CN103521513A - Leaching method of soil polluted by hexavalent chromium - Google Patents
Leaching method of soil polluted by hexavalent chromium Download PDFInfo
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Abstract
The invention discloses a leaching method of soil polluted by hexavalent chromium. The leaching method comprises the following steps: stirring 0.21-0.82 mol/L hydrochloric acid and polluted soil according to the mass ratio of 5:1 to 10:1, standing, then extracting supernatant liquor, adding a reducing agent (iron powder or sodium pyrosulfite or a mixture of the iron powder and the sodium pyrosulfite in any ratio) into the supernatant liquor under an acidic condition with the adding amount being 59-68g per kg of soil, reducing the hexavalent chromium in leacheate into trivalent chromium, and adding solid alkali to precipitate out the trivalent chromium so as to realize separation. The leaching method disclosed by the invention has the advantages that the removal rate of hexavalent chromium approaches to 90%; the following treatment of wastewater is simple and fast, and the removal of chromium ions is complete; the whole remediation process is low in cost and high in removal rate and the leaching method is an ideal remediation means of soil polluted by the hexavalent chromium, especially soil polluted by alkaline or strongly-alkaline chromium; therefore, the leaching method provides good demonstration for ex-situ remediation of soil polluted by heavy metals.
Description
Technical field
The present invention relates to a kind of chemical leaching repairing method of heavy-metal contaminated soil, relate in particular to the chemical leaching repairing method of hexavalent chromium polluted soil.
Background technology
After heavy-metal contaminated soil, it can not be decomposed by edaphon, easily in soil, accumulates, and can be bioaccumulation.The soil of heavy metal pollution is by food chain energy serious harm health.Thereby it is very important that the reparation of heavy-metal contaminated soil seems.The reparation of heavy-metal contaminated soil generally includes physics, chemistry and biological renovation method.Method has chemistry reparation and phytoremediation etc. the most thoroughly.Wherein chemical leaching is important reparation means during chemistry is repaired.
In recent years, people have invented the method for various restoration of soil polluted by heavy metal.Patent CN102389893A utilizes the lead in calcium nitrate and potassium dihydrogen phosphate stable soil.Patent CN103056158A utilizes ferrum sulfuricum oxydatum solutum Continuous leaching and fluorocarbon surfactant and water wash heavy-metal contaminated soil, and in soil, Cd clearance reaches more than 90%.Patent CN102500612A utilizes Na
2eDTA solution drip washing heavy-metal contaminated soil, effectively removes soil available Cd and lead.Patent CN102380506A has provided plantation bluish dogbane can make heavy-metal contaminated soil reach the method for reclaiming.
That Cr VI has is carcinogenic, teratogenesis and mutagenic effect, thereby the reparation of hexavalent chromium polluted soil is very important to human health, has had the technology of a lot of reparation chromium-polluted soils at present.Patent documentation CN1810397 adopts plant and sewage purification effect to combine and Cr VI in soil is migrated in plant or be transferred in the water in filter layer pond, and the physiological action by lawn, seeding corn and other crops finally makes the Cr VI in the water of filter layer pond be transferred in plant.The method mainly utilizes plant to absorb the chromium in soil, and long based on the plant growth cycle, repairing effect is slow, and the plant of absorption chromium also needs subsequent treatment.Patent CN102247980A employing citric acid and pyrolusite mixture are as the eluent of chromium-polluted soil, and the percentage by weight of citric acid and pyrolusite is respectively 95 – 99% and 1% – 5%.According to our experimental result, citric acid has severe jamming in precipitate reduction process after Cr VI, is unfavorable for removing chromium.It is trivalent chromium by hexavalent chrome reduction that patent CN102228901A adds divalent iron salt solution in chromium-polluted soil, then lime solution is injected to soil is chromium hydroxide precipitation by trivalent chromium conversion.The shortcoming of this in-situ solidifying/stabilisation restorative procedure is that Chromium in Soil still rests in soil, although Cr VI is reduced to trivalent chromium, under natural endowment, likely again trivalent chromium is oxidized to sexavalence, thereby has risk.In addition, the method is introduced a large amount of iron in soil, can bring secondary pollution.Patent documentation CN102652956A proposes a kind of original position drip washing processing method, and water is sprinkled upon to contaminated soil surface, then the water that surface is permeated to drip washing from underground water extraction well is extracted into surface and processes.The drawback of the method is the drip washing poor effect of water to chromium, if improve drip washing effect, can only increase drip washing number of times, can increase wastewater treatment capacity like this.Patent documentation CN102357522A adopts multiple polar electric pole electrical means to repair chromium-polluted soil, although the method to chromic clearance up to 84.1 – 89.6%, the method need to continue to switch on more than 120h, thereby energy consumption is large, cost is high.
