CN111298769B

CN111298769B - Preparation method and application of lanthanum-modified sycamore biochar

Info

Publication number: CN111298769B
Application number: CN202010132350.9A
Authority: CN
Inventors: 曾薇; 贾子悦; 许欢欢; 李帅帅; 彭永臻
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2020-02-29
Filing date: 2020-02-29
Publication date: 2022-03-22
Anticipated expiration: 2040-02-29
Also published as: CN111298769A

Abstract

A preparation method of lanthanum hydroxide modified biochar belongs to the field of functional materials and environmental water treatment, and is used for removing phosphate in municipal sewage. In the invention, the sycamore fruit balls are used as the raw material of biochar, and after modification with lanthanum, an efficient, economical and environmentally friendly adsorbent La-TC is prepared. For the concentration of phosphorus in municipal sewage of 4-10mg/L, when the dosage of La-TC is 0.3-0.5g/L, the pH of the solution is 3-9, and the temperature is 25-40°C, it can be recovered within 15-20min. 100% removal of phosphate is achieved. At the same time, it has strong anti-interference ability of competing anions, and after three adsorption and desorption cycles, the adsorption rate of La-TC can still reach 100%. In the experiment of removing municipal sewage with a fixed bed column, at a flow rate of 1mL/min, the maximum bed volume of 0.5g-1.0g of La-TC sub-treatment was 420BV-480BV, indicating that La-TC has broad application in practical engineering. Prospects.

Description

Preparation method and application of lanthanum-modified sycamore biochar

Technical Field

The invention discloses a preparation method of lanthanum hydroxide modified biochar, belongs to the field of functional materials and environmental water treatment, and is used for removing phosphate in urban sewage.

Background

Phosphate acts as a limiting nutrient for phytoplankton in water and its unreasonable discharge inevitably leads to eutrophication of water. Research has shown that when the phosphate concentration in the water body reaches 0.02mg/L, the algae can be stimulated to grow and the water bloom phenomenon can be seriously developed. Therefore, the removal of phosphate from the sewage before the sewage is discharged into a receiving water body is of great importance for the protection of the aquatic ecological environment. At present, there are many technical means for removing phosphate in sewage, such as enhanced biological phosphorus removal EBPR, chemical precipitation, ion exchange, membrane treatment technology and adsorption method. The adsorption method has the advantages of high removal capacity for low-concentration phosphate in sewage, targeted adsorption, low cost, simple and convenient operation, no generation of excess sludge and the like, and is considered to be a phosphate treatment means with great potential.

Various adsorbing materials have been widely used for removing phosphate in wastewater, such as metal modified silicon-based porous materials, activated carbon and metal modified activated carbon materials, synthetic metal hydroxides/oxides, and high molecular polymer materials. However, the adsorption performance of different adsorbents is different due to different preparation methods of the base materials, the modified metals and the modified metals, and the suitable adsorption environments are also greatly different. The reported adsorbents generally have the problems of high preparation cost, low adsorption capacity, complex preparation process, unstable adsorption performance, low regeneration efficiency and the like. Therefore, it is imperative to develop an adsorbent which is inexpensive and readily available, has high removal efficiency, and is easily regenerated.

In recent years, biochar derived from biological resources has attracted much attention due to its advantages of being widely available, renewable, environmentally friendly, and the like. The special physical and chemical properties of the biochar such as high surface area, rich porosity, excellent cation exchange capacity, low bulk density and rich functional groups have great advantages when the biochar is used as a carrier material. However, the original biochar functional groups are generally negatively charged and the phosphate removal efficiency is low. After being modified by metal oxide or hydroxide, the modified biological carbon can selectively and efficiently adsorb phosphate, such as Fe/Al/Zr/La modified biological carbon, such as nano modified AlOOH biological carbon, Mg/Al layered double hydroxide modified biological carbon and nano cerium oxide functionalized biological carbon. In contrast, lanthanum metal is a popular candidate metal element for modified biochar because it is environmentally friendly, relatively inexpensive, and has specific affinity for phosphate even at trace levels. In recent years, a plurality of researches on lanthanum modified adsorption materials show that metal lanthanum has various advantages for removing phosphate, wide pH tolerance range, excellent adsorption capacity and stable regeneration capacity. Moreover, most of the existing researches are only carried out under the condition of laboratory water distribution, and the dynamic removal effect of phosphate in actual sewage is still lack of application researches.

