CN116903214A - Ectopic treatment and resource utilization method for heavy metal polluted river sediment - Google Patents
Ectopic treatment and resource utilization method for heavy metal polluted river sediment Download PDFInfo
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Classifications
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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
- C02F11/10—Treatment of sludge; Devices therefor by pyrolysis
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/30—Processes for preparing, regenerating, or reactivating
- B01J20/3078—Thermal treatment, e.g. calcining or pyrolizing
-
- 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
- C02F1/28—Treatment of water, waste water, or sewage by sorption
- C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
-
- 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
- C02F11/008—Sludge treatment by fixation or solidification
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/007—Contaminated open waterways, rivers, lakes or ponds
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/40—Valorisation of by-products of wastewater, sewage or sludge processing
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Environmental & Geological Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Water Supply & Treatment (AREA)
- Engineering & Computer Science (AREA)
- Hydrology & Water Resources (AREA)
- Analytical Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
The invention discloses an ex-situ treatment and resource utilization method for heavy metal polluted river sediment, and belongs to the technical field of solid waste treatment. The ectopic treatment method comprises the following steps: detecting basic physicochemical parameters of the polluted bottom mud, total Cu and Zn, leaching toxicity and occurrence form; uniformly mixing the biomass to be screened and the polluted bottom mud according to the mass ratio of 1:1, and carrying out oxygen-limited co-pyrolysis to screen out the optimal co-pyrolysis biomass; respectively modifying parameters related to the co-pyrolysis process (the optimal co-pyrolysis biomass/polluted sediment mass ratio, the co-pyrolysis temperature and the co-pyrolysis time) to determine an optimal co-pyrolysis parameter combination; and carrying out oxygen-limited co-pyrolysis on the polluted substrate sludge and the optimal co-pyrolysis biomass under the optimal co-pyrolysis parameter combination. The method disclosed by the invention has the advantages that Cu and Zn polluted river sediment and biomass are subjected to co-pyrolysis, cu and Zn in the sediment are immobilized, the method is time-saving and efficient, the consumption cost is obviously lower, and the product can be used for removing Cd.
Description
Technical Field
The invention relates to a treatment and recycling method for polluted river sediment, in particular to an ex-situ treatment and recycling method for heavy metal (Cu and Zn) polluted river sediment, belonging to the technical field of solid waste treatment.
Background
With the great development of comprehensive treatment of water pollution, dredging has become a conventional means for treating endogenous pollution of sediment, so that a large amount of dredging sediment is also generated. At present, nearly half of dredging bottom mud in China can only be treated by adopting a storage yard stacking mode. The piled dredging bottom mud occupies land, pollutants such as heavy metals and the like which are enriched in the dredging bottom mud can pollute surrounding soil and underground water, and potential safety hazards such as dam break or mud biogas exist in a piled yard with higher piling. In particular, due to the influence of human activities (such as mining and agricultural activities), the enrichment degree of Cu and Zn in the sediment is obviously higher than that of other heavy metals, and the environment (such as groundwater and soil) and the human health of a stacking place are more easily damaged. Therefore, the method has important significance in developing treatment and research on the sediment of the Cu and Zn polluted river.
At present, the method for treating and disposing the sediment of the river channel polluted by heavy metals at different positions mainly comprises the following steps: heat treatment, leaching, electrochemical repair, phytoremediation, immobilization/stabilization, composting, and the like. Each treatment method has respective advantages and disadvantages, and a proper method is required to be selected according to a specific application scene in practical application. However, the existing method for treating and disposing the sediment of the heavy metal polluted river in an out-of-place manner has relatively limited sediment removal, and the removal speed cannot meet the rapid increase of the sediment removal output. Thus, there is a need to develop new treatment methods for heavy metal contaminated river sediment.
In the method for treating and disposing the sediment of the river channel polluted by the heavy metals in different positions, the heat treatment is an efficient and time-saving method for stabilizing and harmless heavy metals of the sediment. However, the traditional heat treatment method needs to consume higher energy and has higher cost when the river sediment is polluted by heavy metals in large scale. And the co-pyrolysis method widely applied to the field of biochar preparation in recent years is expected to provide a good solution for the immobilization of heavy metals in dredging bottom mud. The co-pyrolysis is a method for obtaining the biochar composite material by mixing two or more industrial and agricultural wastes (generally biomass) and then performing oxygen-limited pyrolysis. Earlier research shows that under the action of reduction reaction and the like after biomass and cadmium and lead polluted solid waste are co-pyrolyzed at a lower temperature, the occurrence form of heavy metal in the product is changed, and then the unstable state is changed into the stable state to be effectively fixed. Meanwhile, in the co-pyrolysis process, organic matters in biomass and sediment can be converted into biochar, so that the co-pyrolysis product has higher heavy metal adsorption capacity, and finally has certain recycling potential. Therefore, the river sediment polluted by Cu and Zn and biomass can be subjected to co-pyrolysis so as to immobilize Cu and Zn with higher activity in the sediment, and meanwhile, the obtained pyrolysis solid product is used as a water body heavy metal pollutant adsorbent.
Disclosure of Invention
In order to solve the defects of the prior art, the invention aims to provide a method for efficiently and cheaply treating and recycling river sediment polluted by heavy metals (Cu and Zn) in an ex-situ manner.