Summary of the invention
The technical problem solving: the deficiency existing in order to solve current existing recovery technique, the effective removal of realization to chromium in Polluted Soil, we provide a kind of ELUTION METHOD of hexavalent chromium polluted soil, the heavy metals such as chromium can be fully transferred in water, by processing such as reduction, precipitations, the complete separating treatment of chromium out also can be collected.
Technical scheme: a kind of ELUTION METHOD of hexavalent chromium polluted soil, by the hydrochloric acid of 0.21 – 0.82mol/L and contaminated soil, according to mass ratio, be that 5:1 – 10:1 stirs, standing rear extraction supernatant, supernatant is added under acid condition to reducing agent iron powder or sodium pyrosulfite or its two mixture, addition is every kg soil 59 – 68g, by hexavalent chrome reduction in leacheate, be trivalent chromium, add solid base that trivalent chromium is precipitated out, realize separated.
Described drip washing is crossed respectively 6mm and 2mm screen cloth with Polluted Soil and is obtained.
Described mixing time is 3 – 6h.
The pH reducing under described acid condition is 0.9 – 3.
Described precipitation solid base is calcium hydroxide.
The described solid base precipitation trivalent chromium that adds, pH is adjusted to 9～10 and is terminal.
A kind of ELUTION METHOD of hexavalent chromium polluted soil, the key step comprising has drip washing stirring, Separation of Solid and Liquid, hexavalent chrome reduction and precipitation and precipitation to remove, described drip washing is stirred the equipment using and is comprised agitator tank, the first motor, the first agitator and the first screw pump, described the first motor frame is connected in agitator tank top and with the first agitator, the first screw pump import is connected with the through hole that agitator tank top is provided with by pipeline, pipeline stretches in tank body, and the first screw pump outlet is connected with the through hole that agitator tank bottom is provided with; The equipment that Separation of Solid and Liquid is used comprises the second screw pump and plastic storage tank, and the second screw pump is connected with stirring tank interior by pipeline, extracts solution and enters plastic storage tank; The equipment that hexavalent chrome reduction and precipitation are used comprises plastic storage tank, the second agitator and doser, in described plastic storage tank, by doser, adds medicament, and the second agitator stirs the solution in plastic storage tank; Precipitation is removed the equipment using and is comprised plastic storage tank, three screw pump, filter press, the second motor and cistern, the second motor is located at one end of filter press, cistern is located at the below of filter press, described three screw pump will pump into filter press away from one end of the second motor containing floccule solution after plastic storage tank reaction, and filter liquor enters cistern; By the hydrochloric acid of 0.21 – 0.82mol/L and contaminated soil, according to mass ratio, be that 5:1 – 10:1 stirs, standing rear extraction supernatant, supernatant is added under acid condition reducing agent iron powder or sodium pyrosulfite or its two arbitrarily than mixture, addition is every kg soil 59 – 68g, by hexavalent chrome reduction in leacheate, it is trivalent chromium, add solid base that trivalent chromium is precipitated out, realize separated.
Beneficial effect: sample and working sample is learnt by test, leacheate watery hydrochloric acid concentration is that 0.21mol/L, 5:1 soil ratio stir under the condition of 3 hours, and in soil, hexavalent chromium removal rate is maximum.This phenomenon does not also meet people's routine and thinks that eluent concentration is larger, soil ratio is higher, the rule that drip washing effect is better.After above-mentioned condition drip washing, then add the water of equivalent to stir for the second time the same time, total clearance can reach 88% – 91%.In follow-up water treatment procedure, select sodium pyrosulfite as reducing agent, compare with iron powder, Reaction time shorten, can also reduce reducing agent consumption in a large number, reduces costs.Because iron powder to chromic reduction mechanism is: iron first generates ferrous ion with hydrochloric acid reaction, and ferrous ion is trivalent chromium by hexavalent chrome reduction again under acid condition.Under pilot plant conditions, iron powder and hydrochloric acid reaction also need time a couple of days by hexavalent chrome reduction.And compare with sodium pyrosulfite, the reducing power of ferrous ion a little less than, need to be under very low pH competence exertion reduction, thereby can consume a large amount of hydrochloric acid.So result of the test recommend adoption sodium pyrosulfite is as reducing agent.
Precipitation process selects calcium hydroxide as precipitating reagent, and benefit is that excessive calcium hydroxide can not dissolve established sediment as chromium hydroxide etc., does not worry that the excessive dissolved hydrogen chromium oxide of highly basic discharges the side effect of chromium in water.