The invention is technically different from the prior art and mainly comprises the following two aspects:

(1) the main materials are different: the main material of the invention is from resources and wastes of biological sources, and is prepared by preparing biochar from the sycamore wool fiber for the first time and modifying with lanthanum, so that La-TC with high affinity to phosphate is successfully prepared. The yield of the sycamore is extremely high and easy to obtain, and the recycling of the sycamore can also reduce the environmental pollution caused by the falling of fruit hair from trees.

(2) Research on adsorption performance of the biochar in the fixed bed column for treating P in town sewage: the adsorption capacity of the engineered biochar on P in actual wastewater is not studied in the previous researches. Furthermore, the performance of biochar as a filter medium in a fixed bed filter reactor for adsorbing P in dynamic actual wastewater streams is still unknown. The town sewage is simply filtered and directly flows through the fixed bed with different biochar measures, and the continuous treatment capacity of the town sewage is explored.

Disclosure of Invention

The invention aims to prepare the lanthanum hydroxide modified biochar which can efficiently and quickly adsorb phosphate in urban sewage.

The preparation method of the lanthanum modified sycamore biochar is characterized by comprising the following steps of:

(1) pretreatment of biomass: mixing sodium dioctyl sulfosuccinate with distilled water according to a volume ratio of 1: 5, mixing to obtain a mixed solution, wherein the mass ratio of the syzygium aromaticum fruit balls to the mixed solution is 1: 4, crushing the sycamore ball, putting the crushed sycamore ball into the mixed solution, stirring the mixture for 24 hours at the temperature of between 40 and 60 ℃, separating the mixture to obtain fruit hair, washing the fruit hair, and drying the fruit hair at the temperature of 105 ℃. Soaking the dried fruit hair in 2-3M KOH solution for 2h, performing ultrasonic treatment at 35KHz-40KHz for 30min, and oven drying again.

(2) Preparing biochar: pretreating fruit hair in a tube furnace at 200 deg.C for 30min, and adding N₂Keeping in the air flow for 90min, and finally keeping at 10 deg.C/min^-1The heating rate of (2) is increased to 600 ℃ for heat treatment for 2 h. Grinding the obtained biochar TC, sieving by using a 200-mesh sieve, cleaning to be neutral, and drying.

(3) Preparing lanthanum modified biochar: 300mgTC was added to a solution containing 0.2M 50mL of La (NO)₃)₃·6H₂O Erlenmeyer flask, through the coprecipitation method to add 1M NaOH, to maintain the pH at 11-12, magnetic stirring 24 h. After centrifugation at 6000rpm, a solid precipitate was obtained and washed with water to pH 7-8. And finally, freeze-drying for 24 hours to obtain the lanthanum hydroxide modified biochar La-TC.

The application conditions of the lanthanum modified sycamore biochar are as follows:

the dosage of the La-TC is 0.3-0.5g/L, the pH of the solution is 3-9, and the adsorption rate of the solution to phosphate can reach 100% within 15-20min at the temperature of 25-40 ℃; the adsorption capacity is still 100% after three times of adsorption and desorption cycles; or La-TC is filled in the fixed bed reactor and used as a filter medium to effectively remove phosphate in the dynamic actual wastewater flow; therefore, the material is economic and environment-friendly and has great potential in practical engineering application.

