阅读说明：本技术 一种适用于高浓度砷锑复合污染土壤的淋洗药剂及其制备和应用 (Leaching agent suitable for high-concentration arsenic-antimony composite polluted soil and preparation and application thereof ) 是由 崔长征 赵建锋 丁雷 吴劲松 罗启仕 傅展宇 金嘉路 张峰 林匡飞 于 2021-08-06 设计创作，主要内容包括：本发明涉及一种适用于高浓度砷锑复合污染土壤的淋洗药剂及其制备和应用,土壤淋洗药剂为草酸和柠檬酸复配而成。本发明提供的淋洗剂能够同时高效去除污染土壤中的砷和锑,且相较于单独使用草酸和柠檬酸在达到淋洗阈值的情况下,仍然能够进一步将污染土壤中的砷和锑洗脱下来。此外,提供的淋洗剂组分简单,均为有机弱酸,对土壤的破坏作用小,有利于后续淋洗废液的回收利用,所选试剂具有价格低廉、环境友好、安全性可靠的特点,尤其适用于有色金属冶炼过程中由伴生矿带来的高浓度砷锑复合污染土壤。(The invention relates to a leaching agent suitable for high-concentration arsenic-antimony composite polluted soil, and preparation and application thereof. The eluting agent provided by the invention can simultaneously and efficiently remove arsenic and antimony in the polluted soil, and can still further elute the arsenic and antimony in the polluted soil compared with the condition that oxalic acid and citric acid are independently used and the eluting threshold is reached. In addition, the provided eluting agent has simple components, is organic weak acid, has small destructive effect on soil, is beneficial to recycling of subsequent eluting waste liquid, has the characteristics of low price, environmental friendliness and reliable safety, and is particularly suitable for high-concentration arsenic-antimony composite polluted soil caused by associated ores in the non-ferrous metal smelting process.)

1. The leaching agent suitable for the high-concentration arsenic-antimony composite polluted soil is characterized by being a compound leaching agent containing oxalic acid and citric acid.

2. The leaching agent suitable for the high-concentration arsenic-antimony composite polluted soil according to claim 1, wherein the concentration of oxalic acid in the compound leaching agent is 0.01-1.00 mol/L.

3. The leaching agent suitable for the high-concentration arsenic-antimony composite polluted soil according to claim 1, wherein the compound leaching agent is 0.20-0.50 mol/L.

4. The leaching agent suitable for the high-concentration arsenic-antimony composite polluted soil according to claim 1, wherein the concentration of citric acid in the compound leaching agent is 0.01-1.00 mol/L.

5. The leaching agent suitable for the high-concentration arsenic-antimony composite polluted soil according to claim 1, wherein the concentration of citric acid in the compound leaching agent is 0.20-0.50 mol/L.

6. The method for preparing the leaching agent suitable for the high-concentration arsenic-antimony composite polluted soil as claimed in any one of claims 1-5, wherein the leaching agent is obtained by mixing an oxalic acid solution and a citric acid solution.

7. The application of the leaching agent suitable for the high-concentration arsenic-antimony composite polluted soil as claimed in any one of claims 1 to 5, wherein the leaching agent is used for leaching and repairing the high-concentration arsenic-antimony composite polluted soil.

8. The application of the leaching agent suitable for the high-concentration arsenic-antimony composite polluted soil according to claim 7, wherein when the leaching agent is used for leaching and repairing the polluted soil, the specific repairing process is as follows:

firstly, crushing and sieving the polluted soil to be repaired, then adding the crushed and sieved polluted soil and the compound leaching agent into a centrifugal tube for mixing, leaching by using a vortex oscillator, then centrifuging, and collecting to obtain a solid phase part, namely the repaired soil.

9. The application of the leaching agent suitable for the high-concentration arsenic-antimony composite polluted soil according to claim 8 is characterized in that the addition amount of the polluted soil to be repaired and the compound leaching agent meets the following requirements: the solid-liquid ratio is 1 g: (5-20) mL.

10. The application of the leaching agent suitable for the high-concentration arsenic-antimony composite polluted soil according to claim 8, wherein the leaching time is 1-4 h.

Technical Field

The invention belongs to the technical field of site contaminated soil remediation, and relates to a leaching agent suitable for high-concentration arsenic-antimony composite contaminated soil, and preparation and application thereof.

