CN105523665A - Method for recovering chromium from leather tanning waste water - Google Patents
Method for recovering chromium from leather tanning waste water Download PDFInfo
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- CN105523665A CN105523665A CN201610020316.6A CN201610020316A CN105523665A CN 105523665 A CN105523665 A CN 105523665A CN 201610020316 A CN201610020316 A CN 201610020316A CN 105523665 A CN105523665 A CN 105523665A
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
- C02F11/122—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering using filter presses
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/18—Treatment of sludge; Devices therefor by thermal conditioning
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
- C02F2101/22—Chromium or chromium compounds, e.g. chromates
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Abstract
The invention discloses a method for recovering chromium from leather tanning waste water. The method comprises the following steps: (1) pretreatment; (2) precipitation separation; (3) dehydration; (4) acidification; and (5) reduction. By adoption of the method disclosed by the invention to carry out recovery and resource utilization of heavy metal element chromium in the leather tanning waste water, the problems of up-to-standard release of chromium-containing waste water and safe disposal of chromium-containing hazardous wastes are effectively solved, a new approach for treating the chromium in the leather tinning waste water is opened, the recovered chromium liquor is used for a leather tinning process, the waste is changed into a valuable thing, the added amount of chromium powder is reduced, the production cost is reduced, the generated quantity of chromium-containing hazardous wastes is reduced at the same time, and energy conservation and emission reduction are realized. Moreover, according to the method disclosed by the invention, the chromium-containing sludge generated by the treatment of leather tanning chromium-containing waste water is prepared into a chromium tanning agent, useful components in the sludge are effectively utilized, and resource waste and environmental pollution are reduced, so that the method accords with the concepts of clean production and cycle economy.
Description
Technical field
The present invention relates to the method reclaiming chromium from leather tanning wastewater, belong to field of waste water treatment.
Background technology
The leather that chrome tanning agent tanning becomes is water-fastness, and shelf-stable, has best hydrothermal stability, therefore widely uses in leather tanning processing.According to statistics, often one ton of rawhide is processed, Cr
2o
3consumption is about 50kg, wherein has more than 1/3rd do not absorbed by leather and enter in waste water, and this not only causes the waste of chromium resource, and brings serious water pollution problems.Because chromium is heavy metal, belong to the first kind pollutent of national strict control discharge.In order to the chromium in waste water is removed, often need to add a large amount of chemical agents, and the chemical sludge that final formation is a large amount of.
Specify according to " National Hazard refuse register ", the chromium-bearing sludge that the process of fur tanning processing waste water produces belongs to HW21 class Hazardous wastes in the useless register of danger, and now current way transfers to the danger of qualification useless process unit to be undertaken managing and disposing by Hazardous wastes after the chromium in tanning waste water is formed chromium mud by chemical precipitation.And it is reported, often processing one ton endangers useless containing chromium, expense is up to 3000 yuan, and this is difficult to bear for most of leather processing enterprise.Therefore the chromium in leather tanning chromate waste water is carried out reclaiming and being back to production technique, while reducing costs to leather manufacturing enterprise, not only solve the process problem of chromate waste water, more importantly solve the handling problems of chromium-bearing sludge, achieve the unification of environmental benefit, economic benefit and social benefit three.At present, disclosing of existing chromate waste water treatment technology, as disclosed a kind of method reclaiming collagen protein and chromic salts from chromium scrap leather slag in CN103101491A, the method use the chemical such as metal oxide, tensio-active agent, cost is high, other impurity of easy introducing, are unfavorable for the recycling of chromium.For another example disclose process for processing chromate-containing waste water in CN103833155A, the method recovery utilization rate is low.
Summary of the invention
The technical problem to be solved in the present invention overcomes existing defect, provide a kind of method reclaiming chromium in leather tanning wastewater, the feature of the method for leather processing industry chromate waste water and the requirement of production technique, chromium in leather tanning wastewater is carried out separation and becomes chromium mud, then carry out dewatering, acidifying, to reclaim after the operation such as reduction, be back to leather tanning operation, reduce cost recovery, recovery utilization rate is high.
