CN113603179A - Preparation of composite biochar and method for removing thallium-containing ammonia nitrogen wastewater by composite biochar - Google Patents

Preparation of composite biochar and method for removing thallium-containing ammonia nitrogen wastewater by composite biochar Download PDF

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CN113603179A
CN113603179A CN202110949018.6A CN202110949018A CN113603179A CN 113603179 A CN113603179 A CN 113603179A CN 202110949018 A CN202110949018 A CN 202110949018A CN 113603179 A CN113603179 A CN 113603179A
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thallium
ammonia nitrogen
biochar
composite
adsorption
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龙建友
陈思浩
柯艳阳
彭丽瑚
李伙生
叶容川
郑一杰
陈子楷
黄涓溪
肖唐付
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Guangzhou University
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Guangzhou University
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/288—Treatment of water, waste water, or sewage by sorption using composite sorbents, e.g. coated, impregnated, multi-layered
    • 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
    • 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
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/3078—Thermal treatment, e.g. calcining or pyrolizing
    • 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
    • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
    • 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
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/76—Treatment of water, waste water, or sewage by oxidation with halogens or compounds of halogens
    • 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
    • B01J2220/4812—Sorbents characterised by the starting material used for their preparation the starting material being of organic character
    • B01J2220/4825—Polysaccharides or cellulose materials, e.g. starch, chitin, sawdust, wood, straw, cotton
    • 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
    • C02F2101/16—Nitrogen compounds, e.g. ammonia
    • 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 relates to a preparation method of composite biochar and a method for removing thallium-containing ammonia nitrogen wastewater by the same, which mainly comprises the steps of adding the composite biochar and hypochlorite into the thallium-containing ammonia nitrogen wastewater; the shaddock peel biochar prepared by taking shaddock peel as a material through a carbon thermal method is loaded with zero-valent manganese, and the load ratio of the shaddock peel biochar to the zero-valent manganese is 1: 0.3; the composite charcoal adsorbs monovalent thallium and trivalent thallium, and the monovalent thallium is oxidized into the trivalent thallium in the adsorption process; the hypochlorite dosage is within the range of not more than 30mmol/L, and the synchronous removal rate of thallium and ammonia nitrogen is increased along with the increase of the hypochlorite dosage. Specifically discloses a method for removing thallium-containing ammonia nitrogen wastewater, and describes the physical characteristics of the composite biochar in the removal of thallium ions and ammonia nitrogen in the thallium-containing ammonia nitrogen wastewater in detail. In the specific application process, the composite biochar can effectively adsorb and remove thallium ions and ammonia nitrogen in wastewater under different initial conditions, and the raw materials for preparing the composite biochar are simple and easy to obtain.

Description

Preparation of composite biochar and method for removing thallium-containing ammonia nitrogen wastewater by composite biochar
Technical Field
The invention belongs to the technical field of sewage treatment, relates to preparation of composite biochar, and particularly relates to preparation of load-type composite biochar and application of the load-type composite biochar in thallium-containing ammonia nitrogen wastewater treatment.
Background
Thallium is widely used in the fields of optics, military industry, electronic materials and superconducting materials, and has great potential application value in the fields of radiation shielding and the like. The thallium (Tl) resource is rich in China, along with the development and progress of science and technology, the thallium (Tl) resource is exploited and used in large quantity, but due to partial unreasonable development, a part of thallium (Tl) is discharged into the natural environment, so that the environment is polluted, and meanwhile, the thallium (Tl) resource has great potential hazard to human health. With the progress of industrial production technology, the components in industrial wastewater have also become diversified. Among these, highly aerobic pollutants and toxic pollutants reflect the characteristics of industrial wastewater in three aspects: high concentration, high ammonia nitrogen and difficult degradation. A part of industrial wastewater discharge contains a large amount of ammonia nitrogen, the ammonia nitrogen concentration can cause serious harm to the environment under certain conditions, and the excessive ammonia nitrogen causes difficulty in breathing and resistance reduction of aquatic organisms, even syncope conditions occur and normal growth of the organisms is influenced. Therefore, thallium (Tl) and ammonia nitrogen in the environment need to be removed and treated in time.