Accompanying drawing explanation
Fig. 1 is that schematic diagram is stirred in drip washing;
Fig. 2 is Separation of Solid and Liquid schematic diagram;
Fig. 3 is leacheate precipitate reduction schematic diagram;
Fig. 4 is sedimentation and filtration schematic diagram.
Agitator tank in figure (1), the first motor (2), the first agitator (3), the first screw pump (4), the second screw pump (5), plastic storage tank (6), the second agitator (7), doser (8), three screw pump (9), filter press (10), the second motor (11), cistern (12).
The specific embodiment
With pilot plant test, the present invention will be further described below.
It is extremely serious that test site is positioned at the topsoil pollution of chromium of chemical plant, Hangzhou ，Gai plant area of old site plant area, and surface also has chromium slag residual, fluffy, is mustiness, yellow or yellow green.This test be take on-site remained on surface chromium slag and is originated as main Polluted Soil.Collect place inner surface chromium slag and topsoil, cross the stainless steel sift of 6.0mm, if the soil sieving has compared with large clod, with mallet, break into pieces, after the stainless steel sift of 2.0mm.All soil of crossing 2.0mm stainless steel sift is flocked together and mixed thoroughly, standby.
With self-priming chemical pump by two barrels of 60kg(, every barrel of 30kg) in the hydrochloric acid and 1380kg clear water suction agitator tank of 36%wt technical grade.Start and stir elution device (comprise agitating device and fluid circulating device, EGR is mainly comprised of screw pump), start to stir, preparation obtains the about 1440L of hydrochloric acid solution of 0.41mol/L.Now, the first agitator Stirring, rotating speed is 50rpm, and circulation screw pump makes in agitator tank solution from extracting out above, then is pressed into from agitator tank small hole at bottom part, on playing a part, turns over solution, and whole process makes in agitator tank solution in rolling state.Utilize conveyer to send in agitator tank in weighing 144kg soil.Start timing, continuous stirring 3h.Stop stirring, standing sedimentation, extracts supernatant to be placed in plastic storage tank out with self-priming chemical pump.Continuation adds 1380kg clear water, continuous stirring 3h in agitator tank.Stop stirring standing sedimentation.Supernatant is extracted out and is mixed in above-mentioned storage tank, stir.
The soil of agitator tank bottom drip washing is slowly emitted from bottom discharge mouth, add the water suction of 75kg calcium oxide, stir, be transported to fixed position and deposit.
Hydrochloric acid to adding 44.52kg36%wt technical grade in the leacheate of extracting out, is adjusted to 0.9 by pH value of solution, adds 9.19kg100 order iron powder, stirs, fully reaction.Treat that solution becomes blackish green, add wherein 21.16kg technical grade calcium hydroxide, pH value of solution is adjusted to 9.21, flocculent deposit is obvious.Start filter-press arrangement (comprising filter press and screw pump), sediment solution is pressed into Filter Press, after filtering, solution is as clear as crystal.
Whipping process is divided into twice, uses for the first time hydrochloric acid stirring, water and soil mass ratio 10:1, the stirring 3h of 0.41mol/L; For the second time with clear water stirring, water and soil mass ratio 10:1, stirring 3h.In twice extraction supernatant process, take respectively water sample, in emitting lessive process, take soil sample.Before leacheate reduction, with in salt acid for adjusting pH process, intermittence adds hydrochloric acid, after stirring, with portable pH meter, measures pH, until pH reaches 0.9, then adds reducing agent iron powder.Should be standing after adding reducing agent to stir, allow it fully react.Because laboratory experiment demonstration, adds in iron powder reducing process, the H2 of generation also can participate in reduction reaction, thereby continues to stir reacting unfavorable.In field pilot test process, because material handling amount is larger, the H2 of generation is a lot, and H2 can not rest in solution, all can run out, thereby reaction is slower, lasts and reaches a couple of days.In adding calcium hydroxide precipitation process, intermittence adds a small amount of calcium hydroxide, stirs, with portable pH meter, measure pH, when reaching 8.5 left and right Shi Ying, stop adding, question response is abundant, pH value can reach 9 left and right, and this pH value is the best pH of trivalent chromium precipitation just.
