CN103894407B - A kind of method of restoration of soil polluted by heavy metal - Google Patents

A kind of method of restoration of soil polluted by heavy metal Download PDF

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CN103894407B
CN103894407B CN201410112108.XA CN201410112108A CN103894407B CN 103894407 B CN103894407 B CN 103894407B CN 201410112108 A CN201410112108 A CN 201410112108A CN 103894407 B CN103894407 B CN 103894407B
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heavy metal
clay
soil
adsorbent
wash
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CN201410112108.XA
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CN103894407A (en
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牛晓君
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华南理工大学
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Abstract

The present invention discloses a kind of method of restoration of soil polluted by heavy metal, is fragmentation is carried out in the paddy field by heavy metal pollution, after the dark soil breaking of top layer 0.5-0.6m to the soil block being less than 2-3mm; It is dark that irrigation reaches 10-15cm to the ponding layer on soil horizon; Add modified clay mineral adsorbent, mechanical agitation, leave standstill 6 ~ 8 hours, pull the adsorbent completing absorption of keeping afloat out, supernatant is discharged simultaneously, complete one-level reparation; Light ceramic after rear collection absorption carries out wash-out process in waste water treatment plant, afterwards, repeats step above until soil is up to standard.This method is simple to operate, and cost is low, and removal efficiency is high, corresponds to actual needs, and has good application value.

Description

A kind of method of restoration of soil polluted by heavy metal
Technical field
The present invention relates to polluted soil process field, particularly a kind of method of restoration of soil polluted by heavy metal.
Background technology
Cadmium (Cd), mercury (Hg), arsenic (As) are current putative harmful heavy metal elements, and they produce toxic action by the activity of inhibitory enzyme to human body.Due to the various activities in production of the mankind, the degree that ecological environment pollutes is increasingly sharpened, wherein the severe problem of of can not be ignored has been become to the pollution of soil.Farming land toxic heavy metal element refers generally to mercury, cadmium, arsenic, chromium, five kinds, lead, and south is maximum with cadmium toxicity harm, Pearl River Delta water and soil pollution outstanding problem.These Soils In The Regions are based on the low ph value soil of belt variable electric charge, and weak to external acid buffer capacity, heavy metal crystallized ability is extremely limited, and some local are saturated, reached spilling critical.The activity of heavy metal in soil is quite high, and external environment condition slightly changes, and namely can be extracted into the soil liquid, or enters runoff pollution underground water, surface water, or is absorbed by plants, and enters plant chain harm people and animals.For cadmium, the background value of contaminated area is generally higher, and part contaminated area paddy cadmium content is more than ten times of irrigated area mean value clearly, and vegetables are more up to tens times.Obviously, there is serious potential hazard to common people's health in the farming land of heavy metal pollution.
Find that clay mineral is as the raw material of adsorbent after deliberation, have inexpensive, reserves large, the characteristic of easy exploiting, certainly, most important or its special absorption property of having.Clay mineral is the moisture layer silicate mineral of a class particle very trickle (particle diameter is less than 0.01 millimeter), mainly comprises the mineral such as illite race, vermiculite race, kaolinite race, smectite race, palygorskite race.Clay mineral has that particle is trickle, electronegative, specific area is huge and there is the features such as interlamination region structure, thus has the properties such as adsorptivity, dilatancy, plasticity and ion-exchange.
The purification mechanism of clay mineral heavy metal pollutant, comprises surface reaction two aspects that the suction-operated of clay mineral and clay mineral and heavy metal occur.Suction-operated comprises adsorption and ionic adsorption two class.Adsorption is the enrichments of one or more chemical substances on surface.Clay mineral has that specific area is large, surface energy is high, there is the features such as interlamination region, thus has higher adsorption ability, becomes excellent adsorbent.On the surface of clay mineral, in duct and interlamination region all can occur ion-exchange absorption.The interlamination region of clay mineral has a large amount of negative electrical charges, and heavy metal ion has stronger ion-exchange absorption property.But problem is, this kind of adsorption phenomena is more easily freed by the ion adsorbed, and is undesirable for polluted soil reparation.Therefore carry out " modification " clay, selective absorbent adsorbs also known as obligate, belongs to chemisorbed: one is heavy metal ion and clay mineral surface or the exchange adsorption of scission of link gene proton; Two is in the heavy metal ion multiple tripartite room that enters clay mineral tetrahedral si-o film or octahedral sheet lattice defect; Three is adsorb with the obligate of metal complex form; Four is the form precipitations with metal oxide or other insoluble salts.
