CN108079949B - Method for removing lead in water body by using magnetic pig manure biochar - Google Patents

Method for removing lead in water body by using magnetic pig manure biochar Download PDF

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CN108079949B
CN108079949B CN201711446967.2A CN201711446967A CN108079949B CN 108079949 B CN108079949 B CN 108079949B CN 201711446967 A CN201711446967 A CN 201711446967A CN 108079949 B CN108079949 B CN 108079949B
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pig manure
lead
water
biochar
magnetic
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CN108079949A (en
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王荣忠
黄丹莲
张辰
刘云国
赖萃
曾光明
薛文静
龚小敏
万佳
张青
罗浩
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Hunan University
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    • 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
    • B01J20/02—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
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28002—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their physical properties
    • B01J20/28009—Magnetic properties
    • 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
    • B01J20/34—Regenerating or reactivating
    • B01J20/345—Regenerating or reactivating using a particular desorbing compound or mixture
    • B01J20/3475—Regenerating or reactivating using a particular desorbing compound or mixture in the liquid phase
    • 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
    • C02F1/281—Treatment of water, waste water, or sewage by sorption using inorganic sorbents
    • 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
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/48—Sorbents characterised by the starting material used for their preparation
    • B01J2220/4875—Sorbents characterised by the starting material used for their preparation the starting material being a waste, residue or of undefined composition
    • B01J2220/4887—Residues, wastes, e.g. garbage, municipal or industrial sludges, compost, animal manure; fly-ashes
    • 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

Abstract

The invention discloses a method for removing lead in a water body by using magnetic pig manure biochar, which comprises the following steps: adding the magnetic pig manure biochar into a lead-containing water body, controlling the pH value of the water body to be 2-7, and carrying out constant-temperature oscillation treatment to adsorb and remove lead in the water body, wherein the preparation of the magnetic pig manure biochar comprises (1) pyrolyzing the pretreated pig manure at high temperature under nitrogen to obtain the pig manure biochar; (2) preparing a pig manure biochar dispersion liquid, mixing and stirring a trivalent ferric salt solution and a divalent ferric salt solution to prepare a ferric salt mixed solution; (3) and mixing and stirring the pig manure biochar dispersion liquid and the iron salt mixed solution, adjusting the pH value, and boiling, filtering, washing and drying to obtain the magnetic pig manure biochar. The method has the advantages of simple operation, low cost, quick and efficient adsorption of lead, easy separation and recovery, repeatable use, no harm to the environment and the like.

Description

Method for removing lead in water body by using magnetic pig manure biochar
Technical Field
The invention belongs to the technical field of sewage treatment, relates to a method for removing lead in a water body, and particularly relates to a method for removing lead in a water body by using magnetic pig manure biochar prepared by taking pig manure as a raw material.
Background
Lead is a heavy metal with great toxicity. Lead and its compounds pollute the environment more and more seriously due to lead-containing waste water, waste gas and waste residues discharged from the industrial production processes of mining, smelting, petroleum refining, storage batteries, glass, paint, coating, medicine, ships and the like. It can affect various organs such as nerve, hemopoiesis, digestion, urinary system, reproduction and development, cardiovascular system, endocrine system, immunity and skeleton, and the main target organs are nervous system and hemopoietic system. More seriously, it affects the growth and intelligence development of infants, damages the brain functions such as cognitive function, neuro-behavior, learning and memory, and the like, and causes dementia in severe cases. Therefore, the treatment of the lead-containing wastewater is very important, and the method is beneficial to environmental protection and public health.
At present, a great deal of research work is carried out on the treatment of heavy metal polluted wastewater by scholars at home and abroad. The wastewater treatment methods developed and applied mainly include adsorption, chemical, physical-chemical and biological methods. The adsorption method is to adsorb heavy metal ions by utilizing the characteristics of large specific surface area and high surface energy of materials, separate and remove the heavy metal ions from water and realize the purpose of purifying water. The adsorption method is one of the most important water treatment methods, is widely applied, and has the advantages of high efficiency, high speed, strong adaptability, simple process, convenient operation and the like. However, industrial adsorbents are expensive and have limited their application in water to some extent. Therefore, the research and development of the novel efficient adsorbent have important significance on the research of removing the heavy metals in the water body.
