59
revision, we will focus on the water pollution caused by fluoride and arsenic, being
the former considered the most massive poisoning in history (Bhattacharjee 2007).
The ingestion of arsenic and fluoride is causing severe health problems worldwide (González-Horta et al. 2015; Limón-Pacheco et al. 2018). Among the affected
countries are Bangladesh, India, Vietnam, Thailand, Taiwan, Mongolia, China,
Argentina, Chile, Bolivia, Brazil, Mexico, Germany, Hungary, and the United States
(Hossain 2006; Alemayehu et al. 2011; Chowdhury et al. 2018; Khan et al. 2019;
Bhardwaj et al. 2019; Thakur 2019; Agusa et al. 2014; Tiankao and Chotpantarat
2018). Reports indicate that millions of people in different parts of the world are
ingesting water with high concentrations of arsenic and fluoride (high than 300 μg/L
(Smith et al. 2000) and 30 mg/L, (Dey et al. 2004), respectively). The high arsenic
concentrations can cause human diseases such as arsenicosis, hyperkeratosis, keratosis, and cancer (Choong et al. 2007). On the other hand, fluoride is beneficial in a
concentration of 0.7 mg L
−1
but represents a health hazard once it exceeds a concentration of 1.5 mg L
−1
. Chronic fluoride exposure can cause dental and skeletal fluorosis, cancer, negative effects on deoxyribonucleic acid structure, Alzheimer’s
disease, and kidney and neurological damage. High fluoride concentrations in water
can interfere with mineral metabolism, vitamins, carbohydrates, proteins, and lipids
(Ozsvath 2009).
Arsenic is a naturally ubiquitous metalloid in the earth’s crust, making geological the main source of arsenic in water. Arsenic exists in three main oxidation states,
+5, +3, and −3, known as arsenate, arsenite, and arsine, respectively. Arsenic pollution of drinking water can be caused by naturally ocurring minerals or can be related
to anthropogenic activities, such as mining (since about 245 minerals contain arsenic), the use of fossil fuels and pesticides (Bissen and Frimmel 2003). Arsenic is one
of the 20 most abundant elements in nature, and we can also find it in the human
body and in seawater (Mandal and Suzuki 2002). Arsenic appears in natural waters
commonly as oxoanion, being the arsenate (AsO 4
3−
) and arsenite (AsO 3
3−
) the most
common oxidation states. Figure 3.1 shows the -Log [H
+
] vs. -Log concentration
diagram for those chemical species. The predominant chemical speciation of arsenate in the pH of natural waters (6–8) is as mono- and dianion, while for arsenite,
the predominant chemical form is the neutral oxo-complex.
On the other hand, fluoride occurs in the environment mainly associated with
metals, including sellaite (MgF 2 ), fluorite (CaF 2 ), cryolite (Na 3 AlF 6 ), and fluorapatite (Ca 10 (PO 4 ) 6 F 2 ). When a suitable chemical environment surrounds the fluoridecontaining minerals, the minerals dissolve, and the fluorine becomes part of the
dissolved components of the water reservoir. Additional fluoride sources are related
to industrial activities, including metal casting operations (iron, steel, and aluminum), production of ceramics, and the production of phosphate- based fertilizers.
Besides, many sources of fluoride for human include food, medicaments, cosmetics,
and organofluorine compounds, among others (Council 2006). The chemical speciation of fluoride in groundwater appears in Fig. 3.2. Arsenic can be seen, and the
predominant chemical species of fluorine in groundwater is the anionic form.
Interesting, the presence of metal alkaline cations promotes the formation of fluorine ionic pairs with a positive charge (i.e., MgF
+
, CaF
+
).
3 Metal Oxyhydroxide Composites for Halogens and Metalloid Removal
revision, we will focus on the water pollution caused by fluoride and arsenic, being
the former considered the most massive poisoning in history (Bhattacharjee 2007).
The ingestion of arsenic and fluoride is causing severe health problems worldwide (González-Horta et al. 2015; Limón-Pacheco et al. 2018). Among the affected
countries are Bangladesh, India, Vietnam, Thailand, Taiwan, Mongolia, China,
Argentina, Chile, Bolivia, Brazil, Mexico, Germany, Hungary, and the United States
(Hossain 2006; Alemayehu et al. 2011; Chowdhury et al. 2018; Khan et al. 2019;
Bhardwaj et al. 2019; Thakur 2019; Agusa et al. 2014; Tiankao and Chotpantarat
2018). Reports indicate that millions of people in different parts of the world are
ingesting water with high concentrations of arsenic and fluoride (high than 300 μg/L
(Smith et al. 2000) and 30 mg/L, (Dey et al. 2004), respectively). The high arsenic
concentrations can cause human diseases such as arsenicosis, hyperkeratosis, keratosis, and cancer (Choong et al. 2007). On the other hand, fluoride is beneficial in a
concentration of 0.7 mg L
−1
but represents a health hazard once it exceeds a concentration of 1.5 mg L
−1
. Chronic fluoride exposure can cause dental and skeletal fluorosis, cancer, negative effects on deoxyribonucleic acid structure, Alzheimer’s
disease, and kidney and neurological damage. High fluoride concentrations in water
can interfere with mineral metabolism, vitamins, carbohydrates, proteins, and lipids
(Ozsvath 2009).
Arsenic is a naturally ubiquitous metalloid in the earth’s crust, making geological the main source of arsenic in water. Arsenic exists in three main oxidation states,
+5, +3, and −3, known as arsenate, arsenite, and arsine, respectively. Arsenic pollution of drinking water can be caused by naturally ocurring minerals or can be related
to anthropogenic activities, such as mining (since about 245 minerals contain arsenic), the use of fossil fuels and pesticides (Bissen and Frimmel 2003). Arsenic is one
of the 20 most abundant elements in nature, and we can also find it in the human
body and in seawater (Mandal and Suzuki 2002). Arsenic appears in natural waters
commonly as oxoanion, being the arsenate (AsO 4
3−
) and arsenite (AsO 3
3−
) the most
common oxidation states. Figure 3.1 shows the -Log [H
+
] vs. -Log concentration
diagram for those chemical species. The predominant chemical speciation of arsenate in the pH of natural waters (6–8) is as mono- and dianion, while for arsenite,
the predominant chemical form is the neutral oxo-complex.
On the other hand, fluoride occurs in the environment mainly associated with
metals, including sellaite (MgF 2 ), fluorite (CaF 2 ), cryolite (Na 3 AlF 6 ), and fluorapatite (Ca 10 (PO 4 ) 6 F 2 ). When a suitable chemical environment surrounds the fluoridecontaining minerals, the minerals dissolve, and the fluorine becomes part of the
dissolved components of the water reservoir. Additional fluoride sources are related
to industrial activities, including metal casting operations (iron, steel, and aluminum), production of ceramics, and the production of phosphate- based fertilizers.
Besides, many sources of fluoride for human include food, medicaments, cosmetics,
and organofluorine compounds, among others (Council 2006). The chemical speciation of fluoride in groundwater appears in Fig. 3.2. Arsenic can be seen, and the
predominant chemical species of fluorine in groundwater is the anionic form.
Interesting, the presence of metal alkaline cations promotes the formation of fluorine ionic pairs with a positive charge (i.e., MgF
+
, CaF
+
).
3 Metal Oxyhydroxide Composites for Halogens and Metalloid Removal