CN205966754U - Arsenic slag contaminated sites soil electronic PRB prosthetic devices - Google Patents

Abstract

An electric repair device for soil contaminated by arsenic slag site, including soil sample chamber, anode chamber, cathode chamber, DC power supply, ammeter, filter screen, pH adjustment system, electrode, overflow hole, acid solution tank, lye solution tank, collection Groove, Fe ⁰ ‑PRB; Fe ⁰ ‑PRB is set in the vertical electric field direction in the soil sample chamber, and the anode chamber and the cathode chamber are adjacent to the left and right sides of the soil sample chamber; the inner walls adjacent to the anode and cathode chambers of the soil sample chamber A filter screen is pasted on the top, and electrodes are respectively set in the middle of the anode and cathode chambers, and the two electrodes are connected by wires, with a DC power supply and an ammeter in the middle; the acid tank is connected to the cathode chamber through a rubber hose, and a pH Adjustment system; the lye tank is connected to the anode chamber through a rubber hose, and a pH adjustment system is provided in the middle; an overflow hole is provided at the upper end of the cathode chamber and the anode chamber, and the overflow hole is connected to the collection tank through a conduit. The structure is simple , strong operability and good arsenic removal effect.

Description

An electric-PRB remediation device for soil contaminated by arsenic slag

technical field

The utility model belongs to the technical field of soil pollution restoration of environmental technology, in particular to an electric restoration device for soil polluted by arsenic slag sites.

Background technique

Arsenic slag is a highly toxic solid waste, the main source of which is the discharge from the mining and smelting of arsenic-containing minerals, concentrated in Xinjiang, Inner Mongolia, Hunan Province, Guangdong Province and other places. China's arsenic mineral resources account for about 70% of the world's total. In areas where arsenic-containing mines are active, the annual output of arsenic slag is about 50 tons. A large number of idle arsenic-containing slags that have not been harmlessly treated and piled up arbitrarily have caused arsenic to enter the nearby soil Large areas of soil arsenic pollution have been caused. Soil arsenic pollution has the characteristics of concealment, long-term and irreversible. Therefore, once the soil is polluted by arsenic, its treatment is difficult and the cycle is long.

At present, the main methods for dealing with arsenic-contaminated soils include guest soil method, leaching method, solidification/stabilization method, phytoremediation method and electrokinetic remediation method. The engineering quantity of guest-soil method is large, time-consuming and labor-intensive. The leaching method and solidification/stabilization method did not completely remove the arsenic in the soil, which easily caused secondary pollution of the soil, and was not suitable for large-scale site restoration. Phytoremediation is generally time-consuming and may take decades. As an emerging in-situ repair technology, the electrokinetic repair method has the characteristics of simple operation, strong applicability, and short cycle. However, electrokinetic repair only migrates pollutants into the electrode solution and requires secondary treatment. The combined use of electrodynamic restoration technology and PRB can combine the advantages of electrodynamic and PRB technologies to improve the removal efficiency of arsenic in the soil, the restoration time is shorter, and the soil layer is not disturbed. It is suitable for low-permeability soils, and arsenic can be recovered at the same time. It can effectively reduce secondary pollution, reduce the workload of subsequent treatment, and improve economic benefits.

The current electric repair device is complex in design, not strong in practicability, and has poor removal effect on pollutants. The acid-base waste liquid generated is not recycled and reused, causing secondary pollution to the environment.

Utility model content

In order to solve the above technical problems, the utility model provides an electric-PRB combined restoration device for in-situ restoration of soil contaminated by arsenic slag sites. The device can quickly, economically, effectively, and in-situ repair the arsenic site-contaminated soil, and can recover acid-base waste liquid for recycling.

The utility model is realized through the following technical solutions:

An electric repair device for soil contaminated by arsenic slag site, including soil sample chamber, anode chamber, cathode chamber, DC power supply, ammeter, filter screen, pH adjustment system, electrode, overflow hole, acid solution tank, lye solution tank, collection Groove, Fe ⁰ -PRB; Fe ⁰ -PRB is set in the vertical direction of the electric field in the soil sample chamber, and the anode chamber and cathode chamber are adjacent to the left and right sides of the soil sample chamber; the inner walls of the soil sample chamber adjacent to the anode and cathode chambers A filter screen is pasted on the top, and electrodes are respectively set in the middle of the anode and cathode chambers, and the two electrodes are connected by wires, with a DC power supply and an ammeter in the middle; the acid tank is connected to the cathode chamber through a rubber hose, and a pH Adjustment system; the lye tank is connected to the anode chamber through a rubber hose, and a pH adjustment system is arranged in the middle; an overflow hole is provided at the upper end of the cathode chamber and the anode chamber, and the overflow hole is connected to the collection tank through a conduit.