Clay mineral carries out modification by methods such as thermal activation, acid activation, inorganic pillared and organic intercalations to clay mineral usually.To increase clay mineral surface charge number and specific area, expansion structure passage, and implant obligate chelation group etc., with the cation exchange capacity (CEC) of the adsorption capacity and clay that improve its surface, obtain better adsorption effect.
Existing patent of invention CN102327893A provides a kind of for material plumbous in removal heavy metal contaminated soil leacheate, this material is iron-based bentonite clay material, and this patent of invention provides the preparation method of this material and the method for lead in this material removal heavy metal leached soil solutions of application simultaneously.Apply this technology and can only remove lead, in chelating eluent (EDTA) leacheate, cause a certain amount of secondary pollution.Still there is certain problem generally in the application of other recovery techniques.Therefore, development of new is efficient, the Heavy Metals in Soil Contaminated Treatment process of low consumption, is especially conceived to have great importance applying of scale and be worth.
Summary of the invention
The object of the invention is to for the deficiencies in the prior art, provide a kind of method of restoration of soil polluted by heavy metal, its concrete technical scheme is as follows:
A method for restoration of soil polluted by heavy metal, comprises the following steps:
(1) fragmentation is carried out in one piece of dry paddy field by heavy metal pollution, after the dark soil breaking of top layer 0.5-0.6m to the soil block being less than 2-3mm; It is dark that irrigation reaches 10-15cm to the ponding layer on soil horizon; Add lightweight resin microsphere as adsorbent, mechanical agitation 20 ~ 30 minutes, leave standstill 6 ~ 8 hours, pull the adsorbent completing absorption of keeping afloat out, supernatant is discharged simultaneously, complete one-level reparation; The proportion of described lightweight resin microsphere is less than 1.
(2) adsorbent completing absorption pulled out in step (1) is put into reaction tank to add eluant, eluent and carry out heavy metal wash-out, the sorbent circulation after wash-out uses; Wash-out waste water after wash-out carries out wastewater treatment; Described wastewater treatment can adopt various existing, Conventional waste water treatment process, such as activated sludge process: SBR, AAO, AO, CASS, oxidation ditch (Carrousel oxidation ditch, opel oxidation ditch, integral type oxidation ditch); Embrane method: bio-contact oxidation, biofilter etc.;
(3) step (1) is repeated with step (2) until the heavy metal content index of polluted soil is qualified to the described paddy field by heavy metal pollution.
Described lightweight resin microsphere can select commercially available this microsphere of pine---FN-80SDE, and described this microballoon of pine FN-80SDE uses FN series microsphere expansion to obtain by loose our company.Shell is thermoplasticity macromolecule, and inside contains the light hollow microballoon of paraffin gas.Jacket ingredients: AN base polymer average grain diameter (um): 20-40 true specific gravity (g/cc): 0.025 moisture (%): less than 3.0% recommendation temperature (DEG C) (1): less than 90 DEG C resistance to pressures (Mpa) (2): more than 20 solvent resistances.Because this microballoon of pine FN-80SDE has low-down proportion, only need a small amount of interpolation, product just can be made when mechanical performance is constant, reduce the density of product significantly.
Preferably, described lightweight resin microsphere (proportion is less than 1) is the phenolic resins tiny balloon of hollow, prepared by employing following steps: be liquid by resol dissolution with solvents, stir with blowing agent, surfactant, pure water and mix, the volume mixture ratio of resole solutions, blowing agent, surfactant, pure water is (80 ~ 120): 5:3:(5 ~ 10), be then suction filtration; Enter drying box dry 3-8 hour at the temperature of 70 DEG C-90 DEG C, after at the temperature of 400-600 DEG C calcination 6-10 hour, to solidify in drying box, dry; Described blowing agent is azo-bis-iso-dimethyl or ABVN or benzoyl peroxide; Described surfactant is the different alcohol dibasic acid esters of maleic acid; Described resol solvent is ethanol or oxolane or dimethyl formamide.
Preferably, described in step (2), wash-out waste water carries out wastewater treatment, described waste water can be passed into filtering ponds through pre-filtering, next enter in pH regulating reservoir and pH value is adjusted to 6.5 ~ 9, after enter reaction tank, by H type cationic ion-exchange resin in reaction tank, heavy metal cation in waste water is by the enrichment of H type strong-acid cation-exchange resin, and the acid ion displaced in hydrogen ion and waste water forms acid solution, then waste water enters except acid anion exchange resins again, and the acid solution in waste water is removed acid anion exchange resins enrichment.
