Remediation system and method for oxygen-deficient vanadium pollution environment

Abstract

The invention discloses an oxidation pretreatment system for an anoxic vanadium polluted environment and a remediation method, and belongs to the technical field of environmental chemistry and pollution control. The system comprises an adding unit, a pH regulation and control unit and a monitoring unit, the adding unit is used for adding amorphous ferrihydrite into the polluted water body as an oxidizing agent, and the pH regulation and control unit is used for regulating the pH value of the water body and maintaining the pH value between 5.0 and 7.0. The remediation method comprises the following steps: firstly, carrying out oxidation pretreatment on low-valence vanadium by using amorphous ferrihydrite under an anoxic condition, and then adding an adsorption material to adsorb and fix generated pentavalent vanadium. The problem that low-valence vanadium is difficult to directly remove by a traditional adsorbent in an anoxic environment is solved, efficient and stable repair of vanadium pollution is achieved through the synergistic effect of directional oxidation and obligate adsorption, and the method has the advantages of being environmentally friendly and low in cost.

Description

Technical Field

[0001] This invention belongs to the field of environmental chemistry and pollution control technology, specifically relating to a pretreatment system for oxidizing low-valent vanadium to pentavalent vanadium in hypoxic or low-oxygen environments, and a remediation method for its application. Background Technology

[0002] Vanadium often exists in multiple valence states in natural water bodies and contaminated sites, among which low-valence vanadium (V(III), V(IV)) exhibits certain mobility and toxicity. To achieve the final removal and fixation of vanadium, it needs to be converted into a form that is easily and efficiently captured. Pentavalent vanadium (V(V)) exists in water as an oxyanion and can be efficiently and stably adsorbed and fixed by specific iron-based materials (especially amorphous ferrohydrate). Therefore, the selective oxidation of widely present low-valence vanadium to V(V) in polluted environments has become a key pretreatment step bridging the pollution status quo and efficient terminal treatment.

[0003] However, achieving this controllable and efficient oxidation pretreatment in anoxic / hypoxic environments such as groundwater and deep sediments presents significant challenges. Traditional chemical oxidants (such as permanganate and persulfate) are difficult to activate under anoxic conditions, have low efficiency, are costly, and are prone to causing secondary pollution. In recent years, iron-mediated oxidation processes have attracted attention due to their environmental friendliness, but existing technologies have significant limitations: 1) The active iron species are unclear, and there is a lack of systematic understanding of iron species that efficiently and selectively oxidize vanadium under anoxic conditions; 2) The pretreatment process is uncontrollable, and the oxidation rate is strongly coupled with multiple factors such as pH and Eh, making optimization difficult; 3) The pretreatment effect is unstable and cannot efficiently coordinate with subsequent adsorption units, resulting in low efficiency of the entire remediation process chain. Therefore, developing a vanadium oxidation pretreatment system and method that is both highly efficient and process-controllable for anoxic environments is an urgent need for building a complete and efficient vanadium pollution remediation technology chain. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology in the low efficiency of remediation of low-valent vanadium pollution under hypoxic conditions, and to provide a stable and controllable oxidation pretreatment system and remediation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides an oxidation pretreatment system for remediating vanadium-contaminated water, comprising:

[0007] (a) A dosing unit for adding amorphous ferrohydrate as an oxidant to the polluted water body;

[0008] (b) A pH control unit for adjusting and maintaining the pH value of the polluted water body within the range of 5.0 to 7.0;

[0009] (c) A monitoring unit for detecting the valence distribution of vanadium in the polluted water.

[0010] Preferably, the dosing unit is further used to add Fe(II)-organic acid complexes, wherein the organic acid is oxalic acid, citric acid, or tartaric acid. Preferably, the system further includes a redox potential control unit for adjusting the redox potential Eh of the polluted water body to a range of 150mV to 350mV (relative to a standard hydrogen electrode).