The soil sample chamber 1 is used for filling the soil to be tested, and its size ratio is length: width: height = 3:2:1.

The soil to be tested is crushed chromium slag site and chromium-contaminated soil, sieved, mixed with acidic solution to make the moisture content of the soil 25%-45%, stirred and balanced.

The chromium slag site and the chromium-contaminated soil are preferably the soil of the arsenic slag stacking site, the soil is weakly acidic, the pH value is generally between 5-7, and the concentration of arsenic in the soil is relatively high, and the total arsenic concentration is generally 100-100000mg/ between kg.

The thickness of the Fe ⁰ -PRB is 1-5 cm, preferably 3-5 cm, most preferably 3 cm.

The dimensions of the anode chamber and the cathode chamber are length: width: height = 1:2:1.

The filter screen is 400-650 mesh, preferably 500 mesh.

The voltage gradient of the DC power supply is 1-2V/cm.

The electrodes are rod-shaped graphite electrodes, and the electrodes are respectively placed in the center of the cathode and anode chambers and inserted into the bottom of the cathode and anode chambers.

Electrolyte is added into the anode chamber, and electrolyte and strengthening reagent are added into the cathode chamber.

The electrolyte is a KCl solution with a concentration of 0.05-0.15 mol/L, preferably 0.1 mol/L.

The enhancing reagent is EDTA solution, its concentration is 0.001-0.1mol/L, preferably 0.005mol/L.

The pH adjustment system is mainly composed of a pH electrode, a peristaltic pump, and a software control system; the pH range is set, and when the pH electrode measures the pH of the anode chamber or the cathode chamber beyond the set pH range, the peristaltic pump is instructed by the software control system , the peristaltic pump collapses the configured acid or lye into the cathode chamber or anode chamber to adjust the pH. The preferred pH5 is between 5-7.

Beneficial effect

Put soil into the device of the utility model, and add Fe ⁰ -PRB in the direction of the vertical electric field in the soil sample chamber, use filter cloth to separate the soil sample chamber from the adjacent anode and cathode chambers, and connect the power system and the pH balance adjustment system . In the electric/PRB joint restoration process, a DC power supply is used to apply a stable voltage across the soil. Under the action of an external electric field, pentavalent arsenic and trivalent arsenic in the soil migrate in the form of oxygen-containing anion groups and cationic groups, respectively. into the anode chamber and cathode chamber electrolyte, and remove it by adsorption with PRB medium Fe ⁰ . Due to the complexing property of EDTA, it can react with arsenate to form a dissolved complex, which improves the mobility of arsenic, thereby significantly improving the removal rate of arsenic. During the restoration process, the pH value of the cathode and anode liquids is monitored in real time, and the pH balance adjustment system is used to add acetic acid solution and sodium hydroxide solution to the cathode and anode liquids respectively by using a peristaltic pump to adjust the electrolytes of the cathode and anode so that the pH is at Between 5 and 7, maintain weak acidity, which can effectively control the migration of OH ^- produced by cathodic electrolysis into the soil and make the soil pH more alkaline. The removal effect of the total arsenic by the use of the device reaches 40%, and the arsenic mainly exists in the residual state, and the bioavailability of the residual arsenic is reduced.

The utility model is suitable for the arsenic-polluted soil where the arsenic concentration is relatively high, and the total arsenic concentration is generally between 100-100000 mg/kg.

The overflow hole of the utility model and the collection tank connected by the overflow hole through the conduit can recycle and reuse a large amount of acid and alkali liquid, reduce the risk of secondary pollution, and achieve high efficiency and environmental protection.

Description of drawings:

Fig. 1 is a schematic structural diagram of the electric-PRB repair device of the present invention.

Among them, 1-soil sample chamber, 2-anode chamber, 3-cathode chamber, 4-DC power supply, 5-ammeter, 6-filter, 7-pH adjustment system, 8-electrode, 9-overflow hole, 10- Acid tank, 11-alkali tank, 12-collection tank, 13-Fe ⁰ -PRB

detailed description

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. example. Based on the embodiments of the present utility model, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model. The features and advantages of the present invention will be described in detail below in conjunction with the accompanying drawings.

The electric-PRB repair device of the present utility model, as shown in Figure 1, comprises: soil sample chamber 1, anode chamber 2, cathode chamber 3, DC power supply 4, ammeter 5, filter screen 6, pH adjustment system 7, electrode 8, Overflow hole 9, acid solution tank 10, lye solution tank 11, collection tank 12, Fe ⁰ -PRB 13.