In order to achieve the above object, the present invention adopts the following technical scheme:
an ex-situ treatment disposal method for bottom mud of a heavy metal polluted river comprises the following steps:
(1) Detecting basic physical and chemical parameters of polluted bottom mud, total amount of Cu and Zn, leaching toxicity and occurrence form, wherein the basic physical and chemical parameters comprise: particle size, total organic carbon and pH;
(2) Uniformly mixing biomass to be screened and polluted bottom mud according to a mass ratio of 1:1, placing the mixture into a co-pyrolysis device, performing oxygen-limited co-pyrolysis on the mixture, detecting leaching concentrations of Cu and Zn in the obtained solid product, and determining the optimal co-pyrolysis biomass according to the change condition of leaching toxicity of Cu and Zn;
(3) Parameters involved in the co-pyrolysis process are respectively modified, and the parameters comprise: the optimal co-pyrolysis biomass/polluted bottom mud mass ratio, the co-pyrolysis temperature and the co-pyrolysis time, the rest specific processes are the same as the specific processes determined by the optimal co-pyrolysis biomass, the leaching concentration and occurrence form of Cu and Zn in the obtained solid product are detected, and the optimal co-pyrolysis parameter combination is determined based on the leaching toxicity and occurrence form of Cu and Zn, the pyrolysis cost and the disposal amount of the polluted bottom mud;
(4) And carrying out oxygen-limited co-pyrolysis on the polluted substrate sludge and the optimal co-pyrolysis biomass under the optimal co-pyrolysis parameter combination.
Preferably, in step (2), the biomass to be screened comprises: rice straw, wheat straw, corn straw, rape straw, coconut husk, peanut husk, rice husk, bamboo powder, pine dust and corncob.
Preferably, in step (2), the mixture is subjected to oxygen limited co-pyrolysis in particular as follows: high-purity nitrogen is introduced into the tubular furnace in advance at a rate of 1L/min for 20min, then the temperature is raised to 600 ℃ at a rate of 8 ℃/min, and the temperature is maintained for 100min, so that oxygen-limited co-pyrolysis is carried out, and a solid product is obtained.
Preferably, in step (3), the optimum co-pyrolysis biomass/contaminated sediment mass ratio is modified in the range of: 1:3, 1:2, 1:1, 2:1, 3:1; the co-pyrolysis temperature change range is: 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃; the co-pyrolysis time modification range is: 60min, 80min, 100min, 120min, 140min.
A resource utilization method of river sediment polluted by heavy metals comprises the following steps:
(1) Carrying out ex-situ treatment on heavy metal polluted river sediment according to any one of the above methods to obtain a co-pyrolysis solid product;
(2) Adjusting the pH value of the Cd polluted water body to be alkaline by using a NaOH solution;
(3) At room temperature, adding the co-pyrolysis solid product into an alkaline Cd polluted water body, and placing the water body in a reciprocating oscillator for adsorption; preferably, the oscillating speed of the reciprocating oscillator is 180rpm and the oscillating time is 24 hours.
The invention has the advantages that:
the method disclosed by the invention has the advantages that the Cu and Zn polluted river sediment and biomass are subjected to co-pyrolysis, the immobilization of Cu and Zn in the sediment is realized, the method is time-saving and efficient, the consumption cost is obviously lower than that of the traditional heat treatment method, and the method can be truly applied to the large-scale treatment of the Cu and Zn polluted river sediment, and has a good application prospect; meanwhile, the solid product obtained by co-pyrolysis is used for adsorbing and removing Cd pollutants in the water body, so that the sustainable development concept of treating wastes with the wastes is implemented, and finally, the reduction, harmlessness and recycling of the sludge of the river channel polluted by Cu and Zn are realized, thereby having important practical significance and engineering application value and being expected to have higher social, economic and environmental benefits.
Drawings
FIG. 1 is a schematic structural view of a co-pyrolysis apparatus;
FIG. 2 is a graph of the detection results of Cu leaching concentration in solid products obtained by co-pyrolysis of different biomass and contaminated substrate sludge;
FIG. 3 is a graph of the detection results of Zn leaching concentrations in solid products obtained by co-pyrolysis of different biomass and contaminated substrate sludge;
FIG. 4 is a graph of the detection results of Cu leaching concentration in solid products obtained by co-pyrolysis of pine wood chips and polluted bottom sludge at different mass mixing ratios;
FIG. 5 is a graph of the detection results of Zn leaching concentration in solid products obtained by co-pyrolysis of pine wood chips and polluted bottom sludge at different mass mixing ratios;
FIG. 6 is a graph of the detection results of Cu occurrence morphology in solid products obtained by co-pyrolysis of pine wood chips and polluted bottom sludge at different mass mixing ratios;
FIG. 7 is a graph of detection results of Zn occurrence forms in solid products obtained by co-pyrolysis of pine wood chips and polluted bottom sludge in different mass mixing ratios;
FIG. 8 is a graph of the detection results of Cu leaching concentration in solid products obtained by co-pyrolysis of pine wood chips and contaminated bottom sludge at different co-pyrolysis temperatures;
FIG. 9 is a graph of the detection results of Zn leaching concentration in solid products obtained by co-pyrolysis of pine wood chips and polluted bottom sludge at different co-pyrolysis temperatures;
FIG. 10 is a graph of the detection results of Cu occurrence morphology in solid products obtained by co-pyrolysis of pine wood chips and contaminated bottom sludge at different co-pyrolysis temperatures;
