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Water Supply Engineering
Published in P.K. Jayasree, K Balan, V Rani, Practical Civil Engineering, 2021
P.K. Jayasree, K Balan, V Rani
Fluorides in drinking water must neither be totally absent nor should exceed an optimum value of about 1 ppm. To ensure this, fluorides are added to waters found deficient in fluoride concentrations, under a process known as fluoridation. When the fluoride concentration in given water exceeds the limiting value of 1–1.5 ppm, the fluorides are removed from water under a process known as defluoridation. Fluorides may enter the human body through drinking water 96%–99% of it combines with bones, since fluorides have affinity for calcium phosphate in the bones. Excess intake of fluoride can lead to dental fluorosis, skeletal fluorosis, or nonskeletal fluorosis.
Bioremediation of Fluoride and Nitrate Contamination in Soil and Groundwater
Published in Amitava Rakshit, Manoj Parihar, Binoy Sarkar, Harikesh B. Singh, Leonardo Fernandes Fraceto, Bioremediation Science From Theory to Practice, 2021
Lal Chand Malav, Gopal Tiwari, Abhishek Jangir, Manoj Parihar
Chemical process such as precipitation, weathering, absorption and exchange of ions may influence concentrations of F– and nitrate in groundwater. Various modern methods of defluoridation and nitrate removal are already being used but these traditional methods have certain drawbacks, including high cost and energy consumption, secondary contamination after treatment and lower efficiency. In this context, bioremediation could be a cost-effective and environmentally friendly way to remove fluoride and nitrate compounds from soil and groundwater.
Carbon Nanotubes And Their Applications In Chemical Engineering Science: A Far-Reaching Review
Published in Alexander V. Vakhrushev, Vladimir I. Kodolov, A. K. Haghi, Suresh C. Ameta, Carbon Nanotubes and Nanoparticles, 2019
Loganathan et al.16 delineated with deep and cogent insight in a review defluoridation of drinking water using adsorption processes. Excessive intake of fluoride, mainly through drinking water is a serious health hazard throughout the world whether it is developed or developing nations. Today there are several methods used for defluoridation of drinking water, of which, adsorption techniques are generally considered attractive and important because of their effectiveness, convenience, and ease of operation. In this paper, the authors deeply discussed various adsorbents used for defluoridation, their relative effectiveness, mechanisms and thermodynamics of adsorption, and the varied suggestions made on the choice of adsorbents for various circumstances and immense scientific vision. The authors in this paper deeply discussed factors influencing adsorption: (1) pH, (2) coexisting anions, (3) temperature, and (4) adsorption kinetics.16 Adsorption thermodynamics, fluoride desorption, and adsorption regeneration are the other hallmarks of this paper.16
Defluoridation of synthetic and industrial wastewater by using acidic activated alumina adsorbent: characterization and optimization by response surface methodology
Published in Journal of Environmental Science and Health, Part A, 2018
Usha Kumari, Sushanta K. Behera, B. C. Meikap
Various methods like precipitation, electrocoagulation, membrane separation, ion exchange and adsorption have been attempted for defluoridation.[11–13] Among the methods mentioned, adsorption is widely accepted due to low cost, highly efficient, eco-friendly, easy handling and a wide variety of adsorbent availability.[2,14] Researchers have attempted a wide variety of adsorbents for defluoridation such as synthetic resin, [15] red mud,[16] fibrous adsorbent,[17] bone char,[18] fly ash,[19] activated carbon [20] and polymeric materials.[21,22] The drawbacks of adsorbents mentioned above are low adsorbent capacity, less selectivity, cumbersome and time-consuming synthesis process. All these drawbacks create hindrance in practical application adsorbent in the removal of fluoride.
Removal of fluoride from wastewater using HCl-treated activated alumina in a ribbed hydrocyclone separator
Published in Journal of Environmental Science and Health, Part A, 2018
Gayatree Patra, Priyam Das, S. Chakraborty, B. C. Meikap
Fluoride removal from aqueous solution have been carried out by many researchers.[7–12] The techniques used for defluoridation are adsorption,[13–17] membrane processes, precipitation, reverse osmosis, electro dialysis, nano filtration and electrocoagulation-flotation.[18] Adsorption is the most widely used technique for defluoridation. Several adsorbents such as Mg-Cr-Cl layered double hydroxide,[19] Fe-Ca-Zr hybrid metal oxide nanomaterial,[20] goethite,[21] calcium impregnated activated charcoal,[22] Al2O3-Fe3O4-expanded graphite nano-sandwich structure [23] have been employed for the removal of fluoride from aqueous solutions. Alumina and alumina based compounds like aluminum hydroxide coated rice husk ash,[24] poly aluminum chloride alum,[25] Al, Ti, and Fe hydroxides,[26] aluminum fumarate metal-organic framework,[27] aluminum containing compounds,[28–31] aluminum oxide,[32] lanthanum hydroxide supported on alumina [33] were used by many researchers for defluoridation.
Application of clay ceramics and nanotechnology in water treatment: A review
Published in Cogent Engineering, 2018
Ebenezer Annan, Benjamin Agyei-Tuffour, Yaw Delali Bensah, David Sasu Konadu, Abu Yaya, Boateng Onwona-Agyeman, Emmanuel Nyankson
Fluoride is a naturally occurring element in minerals, geochemical deposits, and natural water systems and enters food chains through either drinking water or eating plants and cereals (Pandey & Soupir, 2013). Also found to occur naturally as sellaite (MgF2), fluorspar (CaF2), cryolite (Na3AlF6) and fluorapatite [3Ca3(PO4)2Ca(F,Cl2)]. According to the WHO, the tolerance limit of fluoride content in drinking water is 1.5 mg/L (World Health Organization, 2004). Fluoride concentrations in the range of (1.5–4) mg/L result in dental fluorosis, whereas with prolonged exposure to (4–10 mg/L) progresses to skeletal fluorosis. Fluoride which is nearly insoluble in water has been found in many groundwater bodies at levels around 30 mg/L, notably in Africa, USA, and Asia (Mohapatra, Anand, Mishra, Giles, & Singh, 2009) (Maheshwari, 2006). The main methods used in defluoridation from aqueous solutions are membrane techniques and adsorption techniques (alumina-based adsorbents, clays and soils, carbon, zeolites and layered double hydroxides (Mohapatra et al., 2009). The adsorption techniques have been found to be most effective and widely used because of its low maintenance cost and even appreciable fluoride removal at low concentrations.