The invention provides following technical scheme: a kind of method reclaiming chromium from leather tanning wastewater, comprise following each step:
(1) pre-treatment: remove impurity, grease, suspended substance and partial organic substances in leather tanning wastewater;
(2), there is flocculation reaction and form Cr (OH) in precipitate and separate: the waste water ph after regulating step (1) process, to alkalescence, adds alkali and adds settling agent simultaneously
3precipitation, carry out steam heating during flocculation reaction and carry out mechanical stirring simultaneously, temperature of reaction is 38 DEG C-40 DEG C, mixing speed is 30-45rpm, reaction times is 1 ~ 2h, and the settling time is 4 ~ 5h, then carries out mud-water separation and obtains processed waste water and chromium mud, described processed waste water carries out aftertreatment, and it is 95% ~ 97% that described chromium mud is concentrated into water ratio;
(3) dewater: the chromium mud after concentrated carries out filter-press dehydration process, after dehydration, the water ratio of chromium mud is 75% ~ 81%;
(4) acidifying: add the vitriol oil in chromium mud after dewatering, acid adding limit, limit is stirred, and passes into steam simultaneously and improves chrome liquor temperature gradually, when chrome liquor temperature reaches 88 DEG C ~ 93 DEG C, steam off Keep agitation;
(5) reduce: add reductive agent in the chromium mud after acidifying by Cr wherein
6+be reduced to Cr
3+, continuously stirring, disappears until yellow, must can be used as the chrome liquor of chrome tanning agent raw material.
Know-why of the present invention is as follows:
Cr
3++3OH
-＝Cr(OH)
3↓
Cr(OH)
3+H
2SO
4＝Cr(OH)SO
4+2H
2O
The method reclaiming chromium from leather tanning wastewater of the present invention, technique is simple, carrying out oxidizing reaction, decreasing production cost without the need to adding oxygenant, in addition also without the need to adding organism, avoiding and introducing other impurity, improve the recovery utilization rate of chromium.In whole technique, the step of most critical is step (2) precipitate and separate, due to Cr (OH)
3precipitation is amphoteric hydroxide, all can dissolve under strong acid or basic conditions, and granularity is tiny not easily precipitates, so reaction conditions controls extremely important.First be the control of PH, 20%NaOH easily controls pH value in the art, next is the control of reaction and settling process, suitable heating and temperature are 38 DEG C-40 DEG C and are conducive to fast reaction speed, increase floc particle, improve deposition efficiency, suitable mechanical stirring and mixing speed are that 30-45rpm makes reaction evenly more abundant, can improve chromium recovery ratio.Be reaction times and sedimentation time again, the reaction times will be set as 1 ~ 2h, the settling time is that 4 ~ 5h can improve deposition efficiency.Pass into the dissolving that steam is conducive to accelerating chromium mud in addition in step (4), directly pass into steam and more can promote mix and blend than indirect heating, make dissolving faster.
, in step (1), described leather tanning wastewater first removes impurity through mechanical grille in such scheme preferably, is then being separated grease, suspended substance and partial organic substances through airfloat equipment, and then is removing suspension material in liquid through filter.
In above-mentioned either a program preferably, in step (1), described mechanical grille is Barrate type grilling, and grizzly bar gap is 1mm; Described airfloat equipment is pressure air-dissolving air-float machine, and disengaging zone surface load is 2 ~ 3m
3/ m
2h, the dissolved air flotation time is 30 ~ 40min, and dissolved air water reflux ratio is 30% ~ 50%; Described strainer is brush type self-cleaning filter, and filtering accuracy is 80 μm, and intake pressure is 3kg/cm
2.
Owing to taking strenuous primary treatment measure in the present invention, decrease impurity, the quality of recovery chromium is improved greatly.
In above-mentioned either a program preferably, in step (2), described pH regulator alkali lye is 20%NaOH solution, and pH controls (to be preferably 9.5) in 8.5 ~ 10 scopes, and described settling agent is MgSO
4, generate fine and close Mg (OH) in the basic conditions
2throw out, dosage is 50-80mg/l.
Ordinary method lime or MgO make precipitation agent, and because its solubleness is lower, dissolve and add inconvenience, and can bring the problems such as impurity fouling, we select 20%NaOH solution adjust ph to make precipitation agent, and the MgSO adopting solubleness high
4make settling agent, the throw out of generation is fine and close, sedimentation is fast, mud amount is few, easy filter-press dehydration, and the chromium mud quality obtained and purity better; Add alkali to add settling agent simultaneously and can accelerate settling velocity, improve the organic efficiency of chromium, generate fine and close Mg (OH) in the basic conditions
2throw out, chromium recovery ratio can reach more than 98%.
In above-mentioned either a program preferably, in step (2), temperature of reaction is about 40 DEG C, and mixing speed is 40rpm, and the reaction times is 2h, and the settling time is 4.5h.
Preferred reaction conditions, make deposition efficiency better, chromium recovery ratio is higher.
In the waste water be separated in step (2), the rate of recovery of chromium is greater than 98%, and the chromium mud water ratio obtained is generally 99.2%-99.4%.
In above-mentioned either a program preferably, in step (3), chromium mud after concentrated is delivered to plate-and-frame filter press through sludge pump and carries out filter-press dehydration process, described plate-and-frame filter press working temperature is normal temperature, operating pressure 1.0MPa, press filtration cycle 4-6h, wherein enters mud 2 ~ 3h, pressurize 1h, dump 1h.Described sludge pump is spiral pump or pneumatic diaphragm pump, operating pressure >=0.6Mpa.
