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Article

Effective Treatment of High Arsenic Smelting Wastewater Synergetic Synthesis of Well-Crystallized Scorodite

by
Yuanhang Liao
1,2,
Jianhui Wu
1,2,
Chengyun Zhou
3,*,
Yanjie Liang
1 and
Guomeng Yan
4
1
School of Metallurgy and Environmental, Central South University, Changsha 410083, China
2
Zijin Mining Group Company Limited, Shanghang 364200, China
3
College of Environmental Science and Engineering, Hunan University, Changsha 410083, China
4
Sainz Environmental Protection Co., Ltd., Nonferrous Industry Pollution Control and Equipment Engineering Technology Research Center, Changsha 410083, China
*
Author to whom correspondence should be addressed.
Water 2025, 17(11), 1599; https://doi.org/10.3390/w17111599
Submission received: 30 April 2025 / Revised: 20 May 2025 / Accepted: 23 May 2025 / Published: 25 May 2025
(This article belongs to the Section Wastewater Treatment and Reuse)
Browse Figures
Versions Notes

Abstract

:
Arsenic-containing acidic wastewater from nonferrous heavy smelting industry is a dangerous source of arsenic pollution due to its complex composition, high acidity, and strong toxicity. In this study, an environment-friendly strategy was proposed, in which highly stable scorodite was synthesized in acidic wastewater. The effects of initial pH, Fe/As molar ratio, and oxidation-reduction potential (ORP) on the morphology, particle size, phase composition, and leaching stability of scorodite were systematically investigated. The results demonstrate a distinct morphological evolution with increasing pH. The products were transitioned from bone-shaped to rice grain-shaped, and then turned to bipyramidal polyhedral-shaped and amorphous aggregates. When the Fe/As molar ratio was increased, the scorodite crystallization quickly formed well-defined particles (the size was 15–20 μm). Higher ORP values led to progressively irregular morphologies, reduced particle sizes, and ultimately formed amorphous ferric arsenate. The large-grained scorodite with regular morphology and high leaching stability from high-arsenic solutions (25 g/L) was produced under optimal conditions (initial pH 1.5, Fe/As 1.5, ORP 385 mV). These findings provide critical technical support for arsenic solidification from waste liquids under atmospheric pressure conditions.