[0011] Secondly, the present invention provides a method for remediating an oxygen-deficient vanadium-contaminated environment, comprising the following steps performed sequentially:

[0012] (i) Oxidation pretreatment step: Under the condition that the dissolved oxygen concentration is less than 1.0 mg / L, amorphous ferrohydrate is added to the polluted water containing low-valent vanadium, and the pH value of the polluted water is controlled between 5.0 and 7.0 to carry out the reaction, so that some or all of the low-valent vanadium is converted into pentavalent vanadium.

[0013] (ii) Adsorption and fixation step: Add adsorption material to the water body treated in step (i) to remove the pentavalent vanadium.

[0014] Preferably, in step (i), the dosage of the amorphous ferrohydrate is 0.1 g to 2.0 g per liter of polluted water. More preferably, the dosage is 0.5 g to 1.5 g. Even more preferably, the dosage is 0.8 g to 1.0 g.

[0015] Preferably, in step (i), the pH value of the polluted water is controlled between 5.5 and 6.5. More preferably, the pH value is controlled between 6.0 and 6.2.

[0016] Preferably, in step (i), the redox potential Eh of the polluted water body is further controlled between 150 mV and 350 mV (relative to a standard hydrogen electrode). More preferably, Eh is controlled between 200 mV and 300 mV.

[0017] Preferably, in step (i), the reaction is carried out at a temperature of 20°C to 30°C.

[0018] Preferably, in step (ii), the adsorbent material is a composite material with amorphous ferrohydrate as the main active component.

[0019] The beneficial effects of this invention are:

[0020] (1) It was clearly proposed and verified that amorphous ferroalloys have a significant and efficient oxidation capacity for low-valent vanadium (V(III) / V(IV)) under specific anoxic and pH conditions (5.0-7.0), and can directionally convert them into pentavalent vanadium (V(V)) which is easy to be subsequently adsorbed, thus solving the key pretreatment problem of vanadium pollution remediation under anoxic conditions.

[0021] (2) By controlling the reaction system within the optimal range through a pH adjustment unit, the efficiency and stability of the oxidation process are significantly improved. Combined with the subsequent specific adsorption step, a synergistic process of "directional oxidation-specific adsorption" is formed. Examples show that the total vanadium removal rate of this synergistic process (>90%) is significantly higher than that of direct adsorption (approximately 30%) or the scheme using traditional oxidant pretreatment (approximately 52%).

[0022] (3) The core oxidant of the system (amorphous ferrohydrate) is widely available, easy to prepare, and has good environmental compatibility, avoiding the secondary pollution and high cost problems that may be caused by traditional strong oxidants, and has good engineering application potential.

[0023] (4) Comparative experiments have shown that, under the same hypoxia and pH conditions, the oxidation efficiency and final synergistic repair effect of other common iron minerals (such as goethite) or traditional oxidants are far lower than those of the present invention. This highlights the significant and superior technical effect produced by the combination of amorphous ferrohydrate and a specific hypoxia-pH window. Attached Figure Description

[0024] Figure 1 This is an oxidation kinetic curve of V(III) on amorphous ferrohydrate in Example 1 of the present invention (showing a decrease in V(III) concentration and an increase in V(V) concentration). Detailed Implementation

[0025] The present invention will be further illustrated below with specific embodiments and comparative examples, but the invention is not limited to these embodiments. Unless otherwise specified, all experiments were conducted in an anaerobic glove box (maintaining dissolved oxygen concentration <0.5 mg / L) at a reaction temperature of 25°C. Vanadium in the initial water sample existed in the form of V(III) at a concentration of 1.0 mg / L (for oxidation rate testing) or 2.0 mg / L (for total removal rate testing). Oxidation rate refers to the percentage of V(III) converted to V(V). The adsorption step uniformly used 0.4 g / L of amorphous ferrohydrate-based adsorbent prepared in the same batch, with an adsorption time of 120 min. The total removal rate is the percentage of total vanadium removed from the water after the oxidation-adsorption synergistic process.

