Print this page Email this page
Users Online: 989
Home About us Editorial board Search Browse articles Submit article Instructions Subscribe Contacts Login 

Previous article Browse articles Next article 
ORIGINAL ARTICLE
Int J Env Health Eng 2015,  4:28

Performance evaluation of Fenton process removing fluoride from aqueous solution


1 Department of Environmental Health Engineering, Student Research Center, School of Health, Isfahan University of Medical Sciences (IUMS), Isfahan, Iran
2 Environment Research Center, Research Institute for Primordial Prevention of Non-communicable Disease, IUMS, Isfahan, Iran and Department of Environmental Health Engineering, School of Health, IUMS, Isfahan, Iran

Date of Web Publication31-Aug-2015

Correspondence Address:
Afshin Ebrahimi
Environment Research Center, Isfahan University of Medical Sciences, Hezar Jerib Ave
Iran
Login to access the Email id

Source of Support: Isfahan University of Medical Sciences,, Conflict of Interest: None


DOI: 10.4103/2277-9183.163968

Rights and Permissions
  Abstract 

Aims: This study was conducted to determine the Fenton performance on the fluoride removal efficiency from aqueous solutions.
Materials and Methods: The removal efficiency of fluoride from aqueous solutions by the Fenton was carried out by preparation of the water solutions. The studied concentrations of fluoride were in the range of 1.5-3.5 mg/L, pH 2-11, contact times 1-17 min, and the Fenton ratios in the range of 1:1-1:10. The SPADNS method was used for fluoride determinations.
Results: The optimum obtained values of the studied parameters to maximum 67% removal of the fluoride from the solutions were, the fluoride concentration 2.5 mg/L, pH = 3, Fenton ratio (H 2 O 2 :Fe) = 1:2 and the contact time of 15 min.
Conclusion: The proposed material has successfully been applied to the removal of fluoride in different aqueous solutions having a broad concentration range of fluoride. The simplicity of the proposed fluoride removal material, high removal efficiency, a short time and the use of safe chemicals demonstrate the high potential of the proposed method for routine fluoride removal from water samples. The obtained results showed that Fenton process in the removal of fluoride concentration could be an effective method for the removal of fluoride.

Keywords: Aqueous solutions, Fenton, fluoride removal


How to cite this article:
Moghadam FN, Ebrahimi A. Performance evaluation of Fenton process removing fluoride from aqueous solution. Int J Env Health Eng 2015;4:28

How to cite this URL:
Moghadam FN, Ebrahimi A. Performance evaluation of Fenton process removing fluoride from aqueous solution. Int J Env Health Eng [serial online] 2015 [cited 2019 Sep 23];4:28. Available from: http://www.ijehe.org/text.asp?2015/4/1/28/163968