Preferably, heavy metal wash-out described in step (2) adopts thermal desorption processes, puts into reaction tank by the adsorbent completing absorption pulled out in step (1), and adding temperature is that the water of 72 ~ 100 DEG C regulates, and pH value is 4 ~ 6, constantly stirs and carry out thermal desorption; (5) by the mixture after thermal desorption, rapid filtration, leaches the light ceramic adsorbent after wash-out, and filtrate is attached most importance to metal ion solution.
Preferably, described in step (2), wash-out waste water carries out wastewater treatment, described waste water can be passed into filtering ponds through pre-filtering, next enter in pH regulating reservoir and pH value is adjusted to 6.5 ~ 9, after enter reaction tank, filter add flocculant PAC, coagulant flocculation coagulation in reaction tank after, after precipitation, obtain supernatant; Gained supernatant cholorination, sterilization adopts microwave irradiation 5-10min simultaneously, must reach the water of discharge standard after process; Pass into described coagulant and adopt PDDA, aluminium polychloride, the mixture of shitosan, iron chloride, its mixed proportion is 3:2:1:1, and consumption is 20 ~ 150mg/L.
Preferably, described lightweight resin microsphere can replace with light ceramic.
Preferably, described light ceramic by modified clay mineral adsorbent be montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite makes, be to adopt following steps to make:
(1) get Powdered montmorillonitic clay modified adsorbent, chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite mixing mixed proportion be volume ratio 1:2:1:1; Stir evenly homogenizing, control moisture content < 30%;
(2) enter rotary kiln with after formed by balling machine, control kiln end temperature at 200 ~ 500 DEG C, preheating and drying 20 ~ 50 minutes, controlling firing temperature is 1030 ~ 1410 DEG C, roasting 5 ~ 12 minutes;
(3) it is 120 ~ 1000kg/m that the haydite after roasting or haydite ring formation enter the cooler obtained loose volume weight that cools through discharge port 3light ceramic or haydite ring formation.
Described light ceramic is montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite is made; The preparation process of wherein said montmorillonitic clay modified adsorbent can be, get 200-250 order natural smectite clay powder to add in distilled water and stir 10min and make suspension, add sodium carbonate or sodium pyrophosphate or sodium polyphosphate and stir 10min, add inorganic polymer again and stir 20 minutes, namely complete modification.
Preferably, described inorganic polymer is asbestos or mica or glass or polychlorophosphnitrile.
Preferably, described inorganic polymer can also be aluminosilicate.
The light ceramic that described modified clay mineral adsorbent is montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite is made; The preparation process of wherein said chitin modified clay can be take 100mg shitosan, and the hydrochloric acid adding the mass concentration 1% of 10ml makes it abundant dissolving, and is settled to 1000ml, adds in 2000mg clay after mixing, and uniform stirring 20 minutes, namely completes modification.
The light ceramic that described modified clay mineral adsorbent is montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite is made; The preparation process of wherein said bentonite modified clay can be take 100mg cetrimonium bronmide, and the hydrochloric acid adding the mass concentration 1% of 10ml makes it abundant dissolving, and be settled to 1000ml, add in 2000mg clay after mixing, uniform stirring 20 minutes, namely completes modification.
The light ceramic that described modified clay mineral adsorbent is montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite is made; The preparation process of wherein said phosphoric acid modification attapulgite can be, take 15g attapulgite clay, add 4mol/L phosphoric acid solution 80ml, be placed in boiling water bath and heat suction filtration after 2h, and with pure water, filter cake is washed till neutrality, dry under 103-105 degree Celsius in baking oven, be ground to 70-80 order, namely complete modification.
Compared with prior art, the invention has the beneficial effects as follows: adopt novel technique, simple cost is low, removal heavy metal is effective, effectively removes the various heavy in contaminated soil; Adopt novel adsorbent, phenolic resins lightweight microballoon, greatly can improve the clearance of the heavy metal such as chromium, lead, zinc, copper residual in soil, especially heavy metal chromium, by repairing, sound improvement is carried out to contaminated soil, the remaining quantity of effective minimizing soil cationic, improves soil quality, and being conducive to the later stage cultivates crops.
In the method for restoration of soil polluted by heavy metal of the present invention, by the Optimal Control to each side such as pH value, adsorbent, waste water treatment process, in repair process, substantially increase the clearance of heavy metal, achieve good repairing effect, improve soil quality.
Detailed description of the invention
Below by specific embodiment, technical scheme of the present invention is described further.Following examples do not form limitation of the invention.
