Electrocoagulaciom

Desalination 275 (2011) 102–106

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Desalination
j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / d e s a l

Analysis and the understanding of fluoride removal mechanisms by an electrocoagulation/flotation (ECF) process
Mohammad M. Emamjomeh a,⁎, Muttucumaru Sivakumar b, Ali Safari Varyani c
a

Research Center forCommunity Development and Health promotion, Qazvin university of Medical Sciences, Qazvin, Iran Sustainable Water and Energy Research Group, School of Civil, Mining and Environmental Engineering, Faculty of Engineering, University of Wollongong, Wollongong, NSW 2522, Australia c Occupational Health Group, Faculty of Health, Qazvin university of Medical Sciences, Qazvin, Iran
b

a r t i c l e

i n fo

a b s t r a c t
Electrocoagulation is a method of applying direct current to sacrificial electrodes that are submerged in an aqueous solution. Dissolving aluminum (Al3+) is predominant in the acidic condition and aluminum hydroxide has tendency soluble. The defluoridation process was found to be efficient for a pH ranging from 6 to 8. The fluoride removal mechanisms are investigated based onthe solution speciation (Al and Al–F complexes) and dried sludge characteristics in the electrocoagulator. The XRD analysis of the composition of the dried sludge shows the formation of Al(OH)3 − xFx and provides confirmation for the main mechanism for fluoride removal. The mechanism of the fluoride removal was confirmed to be not only the competitive adsorption between OH– and F− but also the formationof solid cryolite in pH range of 5–8. © 2011 Elsevier B.V. All rights reserved.

Article history: Received 6 December 2010 Received in revised form 12 February 2011 Accepted 14 February 2011 Available online 8 March 2011 Keywords: Electrocoagulation/flotation (ECF) process Fluoride removal mechanism Analysis Sludge characteristics

1. Introduction Inorganic constituents, which may be presentedin natural waters or in contaminated source waters, are found to become a major public health problem in drinking water. The presence of fluoride, as an inorganic ion, is serious more than limits in drinking water and it is a public health problem. The fluoride removal in drinking water and in wastewater has been the subject of many publications and studies that have progressively developed theaspects of toxicity on man and on the environment. When the fluoride concentration is increased to more than 4 mg L−1 in drinking water, fluorosis deformity at hips, knees and other joints are seen in skeletal fluorosis [1]. However, long-term use of low fluoride concentration (less than 0.5 mg L−1) is the cause of dental caries [2]. Because of the public health significance of high fluorides consumptionin drinking water, defluoridation is important. The maximum acceptable concentration of fluoride in water is 1.5 mg L−1 [3]. Fluoride pollution occurs through two different sources including natural and anthrogenic sources. In groundwater sources, the natural concentration of fluoride depends on the geological, chemical and physical characteristics of the aquifer, as concentrations of up to 38.5 mgL−1 have been reported in India. Some of the water supplies can be polluted by discharging of industrial wastewater without any
⁎ Corresponding author at: Environmental Health Engineering Dep, Faculty of Health, Qazvin university of Medical Sciences, Bahonar Street, Qazvin, Iran. Tel.: +98 281 3344504; fax: +98 281 3368778. E-mail address: m_emamjomeh@yahoo.com (M.M. Emamjomeh). 0011-9164/$ – seefront matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2011.02.032

fluoride treatment, including glass manufacturing industries [4] and semiconductor industries [5] in the natural environment. Several methods were globally studied for defluoridation of water, such as: adsorption [6–8], chemical precipitation [9–15], electrodialysis [13], and electrochemical methods [16,17]....