1. Introduction

Arsenic has shown extremely wide applications in multiple fields, covering alloy manufacturing, medical pharmaceuticals, and the production of semiconductor materials, among others. However, its potential harm to the ecological environment and human health cannot be ignored. Arsenic mainly migrates through water bodies, thus causing pollution. Therefore, the purification process of arsenic removal from water bodies has become an unavoidable environmental protection problem in human production and life. Arsenate precipitation is a common method for water purification. Among various arsenate precipitates, ferric arsenate demonstrates the best environmental stability due to its lowest solubility product, a property particularly prominent in the natural mineral scorodite. Consequently, the artificial synthesis of scorodite with high environmental stability has gradually become a research focus [1,2,3,4].
Since the 1870s, scorodite minerals have been successively discovered in nature, and relevant case reports have emerged in an endless stream [5,6,7]. People have started in-depth research on the crystal structure, composition, solubility, and leaching stability of scorodite [8]. Since the 1980s, research on the artificial synthesis of scorodite has been carried out successively at home and abroad. The synthesis methods are mainly divided into two types: the hydrothermal method and the atmospheric pressure method. The hydrothermal method is usually carried out under hydrothermal conditions of 100–250 °C, while the atmospheric pressure method is carried out under conditions below 100 °C.
In 1988, Dutrizac et al. successfully synthesized scorodite with good crystallinity using the iron nitrate-arsenic acid-lithium sulfate system under the conditions of initial pH 0.8–1.8, arsenic concentration of 15 g/L, and temperature of 125–160 °C [9]. However, no detection and analysis of its leaching stability were carried out. G.P. Demopoulos et al. synthesized scorodite with a crystal size of about 20 μm at 150 °C using the iron sulfate-arsenic acid-sodium sulfate system [10]. Subsequently, they switched to the iron chloride-arsenic acid-sodium chloride system. By stepwise pH regulation and the introduction of seeds, the supersaturation of arsenic in the reaction system was maintained at a relatively low level, and scorodite with a median particle size of 40 μm was synthesized at 80–95 °C, and the leaching toxicity of arsenic was 0.06 mg/L. Luo et al. synthesized large-sized scorodite particles with irregular morphology at 160 °C [11]. They proposed that stirring would accelerate the nucleation rate of scorodite, which was not conducive to the growth of single crystals. Moreover, K+ and SO42− in the reaction system could combine with Fe3+ to form jarosite, which had a competitive precipitation relationship with scorodite, thus affecting the purity of scorodite [12,13].
Liu et al. compared hydrothermal, atmospheric pressure, and improved atmospheric pressure methods for the synthesis of scorodite [14]. They found that the higher the crystallinity of scorodite, the smaller its specific surface area and the better its leaching stability. Zhang et al. used hydrogen peroxide instead of air as an oxidant to synthesize polycrystalline scorodite with a particle size of 20 μm at 150 °C, and the arsenic leaching concentration reached 0.08 mg/L [15]. Fujita et al. [16,17,18] used the ferrous sulfate-arsenic acid-sodium sulfate system with air as an oxidant. At 50 °C, bone-shaped scorodite with a particle size of 3–5 μm and poor crystallinity was obtained; at 70 °C, bone-shaped and bipyramidal scorodite with a particle size of 20 μm was obtained; and at 95 °C, bipyramidal scorodite with a mixture of single crystals and polycrystals and a particle size of 20 μm was obtained. Wang et al. [19] pointed out that the nucleation rate and crystal morphology of scorodite could be effectively regulated by controlling the initial supersaturation of the reaction system. Min et al. [20,21] successfully synthesized polycrystalline scorodite by an air oxidation method at 80–95 °C, and the leaching toxicity of arsenic was lower than 1.0 mg/L. Although a large amount of research data has been accumulated [22,23,24,25,26,27,28,29,30,31], and a detailed study of various influencing factors in the reaction system has been carried out, there is still a lack of systematic analysis on the influence laws of various influencing factors on the crystal morphology and particle size of scorodite, as well as the correlation between crystal morphology and leaching stability.
In this study, scorodite was synthesized in a high-arsenic solution containing ferrous sulfate and sodium sulfate. The effects of key factors on the morphology, particle size, and leaching stability of the synthesized product were systematically investigated. A novel method for the efficient synthesis of scorodite from high-concentration arsenic-bearing solutions is proposed.

2. Materials and Methods

2.1. Materials

The ferrous sulfate (FeSO4, Sinopharm Group Chemical Reagent Co., Ltd., Shanghai, China, 10 wt.%), sodium carbonate solution (Na2CO3, Sinopharm Group Chemical Reagent Co., Ltd., Shanghai, China, 15 wt.%), sulfuric acid (H2SO4, Sinopharm Group Chemical Reagent Co., Ltd., Shanghai, China, 20 wt.%), and hydrogen peroxide solution (H2O2, Sinopharm Group Chemical Reagent Co., Ltd., Shanghai, China, 5 wt.%). The arsenic-containing wastewater originated from oxidative leaching of arsenic sulfide slag, with its key parameters summarized in Table 1. All chemical reagents used in this study are of analytical grade, except for the arsenic sulfide slag.

2.2. Synthesis of Scorodite Precursors

At room temperature, a ferrous sulfate solution and an arsenic-containing solution were mixed in a 500 mL beaker at specific Fe/As molar ratios of 1.0 and 1.5. The initial pH was slowly adjusted using sodium carbonate solution, and the initial ORP was regulated with hydrogen peroxide solution, followed by continuous stirring for 0.5 h to obtain a gray-green scorodite precursor mixture. During the synthesis, magnetic stirring was maintained at 100 r/min, with the initial pH controlled between 0.5 and 3.0, and the initial ORP stabilized in the range of 385–585 mV. The precursor formation rate was regulated by gradual adjustments to pH and ORP, ensuring detection values remained stable within 30 s.

2.3. Synthesis of Scorodite

The scorodite precursor mixture was transferred into a 500 mL flat-bottom flask. Then, the flask with a ground-glass stopper was sealed. The sealed flask was immersed in an oil bath, and the reaction conditions were maintained at 75 °C for 8 h after reaching the target temperature. Upon completion, the reaction mixture was cooled and filtered. The filter residue was washed thoroughly, then dehydrated in a vacuum dryer at 60 °C for 8 h to obtain the target product: scorodite (molecular formula: FeAsO4·2H2O). To minimize nucleation and promote crystal growth, no stirring was applied during the synthesis [9]. Experimental parameters are listed in Table 2.