Test the contaminated farmland near industrial area, Pearl River Delta, all instrument and equipments used are all commercially available, adopt following scheme:
Embodiment 1
A method for restoration of soil polluted by heavy metal, comprises the following steps:
(1) fragmentation is carried out in one piece of dry paddy field by heavy metal pollution, after the dark soil breaking of top layer 0.5m to the soil block being less than 2mm; It is dark that irrigation reaches 10cm to the ponding layer on soil horizon; Add lightweight resin microsphere as adsorbent, mechanical agitation 20 minutes, leave standstill 6 hours, pull the adsorbent completing absorption of keeping afloat out, supernatant is discharged simultaneously, complete one-level reparation; The proportion of described lightweight resin microsphere is less than 1.
(2) adsorbent completing absorption pulled out in step (1) is put into reaction tank to add eluant, eluent and carry out heavy metal wash-out, the sorbent circulation after wash-out uses; Wash-out waste water after wash-out carries out wastewater treatment;
(3) step (1) is repeated with step (2) until the heavy metal content index of polluted soil is qualified to the described paddy field by heavy metal pollution.
Described lightweight resin microsphere is the phenolic resins tiny balloon of hollow, prepared by employing following steps: be liquid by resol dissolution with solvents, stir with blowing agent, surfactant, pure water and mix, the volume mixture ratio of resole solutions, blowing agent, surfactant, pure water is 80:5:3:5, is then suction filtration; Enter drying box at the temperature of 70 DEG C dry 3 hours, after calcination 6 hours at the temperature of 400-600 DEG C, to solidify in drying box, dry; Described blowing agent is azo-bis-iso-dimethyl; Described surfactant is the different alcohol dibasic acid esters of maleic acid; Described resol solvent is dimethyl formamide.
Described in step (2), wash-out waste water carries out wastewater treatment, described waste water can be passed into filtering ponds through pre-filtering, next enter in pH regulating reservoir and pH value is adjusted to 6.5 ~ 9, after enter reaction tank, by H type cationic ion-exchange resin in reaction tank, heavy metal cation in waste water is by the enrichment of H type strong-acid cation-exchange resin, and the acid ion displaced in hydrogen ion and waste water forms acid solution, then waste water enters except acid anion exchange resins again, and the acid solution in waste water is removed acid anion exchange resins enrichment.
Heavy metal wash-out described in step (2) adopts thermal desorption processes, puts into reaction tank by the adsorbent completing absorption pulled out in step (1), and adding temperature is that the water of 72 ~ 100 DEG C regulates, and pH value is 4 ~ 6, constantly stirs and carry out thermal desorption; (5) by the mixture after thermal desorption, rapid filtration, leaches the light ceramic adsorbent after wash-out, and filtrate is attached most importance to metal ion solution.
Described lightweight resin microsphere can replace with light ceramic.Described light ceramic by modified clay mineral adsorbent be montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite makes, be to adopt following steps to make:
(1) get Powdered montmorillonitic clay modified adsorbent, chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite mixing mixed proportion be volume ratio 1:2:1:1; Stir evenly homogenizing, control moisture content < 30%;
(2) enter rotary kiln with after formed by balling machine, control kiln end temperature at 200 DEG C, preheating and drying 20 minutes, controlling firing temperature is 1030 DEG C, roasting 5 minutes;
(3) it is 120 ~ 1000kg/m that the haydite after roasting or haydite ring formation enter the cooler obtained loose volume weight that cools through discharge port 3light ceramic or haydite ring formation.
The preparation process of described montmorillonitic clay modified adsorbent can be, gets 200 order natural smectite clay powder and adds in distilled water and stir 10min and make suspension, add sodium carbonate and mix 10min, then adds inorganic polymer asbestos and stir 20 minutes, namely completes modification.
The preparation process of described chitin modified clay can be take 100mg shitosan, and the hydrochloric acid adding the mass concentration 1% of 10ml makes it abundant dissolving, and is settled to 1000ml, adds in 2000mg clay after mixing, and uniform stirring 20 minutes, namely completes modification.
The preparation process of described bentonite modified clay can be take 100mg cetrimonium bronmide, and the hydrochloric acid adding the mass concentration 1% of 10ml makes it abundant dissolving, and be settled to 1000ml, add in 2000mg clay after mixing, uniform stirring 20 minutes, namely completes modification.
The preparation process of described phosphoric acid modification attapulgite can be take 15g attapulgite clay, adds 4mol/L phosphoric acid solution 80ml, be placed in boiling water bath and heat suction filtration after 2h, and with pure water, filter cake is washed till neutrality, dry under 103 degrees Celsius in baking oven, be ground to 70 orders, namely complete modification.
