CN114275984B - Electrochemical leaching lead recovery method for lead-containing sludge - Google Patents
Electrochemical leaching lead recovery method for lead-containing sludge Download PDFInfo
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Abstract
The invention provides a method for recovering lead from lead-containing sludge by electrochemical leaching, which comprises the steps of oxidizing and degrading partial organic matters in the sludge by using strong-oxidizing hydroxyl radicals (. OH) generated by a Fenton reaction, destroying sludge flocs to desorb lead from the sludge floc structure, performing electrochemical leaching to electrically migrate the lead into electrolyte under the action of an electric field, recovering the lead by using a chemical precipitation method and an electrolytic method, and electrolyzing after impurity removal to obtain electrolytic lead with the purity of 99.997%. The method can fully remove and recover heavy metal lead in the lead-containing industrial sludge, the recovery rate of the lead can reach more than 90 percent, the harm of the sludge to the environment is reduced, the recovery and the resource of the lead are fully realized finally, meanwhile, leacheate can be discharged harmlessly after chemical precipitation, and the reduction of the sludge can be realized through electroosmosis dehydration treatment.
Description
Technical Field
The invention relates to the technical field of industrial sludge treatment, in particular to a method for recovering lead from lead-containing sludge by electrochemical leaching.
Background
Industrial sludge generally has the following characteristics: complex components, high content of toxic and harmful substances, dispersed sources, high yield and high requirement on harmlessness. Industrial sludge often contains high heavy metals, so that secondary pollution may be caused in the sludge disposal process, and certain difficulty is brought to harmless subsequent disposal of the sludge.
At present, the industrial sludge treatment method in China mainly comprises a thermochemical treatment technology, composting, anaerobic digestion drying, stabilization/solidification and the like, and the final treatment scheme mainly comprises the following steps: land utilization, building material utilization, incineration, landfill, discarding and the like. Among them, stabilization/solidification is an important means for treating heavy metal waste, but it is only a temporary isolation of harmful elements in sludge, and cannot essentially solve the problem of heavy metal hazard. The landfill method has simple technology, small investment and low cost, but is easy to cause pollution to soil and underground water and has large occupied area; the sludge after composting can be used for soil remediation, landscaping and the like, but the secondary pollution problem cannot be effectively solved; in the incineration method, the sludge contains organic matters in a certain proportion more or less, toxic gases such as dioxin, sulfur dioxide and the like can be generated in the incineration process, secondary pollution is easily caused due to poor treatment, the ecological environment is affected, and the investment cost, the operation cost and the technical difficulty are high. At present, the domestic technology for recycling heavy metal in sludge is not mature enough, and the secondary pollution problem and resource recycling are urgently needed to be solved.
At present, the heavy metal recovery technology of industrial sludge mainly utilizes a microbiological method to adsorb and reduce the content of heavy metal in the sludge, a chemical agent addition method to separate the heavy metal in the sludge and an electrochemical method to remove the heavy metal. Among them, the biological method has low efficiency, and the chemical agent separation method easily generates a large amount of waste water or waste residues. The electrochemical method mainly uses an electric restoration technology, has simple principle, high selectivity on different metals and short treatment time, can obtain high-purity target metal products, has good prospect, is widely applied to the restoration of saline-alkali soil, heavy metal and organic polluted soil and has more remarkable effect, but has less application to the removal and recovery of heavy metal ions in sludge. For example, the prior art discloses an electrochemical oxidation-elution Cr contaminated soil treatment integrated device and a treatment method, which mainly concern about the elution of pollutants, do not concern about the recovery part of heavy metals (the content of the heavy metals is too low), and have obvious difference between the soil treatment conditions and the key technical parameters of the lead-containing industrial sludge treatment. How to improve the reduction ratio of the sludge to electrochemically elute the heavy metals and shorten the treatment time is an important research direction for removing the heavy metals from the sludge, and meanwhile, lead is taken as an important metal resource, so that the method for recovering the lead from the lead-containing sludge is short of an effective technology at present.
Based on the technical defects of the current method for recovering lead from the lead-containing sludge, improvement on the method is needed.
Disclosure of Invention
In view of the above, the present invention provides a method for recovering lead by electrochemical leaching of lead-containing sludge, so as to solve or at least partially solve the technical problems in the prior art.