FIG. 11 is a graph of the detection results of Zn occurrence morphology in solid products obtained by co-pyrolysis of pine wood chips and polluted bottom sludge at different co-pyrolysis temperatures;
FIG. 12 is a graph of the detection results of Cu leaching concentration in solid products obtained by co-pyrolysis of pine wood chips and contaminated bottom sludge at different co-pyrolysis times;
FIG. 13 is a graph of the detection results of Zn leaching concentration in solid products obtained by co-pyrolysis of pine wood chips and polluted bottom sludge at different co-pyrolysis times;
FIG. 14 is a graph of the detection results of Cu occurrence morphology in solid products obtained by co-pyrolysis of pine wood chips and contaminated bottom sludge at different co-pyrolysis times;
FIG. 15 is a graph of the detection results of Zn occurrence patterns in solid products obtained by co-pyrolysis of pine wood chips and polluted bottom sludge at different co-pyrolysis times;
FIG. 16 is an SEM-EDS image of contaminated sediment;
FIG. 17 is an SEM-EDS image of a solid product obtained by co-pyrolysis of pine dust with contaminated sediment;
FIG. 18 is an XRD pattern of solid products from co-pyrolysis of pine wood chips with contaminated substrate sludge at different co-pyrolysis temperatures;
FIG. 19 is an XRD pattern of solid products obtained by co-pyrolysis of pine wood chips with contaminated substrate sludge at different co-pyrolysis times;
FIG. 20 is an XRD pattern of solid products obtained by co-pyrolysis of pine wood chips with contaminated substrate sludge at different mass mixing ratios;
FIG. 21 is a FTIR spectrum of a solid product obtained by co-pyrolysis of pine wood chips with contaminated substrate sludge at different co-pyrolysis temperatures;
FIG. 22 is a FTIR spectrum of solid products obtained by co-pyrolysis of pine dust and contaminated sediment at different co-pyrolysis times;
FIG. 23 is a FTIR spectrum of solid products obtained by co-pyrolysis of pine wood chips with contaminated substrate sludge at different mass mixing ratios;
FIG. 24 is an XPS spectrum of S in a solid product obtained by pyrolysis of contaminated sediment alone and in a solid product obtained by co-pyrolysis of pine dust with contaminated sediment;
FIG. 25 is an XPS spectrum of Zn in a solid product obtained by pyrolysis of contaminated sediment alone and in a solid product obtained by co-pyrolysis of pine dust and contaminated sediment;
FIG. 26 is an XPS spectrum of Cu in a solid product obtained by pyrolysis of contaminated sediment alone and in a solid product obtained by co-pyrolysis of pine dust and contaminated sediment;
FIG. 27 is a graph showing the effect of the initial pH of the solution on the adsorption of Cd by solid products obtained by co-pyrolysis of pine wood chips and contaminated substrate sludge;
FIG. 28 is a graph of a kinetic model of adsorption of Cd by solid products obtained by co-pyrolysis of pine wood chips and polluted bottom sludge;
FIG. 29 is a graph of a thermodynamic Freundlich model of the adsorption of Cd by solid products obtained by co-pyrolysis of pine wood chips and contaminated sediment;
FIG. 30 is a thermodynamic Langmuir model of Cd adsorption by solid products obtained by co-pyrolysis of pine wood chips and contaminated sediment;
FIG. 31 is an SEM image of the solid product of co-pyrolysis of pine dust and contaminated sediment after adsorption of Cd;
FIG. 32 is an XRD spectrum of a solid product obtained by co-pyrolysis of pine wood chips and contaminated sediment before and after adsorption of Cd;
FIG. 33 is a FTIR spectrum of a solid product obtained by co-pyrolysis of pine dust and contaminated sediment before and after adsorption of Cd;
FIG. 34 is XPS full spectrum before and after adsorption of Cd by solid products obtained by co-pyrolysis of pine dust and contaminated sediment;
FIG. 35 is an XPS spectrum of C1 s before and after adsorption of Cd by solid products obtained by co-pyrolysis of pine dust and contaminated sediment;
FIG. 36 is an XPS spectrum of O1 s before and after adsorption of Cd by solid products obtained by co-pyrolysis of pine dust and contaminated sediment;
FIG. 37 is an XPS spectrum of a solid product obtained by co-pyrolysis of pine dust and contaminated sediment for adsorption of Cd 3d before and after Cd.
Detailed Description
According to the method for treating and recycling the heavy metal polluted river sediment in the ex-situ manner, firstly, the Cu and Zn polluted sediment and biomass are subjected to co-pyrolysis so as to realize efficient immobilization of Cu and Zn in the dredging sediment, and then a solid product obtained by co-pyrolysis is used as an adsorbent for removing Cd in water.
The invention is described in detail below with reference to the drawings and the specific embodiments.
1. Basic physicochemical parameters of polluted river sediment and Cu and Zn pollution profile analysis
1. Basic physicochemical parameter determination of polluted river sediment
(1) pH of the bottom mud: the pH value of the sludge was measured according to the method specified in the method of measuring pH value of soil potential (HJ 962-2018).
(2) Total organic carbon of bottom mud: 1g of the sediment is leached by using 10mL of hydrochloric acid solution with the concentration of 1mol/L, the stirring speed is 180rpm, the leaching time is 16 hours, so that inorganic carbon in the sediment is removed, and then the total organic carbon content of the sediment is analyzed by using an elemental analyzer.
(3) Sediment particle size: organic matters, carbonates and the like in the bottom mud are removed by using a hydrogen peroxide solution with the volume concentration of 30 percent and a hydrochloric acid solution with the volume concentration of 10 percent in sequence, then sodium hexametaphosphate is added as a dispersing agent, and then the granularity composition of the bottom mud is measured by using a laser granularity meter.