The biochar is a product produced by thermal cracking of biomass under an anoxic condition, has the characteristics of looseness, porosity and large specific surface area, and functional groups on the surface of the biochar comprise carboxyl, phenolic hydroxyl, anhydride and other groups, so that the biochar has good adsorption characteristics, can strongly adsorb organic pollutants in an environment medium, and reduces the environmental risk. The composite biochar is a novel material developed on the basis of biochar, and overcomes the defect that although the biochar has an excellent adsorption effect, the biochar is not easy to separate from a solution.
Patent CN109908867A discloses a method for removing ammonia nitrogen in a water body by using sulfonated biochar in an enhanced manner, and relates to the field of water treatment. The preparation method of the sulfonated biochar comprises the following steps: drying, grinding and sieving reed straws, and carrying out anaerobic pyrolysis in a nitrogen atmosphere to obtain reed biochar; and (3) sulfonating under the condition of heating by concentrated sulfuric acid, washing the sulfonated biochar to be neutral by using deionized boiling water, and then putting the washed biochar into an oven to be dried to obtain the sulfonated biochar. Patent CN108435135A discloses a preparation method of watermelon peel biochar, which comprises the following steps: (1) pretreating watermelon peels: drying the watermelon peel to obtain watermelon peel powder; (2) carbonizing: carbonizing the watermelon peel powder obtained in the step (1) for 0.5-1.5 hours at a carbonization temperature of 400-600 ℃ in a nitrogen atmosphere to obtain the watermelon peel biochar; the watermelon peel biochar prepared by the preparation method disclosed by the invention has the highest adsorption efficiency on thallium ion, and is simple in process and low in preparation cost. Although both of the above patents propose methods for purifying wastewater by using biochar, thallium and ammonia nitrogen in wastewater cannot be removed simultaneously.
At present, the main methods for removing thallium are chemical precipitation method, ion exchange method, adsorption method and the like. The most used method is an adsorption method, which mainly comprises activated carbon adsorption, biochar adsorption, composite material adsorption, nano metal compound adsorption and the like. Although the adsorption method can effectively remove thallium in industrial wastewater, the adsorption method has no effect on a large amount of ammonia nitrogen in the wastewater. Therefore, the invention provides a preparation method of composite biochar and a method for removing thallium-containing ammonia nitrogen wastewater by the composite biochar so as to synchronously and effectively eliminate thallium and ammonia nitrogen in the thallium-containing ammonia nitrogen wastewater.
Disclosure of Invention
The invention aims to treat thallium-containing ammonia nitrogen wastewater to remove thallium ions and ammonia nitrogen in the thallium-containing ammonia nitrogen wastewater.
In view of the above, the present application addresses this need in the art by providing a composite biochar prepared from commercially available biomass sources (such as grapefruit peel) with physical characteristics. Also provided herein are methods of making composite biochar suitable for adsorbing thallium ions in wastewater.
On the one hand, the method for removing the thallium-containing ammonia nitrogen wastewater comprises the following steps:
adding composite biochar and hypochlorite into thallium-containing ammonia nitrogen wastewater; the shaddock peel biochar prepared by taking shaddock peel as a material through a carbon thermal method is loaded with zero-valent manganese, and the load ratio of the shaddock peel biochar to the zero-valent manganese is 1: 0.3; the composite charcoal adsorbs monovalent thallium and trivalent thallium, and the monovalent thallium is oxidized into the trivalent thallium in the adsorption process; the hypochlorite dosage is within the range of not more than 30mmol/L, and the thallium and ammonia nitrogen synchronous removal rate is increased along with the increase of the hypochlorite dosage.
In another aspect, a method for loading zero-valent manganese on the shaddock peel biochar is provided:
adding the shaddock peel biochar into an aqueous solution containing divalent manganese, slowly adding an aqueous solution containing tetrahydroborate, washing with water, centrifuging, and freeze-drying; the aqueous solution containing the divalent manganese is an aqueous solution of manganese sulfate; the aqueous solution containing tetrahydroborate is an aqueous solution of sodium borohydride or potassium borohydride; the contact with air is minimized during the addition of the aqueous solution containing tetrahydroborate.
On the other hand, the shaddock peel biochar is prepared by a carbothermic method, specifically, shaddock peel is dried, crushed, sieved by a 100-mesh sieve and placed in a tubular furnace, the temperature is set to be 500 ℃, and the shaddock peel biochar is fired for 1 hour.