Soil is in drip washing whipping process, and powder proportion is less, thereby can flow together along with solution, thereby after stopping stirring, powder can be deposited on agitator tank marginal position, and sand grains can be gathered in agitator tank centre position.Cause sand grains and powder skewness, thereby take respectively sand grains and powder pedotheque.By the soil sample air-dry of adopting back, ground 10 mesh sieves, then get and cross in right amount 100 mesh sieves, 100 order samples are dried to 2h for analytical test in 105 ℃ of baking ovens.Total chromium content in soil adopts HF-HNO
3-HClO
4-atomic absorption spectrophotometry is measured; In soil, Cr VI adopts clear up-diphenylcarbazide of alkali determined by ultraviolet spectrophotometry; The total chromium of water sample adopts atomic absorption spectrophotometry or inductively coupled plasma emission spectrographic determination; Water sample Cr VI adopts diphenylcarbazide determined by ultraviolet spectrophotometry.In each pedotheque, content of 6-valence Cr ions is in Table 1.Measurement result demonstration, after drip washing, in sand grains and powder, content of 6-valence Cr ions is suitable.This may be due at the bottom of after stirring for the first time, sand grains and powder are deposited on tank, and water filling is for the second time when again stir, the sand grains that proportion is larger is difficult for being stirred or stirring less, and powder proportion is less, be easy to just can enter in water, thereby reach abundant stirring, thereby compare with sand grains, in powder, Cr VI is leached more abundant.
Table 1 embodiment 1 test pedotheque determination of hexavalent chromium content
According to measurement result, calculate hexavalent chromium removal effect in soil, in Table 2.In process of the test, in the middle of twice drip washing, the period is not taked pedotheque, thereby the hexavalent chromium removal effect of the sand grains soil sample that directly utilization is finally taked and powder soil sample hexavalent chromium removal rate sign soil.
Hexavalent chromium removal rate in table 2 embodiment 1 Soil Under Conditions
Test site and soil source are with embodiment 1.By tetra-barrels of 120kg(, every barrel of 30kg) technical hydrochloric acid of 36%wt and 1320kg clear water be with in self-priming chemical pump suction agitator tank.Start and stir elution device, make solution start to stir, preparation obtains the dilute hydrochloric acid solution of 0.82mol/L.Do not stopping under stirring, by conveyer, the 288kg Polluted Soil of mistake 2.0mm is being sent in agitator tank.Start timing, continue to stir 6h.Standing sedimentation, extracts supernatant to deposit white storage tank in out by self-priming chemical pump.
The soil of drip washing is slowly emitted by the discharging opening of agitator tank bottom, add the water suction of 125kg calcium oxide, after mixing thoroughly, be carried to locality and deposit.
Technical hydrochloric acid to adding 33.52kg36% in the leacheate of extracting out, is adjusted to 0.91 by pH, adds 9.98kg100 object iron powder, and fully reaction, last a couple of days, but solution is still faint yellow.Continue to add 12.7kg hydrochloric acid, pH is adjusted to 2.0, in solution, adds 7.0kg sodium pyrosulfite, stir, and fully reaction, solution becomes blackish green very soon.Add 25.98kg technical grade calcium hydroxide, pH is regulated to 9.1, precipitation obviously.Start filter-press arrangement, precipitation solution is filtered, obtain as clear as crystal clear water.
In process, first use 100 order iron powders as reducing agent, but requiring reduction system pH to arrive 0.9 just can change, and in process, constantly add hydrochloric acid and iron powder to guarantee low acidity environment and sufficient reducing agent, but can find out from embodiment 1, course of reaction is quite long, can reach a couple of days, reduction efficiency is low.For this reason, we change reducing agent, use sodium pyrosulfite as reducing agent, to the not reduction of system continuation thoroughly of reduction reaction.When system pH being adjusted to 2 and add after 7.0kg sodium pyrosulfite, (approximately 15min) can see great variety at short notice, and solution becomes blackish green at once, shows that reduction completely.In system, contain the complete ferrous ion of unreacted, and the trivalent chromic ion of blueness mixes originally, has other impurity etc. in adding system, solution presents blackish green.
Sample analysis method is with embodiment 1, and pedotheque content of 6-valence Cr ions measurement result is listed in table 3.Result demonstration, in the sand grains of drip washing, content of 6-valence Cr ions is than few 2000mg/kg left and right in powder, and this is due to the easy drip washing of sand, thereby more easily removes Cr VI.
Table 3 embodiment 2 test pedotheque determination of hexavalent chromium content
Through calculating chromic removal effect in soil, in Table 4.Result demonstration, this is tested hexavalent chromium removal rate and than upper batch, tests low 10 – 20%.As can be seen here, clear water drip washing for the second time improves to total clearance.Utilize solution phase determination data to calculate known, clearance is in 12% left and right for the second time.In process of the test, solid-liquid separation step is directly emitted solid material after extracting supernatant.Can cause like this containing in soil a certain amount of leacheate, the Cr VI in the middle of leacheate etc. residues in soil, make in soil that woods washed content of 6-valence Cr ions higher, thereby clearance is on the low side.