Biochar (biochar) is a refractory, stable, highly aromatic, carbon-rich solid substance produced by slow pyrolysis of biological residues at high temperatures (typically < 700 ℃) in the absence of oxygen. The biochar has the advantages of porous structure, high specific surface area, large pore volume, acid and alkali corrosion resistance, rich functional groups and the like, and is widely researched and applied in the fields of pollutant treatment, water body purification and the like. However, the original biochar has the following problems in the actual use process: first, the specific surface area, pore volume, and pore size of the original biochar are relatively small, and heavy metal removal efficiency is not high. Secondly, the reaction rate is slow, long reaction time is needed, the biochar can reach adsorption balance to heavy metals, and heavy metal pollution in water cannot be timely and effectively removed. Thirdly, after the original biochar finishes the adsorption of heavy metals in the water body, the solid-liquid separation can not be realized quickly, and the secondary pollution is reduced; therefore, there is a need to further research a modified biochar, which can not only remove heavy metals in water efficiently, but also reach adsorption balance quickly, and simultaneously can realize solid-liquid separation quickly and reduce secondary pollution.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides the method for removing the lead in the water body by using the magnetic pig manure biochar, which is simple to operate, low in cost, capable of quickly and efficiently adsorbing the lead, easy to separate and recover and harmless to the environment.
In order to solve the technical problems, the invention adopts the following technical scheme:
a method for removing lead in a water body by using magnetic pig manure biochar comprises the following steps: adding the magnetic pig manure biochar into a lead-containing water body, controlling the pH value of the water body to be 2-7, and carrying out constant-temperature oscillation treatment to remove lead in the water body by adsorption;
the preparation method of the magnetic pig manure biochar comprises the following steps:
(1) placing the pretreated pig manure in a nitrogen atmosphere, heating to 300-700 ℃ for high-temperature pyrolysis at a heating rate of 8-12 ℃/min for 2-4 h, cooling to room temperature, grinding, and sieving to obtain pig manure biochar;
(2) mixing the pig manure biochar obtained in the step (1) with water, stirring and dispersing at the stirring speed of 800-1000 r/min for 20-30 min to obtain pig manure biochar dispersion liquid; respectively preparing a ferric salt solution and a ferrous salt solution, then mixing and stirring the ferric salt solution and the ferrous salt solution at the stirring speed of 1083 r/min-1300 r/min for 20 min-30 min to obtain a ferric salt mixed solution;
(3) and (3) mixing and stirring the pig manure biochar dispersion liquid obtained in the step (2) with the ferric salt mixed solution, wherein the stirring speed is 867 r/min-1083 r/min, the stirring time is 20 min-30 min, the pH value of the obtained solution system is adjusted to 10-11, the solution system is boiled after continuous stirring, the boiling is kept for 60 min-90 min, and the magnetic pig manure biochar is obtained after filtering, washing and drying.
In the method for removing lead in the water body by using the magnetic pig manure biochar, the initial concentration of lead in the lead-containing water body is preferably 5 mg/L-500 mg/L, and the constant-temperature oscillation treatment time is preferably 0.25 min-15 min.
In the method for removing lead in the water body by using the magnetic pig manure biochar, preferably, the initial concentration of lead in the lead-containing water body is 5-100 mg/L, the pH value of the water body is controlled to be 3-7, and the constant-temperature oscillation treatment time is 3-5 min.
In the method for removing lead in the water body by using the magnetic pig manure biochar, preferably, the adding amount of the magnetic pig manure biochar is 0.5-5 g/L, and/or the rotation speed of the constant-temperature oscillation treatment is 160-200 rpm.
In the method for removing lead in water by using magnetic pig manure biochar, preferably, the coexisting cations in the lead-containing water comprise Na+、NH4+、Ca2+And Al3+One or more of them.
In the method for removing lead in the water body by using the magnetic pig manure biochar, preferably, after the lead in the water body is removed by adsorption, the obtained magnetic pig manure biochar after adsorption is subjected to solid-liquid separation from the water body, is subjected to desorption and regeneration, and is repeatedly used for adsorbing lead in the lead-containing water body.