Be employed herein a press filtration, save cost recovery.
In above-mentioned either a program preferably, in step (4), acidifying acid used is the vitriol oil of 98%, and consumption is Cr in chromium mud
2o
31.5 ~ 2.5 times (are preferably 2 times) of content, constantly stir during acidifying, pass into steam simultaneously and improve chrome liquor temperature gradually, when chrome liquor temperature reaches 90 DEG C, and steam off Keep agitation 2h.
In above-mentioned either a program preferably, in step (5), described reductive agent is NaHSO
3, consumption is 1.8 ~ 2.2kg/m
3chrome liquor (is preferably 2kg/m
3), the reaction times is 30min, stirs during reaction.
Owing to containing part sexavalent chrome Cr in chromium mud
6+impurity and make chrome liquor displaing yellow, in order to avoid reclaiming the sexavalent chrome Cr in chrome liquor
6+may have a negative impact to quality product, therefore add reductive agent.
In above-mentioned either a program preferably, described method also comprises step (6) and mends chromium, obtains effective chromium content in chrome liquor, and supplement chromium powder according to manufacturing technique requirent after detecting reduction, and limit edged stirs, until dissolve completely; Step (7) ageing, the chrome liquor that step (6) reclaims is through still aging before reuse, and supernatant fluid reuse, impurities at bottom is got rid of.
In above-mentioned either a program preferably, in step (6), described chromium powder is Cr (OH) SO
4(basic chromium sulfate), to add in rear chrome liquor chrome content with chromium sesquioxide (Cr
2o
3) count 20% ~ 25%; In step (7), described digestion time is 5-7d.
Method of the present invention comprises the step of mending chromium further, to ensure that the chrome liquor reclaimed meets production technique desired concn, makes chrome liquor reenter production, is re-used.After ageing, pH value is 2.5-3.0, and basicity is about 40%.
Beneficial effect of the present invention: after leather tanning wastewater is passed through strenuous primary treatment (waste water removal of impurities, oil removing, oil removal and organism) and precipitate and separate by method of the present invention, the chromium mud obtained through steps such as filter-press dehydration, acidifying, reduction, benefit chromium, ageings, makes the chrome tanning agent meeting manufacturing technique requirent again.Method of the present invention is adopted to reclaim and recycling heavy metal element chromium in leather tanning wastewater, both the safe disposal problem having efficiently solved chromate waste water qualified discharge and given up containing chromium danger, also for the process of leather tanning wastewater chromium opens up a new way, recovery chrome liquor is back to leather tanning operation, turn waste into wealth, decrease chromium powder dosage, reduce production cost, decrease containing chromium Hazardous wastes generation simultaneously, achieve energy-saving and emission-reduction; And the chromium-bearing sludge that the process of leather tanning chromate waste water produces is made chrome tanning agent by the method for the invention, effectively make use of useful component in mud, decreases the wasting of resources and environmental pollution, meet the theory of cleaner production and recycling economy.
Accompanying drawing explanation
Fig. 1 is a kind of process flow sheet reclaiming a preferred embodiment of the method for chromium from leather tanning wastewater of the present invention.
Embodiment
Below the preferred embodiments of the present invention are described, should be appreciated that preferred embodiment described herein is only for instruction and explanation of the present invention, is not intended to limit the present invention.
Embodiment 1:
From leather tanning wastewater, reclaim a method for chromium, the sewage of waste liqouor system is from tanning and retanning procedures, and waste water chromium content is 2500 ~ 3000mg/L, and the designing treatment water yield is 350m
3/ d, pH value is 3.5 ~ 4.5, recovery process schema 1, and concrete steps are as follows:
(1) pre-treatment: waste water by after artificial grid and mechanical grille interception agglomerate floater, then is separated grease and other fine suspension and colloidalmaterial further by pressurized dissolved air flotation, then removes impurity by self-stip mechanical filter; Fine fack gap 1mm, Air Bearing Surface load 2.5m
3/ m
2h, the dissolved air flotation time is 35min, and dissolved air water reflux ratio is 40%, self-cleaning filtering precision 80 μm;
(2) precipitate and separate: the water outlet through step (1) strenuous primary treatment adds 20%NaOH solution and and settling agent MgSO
4, and carry out heated and stirred reaction, form Cr (OH)
3precipitation is separated, and flocculation reaction tank steam is heated to 40 DEG C, and pH controls between 8 ~ 9, MgSO
4dosage is 65mg/l, and mixing speed is 40rpm, and the reaction times is 2h, and the settling time is 4h, and then carry out mud-water separation and obtain processed waste water and chromium mud, described processed waste water carries out aftertreatment, and it is 95% ~ 97% that described chromium mud is concentrated into water ratio;