2.4. Analysis and Detection

The ORP of the reaction system was measured using a 501 ORP composite electrode, which is calibrated against the standard hydrogen electrode. Thus, the measured value directly reflects the potential difference of the solution relative to the standard hydrogen potential. Ion concentrations in the solution were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES, Thermo Scientific, ICAP-7200, Waltham, MA, USA), while arsenic concentration was determined via atomic fluorescence spectroscopy (AFS, Beijing Titan, AFS8220, Beijing, China). Phase composition of the product was characterized by X-ray diffraction (XRD, LabX XRD-6100, Tokyo, Japan)), morphological features observed via scanning electron microscopy (SEM, Carl Zeiss AG, GeminiSEM300, Oberkochen, Germany), elemental qualitative analysis and mapping conducted by energy-dispersive X-ray spectroscopy, and elemental composition with valence states analyzed by X-ray photoelectron spectroscopy (XPS, Thermo Scientific, Escalab 250Xi, Waltham, MA, USA). The leaching stability of the product was evaluated via the sulfuric acid-nitric acid leaching procedure, conducted in accordance with the Solid Waste Leaching Toxicity Test Method—Sulfuric Acid-Nitric Acid Method HJ/T 299-2007 [32]. The HJ/T 299-2007 is a standard method in China for evaluating the leaching stability of solid waste. The leaching agent was the mixture of concentrated sulfuric acid and concentrated nitric acid (pH of 3.20 ± 0.05), a liquid-solid ratio of 10:1, and a leaching time of 18 ± 2 h.

3. Results and Discussion

3.1. Effect of the Initial pH

The initial pH range was set at 0.5–3.0, with experimental parameters corresponding to Numbers 1–5 in Table 2. The XRD patterns of the product were displayed in Figure 1. As shown in Figure 1, the diffraction peak intensity first increases and then decreases with increasing pH. In the initial pH range of 0.5–1.5, the product’s diffraction peak intensity gradually rises with increasing pH, accompanied by a morphological transition from bone-shaped to bipyramidal polyhedral, as illustrated in Figure 2a–e. Although the transformation mechanism remains unclear, it is evident that higher pH values promote the formation of higher-purity scorodite. The XRD analysis showed that the diffraction peaks of the prepared scorodite were highly matched with the pure scorodite (JCPDS 37-0468) [33]. When the initial pH increases to 2.0, the scorodite diffraction peak weakens, with amorphous byproducts adhering to the crystal surface; at pH 3.0, the scorodite diffraction peak nearly disappears, and the product consists of amorphous iron-arsenic compounds.
The SEM images of the product were presented in Figure 2. As shown in Figure 2, the significant morphological change was from bone-shaped to bipyramidal polyhedral morphology, and finally to amorphous aggregates. At initial pH 0.5–1.0, the product exhibits a bone-shaped morphology, with notable growth as the long-axis length increases from 5 μm to 15 μm and the surface becomes smoother and more regular with increasing pH. In the pH range of 1.0–1.5, the morphology transitioned from bone-shaped to bipyramidal polyhedral, with particle sizes ranging from 2.5–5 μm. As pH was increased to 1.5–2.0, an amorphous shell was developed on the surfaces of the bipyramidal polyhedra. At pH 2.0–3.0, the morphology of the product was transformed from bipyramidal polyhedra into amorphous aggregates by further increasing pH. The EDS spectrum of the pH 3.0 product (Figure 2f) shows trace amounts of copper, indicating the presence of amorphous copper-arsenic compounds—likely contributing to the drastic reduction in diffraction peak intensity.
To synthesize scorodite with higher purity and more regular morphology, the initial reaction pH should be controlled between 1.0 and 2.0, with an optimal value of 1.5 recommended. Notably, two distinct growth forms—a bone-shaped morphology and a bipyramidal polyhedral morphology—were observed during scorodite synthesis, with a transition zone occurring at initial pH 1.0–1.5. Since no prior studies have explained this morphological transition, the crystalline transformation mechanism in this pH transition range requires in-depth investigation.