[0026] Example 1:

[0027] Add 0.8 g / L of amorphous ferrohydrate to simulated polluted water (pH = 6.0), control Eh = 250 mV, and react for 180 min.

[0028] Results: The oxidation rate of V(III) was 78%. Subsequent adsorption steps resulted in a total vanadium removal rate of 89% through the synergistic process.

[0029] Example 2:

[0030] Add 0.9 g / L of amorphous ferrohydrate to simulated polluted water (pH = 6.1), control Eh = 280 mV, and react for 180 min.

[0031] Results: The oxidation rate of V(III) was 81%. Subsequent adsorption steps resulted in a total vanadium removal rate of 91% through the synergistic process.

[0032] Example 3:

[0033] Add 1.0 g / L of amorphous ferrohydrate to simulated polluted water (pH = 6.2), control Eh = 300 mV, and react for 180 min.

[0034] Results: The oxidation rate of V(III) was 80%. Following an adsorption step, the total vanadium removal rate of the synergistic process reached 91%.

[0035] Summary: Examples 1-3 cover the most preferred technical parameter range of the present invention (pH 6.0-6.2, dosage 0.8-1.0 g / L), demonstrating excellent and stable oxidation effect (oxidation rate >78%) and synergistic repair effect (total removal rate >89%).

[0036] Example 4:

[0037] Add 0.8 g / L of amorphous ferrohydrate to simulated polluted water (initially containing 1.0 mg / L of V(IV), pH = 6.0), control Eh = 250 mV, and react for 180 min.

[0038] Results: The oxidation rate of V(IV) was 73%. This indicates that the present invention also has a highly efficient oxidation capability for V(IV).

[0039] Example 5:

[0040] Add 0.6 g / L of amorphous ferrohydrate to simulated polluted water (pH = 5.8), control Eh = 220 mV, and react for 180 min.

[0041] Results: The oxidation rate of V(III) was 70%. Following an adsorption step, the total vanadium removal rate of the synergistic process reached 85%.

[0042] Note: The parameters in this embodiment are within the preferred but not optimal range of the present invention (pH 5.5-6.5, dosage 0.5-1.5g / L), and a good remediation effect can still be obtained, but it is slightly lower than the optimal range.

[0043] Example 6:

[0044] Add 0.3 g / L of amorphous ferrohydrate to simulated polluted water (pH = 5.2), control Eh = 180 mV, and react for 180 min.

[0045] Results: The oxidation rate of V(III) was 58%. Subsequent adsorption steps resulted in a total vanadium removal rate of 75% through the synergistic process.

[0046] Note: The parameters in this embodiment are all within the basic range of the claims of this invention (pH 5.0-7.0, dosage 0.1-2.0 g / L), which can achieve the basic purpose of the invention (total removal rate >70%), proving the feasibility of the scope of the claims, but the effect is significantly less than that of the preferred range.

[0047] Comparative Example 1 (without oxidation pretreatment):

[0048] Using the same simulated polluted water body, without oxidation pretreatment, 0.4 g / L of adsorbent was directly added for adsorption.

[0049] Result: The total vanadium removal rate was only 28%.

[0050] Comparative Example 2 (Conventional Oxidant Pretreatment):

[0051] Under the same anoxic conditions, potassium persulfate with an oxidation equivalent to that in Example 1 was used to replace amorphous ferrohydrate for pretreatment, while other conditions remained the same as in Example 1. Adsorption was then performed after pretreatment.

[0052] Results: The oxidation rate was approximately 30%, and the total removal rate of the synergistic process was approximately 52%.

[0053] Comparative Example 3 (Pretreatment of other iron minerals):

[0054] Use 0.8 g / L goethite instead of amorphous ferrohydrate, and other conditions are the same as in Example 1. Adsorption is performed after pretreatment.

[0055] Results: The oxidation rate was approximately 18%, and the total vanadium removal rate of the synergistic process was approximately 40%.