2. Analysis of pollution conditions of Cu and Zn of polluted river sediment
(1) And (3) measuring the total amount of Cu and Zn in the bottom mud: the total amount of Cu and Zn in the sediment was analyzed according to the method specified in inductively coupled plasma Mass Spectrometry (DB/T4435-2021), which measures the total amount of 14 metal elements in soil and sediment.
(2) Cu and Zn leaching toxicity: the leaching toxicity of the sediment Cu and Zn was measured according to the method specified in the method of leaching toxicity of solid waste acetic acid buffer solution method (HJ/T300-2007).
(3) Sediment Cu and Zn occurrence forms: and analyzing the occurrence forms of Cu and Zn in the sediment according to the method specified in the soil and sediment 13 trace element form sequence extraction program.
3. Analysis results
Taking the polluted sediment obtained from a certain coastal river channel in the tobacco table of Shandong province as an example, the basic physical and chemical parameters of the polluted sediment and the pollution conditions of Cu and Zn are specifically as follows:
TABLE 1 basic physicochemical parameters of polluted bottom sludge and measurement results of Cu and Zn pollution conditions
From the measurement results listed in table 1, it can be found that:
(1) The Cu and Zn contents in the polluted sediment are all higher than the risk screening value of the soil pollution risk management and control standard (trial) of soil environment quality agricultural land (GB 15618-2018), and the polluted sediment has a certain ecological risk;
(2) The leaching concentration (2.91 mg/L) of Zn in the polluted bottom mud exceeds the first-class standard (2 mg/L) of the second-class pollutants in the integrated wastewater discharge standard (GB 8978-1996), but is lower than the standard limit value (100 mg/L) in the integrated hazardous waste identification standard leaching toxicity identification (GB 5085.3-2007), and the leaching concentration (0.08 mg/L) of Cu is lower than the first-class standard (0.5 mg/L) of the second-class pollutants in the integrated wastewater discharge standard (GB 8978-1996), so the polluted bottom mud is class II general solid waste;
(3) The morphological analysis of heavy metal occurrence shows that Zn in the polluted bottom mud is mainly in an F1 state (with the proportion of 62.40%), and Cu is mainly in an F3 state (with the proportion of 53.24%).
2. Optimal co-pyrolysis biomass determination
The biomass to be screened (rice straw, wheat straw, corn straw, rape straw, coconut husk, peanut shell, rice husk, bamboo powder, pine wood dust and corncob) is sieved by a 100-mesh sieve, the polluted substrate sludge is sieved by an 80-mesh sieve, the biomass to be screened and the polluted substrate sludge are uniformly mixed according to the mass ratio of 1:1, and 6g of the mixture is taken and placed in a co-pyrolysis device shown in figure 1 (specifically placed in a tubular furnace).
Introducing high-purity nitrogen (purity is more than 99.99%) into a tube furnace at a rate of 1L/min in advance, and maintaining for 20min to remove oxygen in the quartz tube; then heating to 600 ℃ at a speed of 8 ℃/min, maintaining for 100min, and performing oxygen-limited co-pyrolysis to obtain a solid product; after the solid product in the quartz tube is cooled to room temperature, the solid product is taken out, the leaching toxicity of Cu and Zn in the obtained solid product is analyzed, and the leaching toxicity of Cu and Zn is measured according to the method described in acetic acid buffer solution method (HJ/T300-2007) of solid waste leaching toxicity leaching method. The detection results of the leaching concentration of Cu and Zn in the obtained solid product are respectively shown in fig. 2 and 3.
And determining the optimal co-pyrolysis biomass according to the change condition of Cu and Zn leaching toxicity in the solid product obtained by co-pyrolysis.
As can be seen from fig. 2 and fig. 3, after the pine wood scraps and the polluted bottom mud are co-pyrolyzed, the leaching concentration of Cu and Zn in the obtained solid product is most obviously reduced, which is obviously lower than the leaching concentration of Cu and Zn in the polluted bottom mud and is also obviously lower than the first-level standard of the second type of pollutants in the integrated wastewater discharge standard (GB 8978-1996). Thus, pine wood chips are determined as the best co-pyrolyzed biomass for this contaminated substrate sludge.
3. Determination of optimal parameters for a co-pyrolysis process
On the basis of determining the optimal co-pyrolysis biomass, parameters involved in the co-pyrolysis process, such as mass ratio of pine dust to polluted sediment, co-pyrolysis temperature and co-pyrolysis time, are changed, the rest specific processes are the same as the specific processes determined by the optimal co-pyrolysis biomass, and finally, the optimal co-pyrolysis parameter combination is determined based on leaching toxicity and occurrence form of Cu and Zn in the solid product.
1. Determination of optimal mass ratio of pine wood dust/polluted bottom mud
Uniformly mixing pine wood scraps passing through a 100-mesh sieve and polluted substrate sludge passing through an 80-mesh sieve according to the mass ratio of 1:3, 1:2, 1:1, 2:1 and 3:1 respectively, and placing 6g of the mixture into a co-pyrolysis device shown in figure 1.
High-purity nitrogen (purity is more than 99.99%) is introduced into the tube furnace in advance according to the speed of 1L/min, and the tube furnace is maintained for 20min; then heating to 600 ℃ at a speed of 8 ℃/min and maintaining for 100min to obtain a solid product; and after the solid product in the quartz tube is cooled to room temperature, taking out the solid product, and analyzing the leaching toxicity and occurrence form of Cu and Zn in the obtained solid product, wherein the leaching toxicity of Cu and Zn is measured according to a method specified in a solid waste leaching toxicity leaching method acetic acid buffer solution method (HJ/T300-2007), and the occurrence form of Cu and Zn is measured according to a method specified in a soil and sediment 13 trace element form sequential extraction procedure.