In the method for removing lead in the water body by using the magnetic pig manure biochar, preferably, the analysis regeneration is performed by using a nitric acid solution, the concentration of the nitric acid solution is 1-2 mol/L, the analysis regeneration time is 12-24 h, the magnetic pig manure biochar obtained by the analysis regeneration is washed to be neutral by using ultrapure water, and the magnetic pig manure biochar is dried.
In the method for removing lead in water by using magnetic pig manure biochar, preferably, in the step (2) of the preparation method of magnetic pig manure biochar, the trivalent iron salt is FeCl3·6H2O, the ferrous salt is FeSO4·7H2O, the pig manure biochar and FeCl3·6H2O、FeSO4·7H2The mass ratio of O is 4.5-5.0: 4.8-5.0: 2.7-2.8. More preferably, the pig manure biochar and FeCl3·6H2O、FeSO4·7H2The mass ratio of O is 4.5-5: 4.8605-4.995: 2.7003-2.775.
In the method for removing lead in water by using magnetic pig manure biochar, preferably, in the step (3) of the preparation method of the magnetic pig manure biochar, sodium hydroxide solution is dropwise added into the solution system to adjust the pH value, the concentration of the sodium hydroxide solution is 8-10 mol/L, the continuous stirring time after the pH value is adjusted is 30-40 min, the washing is successively performed by adopting ultrapure water and ethanol, and the drying temperature is 60-70 ℃.
In the method for removing lead in water by using magnetic pig manure biochar, preferably, in the step (1) of the preparation method of magnetic pig manure biochar, the pretreatment process of pig manure is as follows: collecting fresh pig manure, drying, crushing, sieving with a 100-200 mesh sieve, and sealing for storage until the water content of the pig manure is 10-15%; the screening after crushing refers to screening by a 100-200 mesh sieve.
In the preparation method of the magnetic pig manure biochar, the stirring process of the pig manure biochar dispersion liquid in the step (2) is carried out at room temperature, and the stirring is carried out at room temperature when the ferric salt solution and the ferrous salt solution are mixed; and (4) stirring the pig manure biochar dispersion liquid at room temperature when adding the iron salt mixed solution.
In the invention, after the magnetic pig manure biochar repeatedly adsorbs lead-containing water with the initial concentration of 50mg/L for 5 times, the removal rate is over 80 percent.
The main innovation points of the invention are as follows:
the invention provides a method for removing lead in water (mainly referring to polluted water) by using a magnetic pig manure biochar material. The biochar prepared by taking the pig manure as the raw material has high ash content and strong alkalinity, and is beneficial to the precipitation of ferric salt mixed solution on the surface of the biochar to generate magnetic biochar; the magnetic biochar prepared by taking the pig manure as the raw material contains rich oxygen-containing functional groups, larger pore volume and pore size, the ash content is obviously higher than that of biochar prepared by herbaceous or woody plants, and the ash components are subjected to reactions such as precipitation, ion exchange and the like, so that the adsorption effect of the biochar on heavy metals in a water body is increased, the mobility and the biological effectiveness of the heavy metals in the water body are reduced, and the aim of effectively controlling the heavy metal pollution in the water body is fulfilled. Pig manure biochar and FeCl3·6H2O、FeSO4·7H2The magnetic biochar prepared by the O in a specific mass ratio can not only meet the requirement that the material can quickly realize solid-liquid separation under the action of an external magnetic field, but also ensure that the adsorption quantity of the magnetic biochar reaches the optimum. The excessive content of the biochar can cause the over-small proportion of the ferroferric oxide, and the solid-liquid separation is not enough. The content of the biochar is too low, so that the proportion of ferroferric oxide is too high, the proportion of the biochar is reduced, oxygen-containing functional groups are reduced, and the adsorption capacity of heavy metals is reduced. Compared with the common biochar, the magnetic pig manure biochar improves the specific surface area and the pore volume of the biochar, increases adsorption sites, enhances the adsorption capacity of the pig manure biochar to pollutants, greatly shortens the balance time of the biochar to heavy metal adsorption, reduces energy consumption, can quickly realize solid-liquid separation under the action of an external magnetic field, is a cheap, effective and practical adsorbent, is suitable for large-scale use,the method can also be used for emergency treatment of water bodies in sudden heavy metal pollution accidents, and has good application value.