(3) dewater: the chromium-bearing sludge that step (2) obtains carries out the chromium mud that thickening obtains solid content 25%, chromium mud after concentrated is delivered to plate-and-frame filter press through sludge pump and carries out filter-press dehydration process, described plate-and-frame filter press working temperature is normal temperature, operating pressure 1.0MPa, press filtration cycle 4 ~ 6h, wherein enters mud 2 ~ 3h, pressurize 1h, dump 1h, 75% chromium mud output is about 2.0 ton per days, is converted to Cr
2o
3be 1.28 ton per days;
(4) acidifying: add the vitriol oil in chromium mud after dewatering and carry out acid-soluble under steam heating condition, acidifying acid used is the vitriol oil of 98%, and consumption is Cr in chromium mud
2o
32 times of content, when chrome liquor temperature reaches 90 DEG C, steam off Keep agitation 2h, 98% sulfuric acid dosage 2.5 ton per day;
(5) reduce: add reductive agent in the chromium mud after acidifying by Cr wherein
6+be reduced to Cr
3+, described reductive agent is NaHSO
3, consumption is for being 2kg/m
3, the reaction times is 30min continuously stirring, disappears, must can be used as the chrome liquor of chrome tanning agent raw material, NaHSO until yellow
3dosage 20kg/d;
Chromium recovery ratio reaches 98.5%.Reclaim chrome liquor every day once, belong to interval reuse, carry out tanning and contrast with fresh Chrome Tanning Liquor under manufacturing condition, reclaim leather owse flexibility good, compared with fresh Chrome Tanning Liquor, except showing slightly except dimness to light skin color, other effect is basically identical.Adhere to reuse for a long time, be conducive to reducing comprehensive wastewater processing cost and production cost 15% ~ 20%.
(6) obtain effective chromium content in chrome liquor after detecting reduction, and supplement chromium powder Cr (OH) SO according to manufacturing technique requirent
4, limit edged stirs, until dissolve completely;
(7) ageing 5-7d, reclaims Chrome Tanning Liquor pH and controls between 2.5 ~ 3.
Embodiment 2
Certain tannery's year processing rawhide 1,000,000, producing wastewater flow rate every day is 3000m
3/ d, wherein, Chrome Tanning Wastewater is about 300m
3/ d, Cr in waste water
3+concentration is about 2000mg/L, and pH is 4-5, and adopt the method for the invention to process leather tanning chromate waste water and recycle the chromium mud produced, concrete steps are as follows:
(1) pre-treatment: first by rotary drum grid machine, pressure air-dissolving air-float machine and brush type self-cleaning filter, pre-treatment is carried out to former water, except the impurity such as meat mincing, grease, skin slag, hair, suspended substance in anhydrating, described mechanical grille is Barrate type grilling, and grizzly bar gap is 1mm; Described airfloat equipment is pressure air-dissolving air-float machine, and disengaging zone surface load is 2.5m
3/ m
2h, the dissolved air flotation time is 35min, and dissolved air water reflux ratio is 40%; Described strainer is brush type self-cleaning filter, and filtering accuracy is 80 μm, and intake pressure is 3kg/cm
2;
(2) precipitate and separate: then add liquid caustic soda (20%NaOH solution) and settling agent MgSO
4, limit edged stirs, and controlling pH value in reaction by online pH meter is 9.0, MgSO
4dosage is 65mg/l, reaction 1.5h, and temperature of reaction is about 40 DEG C, and mixing speed is 40rpm, and the reaction times is 2h, generates Cr (OH)
3throw out enters inclined-plate clarifying basin again and carries out mud-water separation, precipitation 5h, water outlet Cr
3+clearance >95%, bottom chromium-bearing sludge regularly enters concentration basin;
(3) dewater: by pneumatic diaphragm pump, mud is pumped into plate-and-frame filter press and dewater, chromium mud after concentrated is delivered to plate-and-frame filter press through sludge pump and carries out filter-press dehydration process, described plate-and-frame filter press working temperature is normal temperature, operating pressure 1.0MPa, press filtration cycle 4 ~ 6h, wherein enter mud 2 ~ 3h, pressurize 1h, dump 1h, 75% is about containing chromium moisture content of the cake after dehydration, sludge output every day (water ratio 75%) is 6.8 tons, if as dangerous solidification disposal of waste, needs every day to dispose to take about 20,000 yuan;
(4) acidifying: the chromium mud vitriol oil is carried out acidifying dissolving, acid adding limit, limit is stirred, and acidifying acid used is the vitriol oil of 98%, and consumption is Cr in chromium mud
2o
32 times of content, pass into steam simultaneously and improve chrome liquor temperature gradually, when chrome liquor temperature reaches 90 DEG C, and steam off Keep agitation 2h;
(5) reduce: add reductive agent in the chromium mud after acidifying by Cr wherein
6+be reduced to Cr
3+, described reductive agent is NaHSO
3, consumption is 2kg/m
3, the reaction times is 30min, continuously stirring, disappears, must can be used as the chrome liquor of chrome tanning agent raw material until yellow.