The detection results of the leaching concentration of Cu and Zn in the obtained solid product are respectively shown in fig. 4 and 5, and the detection results of the occurrence forms of Cu and Zn are respectively shown in fig. 6 and 7.
2. Determination of optimal Copyrolysis temperature
The pine wood scraps passing through the 100-mesh sieve and the polluted substrate sludge passing through the 80-mesh sieve are uniformly mixed according to the mass ratio of 1:1, and 6g of the mixture is placed in a co-pyrolysis device shown in fig. 1.
High-purity nitrogen (purity is more than 99.99%) is introduced into the tube furnace in advance according to the speed of 1L/min, and the tube furnace is maintained for 20min; then respectively heating to 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃ at a speed of 8 ℃/min, and maintaining for 100min to obtain a solid product; and after the solid product in the quartz tube is cooled to room temperature, taking out the solid product, and analyzing the leaching toxicity and occurrence form of Cu and Zn in the obtained solid product.
The detection results of the leaching concentrations of Cu and Zn in the obtained solid product are respectively shown in fig. 8 and 9, and the detection results of the occurrence forms of Cu and Zn are respectively shown in fig. 10 and 11.
3. Co-pyrolysis time
The pine wood scraps passing through the 100-mesh sieve and the polluted substrate sludge passing through the 80-mesh sieve are uniformly mixed according to the mass ratio of 1:1, and 6g of the mixture is placed in a co-pyrolysis device shown in fig. 1.
High-purity nitrogen (purity is more than 99.99%) is introduced into the tube furnace in advance according to the speed of 1L/min, and the tube furnace is maintained for 20min; then heating to 600 ℃ at a speed of 8 ℃/min, and respectively maintaining for 60min, 80min, 100min, 120min and 140min to obtain a solid product; and after the solid product in the quartz tube is cooled to room temperature, taking out the solid product, and analyzing the leaching toxicity and occurrence form of Cu and Zn in the obtained solid product.
The detection results of the leaching concentrations of Cu and Zn in the obtained solid product are shown in fig. 12 and 13, and the detection results of the occurrence forms of Cu and Zn are shown in fig. 14 and 15.
The test results shown in fig. 4 to 15 show that the stability of Cu and Zn in the solid product is enhanced (fig. 6, 7, 10, 11, 14, and 15) and the leaching toxicity is remarkably reduced (fig. 4, 5, 8, 9, 12, and 13) with the increase of the co-pyrolysis temperature and the co-pyrolysis time and the increase of the addition proportion of pine dust, and the immobilization efficiency is improved.
Based on comprehensive consideration of immobilization efficiency, pyrolysis cost and polluted sediment disposal amount, pyrolysis temperature is 600 ℃, pyrolysis time is 100min, and the mass ratio of pine wood scraps/polluted sediment is 1:1, which is the optimal co-pyrolysis parameter combination.
Under the combination of the optimal co-pyrolysis parameters, carrying out oxygen-limited co-pyrolysis on a large amount of polluted sediment and pine wood scraps obtained from the same coastal river channel, wherein the leaching concentration of Cu and Zn in the obtained solid product is 2.54 mug/L and ND (not detected) respectively, and the leaching concentration meets the first-level standard of the second type of pollutants in the integrated wastewater discharge standard (GB 8978-1996).
4. Mechanism analysis of disposal of Cu and Zn polluted bottom mud by biomass co-pyrolysis
And (3) comprehensively utilizing an SEM-EDS, XRD, FTIR, XPS technology to characterize the surface microscopic morphology, crystal structure and mineral composition, surface functional groups and surface element valence states of the polluted substrate sludge and a solid product obtained by co-pyrolysis of biomass and the polluted substrate sludge so as to reveal the mechanism of the co-pyrolysis immobilized polluted substrate sludge Cu and Zn.
1. Microscopic morphology of solid product obtained by co-pyrolysis of polluted bottom mud and biomass and polluted bottom mud
Taking the solid product obtained by co-pyrolysis under the co-pyrolysis parameter combination of pine wood scraps/polluted substrate sludge with the mass ratio of 1:1, the pyrolysis temperature of 600 ℃ and the pyrolysis time of 100 min.
SEM-EDS images of the contaminated sediment and the solid product are shown in fig. 16 and 17, respectively.
As can be seen from fig. 16, the polluted sludge exhibits a porous structure, and EDS analysis shows that the surface elements of the polluted sludge are mainly composed of O, si, fe and Al.
As can be seen from fig. 17, the solid product exhibits a more developed pore structure, since the high temperature promotes the decomposition of the contaminated sediment particles, and EDS analysis shows that the surface elements of the solid product consist mainly of C, O, si and Ca.
Surface element and morphology analysis showed that biomass was converted to biochar during pyrolysis.
2. Crystal structure and mineral composition of solid product obtained by co-pyrolysis of polluted substrate sludge and biomass and polluted substrate sludge
Taking solid products obtained by the polluted bottom mud and the pine wood chips at different co-pyrolysis temperatures, solid products obtained at different co-pyrolysis times and solid products obtained at different mass mixing ratios.
The X-ray diffraction (XRD) patterns of these solid products and the contaminated sediment are shown in fig. 18, 19 and 20, respectively.
