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Inorganic Chemical Pollutants
Published in William J. Rea, Kalpana D. Patel, Reversibility of Chronic Disease and Hypersensitivity, Volume 4, 2017
William J. Rea, Kalpana D. Patel
Arsenic competes with selenium, and selenium is known to reduce arsenic toxicity. Arsenicals were used as medicine, and arsenic acid and nitrophenol forms of arsenic are used as growth enhancers and for feed efficiency of pigs and poultry.789–791 Arsenic is excreted, mainly through the urine, in its inorganic form and methylated derivatives. Because hair, nail, and liver show high levels of arsenic, they are considered excretory routes. Chronic toxicity is characterized by weakness, prostration, aching muscles, gastrointestinal upset, peripheral neuropathy (increased nerve conduction), and changes in pigmentation of the nails and skin. Arsenic antagonizes thyroid function with resultant goiter. It is a carcinogen or cocarcinogen.791 Certainly, excessive arsenic exposure will exacerbate chemical sensitivity.
Arsenic Trioxide Leaching and Scorodite Crystallization in Methanesulfonic Acid
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Junmo Ahn, Jiajia Wu, Jaewoo Ahn, Jaeheon Lee
Arsenic trioxide leaching was performed at different temperatures from 21 to 95°C as shown in Figure 2. Arsenic extraction showed very fast kinetics and reached to 94% within 3 hours with 0.1 M MSA with periodic additions of hydrogen peroxide at 95°C. At 80°C, arsenic extraction also quickly increased to 93% in 4 hours. When temperature was further decreased to 21°C, the ultimate arsenic extraction was only 80% at 24 hour. Debekaussen et al. also agreed that As2O3 dissolution increased from 12 to 114.6 g/L by increasing temperature from 25 to 100°C in a mildly acidic solution (pH = 5.9) (Debekaussen, Droppert and Demopoulos 2001). In spite of slower leaching kinetic at ambient temperature, high arsenic extraction of 80% was achieved in 0.1 M MSA with H2O2 addition in this study, indicating that the arsenic extraction was improved by H2O2 addition. It has been reported that hydrogen peroxide improves arsenic trioxide leaching by oxidation of dissolved arsenite (H3AsO3) to form arsenate or arsenic acid (H3AsO4) whose solubility is higher than arsenite (Vink 1996). It indicates that oxidation of As (III) to As (V) is required to increase the solubility of As2O3 as written in Equation (2). Therefore, different oxidation methods were compared to investigate the effects on arsenic dissolution from As2O3.
Remediation and improvement of 2,4-dichlorophenol contaminated soil by biochar-immobilized laccase
Published in Environmental Technology, 2021
Zhaobo Wang, Dajun Ren, Yusheng Zhao, Chaofan Huang, Shuqin Zhang, Xiaoqin Zhang, Chen Kang, Zhiqun Deng, Huiwen Guo
First, 5 g of the air-dried sample was weighed, passed through a 2 mm aperture sieve, and placed into a 150 mL bottle. Then 50.0 mL of 0.03 mol/L ammonium fluoride-0.025 mol/L hydrochloric acid extract was added into the bottle and shaken for 30 min at a constant temperature of 20–25°C. The mixed solution was filtrated and 5.00–10.00 mL of the filtrate was placed into a 50 mL flask. Then 10 mL of 3% arsenic acid solution was added into the flask and mixed well with the filtrate. Water was added to the flask to make the solution volume of about 30 mL, then dinitro acid indicator was added to adjust the solution to slightly yellow. Next, 5.00 m molybdenum anti-chromogenic agent was added and some water was added to make the solution up to volume. The color-developed sample was tested with a spectrophotometer and the absorbance was measured at the wavelength of 700 nm. The corresponding content of phosphorus was obtained from the standard curve. where c is the phosphorus concentration in the color-developed solution (μg/mL), V is the volume of the color-developed solution (mL), D is the fractional multiple, and m is the mass of air-dried sample (g).
Chemical and radiation grafted chitosan for the mitigation of arsenic from contaminated water
Published in Journal of Dispersion Science and Technology, 2020
The most important parameter influencing the adsorption capacity is the pH of adsorption medium. Arsenic is sensitive to pH in ground waters (pH 6.5–8.5) under oxidizing and reducing conditions. Under oxidizing conditions, H2AsO4- is dominant at low pH (less than about pH 6.9), while at higher pH, HAsO42- becomes dominant (H3AsO4° and AsO43- may be present in extremely acidic and alkaline conditions, respectively). Under reducing conditions at pH less than about pH 9.2, the uncharged arsenite species H3AsO3° predominates. It was well documented that the surface functional groups of adsorbents together with the forms of arsenic species (adsorbate) are strongly pH dependent. The dissociation reaction of arsenic acid (arsenate) is shown below