In some embodiments, the composite biochar provided by the invention is used for adsorbing thallium in wastewater, and the conditions for adsorbing thallium are as follows: the adding amount of the composite biochar is 2.0g/L, the adding amount of hypochlorite is 30mmol/L, the initial pH of thallium-containing ammonia nitrogen wastewater is 10, the reaction temperature is 15 ℃, and the adsorption time is 30 min.
In some embodiments, the composite biochar provided by the invention is used for adsorbing ammonia nitrogen in wastewater, and the conditions for removing ammonia nitrogen are as follows: the adding amount of the composite biochar is 0.25g/L, the adding amount of hypochlorite is 30mmol/L, the initial pH of thallium-containing ammonia nitrogen wastewater is 4, the reaction temperature is 15 ℃, and the adsorption time is 30 min. Under the initial condition, the highest removal efficiency of ammonia nitrogen in the wastewater can reach 70 percent.
A method for removing thallium ions and ammonia nitrogen from thallium ammonia nitrogen-containing wastewater is provided, made according to any of the methods described herein. Also provides the compound biochar loaded with zero-valent manganese on the shaddock peel biochar.
Compared with the prior art, the invention has the following beneficial effects or advantages:
(1) the main raw materials in the invention are shaddock peel and hypochlorite, so that the cost of the raw materials is low and the raw materials are easy to collect;
(2) under different initial conditions, the method not only realizes the efficient adsorption removal of thallium ions in the wastewater, but also realizes the removal of ammonia nitrogen in the wastewater;
(3) the method for removing thallium and ammonia nitrogen in the thallium-containing ammonia nitrogen wastewater is simple, the adsorption time is 30min, and the removal time is short.
Drawings
FIG. 1 is a diagram showing the thallium and ammonia nitrogen removal effects of a pure thallium solution group and a pure ammonia nitrogen solution group, wherein (a) is the pure thallium solution group, and (b) is the pure ammonia nitrogen solution group;
FIG. 2 is a diagram showing the effect of thallium and ammonia nitrogen removal in a thallium-ammonia nitrogen-containing solution set without sodium hypochlorite, wherein (c) is a pure thallium solution and (d) is a pure ammonia nitrogen solution;
FIG. 3 is a diagram showing the effect of thallium and ammonia nitrogen removal in a thallium-containing ammonia nitrogen solution group to which sodium hypochlorite is added, wherein (e) is a pure thallium solution, and (f) is a pure ammonia nitrogen solution;
FIG. 4 is a graph showing the effect of hypochlorite dosage on thallium and ammonia nitrogen removal by composite biochar, wherein (a) is Tl+A change in removal rate, (b) a change in ammonia nitrogen removal rate;
FIG. 5 is a graph showing the effect of different initial pH values on the removal of thallium and ammonia nitrogen by the composite charcoal, wherein (a) is Tl+A change in removal rate, (b) a change in ammonia nitrogen removal rate;
FIG. 6 is a diagram showing the change of pH value to Tl after the composite biochar is mixed with the thallium-containing ammonia nitrogen solution+Influence of the content, wherein (c) is Tl+A change in removal rate, (d) a change in ammonia nitrogen removal rate;
FIG. 7 is a graph showing the effect of different initial temperatures on the removal of thallium and ammonia nitrogen by the composite charcoal, wherein (e) is Tl+A change in removal rate, (f) a change in ammonia nitrogen removal rate;
FIG. 8 is an SEM image of the composite biochar before and after adsorption of thallium ions;
FIG. 9 is an X-ray diffraction spectrum before and after thallium ion adsorption by the composite biochar;
FIG. 10 is a Fourier transform infrared spectroscopy analysis before and after thallium ion adsorption by composite biochar;
FIG. 11 is an XPS spectrum of Tl4f after thallium ions are adsorbed by the composite biochar material;
FIG. 12 is an XPS spectrum of O1s before and after thallium ion adsorption by the composite biochar material, wherein (a) is before adsorption and (b) is after adsorption;
FIG. 13 is a graph showing the adsorption kinetics of thallium in the composite biochar adsorbing solution;
FIG. 14 is an isothermal adsorption curve of thallium in composite biochar adsorption solution.
Detailed Description
The following examples are given to illustrate the technical aspects of the present invention, but the present invention is not limited to the following examples.