  Introduction Top


Fluorine is one of the four elements that are essential for animal life; there is a considerable amount in all tissues and body fluids of humans and animals. [1] This compound is abundant in the environment and exists only in combination with other elements as fluoride compounds, which are constituents of minerals in rocks and soil. Therefore, fluoride is commonly associated with volcanic activity. [2] People living in places where water has high concentrations of fluoride ions may develop fluorosis. [3] This is one of the most frequently occurring endemic diseases and currently affecting millions of people worldwide. [4] Waters with high concentrations of fluoride are found mostly in alluvial aquifers, areas of geothermal activity, arid, and semi-arid regions. Fluoride, as a contaminant in ground/surface water, could be from either natural geological sources or industries that use fluoride-containing compounds as raw materials. Hence, it is an important task to supply water with safe fluoride levels. In Mexico, the excess of fluoride in drinking water affects 5 million people (about 6% of the population). Many efforts have been taken by various researchers to reduce the fluoride concentrations in water. [5] More than 95% of the rural and about 30-40% of the urban population in India depends on groundwater for its domestic requirements. Other studies have been observed fluoride levels in groundwater in America, [6] Africa, [7] and Asia, [8] ≥30 mg/L. In some parts of Turkey has been observed fluoride concentration in groundwater in the range of 5.1-13.7 mg/L. [9] In a study conducted by Ming et al., it was shown that a high concentration of 5 mg/L fluorine that has been observed in Changzhou, China. [10] High concentration of contaminants such as fluoride and nitrate in groundwater render it unfit for drinking purpose. Fluoride contamination in groundwater has been recognized as a global problem and its concentration in drinking water at many places of the world exceeds the permissible limits. [11] Fluoride is known as both beneficial and detrimental to human health. It is well known that fluoride can effectively prevent dental caries when a relatively low level is constantly maintained in the oral cavity. On the contrary, an excessive fluoride intake leads to various diseases such as dental and skeletal fluorosis. [12],[13] Fluoride concentrations in the range of 1.5-4.0 mg/L result in dental fluorosis whereas with prolonged exposure at still higher fluoride concentrations (4-10 mg/L) dental fluorosis progresses to skeletal fluorosis. [6] Therefore, the World Health Organization as well as many countries has set 1.5 mg/L of fluoride as the upper limit in drinking water. [14],[15] Thus, fluorosis is one of the most frequently occurring diseases that develop in the population who depends on water containing high fluoride concentrations for their daily drinking. [16] 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. [17] Interference of fluoride with carbohydrates, lipid, proteins, vitamins, and mineral metabolism are also to the presence of high concentrations of fluoride in water. Various technologies such as adsorption, ion exchange, precipitation, electro-dialysis, and reverse osmosis have been employed for the removal of fluoride from water resources. [17],[18],[19],[20],[21],[22],[23] Fenton about a 100 years ago was invented for the 1 st time in 1914 by human growth hormone Fenton. However, its mechanism remained unknown until 1930s, [24] and until the 1960s, it was not experienced for destroying of any toxic compounds. Later, it was used in the oxidation-resistant organic matter in municipal wastewater and non-biodegradable material such as phenolic wastewaters. [25] The Fenton reaction causes the dissociation of the oxidant and the formation of highly reactive hydroxyl radicals that attack and destroy the organic components. [26] Some recent research has shown that the mechanism of Fenton oxidation of reactive hydroxyl radicals derived from H 2 O 2 in acidic conditions and the presence of a catalyst. [27] So, in the Fenton process are used iron and hydrogen peroxide, two chemicals that are very important in terms of cost and efficiency. The other Fenton advantage in comparison with other advanced oxidation reactions is its short reaction time. [28] Fenton technique is classified to photo-Fenton, electro-Fenton, dark-Fenton, and pseudo-Fenton process. These methods are based on different operating conditions, but their reactions are the same. Reagents used in these processes are available, inexpensive, and environmentally safe. [29]

Since to date, a study on fluoride removal from aqueous solutions by Fenton process has not been reported, this study was designed to evaluate the removal efficiency of fluoride from aqueous solution by the Fenton method. In this regard, the optimum H 2 O 2 :FeSO 4 ratio, pH, fluoride concentration, and contact times were determined.


  Materials and methods Top


Material used

In this study, all reagents and materials used had analytical grade and were purchased from Merck Co., Germany. The SPADNS reagent was provided by Hach Co., USA.

The F solutions were prepared using NaF powder with commercial purity of 98%. In this study, varying ratios of a solution of 35% (w/v) H 2 O 2 and ferrous sulfate (FeSO 4 , 7 H 2 O 2 ) were used as Fenton. Fluoride concentrations in the initial and final solutions were analyzed by SPADNS method using a direct reading spectrophotometer, Dr-5000, Hatch-LANGE, USA. The study experiments had four variables, the Fenton ratio, and fluoride concentration of solutions, pH, and the contact times.

Design of experiments was as one variable at a time. All experimental tests were repeated 2 times and the mean of results is presented. The number of analyzed samples was 72.

Experiments

Effect of initial fluoride concentrations

In this section of the study, different initial concentrations of fluorine (1.5, 2, 2.5, 3, and 3.5 mg/L) were contacted by a H 2 O 2 :FeSO 4 ratio = 1:5. Other study parameters include of pH = 6, and the contact time = 10 min.

Effect of pH

In the second stage, the optimal pH was characterized. In this regard, 10 pH values of 2-11 were tested. It should be noted that the optimum concentration of fluoride (2.5 mg/L) was obtained from previous experiments was used as the fluoride concentration of the solution. Again, the contact time 10 min and the ratio of Fenton 1:5 were used.