Compared with the prior art, the invention has the advantages that:
1. in the method for removing lead in the water body by using the magnetic pig manure biochar, the adsorption effect of the magnetic pig manure biochar on lead is remarkable, and the removal rate can reach 99 percent and is far higher than that of other adsorbents.
2. In the method for removing lead in the water body by using the magnetic pig manure biochar, the adsorption of the magnetic pig manure biochar on lead can quickly reach adsorption balance, the adsorption balance can be reached within 5min, the reaction time is shortened, the energy consumption is reduced, and the method can be used for environmental management under emergency conditions.
3. In the method for removing lead in the water body by using the magnetic pig manure biochar, the magnetic biochar is easy to recover under the action of an external magnetic field, and secondary pollution is avoided.
4. The invention takes the pig manure as the raw material, has wide source, low cost, simple preparation method, easy operation and easy popularization.
5. The invention takes the pig manure as the raw material, not only solves the problem of treatment and disposal of the manure waste which is difficult to solve in the rural livestock and poultry breeding, reduces the damage to the ecological environment, applies the pig manure biochar to the research of removing heavy metals in the water body, but also realizes the resource utilization of the pig manure and achieves the purpose of protecting the environment.
Drawings
FIG. 1 is a scanning electron microscope image of 500 ℃ magnetic pig manure biochar in example 1 of the present invention.
FIG. 2 is a general X-ray electron spectrum of magnetic pig manure biochar at 500 ℃ in example 1 of the present invention.
FIG. 3 is the peak C1s of the X-ray electron spectrum of the magnetic pig manure biochar at 500 ℃ in example 1 of the present invention.
FIG. 4 is a hysteresis regression line diagram of 500 ℃ magnetic pig manure biochar in example 1 of the present invention.
FIG. 5 is a diagram showing the solid-liquid separation of magnetic pig manure biochar at 500 ℃ under the action of an external magnetic field in example 1 of the present invention.
FIG. 6 shows the lead removal rate and adsorption amount of the magnetic pig manure biochar at 300 ℃ in example 1 of the present invention.
FIG. 7 shows the lead removal rate and adsorption amount of the magnetic pig manure biochar at 500 ℃ in example 1 of the present invention.
FIG. 8 shows the lead removal rate and adsorption amount of the magnetic pig manure biochar at 700 ℃ in example 1 of the present invention.
Detailed Description
The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.
The materials and equipment used in the following examples are commercially available.
Example 1:
the invention discloses a method for removing lead in a water body by using magnetic pig manure biochar, which comprises the following steps:
s1: firstly, preparing the magnetic pig manure biochar by adopting the following method:
(1) preparing the pig manure biochar: collecting fresh pig manure, drying to 10-15% at 60 ℃, crushing, sieving with a 100-mesh sieve, and sealing and storing for later use. And (3) putting the crushed and sieved pig manure into a tubular furnace, introducing nitrogen, pyrolyzing at high temperature with the heating rate of 8 ℃/min, the pyrolysis temperature of 500 ℃ and the pyrolysis retention time of 2h, cooling to room temperature, grinding, and sieving with a 100-mesh sieve to obtain the pig manure Biochar (BC).
(2) Preparing a pig manure biochar dispersion liquid: weighing 5g of pig manure biochar, adding the pig manure biochar into a beaker, adding 50mL of ultrapure water, stirring and dispersing at the stirring speed of 800r/min for 30min to obtain the pig manure biochar dispersion liquid.
FeSO4·7H2Preparation of O solution: weighing 2.775g FeSO4·7H2Adding O into a beaker, adding 20mL of ultrapure water for dissolving, and obtaining FeSO4·7H2And (4) O solution.
FeCl3·6H2Preparation of O solution: weighing 4.995g FeCl3·6H2Adding O into a beaker, adding 130mL of ultrapure water for dissolving to obtain FeCl3·6H2And (4) O solution.
The FeSO is added4·7H2O solution and FeCl3·6H2And mixing the O solution at the stirring speed of 1300r/min, and violently stirring for 30min to obtain the iron salt mixed solution.