Example 1
This example provides adsorption tests of composite biochar to thallium and ammonia nitrogen in solution.
The charcoal is prepared from pericarpium Citri Grandis by peeling fructus Citri Grandis, removing flesh, cutting pericarp, oven drying at 105 deg.C for 24 hr, removing water, pulverizing into powder with CS700y model multifunctional crusher, sieving with 100 mesh sieve, and storing the powder. And placing the powder in a ark, firing for one hour at the high temperature of 500 ℃ by using a tube furnace, and cooling to obtain the shaddock peel biochar. Dissolving manganese sulfate and shaddock peel biochar in deionized water according to the proportion of biochar to manganese sulfate being 1:0.3, and continuously stirring; taking excess NaBH4Dissolving in another beaker, dropwise adding into the previous beaker by using a peristaltic pump, covering the beaker by using a sealing film in the titration process, reducing the contact with air as much as possible, standing for 30min after the titration is finished, pouring out the supernatant, repeating for 2-3 times, pouring the rest solution into 3 centrifuge tubes, performing centrifugal treatment, and freeze-drying for 2 days by using a freeze-dryer to finally obtain the composite biochar.
(1) Influence of adding amount of composite biochar on thallium and ammonia nitrogen removal
The test is divided into a pure thallium solution group, a pure ammonia nitrogen solution group, a thallium ammonia nitrogen solution group without adding sodium hypochlorite, and a thallium ammonia nitrogen solution group with adding sodium hypochlorite. The test methods of the pure thallium solution group, the pure ammonia nitrogen solution group and the thallium ammonia nitrogen solution group without adding sodium hypochlorite are the same as the thallium ammonia nitrogen solution group with adding sodium hypochlorite. Solution Tl for pure thallium solution set+The concentration is 10mmol/L, wherein the test method does not add sodium hypochlorite; the ammonia nitrogen concentration of the solution used by the pure ammonia nitrogen solution group is 25mg/L, wherein the test method does not add sodium hypochlorite; the solution used without adding sodium hypochlorite is 400ml Tl in volume+Pure thallium solution with the concentration of 10mmol/L and pure ammonia nitrogen solution with the concentration of 25mg/L, wherein the test method does not add sodium hypochlorite. Taking a thallium-containing ammonia nitrogen solution group added with sodium hypochlorite as an example, respectively taking a volume of 400ml Tl+Placing a pure thallium solution with the concentration of 10mmol/L and a pure ammonia nitrogen solution with the concentration of 25mg/L in a 600ml beaker; respectively adjusting the pH values of the pure thallium solution and the pure ammonia nitrogen solution to 7 by using a NaOH solution and dilute nitric acid; respectively weighing 0.1 g, 0.2 g, 0.4 g, 0.6 g and 0.8g of composite biochar material, adding the materials into the solutions, and simultaneously adding 12mmol of sodium hypochloriteAnd carrying out shake table reaction for 30min at a constant speed of 150rmp and maintaining the temperature of 30 ℃, respectively measuring the concentration of thallium and ammonia nitrogen in the solution by using ICP (inductively coupled plasma), and calculating the adsorption quantity of thallium. The test results of the influence of the adding amount of the composite biochar on the thallium and ammonia nitrogen removal are shown in the figure 1, the figure 2 and the figure 3.
As can be seen from the figures 1, 2 and 3, when hypochlorite is not added to remove pure thallium and pure ammonia nitrogen, the removal efficiency is increased along with the increase of the dosage within the dosage range of 0.25-2 g/L, and under the condition of the dosage of 2g/L, the highest thallium removal efficiency can reach 14.2%, and the highest ammonia nitrogen removal rate can reach 18.5%. When the thallium and ammonia nitrogen mixed liquid is removed without adding hypochlorite, the thallium removal efficiency is increased along with the increase of the dosage within the dosage range of 0.25-2 g/L, the ammonia nitrogen removal efficiency is reduced along with the increase of the dosage, even a negative growth condition is presented, under the condition of the dosage of 2g/L, the thallium removal efficiency can reach 9.5% to the maximum, and the ammonia nitrogen content is increased by 6.36% on the contrary under the condition. When thallium and ammonia nitrogen mixed liquor is removed under the condition of hypochlorite addition, within the dosage range of 0.25-2 g/L, thallium removal efficiency is increased along with the increase of dosage, the removal efficiency reaches the highest point at 2g/L and is 17.4%, ammonia nitrogen is approximately unchanged, and the highest removal efficiency reaches 57.2%.