It can be seen from FIGS. 18, 19 and 20 that after pyrolysis, znCl in the solid product 2 Characteristic peak intensity is reduced, and new characteristic peak (Zn) with higher stability 2 (PO 4 )OH、ZnSiO 3 And ZnAl 2 S 4 ) But appear in the solid product, which demonstrates that the stability is enhanced by the morphological transformation of Zn that occurs after pyrolysis. However, after pyrolysis, no significant change in the characteristic peak of Cu was observed.
3. Surface functional groups of solid products obtained by co-pyrolysis of polluted bottom sludge and biomass and polluted bottom sludge
Taking solid products obtained by the polluted bottom mud and the pine wood chips at different co-pyrolysis temperatures, solid products obtained at different co-pyrolysis times and solid products obtained at different mass mixing ratios.
Fourier transform infrared absorption spectra (FTIR) of these solid products and contaminated substrate sludge are shown in fig. 21, 22 and 23, respectively.
As can be seen from FIGS. 21, 22 and 23, the contaminated substrate sludge contains a plurality of functionalities such as OH, C-OH, C≡ N, C = O, C-O, CH, etcAnd (3) energy groups. After pyrolysis, the intensity of most functional groups is reduced, mainly due to pyrolysis promoting the conversion of hydrocarbon species into gases (CO 2 、CH 4 Etc.), biomass oil, and the like. Meanwhile, the strength of-OH in the solid product is greatly reduced due to the evaporation of the bound water in the polluted bottom mud. Moreover, some new metal oxide groups are present in the solid product, which is mainly related to the transformation of the metal-loaded morphology during pyrolysis.
4. Mechanism for reducing ecological risks of Cu and Zn in polluted bottom mud by biomass co-pyrolysis
Based on XRD analysis results, the soluble ZnCl in the polluted bottom mud 2 After co-pyrolysis, the phosphate compound is converted into a phosphate compound which is more stable and insoluble in water, and the specific reaction is as follows:
the valence states of S, zn and Cu in the polluted bottom mud, a solid product obtained by single pyrolysis (pyrolysis temperature 600 ℃ C. And pyrolysis time 100 min) of the polluted bottom mud, and a solid product (S@BC) obtained by co-pyrolysis (mass ratio of pine wood chips to the polluted bottom mud is 1:1, pyrolysis temperature 600 ℃ C. And pyrolysis time 100 min) of the pine wood chips and the polluted bottom mud are analyzed in one step.
The XPS of S in the solid product (S@BC) obtained by the co-pyrolysis of the polluted bottom mud (DS), the solid product (DS@A) obtained by the separate pyrolysis of the polluted bottom mud, the pine wood dust and the polluted bottom mud is shown in FIG. 24, the XPS of Zn is shown in FIG. 25, and the XPS of Cu is shown in FIG. 26.
As can be seen from FIG. 24, the sulfate ratio of the solid product obtained by CO-pyrolysis of pine dust and contaminated sludge is reduced and the sulfide ratio is increased, compared to the solid product obtained by pyrolysis of contaminated sludge and contaminated sludge alone, mainly due to the reducing gases (e.g., CO 2 、H 2 、C 2 H 4 ) The sulfate is reduced to sulfide.
As can be seen from FIG. 25, the Zn valence state in the solid product obtained by co-pyrolysis of pine wood chips and contaminated bottom sludge was not significantly changed as compared with the solid product obtained by pyrolysis of contaminated bottom sludge and contaminated bottom sludge alone, but XRD analysis confirmed that ZnAl was present in the solid product obtained by co-pyrolysis of pine wood chips and contaminated bottom sludge 2 S 4 Presumably due to the binding of sulfide formed by the reduction to zinc to produce zinc sulfide.
As can be seen from fig. 26, cu (II) in the solid product obtained by co-pyrolysis of pine dust and contaminated sludge is disappeared and all is converted into Cu (I) and Cu (0) compared with the solid product obtained by pyrolysis of contaminated sludge and contaminated sludge alone, which indicates that the valence state of Cu is changed during co-pyrolysis.
Besides reduction and conversion, the high temperature is also favorable for the growth of metal mineral crystals, so that the stabilization of polluted bottom sludge Cu and Zn is promoted. Meanwhile, the organic matters are converted into the biochar to promote the stability of Cu and Zn, and after the organic matters are converted into the hard biochar, cu and Zn combined with the organic matters in the polluted bottom mud can be wrapped, and meanwhile, the biochar can be used for immobilizing the Cu and Zn through adsorption.
5. Behavior and mechanism of solid product obtained by co-pyrolysis of biomass and polluted sediment for adsorbing Cd in water body
1. Behavior of solid product obtained by co-pyrolysis of biomass and polluted sediment in adsorption of Cd in water body
Taking a solid product obtained by co-pyrolysis of the polluted bottom mud and the pine wood scraps under the co-pyrolysis parameter combination of the pine wood scraps/polluted bottom mud with the mass ratio of 1:1, the pyrolysis temperature of 600 ℃ and the pyrolysis time of 100min as a mode adsorbent, and researching the adsorption behavior of the solid product on Cd.