Technical scheme of the invention

Preparing biochar by using sycamore balls, loading lanthanum on the biochar to prepare a composite material La-TC with high selective adsorption capacity on phosphate, adding the La-TC into town sewage with phosphate concentration of 4-10mg/L, and removing phosphate under the conditions that the pH of a solution is 3-9, the reaction temperature is 25-40 ℃ and the adding amount is 0.3-0.5 g/L; using solutions of 0.1M, 0.5M and 1M NaOH as eluent to carry out regeneration experiments on the adsorbed La-TC; and fixed beds with the heights of 0.5g, 0.7g and 1g respectively carry out continuous dynamic adsorption of phosphate in the town sewage.

The invention has the advantages of

Phosphorus and derivatives thereof are almost ubiquitous in modern society, and excessive discharge of phosphorus inevitably causes eutrophication of water bodies. When the phosphate concentration is as low as 0.02mg/L, the growth of algae is stimulated enough, so that the development of a method for economically and efficiently removing phosphate from low-concentration wastewater is urgently needed. The invention prepares the novel lanthanum-modified biochar La-TC and applies the biochar La-TC to urban sewage for continuous dynamic adsorption of phosphate. As a result, it was found that La-TC exhibits excellent pH resistance at a pH in the range of 3 to 9 with an adsorption efficiency of 100%. While the La-TC has high selective adsorption capacity in the presence of competitive anions. When 0.5M NaOH was used as the eluent, the adsorption capacity did not decrease after three regeneration cycles. In the continuous adsorption process of urban sewage, the treatment effect and the model fitting matching degree are good, and the strong practicability is realized.

Innovation point of the invention

(1) According to the invention, the biochar is prepared by using the syzygium barometz balls for the first time and is modified by using lanthanum, so that the green and efficient adsorbent La-TC is successfully prepared. The substrate material has wide sources, is economic and environment-friendly, and the loaded lanthanum is environment-friendly. The adsorbing material has low cost and stable effect.

(2) The method is different from other adsorbing materials which are only applied to batch experiments, and the La-TC continuously and dynamically adsorbs the town sewage in a fixed bed mode, so that the water outlet effect is stable, and the method has practical application value.

Drawings

FIG. 1 influence of different addition ratios on La-TC adsorption effect

FIG. 2 Effect of different pH on La-TC adsorption Effect

FIG. 3 Effect of different temperatures on La-TC adsorption Effect

FIG. 4 Effect of competitive anions on adsorption Effect

FIG. 5 regeneration cycle experiment

FIG. 6 fixed bed column experiment

Detailed Description

Example 1:

mixing sodium dioctyl sulfosuccinate with distilled water by volumeThe ratio of 1: 5, mixing to obtain a mixed solution, wherein the mass ratio of the syzygium aromaticum fruit balls to the mixed solution is 1: 4, crushing the sycamore balls, putting the crushed sycamore balls into the mixed solution, stirring the mixture for 24 hours at 50 ℃, separating to obtain fruit hair, washing the fruit hair, and drying the fruit hair at 105 ℃. Soaking the dried fruit hair in 2.5M KOH solution for 2h, performing ultrasonic treatment at 40KHz for 30min, and drying again. Pretreating fruit hair in a tube furnace at 200 deg.C for 30min, and adding N₂Keeping in the air flow for 90min, and finally keeping at 10 deg.C/min^-1The heating rate of (2) is increased to 600 ℃ for heat treatment for 2 h. And grinding the obtained biochar TC by using a 200-mesh sieve, cleaning to be neutral and drying. 300mgTC was added to a solution containing 0.2M 50mL of La (NO)₃)₃·6H₂In an O Erlenmeyer flask, 1M NaOH was added by coprecipitation to maintain the pH at 11 and magnetic stirring was carried out for 24 h. After centrifugation at 6000rpm, a solid precipitate was obtained and washed with water to pH 7. And finally, freeze-drying for 24 hours to obtain the lanthanum hydroxide modified biochar La-TC.

