Abstract
Schwertmannite, a kind of iron oxyhydrosulfate mineral, can removal arsenic(III) from arsenic(III)-bearing groundwater by the adsorption process. In this study, schwertmannite was bio-synthesized by Acidithiobacillus ferrooxidans LX5 in shaking flasks (160 rpm) containing a 0.16 mol/L FeSO4 liquid solution. After bio-synthesis, 25.5% of the bio-synthesized schwertmannite adhered to the reactor wall (designated as adhered-sch) and the remainder was suspended in the system (designated as suspended-sch). Particles of adhered-sch exhibited a fractured structure with a small specific surface area (4.36 m2/g) and total pore volume (3.13 × 10−2 cm3/g). In contrast, suspended-sch had a spiny structure (similar in appearance to a hedgehog), and a larger specific surface area (9.62 m2/g) and total pore volume (8.01 × 10−2 cm3/g). When 0.25 g/L of adhered-sch was used as an adsorbent for arsenic(III) removal from 1 mg/L arsenic(III)-bearing waters (at pH 7.5), the arsenic(III) removal efficiency was 43.2% after 4 h of adsorption. However, this efficiency could be increased by 50% by using suspended-sch as the adsorbent. Furthermore, by adding 13.3 g/L and 26.7 g/L additional schwertmannite into the reactor system prior to schwertmannite bio-synthesis, all synthesized schwertmannite remained suspended in the bio-synthesis systems, and the ferrous ions’ bio-oxidation efficiency was improved to a certain extent. Due to the friction effect between the introduced schwertmannite and the reactor wall, adhered-sch was eliminated. The outcomes of this study will provide the necessary data for schwertmannite bio-synthesis and arsenic(III) removal from arsenic(III)-bearing groundwater.
Highlights
Arsenic is defined as a Category 1 and Group A human carcinogen by the International Association for Research on Cancer because of its high toxicity and carcinogenicity [1,2]
During schwertmannite bio-synthesis by A. ferrooxidans LX5, some of the synthesized schwertmannite adheres to the reactor wall, while the rest remains suspended in the system
The total pore volume, specific surface area, and arsenic(III) removal efficiency of adhered-sch are smaller than for the suspended-sch. In both adhered-sch and suspended-sch, mesopores in the synthesized schwertmannite represent a modest pore volume (~30% of total pore volume), but make a great contribution to the specific surface area (~65% of total specific surface area); this relationship is especially true for mesopores with a ~3–20 nm diameter
Summary
Arsenic is defined as a Category 1 and Group A human carcinogen by the International Association for Research on Cancer because of its high toxicity and carcinogenicity [1,2]. Groundwater is frequently contaminated by arsenic due to natural geological processes and many anthropogenic activities [4], and arsenic(III) is the predominant arsenic species existing in anoxic groundwater [5]. High health risks caused by drinking high-arsenic groundwater is a significant problem in many parts of the world, including China [6]. In China, high arsenic-bearing groundwater mainly exists in Inner Mongolia, Shanxi, Xinjiang, etc., including 40 counties of eight provinces. Arsenic concentration in groundwater samples collected from the Hetao Plain in the Inner Mongolia Autonomous Region, Datong in Shanxi province, and Dzungaria district in Xinjiang province can be up to 1.09 mg/L [7], 1.82 mg/L [8], and 0.85 mg/L [9], respectively. Except for China, the arsenic levels in groundwater from many other countries in the world often surpass
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