3.2. Effect of the Initial Fe/As Molar Ratio

The effect of the Fe/As molar ratio at the optimal pH of 1.5 is shown in Figure 3g–i. As the initial Fe/As molar ratio increases from 1.0 to 1.5, the product maintains a bipyramidal polyhedral morphology. The particle size remains approximately 2.5 μm, and the diffraction peak intensity shows a certain degree of enhancement. Notably, SEM imaging reveals the presence of bipyramidal polyhedral particles with a size of ~20 μm, suggesting that surplus iron ions in the reaction system promote scorodite growth.
To further investigate the role of surplus iron ions in crystal growth, additional experiments were conducted at initial pH values of 0.5 and 1.0, with results shown in Figure 3a–f. At pH 0.5, when the Fe/As molar ratio is increased from 1.0 to 1.5, the bone-shaped morphology of the particles is maintained. However, the long-axis length of the particles extends from 5 μm to 10 μm, accompanied by a slight enhancement in the diffraction peak intensity. At pH 1.0, when the Fe/As molar ratio increases from 1.0 to 1.5, the bone-shaped morphology of the particles transforms into a rice grain-shaped one. Meanwhile, the long-axis length of the particles remains within the 15–20 μm range without significant change, and the diffraction peak intensity shows no variation. Notably, SEM images display a crystal with a bipyramidal polyhedral morphology (~20 μm), further verifying the role of surplus iron ions in crystal development.
These results confirm that surplus iron ions in the reaction system can facilitate the growth of scorodite and enhance crystal structural integrity. Under static (unstirred) reaction conditions, excess Fe(II/III) likely provides additional adsorption sites for precursors, enhances the capture of As(III/V), reduces the diffusion rate of Fe and As species, and moderately inhibits scorodite nucleation—thereby accelerating crystal growth rate. Based on these findings, an Fe/As molar ratio greater than 1.0 is recommended, with 1.5 being selected as the optimal value in this study.

3.3. Effect of the Initial ORP

As shown in Figure 4, the diffraction peak intensity of the products decreases significantly with increasing ORP. At an initial ORP of 385–485 mV, the diffraction peaks perfectly match the scorodite standard (PDF-#37-0468). Conversely, when the initial ORP rises to 585 mV, diffraction peaks become nearly undetectable, and the product transforms into an amorphous phase, as evident in Figure 5d. As shown in Figure 5, the product morphology undergoes distinct transformations with increasing ORP: when the initial ORP is 385–425 mV, rising ORP reduces particle size from 10–20 μm to 2.5 μm while maintaining a bipyramidal polyhedral morphology; as ORP increases to 425–485 mV, particle size stabilizes at 2.5 μm but amorphous coatings develop on crystal surfaces, indicating partial amorphization; and when the initial ORP reaches 585 mV, the product forms finely aggregated particles (~1 μm) with a highly agglomerated amorphous structure, exhibiting no discernible crystalline features.
In this study, an ORP serves as a direct indicator of the precursor solution’s redox state, which is inherently tied to the concentrations of Fe(III) and As(V) ions. Elevated ORP values promote the oxidation of Fe(II) to Fe(III) and As(III) to As(V), thereby increasing their concentrations in the solution [34]. Conversely, a lower ORP suppresses these oxidation reactions, maintaining Fe(III)/As(V) at relatively low levels. This redox-dependent ion regulation directly influences scorodite nucleation and crystal growth: at lower ORP (~385 mV), limited Fe(III)/As(V) concentrations can slow nucleation but favor crystal expansion, yielding large bipyramidal polyhedral particles; as ORP rises to 425 mV, increased Fe(III)/As(V) enhances nucleation rates while restricting growth, resulting in smaller bipyramidal tetrahedral particles; at high ORP (485–585 mV), excessive Fe(III)/As(V) surpasses critical supersaturation thresholds, driving the formation of amorphous iron-arsenic phases and inhibiting crystalline scorodite formation entirely.