Hexavalent chromium removal rate in table 4 embodiment 2 Soil Under Conditions
Test site and soil source are with embodiment 1 and 2.With self-priming chemical pump by 105kg(tri-and half) in the technical hydrochloric acid and 1155kg clear water suction agitator tank of 36%wt.Start and stir elution device, make solution start to stir, obtain the dilute hydrochloric acid solution of 0.82mol/L.Do not stopping under stirring, the Polluted Soil of 126kg being crossed to 2.0mm by conveyer is sent in agitator tank.Start timing, continue to stir 6h.Stop stirring, standing sedimentation, is extracted out supernatant deposit white storage tank in by self-priming chemical pump, pending.
The soil that woods was washed is slowly emitted by the discharging opening of agitator tank bottom, adds the water suction of 100kg calcium oxide, is carried to locality and deposits after mixing thoroughly.
To extracting the technical hydrochloric acid that adds 21.38kg36%wt in leacheate out, pH value of solution is adjusted to 0.9, add 5.44kg100 object iron powder, stir, fully reaction, timing agitation, lasted about three days, but solution is still with yellow.Add 13.48kg hydrochloric acid, pH value of solution is adjusted to 2.04, add 4.0kg sodium pyrosulfite, stir, fully reaction, solution becomes blackish green very soon.After 20 minutes, add 18.14kg technical grade calcium hydroxide, pH value of solution is regulated to 8.45, precipitation obviously.Start filter-press arrangement, precipitation solution is filtered, obtain as clear as crystal clear water.
This batch of test and second batch test are almost carried out (wastewater treatment stage) simultaneously, thus early stage be all to using 100 order iron powders as reducing agent, but reduction efficiency is too low, the reaction time is oversize.Thereby the later stage adopts pyrosulfurous acid sodium reduction to compare.
The analytical method of experimentation collected specimens is with embodiment 1 and 2, and in soil sample, Determination of Hexavalent Chromium the results are shown in table 5.Drip washing soil once, the content of 6-valence Cr ions of sand grains and powder differs larger, reaches 2500mg/kg difference.
Table 5 embodiment 3 test pedotheque determination of hexavalent chromium content
By measurement result, calculate hexavalent chromium removal rate in soil, in Table 6.Can find out, catch up with single test and compare, although this time test is brought up to 10:1 by soil ratio, twice test soil hexavalent chromium removal is suitable, and the soil in the pollution place of production that this explanation is selected for us, improves soil ratio and can not increase hexavalent chromium removal rate.With first test, compare, watery hydrochloric acid concentration is doubled, total mixing time is still 6h, and hexavalent chromium removal rate is still lower, illustrates that clear water drip washing for the second time brings the raising of hexavalent chromium removal rate really.
Hexavalent chromium removal rate in table 6 embodiment 3 Soil Under Conditions
Not enough for solid-liquid separation step in test, leacheate is separated with soil not thorough, finally cause hexavalent chromium removal rate this deficiency on the low side, we can take other ways to promote, such as making container-like filter with steel wire screen pack (as 500 orders), remaining bottom solid after Separation of Solid and Liquid is emitted, be placed in filter, allow wherein residual leacheate naturally trickle, collect leacheate simultaneously, even can again rinse with clear water, be incorporated to waste water and together process.This process may need the long period, but can improve the efficiency of Separation of Solid and Liquid.
Embodiment 4
Test site and the soil same above-described embodiment of originating.Enable the first screw pump 4(G40-2, Hangzhou Wu Bang industrial pump Co., Ltd produces) by mono-barrel of 30kg() 36%wt hydrochloric acid and 1410kg clear water suction agitator tank 1.The first agitator 3 that startup frame drives in agitator tank 1 top the first motor 2 starts to stir, and is mixed with the dilute hydrochloric acid solution of 0.21mol/L.Under stirring, start conveyer, 288kg soil is sent in agitator tank 1.The first screw pump 4 extracts the solution of agitator tank 1 inside by pipeline and valve, and is connected by the aperture of agitator tank 1 bottom, and circulation pumps into tank interior, fully mixes, thereby realize cycling elution and the stirring of agitator tank 1 inner upper solution with soil.Start timing, continuous stirring 3h.Stop stirring standing sedimentation.By the second screw pump 5(G30-1 for the supernatant of agitator tank 1 internal solution, Hangzhou Wu Bang industrial pump Co., Ltd produces) extract out and be placed in white plastic storage tank 6(1500*1700, Hangzhou Zhong Huan Chemical Equipment Co., Ltd. produces) in, obtain 1197L leacheate.Continuation adds 1197kg clear water, continuous stirring 3h in agitator tank 1.Stop stirring standing sedimentation.Supernatant is extracted out and is mixed in above-mentioned plastic storage tank 6, stir, twice drip washing obtains 2327L leacheate altogether.