Preparing magnetic pig manure biochar: adding the pig manure biochar dispersion liquid into the ferric salt mixed solution, stirring at the speed of 867r/min for 30 min. A10M NaOH solution was added dropwise until the pH reached 10 to cause precipitation. Stirring for 30min, boiling, and keeping boiling for 90 min. Filtering, sequentially cleaning with ultrapure water and ethanol for several times, and oven drying at 60 deg.C to obtain magnetic pig manure biochar (Fe)3O4-BC 500). The magnetic pig manure biochar is black in appearance and mainly comprises pig manure biochar and ferroferric oxide modified on the surface of the pig manure biochar. Through detection, the ash content of the magnetic pig manure biochar is 58.77%, and the specific surface area is 259.22m2Per g, pore volume 0.396cm3The average pore diameter was 2.367 nm.
The prepared magnetic pig manure biochar is observed under a scanning electron microscope, the surface structure of the magnetic pig manure biochar is shown in figure 1, and the rough surface and the pore-containing structure of the magnetic pig manure biochar can be observed. The magnetic pig manure biochar mainly contains elements such as C, O, N, Si, P, Mg, Na, Ca, Fe and the like, and consists of various organic matters and ash, wherein the magnetic pig manure biochar contains Fe element, which indicates that ferroferric oxide is successfully loaded on the surface of the biochar. The result of the C1s peak separation of the magnetic pig manure biochar is shown in figure 3, which shows that functional groups such as C-C, C-H, C-O, O-C ═ O and pi-pi ×, and the like exist in the biochar. The magnetic hysteresis regression line of the magnetic pig manure biochar and the result of solid-liquid separation under the action of an external magnetic field are shown in figure 4, and the saturation magnetic strength is 6.0918emu g-1The magnetic hysteresis loop basically tends to S type, and basically has no coercive force and remanence, so that the expected purpose of people can be achieved, and solid-liquid separation is realized. FIG. 5 shows Fe under the action of external magnetic field3O4the-BC 500 can be uniformly dispersed in the aqueous solution. Under the action of external magnetic field, the magnetic biochar is adsorbed to the bottle wall within 5min to quickly realize solid-liquid separation, and as a result, the magnetic biochar is adsorbed to the bottle wallThe prepared magnetic biochar has better magnetic response capability and is a potential adsorbent.
In order to research the removal efficiency of the magnetic pig manure biochar on the lead-containing water body under different conditions, the preparation method is also adopted, the pyrolysis temperatures in the step (1) are changed to 300 ℃ and 700 ℃, and the magnetic pig manure biochar Fe is prepared3O4-BC300 and magnetic pig manure biochar Fe3O4-BC700。
S2: and respectively adding the prepared magnetic pig manure biochar into a lead-containing water body, adjusting the pH value of the water body, and carrying out constant-temperature oscillation treatment at room temperature to adsorb and remove lead in the water body.
This example investigates the effect of reaction time on magnetic pig manure biochar on lead treatment efficiency.
0.01g of magnetic pig manure biochar is put into 10mL of 50mg/L lead-containing aqueous solution, and the pH value of the solution is adjusted to 5 by using 1M HCl and NaOH solutions. Shaking at constant temperature of 180rpm at 25 deg.C (both at room temperature), and sampling to detect the residual lead concentration in the solution 15s (0.25min) after shaking. And (3) performing solid-liquid separation on the sampling solution under the action of an external magnetic field, and filtering the supernatant by using a filter with the pore diameter of 0.48 mu m to obtain a filtrate. The untreated lead in the filtrate was measured by a flame atomic absorption photometer, and the magnetic biochar was analyzed for treatment efficiency under different treatment time conditions, and the results are shown in table 1 and fig. 6, 7 and 8.
TABLE 1 influence of reaction time on magnetic pig manure biochar on lead treatment efficiency
As can be seen from Table 1: 1min before the treatment of the magnetic pig manure biochar at three different pyrolysis temperatures, the adsorption rate is high; after treatment for 4-5 min, adsorption balance is basically achieved. Therefore, the method for treating the lead by using the magnetic pig manure biochar has short lead treatment time, the preferred adsorption time is 3-5 min, and the optimal adsorption time is 5, 5 and 4min respectively. As can be seen from FIGS. 6, 7 and 8, the magnetic pig manure organisms increased with the treatment timeThe adsorption capacity of carbon to lead is continuously increased, and Fe3O4-BC300、Fe3O4-BC500、Fe3O4The lead adsorption capacity of the-BC 700 reaches 49.50mg/g, 49.94mg/g and 49.78mg/g respectively.