Determination of the adding amount: phosphate stock solutions were prepared by dissolving potassium dihydrogen phosphate in distilled water and diluted to 10mg/L to investigate the efficiency of La-TC for removal of phosphate from aqueous solutions. The experiment is carried out at the neutral pH and the room temperature, 50mL of phosphorus solution is respectively filled into 150mL volumetric flasks marked with numbers 1-9, and the adding amount of 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8g/L is respectively added, as shown in figure 1, the lowest adding amount required for achieving 100% removal of phosphate can be determined to be 0.4g/L, and the optimal using amount for ensuring the economical efficiency and the high efficiency of the La-TC adsorbent can also be determined.

Example 2:

mixing sodium dioctyl sulfosuccinate with distilled water according to a volume ratio of 1: 5, mixing to obtain a mixed solution, wherein the mass ratio of the syzygium aromaticum fruit balls to the mixed solution is 1: 4, crushing the sycamore balls, putting the crushed sycamore balls into the mixed solution, stirring the mixture for 24 hours at 50 ℃, separating to obtain fruit hair, washing the fruit hair, and drying the fruit hair at 105 ℃. Soaking the dried fruit hair in 2.5M KOH solution for 2h, performing ultrasonic treatment at 40KHz for 30min, and drying again. Pretreating fruit hair in a tube furnace at 200 deg.C for 30min, and adding N₂Keeping in the air flow for 90min, and finally keeping at 10 deg.C/min^-1The heating rate of (2) is increased to 600 ℃ for heat treatment for 2 h. Grinding the obtained biochar TC by a 200-mesh sieve, cleaning to be neutral and drying. 300mgTC was added to a solution containing 0.2M 50mL of La (NO)₃)₃·6H₂In an O Erlenmeyer flask, 1M NaOH was added by coprecipitation to maintain the pH at 11 and magnetic stirring was carried out for 24 h. After centrifugation at 6000rpm, a solid precipitate was obtained and washed with water to pH 7. And finally, freeze-drying for 24 hours to obtain the lanthanum hydroxide modified biochar La-TC.

Influence of pH on La-TC adsorption Properties: 50mL of 10mg/L phosphorus solution is respectively filled into 150mL conical flasks with the labels of 1-10, the pH is adjusted to 3-12 by using 1M HCl and 1M NaOH, then 0.02g of La-TC is added into each conical flask, and the conical flasks are placed into a shaking table to shake for 24 hours. Subsequently, the concentration of phosphorus before and after adsorption was measured by a spectrophotometer, and the pH after completion of adsorption was measured. As shown in FIG. 2, the adsorption efficiency is 100% in the pH range of 3-9, indicating that La-TC has wide pH tolerance.

Example 3:

mixing sodium dioctyl sulfosuccinate with distilled water according to a volume ratio of 1: 5, mixing to obtain a mixed solution, wherein the mass ratio of the syzygium aromaticum fruit balls to the mixed solution is 1: 4, crushing the sycamore balls, putting the crushed sycamore balls into the mixed solution, stirring the mixture for 24 hours at 50 ℃, separating to obtain fruit hair, washing the fruit hair, and drying the fruit hair at 105 ℃. Soaking the dried fruit hair in 2.5M KOH solution for 2h, performing ultrasonic treatment at 40KHz for 30min, and drying again. Pretreating fruit hair in a tube furnace at 200 deg.C for 30min, and adding N₂Keeping in the air flow for 90min, and finally keeping at 10 deg.C/min^-1The heating rate of (2) is increased to 600 ℃ for heat treatment for 2 h. And grinding the obtained biochar TC by using a 200-mesh sieve, cleaning to be neutral and drying. 300mgTC was added to a solution containing 0.2M 50mL of La (NO)₃)₃·6H₂In an O Erlenmeyer flask, 1M NaOH was added by coprecipitation to maintain the pH at 11 and magnetic stirring was carried out for 24 h. After centrifugation at 6000rpm, a solid precipitate was obtained and washed with water to pH 7. And finally, freeze-drying for 24 hours to obtain the lanthanum hydroxide modified biochar La-TC.