The soil of agitator tank bottom drip washing is slowly emitted from bottom discharge mouth, add the water suction of 100kg calcium oxide, stir, be transported to fixed position and deposit.
Hydrochloric acid to adding 38.36kg36%wt technical grade in plastic storage tank 6 leacheates, is adjusted to 2.81 by pH value of solution, adds 19.5kg sodium pyrosulfite, stir, and fully reaction, solution becomes blackish green very soon.Add wherein 26.12kg calcium hydroxide, pH is adjusted to more than 9.85, flocculent deposit is obvious.Start three screw pump 9(G30-1, Hangzhou Wu Bang industrial pump Co., Ltd produces) solution that contains floccule after plastic storage tank 6 reactions is pumped into the connected filter press 10(XMY30/630-UB of the second motor 11, Hangzhou holy well filter Co., Ltd), filter liquor enters cistern 12, and after filtering, solution is as clear as crystal.
This time test adopts separately sodium pyrosulfite as reducing agent, to understand its reduction efficiency.From experimental phenomena, with sodium pyrosulfite, as reducing agent, can greatly shorten the recovery time, reduce reducing agent consumption, thereby reduce costs.
Collected specimens analytical method is the same, and in soil sample, content of 6-valence Cr ions is in Table 7.Identical with first test, the abnormal phenomena of appearance is that in sand grains, content of 6-valence Cr ions, on the contrary than high in powder, approximately exceeds 630mg/kg left and right.This is owing to stirring for the second time, and Stirring can not make sand grains that proportion is larger come back in solution along with solution stirs together, and causes drip washing effect poor compared with powder.
Table 7 embodiment 4 test pedotheque determination of hexavalent chromium content
This time, in test, the water and soil quality of pressing 5:1 with the dilute hydrochloric acid solution of 0.21mol/L for the first time, than drip washing 3h, after separating liquid, then continues with equivalent clear water drip washing 3h, and clearance is 88.1 – 88.2%.And the water and soil quality that first batch of test pressed 10:1 with 0.42mol/L watery hydrochloric acid than drip washing 3h after, then use clear water drip washing 3h, clearance is 88.9 – 92.0%.As can be seen here, concentration of hydrochloric acid and soil ratio are little to hexavalent chromium removal effectiveness affects, and drip washing number of times has impact more significantly to hexavalent chromium removal rate.Compare with single drip washing test, in the soil of hydrochloric acid/clear water Continuous leaching test, total hexavalent chromium removal rate is significantly improved, and roughly improves 10 – 20%.
Hexavalent chromium removal rate in table 8 embodiment 4 Soil Under Conditions
A kind of ELUTION METHOD of hexavalent chromium polluted soil, comprise following several step: drip washing stirring, Separation of Solid and Liquid, hexavalent chrome reduction and precipitation and precipitation are removed, described drip washing is stirred the equipment using and is comprised agitator tank 1, the first motor 2, the first agitator 3 and the first screw pump 4,2, described the first motor is connected in agitator tank 1 top and with the first agitator 3, the first screw pump 4 imports are connected with the through hole that agitator tank 1 top is provided with by pipeline, pipeline stretches in tank body, and the through hole that the first screw pump 4 outlets are provided with agitator tank 1 bottom is connected; The equipment that Separation of Solid and Liquid is used comprises that the second screw pump 5 and plastic storage tank 6, the second screw pumps 5 are connected with agitator tank 1 body is inner by pipeline, extract solution and enter plastic storage tank 6; The equipment that hexavalent chrome reduction and precipitation are used comprises plastic storage tank 6, the second agitator 7 and doser 8, in described plastic storage tank 6, by doser 8, adds medicament, the solution that the second agitator 7 stirs in plastic storage tank 6; Precipitation is removed the equipment using and is comprised plastic storage tank 6, three screw pump 9, filter press 10, the second motor 11 and cistern 12, the second motor 11 is located at one end of filter press 10, cistern 12 is located at the below of filter press 10, described three screw pump 9 will pump into filter press 10 away from one end of the second motor 11 containing floccule solution after plastic storage tank 6 reactions, and filter liquor enters cistern 12.By the hydrochloric acid of 0.21 – 0.82mol/L and contaminated soil, according to mass ratio, be that 5:1 – 10:1 stirs, standing rear extraction supernatant, supernatant is added under acid condition reducing agent iron powder or sodium pyrosulfite or its two arbitrarily than mixture, addition is every kg soil 59 – 68g, by hexavalent chrome reduction in leacheate, it is trivalent chromium, add solid base that trivalent chromium is precipitated out, realize separated.This complete set of equipments also can be used for above each embodiment, carries out the drip washing of contaminated soil and processes.