Example 2
The method for removing lead in water by using the magnetic pig manure biochar disclosed by the invention adopts the magnetic pig manure biochar prepared in the example 1, and the influence of pH on the lead treatment efficiency of the magnetic pig manure biochar is examined in the example.
0.01g of magnetic pig manure biochar is put into 10mL of 50mg/L lead-containing solution, and the pH values of the solution are adjusted to be 2, 3, 4, 5, 6 and 7 respectively by using 1M HCl and NaOH solutions. Oscillating at 25 deg.C and 180rpm for 24 hr (5min or more than 4min to reach adsorption balance). The treated solution is subjected to solid-liquid separation under the action of an external magnetic field, and the supernatant is filtered by a filter with the pore diameter of 0.48 mu m to obtain filtrate. Untreated lead in the filtrate was measured by a flame atomic absorption photometer, and the treatment efficiency of the magnetic pig manure biochar under the pH condition was analyzed based on the untreated lead, and the measurement results are shown in Table 2.
TABLE 2 influence of pH on the magnetic pig manure biochar on lead treatment efficiency
As can be seen from Table 2: when the pH value is 2, the lead removal efficiency of the magnetic pig manure biochar at three different pyrolysis temperatures is low. When the pH value is changed from 3 to 7, the removal efficiency of the magnetic pig manure biochar on lead is more than 96%, and the influence of the pH value on the adsorption effect is small, which shows that the magnetic pig manure biochar on Pb-containing materials with the pH value of 3 to 72+The solution removal effect is good.
Example 3
The method for removing lead in water by using the magnetic pig manure biochar disclosed by the invention adopts the magnetic pig manure biochar prepared in the example 1, and the influence of the initial concentration of lead on the lead treatment efficiency by the magnetic pig manure biochar is examined in the example.
0.01g of magnetic pig manure biochar is respectively added into 10mL of lead-containing aqueous solution with the concentration of 5, 10, 20, 30, 50, 100, 200, 300 and 500mg/L, and the pH value of the solution is adjusted to 5 by 1M HCl and NaOH solutions. Oscillating at constant temperature of 25 deg.C and 180rpm for 24h (5min or more than 4min, to reach adsorption balance). And performing solid-liquid separation on the treated solution under the action of an external magnetic field, and filtering the supernatant by using a filter with the pore diameter of 0.48 mu m to obtain a filtrate. Untreated lead in the filtrate was measured by a flame atomic absorption photometer, and the magnetic pig manure biochar was analyzed for treatment efficiency at different initial concentrations, and the results are shown in table 3.
TABLE 3 influence of initial concentration on magnetic pig manure biochar on lead treatment efficiency
As can be seen from Table 3: when the lead concentration is 5-100 mg/L, Fe3O4The lead removal rate of the-BC reaches more than 95 percent. But when the lead concentration is increased, the removal rate of the magnetic pig manure biochar to lead is reduced to 60 percent at least. The magnetic pig manure biochar is proved to have the effect on Pb containing pH of 5-100 mg/L2+The solution removal effect is optimal.
Example 4
The method for removing lead in water by using the magnetic pig manure biochar disclosed by the invention adopts the magnetic pig manure biochar prepared in the example 1, and the influence of cations coexisting in a solution on the lead treatment efficiency of the magnetic pig manure biochar is examined in the example.
Adding 0.01g of magnetic pig manure biochar into 10mL of lead-containing solution of 50mg/L, adjusting the pH value of the solution to 5 by using 1M of HCl and NaOH solutions, and respectively adding 1M of NaCl and NH4Cl、CaCl2、AlCl3. Oscillating at constant temperature of 25 deg.C and 180rpm for 24h (5min or more than 4min, to reach adsorption balance). And performing solid-liquid separation on the treated solution under the action of an external magnetic field, and filtering the supernatant by using a filter with the pore diameter of 0.48 mu m to obtain a filtrate. The untreated lead in the filtrate is measured by a flame atomic absorption photometer, and the treatment efficiency of the magnetic pig manure biochar under different coexisting cation conditions is analyzed according to the untreated leadThe results are shown in Table 4.