Selecting the reaction temperature: a150 mL conical flask, designated by reference numerals 1-8, was filled with 50mL of a phosphate solution having a concentration of 30-100mg/L, 0.02g of La-TC was added thereto, and the mixture was put into a shaker at 25 ℃, 30 ℃, 35 ℃ and 40 ℃ four times and shaken for 24 hours, followed by measuring the phosphorus concentration before and after adsorption with a spectrophotometer. As shown in figure 3, the removal rate of the phosphate can be 100% at 25-40 ℃ for 4-10mg/L, wherein the adsorption speed is fastest and the adsorption capacity is optimal at 35 ℃.

Example 4:

Competitive anion experiments: to further study the selective adsorption capacity of La-TC on phosphate, 50ml of a 10mg/L phosphorus solution was placed in 150ml Erlenmeyer flasks 1-6, 6 Erlenmeyer flasks were blank and SO was added₄ ^2-，NO₃ ^-，HCO₃ ^-，CO₃ ^2-And Cl^-The concentrations of the five anions are respectively 0.01M and 0.1M, which are 10 times and 100 times higher than the concentration of the anion in the municipal sewage. The amount of La-TC added was 0.02g, followed by shaking in a shaker for 24 hours. SO at two concentrations, as shown in FIG. 4₄ ^2-，NO₃ ^-Has no influence on the adsorption of phosphorus although HCO₃ ^-，CO₃ ^2-，Cl^-The masking effect on phosphorus adsorption is enhanced with the increase of the concentration, but the adsorption capacity of more than 85 percent can still be ensured on the whole.

Example 5:

dioctyl sulfosuccinateThe volume ratio of the ester sodium salt to the distilled water is 1: 5, mixing to obtain a mixed solution, wherein the mass ratio of the syzygium aromaticum fruit balls to the mixed solution is 1: 4, crushing the sycamore balls, putting the crushed sycamore balls into the mixed solution, stirring the mixture for 24 hours at 50 ℃, separating to obtain fruit hair, washing the fruit hair, and drying the fruit hair at 105 ℃. Soaking the dried fruit hair in 2.5M KOH solution for 2h, performing ultrasonic treatment at 40KHz for 30min, and drying again. Pretreating fruit hair in a tube furnace at 200 deg.C for 30min, and adding N₂Keeping in the air flow for 90min, and finally keeping at 10 deg.C/min^-1The heating rate of (2) is increased to 600 ℃ for heat treatment for 2 h. And grinding the obtained biochar TC by using a 200-mesh sieve, cleaning to be neutral and drying. 300mgTC was added to a solution containing 0.2M 50mL of La (NO)₃)₃·6H₂In an O Erlenmeyer flask, 1M NaOH was added by coprecipitation to maintain the pH at 11 and magnetic stirring was carried out for 24 h. After centrifugation at 6000rpm, a solid precipitate was obtained and washed with water to pH 7. And finally, freeze-drying for 24 hours to obtain the lanthanum hydroxide modified biochar La-TC.

Adsorption and desorption experiments: La-TC adsorption experiments were performed under optimal conditions, and the depleted La-TC was regenerated by soaking in NaOH solutions of different concentrations (0.1M, 0.5M, 1M) at 50 ℃ for 8h, as shown in FIG. 5, with the phosphate desorption efficiency increasing with increasing NaOH concentration in three regeneration cycles. The desorption efficiency of phosphate-saturated La-TC was 100%, 88% and 29% at a NaOH concentration of 0.1M. The third regeneration efficiency of 0.5M NaOH was still higher than 98%. Meanwhile, the desorption efficiency in three regeneration cycles of 1M NaOH was 100%. Therefore, the regeneration effect can be well achieved by using NaOH solution with the concentration higher than 0.5M, and the adsorbent is proved to have good application prospect in the field of adsorption.

