), Cd(II) and Zn(II) Yvan J.O. Asencios a,∗ , María R. Sun-Kou b a Instituto de Química de São Carlos, Universidade de São Paulo, Av. Trabalhador Sãocarlense, 400, 13560-970, São Carlos, SP, Brazil b Sección Química, Departamento de Ciencias, Pontificia Universidad Católica del Perú, Av. Universitaria 1801, Lima 32, Peru a r t i c l e i n f o Article history: Received 18 January 2012 Received in revised form 18 June 2012 Accepted 18 June 2012 Available online 26 June 2012 Keywords: Gamma alumina Adsorbent Adsorption Zinc Cadmium Lead a b s t r a c t Several types of alumina were synthesized from sodium aluminate (NaAlO 2 ) by precipitation with sulfuric acid (H 2 SO 4 ) and subsequently calcination at 500 ◦ C to obtain -Al 2 O 3 . The precursor aluminate was derived from aluminum scrap. The various -Al 2 O 3 synthesized were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), adsorption–desorption of N 2 (S BET ) and scanning electron microscopy (SEM). XRD revealed that distinct phases of Al 2 O 3 were formed during thermal treatment. Moreover, it was observed that conditions of synthesis (pH, aging time and temperature) strongly affect the physicochemical properties of the alumina. A high-surface-area alumina (371 m 2 g -1 ) was synthesized under mild conditions, from inexpensive raw materials. These aluminas were tested for the adsorption of Cd(II), Zn(II) and Pb(II) from aqueous solution at toxic metal concentrations, and isotherms were determined. © 2012 Elsevier B.V. All rights reserved. 1. Introduction In recent years, the increasing extraction of metals has stimulated the economies of several south-American countries (e.g. Brazil, Peru, Chile). However, these activities release some unwanted by-products, such as Zn, Cd and Pb. These metals accumulate in the aquatic ecosystem and are hazardous at high concentrations. Thus, the removal of heavy metals from wastew- ater is a growing concern because the increasing discharges could lead to toxic water supplies [1]. Cadmium comes mainly from the wastewater of the metal plat- ing industry, cadmium–nickel batteries and mining [2]. Foods high in proteins contain zinc naturally, but soluble salts of zinc, such as ZnSO 4 , in large doses (about 10 g), have caused internal organ damage and even death [3]. Lead is hazardous in small amounts as it accumulates in brain, bones and kidney. Industrial processes, such as battery manufacturing, are also a major source of lead pol- lution [4]. According to the Agency for Toxic Substances and Disease Registry (ATSDR) of the U.S. Department of Health and Human Ser- vices, the permissible limits in drinking water are 0.04 mg L -1 for Cd, 5 mg L -1 for Zn and 0 mg L -1 for Pb [5]. ∗ Corresponding author. Tel.: +55 16 33739484. E-mail addresses: yvan@iqsc.usp.br (Y.J.O. Asencios), msun@pucp.edu.pe (M.R. Sun-Kou). The use of adsorbents to treat wastewater has become an important topic of research, since adsorption processes are very simple, compared to chemical processes such as precipitation or ion-exchange. Additionally, in response to environmental quality requirements for drinking water, recent work includes the syn- thesis of new economical adsorbents with useful properties for contaminant removal, to replace conventional high-cost adsor- bents (activated carbon, zeolites, SBA-15, etc.). Alumina is obtained from bauxite industrially by the Bayer pro- cess, in which a mixture of bayerite and gibbsite is produced by acidic precipitation of sodium aluminate with CO 2 , the final prod- uct containing impurities such as Fe 2 O 3 [6]. The bayerite is calcined at >500 ◦ C and transformed into gamma alumina, which is widely used as a catalytic support, because of its large surface area, high porosity, acidity and low toxicity. Many methods for the synthesis of alumina are reported in the literature [7–10], involving expensive raw materials and harsh syn- thetic conditions that include high temperatures and pressures. Here we report a method that involves mild conditions to synthe- size gamma alumina (-Al 2 O 3 ) and compare the morphology and crystal structure with those of commercial alumina. A great amount of aluminum scrap is produced worldwide, of which a major part is recovered by recycling [6], but an alternative way of using the aluminum scrap is to transform it directly into alumina, which finds several uses (in catalysts, in soft abrasives, in coatings and in adsorbents). The aim of this study was to synthesize alumina by acidic precipitation (with H 2 SO 4 ) of sodium aluminate. 0169-4332/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apsusc.2012.06.063