Background

Arsenic (As) and antimony (Sb) contamination in soil is often present in non-ferrous metal mining and smelting activities, 3900 national nonferrous smelting companies, and 1301 lead and zinc smelting companies. The nonferrous smelting ore is usually associated ore or paragenic ore, and contains high concentrations of As and Sb, resulting in composite soil pollution. As and Sb in soil have strong migration, are easy to cause groundwater pollution, and also can cause health risks to human beings through food chains, so that the content of As and Sb in the soil environment must be controlled.

The soil leaching technology is to transfer heavy metals from a soil medium to a water phase medium by utilizing the interaction between a leaching agent and the heavy metals, and then thoroughly remove the heavy metals in the soil through solid-liquid separation, and is particularly suitable for high-concentration composite heavy metal contaminated soil. Compared with the solidification/stabilization technology, the leaching method can effectively avoid the risk of re-leaching of heavy metals. Compared with the plant restoration technology, the leaching method can quickly restore the soil polluted by heavy metals with different concentrations, and is less influenced by environmental factors.

As and Sb in soil have various forms and mainly comprise two main types of organic and inorganic arsenic, wherein the inorganic arsenic comprises arsenite (III), arsenate (V) and the like, the toxicity difference of arsenic and antimony in various valence states and forms is large, and the toxicity sequence is trivalent arsenic, pentavalent arsenic, trivalent antimony, pentavalent antimony and organic antimony. The Chinese patent application document CN 104190698A discloses a method for preparing viscous soil in a high-load metal-polluted site, which comprises three steps of soil modification, leaching, solidification and the like, and the aim of rapid development and utilization is difficult to achieve.

In addition, the chinese patent application CN 112122325 a discloses a preparation method and application of an arsenic-contaminated soil eluting agent, but arsenic and antimony often accompany or complex in the same mineral, and most of the arsenic and antimony are high-concentration contaminated soil in the mining area and the smelting area, and the eluting efficiency of 50% obviously cannot meet the technical requirements. Therefore, an eluting agent applied to high-concentration arsenic-antimony composite polluted soil is urgently needed to deal with the high-concentration soil pollution caused after the decommissioning of mining areas and smelting fields in the south and the south of China.

Disclosure of Invention

The invention aims to provide a leaching agent suitable for high-concentration arsenic-antimony composite polluted soil, and preparation and application thereof, so that the removal efficiency of total arsenic and total antimony in the soil is improved, and the national relevant standard value and the like are reached.

The purpose of the invention can be realized by the following technical scheme:

one of the technical schemes of the invention provides a leaching agent suitable for high-concentration arsenic-antimony composite polluted soil, which is a compound leaching agent containing oxalic acid and citric acid.

Furthermore, in the compound leaching agent, the concentration of oxalic acid can be selected to be 0.01-1.00 mol/L, and further can be selected to be 0.20-0.50 mol/L.

Furthermore, in the compound leaching agent, the concentration of citric acid can be selected to be 0.01-1.00 mol/L, and further can be selected to be 0.20-0.50 mol/L.

The second technical scheme of the invention provides a preparation method of the leaching agent suitable for the high-concentration arsenic-antimony composite polluted soil, and the oxalic acid solution and the citric acid solution are mixed. Thus obtaining the product.

The third technical scheme of the invention provides application of the leaching agent suitable for the high-concentration arsenic-antimony composite polluted soil, and is characterized in that the leaching agent is used for leaching and repairing the high-concentration arsenic-antimony composite polluted soil.

Further, when the leaching agent is used for leaching and repairing the polluted soil, the specific repairing process is as follows:

firstly, crushing and sieving the polluted soil to be repaired, then adding the crushed and sieved polluted soil and the compound leaching agent into a centrifugal tube for mixing, leaching by using a vortex oscillator, then centrifuging, and collecting to obtain a solid phase part, namely the repaired soil.

Furthermore, the addition amount of the contaminated soil to be repaired and the compound leaching agent meets the following requirements: the solid-liquid ratio is 1 g: (5-20) mL, preferably 1 g: (8-15) mL.

Furthermore, the leaching time is 1-4h, preferably 2-3 h. Meanwhile, in the leaching process, the rotation speed is controlled to be 400-600rpm, preferably 500 rpm.