(2) Influence of hypochlorite dosage on thallium and ammonia nitrogen adsorption
Taking 400ml of Tl+Putting thallium-containing ammonia nitrogen solution with the concentration of 10mmol/L and the ammonia nitrogen concentration of 25mg/L into a 600ml beaker; adjusting the pH value of the thallium-containing ammonia nitrogen solution to 7 by using a NaOH solution and dilute nitric acid; weighing 0.8g of composite biochar material, adding the composite biochar material into the solution, respectively adding 0, 2, 4, 6, 8, 10 and 12mmol of sodium hypochlorite, carrying out shake table reaction for 30min at a constant speed of 150rmp and maintaining the temperature at 30 ℃, respectively measuring the concentration of thallium and ammonia nitrogen in the solution by using ICP (inductively coupled plasma), and calculating the adsorption quantity of thallium. The test results of the influence of the hypochlorite dosage on the absorption of thallium and ammonia nitrogen are shown in figure 4.
As can be seen from FIG. 4, the thallium and ammonia nitrogen removal efficiency increases rapidly with the increase of hypochlorite dosage, and under the condition of hypochlorite dosage of 30mmol/L, the thallium removal rate is as high as 99.7%, which is almost completely removed, while the ammonia nitrogen removal rate is as high as 62.8%. It can be seen that hypochlorite has a very good effect on the removal of both.
(3) Influence of initial pH and mixed solution pH on thallium and ammonia nitrogen removal of composite biochar
Taking 400ml of Tl+Putting thallium-containing ammonia nitrogen solution with the concentration of 10mmol/L and the ammonia nitrogen concentration of 25mg/L into a 600ml beaker; respectively adjusting the pH value of the thallium-containing ammonia nitrogen solution to 2, 4, 6, 8 and 10 by using NaOH solution and dilute nitric acid; weighing 0.8g of composite biochar material, adding 12mmol of sodium hypochlorite into the solution, carrying out shake table reaction for 30min at a constant speed of 150rmp and at a temperature of 30 ℃, respectively measuring the concentration of thallium and ammonia nitrogen in the solution by ICP, and calculating the adsorption quantity of thallium. The test results of the influence of the initial pH on the removal of thallium and ammonia nitrogen by the composite biochar are shown in FIG. 5.
Taking 400ml of Tl+Putting thallium-containing ammonia nitrogen solution with the concentration of 10mmol/L and the ammonia nitrogen concentration of 25mg/L into a 600ml beaker; weighing 0.8g of composite biochar material, adding the composite biochar material into the solution, and adding 12mmol of sodium hypochlorite; respectively adjusting the pH value of the mixed solution to 2, 4, 6, 8 and 10 by using NaOH solution and dilute nitric acid; carrying out shake table reaction for 30min at a constant speed of 150rmp and maintaining the temperature of 30 ℃, respectively measuring the concentration of thallium and ammonia nitrogen in the solution by ICP, and calculating the adsorption quantity of thallium. The test results of the influence of the pH value after mixing on the removal of thallium and ammonia nitrogen by the composite biochar are shown in figure 6.
As can be seen from fig. 5 and 6, the thallium removal efficiency increases substantially with increasing pH, and 59.1% removal efficiency can be achieved under strongly alkaline conditions, and the optimum ammonia nitrogen removal conditions are initial pH 4 and 52.2% removal efficiency, but the thallium removal rate is low, which is not suitable for adsorption removal of thallium. It can be seen that the optimal conditions for thallium and ammonia nitrogen are not the same at the initial pH, and there is a removal conflict. Different from the initial pH, when the pH is 4 or 10 after the reaction, the thallium removal rate reaches 69.7 percent and 70.2 percent respectively, the removal effect is good under the conditions of two pH values, while the ammonia nitrogen achieves 45.7 percent under the condition of 10 pH value, and the ammonia nitrogen removal effect is poor under the condition of strong acid. Combining two different pH experimental results, the optimal thallium removal condition is to adjust the pH to 10 after the reaction, the optimal ammonia nitrogen removal condition is to adjust the initial pH to 4, and if the two kinds of pollution are removed to the maximum, the pH adjustment is carried out before the reaction and after the reaction.
