Removal Arsenic Research Articles

Adsorption of Arsenite from Groundwater Using Titanium Dioxide

AbstractThe present research focused in the feasibility of using a common, inexpensive, and non‐toxic material as titanium dioxide (TiO2) for arsenite (As(III)) removal from aqueous solutions. Batch experiments were conducted to test the effects of adsorbent dose, contact time, and stirring speed. The As(III) removal has been carried out under natural environment conditions (temperature 23 ± 3°C and water pH 8 ± 0.2). Results show that the kinetic rate of As(III) adsorption was higher in the first 30 min and decreases thereafter. The maximum removal efficiency was 96% with 1.5 g/L in 1.5 h of contact time. The As–TiO2 system has reached equilibrium in 1 h, regardless of the titanium dioxide dosage. The adsorption process was best described by the Freundlich's isotherm model, which indicates that the multilayer adsorption should be involved in the process of As(III) removal. The contact between the As(III) and TiO2 was done mainly by convection and diffusion. The mass transfer coefficient (β) has been found between 0.8 × 10−5 and 12.3 × 10−5 cm/s. The thermodynamic analysis showed a feasible, spontaneous, and exothermic adsorption process. TiO2 is a safe substance for human health and is a feasible and efficient alternative treatment for arsenic removal from water.Chronic exposures at low‐level of arsenic will cause adverse health effects. TiO2 is a feasible low‐cost material for remove arsenic. Reaction mechanisms, the zeta potential and adsorption kinetics were analyzed. A dose of 1.5 g/L removed 92% (Co = 120 µg As/L) of arsenic in 0.9 h. This conditions allows to get a treated water quality in agreement with the international standards (<10 µg/L).

Synergistic degradation of pyrene and volatilization of arsenic by cocultures of bacteria and a fungus

The combination of two bacteria (Bacillus sp. PY1 and Sphingomonas sp. PY2) and a fungus (Fusarium sp. PY3), isolated from contaminated soils near a coking plant, were investigated with respect to their capability to degrade pyrene and volatilize arsenic. The results showed that all strains could use pyrene and arsenic as carbon and energy sources in a basal salts medium (BSM), with the combined potential to degrade pyrene and volatilize arsenic. Bacillus sp. PY1, Sphingomonas sp. PY2 and Fusarium sp. PY3 were isolated from the consortium and were shown to degrade pyrene and volatilize arsenic independently and in combination. Fungal-bacterial coculture has shown that the most effective removal of pyrene was 96.0% and volatilized arsenic was 84.1% after incubation in liquid medium after 9 days culture, while bioremediation ability was 87.2% in contaminated soil with 100 mg·kg−1 pyrene. The highest level of arsenic volatilization amounted to 13.9% of the initial As concentration in contaminated soil after 63 days. Therefore, a synergistic degradation system is the most effective approach to degrade pyrene and remove arsenic in contaminated soil. These findings highlight the role of these strains in the bioremediation of environments contaminated with pyrene and arsenic.

Preparation of an Iron Oxide Modified Montmorillonite for Removal of Arsenic in Waters

Most concerns have focused on the arsenic (As) contamination in wastewater. Montmorillonite (MMT) has been proved to be a good adsorbent for removal heavy metals existing as cation in ground water while it is invalid for anions. However, arsenic usually exists as anions in aqueous. Accordingly, suitable modifications on MMT need to be done before using. This paper presents the results that a kind of commercial MMT has been modified by iron oxides under normal and inverse titration conditions. The x-ray diffraction (XRD), Thermal Gravimetry Analysis and Differential Thermal Analysis (TGA-DTA) and SBET analysis have been employed to elucidate the modification mechanisms. Modification characteristic analysis illustrated that the iron oxide associated with MMT by coated style as polymerization of hydroxyl-Fe (Fe (OH) 3) under inverse titration condition. Under normal titration condition, on the other hand, the iron oxide associated with MMT predominant by intercalation as goethite (FeOOH). The arsenic removal efficiencies of different modified products for polluted water have also been verified by batch experiments. Results proved that Iron oxide modified MMT on the removal efficiency of arsenic significantly increased and the normal titration is better than inverse titration as indicated by the arsenic removal ratios under the same experimental conditions. Based on these results, the iron oxide modified MMT by normal titration procedure is a promising material for removal arsenic in wastewaters.