Claims (7)
1. the ELUTION METHOD of a hexavalent chromium polluted soil, it is characterized in that be that 5:1 – 10:1 stirs by the hydrochloric acid of 0.21 – 0.82 mol/L and contaminated soil according to mass ratio, standing rear extraction supernatant, supernatant is added under acid condition reducing agent iron powder or sodium pyrosulfite or its two arbitrarily than mixture, addition is every kg soil 59 – 68g, by hexavalent chrome reduction in leacheate, be trivalent chromium, add solid base that trivalent chromium is precipitated out, realize separated.
2. the ELUTION METHOD of hexavalent chromium polluted soil according to claim 1, is characterized in that described drip washing crosses respectively 6 mm and 2 mm screen clothes with Polluted Soil and obtain.
3. the ELUTION METHOD of hexavalent chromium polluted soil according to claim 1, is characterized in that described mixing time is 3 – 6 h.
4. the ELUTION METHOD of hexavalent chromium polluted soil according to claim 1, is characterized in that the pH reducing under described acid condition is 0.9 – 3.
5. the ELUTION METHOD of hexavalent chromium polluted soil according to claim 1, is characterized in that described precipitation solid base is calcium hydroxide.
6. the ELUTION METHOD of hexavalent chromium polluted soil according to claim 1, adds solid base precipitation trivalent chromium described in it is characterized in that, pH is adjusted to 9～10 and is terminal.
7. the ELUTION METHOD of a hexavalent chromium polluted soil, it is characterized in that the key step comprising has drip washing to stir, Separation of Solid and Liquid, hexavalent chrome reduction and precipitation and precipitation are removed, described drip washing is stirred the equipment using and is comprised agitator tank (1), the first motor (2), the first agitator (3) and the first screw pump (4), described the first motor (2) frame is connected in agitator tank (1) top and with the first agitator (3), the first screw pump (4) import is connected with the through hole that agitator tank (1) top is provided with by pipeline, pipeline stretches in tank body, the first screw pump (4) outlet is connected with the through hole that agitator tank (1) bottom is provided with, the equipment that Separation of Solid and Liquid is used comprises the second screw pump (5) and plastic storage tank (6), and the second screw pump (5) is connected by pipeline and agitator tank (1) body are inner, extracts solution and enters plastic storage tank (6), the equipment that hexavalent chrome reduction and precipitation are used comprises plastic storage tank (6), the second agitator (7) and doser (8), in described plastic storage tank (6), by doser (8), add medicament, the second agitator (7) stirs the solution in plastic storage tank (6), precipitation is removed the equipment using and is comprised plastic storage tank (6), three screw pump (9), filter press (10), the second motor (11) and cistern (12), the second motor (11) is located at one end of filter press (10), cistern (12) is located at the below of filter press (10), described three screw pump (9) will pump into filter press (10) away from one end of the second motor (11) containing floccule solution after plastic storage tank (6) reaction, and filter liquor enters cistern (12), by the hydrochloric acid of 0.21 – 0.82 mol/L and contaminated soil, according to mass ratio, be that 5:1 – 10:1 stirs, standing rear extraction supernatant, supernatant is added under acid condition reducing agent iron powder or sodium pyrosulfite or its two arbitrarily than mixture, addition is every kg soil 59 – 68g, by hexavalent chrome reduction in leacheate, it is trivalent chromium, add solid base that trivalent chromium is precipitated out, realize separated.
