Alluvial and gypsum karst geological transition favors spreading arsenic contamination in Matehuala, Mexico

Effects of Silicic Acid on Leaching Behavior of Arsenic from Spent Calcium-Based Adsorbents with Arsenite

“…Assuming that one Ca atom is chemically bonded to two O atoms and that one Si atom is chemically bonded to four O atoms, the formation of calcium silicate species with a Ca/Si molar ratio of 0.5-4 is stoichiometrically conceivable, as shown by Equations ( 19)- (23). In addition, when H 3 SiO 4…”

“…Assuming that one Ca atom is chemically bonded to two O atoms and that one Si atom is chemically bonded to four O atoms, the formation of calcium silicate species with a Ca/Si molar ratio of 0.5-4 is stoichiometrically conceivable, as shown by Equations ( 19)- (23). In addition, when H3SiO4 − is assumed to be the reactive silicic acid species, "H4SiO4" on the left side of the above formulas must be replaced with "H3SiO4 − + H + ".…”

“…If the only cause of the decrease in both MCa and MSi-T was the production of the calcium silicate species caused by a reaction between Ca 2+ leached from the spent adsorbent and the silicic acid species in the solution, the value of ΔMCa/ΔMSi-T should be between 0.5 and 4, based on Equations ( 19)− (23). Most of ΔMCa/ΔMSi-T were found to be in the range If the only cause of the decrease in both M Ca and M Si-T was the production of the calcium silicate species caused by a reaction between Ca 2+ leached from the spent adsorbent and the silicic acid species in the solution, the value of ∆M Ca /∆M Si-T should be between 0.5 and 4, based on Equations ( 19)− (23). Most of ∆M Ca /∆M Si-T were found to be in the range 0.5-4, as shown in Table 10.…”

“…There are numerous reports on groundwater contamination with arsenic (As), which is a global problem. In recent years, it has become a major challenge in regions across Asia (such as Bangladesh [1-5], Pakistan [6,7], Iran [8], India [9][10][11], Sri Lanka [12], Vietnam [13,14], Cambodia [15], and China [16][17][18]), Latin America (such as Argentina [19,20], Uruguay [21], and Mexico [22,23]) and West and South Africa [24,25]. Podgorski and Berg [26] reported the arsenic pollution in groundwater around the world; the proportion of affected area in Asia was 64%, in South America 14%, North America 10%, Africa 9%, Oceania 2% and Europe 1%.…”

Removal of Arsenate from Contaminated Water via Combined Addition of Magnesium-Based and Calcium-Based Adsorbents

“…Consuming As-containing drinking water and food can cause chronic arsenicism, leading to dermal lesions, peripheral neuropathy, skin cancer, bladder and lung cancers, and peripheral vascular disease, as well as acute As intoxication [1]. As-contaminated groundwater is often directly consumed, especially in developing regions such as Southern and Southeast Asia [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16], Western and Southern Africa [17,18], and Latin America [19][20][21][22][23].…”