Effect of Fenton ratios

In the following, a series of experiments were implemented to determine of optimum Fenton ratio. In the other word, using the optimal values of the F concentration and pH obtained in the previous experiments, the optimum ratio of Fenton in the range of 1:1-10:1 was determined. In this way, the fluoride concentrations of 2.5 mg/L and pH 5 were used. The contact time of these experiments was 10 min.

Effect of contact times

In this section, the previous obtained results of the experiments, F concentration = 2.5 mg/L, pH = 5, and the H 2 O 2 :FeSO 4 = 1:5 were applied for determination of the optimum contact time. The contact times of 1-17 min were tested.


  Results Top


[Figure 1], shows the standard calibration curve of fluoride absorption in aqueous solutions. [Figure 2] illustrates the effect of initial fluoride concentrations on the fluoride removal efficiency by Fenton process. As can be shown in this figure, the fluoride percentage removal was increased with increasing fluoride concentration and the most fluoride removal was occurring in the fluoride concentration of 2.5 mg/L. [Figure 3] displays the effect of the pH changes on the fluoride removal from aqueous solutions. This figure indicates that by pH increasing of the solutions the fluoride removal efficiency was reduced. On the other hand, the maximum percentage of fluoride ions were removed at pH = 3. [Figure 4], shows the influence of the Fenton ratios on the fluoride removal. This figure demonstrates that the increase of the H 2 O 2 :FeSO 4 ratio, the decrease the fluoride removal efficiency. In addition, the highest fluoride removal efficiency was obtained in the ratio of 1:2. [Figure 5], displays the impact of contact time on the fluoride removal efficiency from aqueous solutions. As can be seen from this figure, it shows the fluoride percentage removal was increased with increasing contact time and the removal efficiency was constant after 15 min.
Figure 1: The standard calibration curve of fluoride absorption in aqueous solutions

Click here to view
Figure 2: Effect of initial fluoride concentrations, (Time = 10 min, pH = 5, H2O2:Fe = 1:5)

Click here to view
Figure 3: Influence of pH change on the fluoride removal, (time = 10 min, fluoride concentration =2.5 mg/L, H2O2:Fe = 1:5)

Click here to view
Figure 4: Impact of Fenton ratio on the fluoride removal, (time = 10 min, pH = 3, fluoride concentration =2.5 mg/L)

Click here to view
Figure 5: Contact time effect on the fluoride removal, (fluoride concentration =2.5 mg/L, pH = 3, H2O2:Fe = 1:2)

Click here to view



  Discussion Top


Effect of initial fluoride concentrations

The effect of initial fluoride ion concentration on the removal capacity of Fenton was studied by varying the initial fluoride ion concentration in the range of 1.5-3.5 mg/L at pH 5, contact time 10 min, and the H 2 O 2 :Fe ratio of 1:5 [Figure 2]. It was observed that the fluoride removal efficiency (~88%) increased as the initial fluoride ion concentration increased to a specified level (2.5 mg/L) and then leveled off. However, totally the removal trend of the fluoride from the aqueous solutions was increased by increasing of the initial fluoride concentrations. As some references, the fluoride reaction with Fe 2+ creates the Iron (II) fluoride (FeF 2 ). So, due to its k sp of 2.3 × 10−6 , probably some of the solute fluorides could be removed from solution. However, some of the more insoluble compounds also may produce during this reaction, such as CaF 2 with k sp 3 × 10−11 , and MgF 2 with k sp 5.61 × 10−11 . [30],[31]

Effect of pH

In order to understand the mechanism of fluoride removal from aqueous solutions by Fenton and the role of it, the pH of treated samples was measured. The pH of the solution is an important variable, which affect the removal of fluoride. Hence, the effects of the solution pH were studied in the range of 2-11. Results that are shown in [Figure 3] indicates that with the increasing the solution pH, the fluoride removal efficiency was decreased. The superlative fluoride removal (67%) was occurring at the initial pH 3. Therefore, it is well established that the fluoride was highly removed in acidic conditions. The highest efficiency of fluoride removal at acidic condition may be related to the presence of the highest value of dissolved iron in water at such conditions. In this situation, the highest hydroxyl radicals are formed. [32] In this study, the pH 3 was chosen as the optimal pH in the Fenton reactions. In the Fenton reaction, the hydroxyl radicals are the main oxidation agents, which are produced by the decomposition of hydrogen peroxide catalyzed by metal ions, e.g., Fe 2+ .