The invention provides a method for recovering lead from lead-containing sludge by electrochemical leaching, which comprises the following steps:
adding acid into the lead-containing sludge to adjust the pH value to 2-4, adding ferrous ions, and then adding hydrogen peroxide to enable the lead-containing sludge to generate a Fenton reaction;
carrying out electrochemical leaching on the lead-containing sludge subjected to the Fenton reaction to enable lead ions in the lead-containing sludge to enter electrolyte on one side of a cathode;
adjusting the pH value of the electrolyte to 5-6, filtering, and collecting filtrate;
adding carbonate into the filtrate to generate lead carbonate precipitate, adding acid into the lead carbonate precipitate to dissolve the lead carbonate precipitate, and preparing lead by an electrolytic method.
Preferably, the method for recovering lead by electrochemical leaching of lead-containing sludge comprises the following steps of performing electrochemical leaching on the lead-containing sludge subjected to the Fenton reaction, so that lead ions in the lead-containing sludge enter the electrolyte on the cathode side:
providing an electrolytic cell and a power supply, wherein an anode and a cathode are arranged in the electrolytic cell, and electrolyte is placed between the cathode and the inner wall of the electrolytic cell;
the cathode is of a porous structure;
the electrolyte is a citric acid solution with the pH value of 3.5-4.5;
during electrochemical leaching, lead-containing sludge is placed between the cathode and the anode, the cathode of the power supply is connected with the cathode, and the anode of the power supply is connected with the anode.
Preferably, in the method for recovering lead by electrochemical leaching of lead-containing sludge, the cathode is a porous titanium electrode plate, and the porosity of the cathode is 25-60%.
Preferably, in the method for recovering lead by electrochemical leaching of lead-containing sludge, the anode is a titanium-based iridium dioxide coating electrode, and the porosity of the anode is 10-50%.
Preferably, in the method for recovering lead by electrochemical leaching of the lead-containing sludge, the electrochemical leaching process is carried out under the condition of constant or intermittent voltage with the voltage gradient of 1.0-2.0V/cm;
the time of the electrochemical leaching is 10.0-20.0h/cm according to the length of the lead-containing sludge between the anode and the cathode;
in the electrochemical leaching process, the anode moves 2-10cm towards the cathode every 3.0-10.0 h until the distance between the anode and the cathode is 2-6 cm, and then the anode does not move, and the electrochemical leaching is stopped after the electrochemical leaching is continued for 4-10 h.
Preferably, in the method for recovering lead by electrochemical leaching of the lead-containing sludge, the length of the lead-containing sludge between the anode and the cathode is 3-20 cm.
Preferably, in the method for recovering lead by electrochemical leaching of lead-containing sludge, the acid is nitric acid, the addition amount of hydrogen peroxide in each kg of lead-containing sludge is 40-100 g, and the addition amount of ferrous ions in each kg of lead-containing sludge is 0-100 mg.
Preferably, the method for recovering lead by electrochemical leaching of lead-containing sludge further comprises: and performing electroosmosis dehydration on the lead-containing sludge subjected to electrochemical leaching.
Preferably, the method for recovering lead from lead-containing sludge by electrochemical leaching adopts an electric field intensity of 25-45V/cm to carry out electroosmotic dehydration on the lead-containing sludge after electrochemical leaching.
Compared with the prior art, the electrochemical leaching lead recovery method of the lead-containing sludge has the following beneficial effects:
according to the method for recovering lead from the lead-containing sludge by electrochemical leaching, a part of organic matters in the sludge are oxidized and degraded by strong oxidizing hydroxyl radicals (. OH) generated by Fenton reaction, sludge flocs are damaged to desorb lead from the sludge flocs structure, the lead is electrolyzed and transferred into electrolyte under the action of an electric field by electrochemical leaching, then the lead is recovered by a chemical precipitation method and an electrolysis method, and the electrolytic lead with the purity of 99.997 percent is obtained by electrolysis after impurity removal. The method can fully remove and recover heavy metal lead in the lead-containing industrial sludge, the recovery rate of the lead can reach more than 90 percent, the harm of the sludge to the environment is reduced, the recovery and the resource of the lead are fully realized finally, meanwhile, leacheate can be discharged harmlessly after chemical precipitation, and the reduction of the sludge can be realized through electroosmosis dehydration treatment.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
FIG. 1 is a schematic view of an electrochemical leaching apparatus according to the present invention;
FIG. 2 is a schematic flow chart of the lead recovery method by electrochemical leaching of the lead-containing sludge according to the present invention;
FIG. 3 is a graph showing the removal rate of lead and the remaining proportion of lead in various forms in the lead-containing sludge after electrochemical leaching according to the method in example 1 and comparative examples 1 to 3 of the present invention;
FIG. 4 is an SEM photograph of a lead carbonate precipitate formed in step S4 of example 1 of the present invention;
fig. 5 is an XRD pattern of the lead carbonate precipitate generated in step S4 of example 1 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
In the description of the present invention, it should be understood that the relation indicating the orientation or position such as "above" is based on the orientation or position relation shown in the drawings, or the orientation or position relation which the product of the present invention is usually put into use, or the orientation or position relation which is usually understood by those skilled in the art, and is only for convenience of describing the present invention and simplifying the description, but does not indicate or imply that the device or element to be referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, cannot be construed as limiting the present invention.