(4) Influence of temperature on thallium and ammonia nitrogen removal of composite biochar
Taking 400ml of Tl+Putting thallium-containing ammonia nitrogen solution with the concentration of 10mmol/L and the ammonia nitrogen concentration of 25mg/L into a 600ml beaker; adjusting the pH value of the thallium-containing ammonia nitrogen solution to 10 by using a NaOH solution and dilute nitric acid; weighing 0.8g of composite biochar material, adding the composite biochar material into the solution, and adding 12mmol of sodium hypochlorite; respectively setting the temperature of the shaking table at 15, 20, 25 and 30 ℃; carrying out shake table reaction for 30min under the constant speed of 150rmp, respectively measuring the concentration of thallium and ammonia nitrogen in the solution by ICP, calculating the adsorption quantity of thallium, and simultaneously measuring the pH of the result after the reaction. The test results of the influence of pH on the removal of thallium and ammonia nitrogen by the composite biochar are shown in FIG. 7.
As can be seen from FIG. 7, in the range of 15 ℃ to 35 ℃, the low temperature can increase the thallium and ammonia nitrogen removal efficiency, and the high temperature can inhibit the adsorption of thallium and ammonia nitrogen by the composite biochar. Under the condition of 15 ℃ and the initial pH value of 10, the removal rate of thallium is close to 70 percent, and the removal rate of ammonia nitrogen is 48.6 percent. According to the data in the figure, the effect of temperature on thallium removal is small, the effect on ammonia nitrogen removal is large, and the difference between the highest efficiency and the lowest efficiency is close to 30%. Therefore, the composite biochar optimally removes thallium and ammonia nitrogen at the temperature of 15 ℃.
Example 2
The embodiment provides the kinetic analysis and the characterization technical analysis of the adsorption of the composite biochar to the thallium and the ammonia nitrogen in the solution.
The material source for this example was the same as example 1.
(1) Characterization technical analysis of material before and after thallium adsorption in composite biochar adsorption solution
For the surface characteristic analysis of the composite biochar, the morphology and the element composition of the material before and after adsorption are mainly observed through SEM and EDS, and surface functional groups before and after adsorption of the material are measured through FT-IR; analyzing the stability of the colloidal dispersion system through the ZETA point position; analyzing the components and valence states of thallium and oxygen before and after adsorption through XPS; an XRD (X-ray diffraction) pattern of the material is measured by an X-ray powder diffractometer; and (4) measuring data such as BET specific surface area and the like of the composite biochar before adsorption.
Fig. 8 is SEM images before and after adsorption of the composite biochar. The microscopic morphology of the composite biochar can be observed by utilizing a scanning electron microscope through different magnification factors, the composite biochar is shown to have no fixed morphological structure and is a substance with an irregular and uniform shape, comparison between (a) and (b) in fig. 8 shows that the adsorbed composite biochar material adsorbs a new substance on the surface, zero-valent manganese loaded on the biochar material and an adsorption effect on thallium can be determined, and the composite biochar material before and after adsorption is in an irregular shape, which indicates that the composite biochar material has good stability. BET analysis shows that the average particle size of the composite biochar material nano particles prepared by the experiment is 308.815A, is larger than the particle size diameter of thallium ions, and has the specific surface area of 194.2911m2Per g, micropore area 128.8401m2The/g shows that the composite biochar has larger surface area and developed pore structure. These data all indicate that the composite biochar has good conditions for thallium adsorption.
FIG. 9 shows the X-ray diffraction patterns before and after adsorption of the composite biochar. As can be seen from the figure, two peaks were shown at 31.5 ℃ and 51.5 ℃ after the reaction, and the material shown was TiO2The diffraction peak is sharp, and the baseline is smooth, which shows that the crystallinity of the material is better. And part of documents show that the composite biochar with poor crystallinity and large specific surface area has a good thallium adsorption effect, so that the material can be obtained to have good thallium adsorption capacity.
Table 1 shows EDS analysis before and after adsorption of the composite biochar. Table 1 shows that the biochar material is well loaded with zero-valent manganese, a small amount of elements such as Fe are contained in addition to elements such as C, O, Mn, and the comparison of the element composition before and after the reaction shows that the material adsorbs thallium.
