# Removal of Fluoride and Arsenate from Aqueous Solutions by Aluminum-Modified Guava Seeds  
[PERSON]  
1 Facultad de Quimico Farmacobiologia, Universidad Michoacana de San Nicolas de Hidalgo, Tzintzuntzan 173 Col. Matamoros, Morelia C.P. 58240, Michoacan, Mexico; [EMAIL_ADDRESS]  
2 Instituto de Investigaciones en Ciencias de la Tierra, Universidad Michoacana de San Nicolas de Hidalgo, Edificio U, C.U., Morelia C.P. 58060, Michoacan, Mexico; [EMAIL_ADDRESS]  
3 Facultad de Ingenierieria Quimica, Universidad Michoacana de San Nicolas de Hidalgo, C.U., Morelia C.P. 58060, Michoacan, Mexico; [PERSON]  
4 Correspondence: [EMAIL_ADDRESS]; Tel. : +52-443-314-2152  
then consumption of these waters may lead to dental fluorosis. From 3 to 6 mg/L of fluoride, skeletal fluorosis may appear, and at higher fluoride levels (>10 mg/L) crippling skeletal fluorosis can be developed [3,4]; these types of fluorosis are irreversible, and no treatment can eliminate symptoms definitively. Keeping fluoride intake within safe levels is the only way to prevent these diseases [5,6]. People in several countries around the world are facing problems of high fluoride levels in drinking water; these problems are more severe and intense depending on different factors, like the geographical and economic status of the affected communities [7]. The World Health Organization (WHO) guidelines for drinking water quality have established that, for areas with a warm climate, fluoride concentration in water should remain below 1 mg/L, while this concentration could be raised up to 1.2 mg/ for areas with a cold climate [3]. In developing countries this problem is more acute, particularly in small urban communities and rural areas [5,8]. On the other hand, arsenic content in drinking water is also a worldwide concern, and it represents a great threat to human health. Levels above 10 ug/L of arsenic, which is the maximum level recommended by the WHO, have been reported in drinking water from several countries like India, Bangladesh, Taiwan, Mongolia, Chile, Mexico, and the United States. Chronic exposure to arsenic can induce skin cancer, or it can cause damages to the kidneys, lungs, and bladder, as well as disorders of cardiovascular and neurological systems [9]. Arsenic can be found in aquatic environments in the oxidation states +III and +V, depending on the redox conditions. The As(III) species is the most toxic and it is more mobile than As(V) species [10]. Usually, arsenic in the oxidation state +V predominates in surface waters, while arsenic in the oxidation state +III is the main species found in groundwater, particularly for deep aquifers. However, arsenic in both oxidation states can be found in groundwater due to changes in redox conditions and biological activity [11]. Arsenic and fluoride coexistence has been reported in groundwater samples from aquifers in different countries, with concentrations up to 5300 ug/L and 29 mg/L for As and F\({}^{-}\), respectively [12]. It has been reported synergistic adverse effects in mouse kidney and liver at low arsenic and fluoride concentrations [12], but they are far from being completely understood. Such co-occurrence of arsenate and fluoride ions has been reported in some industrial wastewaters, like those discharged from metallurgy and electroplating industries. Consequently, removal of arsenic and fluoride from drinking water is of great importance in order to optimize costs and simplify treatment processes, especially when these two ions are present simultaneously in contaminated aquifers. [13]. Arsenic and fluoride removal from water can be achieved by different methods, including chemical treatment, electrochemical methods, membrane technologies, and ion exchange processes. However, the high costs, difficulty in operation, and the high solute concentration in water are some factors that restrict the implementation of these type of technologies [13].