Abstract
Applicability of the bioscorodite method (use of the thermo-acidophilic Fe(II)-oxidizing archaeon Acidianus brierleyi for arsenic (As) oxidation and immobilization at 70 °C) was tested for synthetic copper refinery wastewaters of a wide range of dilute initial As(III) concentrations ([As(III)]ini = 3.3–20 mM) with varying initial [Fe(II)]/[As(III)] molar ratios ([Fe(II)]ini/[As(III)]ini = 0.8–6.0). Crystallization of scorodite (FeAsO4·2H2O) tends to become increasingly challenging at more dilute As(III) solutions. Optimization of conditions such as initial pH, seed feeding and initial [Fe(II)]/[As(III)] molar ratio was found critical in improving final As removal and product stability: Whilst setting the initial pH at 1.2 resulted in an immediate single-stage precipitation of crystalline bioscorodite, the initial pH 1.5 led to a two-stage As precipitation (generation of brown amorphous precursors followed by whitish crystalline bioscorodite particles) with a greater final As removal. The formation process of bioscorodite precipitates differed significantly depending on the type of seed crystals fed (bio- versus chemical- scorodite seeds). Feeding the former was found effective not only in accelerating the reaction, but also in forming more recalcitrant bioscorodite products (0.59 mg/L; Toxicity Characteristic Leaching Procedure (TCLP) test). Under such favorable conditions, 94–99% of As was successfully removed as crystalline bioscorodite at all dilute As(III) concentrations tested by setting [Fe(II)]ini/[As(III)]ini at 1.4–2.0. Providing an excess Fe(II) (closer to [Fe(II)]ini/[As(III)]ini = 2.0) was found beneficial to improve the final As removal (up to 98–99%) especially from more dilute As(III) solutions.
Highlights
Arsenic (As) contamination is a growing problem in metallurgical operations due to the increasing metal demand that necessitates processing of As-bearing low-grade copper sulfide ores such as enargite (Cu3 AsS4 ) and tennantite (Cu12 As4 S13 )
As one of the approaches to immobilize soluble As species from wastewaters, formation of scorodite (FeIII AsV O4 ·2H2 O) is considered an ideal form of
Studies on scorodite synthesis employed hydrothermal processes targeting high As(V) concentrations of 170–460 mM (13,000–35,000 mg/L) [2,3]. They were later followed by studies using atmospheric pressure, again targeting high As(V) concentration ranges of 130–670 mM
Summary
Arsenic (As) contamination is a growing problem in metallurgical operations due to the increasing metal demand that necessitates processing of As-bearing low-grade copper sulfide ores such as enargite (Cu3 AsS4 ) and tennantite (Cu12 As4 S13 ). Studies on scorodite synthesis employed hydrothermal processes targeting high As(V) concentrations of 170–460 mM (13,000–35,000 mg/L) [2,3] They were later followed by studies using atmospheric pressure (mostly at around 95 ◦ C), again targeting high As(V) concentration ranges of 130–670 mM (10,000–50,000 mg/L) [4,5,6,7,8,9,10]. While these chemical approaches are generally effective for high As(V). Since such chemical treatments generally require a Minerals 2018, 8, 23; doi:10.3390/min8010023 www.mdpi.com/journal/minerals
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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 callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