20mL of Cd solution (containing 0.01mol/L NaNO) with initial concentration of 100mg/L was taken 3 To maintain ionic strength of the adsorption solution) was placed in a 50mL centrifuge tube with HNO at a concentration of 0.1mol/L 3 The pH values of the adsorption solution are respectively adjusted to 5, 6, 7, 8, 9, 10, 11 and 12 by the solution and NaOH solution with the concentration of 0.1mol/L, 0.02g of the solid product is added at room temperature (25 ℃) and is placed in a reciprocating oscillator for adsorption, the oscillation speed is 180rpm, and the oscillation time is 24 hours; and (3) passing the adsorbed Cd solution through a cellulose acetate filter membrane with the aperture of 0.45 mu m, measuring the concentration of residual Cd in the solution by using an inductively coupled plasma spectrometer, and calculating the removal rate of Cd and the adsorption performance of the solid product based on the concentration difference value of Cd in the solution before and after adsorption, wherein the calculation formula is as follows:
wherein, the liquid crystal display device comprises a liquid crystal display device,Q e for the equilibrium adsorption amount (mg/g) of the adsorbent,the removal rate (%) of Cd,C 0 to the initial concentration (mg/L) of Cd before adsorption,C e for the equilibrium adsorption concentration (mg/L) of Cd after adsorption,Vthe volume of the adsorption solution (mL), m is the mass of the adsorbent (g).
The adsorption kinetics behavior of the adsorbent is fitted with a pseudo first-order kinetics model (PFO model) and a pseudo second-order kinetics model (PSO model), and the adsorption isotherms of the adsorbent are fitted with a Langmuir model and a Freundlich model, and the calculation method of each model is as follows:
PFO model:
PSO model:
langmuir model:
freundlich model:
wherein, the liquid crystal display device comprises a liquid crystal display device,Q e for the equilibrium adsorption amount (mg/g) of the adsorbent,Q t is thattThe adsorption amount (mg/g) of the adsorbent at the moment,Q max for the maximum theoretical adsorption capacity (mg/g) of the adsorbent,k 1 is a first order kinetic constant (min -1 ），k 2 Is a second order kinetic constant (g/(mg.min)),K L for the adsorption constant (L/mg),K F for the Freundlich constant,nis the Freundlich intensity parameter.
The results of the detection of the maximum adsorption amount of the adsorbent at different initial pH values are shown in FIG. 27. As can be seen from FIG. 27, the increase of the pH value of the adsorption solution is favorable for the increase of the adsorption performance of the adsorbent, and the maximum adsorption amount of the adsorbent can reach 171.31mg/g when the pH value of the adsorption solution is 12.
The kinetic model of the adsorbent for adsorbing Cd is shown in FIG. 28. As can be seen from fig. 28, the simulation effect of the PSO model is superior to that of the PFO model, which indicates that the process of limiting the adsorption of Cd by the adsorbent is chemisorption.
The thermodynamic model of the adsorbent for adsorbing Cd is shown in fig. 29 and 30. As can be seen from fig. 29 and 30, the simulation effect of the Langmuir model is superior to that of the Freundlich model, which suggests that the adsorption of Cd by the adsorbent is mainly a single-layer adsorption process on a heterogeneous surface.
2. Mechanism for adsorbing Cd in water body by solid product obtained by co-pyrolysis of biomass and polluted bottom mud
Taking a solid product obtained by co-pyrolysis of the polluted bottom mud and the pine wood scraps under the co-pyrolysis parameter combination of the pine wood scraps/polluted bottom mud with the mass ratio of 1:1, the pyrolysis temperature of 600 ℃ and the pyrolysis time of 100min as a mode adsorbent, and researching the adsorption mechanism of the solid product on Cd.
And (3) comprehensively utilizing an SEM ‒ EDS, FTIR, XRD, XPS technology, analyzing the relevant physicochemical properties of the adsorbent before and after adsorbing Cd so as to reveal the mechanism of the adsorbent for adsorbing Cd.
SEM-EDS images of the adsorbent after adsorption of Cd are shown in FIG. 31. XRD patterns of the polluted bottom mud (DS), the solid product obtained by co-pyrolysis of pine wood scraps and the polluted bottom mud before adsorbing Cd (S@BC) and the solid product obtained by co-pyrolysis of the pine wood scraps and the polluted bottom mud after adsorbing Cd (S@BC-Cd) are shown in FIG. 32, and FTIR patterns are shown in FIG. 33.
As can be seen from FIG. 31, a large number of chain-like particles appear on the surface of S@BC-Cd, and EDS analysis shows that the particles contain a higher content of Cd, which indicates that the Cd is successfully adsorbed and immobilized by S@BC.
As can be seen from FIG. 32, cdCO 3 Characteristic peaks of (C) appear on a spectrogram of S@BC-Cd, but do not appear in the spectrogram of S@BC, which proves that S@BC can be prepared as CdCO 3 In the form of (2) adsorbing and fixing Cd (II) in the water body.
As can be seen from FIG. 33, the metal-O characteristic peak appears on the surface of S@BC-Cd, presumably the Cd-O peak.
Further analysis was performed on S@BC and S@BC-Cd using XPS.
The full spectra of S@BC and S@BC-Cd are shown in FIG. 34, and the XPS spectra of C1 s, O1 s and Cd 3d are shown in FIG. 35, FIG. 36 and FIG. 37, respectively.
As can be seen from FIGS. 34, 35 and 36, the oxygen-containing functional groups such as C-O, -COOH and the like on the surface of S@BC-Cd are displaced, and the proportion of the functional groups is reduced, so that the phenomena indicate that the functional groups and Cd (II) undergo a complexation reaction, and the immobilization of Cd (II) is facilitated. As can be seen from FIG. 37, cd is adsorbed in the form of Cd-O, and the possible binding forms are predicted to be COO-Cd, O-Cd, cdCO based on the XRD analysis result 3 。
In summary, the main mechanism of adsorption of Cd (II) by the solid product obtained by co-pyrolysis of pine wood scraps and polluted substrate sludge is as follows: solid products obtained by co-pyrolysis of pine wood chips and polluted substrate sludge induce Cd (II) to form CdCO 3 Precipitation, or pine dust and dirtThe oxygen-containing functional group on the surface of the solid product obtained by co-pyrolysis of the dyeing substrate sludge is subjected to complexation reaction with Cd (II) to be adsorbed.