In this technique, the heavy metals removal result table of comparisons is in table 1:
Table 1
Result of the test shows, removal efficiency of heavy metals is higher, and after drip washing 3 times, the clearance of Cd is 98.81%, the clearance of Pb is 71.50%, the clearance of Hg is 90.70%.Soil after the present embodiment process can reach hazardous waste judging standard leaching characteristic identification (GB5085.3-2007), improves soil quality.Embodiment 2
Certain contaminated terraced fields
A method for restoration of soil polluted by heavy metal, comprises the following steps:
(1) fragmentation is carried out in one piece of dry paddy field by heavy metal pollution, after the dark soil breaking of top layer 0.55m to the soil block being less than 2.5mm; It is dark that irrigation reaches 12.5cm to the ponding layer on soil horizon; Add lightweight resin microsphere as adsorbent, mechanical agitation 25 minutes, leave standstill 7 hours, pull the adsorbent completing absorption of keeping afloat out, supernatant is discharged simultaneously, complete one-level reparation; The proportion of described lightweight resin microsphere is less than 1.
(2) adsorbent completing absorption pulled out in step (1) is put into reaction tank to add eluant, eluent and carry out heavy metal wash-out, the sorbent circulation after wash-out uses; Wash-out waste water after wash-out carries out wastewater treatment;
(3) step (1) is repeated with step (2) until the heavy metal content index of polluted soil is qualified to the described paddy field by heavy metal pollution.
Described lightweight resin microsphere can select commercially available this microsphere of pine---FN-80SDE, and described this microballoon of pine FN-80SDE uses FN series microsphere expansion to obtain by loose our company.Shell is thermoplasticity macromolecule, and inside contains the light hollow microballoon of paraffin gas.Jacket ingredients: AN base polymer average grain diameter (um): 20 true specific gravities (g/cc): 0.025 moisture (%): less than 3.0% recommendation temperature (DEG C) (1): less than 90 DEG C resistance to pressures (Mpa) (2): more than 20 solvent resistances.Because this microballoon of pine FN-80SDE has low-down proportion, only need a small amount of interpolation, product just can be made when mechanical performance is constant, reduce the density of product significantly.
Heavy metal wash-out described in step (2) adopts thermal desorption processes, puts into reaction tank by the adsorbent completing absorption pulled out in step (1), and adding temperature is that the water of 86 DEG C regulates, and pH value is 5, constantly stirs and carry out thermal desorption; (5) by the mixture after thermal desorption, rapid filtration, leaches the light ceramic adsorbent after wash-out, and filtrate is attached most importance to metal ion solution.
Described in step (2), wash-out waste water carries out wastewater treatment, described waste water can be passed into filtering ponds through pre-filtering, next enter in pH regulating reservoir and pH value is adjusted to 7.8, after enter reaction tank, filter add flocculant PAC, coagulant flocculation coagulation in reaction tank after, after precipitation, obtain supernatant; Gained supernatant cholorination, sterilization adopts microwave irradiation 5min simultaneously, must reach the water of discharge standard after process; Pass into described coagulant and adopt PDDA, aluminium polychloride, the mixture of shitosan, iron chloride, its mixed proportion is 3:2:1:1, and consumption is 20mg/L.
Described lightweight resin microsphere can replace with light ceramic.Described light ceramic by modified clay mineral adsorbent be montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite makes, be to adopt following steps to make:
(1) get Powdered montmorillonitic clay modified adsorbent, chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite mixing mixed proportion be volume ratio 1:2:1:1; Stir evenly homogenizing, control moisture content < 30%;
(2) enter rotary kiln with after formed by balling machine, control kiln end temperature at 450 DEG C, preheating and drying 35 minutes, controlling firing temperature is 1200 DEG C, roasting 8 minutes;
(3) it is 120 ~ 1000kg/m that the haydite after roasting or haydite ring formation enter the cooler obtained loose volume weight that cools through discharge port 3light ceramic or haydite ring formation.
Described light ceramic is montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite is made; The preparation process of wherein said montmorillonitic clay modified adsorbent can be, get 200 order natural smectite clay powder to add in distilled water and stir 10min and make suspension, add sodium carbonate or sodium pyrophosphate or sodium polyphosphate and stir 10min, add inorganic polymer again and stir 20 minutes, namely complete modification.Described inorganic polymer is asbestos or mica or glass or polychlorophosphnitrile.
The light ceramic that described modified clay mineral adsorbent is montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite is made; The preparation process of wherein said chitin modified clay can be take 100mg shitosan, and the hydrochloric acid adding the mass concentration 1% of 10ml makes it abundant dissolving, and is settled to 1000ml, adds in 2000mg clay after mixing, and uniform stirring 20 minutes, namely completes modification.