3.4. EDS Analysis

According to the SEM results of FA-9, the size of scorodite is relatively large. In order to further investigate the formation mechanism of FA-9, EDS surface scanning was used to analyze the elemental composition and distribution (Figure 6). As depicted in Figure 6a, the product exhibits a bipyramidal polyhedral morphology with dominant isotropic growth, well-defined crystal planes and boundaries, and a size of approximately 28.5 μm. Notably, a small number of small-sized crystals are attached to the surface of the primary crystal. This observation suggests that regulating the attachment and distribution of crystal nuclei and secondary crystals may influence the growth mode and final morphology of the primary crystals. Figure 6b–e reveals uniform distributions of Fe, As, and O across the scorodite crystal surface. However, the Fe/As molar ratio on the surface is unexpectedly 1.53—notably higher than the theoretical stoichiometric Fe/As ratio of 1.0 for scorodite. Furthermore, the iron and arsenic content in FA-9 was further quantified using ICP-AES. The results of ICP-AES indicate that the overall iron-to-arsenic molar ratio of FA-9 is 1.012, which is very close to the theoretical value based on the molecular formula of stinky onion stone. Therefore, we believe that a layer of iron-containing compounds may adhere to the surface of scorodite, resulting in a higher iron arsenic molar ratio than the theoretical value. The phase of this iron-containing compound needs further study.

3.5. XPS Analysis

Elemental identification and analysis of the large crystal surface in FA-9 were performed via XPS, and the results are shown in Figure 7. A comparative analysis of the arsenic and iron compositions obtained from EDS, XPS, and ICP-AES is summarized in Table 3. Figure 7a displays the full XPS spectrum, while Figure 7b–d presents the peak fitting of Fe, As, and O using CasaXPS software (2007 version). As shown in Figure 7a, the detected elements include Fe, As, O, and C, with the C signal likely arising from adventitious contamination or sample preparation. From the fitting of the Fe 2p in Figure 7b, binding energy signals at 713.08 eV and 725.45 eV correspond to Fe 2p3/2 and Fe 2p1/2, respectively. The high binding energy values are characteristic of Fe3+, indicating that iron exists in the trivalent valence state. In the O 1s peak fitting spectrum of Figure 7c, binding energy signals at 532.51 eV and 531.58 eV are observed, which can be attributed to -OH and O2− species, respectively.
For the As 3d peak fitting in Figure 7d, two well-resolved peaks at 45.50 eV (3d5/2) and 46.04 eV (3d3/2) are observed. These binding energies align with the characteristic values for As5+ in arsenate compounds, confirming the pentavalent oxidation state of arsenic. Based on the above characterization analysis, we speculate that the hydroxyl group may come from the amorphous hydrated iron on the surface of FA-9, resulting in a higher iron-to-arsenic molar ratio on its surface than the theoretical molecular formula. The formation pathway of FA-9 is that iron arsenic precipitates in the form of amorphous hydroxy iron arsenic compounds, and the rate of amorphous compound formation is controlled by adjusting pH, iron arsenic concentration, and potential value. Under optimal reaction conditions, amorphous hydroxy iron arsenic compounds nucleate after redissolution, with a relatively slow nucleation rate. The formed crystal nuclei are further bound together in the most stable form through the adsorption of hydroxy iron arsenic compounds, forming regular bipyramidal polyhedra, and ultimately forming large-sized individual odorous onion stones. When the reaction conditions are not optimized, the binding of garnet crystal nuclei becomes chaotic and disordered, forming other morphologies such as rod-shaped and elliptical.

3.6. Leaching Stability of Products

In this study, the leaching toxicity of the products was evaluated, and the test results are presented in Table 4. As Table 4 clearly indicates, the leaching stability of the products is closely linked to their morphology, particle size, and phase composition, showing the following trends: bipyramidal polyhedron > bipyramidal-like polyhedron > bone-shaped crystals > agglomerated particles. The particle size exhibits the following trends: large crystals > small crystals > non-uniform particles. Overall, scorodite with higher purity, more regular crystal shape, and larger particle size exhibits better leaching stability. Conversely, poorly controlled synthesis conditions tend to form amorphous ferric arsenate, which significantly reduces the product’s leaching resistance. The minimum leaching toxicity of the synthesized products in this study was 0.08 mg/L. The result is significantly lower than the limit specified in the Identification Standard for Hazardous Wastes—Leaching Toxicity Identification GB 5085.3-2007 [35] and meets the arsenic concentration requirements for Class V surface water quality outlined in the Surface Water Environmental Quality Standard GB 3838-2002 [36], demonstrating excellent ecological compatibility and absence of potential pollution risks. Future investigations will focus on enhancing scorodite leaching stability by optimizing reaction temperatures, extending aging durations, and seeding crystal-induced crystallization, with the goal of preparing products with superior leaching resistance and enhanced environmental friendliness.

