Abstract
Schwertmannite (Sch) is an efficient adsorbent for arsenic(III) removal from arsenic(III)-contaminated groundwater. In this study, bio-schertmannite was synthesized in the presence of dissolved ferrous ions and Acidithiobacillus ferrooxidans LX5 in a culture media. Bio-synthesized Sch characteristics, such as total organic carbon (TOC), morphology, chemical functional groups, mineral phase, specific surface area, and pore volume were systematically studied after it was dried at 105 °C and then heated at 250–550 °C. Differences in arsenic(III) removal efficiency between 105 °C dried-sch and 250–550 °C heated-sch also were investigated. The results showed that total organic carbon content in Sch and Sch weight gradually decreased when temperature increased from 105 °C to 350 °C. Sch partly transformed to another nanocrystalline or amorphous phase above 350 °C. The specific surface area of 250 °C heated-sch was 110.06 m2/g compared to 5.14 m2/g for the 105 °C dried-sch. Total pore volume of 105 °C dried-sch was 0.025 cm3/g with 32.0% mesopore and 68.0% macropore. However, total pore volume of 250 °C heated-mineral was 0.106 cm3/g with 23.6% micropore, 33.0% mesopore, and 43.4% macropore. The arsenic(III) removal efficiency from an initial 1 mg/L arsenic(III) solution (pH 7.5) was 25.1% when 0.25 g/L of 105 °C dried-sch was used as adsorbent. However, this efficiency increased to 93.0% when using 250 °C heated-sch as adsorbent. Finally, the highest efficiency for arsenic(III) removal was obtained with sch-250 °C due to high amounts of sorption sites in agreement with the high specific surface area (SSA) obtained for this sample.
Highlights
Groundwater is generally the primary resource for drinking water and irrigation [1], and a large amount of groundwater is used without any pre-treatment
◦the color changed from reddish-brown to when the heating temperature increased and reached 550 C
The aggregation of individual bio-schwertmannite spherical particles showed no obvious change after heating at 250–550 ◦ C. These results indicate that the aggregation of bio-schwertmannite particles was due to the extracellular polymeric substances (EPS) secreted by A. ferrooxidans or A. ferrooxidans cells
Summary
Groundwater is generally the primary resource for drinking water and irrigation [1], and a large amount of groundwater is used without any pre-treatment. Arsenic contamination of groundwater is an important environmental problem that affects human health and quality of life [2,3]. Long-term exposure to arsenic-contaminated drinking water can cause serious health problems, such as skin damage, bladder cancer, liver cancer, kidney cancer, nasal cancer, and gastric cancer [5]. Minerals 2017, 7, 9 the human risk for cancer and other serious diseases, the World Health Organization (WHO) has admonished countries to limit the As concentration in drinking water to 10 μg/L [6]. Chakraborti et al [10] investigated the arsenic contamination of groundwater in Patna district (Bihar, India); the study detected a maximum arsenic concentration of
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