Batch and continuous precipitation of scorodite from dilute industrial solutions

Caetano, Michelle L.; Ciminelli, V.S.T.; Rocha, Sônia Denise Ferreira; Spitale, Matheus C.; Caldeira, Claudia L.

doi:10.1016/j.hydromet.2008.04.010

Cited by 48 publications

(19 citation statements)

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“…1,4) In order to synthesize stable ferric arsenate compounds, precipitation processes of scorodite in water have been investigated by examining the precipitates and analyzing the solution. [16][17][18][19] In these studies, scorodite particles were precipitated by reacting Fe(III) with As(V) in water; it should be noted that the solution conditions in these studies were different in each study. In the coprecipitation of scorodite, the following reaction is considered to occur:…”

Section: Introductionmentioning

confidence: 99%

Coprecipitation of Large Scorodite Particles from Aqueous Fe(II) and As(V) Solution by Oxygen Injection

Shinoda

Tanno

Fujita³

et al. 2009

Mater. Trans.

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A novel method for synthesizing large scorodite (FeAsO 4 . 2H 2 O) particles was recently developed for the fixation of arsenic. This method involves the coprecipitation of scorodite particles from an Fe(II) and As(V) aqueous solution at approximately 95 C by oxygen injection. In order to understand the process of coprecipitation of scorodite particles by this method, X-ray diffractometry (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used for characterizing reaction products extracted from the suspension during the reaction. The SEM observation showed that the formation of large scorodite particles was almost completed after a reaction time of 3 h, and then, fine particles precipitated on the large particles by further reactions. The XRD results indicated that scorodite particles with specific lattice parameters were formed in the reaction. The XPS results indicated that the arsenic composition on the surface of the scorodite particles decreased until 3 h from the start of precipitation reaction and increased thereafter. These results correspond to the results on the morphology of the scorodite particles obtained by SEM. Furthermore, X-ray absorption spectra (XAS) in the range of X-ray absorption near edge structure (XANES) were measured for gel-like reaction products formed in the initial stages of the reaction. The spectra revealed that the gel-like reaction products were composed of Fe(II) and Fe(III). The coprecipitation of scorodite particles synthesized by the novel method is discussed on the basis of these results together with previous results on the analyses of iron and arsenic concentrations in solution.

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Section: Introductionmentioning

confidence: 99%

Coprecipitation of Large Scorodite Particles from Aqueous Fe(II) and As(V) Solution by Oxygen Injection

Shinoda

Tanno

Fujita³

et al. 2009

Mater. Trans.

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“…However, As removal remained relatively incomplete at pH 1.2 (91%), compared to at pH 1.5 (98%) (at day 30; Figure 3a). Overall lower supersaturation levels (Figure 3c) owing to lower As(V) ion activities at pH 1.2 ( Figure 3d) as well as continuous As precipitation likely promoted steady and continuous bioscorodite crystal growth, as was reported under abiotic atmospheric pressure conditions [4,5,16]. …”

Section: Effect Of Initial Phmentioning

confidence: 60%

“…Although the Fe/As molar ratios of all scorodite seeds and products were 1.0-1.1 and 1.3-1.4, respectively, the amount of Fe leached generally remained only below one-tenth of that of As (Table 2), due to selective re-precipitation of Fe(III) at pH 4.9. Other chemical scorodite studies reported TCLP leachabilities ranging 0.1-13.6 As-mg/L [7,10,16], generally often higher than those of bioscorodite (Table A2). Such stability difference between bioscorodite seeds and chemical seeds may be attributed to factors such as involvement of cell encrustation, structural water content and morphological difference, and crystal maturity (speed of crystallization), but the exact reasons remain to be unclear.…”

Section: Stability Of Final Bioscorodite Productsmentioning

confidence: 95%

“…Other abiotic studies under atmospheric pressure condition using As(V) and Fe(III) as starting species also have reported a positive effect of seeds with high specific surface area, e.g., the better scorodite precipitation kinetics were observed by using finer seeds such as hematite and hydrothermal scorodite [6]. Caetano et al (2009) reported that a specific surface area higher than 270 m 2 /g was required to achieve 85% As removal [16].…”

Section: Effect Of Seedmentioning

confidence: 98%

“…From studies of conventional abiotic scorodite syntheses, seed feeding (scorodite or other heterogeneous crystals) was shown to be one of the influential factors to promote scorodite formation [4,6,16]. Initial pH was also reported to affect the stability and Fe/(As + S) ratio of the resultant scorodite product [17].…”

Section: Introductionmentioning

confidence: 99%

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

Tanaka

Okibe

2018

Minerals

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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 (FeAsO 4 ·2H 2 O) 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.

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Lanthanide Arsenate Chemical Thermodynamics

Gontijo,

Ciminelli,

Rocha

et al. 2024

Proceedings of the 63rd Conference of Metallurgists, COM 2024

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Batch and continuous precipitation of scorodite from dilute industrial solutions

Cited by 48 publications

References 10 publications

Coprecipitation of Large Scorodite Particles from Aqueous Fe(II) and As(V) Solution by Oxygen Injection

Coprecipitation of Large Scorodite Particles from Aqueous Fe(II) and As(V) Solution by Oxygen Injection

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

Lanthanide Arsenate Chemical Thermodynamics

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