Example 6:

mixing sodium dioctyl sulfosuccinate with distilled water according to a volume ratio of 1: 5, mixing to obtain a mixed solution, wherein the mass ratio of the syzygium aromaticum fruit balls to the mixed solution is 1: 4, crushing the sycamore balls, putting the crushed sycamore balls into the mixed solution, stirring the mixture for 24 hours at 50 ℃, separating to obtain fruit hair, washing the fruit hair, and drying the fruit hair at 105 ℃. Soaking the dried fruit hair in 2.5M KOH solution for 2h, performing ultrasonic treatment at 40KHz for 30min, and drying again. Pretreating fruit hair in a tube furnace at 200 deg.C for 30min, and adding N₂Keeping in the air flow for 90min, andthen at 10 ℃ min^-1The heating rate of (2) is increased to 600 ℃ for heat treatment for 2 h. And grinding the obtained biochar TC by using a 200-mesh sieve, cleaning to be neutral and drying. 300mgTC was added to a solution containing 0.2M 50mL of La (NO)₃)₃·6H₂In an O Erlenmeyer flask, 1M NaOH was added by coprecipitation to maintain the pH at 11 and magnetic stirring was carried out for 24 h. After centrifugation at 6000rpm, a solid precipitate was obtained and washed with water to pH 7. And finally, freeze-drying for 24 hours to obtain the lanthanum hydroxide modified biochar La-TC.

Fixed bed experiment: fixed bed experiments were performed using town sewage to obtain a bed volume concentration breakthrough curve to determine the continuous adsorption capacity of La-TC. Different amounts (0.5g, 0.75g, 1g) of biochar were packed into a fixed bed and the effect of bed loading on phosphorus removal was investigated at an upflow flow rate of 1 mL/min. The column was first rinsed with distilled water for 5h to remove bubbles and impurities. After stabilization, the column was switched to domestic wastewater to start the column experiment. Column effluent samples were collected at regular intervals. The breakthrough point was considered to be 0.5mg P/L. As shown in FIG. 6, the adsorption curve of domestic wastewater fits well to the Thomas, Yoon-Nelson, Adams-Bohart model.

TABLE 1

Claims

1. a preparation method of lanthanum modified sycamore biochar is characterized in that: dioctyl sulfosuccinate sodium salt and distilled water are mixed by volume ratio 1:5 to obtain a mixed solution, and the sycamore fruit ball and the mixed solution mass ratio are 1:4, put the sycamore fruit balls into the mixed solution after crushing, stir at 40-60 ℃ for 24 hours, separate the fruit hairs, wash them and put them into drying at 105 ℃; put the dried fruit hairs into 2-3M Soak in KOH solution for 2h, ultrasonicate for 30min at 35kHz-40kHz, and dry again;

The fruit hairs were pretreated in a tube furnace at 200 °C for 30 min, kept in N ₂ gas flow for 90 min, and finally heated to 600 °C at a heating rate of 10 °C min -1 for 2 h to obtain biochar TC; the obtained biochar was After TC is ground, sieve with a 200-mesh sieve, clean to neutrality, and dry;

300mg TC after drying was added to the Erlenmeyer flask equipped with 0.2M 50mL La(NO ₃ _{) 3.6H 2} _O , 1M NaOH was added by co-precipitation method, the pH was maintained at 11-12, and the magnetic stirring was performed for 24h; After centrifugation at 6000 rpm, a solid precipitate was obtained, and washed with water until the pH was 7-8; finally, lyophilized for 24 h to obtain lanthanum-modified sycamore biochar La-TC.

2. the method for applying the lanthanum modified plane tree biochar as claimed in claim 1, is characterized in that: adding lanthanum modified plane tree biochar La-TC to the phosphate concentration is in the municipal sewage of 4-10mg/L , the pH of the control solution is 3-9, the temperature is 25-40 ℃, and the dosage of La-TC is 0.3-0.5g/L to adsorb phosphate in municipal sewage;

Alternatively La-TC is packed in a fixed bed reactor as a filter medium to remove phosphate in a dynamic real wastewater stream.