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Resources and Sustainable Materials
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Fluorine compounds are widely used in industry. Large quantities of fluorspar, CaF2, are required as a flux in steel manufacture. Synthetic and natural cryolite, Na3AlF6, is used as a solvent for aluminum oxide in the electrolytic preparation of aluminum metal. Sodium fluoride is added to water to help prevent tooth decay (water fluoridation). World reserves of high-grade fluorspar are around 190 million metric tons, approximately 13% of which is in the United States. This is sufficient for several decades at projected rates of use. A significant amount of by-product fluorine is recovered from the processing of fluorapatite, Ca5(PO4)3F, used as a source of phosphorus (see the following section).
MOF-based Electrochemical Sensors for Toxic Anions
Published in Ram K. Gupta, Tahir Rasheed, Tuan Anh Nguyen, Muhammad Bilal, Metal-Organic Frameworks-Based Hybrid Materials for Environmental Sensing and Monitoring, 2022
Naseer Ahmad, Sufian Rasheed, Batool Fatima, Saadat Majeed, Abrar Mohyuddin, Muhammad Najam-ul-Haq, Dilshad Hussain
The mixing of fluorides in groundwater is a basis of severe human health issues. Fluorides are present in water with iron, beryllium, and aluminum as fluoride ions. It is due to the elimination of mineral deposits and industrial waste which contains fluoride into bodies of water. Fluorine-based inorganic compounds are employed in industry for aluminum fabrication, in glass fiber, and steel utilized as a flux, sodium hexafluorosilicate, fluorosilicic acid, and sodium fluoride NaF is applied in water fluoridation treatment. Fluorides in the human body within range are also essential for the usual mineralization of skeletons and the formation of the dental coating. A fluoride amount in drinking water is beneficial at levels up to 0.7 mg/L but is toxic above 1.5 mg/L, according to the WHO. If fluoride is present in excess in the body it may cause dental and skeletal fluorosis. Fluorosis is widely spread across 20 developed and developing countries. Some other health effects which may result from Fluorides are arthritis, brain damage, cancer, Alzheimer’s syndrome, infertility, osteoporosis, brittle bones, and thyroid disorder. A large fluoride concentration affects some other biological molecules such as carbohydrates, lipids, vitamins, proteins, and the mineral metabolism. The most common methods to eliminate fluoride from polluted water are bone char, clay, dolomite, precipitation with lime, ion exchange, reverse osmosis, nanofiltration, and electrodialysis. Monitoring their concentrations to prevent toxic effects, MOF-based electrochemical sensors are utilized [12].
Chemistry in Wastewater Treatment
Published in Sreedevi Upadhyayula, Amita Chaudhary, Advanced Materials and Technologies for Wastewater Treatment, 2021
Sonali Sengupta, Chandan Kumar Pal
Fluoride can be removed to a great extent by combining activated alumina adsorption and reverse osmosis. But in some cases, coagulation using alumina coagulant is effective and economical. The removal is highly dependent on the pH of water and the coagulant dose. The optimum pH for this operation is in the range of 6–7.5. Fluoride ions reacting with aluminum hydroxide produce complex aluminum-fluoride ions, which generate flocs. Some fluoride ions adsorb on the aluminum flocs rather than producing complex ions. In a recent study, it was observed that fluoride removal efficiency was increased with increasing alum coagulant concentration and contact time. The maximum removal rate (93.3 percent) was achieved with 300 mg/l alum concentration, 45 minute contact time, and pH value of 6 when fluoride concentration in water was 3 mg/l (24). Also, removal efficiency is decreased by increasing fluoride concentration. Experimental results reveal that aluminum sulfate coagulant shows an acceptable efficiency with easy operation.
