Adsorptive removal of ﬂuoride from water samples using Zr–Mn composite material Vaishali Tomar a , Surendra Prasad b, ⁎, Dinesh Kumar a, ⁎⁎ a Department of Chemistry, Banasthali Vidyapith, Banasthali 304022, Rajasthan, India b School of Biological and Chemical Sciences, Faculty of Science, Technology and Environment, The University of the South Paciﬁc, Private Mail Bag, Suva, Fiji abstract article info Article history: Received 7 April 2013 Accepted 17 April 2013 Available online 24 April 2013 Keywords: Fluoride Deﬂuoridation of water Fluoride removal Fluoride adsorption Fluoride removal efﬁciency Adsorption capacity The toxicity of ﬂuoride to mankind is very high. Thus there has always been need to treat ﬂuoride contaminated water samples for its removal to make it safe for human consumption. A novel and efﬁcient analytical method for the removal of ﬂuoride using Zr–Mn composite material has been developed for water samples. The adsorption was conﬁrmed by the use of various techniques like X-ray diffraction (XRD), Brunauer, Emmett and Teller (BET) and FTIR. The key parameters that inﬂuence analyte i.e. ﬂuoride removal were investigated and optimized. Under the optimized conditions of the adsorbent dose 1.2 g/50 mL, pH 7, temp 29 °C and the contact time 145 min, an excellent ﬂuoride removal up to 90% was achieved. The proposed material has successfully been applied to the removal of ﬂuoride in different aqueous solutions having a broad concentration range of ﬂuoride. The effective- ness of the sorption process on the adsorbent (Zr–Mn composite material) was veriﬁed by testing it on natural waters loaded with the proposed ﬂuoride. The reproducibility of the method was validated by removing ﬂuoride in various water samples by the proposed method in a different laboratory under the same condition. The simplic- ity of the proposed ﬂuoride removal material, very high removal efﬁciency, short time and the use of safe chemicals demonstrate the high potential of the proposed method for routine ﬂuoride removal from water samples. The pro- cess of adsorption by Zr–Mn composite material followed Freundlich as well as Langmuir isotherms but is favor- able to Freundlich isotherm that provides best ﬁt to the experimental data. The results obtained showed that adsorption on the Zr–Mn composite material could be an effective method for the removal of ﬂuoride. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Fluorine is quite a common element that does not naturally occur in elemental form because of its high reactivity. Fluoride is a naturally occurring compound derived from ﬂuorine which is the 13th most abundant element in the earth's crust [1,2]. It exists in the form of ﬂuorides in various minerals such as sellaite (MgF 2 ), ﬂuorspar (CaF 2 ), cryolite (Na 3 AlF 6 ) and ﬂuorapatite (Ca 5 (PO 4 ) 3 F). Thus ﬂuorides are also found in rocks, soil, plants, animals, humans and fresh as well as ocean water [2,3]. Therefore ﬂuoride occurs naturally in public water systems as a result of runoff from weathering of ﬂuoride-containing rocks and soils and leaching from soil into ground water [2–5]. In addi- tion to water, ﬂuoride is present naturally in almost all foods and bever- ages but levels vary widely. However, ﬂuoride has both beneﬁcial and harmful effects on human health depending on its level. Among the beneﬁcial effects of ﬂuoride in the human body, strengthening of bones and prevention from tooth decay are signiﬁcant [5]. Compared to its beneﬁcial effect ﬂuoride is more detrimental. Thus ﬂuoride is a toxic chemical and it is a risk factor for thyroid hormone production in children when the exposure to ﬂuoride occurs during intrauterine growth period [6]. A report during 2008 in Scientiﬁc American on ‘second thoughts about ﬂuoride’ was a warning to all concerned as it revealed the risk of ﬂuoride causing disorders affecting the teeth, bone, brain and thyroid gland [6,7]. It has also been reported that thyroxine and triiodothyronine in serum decreased with increasing urinary ﬂuo- ride in cattle. Cattle affected with ﬂuorosis developed hypothyroidism and anemia [6]. In addition, it has been conﬁrmed that there is signiﬁcant positive relationship between ﬂuoride intake by water and the preva- lence of dental ﬂuorosis [2,8–11]. For the general population the intake of ﬂuoride is mainly from drinking water and to a much lesser extent from foodstuffs i.e. drinking water is the major source of daily intake of ﬂuoride [2,12,13]. Water is an essential natural resource for sustaining life and envi- ronment that is thought to be available in abundance as a free gift of nature. However, over the past few decades, the ever-increasing pop- ulation, urbanization, industrialization and unskilled utilization of water resources have led to the degradation of water quality, causing its reduction in per capita availability in various developing countries [13]. Thus there is a substantial shortfall in the availability of potable water in less developed or developing countries, primarily due to water contamination and pollution [14–16]. It has also been reported that about 80% of the diseases in the world are due to poor quality of drinking water, and the ﬂuoride contamination in drinking water is responsible for 65% of endemic ﬂuorosis in the world which affects the teeth, bone and soft tissues [14,17,18]. The beneﬁcial or detrimental Microchemical Journal 111 (2013) 116–124 ⁎ Corresponding author. Tel.: +679 3232416; fax: +679 2321512. ⁎⁎ Corresponding author. Tel.: +91 9928108023; fax: +91 1438 228365. E-mail addresses: prasad_su@usp.ac.fj (S. Prasad), dschoudhary2002@yahoo.com (D. Kumar). 0026-265X/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.microc.2013.04.007 Contents lists available at SciVerse ScienceDirect Microchemical Journal journal homepage: www.elsevier.com/locate/microc