On the other hand, at the neutral solution pH 7, the obtained removal efficiency of the fluoride from aqueous solutions was only 45%. This lower removal efficiency may be due to the exchange interactions between F and OH groups in the solutions. It should be noted that, the lower the pH favors the generation of hydroxyl radicals. In addition, lower degradation at higher pH might be attributed to the formation of ferrous and ferric hydroxyl complexes, which will lead to a decrease in the production of hydroxyl radicals. [33]

At pH > 7, iron precipitations were visually apparent in yellow color at the bottom of the beaker. In this pH range, both Fe 2+ and Fe 3+ will precipitate as iron hydroxides. This limits the amount of iron available for Fenton reaction, which lead to decrease the amount of fluoride in the solution. [34] Xu et al., [35] observed similar results.

Effect of Fenton ratios

In this part of the study, the effect of Fenton different ratios was analyzed in the range of 1:1-1:10 of H 2 O 2 :Fe. As can be seen in the [Figure 4], in all studied ranges, except the 1:2 ratios, the trend line of the fluoride removal is decreasing by the increasing of the Fenton ratios. On the other word, under different H 2 O 2 :FeSO 4 ratios of 1:10, 1:5 and 1:2, the percentage of fluoride concentration removal at 10 min contact time was 22.74%, 44% and 62%, respectively. Fluoride removal in H 2 O 2 :Fe ratio of 1:10 and 1:9 was very low because hydroxyl radicals produced was not sufficient for fluoride removal from the aqueous solution, and the iron hydroxide precipitation was observed. So, in the 1:2 Fenton ratios, the highest removal efficiency of the fluoride was detected. Thus, this ratio was selected as the optimum value.

Effect of contact times

The effects of this parameter on the removal of fluoride were studied by varying the contact times in the range of 1-17 min under the fluoride concentration 2.5 mg/L, pH = 3, and the H 2 O 2 :FeSO 4 = 1:2. Fluoride removal efficiency as a function of contact time is shown in [Figure 5]. This Figure shows that by the increasing of the contact times, the fluoride removal efficiency was increased up to 66% at the contact time of 15 min. However, the fluoride was removed rapidly, reaching 38% removal during the first 5 min. This may be due to the diffusion of hydroxyl radical into the solution. [36] It is apparent that the fluoride removal rate was fixed and was stabilized at approximately 66%, after 15 min contact time. Argun et al., observed similar results in a heavy metal removal study. [37] Tomar et al. shown that the removal of fluoride ions increased with increase in contact time. [33]


  Conclusion Top


The proposed method has successfully been applied to the removal of fluoride in different aqueous solutions containing a wide concentration range of the fluoride. The simplicity of this method, high removal efficiency, a short time and the use of safer chemicals, demonstrate a high potential for routine fluoride removal from water samples. These values were then optimized individually double-tested and showed a maximum 67% fluoride removal. The obtained results showed that Fenton process could be an effective method for the removal of fluoride from aqueous solutions.


  Acknowledgments Top


This paper was inspired by the results of MSc Thesis no. 393266 approved by Isfahan University of Medical Sciences and the Environment Research Center at the school of health. The authors are thankful of the deputy of the research Department of Isfahan University of Medical Sciences for supporting the financial and credit requirements of this thesis. The authors also are thankful of the Isfahan University of Medical Sciences, vice chancellor for Health, Environmental Health Laboratory Staff, Eng. Manian for laboratory cooperation.