Furthermore, the terms "first," "second," and the like are used merely to distinguish one description from another, and are not to be construed as indicating or implying relative importance.
In the following, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The embodiment of the application provides a method for recovering lead from lead-containing sludge by electrochemical leaching, which comprises the following steps:
s1, adding acid into the lead-containing sludge to adjust the pH value to 2-4, adding ferrous ions, and then adding hydrogen peroxide to enable the lead-containing sludge to generate a Fenton reaction;
s2, carrying out electrochemical leaching on the lead-containing sludge subjected to the Fenton reaction, so that lead ions in the lead-containing sludge enter the electrolyte on one side of the cathode;
s3, adjusting the pH value of the electrolyte to 5-6, filtering, and collecting filtrate;
and S4, adding carbonate into the filtrate to generate a lead carbonate precipitate, adding acid into the lead carbonate precipitate to dissolve the lead carbonate precipitate, and preparing lead by an electrolytic method.
Specifically, the carbonate is sodium carbonate, potassium carbonate, etc., and the ferrous ion can be ferrous sulfate, ferrous chloride, etc.
The method for recovering lead by electrochemical leaching of lead-containing sludge according to the present application includes oxidizing and degrading a part of organic matters in sludge by using strong oxidative hydroxyl radicals (· OH) generated by a Fenton reaction, destroying sludge flocs to desorb lead from the sludge floc structure, performing electrochemical leaching to migrate lead into an electrolyte under the action of an electric field, recovering lead by using a chemical precipitation method and an electrolysis method, and performing electrolysis after impurity removal to obtain electrolytic lead with a purity of 99.997%. The method can fully remove and recover heavy metal lead in the lead-containing industrial sludge, the recovery rate of the lead can reach more than 90 percent, the harm of the sludge to the environment is reduced, the recovery and the resource of the lead are fully realized finally, meanwhile, leacheate can be discharged harmlessly after chemical precipitation, and the reduction of the sludge can be realized through electroosmosis dehydration treatment.
In some embodiments, the electrochemical leaching of the lead-containing sludge after the Fenton reaction is performed, so that lead ions in the lead-containing sludge enter the electrolyte on the cathode side specifically:
providing an electrolytic tank 1 and a power supply 4, wherein an anode 2 and a cathode 3 are arranged in the electrolytic tank 1, and electrolyte is placed between the cathode 3 and the inner wall of the electrolytic tank 1;
the anode 2 and the cathode 3 are both porous structures;
the electrolyte is a citric acid solution with the pH value of 3.5-4.5;
during electrochemical leaching, lead-containing sludge is placed between the cathode 3 and the anode 2, the cathode of the power supply 4 is connected with the cathode 3, and the anode of the power supply 4 is connected with the anode 2.
In the above embodiment, referring to fig. 1, an anode 2 and a cathode 3 are oppositely disposed in an electrolytic cell 1, a first chamber 11 is formed between the cathode 3 and the inner wall of the electrolytic cell 1, and a citric acid solution with a pH of 3.5 to 4.5 is placed in the first chamber 11; during electrochemical leaching, the lead-containing sludge subjected to the Fenton reaction is placed between a cathode 3 and an anode 2 of an electrolytic cell 1, the cathode of a power supply 4 is connected with the cathode 3, the anode of the power supply 4 is connected with the anode 2, and due to the fact that the cathode is a porous cathode, pb ions in the sludge migrate to the vicinity of the cathode during electrochemical leaching and finally pass through the cathode 3 to enter a citric acid solution; the pH value of the further citric acid solution is controlled to be 3.5-4.5, so that OH generated by hydrogen evolution near the cathode in the electrochemical leaching process can be avoided - Lead to the precipitation of Pb, and apparently keep the vicinity of the cathode acidic at all times during the electrochemical leaching process, so as to neutralize the OH produced - 。
In practice, a second chamber 12 is formed between the anode 2 and the inner wall of the electrolytic cell 1, and a citric acid solution with a pH value of 3.5-4.5 is placed in the second chamber 12.