Every day, recyclable chromium was (with Cr
2o
3meter) about 1050kg, is worth about 2.1 ten thousand yuan, deducts cost recovery about 10,000 yuan, then every day net profit about 30,000 yuan, within 1 year, can save production cost nearly ten million yuan.In addition, the Cr to environmental emission can be reduced every year
3+be 188 tons, economic benefit and environmental benefit are very remarkable;
(6) obtain effective chromium content in chrome liquor after detecting reduction, and supplement chromium powder Cr (OH) SO according to manufacturing technique requirent
4, limit edged stirs, until dissolve completely;
(7) ageing 5-7d, reclaims Chrome Tanning Liquor pH and controls between 2.5 ~ 3.
Embodiment 3:
From leather tanning wastewater, reclaim a method for chromium, comprise following each step:
(1) pre-treatment: remove impurity, grease, suspended substance and partial organic substances in leather tanning wastewater; Described leather tanning wastewater first removes impurity through mechanical grille, is then being separated grease, suspended substance and partial organic substances through airfloat equipment, and then is removing suspension material in liquid through filter; Wherein said mechanical grille is Barrate type grilling, and grizzly bar gap is 1mm; Described airfloat equipment is pressure air-dissolving air-float machine, and disengaging zone surface load is 2 ~ 3m
3/ m
2h, the dissolved air flotation time is 30 ~ 40min, and dissolved air water reflux ratio is 30% ~ 50%; Described strainer is brush type self-cleaning filter, and filtering accuracy is 80 μm, and intake pressure is 3kg/cm
2;
(2), there is flocculation reaction and form Cr (OH) in precipitate and separate: the waste water ph after regulating step (1) process, to alkalescence, adds alkali and adds settling agent simultaneously
3precipitation, carry out steam heating during flocculation reaction and carry out mechanical stirring simultaneously, temperature of reaction is 40 DEG C, and mixing speed is 40rpm, reaction times is 2h, settling time is 4.5h, and then carry out mud-water separation and obtain processed waste water and chromium mud, described processed waste water carries out aftertreatment, it is 95% ~ 97% that described chromium mud is concentrated into water ratio, described pH regulator alkali lye is 20%NaOH solution, and pH controls in 8.5 ~ 10 scopes, and described settling agent is MgSO
4, dosage is 65mg/l;
(3) dewater: the chromium mud after concentrated carries out filter-press dehydration process, after dehydration, the water ratio of chromium mud is 75% ~ 81%, chromium mud after concentrated is delivered to plate-and-frame filter press through sludge pump and carries out filter-press dehydration process, described plate-and-frame filter press working temperature is normal temperature, operating pressure 1.0MPa, press filtration cycle 5h, wherein enters mud 2.5h, pressurize 1h, dump 1h;
(4) acidifying: add the vitriol oil in chromium mud after dewatering, changes the vitriol oil that acid used is 98%, and consumption is Cr in chromium mud
2o
32 times of content, acid adding limit, limit is stirred, and passes into steam simultaneously and improves chrome liquor temperature gradually, when chrome liquor temperature reaches 90 DEG C, steam off Keep agitation 2h;
(5) reduce: add reductive agent in the chromium mud after acidifying by Cr wherein
6+be reduced to Cr
3+, described reductive agent is NaHSO
3, consumption is 2kg/m
3chrome liquor, the reaction times is 30min, continuously stirring during reaction, disappears, must can be used as the chrome liquor of chrome tanning agent raw material until yellow.
(6) chromium is mended: obtain effective chromium content in chrome liquor after detecting reduction, and supplement chromium powder according to manufacturing technique requirent, described chromium powder is Cr (OH) SO
4, add chrome content in rear chrome liquor and count 20% ~ 25% with chromium sesquioxide, limit edged stirs, until dissolve completely;
(7) ageing: the chrome liquor that step (6) reclaims is through still aging 5-7d before reuse, and supernatant fluid reuse, impurities at bottom is got rid of, and reclaims Chrome Tanning Liquor pH and controls between 2.5 ~ 3.
In the present embodiment, chromium recovery ratio reaches 98.9%.