[0056] Comparative Example 4 (pH out of range):

[0057] The pH of the reaction system was controlled at 4.5 (below the lower limit of this invention), and other conditions were the same as in Example 1. Adsorption was performed after pretreatment.

[0058] Results: The oxidation rate was approximately 35%, and the total vanadium removal rate of the synergistic process was approximately 60%.

[0059] Comparative Example 5 (Non-hypoxic conditions):

[0060] Under aerobic conditions (dissolved oxygen ~8 mg / L), other conditions were the same as in Example 1. Adsorption was performed after pretreatment.

[0061] Results: The oxidation rate was approximately 65%, but the V(V) content in the product was low; the total vanadium removal rate of the synergistic process was approximately 70%.

[0062] Effect Analysis:

[0063] The data from the above embodiments and comparative examples clearly demonstrate the following trends:

[0064] Within the basic parameter range defined in the claims of this invention (Example 5), effective repair (total removal rate of 75%) can be achieved.

[0065] Within the preferred parameter range of the present invention (Example 4), the repair effect is further improved (total removal rate 85%).

[0066] Within the optimal parameter range of this invention (Examples 1-3), the repair effect is optimal and stable (total removal rate 89%-92%).

[0067] Any scheme that deviates from the core features of this invention (amorphous ferrohydrate, oxygen-deficient conditions, pH 5.0-7.0) (Comparative Examples 1-5) shows a significant decrease in oxidation efficiency and final synergistic repair effect.

[0068] This fully demonstrates the effectiveness of the technical solution of the present invention, the rationality of the parameter range limitation, and its outstanding advantages and inventiveness compared with existing technologies and conventional methods.

[0069] To provide a more intuitive demonstration, the key information and synergistic repair effects of the above embodiments and comparative examples are summarized in Table 1 below.

[0070] Table 1 Summary of Results Data

[0071]

[0072] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An oxidation pretreatment system for remediating vanadium-contaminated water, characterized in that, The system operates under hypoxic or low-oxygen conditions with a dissolved oxygen concentration below 1.0 mg / L, including: (a) A dosing unit for adding amorphous ferrohydrate as an oxidant to the polluted water body; (b) A pH control unit for adjusting and maintaining the pH value of the polluted water body within the range of 5.0 to 7.0; (c) A monitoring unit for detecting the concentration of pentavalent vanadium (V(V)) in the polluted water.

2. The oxidation pretreatment system according to claim 1, characterized in that, The dosing unit is also used to add Fe(II)-organic acid complexes, wherein the organic acid is oxalic acid, citric acid or tartaric acid.

3. The oxidation pretreatment system according to claim 1 or 2, characterized in that, It also includes a redox potential control unit for adjusting the redox potential Eh of the polluted water body to a range of 150mV to 350mV (relative to a standard hydrogen electrode).

4. A method for remediating oxygen-deficient vanadium-polluted environments, characterized in that, Including the following steps performed sequentially: (i) Oxidation pretreatment step: Under the condition that the dissolved oxygen concentration is less than 1.0 mg / L, amorphous ferrohydrate is added to the polluted water containing low-valent vanadium, and the pH value of the polluted water is controlled between 5.0 and 7.0 to carry out the reaction, so that some or all of the low-valent vanadium is converted into pentavalent vanadium. (ii) Adsorption and fixation step: Add an adsorbent material with adsorption capacity for pentavalent vanadium to the water body treated in step (i) to carry out an adsorption reaction.

5. The repair method according to claim 4, characterized in that, In step (i), the dosage of the amorphous ferroalloy is 0.1 g to 2.0 g per liter of polluted water.

6. The repair method according to claim 4, characterized in that, In step (i), the redox potential Eh of the polluted water body is also controlled to be between 150 mV and 350 mV (relative to a standard hydrogen electrode).

7. The repair method according to claim 4, characterized in that, In step (i), the reaction is carried out at a temperature of 20°C to 30°C.

8. The repair method according to claim 4, characterized in that, In step (ii), the adsorbent material is a composite material with amorphous ferrohydrate as the main active component.

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