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| CN201310493630.2A CN103521513B (en) | 2013-10-18 | 2013-10-18 | Leaching method of soil polluted by hexavalent chromium |
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| CN103920701A (en) * | 2014-04-24 | 2014-07-16 | 杭州大地环保工程有限公司 | Method for restoring chromium-polluted soil |
| CN103962373A (en) * | 2014-05-29 | 2014-08-06 | 武汉大学 | Organic contaminated soil remediation device based on leacheate recycling |
| CN104610973A (en) * | 2014-12-11 | 2015-05-13 | 桑德环境资源股份有限公司 | Chromium-polluted soil restoration leaching agent and chromium-polluted soil restoration method |
| CN105127190A (en) * | 2015-08-11 | 2015-12-09 | 青海省环境科学研究设计院 | Method for repairing hexavalent chromium in chromium polluted soil |
| CN105215051A (en) * | 2015-11-10 | 2016-01-06 | 辽宁石油化工大学 | A kind of reduction-stabilisation two-period form restorative procedure of chromium-polluted soil |
| CN108273837A (en) * | 2018-01-04 | 2018-07-13 | 重庆大学 | A kind of calcium ion and pyrosulfurous acid radical ion mixture and its application |
| CN108372196A (en) * | 2018-02-09 | 2018-08-07 | 广州市怡地环保有限公司 | Heavy-metal contaminated soil restorative procedure |
| CN108941173A (en) * | 2018-05-31 | 2018-12-07 | 河北科技大学 | The elution extracting method of soil Cr VI |
| CN110695078A (en) * | 2019-10-16 | 2020-01-17 | 重庆大学 | Contaminated soil ex-situ remediation device and working mode and process thereof |
| CN113333449A (en) * | 2021-07-22 | 2021-09-03 | 湖南中森环境科技有限公司 | Leaching equipment and leaching method for high-concentration heavy metal contaminated soil |
| CN113732042A (en) * | 2021-07-28 | 2021-12-03 | 湖南新九方科技有限公司 | Leaching/wet detoxification method for different chromium-polluted media |
| CN114029333A (en) * | 2021-11-30 | 2022-02-11 | 广东省农业科学院农业资源与环境研究所 | Novel method for repairing soil polluted by heavy metals of cadmium, lead, mercury and chromium |
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| CN106583436A (en) * | 2016-12-16 | 2017-04-26 | 亿利首建生态科技有限公司 | Leaching method for remediating hexavalent chromium contaminated soil |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103920701B (en) * | 2014-04-24 | 2016-05-11 | 杭州大地环保工程有限公司 | A kind of restorative procedure of chromium-polluted soil |
| CN103920701A (en) * | 2014-04-24 | 2014-07-16 | 杭州大地环保工程有限公司 | Method for restoring chromium-polluted soil |
| CN103962373A (en) * | 2014-05-29 | 2014-08-06 | 武汉大学 | Organic contaminated soil remediation device based on leacheate recycling |
| CN104610973B (en) * | 2014-12-11 | 2018-10-09 | 桑德环境资源股份有限公司 | Repair the eluent and method of chromium-polluted soil |
| CN104610973A (en) * | 2014-12-11 | 2015-05-13 | 桑德环境资源股份有限公司 | Chromium-polluted soil restoration leaching agent and chromium-polluted soil restoration method |
| CN105127190A (en) * | 2015-08-11 | 2015-12-09 | 青海省环境科学研究设计院 | Method for repairing hexavalent chromium in chromium polluted soil |
| CN105215051A (en) * | 2015-11-10 | 2016-01-06 | 辽宁石油化工大学 | A kind of reduction-stabilisation two-period form restorative procedure of chromium-polluted soil |
| CN105215051B (en) * | 2015-11-10 | 2018-06-26 | 辽宁石油化工大学 | A kind of reduction of chromium-polluted soil-stabilisation two-period form restorative procedure |
| CN108273837B (en) * | 2018-01-04 | 2020-05-26 | 重庆大学 | Calcium ion and pyrosulfite ion mixture and application thereof |
| CN108273837A (en) * | 2018-01-04 | 2018-07-13 | 重庆大学 | A kind of calcium ion and pyrosulfurous acid radical ion mixture and its application |
| CN108372196A (en) * | 2018-02-09 | 2018-08-07 | 广州市怡地环保有限公司 | Heavy-metal contaminated soil restorative procedure |
| CN108941173A (en) * | 2018-05-31 | 2018-12-07 | 河北科技大学 | The elution extracting method of soil Cr VI |
| CN110695078A (en) * | 2019-10-16 | 2020-01-17 | 重庆大学 | Contaminated soil ex-situ remediation device and working mode and process thereof |
| CN113333449A (en) * | 2021-07-22 | 2021-09-03 | 湖南中森环境科技有限公司 | Leaching equipment and leaching method for high-concentration heavy metal contaminated soil |
| CN113732042A (en) * | 2021-07-28 | 2021-12-03 | 湖南新九方科技有限公司 | Leaching/wet detoxification method for different chromium-polluted media |
| CN114029333A (en) * | 2021-11-30 | 2022-02-11 | 广东省农业科学院农业资源与环境研究所 | Novel method for repairing soil polluted by heavy metals of cadmium, lead, mercury and chromium |
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