Embodiment 4:
From leather tanning wastewater, reclaim a method for chromium, comprise following each step:
(1) pre-treatment, removes impurity, grease, suspended substance and partial organic substances in leather tanning wastewater; Described leather tanning wastewater first removes impurity through mechanical grille, is then being separated grease, suspended substance and partial organic substances through airfloat equipment, and then is removing suspension material in liquid through filter; Wherein said mechanical grille is Barrate type grilling, and grizzly bar gap is 1mm; Described airfloat equipment is pressure air-dissolving air-float machine, and disengaging zone surface load is 2 ~ 3m
3/ m
2h, the dissolved air flotation time is 30 ~ 40min, and dissolved air water reflux ratio is 30% ~ 50%; Described strainer is brush type self-cleaning filter, and filtering accuracy is 80 μm, and intake pressure is 3kg/cm
2;
(2) precipitate and separate, the waste water ph after regulating step (1) process, to alkalescence, adds alkali and adds settling agent simultaneously, flocculation reaction occurs and forms Cr (OH)
3precipitation, carry out steam heating during flocculation reaction and carry out mechanical stirring simultaneously, temperature of reaction is 38 DEG C, and mixing speed is 30rpm, reaction times is 1h, settling time is 4h, and then carry out mud-water separation and obtain processed waste water and chromium mud, described processed waste water carries out aftertreatment, it is 95% ~ 97% that described chromium mud is concentrated into water ratio, described pH regulator alkali lye is 20%NaOH solution, and pH controls in 8.5 ~ 10 scopes, and described settling agent is MgSO
4, dosage is 50mg/l; Temperature of reaction is about 40 DEG C, and mixing speed is 40rpm, and the reaction times is 2h, and the settling time is 4.5h;
(3) dewater, chromium mud after concentrated carries out filter-press dehydration process, after dehydration, the water ratio of chromium mud is 75% ~ 81%, chromium mud after concentrated is delivered to plate-and-frame filter press through sludge pump and carries out filter-press dehydration process, and described plate-and-frame filter press working temperature is normal temperature, operating pressure 1.0MPa, press filtration cycle 4h, wherein enter mud 2h, pressurize 1h, dump 1h;
(4) acidifying, adds the vitriol oil in chromium mud after dewatering, changes the vitriol oil that acid used is 98%, and consumption is Cr in chromium mud
2o
31.5 times of content, acid adding limit, limit is stirred, and passes into steam simultaneously and improves chrome liquor temperature gradually, when chrome liquor temperature reaches 88 DEG C, steam off Keep agitation 2h;
(5) reduce, add reductive agent in the chromium mud after acidifying by Cr wherein
6+be reduced to Cr
3+, described reductive agent is NaHSO
3, consumption is 1.8kg/m
3chrome liquor, the reaction times is 30min, continuously stirring during reaction, disappears, must can be used as the chrome liquor of chrome tanning agent raw material until yellow.
(6) mend chromium, obtain effective chromium content in chrome liquor after detecting reduction, and supplement chromium powder according to manufacturing technique requirent, described chromium powder is Cr (OH) SO
4, add chrome content in rear chrome liquor and count 20% ~ 25% with chromium sesquioxide, limit edged stirs, until dissolve completely;
(7) ageing, the chrome liquor that step (6) reclaims is through still aging 5-7d before reuse, and supernatant fluid reuse, impurities at bottom is got rid of, and reclaims Chrome Tanning Liquor pH and controls between 2.5 ~ 3.
In the present embodiment, chromium recovery ratio reaches 98.5%.
Embodiment 5:
From leather tanning wastewater, reclaim a method for chromium, comprise following each step:
(1) pre-treatment: remove impurity, grease, suspended substance and partial organic substances in leather tanning wastewater; Described leather tanning wastewater first removes impurity through mechanical grille, is then being separated grease, suspended substance and partial organic substances through airfloat equipment, and then is removing suspension material in liquid through filter; Wherein said mechanical grille is Barrate type grilling, and grizzly bar gap is 1mm; Described airfloat equipment is pressure air-dissolving air-float machine, and disengaging zone surface load is 2 ~ 3m
3/ m
2h, the dissolved air flotation time is 30 ~ 40min, and dissolved air water reflux ratio is 30% ~ 50%; Described strainer is brush type self-cleaning filter, and filtering accuracy is 80 μm, and intake pressure is 3kg/cm
2;
(2), there is flocculation reaction and form Cr (OH) in precipitate and separate: the waste water ph after regulating step (1) process, to alkalescence, adds alkali and adds settling agent simultaneously
3precipitation, carry out steam heating during flocculation reaction and carry out mechanical stirring simultaneously, temperature of reaction is 40 DEG C, and mixing speed is 45rpm, reaction times is 2h, settling time is 5h, and then carry out mud-water separation and obtain processed waste water and chromium mud, described processed waste water carries out aftertreatment, it is 95% ~ 97% that described chromium mud is concentrated into water ratio, described pH regulator alkali lye is 20%NaOH solution, and pH controls in 8.5 ~ 10 scopes, and described settling agent is MgSO
4, dosage is 80mg/l; Temperature of reaction is about 40 DEG C, and mixing speed is 40rpm, and the reaction times is 2h, and the settling time is 4.5h;
(3) dewater: the chromium mud after concentrated carries out filter-press dehydration process, after dehydration, the water ratio of chromium mud is 75% ~ 81%, chromium mud after concentrated is delivered to plate-and-frame filter press through sludge pump and carries out filter-press dehydration process, described plate-and-frame filter press working temperature is normal temperature, operating pressure 1.0MPa, press filtration cycle 6h, wherein enters mud 3h, pressurize 1h, dump 1h;
(4) acidifying: add the vitriol oil in chromium mud after dewatering, changes the vitriol oil that acid used is 98%, and consumption is Cr in chromium mud
2o
32.5 times of content, acid adding limit, limit is stirred, and passes into steam simultaneously and improves chrome liquor temperature gradually, when chrome liquor temperature reaches 93 DEG C, steam off Keep agitation 2h;
(5) reduce: add reductive agent in the chromium mud after acidifying by Cr wherein
6+be reduced to Cr
3+, described reductive agent is NaHSO
3, consumption is 2.2kg/m
3chrome liquor, the reaction times is 30min, continuously stirring during reaction, disappears, must can be used as the chrome liquor of chrome tanning agent raw material until yellow.