 
  References Top

1.
Brouwer ID, Dirks OB, De Bruin A, Hautvast JG. Unsuitability of World Health Organisation guidelines for fluoride concentrations in drinking water in Senegal. Lancet 1988;1:223-5.  Back to cited text no. 1
    
2.
Edmunds W, Smedley P. Groundwater geochemistry and health: An overview. Vol. 113. Geological Society, London: Special Publications; 1996. p. 91-105.  Back to cited text no. 2
    
3.
Zevenbergen C, van Reeuwijk LP, Frapporti G, Louws RJ, Schuiling RD. A simple method for defluoridation of drinking water at village level by adsorption on Ando soil in Kenya. Sci Total Environ 1996;188:225-32.  Back to cited text no. 3
    
4.
Ruixia L, Jinlong G, Hongxiao T. Adsorption of fluoride, phosphate, and arsenate ions on a new type of ion exchange fiber. J Colloid Interface Sci 2002;248:268-74.  Back to cited text no. 4
    
5.
Zeni M, Riveros R, Melo K, Primieri R, Lorenzini S. Study on fluoride reduction in artesian well - Water from electrodialysis process. Desalination 2005;185:241-4.  Back to cited text no. 5
    
6.
Mohapatra M, Anand S, Mishra BK, Giles DE, Singh P. Review of fluoride removal from drinking water. J Environ Manage 2009;91:67-77.  Back to cited text no. 6
    
7.
Apambire WB, Michel F. Geochemistry, genesis, and health implications of floriferous ground waters in the upper regions of Ghana. Environ Geol 1997;33:13-24.  Back to cited text no. 7
    
8.
Azbar N, Trkman A. Defluoridation in drinking waters. Water Sci Technol 2000;42:403-7.  Back to cited text no. 8
    
9.
Oruc N. Occurrence and problems of high fluoride waters in Turkey: An overview. Environ Geochem Health 2008;30:315-23.  Back to cited text no. 9
    
10.
Ming L, Yi SR, Hua ZJ, Yang B, Lei W, Ping L, Fuwa KC. Elimination of excess fluoride in potable water with coacervation by electrolysis using an aluminum anode. Fluoride 1987;20:54-63.  Back to cited text no. 10
    
11.
Swain S, Patnaik T, Patnaik P, Jha U, Dey R. Development of new alginate entrapped Fe (III) - Zr (IV) binary mixed oxide for removal of fluoride from water bodies. Chem Eng J 2013;215:763-71.  Back to cited text no. 11
    
12.
Chinoy N, Memon M. Beneficial effects of some vitamins and calcium on fluoride and aluminium toxicity on gastrocnemius muscle and liver of male mice. Fluoride 2001;34:21-33.  Back to cited text no. 12
    
13.
Harrison PT. Fluoride in water: A UK perspective. J Fluor Chem 2005;126:1448-56.  Back to cited text no. 13
    
14.
Fawell JK, Bailey K. Fluoride in Drinking-Water. IWA publishing, Alliance House, 12 Caxton Street, London SW1H0QS, UK.: World Health Organization; 2006.  Back to cited text no. 14
    
15.
Tomar V, Prasad S, Kumar D. Adsorptive removal of fluoride from aqueous media using Citrus limonum (lemon) leaf. Microchem J 2014;112:97-103.  Back to cited text no. 15
    
16.
Wang H, Chen J, Cai Y, Ji J, Liu L, Teng HH. Defluoridation of drinking water by Mg/Al hydrotalcite-like compounds and their calcined products. Appl Clay Sci 2007;35:59-66.  Back to cited text no. 16
    
17.
Susheela A, Bhatnagar M, Vig K. Excess fluoride ingestion and thyroid hormone derangements in children living in Delhi, India. Fluoride 2005;38:98-108.  Back to cited text no. 17
    
18.
Biswas K, Gupta K, Goswami A, Ghosh UC. Fluoride removal efficiency from aqueous solution by synthetic iron (III)-aluminum (III)-chromium (III) ternary mixed oxide. Desalination 2010;255:44-51.  Back to cited text no. 18
    
19.
Kagne S, Jagtap S, Dhawade P, Kamble SP, Devotta S, Rayalu SS. Hydrated cement: A promising adsorbent for the removal of fluoride from aqueous solution. J Hazard Mater 2008;154:88-95.  Back to cited text no. 19
    
20.
Leyva-Ramos R, Rivera-Utrilla J, Medellin-Castillo N, Sanchez-Polo M. Kinetic modeling of fluoride adsorption from aqueous solution onto bone char. Chem Eng J 2010;158:458-67.  Back to cited text no. 20
    