TABLE 4 Effect of coexisting cations in the solution on the magnetic pig manure biochar on lead treatment efficiency
As can be seen from Table 4: the coexisting cations have certain influence on the removal rate of the lead by the magnetic pig manure biochar, wherein the influence degree is as follows: al (Al)3+＞Ca2+＞NH4 +＞Na+The higher the charge of the coexisting cation at the same concentration, the greater the influence on the amount of adsorption. Shows that the magnetic pig manure biochar pair contains Na+And NH4 +Pb of2+The solution has good removal effect on Ca2+Pb of2+The solution has better removing effect and contains Al3+Pb of2+The solution removal effect is poor.
Example 5
The method for removing lead in water by using the magnetic pig manure biochar disclosed by the invention adopts the magnetic pig manure biochar prepared in example 1, and the repeated adsorption effect of the magnetic pig manure biochar on lead adsorption is examined in the example.
Collecting the magnetic pig manure biochar after adsorbing the lead under the action of an external magnetic field, and adding HNO with the concentration of 1-2 mol/L3Oscillating the solution at the constant temperature of 25 ℃ and 180rpm for 24h, washing the resolved and regenerated magnetic pig manure biochar with ultrapure water until the magnetic pig manure biochar is neutral, and drying. 0.01g of magnetic pig manure biochar (Fe) is taken3O4-BC) in 10mL of a 50mg/L lead-containing solution, the pH of the solution being adjusted to 5 with 1M HCl and NaOH solutions. Shaking at 25 deg.C and 180rpm for 5 min. And (3) carrying out solid-liquid separation on the treated solution under the action of an external magnetic field, acidifying the adsorbed material again, carrying out desorption regeneration, drying and adsorbing again.
Untreated lead in the water body was measured by a flame atomic absorption photometer, and the repeated adsorption effect of the magnetic pig manure biochar on lead was analyzed based on the results, and the results are shown in table 5.
As can be seen from Table 5: magnetic pig manure biochar for 50mg/L Pb2+After the solution is repeatedly adsorbed for 5 times, the removal rate can reach more than 80 percent.
TABLE 5 repeated adsorption effect of magnetic pig manure biochar on lead adsorption
Comparative example 1
This comparative example investigates the efficiency of the reaction time on the treatment of lead with the magnetically unmodified biochar.
The preparation method of the unmodified pig manure Biochar (BC) comprises the following steps:
collecting fresh pig manure, drying at 60 ℃, crushing, sieving with a 100-mesh sieve, sealing and storing for later use. And (3) putting the crushed and sieved pig manure into a tubular furnace, introducing nitrogen, pyrolyzing at high temperature with the heating rate of 8 ℃/min, the pyrolysis temperature of 300 ℃ and the pyrolysis retention time of 2h, cooling to room temperature, grinding, and sieving with a 100-mesh sieve to obtain the pig manure biochar (BC 300).
By adopting the same method, the pyrolysis temperature is changed to be 500 ℃ and 700 ℃, and the pig manure biological carbon BC500 and the pig manure biological carbon BC700 are prepared.
0.01g of BC was placed in 10mL of a 50mg/L lead-containing solution, and the pH of the solution was adjusted to 5 with 1M HCl and NaOH solutions. Oscillating at constant temperature of 25 deg.C and 180rpm, and sampling to detect the residual lead concentration in the solution 0.5min after oscillation. The treated solution was centrifuged, separated by filtration, and the supernatant was filtered through a 0.48 μm pore filter to obtain a filtrate.
Untreated lead in the water body was measured by a flame atomic absorption photometer, and the treatment efficiency of the biochar which was not magnetically modified under different treatment time conditions was analyzed based on the results, and the results are shown in table 6.
TABLE 6 reaction time versus efficiency of lead treatment with non-magnetically modified biochar
As can be seen from Table 6: the biochar which is not subjected to magnetic modification at different pyrolysis temperatures respectively removes lead for 90min, 25min and 10min, and the adsorption rate is high; adsorption equilibrium is basically reached after 360, 40 and 25min of treatment. As can be seen from comparison of the table 1, the adsorption of the magnetic pig manure biochar at different cracking temperatures to lead can reach the adsorption balance in 5, 5 and 4min, so that the adsorption balance time is obviously and greatly reduced.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make many possible variations and modifications to the disclosed embodiments, or equivalent modifications, without departing from the spirit and scope of the invention, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention.