Among them, the soil sample chamber 1 is used to fill the soil for testing, and its size ratio is length: width: height = 3:2:1. Add Fe ⁰ -PRB 13 to soil sample chamber 1 with a thickness of 5 cm. Adjacent to the left and right sides of the soil sample chamber 1 are the anode chamber 2 and the cathode chamber 3, and the dimensions of the anode chamber 2 and the cathode chamber 3 are length: width: height = 1:2:1. A filter screen 6 is pasted on the inner wall adjacent to the anode and cathode chambers of the soil sample chamber, electrodes 8 are respectively arranged in the middle of the anode chamber 2 and the cathode chamber 3, and the two electrodes 8 are connected by wires, and a DC power supply 4 is arranged in the middle , Ammeter 5. The electrodes 8 are rod-shaped graphite electrodes, and the electrodes 8 are respectively placed in the center of the cathode and anode chambers and inserted into the bottom of the cathode and anode chambers.

The acid solution tank 10 is connected with the cathode chamber 3 by rubber hose, and a pH adjustment system 7 is arranged in the middle, and the lye tank 11 is connected with the anode chamber 2 by a rubber hose, and the pH adjustment system 7 is arranged in the middle; There is an overflow hole 9 which is connected to a collection tank 12 by a conduit.

The pH adjustment system is mainly composed of a pH electrode, a peristaltic pump, and a software control system (the pH electrode, peristaltic pump, and software control system are not marked in Figure 1); the pH range is set, and when the pH of the anode chamber or cathode chamber measured by the pH electrode exceeds the set value When the pH range is specified, the peristaltic pump is instructed by the software control system, and the peristaltic pump will collapse the configured acid or alkali into the cathode chamber or anode chamber to adjust the pH.

Repair process:

(1) Get the naturally air-dried chromium-contaminated soil, remove foreign matter therein, use a pulverizer to pulverize, cross a standard sieve with a particle size of 0.50 mm, and set aside;

(2) Mix the above-mentioned soil to be used with deionized water at a ratio of 2:1 to make the water content 25-45%, stir well and balance for one day;

(3) Take the above-mentioned balanced soil in the soil sample chamber 1 of the electric-PRB repair device, and place a 500-mesh filter screen 6 at both ends of the soil sample chamber 1 to prevent the soil from migrating to the anode chamber 2 and cathode chamber 3 during the repair process. The cathode and anode chambers are filled with electrolyte, and the electrolyte is 0.1mol/L KCl solution, and 0.1mol/L KCl solution is added to the cathode chamber 3, and 0.005mol/L enhancement reagent EDTA solution is added at the same time.

(4) Insert the graphite electrode 8 into the middle of the cathode and anode chamber, insert it to the bottom, connect the power supply 4 and the ammeter 5, and after the repair starts, adjust the voltage gradient to 1-2V/cm, and continue until the repair is completed.

(5) During the repair process, real-time monitoring of the pH value of the anode and cathode solution, and use the pH balance adjustment system 7, use the peristaltic pump to drip the acetic acid solution in the acid solution tank 10 to the electrolyte solution of the cathode 3, and add the acetic acid solution to the electrolyte solution of the anode 2 Add dropwise the sodium hydroxide solution in the lye tank 11 to adjust the respective pH of the catholyte and the anolyte, so that each electrolyte is at 5-7 to keep weak acidity.

During the electric restoration process, the acetic acid solution and the sodium hydroxide solution must be continuously replenished, so the cathode and anode electrolytes will be discharged from the overflow hole 9, and the cathode and anode electrolytes discharged from the overflow hole 9 will be collected and stored in the collection tank 12. Unified treatment with the anode and cathode solution after electric restoration. Example 2

Use the device of embodiment 1 to remediate arsenic-contaminated soil, comprising the following steps:

Step (1) takes the arsenic-contaminated soil after natural air-drying, (wherein the total arsenic content in the soil is 447.5 mg/kg of the total arsenic content of the soil, 67.9 mg/kg of the As(III) content of the soil, and 67.9 mg/kg of the As(V) content of the soil 379.6mg/kg, pH=6.8), remove the sundries therein, pulverize with a pulverizer, sieve with a fineness of 0.50mm, and set aside;

Step (2) Mix 5 kg of the above-mentioned soil to be used with 2.5 L of deionized water, stir evenly with a stainless steel shovel, and let stand for one day;