In some embodiments, the cathode is a porous titanium electrode plate, and the porosity of the cathode is 25-60%.
In some embodiments, the anode is a titanium-based iridium dioxide coated electrode, and the porosity of the anode is 10 to 50%.
In some embodiments, the electrochemical leaching process is performed under a constant or intermittent voltage condition with a voltage gradient of 1.0-2.0V/cm;
the time of the electrochemical leaching is 10.0-20.0h/cm according to the length of the lead-containing sludge between the anode and the cathode;
in the electrochemical leaching process, the anode moves 2-10cm in the cathode direction every 3.0-10.0 h until the distance between the anode and the cathode is 2-6 cm, and then does not move, and the electrochemical leaching is stopped after the electrochemical leaching is continued for 4-10 h.
Specifically, in the above-mentioned examples, the voltage gradient of 1.0 to 2.0V/cm means that the voltage gradient is controlled to be 1.0 to 2.0V/cm per cm length of the lead-containing sludge, specifically, for example, if the length of the lead-containing sludge (i.e., the length of the lead-containing sludge, i.e., the distance between the anode and the cathode) is 10cm, the voltage between the anode and the cathode is controlled to be 10 to 20V, and if the length of the lead-containing sludge is 20cm, the voltage between the anode and the cathode is controlled to be 20 to 40V; specifically, the electrochemical leaching is performed by using a constant or intermittent voltage, specifically, the intermittent voltage means that the electrochemical leaching is stopped after a period of time, then the power is continuously applied for the electrochemical leaching, for example, every time the electrochemical leaching is performed for 5min, then the power is stopped for 2min, then the electrochemical leaching is continuously performed for 5min, and the process is circulated; the time for electrochemical leaching is 10.0-20.0h/cm according to the length of the lead-containing sludge between the anode and the cathode, for example, when the length of the lead-containing sludge between the anode and the cathode is 1cm, the time for electrochemical leaching is 10-20 h, if the length of the lead-containing sludge is 10cm, the time for electrochemical leaching is 100-200 h, and if the length of the lead-containing sludge is 20cm, the time for electrochemical leaching is 200-400 h; meanwhile, in the electrochemical leaching process, the anode moves 2-10cm in the cathode direction every 3.0-10.0 h until the anode does not move any more after being spaced 2-6 cm away from the cathode, the electrochemical leaching is continued for 4-10 h, and then the electrochemical leaching is stopped.
In some embodiments, the length of the lead-containing sludge between the anode and the cathode is between 3 and 20cm.
In some embodiments, the acid is nitric acid, the amount of hydrogen peroxide added per kg of the lead-containing sludge is 40 to 100g, and the amount of ferrous ions added per kg of the lead-containing sludge is 0 to 100mg; specifically, the concentration of the nitric acid is 1 to 5mol/L.
Specifically, the amounts of the hydrogen peroxide and the divalent iron ions added are both relative to the dry weight of the lead-containing sludge, and specifically, the method for measuring the dry weight of the lead-containing sludge specifically comprises the following steps: drying the lead-containing sludge sample in an environment at 105 ℃ for more than 12h until the weight is not reduced any more; specifically, soluble ferrous salts such as ferrous chloride and ferrous nitrate can be used as the ferrous ions, but ferrous sulfate cannot be used because sulfate easily forms insoluble lead sulfate with lead. In an acidic environment with pH =3.0 or so, the divalent iron ions catalyze hydrogen peroxide to generate hydroxyl radicals with strong oxidizing property, thereby oxidizing part of organic matters in the sludge. The divalent iron ion is a catalyst. In general, a certain amount of ferrous ion flocculant is added in the sewage treatment process, so that the sludge per se contains a certain amount of ferrous ions, and therefore, in some cases, the ferrous ions do not need to be additionally added in the embodiment of the invention.