The light ceramic that described modified clay mineral adsorbent is montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite is made; The preparation process of wherein said bentonite modified clay can be take 100mg cetrimonium bronmide, and the hydrochloric acid adding the mass concentration 1% of 10ml makes it abundant dissolving, and be settled to 1000ml, add in 2000mg clay after mixing, uniform stirring 20 minutes, namely completes modification.
The light ceramic that described modified clay mineral adsorbent is montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite is made; The preparation process of wherein said phosphoric acid modification attapulgite can be take 15g attapulgite clay, adds 4mol/L phosphoric acid solution 80ml, be placed in boiling water bath and heat suction filtration after 2h, and with pure water, filter cake is washed till neutrality, dry under 103 degrees Celsius in baking oven, be ground to 70 orders, namely complete modification.
In this technique, the heavy metals removal result table of comparisons is in table 2:
Table 2
Result of the test shows, removal efficiency of heavy metals is higher, and the clearance of Cd is 98.77%, the clearance of Pb is 69.85%, the clearance of Hg is 90.79%.Soil after the present embodiment process can reach hazardous waste judging standard leaching characteristic identification (GB5085.3-2007), improves soil quality.
Embodiment 3
Certain contaminated terraced fields
A method for restoration of soil polluted by heavy metal, comprises the following steps:
(1) fragmentation is carried out in one piece of dry paddy field by heavy metal pollution, after the dark soil breaking of top layer 0.6m to the soil block being less than 3mm; It is dark that irrigation reaches 15cm to the ponding layer on soil horizon; Add lightweight resin microsphere as adsorbent, mechanical agitation 30 minutes, leave standstill 8 hours, pull the adsorbent completing absorption of keeping afloat out, supernatant is discharged simultaneously, complete one-level reparation; The proportion of described lightweight resin microsphere is less than 1.
(2) adsorbent completing absorption pulled out in step (1) is put into reaction tank to add eluant, eluent and carry out heavy metal wash-out, the sorbent circulation after wash-out uses; Wash-out waste water after wash-out carries out wastewater treatment; Described wastewater treatment can adopt various existing, Conventional waste water treatment process, such as activated sludge process: SBR, AAO, AO, CASS, oxidation ditch (Carrousel oxidation ditch, opel oxidation ditch, integral type oxidation ditch); Embrane method: bio-contact oxidation, biofilter etc.;
(3) step (1) is repeated with step (2) until the heavy metal content index of polluted soil is qualified to the described paddy field by heavy metal pollution.
Described lightweight resin microsphere is the phenolic resins tiny balloon of hollow, prepared by employing following steps: be liquid by resol dissolution with solvents, stir with blowing agent, surfactant, pure water and mix, the volume mixture ratio of resole solutions, blowing agent, surfactant, pure water is 120:5:3:10, is then suction filtration; Enter drying box at the temperature of 90 DEG C dry 8 hours, after calcination 10 hours at the temperature of 600 DEG C, to solidify in drying box, dry; Described blowing agent is azo-bis-iso-dimethyl or ABVN or benzoyl peroxide; Described surfactant is the different alcohol dibasic acid esters of maleic acid; Described resol solvent is ethanol or oxolane or dimethyl formamide.
Heavy metal wash-out described in step (2) adopts thermal desorption processes, puts into reaction tank by the adsorbent completing absorption pulled out in step (1), and adding temperature is that the water of 100 DEG C regulates, and pH value is 6, constantly stirs and carry out thermal desorption; (5) by the mixture after thermal desorption, rapid filtration, leaches the light ceramic adsorbent after wash-out, and filtrate is attached most importance to metal ion solution.
Described in step (2), wash-out waste water carries out wastewater treatment, described waste water can be passed into filtering ponds through pre-filtering, next enter in pH regulating reservoir and pH value is adjusted to 9, after enter reaction tank, filter add flocculant PAC, coagulant flocculation coagulation in reaction tank after, after precipitation, obtain supernatant; Gained supernatant cholorination, sterilization adopts microwave irradiation 10min simultaneously, must reach the water of discharge standard after process; Pass into described coagulant and adopt PDDA, aluminium polychloride, the mixture of shitosan, iron chloride, its mixed proportion is 3:2:1:1, and consumption is 150mg/L.
Described lightweight resin microsphere can replace with light ceramic.Described light ceramic by modified clay mineral adsorbent be montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite makes, be to adopt following steps to make:
(1) get Powdered montmorillonitic clay modified adsorbent, chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite mixing mixed proportion be volume ratio 1:2:1:1; Stir evenly homogenizing, control moisture content < 30%;
(2) enter rotary kiln with after formed by balling machine, control kiln end temperature at 200 ~ 500 DEG C, preheating and drying 20 ~ 50 minutes, controlling firing temperature is 1030 ~ 1410 DEG C, roasting 5 ~ 12 minutes;
(3) it is 120 ~ 1000kg/m that the haydite after roasting or haydite ring formation enter the cooler obtained loose volume weight that cools through discharge port 3light ceramic or haydite ring formation.