Adsorption of fluorine ion from water by composite nonwovens
Published in The Journal of The Textile Institute, 2021
Minglei Lu, Hao Liu, Fukui Pan, Xin Ning, Jinfa Ming
Many methods have been used to remove fluoride ions from water, including reverse osmosis, electrodialysis, ion exchange, precipitation, adsorption and so on (Ahmed, 2011; Cai et al., 2018; Lahnid et al., 2008; Meenakshi & Viswanathan, 2007; Ndiaye et al., 2005; Reardon & Wang, 2000). Among them, adsorption method has become the most commonly used, because of its advantages of high efficiency and low cost (Gu et al., 2005; O’Connell et al., 2008). Low cost adsorbents have been concerned and examined for the removal of fluoride from aqueous solution (Mohammad et al., 2016). Carbon nanotubes (CNTs), owning a large specific surface area, as well as the high mechanical, chemical and thermal stabilities, are emerging as one of the most promising absorbent materials (Sarkar et al., 2018). Earlier works have reported the excellent adsorption capability of CNTs towards different contaminants such as air particles, dyes, and heavy metals (Lutiane et al., 2020). Rashid et al. reviewed different types of CNTs membranes for the removal of small air particles and the ion filtration of aqueous solution (Md. Harun-Or & Stephen, 2017). Shabaan found anionic dyes and cationic dyes were removed efficiency reaching 98.7% and 97.2% by multiwall carbon nanotubes (MWNTs), when the condition was normal pH, contact time 60 min with agitation speed 240 rpm and initial concentration of dyes 10 mg/L (Ola et al., 2020). Fiyadh et al. reviewed the most efficient adsorption process for heavy metals from water is to use functionalized CNTs with deep eutectic solvents as an adsorbent (Seef et al., 2019).
Hydrogeochemistry and human health risks of groundwater fluoride in Jinhuiqu irrigation district of Wei river basin, China
Published in Human and Ecological Risk Assessment: An International Journal, 2019
Bin Xu, Yan Zhang, Jinfeng Wang
Fluoride is an essential element for human health, which is mainly obtained through drinking water (Li et al.2018a; Singh et al.2018). A suitable quantity of fluoride is necessary to develop bones and dental enamel. The excessive ingestion of fluoride, however, has adverse health effects, especially the dental fluorosis for children and skeletal fluorosis for adults [World Health Organization (WHO) 2017]. It is estimated that over 200 million people worldwide are suffering from fluorosis due to high fluoride in drinking water (Ayoob and Gupta 2006; Thapa et al.2018). Former studies showed that the endemic fluorosis was found in 20 countries covering Asia, Europe, Africa and America. Approximately 65% of endemic fluorosis is attributed to fluoride contamination of drinking water (Fallahzadeh et al.2018). The WHO has set the permissible limit of fluoride as 1.5 mg/L for drinking purpose (WHO 2017). In China, the permissible limit of fluoride for drinking water set by the national guidelines is 1.0 mg/L (General Administration of Quality Supervision, Inspection & Quarantine of China, Standardization Administration of China 2017) due to the severity of high-fluoride water distributed around most part of China. In northwest China, more than 60 million people live in areas where groundwater is the main water source and the risk of fluorosis is high (Liu et al.2018).
Spatial distribution and seasonal variation in fluoride enrichment in groundwater and its associated human health risk assessment in Telangana State, South India
Published in Human and Ecological Risk Assessment: An International Journal, 2018
Adimalla Narsimha, Sanda Rajitha
Groundwater is the principal source of drinking water in the study region. The fluoride in groundwater was higher than the recommended limit of 1.5 mg/L set by the WHO. The mean concentrations of fluoride were 1.26 and 2.21 in pre- and post-monsoon seasons respectively. About 31% in pre-monsoon and 80% in post-monsoon groundwater sampling location showed 1.5 to 4 mg/L fluoride content in groundwater. A considerable amount of fluoride enters into the human body through drinking water. So, HQFluoride was calculated as an indicator of non-carcinogenic health risk hazard and higher values were obtained in the post-monsoon season. The range of HQFluoride was 0.44–2.44 and 0.89–4.67 for children, 0.36–2.00 and 0.73–3.82 for adult females, and 0.41–2.26 and 0.82–4.31 for adult males respectively. The study reveals that children are highly prone to the health risks caused by dental fluorosis through the intake of elevated fluoride water. Therefore, the study indicates that the frequent monitoring of groundwater is a vital step to avoid human health risks and that groundwater must be tested prior to consumption to avoid health risks, especially in children.