4. Conclusions

In this study, large-sized and high-purity scorodite with regular morphology and stable leaching performance was synthesized from an arsenic acid-ferrous sulfate-sulfuric acid solution system by optimizing synthesis parameters under atmospheric pressure. The morphology of the synthesized scorodite was significantly influenced by the initial pH, Fe/As molar ratio, and ORP of the reaction system. When the initial pH was ranged from 1.0 to 1.5, the product morphology was transformed from bone-shaped to bipyramidal polyhedral. At an initial pH of approximately 1.5, biconical polyhedral scorodite with a particle size of 2.5 μm was obtained. Excessively high or low pH values were unfavorable for crystal growth. The excess adsorption sites in the precursor mixture, enhancing arsenic capture capacity, were provided by a mixture of initial Fe/As molar ratio around 1.5, effectively inhibiting the migration rate of arsenate-iron ions, reducing nucleation rate, and promoting scorodite crystal growth. ORP was a key factor in regulating the concentrations of Fe(III) and As(V) ions in the precursor mixture. When the initial ORP of the precursor was approximately 385 mV, the nucleation rate and crystal growth rate of scorodite were relatively balanced, yielding scorodite with a particle size of 15–20 μm, regular morphology, and good leaching stability. The leaching stability of the product was significantly impacted by the morphology, size, and phase composition. The higher purity, more regular crystal form, and larger particle size corresponded to better leaching stability. Large-sized bipyramidal polyhedral scorodite exhibited the best leaching stability.

Author Contributions

Writing—review and editing, J.W., C.Z., and Y.L. (Yanjie Liang); investigation, Y.L. (Yuanhang Liao); methodology, Y.L. (Yanjie Liang); validation, G.Y. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Program for the National Key Research and Development Program of China, grant number 2021YFB3801403.