Described light ceramic is montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite is made; The preparation process of wherein said montmorillonitic clay modified adsorbent can be, get 200-250 order natural smectite clay powder to add in distilled water and stir 10min and make suspension, add sodium carbonate or sodium pyrophosphate or sodium polyphosphate and stir 10min, add inorganic polymer again and stir 20 minutes, namely complete modification.Described inorganic polymer is asbestos or mica or glass or polychlorophosphnitrile.Described inorganic polymer can also be aluminosilicate.
The light ceramic that described modified clay mineral adsorbent is montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite is made; The preparation process of wherein said chitin modified clay can be take 100mg shitosan, and the hydrochloric acid adding the mass concentration 1% of 10ml makes it abundant dissolving, and is settled to 1000ml, adds in 2000mg clay after mixing, and uniform stirring 20 minutes, namely completes modification.
The light ceramic that described modified clay mineral adsorbent is montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite is made; The preparation process of wherein said bentonite modified clay can be take 100mg cetrimonium bronmide, and the hydrochloric acid adding the mass concentration 1% of 10ml makes it abundant dissolving, and be settled to 1000ml, add in 2000mg clay after mixing, uniform stirring 20 minutes, namely completes modification.
The light ceramic that described modified clay mineral adsorbent is montmorillonitic clay modified adsorbent, the mixture of chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite is made; The preparation process of wherein said phosphoric acid modification attapulgite can be, take 15g attapulgite clay, add 4mol/L phosphoric acid solution 80ml, be placed in boiling water bath and heat suction filtration after 2h, and with pure water, filter cake is washed till neutrality, dry under 103-105 degree Celsius in baking oven, be ground to 70-80 order, namely complete modification.
In this technique, the heavy metals removal result table of comparisons is in table 1:
Table 3
Result of the test shows, removal efficiency of heavy metals is higher, and the clearance of Cd is 98.76%, the clearance of Pb is 70.25%, the clearance of Hg is 91.06%.Soil after the present embodiment process can reach hazardous waste judging standard leaching characteristic identification (GB5085.3-2007), improves soil quality.
To those skilled in the art; under this patent design and specific embodiment enlightenment; some distortion that can directly derive from this patent disclosure and general knowledge or associate; those of ordinary skill in the art will recognize also can adopt additive method; or in prior art, commonly use substituting of known technology; and the unsubstantiality of mutual various combination between feature etc. is changed; can be employed equally; this patent representation function and effect can be realized; expansion of illustrating no longer is one by one described in detail, all belongs to this patent protection domain.

Claims (7)

1. a method for restoration of soil polluted by heavy metal, is characterized in that, comprises the following steps:
(1) fragmentation is carried out in one piece of dry paddy field by heavy metal pollution, after the dark soil breaking of top layer 0.5-0.6m to the soil block being less than 3mm; It is dark that irrigation reaches 10-15cm to the ponding layer on soil horizon; Add lightweight resin microsphere or light ceramic or haydite ring formation as adsorbent, mechanical agitation 20 ~ 30 minutes, leave standstill 6 ~ 8 hours, pull the adsorbent completing absorption of keeping afloat out, supernatant is discharged simultaneously, complete one-level reparation;
(2) adsorbent completing absorption pulled out in step (1) is put into reaction tank to add eluant, eluent and carry out heavy metal wash-out, the sorbent circulation after wash-out uses; Wash-out waste water after wash-out carries out wastewater treatment;
(3) step (1) is repeated with step (2) until the heavy metal content index of polluted soil is qualified to the described paddy field by heavy metal pollution;
Described lightweight resin microsphere is the phenolic resins tiny balloon of hollow, prepared by employing following steps: be liquid by resol dissolution with solvents, stir with blowing agent, surfactant, pure water and mix, the volume mixture ratio of resole solutions, blowing agent, surfactant, pure water is (80 ~ 120): 5:3:(5 ~ 10), then suction filtration; Enter drying box dry 3-8 hour at the temperature of 70 DEG C-90 DEG C, after at the temperature of 400-600 DEG C calcination 6-10 hour, to solidify in drying box, dry;
Described light ceramic is made up of the mixture of montmorillonitic clay modified adsorbent, chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite; Described light ceramic or haydite ring formation adopt following steps to make:
(1) get Powdered montmorillonitic clay modified adsorbent, chitin modified clay, bentonite modified clay, phosphoric acid modification attapulgite mixing mixed proportion be volume ratio 1:2:1:1; Stir evenly homogenizing, control moisture content < 30%;
(2) enter rotary kiln with after formed by balling machine, control kiln end temperature at 200 ~ 500 DEG C, preheating and drying 20 ~ 50 minutes, controlling firing temperature is 1030 ~ 1410 DEG C, roasting 5 ~ 12 minutes;
(3) it is 120 ~ 1000kg/m that the haydite after roasting or haydite ring formation enter the cooler obtained loose volume weight that cools through discharge port 3light ceramic or haydite ring formation;
The preparation process of described bentonite modified clay is take 100mg cetrimonium bronmide, and the hydrochloric acid adding the mass concentration 1% of 10ml makes it abundant dissolving, and be settled to 1000ml, add in 2000mg clay after mixing, uniform stirring 20 minutes, namely completes modification.