TABLE 1 EDS analysis before and after adsorption of composite biochar
Figure BDA0003217933030000111
FIG. 10 shows a compound raw materialFourier transform infrared spectrum analysis before and after carbon adsorption. The results in FIG. 10 show that the absorption peaks of the infrared spectra of the composite biochar before and after adsorption are substantially consistent: at a wave number of 3459cm-1、2503cm-1、2138cm-1、1792cm-1、992cm-1、618cm-1All have absorption. 3459cm-1The peak is a telescopic vibration area of O-H bonded by hydrogen in water, which shows that a large amount of water is adsorbed on the surface of the material after reaction; 2503cm-1The peak at (B) is an absorption band of carboxyl group in water, and the carboxyl group peak shifts in a low wave number direction after the reaction due to the formation of dimer. 2138cm-1Where is the absorption wavelength range of the triple bond and cumulative double bond regions, indicating that carbon-carbon bonds are linked by triple bonds or carbon-nitrogen bonds are linked by double bonds in the material. 1792cm-1The position is a bending vibration absorption peak of carbonyl, which indicates that Mn-OH functional groups exist on the surface of the material; 992cm-1Is a C-H out-of-plane bending vibration region, 618cm-1Stretching vibration of Mn-O.
From the above analysis, it can be seen that thallium is mainly absorbed by the composite biochar through ion exchange, complexation and physical adsorption between surface functional groups such as-OH and thallium ions.
FIG. 11 is an XPS spectrum of Tl4f of the material after adsorption of the composite biochar material. A certain amount of the adsorbed composite biochar is taken for freeze drying, characterization analysis is carried out on the composite biochar by XPS, and the content and valence state of elements relevant to the experiment are analyzed, so that the reaction generated in the adsorption process is judged, wherein a Tl element spectrogram is shown in figure 11. The material before reaction does not contain thallium, the binding energy of Tl4f5-2 after reaction is 123.4eV, the binding energy of Tl4f7-2 after reaction is 119eV, and the difference between spin orbit energy levels is 4.4 eV. As shown in FIG. 11, the thallium adsorbed by the composite biochar has two valence states (Tl (I) and Tl (III)), wherein the Tl (I) content is 36.54%, the Tl (III) content is 64.46%, and the ratio of the first valence state to the second valence state is 1:1.76, which indicates that the composite biochar can effectively adsorb thallium, and monovalent thallium is oxidized into trivalent thallium in the adsorption process, so that redox reaction occurs.
FIG. 12 shows XPS spectra of O1s before and after adsorption of the composite biochar material, wherein (a) is before adsorption and (b) is after adsorption. As is clear from FIG. 12, the light of O1s was observed after the reactionThe spectrum has one more oxide peak, only two peaks are available before reaction, and the oxide is Mn-O, Mn-O-Tl and the like because zero-valent manganese is loaded in the material and can be judged according to an XPS standard energy spectrum manual; the peak of hydroxide or H-O-C is reduced compared with that before adsorption, which indicates that hydroxyl is involved in the adsorption reaction process, and H in the hydroxyl+Exchanging with monovalent thallium; the reason for the decrease of C-O is probably that the surface of the composite biochar material adsorbs oxygen, and 532eV is also the binding energy peak range of chemically adsorbed water.
In conclusion, the adsorption of the composite biochar material to thallium mainly depends on an oxidation reaction and an adsorption reaction which are not interfered with each other and exist simultaneously, wherein-OH functional groups on the surface of the composite biochar play an important role, and adsorbed monovalent thallium is oxidized into trivalent thallium and then adsorbed onto the surface of the composite biochar until attachment points are all used to reach reaction equilibrium.
(2) Adsorption kinetics analysis of thallium front and back materials in composite charcoal adsorption solution
FIG. 13 is a graph showing the kinetics of adsorption of thallium in the composite biochar adsorbing solution. Table 2 shows the first and second dynamic models of thallium adsorption by composite biochar. As can be seen from FIG. 13 and Table 2, the adsorption rate of thallium by the composite biochar is slow, and the correlation coefficient R is fitted by a first-order kinetic model2The adsorption process is only 0.369, and the theoretical equilibrium adsorption amount is different from the actual amount, so that the pseudo first-order kinetic model is not suitable for the adsorption process of the material. And the second order dynamics model simulation coefficient R20.957, and the theory is more consistent with the reality, so the quasi-second order kinetic model is more suitable for the material.