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

Author Yuanhang Liao and Jianhui Wu were employed by the company Zijin Mining Group Company Limited. Author Guomeng Yan was employed by the company Sainz Environmental Protection Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Water 17 01599 g001
Figure 1. XRD patterns of products at different initial pHs: (a) 0.5–2.0, (b) 3.0, with Fe/As molar ratios 1.0.
Figure 1. XRD patterns of products at different initial pHs: (a) 0.5–2.0, (b) 3.0, with Fe/As molar ratios 1.0.
Water 17 01599 g001
Water 17 01599 g002
Figure 2. (a–e) SEM images of products at different initial pHs: (a) 0.5, (b) 1.0, (c) 1.5, (d) 2.0, (e) 3.0, with Fe/As molar ratios 1.0; (f) EDS spectrum and quantitative composition (wt%) of (e).
Figure 2. (a–e) SEM images of products at different initial pHs: (a) 0.5, (b) 1.0, (c) 1.5, (d) 2.0, (e) 3.0, with Fe/As molar ratios 1.0; (f) EDS spectrum and quantitative composition (wt%) of (e).
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Water 17 01599 g003
Figure 3. XRD patterns and SEM images of products at Fe/As molar ratios 1.0 and 1.5, with different initial pHs: (a–c) 0.5, (d–f) 1.0, (g–i) 1.5.
Figure 3. XRD patterns and SEM images of products at Fe/As molar ratios 1.0 and 1.5, with different initial pHs: (a–c) 0.5, (d–f) 1.0, (g–i) 1.5.
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Water 17 01599 g004
Figure 4. XRD patterns of products at various initial ORPs: (a) 385 mV–485 mV; (b) 585 mV.
Figure 4. XRD patterns of products at various initial ORPs: (a) 385 mV–485 mV; (b) 585 mV.
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Water 17 01599 g005
Figure 5. SEM images of products at different initial ORPs: (a) 385 mV, (b) 425 mV, (c) 485 mV, (d) 585 mV.
Figure 5. SEM images of products at different initial ORPs: (a) 385 mV, (b) 425 mV, (c) 485 mV, (d) 585 mV.
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Figure 6. (a) SEM image of large particle scorodite; (b–f) EDS spectrum of large particle scorodite containing elemental mapping of Fe, As, O, S, Cu.
Figure 6. (a) SEM image of large particle scorodite; (b–f) EDS spectrum of large particle scorodite containing elemental mapping of Fe, As, O, S, Cu.
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Figure 7. XPS spectrum of large particle scorodite: (a) Full spectrum; (b) Fe 2p; (c) As 3d; (d) O 1s.
Figure 7. XPS spectrum of large particle scorodite: (a) Full spectrum; (b) Fe 2p; (c) As 3d; (d) O 1s.
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Table 1. Main indicators of experimental raw materials.
Table 1. Main indicators of experimental raw materials.
IndexIon Concentration (mg/L)ORP/mVpH
AsFeCuZnNi
Arsenic-containing solution25,00010.215.38.92.33400.89
Table 2. Experimental parameters of the synthesis reaction.
Table 2. Experimental parameters of the synthesis reaction.
NumberFe/As Molar RatioInitial pH Initial ORP/mVFinal pH Final ORP/mVProduct Name
110.54250.36406FA-1
211.04250.84407FA-2
311.54251.28409FA-3
412.04251.82408FA-4
513.04252.98410FA-5
61.50.54250.33404FA-6
71.51.04250.86408FA-7
81.51.54251.41413FA-8
91.51.53851.43383FA-9
101.51.54851.38474FA-10
111.51.55851.36570FA-11
Table 3. Analysis of Fe/As molar ratio in FA-9 via EDS, XPS, and ICP-AES detection.
Table 3. Analysis of Fe/As molar ratio in FA-9 via EDS, XPS, and ICP-AES detection.
Detection MethodElementAtomic %Weight %Fe/As Molar Ratio
EDSO//1.534
Fe60.5453.39
As39.4646.61
XPSC 1s32.2516.301.566
O 1s50.1733.77
Fe 2p10.7330.47
As 3d6.8519.45
ICP-AESFe50.3043.041.012
As49.7056.96
Table 4. Arsenic leaching concentration of different morphologies and phase products.
Table 4. Arsenic leaching concentration of different morphologies and phase products.
NumberProduct NameTopographySizePhaseArsenic Leaching Concentration (mg/L)
1FA-1Bone-shaped5 μmScorodite1.56
2FA-2Bone-shaped15 μmScorodite0.74
3FA-3Bipyramidal polyhedral-shaped2.5 μmScorodite0.49
4FA-4Biconical polyhedral-shaped (with shell)2.5 μmScorodite0.66
5FA-5Agglomerate-shapedNo specific sizeAmorphous ferric arsenate compounds11.71
6FA-6Bone-shaped10 μmScorodite1.32
7FA-7Bone-shaped + rice grain-shaped15–20 μmScorodite0.28
8FA-8Bipyramidal polyhedral-shaped2.5 μmScorodite0.19
9FA-9Bipyramidal polyhedral-shaped15–30 μmScorodite0.08
10FA-10Agglomerate-shaped2.5–10 μmScorodite + amorphous ferric arsenate compounds2.35
11FA-11Agglomerate-shaped1 μmAmorphous ferric arsenate compounds5.21
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Liao, Y.; Wu, J.; Zhou, C.; Liang, Y.; Yan, G. Effective Treatment of High Arsenic Smelting Wastewater Synergetic Synthesis of Well-Crystallized Scorodite. Water 2025, 17, 1599. https://doi.org/10.3390/w17111599

AMA Style

Liao Y, Wu J, Zhou C, Liang Y, Yan G. Effective Treatment of High Arsenic Smelting Wastewater Synergetic Synthesis of Well-Crystallized Scorodite. Water. 2025; 17(11):1599. https://doi.org/10.3390/w17111599

Chicago/Turabian Style

Liao, Yuanhang, Jianhui Wu, Chengyun Zhou, Yanjie Liang, and Guomeng Yan. 2025. "Effective Treatment of High Arsenic Smelting Wastewater Synergetic Synthesis of Well-Crystallized Scorodite" Water 17, no. 11: 1599. https://doi.org/10.3390/w17111599

APA Style

Liao, Y., Wu, J., Zhou, C., Liang, Y., & Yan, G. (2025). Effective Treatment of High Arsenic Smelting Wastewater Synergetic Synthesis of Well-Crystallized Scorodite. Water, 17(11), 1599. https://doi.org/10.3390/w17111599

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