Compared with the prior art, the eluting agent provided by the invention can simultaneously and efficiently remove arsenic and antimony in the polluted soil, and can still further elute the arsenic and antimony in the polluted soil compared with the condition that oxalic acid and citric acid are used independently to reach an eluting threshold. The leaching agent provided by the invention has simple components, is organic weak acid, has small destructive effect on soil, is beneficial to recycling subsequent leaching waste liquid, has the characteristics of low price, environmental friendliness and reliable safety, and is particularly suitable for high-concentration arsenic-antimony composite polluted soil caused by associated ores in the non-ferrous metal smelting process.

Drawings

FIG. 1 shows different concentrations of OA, CA, KH₂PO₄Leaching effect on arsenic;

FIG. 2 shows H at different concentrations₃PO₄EDTA and NaOH have the leaching effect on arsenic;

FIG. 3 shows different concentrations of OA, CA, KH₂PO₄Leaching effect on antimony;

FIG. 4 shows H at different concentrations₃PO₄EDTA and NaOH have the leaching effect on antimony;

FIG. 5 shows the arsenic morphological distribution before and after leaching with leachants of different concentrations;

FIG. 6 is a graph showing the morphological distribution of antimony before and after elution with eluents of different concentrations.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

In the following examples, unless otherwise specified, all the conventional commercially available raw materials or conventional processing techniques in the art are indicated.

Example 1:

the sample is taken from soil to be restored in a certain lead-zinc smelting plant in Hunan province, is naturally dried, is sieved by a nylon sieve with the particle size of 2mm (10 meshes), is uniformly mixed and is placed in a cool and dry place for later use. The measured total arsenic and total antimony contents in the soil sample respectively reach 18900-22000 mg/kg and 3865-3960 mg/kg, which are far beyond the control value arsenic (140 mg-kg) of soil pollution risk of building site in the second type of soil pollution risk control value in the soil environmental quality building site soil pollution risk control Standard (trial) (GB36600-2018) Standard^-1) And antimony (360mg kg)^-1). The basic physical and chemical properties and heavy metal content of the soil are shown in table 1.

TABLE 1 basic physicochemical properties of soil and heavy metal content

pH

Water content ratio

Clay (%)

Powder (%)

Sand (%)

Arsenic (mg/kg)

Antimony (mg/kg)

11.56

15.27％

27～30％

40～51％

22～30％

19800～22600

3865～3960

Weighing 50g of sieved soil, placing the sieved soil in a 1L conical flask, adding 500mL of compound eluent (0.2mol/L of citric acid: 20% by volume, namely the volume of the added citric acid is 100mL, and 1.0mol/L of oxalic acid: 80% by volume, namely the volume of the added oxalic acid is 400mL), namely the liquid-solid ratio is 10mL:1g, placing the mixture in a vortex oscillator, oscillating for 2h under the condition of 500r/min, pouring part of the eluent into a 50mL centrifugal tube, centrifuging at 4000rpm for 15min, collecting supernatant, and determining the concentrations of arsenic and antimony in the eluent.

The washed soil is the clean soil which reaches the standard.

The arsenic and antimony concentrations in the leacheate and the leaching effect are shown in Table 2.

TABLE 2 arsenic and antimony concentrations in leacheate and Leaching Effect

Heavy metals	Concentration of leacheate (mg/L)	Elution efficiency (%)
			Arsenic (As)	212	96.36
Antimony (Sb)	31.9	80.56

Different concentrations of OA, CA and KH₂PO₄The leaching effect on arsenic is shown in fig. 1. Different concentrations of H₃PO₄The leaching effect of EDTA and NaOH on arsenic is shown in FIG. 2. As can be seen from the figure, under the conditions that the solid-liquid ratio is 1:10 and the leaching time is 2H, the leaching efficiency of the six leaching agents on arsenic is continuously increased along with the increase of the concentration, and OA, CA and H₃PO₄、KH₂PO₄The optimal elution efficiency for As, EDTA and NaOH were 94.44%, 90.48%, 95.43%, 95.43%, 92.21% and 83.07%, respectively. The results show that OA, CA and KH have the maximum arsenic leaching efficiency of 83.07% except NaOH₂PO₄、H₃PO₄And EDTA are all more than 90%, and the maximum leaching efficiency is as follows from high to low: h₃PO₄＞KH₂PO₄＞OA＞EDTA＞CA＞NaOH。