Preferably, the adding amount of the hydrogen peroxide in each kg of the lead-containing sludge is 60g, and the adding amount of the ferrous ions in each kg of the lead-containing sludge is 80mg; specifically, the concentration of nitric acid is 4mol/L, and acid is added into the lead-containing sludge to adjust the pH value to 3.
In some embodiments, the lead-containing sludge after electrochemical leaching is subjected to electroosmotic dewatering.
In some embodiments, in step S2, the water content of the electrochemically rinsed sludge is in a range of 60 to 90%, so that the water content of the leaded sludge after the Fenton reaction is performed is adjusted to 60 to 90% before the electrochemical rinsing, water is added to increase the water content of the leaded sludge if the water content of the leaded sludge is less than 60%, and the leaded sludge is dried to reduce the water content of the leaded sludge if the water content of the leaded sludge is higher than 90%.
In some embodiments, in step S3, the pH of the electrolyte is adjusted to 5 to 6 by using sodium hydroxide, the electrolyte is filtered to remove elemental impurities such as iron and aluminum, and the filtrate is collected.
In some embodiments, the lead-containing sludge after electrochemical leaching is subjected to electroosmotic dehydration by using the electric field intensity of 25-45V/cm, and the thickness of the lead-containing sludge in the electroosmotic dehydration is 1.0-2.5 cm. The lead-containing sludge refers to the distance between the cathode and the anode in the electroosmotic dehydration process, namely the length of the sludge between the cathode and the anode.
Specifically, fig. 2 shows a schematic flow chart of the method for recovering lead by electrochemical leaching of lead-containing sludge according to the present application.
The method for recovering lead from the lead-containing sludge by electrochemical leaching according to the present invention will be described below with reference to specific examples.
Example 1
The method for recovering lead by electrochemical leaching of lead-containing sludge provided by the embodiment of the application comprises the following steps:
s1, adding nitric acid into the lead-containing sludge to adjust the pH value to 3, and then adding ferrous ions (specifically adding ferrous chloride) and hydrogen peroxide to enable the lead-containing sludge to generate a Fenton reaction; wherein the adding amount of hydrogen peroxide in each kg of the lead-containing sludge is 50g, the adding amount of ferrous ions in each kg of the lead-containing sludge is 10mg, and the concentration of nitric acid is 4mol/L; wherein, the adding amount of the hydrogen peroxide and the ferrous ions is relative to the dry weight of the lead-containing sludge;
s2, adjusting the water content of the lead-containing sludge subjected to the Fenton reaction to 85%, and performing electrochemical leaching on the lead-containing sludge, wherein the specific process is as follows:
providing an electrolytic cell and a power supply, wherein an anode and a cathode are arranged in the electrolytic cell, and electrolyte is placed between the anode and the inner wall of the electrolytic cell and between the cathode and the inner wall of the electrolytic cell;
the anode is a titanium-based iridium dioxide coating electrode, and the porosity of the anode is 10 percent;
the cathode is a porous titanium electrode plate, and the porosity of the cathode is 25%;
the electrolyte is a citric acid solution with the pH value of 4.0;
during electrochemical leaching, lead-containing sludge is placed between the cathode and the anode, the cathode of the power supply is connected with the cathode, and the anode of the power supply is connected with the anode;
the electrochemical leaching process is carried out under a constant voltage of 1.0V/cm, the distance between the anode and the cathode before the electrochemical leaching is 10cm, the anode does not move any more after moving 2cm towards the cathode every 10.0h in the electrochemical leaching process until the anode is 2cm away from the cathode, the electrification is finished after the electrochemical leaching is continued for 10h, and the electrolyte close to one side of the cathode is taken out;
s3, adjusting the pH value of the electrolyte to 5 by adopting sodium hydroxide, filtering and collecting filtrate;
s4, adding sodium carbonate into the filtrate to generate a lead carbonate precipitate, adding acid into the lead carbonate precipitate to dissolve the lead carbonate precipitate, and preparing lead by an electrolytic method;
and S5, performing electroosmotic dehydration on the lead-containing sludge subjected to electrochemical leaching in the step S2 by adopting an electric field intensity of 45V/cm, wherein the thickness of the lead-containing sludge in the electroosmotic dehydration is 1.0cm.