TABLE 2 Primary and secondary kinetics model of thallium adsorption by composite biochar
Figure BDA0003217933030000141
FIG. 14 is an isothermal adsorption curve of thallium in composite biochar adsorption solution. Table 3 shows the Langmuir and Freundlich fitting parameters for composite biochar adsorption of Tl (I). Adsorption isotherms are used to determine the adsorbate of the adsorbentAn indication of the effectiveness of the adsorption. The Langmuir adsorption model is based on the following assumptions: the surface of the adsorbing material is uniform, the adsorbed objects are not influenced mutually, the adsorption is monomolecular adsorption, and finally the dynamic balance can be achieved. The Freundlich model assumes that adsorption occurs in multiple layers on heterogeneous surfaces. Correlation coefficient R of Langmuir equation fitting20.9956 is greater than the correlation coefficient R of the Freundlich equation fit20.9952, the Langmuir equation is therefore more applicable to the description of the thallium adsorption process by composite biochar, indicating that the adsorption of this material is monolayer adsorption. The adsorption capacity q of the Langmuir equation is 32.443mg/g at an equilibrium concentration of 150mg/L and 2.29mg/g at 50mg/L, which indicates that the adsorbent is more suitable for treating low-concentration wastewater containing thallium.
TABLE 3 Langmuir and Freundlich fitting parameters for composite biochar adsorption Tl (I)
Figure BDA0003217933030000151
In conclusion, the composite biochar is a material with abundant functional groups, a good pore structure and a large specific surface area, and can be used as a material for adsorbing heavy metals.
As described above, the present invention can be preferably implemented, and the above-mentioned embodiments only describe the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various changes and modifications of the technical solution of the present invention made by those skilled in the art without departing from the design spirit of the present invention shall fall within the protection scope defined by the present invention.

Claims (6)

1. A method for removing thallium-containing ammonia nitrogen wastewater is characterized in that composite biochar and hypochlorite are added into the thallium-containing ammonia nitrogen wastewater; the shaddock peel biochar prepared by taking shaddock peel as a material through a carbon thermal method is loaded with zero-valent manganese, and the load ratio of the shaddock peel biochar to the zero-valent manganese is 1: 0.3; the composite charcoal adsorbs monovalent thallium and trivalent thallium, and the monovalent thallium is oxidized into the trivalent thallium in the adsorption process; the hypochlorite dosage is within the range of not more than 30mmol/L, and the thallium and ammonia nitrogen synchronous removal rate is increased along with the increase of the hypochlorite dosage.
2. The method of claim 1, wherein the method for loading zero-valent manganese on the shaddock peel biochar is as follows: adding the shaddock peel biochar into an aqueous solution containing divalent manganese, slowly adding an aqueous solution containing tetrahydroborate, washing with water, centrifuging, and freeze-drying; the aqueous solution containing the divalent manganese is an aqueous solution of manganese sulfate; the aqueous solution containing tetrahydroborate is an aqueous solution of sodium borohydride or potassium borohydride; the contact with air is minimized during the addition of the aqueous solution containing tetrahydroborate.
3. The method of claim 1, wherein the method for preparing the shaddock peel biochar by the carbothermal method comprises: drying and crushing the shaddock peel, sieving by a 100-mesh sieve, and placing in a tubular furnace, setting the temperature at 500 ℃ and firing for 1 h.
4. Use of the method according to claims 1 to 3 for the treatment of thallium-containing ammonia nitrogen wastewater.
5. Use according to claim 4, characterized in that the conditions for thallium adsorption are: the adding amount of the composite biochar is 2.0g/L, the adding amount of hypochlorite is 30mmol/L, the initial pH of thallium-containing ammonia nitrogen wastewater is 10, the reaction temperature is 15 ℃, and the adsorption time is 30 min.
6. Use according to claim 4, characterized in that the conditions for removing ammonia nitrogen are: the adding amount of the composite biochar is 0.25g/L, the adding amount of hypochlorite is 30mmol/L, the initial pH of thallium-containing ammonia nitrogen wastewater is 4, the reaction temperature is 15 ℃, and the adsorption time is 30 min.
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