(6) chromium is mended: obtain effective chromium content in chrome liquor after detecting reduction, and supplement chromium powder according to manufacturing technique requirent, described chromium powder is Cr (OH) SO
4, add chrome content in rear chrome liquor and count 20% ~ 25% with chromium sesquioxide, limit edged stirs, until dissolve completely;
(7) ageing: the chrome liquor that step (6) reclaims is through still aging 5-7d before reuse, and supernatant fluid reuse, impurities at bottom is got rid of, and reclaims Chrome Tanning Liquor pH and controls between 2.5 ~ 3.
In the present embodiment, chromium recovery ratio reaches 98.5%.
Last it is noted that the foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, although with reference to previous embodiment to invention has been detailed description, for a person skilled in the art, it still can be modified to the technical scheme described in foregoing embodiments, or carries out equivalent replacement to wherein portion of techniques feature.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (10)
1. from leather tanning wastewater, reclaim a method for chromium, it is characterized in that: comprise following each step:
(1) pre-treatment: remove impurity, grease, suspended substance and partial organic substances in leather tanning wastewater;
(2), there is flocculation reaction and form Cr (OH) in precipitate and separate: the waste water ph after regulating step (1) process, to alkalescence, adds alkali and adds settling agent simultaneously
3precipitation, carry out steam heating during flocculation reaction and carry out mechanical stirring simultaneously, temperature of reaction is 38 DEG C-40 DEG C, mixing speed is 30-45rpm, reaction times is 1 ~ 2h, and the settling time is 4 ~ 5h, then carries out mud-water separation and obtains processed waste water and chromium mud, described processed waste water carries out aftertreatment, and it is 95% ~ 97% that described chromium mud is concentrated into water ratio;
(3) dewater: the chromium mud after concentrated carries out filter-press dehydration process, after dehydration, the water ratio of chromium mud is 75% ~ 81%;
(4) acidifying: add the vitriol oil in chromium mud after dewatering, acid adding limit, limit is stirred, and passes into steam simultaneously and improves chrome liquor temperature gradually, when chrome liquor temperature reaches 88 DEG C ~ 93 DEG C, steam off Keep agitation;
(5) reduce: add reductive agent in the chromium mud after acidifying by Cr wherein
6+be reduced to Cr
3+, continuously stirring, until yellow disappearance, must can be used as the chrome liquor of chrome tanning agent raw material.
2. the method for claim 1, it is characterized in that: in step (1), described leather tanning wastewater first removes impurity through mechanical grille, is then being separated grease, suspended substance and partial organic substances through airfloat equipment, and then is removing suspension material in liquid through filter.
3. method as claimed in claim 2, it is characterized in that: in step (1), described mechanical grille is Barrate type grilling, and grizzly bar gap is 1mm; Described airfloat equipment is pressure air-dissolving air-float machine, and disengaging zone surface load is 2 ~ 3m
3/ m
2h, the dissolved air flotation time is 30 ~ 40min, and dissolved air water reflux ratio is 30% ~ 50%; Described strainer is brush type self-cleaning filter, and filtering accuracy is 80 μm, and intake pressure is 3kg/cm
2.
4. the method for claim 1, is characterized in that: in step (2), and described pH regulator alkali lye is 20%NaOH solution, and pH controls in 8.5 ~ 10 scopes, and described settling agent is MgSO
4, dosage is 50-80mg/l.
5. the method for claim 1, is characterized in that: in step (2), temperature of reaction is about 40 DEG C, and mixing speed is 40rpm, and the reaction times is 2h, and the settling time is 4.5h.
6. the method for claim 1, it is characterized in that: in step (3), chromium mud after concentrated is delivered to plate-and-frame filter press through sludge pump and carries out filter-press dehydration process, described plate-and-frame filter press working temperature is normal temperature, operating pressure 1.0MPa, press filtration cycle 4 ~ 6h, wherein enters mud 2 ~ 3h, pressurize 1h, dump 1h.