Example 2
The method for recovering lead by electrochemical leaching of lead-containing sludge provided by the embodiment of the application comprises the following steps:
s1, adding nitric acid into the lead-containing sludge to adjust the pH value to 3, and then enabling the lead-containing sludge to generate a Fenton reaction by using hydrogen peroxide; wherein, the adding amount of hydrogen peroxide in each kg of the lead-containing sludge is 50g, and the concentration of nitric acid is 3mol/L; wherein the adding amount of the hydrogen peroxide is relative to the dry basis weight of the lead-containing sludge;
s2, adjusting the water content of the lead-containing sludge subjected to the Fenton reaction to 85%, and performing electrochemical leaching on the lead-containing sludge, wherein the specific process is as follows:
providing an electrolytic cell and a power supply, wherein an anode and a cathode are arranged in the electrolytic cell, and electrolyte is placed between the anode and the inner wall of the electrolytic cell and between the cathode and the inner wall of the electrolytic cell;
the anode is a titanium-based iridium dioxide coating electrode, and the porosity of the anode is 15%;
the cathode is a porous titanium electrode plate, and the porosity of the cathode is 35%;
the electrolyte is a citric acid solution with the pH value of 3.5;
during electrochemical leaching, lead-containing sludge is placed between the cathode and the anode, the cathode of the power supply is connected with the cathode, and the anode of the power supply is connected with the anode;
the electrochemical leaching process is discontinuously operated under the voltage of 2.0V/cm, electrochemical leaching is carried out for two minutes every time when the power is switched on, the power is cut off for two minutes again, electrochemical leaching is carried out for two minutes again, the power is cut off for two minutes again, the power is cycled on and off, the distance between the anode and the cathode before the electrochemical leaching is 20cm, the anode does not move any more after moving to the cathode direction for 4cm at an interval of 6h until the distance between the anode and the cathode is 4cm, the electrochemical leaching is continued for 6h, then the power is ended, and the electrolyte close to one side of the cathode is taken out;
s3, adjusting the pH value of the electrolyte to 5.5 by using sodium hydroxide, filtering, and collecting filtrate;
s4, adding carbonate into the filtrate to generate a lead carbonate precipitate, adding acid into the lead carbonate precipitate to dissolve the lead carbonate precipitate, and preparing lead by an electrolytic method;
and S5, performing electroosmotic dehydration on the lead-containing sludge subjected to electrochemical leaching in the step S2 by adopting an electric field intensity of 35V/cm, wherein the thickness of the lead-containing sludge in the electroosmotic dehydration is 1.0cm.
Comparative example 1
The method for recovering lead by electrochemical leaching of the lead-containing sludge provided by the comparative example is the same as that in example 1, except that step S1 is not included, the water content of the lead-containing sludge is directly adjusted to 85%, and then the electrochemical leaching process which is the same as that in example 1 and the processes from step S3 to step S5 in example 1 are carried out.
Comparative example 2
The method for recovering lead by electrochemical leaching of the lead-containing sludge provided by the comparative example is the same as that in the example 1, the difference is that only nitric acid is added into the lead-containing sludge in the step S1 to adjust the pH to 3, then the water content of the lead sludge is adjusted to 85%, and then the electrochemical leaching process which is completely the same as that in the example 1 and the processes from the step S3 to the step S5 in the example 1 are carried out.
Comparative example 3
The method for recovering lead from the lead-containing sludge by electrochemical leaching provided by the comparative example is the same as that in example 1, except that only hydrogen peroxide is added into the lead-containing sludge in step S1, then the water content of the lead-containing sludge is adjusted to 85%, and then the electrochemical leaching process which is the same as that in example 1 and the processes from step S3 to step S5 in example 1 are carried out. And the adding amount of the hydrogen peroxide is 50g per kg of the lead-containing sludge, wherein the adding amount of the hydrogen peroxide is relative to the dry weight of the lead-containing sludge.
FIG. 3 shows the results of testing the removal rate of lead and the remaining ratio of various forms of lead in the lead-containing sludge after electrochemical leaching according to the methods of example 1 and comparative examples 1 to 3.