Oxalic Acid (OA), Citric Acid (CA), and potassium dihydrogen phosphate (KH) at different concentrations₂PO₄) The leaching effect on antimony is shown in fig. 3. Phosphoric acid (H) of various concentrations₃PO₄) The leaching effects of Ethylene Diamine Tetraacetic Acid (EDTA) and sodium hydroxide (NaOH) on antimony are shown in fig. 4, respectively. Wherein OA, CA, H₃PO₄、KH₂PO₄The optimal elution efficiency for Sb, EDTA and NaOH were 78.24%, 51.14%, 65.20%, 5.91%, 3.23% and 2.16%, respectively. Wherein, KH₂PO₄The optimal leaching efficiency of EDTA and NaOH on Sb is less than 10%. Different concentrations of OA, CA and H under the conditions of solid-to-liquid ratio of 1:10 and leaching time of 2H₃PO₄Along with the increase of the concentration, the leaching efficiency of antimony is continuously increased; however, KH₂PO₄The elution efficiency of EDTA and NaOH is firstly reduced and then increased along with the increase of the concentration of the eluting agent, and the elution efficiency of the EDTA and the NaOH are maintained at a low level.

As shown in fig. 5, is divided intoRespectively corresponding to 0.2mol/L Citric Acid (CA), 0.2mol/L Ethylene Diamine Tetraacetic Acid (EDTA) and 0.2mol/L potassium dihydrogen phosphate (KH)₂PO₄) 0.2mol/L Oxalic Acid (OA), 1.0mol/L phosphoric acid (H)₃PO₄) And performing arsenic morphological analysis on the soil after 1.0mol/L sodium hydroxide (NaOH) washing. Compared with the original soil, after the eluting agent with different concentrations is used for eluting, the different form removal proportions of arsenic in the soil are as follows from large to small: the residue state > carbonate bonding state > ferromanganese oxide bonding state > organic bonding state > ion exchange state. Wherein, the leaching amounts of oxalic acid to arsenic in an ion exchange state, a carbonate combined state, a ferro-manganese oxide combined state, an organic matter combined state and a residue state are 1083mg/kg, 4142mg/kg, 3244mg/kg, 1076mg/kg and 8718mg/kg respectively. The leaching amounts of citric acid on arsenic in an ion exchange state, a carbonate combined state, a ferro-manganese oxide combined state, an organic matter combined state and a residue state are 963mg/kg, 4136mg/kg, 3625mg/kg, 1155mg/kg and 8734mg/kg respectively. Cao et al performed morphological analyses of the soil before and after 0.1mol/L oxalic acid leaching and found that about half of the arsenic in the ferrimanganic oxide bound state was due to dissolution of mineral oxides. Kim et al, by performing leaching studies on mine soils at concentrations of 100330mg/kg, believe that oxalate acts primarily on arsenic in the soil in an amorphous iron oxide-binding state.

As shown in FIG. 6, 0.2mol/L Citric Acid (CA), 0.2mol/L ethylenediaminetetraacetic acid (EDTA), and 0.2mol/L potassium dihydrogen phosphate (KH)₂PO₄) 0.2mol/L Oxalic Acid (OA), 1.0mol/L phosphoric acid (H)₃PO₄) And morphological analysis of antimony in the soil after 1.0mol/L sodium hydroxide (NaOH) washing. Compared with the original soil, the residual antimony components and the organic matter combined components in the soil are reduced after leaching, wherein the leaching amount of the residual antimony components is as follows from high to low: h₃PO₄、OA、CA、EDTA、KH₂PO₄And NaOH, wherein the leaching amount of the organic matter in the combined state is as follows from high to low: h₃PO₄CA, EDTA, NaOH, OA and KH₂PO₄. Li and other researches find that the migration and bioavailability of Sb can be reduced after the soil is washed by oxalate, probably because the oxalate is easy to generate calcium oxalate with alkaline earth metals (such as calcium, barium and the like) and the like to be coated on soil particlesThe surface of the pellet.

By means of the pairs OA, CA and H₃PO₄、KH₂PO₄And the leaching effects of EDTA and NaOH on arsenic and antimony in the soil are compared, and the fact that the two organic weak acid oxalic acid and citric acid can simultaneously leach high-concentration arsenic and antimony in the polluted soil is found. According to the method, oxalic acid and citric acid with certain concentrations are compounded, and compared with the condition that oxalic acid and citric acid are used independently and reach a leaching threshold value, the leaching efficiency of arsenic and antimony in the polluted soil is improved by 1.92% and 2.32% respectively, and the high-concentration arsenic and antimony polluted soil can be leached.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.