21.
Sujana M, Soma G, Vasumathi N, Anand S. Studies on fluoride adsorption capacities of amorphous Fe/Al mixed hydroxides from aqueous solutions. J Fluor Chem 2009;130:749-54.  Back to cited text no. 21
    
22.
Viswanathan N, Meenakshi S. Selective fluoride adsorption by a hydrotalcite/chitosan composite. Appl Clay Sci 2010;48:607-11.  Back to cited text no. 22
    
23.
Wu X, Zhang Y, Dou X, Yang M. Fluoride removal performance of a novel Fe-Al-Ce trimetal oxide adsorbent. Chemosphere 2007;69:1758-64.  Back to cited text no. 23
    
24.
Lopez A, Pagano M, Volpe A, Di Pinto AC. Fenton's pre-treatment of mature landfill leachate. Chemosphere 2004;54:1005-10.  Back to cited text no. 24
    
25.
Tang WZ, Tassos S. Oxidation kinetics and mechanisms of trihalomethanes by Fenton's reagent. Water Res 1997;31:1117-25.  Back to cited text no. 25
    
26.
Neyens E, Baeyens J. A review of classic Fenton's peroxidation as an advanced oxidation technique. J Hazard Mater 2003;98:33-50.  Back to cited text no. 26
    
27.
de Morais JL, Zamora PP. Use of advanced oxidation processes to improve the biodegradability of mature landfill leachates. J Hazard Mater 2005;123:181-6.  Back to cited text no. 27
    
28.
Zhang H, Choi HJ, Huang CP. Optimization of Fenton process for the treatment of landfill leachate. J Hazard Mater 2005;125:166-74.  Back to cited text no. 28
    
29.
Pignatello JJ, Oliveros E, MacKay A. Advanced oxidation processes for organic contaminant destruction based on the Fenton reaction and related chemistry. Crit Rev Environ Sci Technol 2006;36:1-84.  Back to cited text no. 29
    
30.
Available from: http://www.solubilityofthings.com/water/ions_solubility/ksp_chart.php. [Last cited on 2014 Sep 24].  Back to cited text no. 30
    
31.
Sawyer CN, McCarty PL, Parkin GF. Chemistry for Environmental Engineering and Science. 5 th Edi., McGraw-Hill Co., 1221 Ave., of the Americas, New York, NY 10020; 2003: 55-6.  Back to cited text no. 31
    
32.
Poinern GE, Ghosh MK, Ng YJ, Issa TB, Anand S, Singh P. Defluoridation behavior of nanostructured hydroxyapatite synthesized through an ultrasonic and microwave combined technique. J Hazard Mater 2011;185:29-37.  Back to cited text no. 32
    
33.
Tomar V, Prasad S, Kumar D. Adsorptive removal of fluoride from water samples using Zr-Mn composite material. Microchem J 2013;111:116-24.  Back to cited text no. 33
    
34.
Lv L, He J, Wei M, Evans DG, Zhou Z. Treatment of high fluoride concentration water by MgAl-CO3 layered double hydroxides: Kinetic and equilibrium studies. Water Res 2007;41:1534-42.  Back to cited text no. 34
    
35.
Xu M, Wang Q, Hao Y. Removal of organic carbon from wastepaper pulp effluent by lab-scale solar photo-Fenton process. J Hazard Mater 2007;148:103-9.  Back to cited text no. 35
    
36.
Rafique A, Awan MA, Wasti A, Qazi IA, Arshad M. Removal of fluoride from drinking water using modified immobilized activated alumina. J Chem 2012; 2013: 1-7.  Back to cited text no. 36
    
37.
Argun ME, Dursun S, Karatas M, Gürü M. Activation of pine cone using Fenton oxidation for Cd(II) and Pb(II) removal. Bioresour Technol 2008;99:8691-8.  Back to cited text no. 37
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]



 

Top
Previous article  Next article
 
  Search
 
Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

 
  In this article
Abstract
Introduction
Materials and me...
Results
Discussion
Conclusion
Acknowledgments
References
Article Figures

 Article Access Statistics
    Viewed1509    
    Printed58    
    Emailed0    
    PDF Downloaded263    
    Comments [Add]    

Recommend this journal