Bioscorodite Crystallization in an Airlift Reactor for Arsenic Removal

Abstract

Bioscorodite (FeAsO 4 •2H 2 O) crystals were crystallized in an airlift reactor fed at pH 1.2 and 72 °C. Arsenic removal was limited by the biological ferrous iron oxidation. In continuous operation, the iron oxidation initially was 30% and increased to 80% in few days when the iron and dissolved oxygen concentration were increased. The bioscorodite yield was 3 g/g of arsenic removed. The first precipitates were identified as scorodite having a dipyramidal octahedron habit with an Fe/As molar ratio of 1.55. The stability test (TCLP) classified the crystals as suitable for storage with a leached arsenic concentration of 0.5 mg L −1 after 60 days. Settling rates of bioscorodite crystals between 50 and 140 m h −1 were measured. Size distribution frequency indicates that bioscorodite crystals grew from an average size of 30 μm during batch operation to 160 μm at the end of the continuous operation phase. The morphology and size of the crystals guarantee their freeflowing nature, avoiding scaling. The biggest and most stable crystals can be harvested by sedimentation, to select the material best suited for final disposal.

Forced Biomineralization: A Review

“…One industrially relevant example of As-related biomineralization under extreme conditions is bioscorodite (FeAsO 4 •2H 2 O), for which microbial crystallization was demonstrated by Gonzalez-Contreras et al [78][79][80] using As(V) as a reactant. Bioscorodite is precipitated in one single step at pH 1.2 and 70 • C. Batch crystallization of bioscorodite leads to agglomeration of precipitates and formation of flakes; scaling of bioscorodite precipitates was also observed in continually stirred tank reactors.…”

“…Bioscorodite is precipitated in one single step at pH 1.2 and 70 • C. Batch crystallization of bioscorodite leads to agglomeration of precipitates and formation of flakes; scaling of bioscorodite precipitates was also observed in continually stirred tank reactors. The term "indirect biomineralization of scorodite" was proposed in 2012 and was patented by Paques B.V. (Balk, The Netherlands) as the ARSENOTEQ™ process [79,80]. According to the proposed biotechnological approach, the iron-oxidizing archaeon Acidianus suljidivorans is able to precipitate scorodite in the absence of any primary minerals or seed crystals when grown on 0.7 g/L ferrous iron (Fe 2+ ) at 80 • C and pH 0.8 in the presence of 1.9 g/L arsenate (H 3 AsO 4 ).…”

Factors to Enable Crystallization of Environmentally Stable Bioscorodite from Dilute As(III)-Contaminated Waters

“…Hence, to realize effective scorodite formation even from dilute As solutions, a microbiological approach using Fe(II)-oxidizing thermophiles (72-80 • C) was proposed by Gonzalez-Contreras et al (2010, 2012a, 2012b) using 13-37 mM (1000-2800 mg/L) As(V) as starting reactant [11][12][13]. Later our studies enabled simultaneous microbial As(III) and Fe(II) oxidation using the thermophilic archaeon Acidianus brierleyi (70 • C), which for the first time realized one-step bioscorodite crystallization from original wastewater solutes of As(III) and Fe(II), without necessitating any As(III) oxidation pretreatments or chemical oxidants [14,15]: So far bioscorodite was successfully produced by Ac.…”

Dissolution of realgar by Acidithiobacillus ferrooxidans in the presence and absence of zerovalent iron: Implications for remediation of iron-deficient realgar tailings

“…Arsenopyrite (FeAsS) and arsenian pyrite (Fe(S, As)2) are common iron-rich As sulfides that can incorporate gold, silver, etc., but mining and hydrometallurgy operations involving them can result in significant release of As to the environment (Reich et al, 2005;Corkhill and Vaughan, 2009). Microbial techniques can be used to treat these mine wastes by enhancing As immobilization (Gonzalezcontreras et al, 2010(Gonzalezcontreras et al, , 2012Okibe et al, 2017). For example, Egal et al (2009) found that various Acidithiobacillus ferrooxidans (A. ferrooxidans) strains can help the formation of kinds of ferric oxyhydroxy sulfates (e.g.…”