Effect of alpha-lipoic acid on the removal of arsenic from arsenic-loaded isolated liver tissues of rat

The patient of chronic arsenic toxicity shows oxidative stress. To overcome the oxidative stress, several antioxidants such as beta-carotene, ascorbic acid, alpha-tocopherol, zinc and selenium had been suggested in the treatment of chronic arsenic toxicity. In the present study universal anti-oxidant (both water and lipid soluble antioxidant) alpha-lipoic acid was used to examine the effectiveness of reducing the amount of arsenic from arsenic-loaded isolated liver tissues of rat. Isolated liver tissues of Long Evans Norwegian rats were cut into small pieces and incubated first in presence or absence of arsenic and then with different concentrations of alpha-lipoic acid during the second incubation. alpha-Lipoic acid decreases the amount of arsenic and malondialdehyde (MDA) in liver tissues as well as increases the reduced glutathione (GSH) level in dose dependent manner. These results suggest that ?-lipoic acid remove arsenic from arsenic-loaded isolated liver tissues of rat.

Estudio de eliminación de arsénico con resinas de intercambio iónico en agua potable de Zimapán, Estado de Hidalgo, México

Anionic exchange resins were research with respect its capacity for removal arsenic content in water. Water of well V from Zimapan Hidalgo Mexico was used to make this research, because this water have a mean concentration of 480 ± 11 μg·L-1 of arsenic and it isavailable as drinking water. The exchange resins employed were two strong anionic, one macroreticular (IRA-900) and other gel type (IRA-400), as soon as one third anionic weak macroreticular type (IRA-96). The experiments carried with this resins showing that IRA-900 has highest efficient in the process of arsenic removal from drinking water, because, it showed a treatment capacity of 700 Vagua·Vres-1; while that capacities of IRA-400 e IRA-96 resins were 320 and 52 Vagua·Vres-1 respectively. The mean concentration of arsenic residue in the treatise water was 24 μg·l-1 and it is within the maximum level permissible by Mexican official norm for drinking water.

An overview on chronic arsenism via drinking water in PR China.

Chronic endemic arsenism via drinking water was first found in Taiwan in 1968, and reported in Xinjiang Province in mainland China in the 1980s. Arsenism has become one of the most serious endemic diseases in China in the last two decades. Up to now, the disease has been found in Inner Mongolia, Shanxi, Ningxia, Jilin and Qinghai provinces. According to the Chinese maximum limit standard of arsenic (As) in drinking water, over 2 millions people have been exposed to high arsenic and about 10,000 persons were diagnosed as arsenism patients. There are different As concentrations in the water of different sites, even in the same area. Most of the As concentrations range from 0.05 to 2.0mg/l. The incidence of arsenism increases as As concentrations in drinking water and the drinking time increase. The age distribution of patients with arsenism ranged from 3 to 80 years old with peak prevalence in adults. A dose-effect relationship between the status of arsenism and arsenic level and drinking time has been shown. New high-arsenic areas in China have been discovered during recent investigations. In order to reduce the adverse health effects of arsenism, the central and local governments of China have provided significant funds to change water levels of As and at the same time take general measures to "reduce arsenic intake, remove arsenic from the body and treat the patients". After the implementation of these control measures in certain regions, the clinical symptoms and signs of 30% of the patients were improved. There was no change in 52% of patients and only 18% of patients got worse. It is suggested that future work in the research and control of arsenism in China should include: (1) identify all the high arsenic areas in China, (2) study the association of arsenism with fluorosis, (3) determine individual susceptibility, (4) select biomarkers for diagnosis in the early stage of a arsenism, and (5) investigate the molecular mechanisms of carcinogenesis.