7. the method for claim 1, is characterized in that: in step (4), and acidifying acid used is the vitriol oil of 98%, and consumption is Cr in chromium mud
2o
31.5 ~ 2.5 times of content, constantly stir during acidifying, pass into steam simultaneously and improve chrome liquor temperature gradually, when chrome liquor temperature reaches 90 DEG C, and steam off Keep agitation 2h.
8. the method for claim 1, is characterized in that: in step (5), and described reductive agent is NaHSO
3, consumption is 1.8 ~ 2.2kg/m
3chrome liquor, the reaction times is 30min, stirs during reaction.
9. the method for claim 1, is characterized in that: described method also comprises step (6) and mends chromium, obtains effective chromium content in chrome liquor, and supplement chromium powder according to manufacturing technique requirent after detecting reduction, and limit edged stirs, until dissolve completely; Step (7) ageing, the chrome liquor that step (6) reclaims is through still aging before reuse, and supernatant fluid reuse, impurities at bottom is got rid of.
10. method as claimed in claim 9, it is characterized in that: in step (6), described chromium powder is Cr (OH) SO
4, add chrome content in rear chrome liquor and count 20% ~ 25% with chromium sesquioxide; In step (7), described digestion time is 5-7d.
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| CN107640848A (en) * | 2016-07-22 | 2018-01-30 | 宝山钢铁股份有限公司 | A kind of method of the processing of flushing waste water containing chromium |
| CN107935297A (en) * | 2017-11-14 | 2018-04-20 | 辛集市东盟制革有限公司 | A kind of energy-efficient Tannery Wastewater Treatment Technology |
| CN108193002A (en) * | 2018-02-09 | 2018-06-22 | 四川大学 | A kind of method that chrome tanning agent is prepared using process hides waste material containing chromium |
| CN108686471A (en) * | 2018-05-23 | 2018-10-23 | 盐城大捷实业有限公司 | A kind of purifier in automotive seat process |
| CN110923477A (en) * | 2019-12-11 | 2020-03-27 | 中南大学 | Method for separating and recovering chromium in tanning chromium-containing sludge |
| CN114804570A (en) * | 2022-04-29 | 2022-07-29 | 上海同臣环保有限公司 | Chemical conditioning deep dehydration method for sludge |
| CN115465968A (en) * | 2022-09-16 | 2022-12-13 | 嘉兴学院 | Method for separating and recovering chromium in chrome tanning waste liquid |
| IT202100023831A1 (en) * | 2021-09-16 | 2023-03-16 | Giorgio Boschi | Chrome recovery process from tanning sludge and a plant. |
| CN116891315A (en) * | 2023-07-12 | 2023-10-17 | 广东威特雅环境科技有限公司 | Method for chromium plating wastewater hazardous waste reduction and chromium mud recycling |
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| CN107640848A (en) * | 2016-07-22 | 2018-01-30 | 宝山钢铁股份有限公司 | A kind of method of the processing of flushing waste water containing chromium |
| CN107935297A (en) * | 2017-11-14 | 2018-04-20 | 辛集市东盟制革有限公司 | A kind of energy-efficient Tannery Wastewater Treatment Technology |
| CN108193002A (en) * | 2018-02-09 | 2018-06-22 | 四川大学 | A kind of method that chrome tanning agent is prepared using process hides waste material containing chromium |
| CN108193002B (en) * | 2018-02-09 | 2020-06-12 | 四川大学 | Method for preparing chrome tanning agent by using chrome-containing waste material in leather making |
| CN108686471A (en) * | 2018-05-23 | 2018-10-23 | 盐城大捷实业有限公司 | A kind of purifier in automotive seat process |
| CN110923477A (en) * | 2019-12-11 | 2020-03-27 | 中南大学 | Method for separating and recovering chromium in tanning chromium-containing sludge |
| IT202100023831A1 (en) * | 2021-09-16 | 2023-03-16 | Giorgio Boschi | Chrome recovery process from tanning sludge and a plant. |
| CN114804570A (en) * | 2022-04-29 | 2022-07-29 | 上海同臣环保有限公司 | Chemical conditioning deep dehydration method for sludge |
| CN114804570B (en) * | 2022-04-29 | 2023-12-12 | 上海同臣环保有限公司 | Deep dehydration method for chemical conditioning of sludge |
| CN115465968A (en) * | 2022-09-16 | 2022-12-13 | 嘉兴学院 | Method for separating and recovering chromium in chrome tanning waste liquid |
| CN116891315A (en) * | 2023-07-12 | 2023-10-17 | 广东威特雅环境科技有限公司 | Method for chromium plating wastewater hazardous waste reduction and chromium mud recycling |
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