EK1 to EK3 in FIG. 3 correspond to the methods in comparative examples 1 to 3, respectively, EK4 represents the method in example 1, initial represents the morphological distribution of lead in the original lead-containing sludge without any conditioning treatment or electrochemical rinsing treatment. In the figure, F1-F4 represent respectively the weak acid extractable state, reducible state, oxidizable state, residue state. Extractable state: the heavy metal part adhered to the sludge floc particles is sensitive to environmental change and easy to migrate and convert. Reducible state: heavy metals in the form of binding, adsorption or coprecipitation with carbonates, iron manganese oxides. Oxidizable state: the heavy metal is partially wrapped or chelated with various organic matters, humic acid or microorganisms. Residue state: heavy metals in the residual state are generally present in the silicate, primary and secondary mineral lattices. Is not easy to release under natural conditions and can be stabilized in sludge for a long time. In the figure, remove represents lead removal rate.
As can be seen from the removal rate of heavy metals in fig. 3, the removal rate of lead in the electro-leaching process is significantly improved by the sludge after fenton treatment (example 1, ek4) compared to the raw sludge without any treatment (EK 1), the sludge after nitric acid conditioning (EK 3) or hydrogen peroxide oxidation conditioning (EK 2). In particular, the lead content in the extractable and oxidizable states is greatly reduced.
Fig. 4 is an SEM image of the lead carbonate precipitate generated in step S4 of example 1.
Fig. 5 is an XRD pattern of the lead carbonate precipitate generated in step S4 of example 1.
As can be seen from fig. 4 to 5, lead carbonate having a high degree of crystallinity and a high purity can be recovered from the catholyte.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (4)
1. The electrochemical leaching lead recovery method of the lead-containing sludge is characterized by comprising the following steps:
adding acid into the lead-containing sludge to adjust the pH value to 2-4, adding ferrous ions, and then adding hydrogen peroxide to enable the lead-containing sludge to generate a Fenton reaction;
carrying out electrochemical leaching on the lead-containing sludge subjected to the Fenton reaction to enable lead ions in the lead-containing sludge to enter electrolyte on one side of a cathode;
adjusting the pH value of the electrolyte to 5-6, filtering, and collecting filtrate;
adding carbonate into the filtrate to generate a lead carbonate precipitate, adding acid into the lead carbonate precipitate to dissolve the lead carbonate precipitate, and preparing lead by an electrolytic method;
the method comprises the following steps of (1) carrying out electrochemical leaching on the lead-containing sludge subjected to the Fenton reaction, so that lead ions in the lead-containing sludge enter electrolyte on one side of a cathode:
providing an electrolytic cell and a power supply, wherein an anode and a cathode are arranged in the electrolytic cell, and electrolyte is placed between the cathode and the inner wall of the electrolytic cell;
the cathode is of a porous structure;
the electrolyte is a citric acid solution with pH of 3.5-4.5;
during electrochemical leaching, lead-containing sludge is placed between the cathode and the anode, the cathode of the power supply is connected with the cathode, and the anode of the power supply is connected with the anode;
the cathode is a porous titanium electrode plate, and the porosity of the cathode is 25-60%;
the anode is a titanium-based iridium dioxide coating electrode, and the porosity of the anode is 10-50%;
the electrochemical leaching process is carried out under the condition of constant or discontinuous voltage with the voltage gradient of 1.0-2.0V/cm;
the time of the electrochemical leaching is 10.0-20.0h/cm according to the length of the lead-containing sludge between the anode and the cathode;
in the electrochemical leaching process, the anode moves 2-10cm in the direction of the cathode every 3.0-10.0 h until the distance between the anode and the cathode is 2-6 cm, and then the anode does not move, and the electrochemical leaching is stopped after the electrochemical leaching is continued for 4-10 h;
the ferrous ions comprise ferrous chloride or ferrous nitrate, the acid is nitric acid, the addition amount of hydrogen peroxide in each kg of the lead-containing sludge is 40-100 g, and the addition amount of the ferrous ions in each kg of the lead-containing sludge is 10-100 mg.
2. The method for electrochemical leaching lead recovery from lead-containing sludge as claimed in claim 1, wherein the length of the lead-containing sludge between the anode and the cathode is 3-20 cm.
3. The method for electrochemical leaching lead recovery from lead-containing sludge according to claim 1, further comprising: and (3) performing electroosmosis dehydration on the lead-containing sludge subjected to electrochemical leaching.
4. The method for recovering lead from lead-containing sludge by electrochemical leaching according to claim 3, wherein the lead-containing sludge after electrochemical leaching is subjected to electroosmotic dehydration by using an electric field intensity of 25 to 45V/cm.
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