2. the method for a kind of restoration of soil polluted by heavy metal according to claim 1, is characterized in that: described blowing agent is azo-bis-iso-dimethyl or ABVN or benzoyl peroxide; Described surfactant is the different alcohol dibasic acid esters of maleic acid; Described resol solvent is ethanol or oxolane or dimethyl formamide.
3. the method for a kind of restoration of soil polluted by heavy metal according to claim 1, it is characterized in that: described in step (2), wash-out waste water carries out wastewater treatment, that described waste water is passed into filtering ponds through pre-filtering, next enter in pH regulating reservoir and pH value is adjusted to 6.5 ~ 9, after enter reaction tank, by H type cationic ion-exchange resin in reaction tank, heavy metal cation in waste water is by the enrichment of H type strong-acid cation-exchange resin, and the acid ion displaced in hydrogen ion and waste water forms acid solution, then waste water enters except acid anion exchange resins again, acid solution in waste water is removed acid anion exchange resins enrichment.
4. the method for a kind of restoration of soil polluted by heavy metal according to claim 1, it is characterized in that: heavy metal wash-out described in step (2) adopts thermal desorption processes, reaction tank is put into by the adsorbent completing absorption pulled out in step (1), adding temperature is that the water of 72 ~ 100 DEG C regulates, and pH value is 4 ~ 6, constantly stirs and carry out thermal desorption; By the mixture after thermal desorption, rapid filtration, leaches the adsorbent after wash-out, and filtrate is attached most importance to metal ion solution.
5. the method for a kind of restoration of soil polluted by heavy metal according to claim 1, it is characterized in that: described in step (2), wash-out waste water carries out wastewater treatment, that described waste water is passed into filtering ponds through pre-filtering, next enter in pH regulating reservoir and pH value is adjusted to 6.5 ~ 9, after enter reaction tank, filter add flocculant, coagulant flocculation coagulation in reaction tank after, after precipitation, obtain supernatant; Gained supernatant cholorination, sterilization adopts microwave irradiation 5-10min simultaneously, must reach the water of discharge standard after process.
6. the method for a kind of restoration of soil polluted by heavy metal according to claim 5, it is characterized in that: described coagulant adopts PDDA, aluminium polychloride, the mixture of shitosan, iron chloride, its mixed proportion is 3:2:1:1, and consumption is 20 ~ 150mg/L.
7. the method for a kind of restoration of soil polluted by heavy metal according to claim 1 ~ 6 any one, is characterized in that:
The preparation process of described montmorillonitic clay modified adsorbent is, get 200-250 order natural smectite clay powder to add in distilled water and stir 10min and make suspension, add sodium carbonate or sodium pyrophosphate or sodium polyphosphate and stir 10min, add inorganic polymer again and stir 20 minutes, namely complete modification; Described inorganic polymer is asbestos or mica or glass or polychlorophosphnitrile or aluminosilicate;
The preparation process of described chitin modified clay is take 100mg shitosan, and the hydrochloric acid adding the mass concentration 1% of 10ml makes it abundant dissolving, and is settled to 1000ml, adds in 2000mg clay after mixing, and uniform stirring 20 minutes, namely completes modification;
The preparation process of described phosphoric acid modification attapulgite is take 15g attapulgite clay, adds 4mol/L phosphoric acid solution 80ml, be placed in boiling water bath and heat suction filtration after 2h, and with pure water, filter cake is washed till neutrality, dry under 103-105 degree Celsius in baking oven, be ground to 70-80 order, namely complete modification.
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CN104802298B (en) * 2015-03-03 2017-07-18 广州市金龙峰环保设备工程有限公司 A kind of heavy-metal contaminated soil processing method
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