Step (3) Take 4 kg of the above-mentioned equalized soil in the soil sample chamber of the electric/PRB joint restoration device, wherein the soil sample chamber measures 30cm×20cm×10cm, and the negative and positive electrode chambers at both ends measure 10cm×20cm×10cm. Add 500-mesh filter cloths at both ends of the chamber to prevent the soil from migrating to the cathode and anode chambers during the restoration process. Fill the cathode and anode chambers with 0.1mol/L KCl solution, and at the same time add 0.005mol/L enhanced reagent EDTA to the cathode chamber solution;

Step (4) Insert the graphite electrode into the middle of the cathode and anode chamber, insert it to the bottom, connect the DC power supply and the ammeter, and maintain the DC voltage gradient at 2V/cm until the repair is completed;

Among them, during the repair process, the pH value of the cathode and anode liquids is monitored in real time, and the pH balance adjustment system is used to use a peristaltic pump to add acetic acid solution and sodium hydroxide solution to the cathode and anode liquids respectively to adjust the pH of the cathode and anode liquids at 5-7. In between, keep slightly acidic.

Step (5) After the repaired soil sample is digested in a (1+1) aqua regia water bath, the total arsenic concentration is determined by atomic fluorescence spectrometry.

Results: After five days of test operation, the method of the present invention can remove 40% of the total arsenic, and the arsenic mainly exists in the residual state, and the bioavailability of the residual arsenic is reduced. The arsenic removal efficiency of ordinary electric restoration is significantly improved by 16%. At the same time, the energy consumption is reduced from 7.44kWh/g to 6.43kWh/g.

Claims (10)

1. a kind of electronic-PRB prosthetic device of arsenic slag contaminated soil of site, including soil sample chamber, anode chamber, cathode chamber, unidirectional current Source, ammeter, filter screen, pH regulator system, electrode, spout hole, acid storage, lye tank (vat), collecting tank, Fe⁰-PRB；Described soil sample chamber Middle vertical electric field direction arranges Fe⁰- PRB, soil sample chamber the right and left adjacent for anode chamber, cathode chamber；Soil sample chamber and positive and negative Post filter screen on the adjacent inwall of pole room, in the middle of anode, cathode chamber, be respectively equipped with electrode, two electrodes are adopted electric wire even Connect, in the middle of it, be provided with DC source, ammeter；Described acid storage is connected by sebific duct with cathode chamber, and centre is provided with pH regulator system System；Described lye tank (vat) is connected by sebific duct with anode chamber, and centre is provided with pH regulator system；Described cathode chamber and the upper end of anode chamber It is provided with spout hole, spout hole is connected to collecting tank by conduit.

2. prosthetic device as claimed in claim 1 it is characterised in that described soil sample chamber be for filling for examination soil, its Dimension scale is length：Wide：High=3：2：1；Described anode chamber, cathode chamber are a size of long：Wide：High=1：2：1.

3. prosthetic device as claimed in claim 2 is it is characterised in that described is by chromium slag place, pollution of chromium soil for examination soil Earth is pulverized, and sieves, described soil is mixed with deionized water, makes soil moisture content be 25%-45%, stirring, equalizes.

4. prosthetic device as claimed in claim 3 is it is characterised in that described chromium slag place, chromium-polluted soil are in faintly acid, , in 5-7, total arsenic concentration is in 100-100000mg/kg for pH value.

5. prosthetic device as claimed in claim 1 is it is characterised in that described Fe⁰- PRB thickness is 1-5cm.

6. prosthetic device as claimed in claim 1 is it is characterised in that described filter screen is 400-650 mesh.

7. prosthetic device as claimed in claim 1 is it is characterised in that the voltage gradient of described DC source is 1-2V/cm.

8., it is characterised in that described electrode adopts bar-shaped graphite electrode, electrode is respectively for prosthetic device as claimed in claim 1 It is placed on the anode chamber and the cathode chamber center, insert the anode chamber and the cathode chamber bottom.

9. prosthetic device as claimed in claim 1, it is characterised in that adding electrolyte in described anode chamber, adds in cathode chamber Enter electrolyte and Contrast agent, described concentration of electrolyte is 0.05-0.15mol/L, described Contrast agent concentration is 0.001- 0.1mol/L.

10. prosthetic device as claimed in claim 1 is it is characterised in that described pH regulator system is mainly by pH electrode, wriggling Pump, software control system composition；Set pH scope, when pH electrode records anode chamber or cathode chamber pH exceedes the pH scope of setting When, instructed to peristaltic pump by software control system, the acid solution of configuration or alkali liquor are pumped into cathode chamber or anode chamber by peristaltic pump, from And adjust pH.