It should be noted that the above examples are only examples for clearly illustrating the present invention, and are not limiting to the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. Not all embodiments are exhaustive. All obvious changes or modifications which are obvious from the technical proposal of the invention are still within the protection scope of the invention.
Claims (8)
1. The ectopic treatment disposal method of the heavy metal polluted river sediment is characterized by comprising the following steps of:
(1) Detecting basic physical and chemical parameters of polluted bottom mud, total amount of Cu and Zn, leaching toxicity and occurrence form, wherein the basic physical and chemical parameters comprise: particle size, total organic carbon and pH;
(2) Uniformly mixing biomass to be screened and polluted bottom mud according to a mass ratio of 1:1, placing the mixture into a co-pyrolysis device, performing oxygen-limited co-pyrolysis on the mixture, detecting leaching concentrations of Cu and Zn in the obtained solid product, and determining the optimal co-pyrolysis biomass according to the change condition of leaching toxicity of Cu and Zn;
(3) Parameters involved in the co-pyrolysis process are respectively modified, and the parameters comprise: the optimal co-pyrolysis biomass/polluted bottom mud mass ratio, the co-pyrolysis temperature and the co-pyrolysis time, the rest specific processes are the same as the specific processes determined by the optimal co-pyrolysis biomass, the leaching concentration and occurrence form of Cu and Zn in the obtained solid product are detected, and the optimal co-pyrolysis parameter combination is determined based on the leaching toxicity and occurrence form of Cu and Zn, the pyrolysis cost and the disposal amount of the polluted bottom mud;
(4) And carrying out oxygen-limited co-pyrolysis on the polluted substrate sludge and the optimal co-pyrolysis biomass under the optimal co-pyrolysis parameter combination.
2. The method for the ex-situ treatment of heavy metal contaminated river sediment according to claim 1, wherein in step (2), the biomass to be screened comprises: rice straw, wheat straw, corn straw, rape straw, coconut husk, peanut husk, rice husk, bamboo powder, pine dust and corncob.
3. The method for the ex-situ treatment and disposal of heavy metal contaminated river sediment according to claim 1, wherein in the step (2), the method for performing oxygen-limited co-pyrolysis on the mixture is specifically as follows:
introducing nitrogen with purity of more than 99.99% into a tube furnace at a rate of 1L/min in advance, maintaining for 20min, then heating to 600 ℃ at a rate of 8 ℃/min, maintaining for 100min, and performing oxygen limiting co-pyrolysis to obtain a solid product.
4. The method for the ex-situ treatment of heavy metal contaminated river sediment according to claim 1, wherein in the step (3), the modification range of the optimal co-pyrolysis biomass/contaminated sediment mass ratio is as follows: 1:3, 1:2, 1:1, 2:1, 3:1.
5. The method for the ex-situ treatment of heavy metal contaminated river sediment according to claim 1, wherein in the step (3), the co-pyrolysis temperature modification range is: 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃.
6. The method for the ex-situ treatment of heavy metal contaminated river sediment according to claim 1, wherein in the step (3), the co-pyrolysis time is changed in the range of: 60min, 80min, 100min, 120min, 140min.
7. The resource utilization method of the river sediment polluted by the heavy metal is characterized by comprising the following steps of:
(1) Carrying out ex-situ treatment on heavy metal polluted river sediment according to the method of any one of claims 1 to 6 to obtain a co-pyrolysis solid product;
(2) Adjusting the pH value of the Cd polluted water body to be alkaline by using a NaOH solution;
(3) At room temperature, adding the co-pyrolysis solid product into an alkaline Cd polluted water body, and placing the water body in a reciprocating oscillator for adsorption.
8. The method for recycling the heavy metal polluted river sediment according to claim 7, wherein in the step (3), the oscillating speed of the reciprocating oscillator is 180rpm, and the oscillating time is 24 hours.
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| CN112919754A (en) * | 2021-01-21 | 2021-06-08 | 东南大学 | Method for preparing biochar and solidifying heavy metal by virtue of pyrolysis of sludge coupled biomass |
| CN115925210A (en) * | 2022-12-26 | 2023-04-07 | 华中科技大学 | Method for preparing sludge-based biochar and reducing heavy metal toxicity |
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| CN106669603A (en) * | 2016-12-07 | 2017-05-17 | 广东工业大学 | Preparation method and application of magnesium oxide-rice husk biological carbon composite material |
| CN112457853A (en) * | 2020-11-25 | 2021-03-09 | 河南省科学院高新技术研究中心 | Zinc-rich biochar, preparation method thereof and application of zinc-rich biochar in passivation and remediation of heavy metal contaminated soil |
| CN112919754A (en) * | 2021-01-21 | 2021-06-08 | 东南大学 | Method for preparing biochar and solidifying heavy metal by virtue of pyrolysis of sludge coupled biomass |
| CN115925210A (en) * | 2022-12-26 | 2023-04-07 | 华中科技大学 | Method for preparing sludge-based biochar and reducing heavy metal toxicity |
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| CN117756371A (en) * | 2023-12-15 | 2024-03-26 | 中国科学院重庆绿色智能技术研究院 | Chemical conditioning and dewatering control method for reservoir sediment sludge |
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