Claims (7)

1. A method for removing lead in a water body by using magnetic pig manure biochar comprises the following steps: adding the magnetic pig manure biochar into a lead-containing water body, controlling the pH value of the water body to be 3-7, and carrying out constant-temperature oscillation treatment to adsorb and remove lead in the water body; the initial concentration of lead in the lead-containing water body is 5-100 mg/L, and the time of constant-temperature oscillation treatment is 3-15 min;
the preparation method of the magnetic pig manure biochar comprises the following steps:
(1) placing the pretreated pig manure in a nitrogen atmosphere, heating to 300-700 ℃ for high-temperature pyrolysis at a heating rate of 8-12 ℃/min for 2-4 h, cooling to room temperature, grinding, and sieving with a 100-200 mesh sieve to obtain pig manure biochar; the pretreatment process of the pig manure is as follows: collecting fresh pig manure, drying, crushing, sieving with a 100-200 mesh sieve, and sealing for storage until the water content of the pig manure is 10-15%;
(2) mixing the pig manure biochar obtained in the step (1) with water, stirring and dispersing at the stirring speed of 800-1000 r/min for 20-30 min to obtain pig manure biochar dispersion liquid; respectively preparing a ferric salt solution and a ferrous salt solution, then mixing and stirring the ferric salt solution and the ferrous salt solution at the stirring speed of 1083 r/min-1300 r/min for 20 min-30 min to obtain a ferric salt mixed solution; the trivalent ferric salt is FeCl3·6H2O, the ferrous salt is FeSO4·7H2O, the pig manure biochar and FeCl3·6H2O、FeSO4·7H2The mass ratio of O is 4.5-5.0: 4.8-5.0: 2.7-2.8;
(3) and (3) mixing and stirring the pig manure biochar dispersion liquid obtained in the step (2) with the ferric salt mixed solution, wherein the stirring speed is 867 r/min-1083 r/min, the stirring time is 20 min-30 min, the pH value of the obtained solution system is adjusted to 10-11, the solution system is boiled after being continuously stirred for 30 min-40 min, the boiling is kept for 60 min-90 min, and the magnetic pig manure biochar is obtained after filtering, washing and drying.
2. The method for removing lead in water by using magnetic pig manure biochar as claimed in claim 1, wherein the constant temperature oscillation treatment time is 3-5 min.
3. The method for removing lead in water body by using magnetic pig manure biochar as claimed in claim 1, wherein the adding amount of the magnetic pig manure biochar is 0.5-5 g/L, and/or the rotation speed of the constant temperature oscillation treatment is 160-200 rpm.
4. The method for removing lead in water by using magnetic pig manure biochar as claimed in claim 1, wherein the coexisting cations in the lead-containing water comprise Na+、NH4+、Ca2+And Al3+One or more of them.
5. The method for removing lead in water by using the magnetic pig manure biochar as claimed in any one of claims 1 to 4, wherein after the lead in the water is removed by adsorption, the obtained magnetic pig manure biochar after adsorption is subjected to solid-liquid separation from the water, is subjected to desorption regeneration, and is then repeatedly used for adsorbing lead in the lead-containing water.
6. The method for removing lead in water by using magnetic pig manure biochar as claimed in claim 5, wherein the analysis regeneration is carried out by using a nitric acid solution, the concentration of the nitric acid solution is 1-2 mol/L, the analysis regeneration time is 12-24 h, and the magnetic pig manure biochar obtained by the analysis regeneration is washed to be neutral by using ultrapure water and is dried.
7. The method for removing lead in water by using the magnetic pig manure biochar as claimed in any one of claims 1 to 4, wherein in the step (3) of the preparation method of the magnetic pig manure biochar, a sodium hydroxide solution is dropwise added into the solution system to adjust the pH value, the concentration of the sodium hydroxide solution is 8-10 mol/L, the washing is successively carried out by using ultrapure water and ethanol, and the drying temperature is 60-70 ℃.
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