CN113578265A

CN113578265A - Preparation and application method of modified corncob biochar adsorbent

Info

Publication number: CN113578265A
Application number: CN202110896514.XA
Authority: CN
Inventors: 臧淑艳; 邱洪未; 崔立志; 周华峰; 王娟
Original assignee: Shenyang University of Chemical Technology
Current assignee: Shenyang University of Chemical Technology
Priority date: 2021-08-05
Filing date: 2021-08-05
Publication date: 2021-11-02

Abstract

The invention discloses a preparation method and an application method of a modified corncob biochar adsorbent, and relates to a preparation method and an application method of an adsorbent. The method realizes the simultaneous comprehensive treatment of ASA and As (v) composite polluted wastewater, which is more in line with the actual situation of industrial and agricultural pollution, makes up for the defect that only single pollution can be treated in the past, uses the corncob biochar with wide raw material source, low cost and capability of recycling, and has the characteristics of energy conservation, high efficiency and no secondary pollution; the method is simple to operate, easy to realize industrialization, can provide a feasible way for large-scale production of the purifying agent, and is a wastewater/sediment treatment method containing ASA and As (v) with great development prospect.

Description

Preparation and application method of modified corncob biochar adsorbent

Technical Field

The invention relates to a preparation method and application of a biochar adsorbent, in particular to a preparation method and application method of a modified corncob biochar adsorbent.

Background

P-aminobenzene arsenic acid is also called arsanilic acid (ASA) and is an organic arsenic preparation. ASA is widely used as a feed additive because of its effects of promoting growth, increasing feed utilization rate, improving appearance of livestock and poultry, etc. A large number of researches show that although the arsenic preparation is very easy to be absorbed by livestock and poultry, the utilization rate is very low, generally about 5 percent, and unabsorbed arsenic enters soil and water environment in a compost form after being metabolized by animals and is irrigated and washed by rainwater. As the content of arsenic in drinking water and soil exceeds the standard since Xinjiang in the early 80 s of the 20 th century, people drink water in the area for a long time to cause arsenic poisoning, and 12 provinces (regions) in China successively find arsenic disease areas, which has a very close relationship with factories and farms producing arsenic preparations and using arsenic preparations in a long-term and accumulated way. At present, the treatment of arsenic pollution in wastewater at home and abroad is only limited to single organic arsenic or inorganic arsenic, so that the research on the treatment and removal of organic arsenic and inorganic arsenic composite pollution wastewater in wastewater has great significance.

At present, the arsenic treatment method mainly comprises an advanced oxidation method, a chemical precipitation method, a biological method, an adsorption method and the like. The novel advanced oxidation technology is various, but the treatment capacity is limited, so that industrial batch application cannot be obtained, some methods are still in a research stage, the treatment cost of a chemical method is high, secondary pollution is often caused, the treatment period is long although the cost of a biological method is low, and the experimental conditions are harsh. Compared with other water treatment technologies, the adsorption method has the advantages of relatively large specific surface area, high arsenic adsorption removal rate, no need of other reagents for assistance during adsorption, no secondary pollution, simplicity and feasibility. But an excellent and cheap adsorbing material is lacked at present.

At present, the corncobs in China are not only industrialized raw material, base material, feed and novel energy utilization, but also about 3800 ten thousand of corncobs are left, and most of the corncobs are directly used as domestic fuel to form corncob biochar. The biochar mainly comprises C, H, O and other elements and has strong adsorbability. Fe is a good arsenic removal reagent, Fe and arsenic can form iron-arsenic coprecipitation, and arsenic in sewage can be successfully removed. Therefore, the invention provides how to load Fe on the corncob biochar and explore the adsorption condition and mechanism of the composite arsenic solution.

Disclosure of Invention

The first purpose of the invention is to provide NaHCO which is a biochar prepared by taking corncobs as raw materials and calcining the corncobs at high temperature₃The specific surface area of the pore-increasing agent is enlarged. Utilizes the characteristic of large specific surface area to load Fe³⁺And (3) taking NaOH as a precipitator, and washing, filtering and drying to obtain the modified corncob biochar adsorbent. Meanwhile, the modified adsorbent is used for simultaneously removing organic arsenic (ASA) and inorganic arsenic (As (V)) in the wastewater, thereby providing a basis for treating the composite arsenic-polluted wastewater.

The purpose of the invention is realized by the following technical scheme:

a preparation method of a modified corncob biochar adsorbent comprises the following preparation processes:

(1) placing the corncobs in a muffle furnace, calcining for 1.5 h at 500 ℃, naturally cooling, taking out, and sieving with a 180-mesh sieve;

(2) with 50 mL saturated NaHCO₃Modifying the carbonized 10 g of corncobs by the solution, and firstly carrying out ultrasonic treatment in an ultrasonic cleaning machine for 5 min; then stirring in a magnetic stirrer in a water bath for 30 min, standing for 30 min, centrifuging, drying for 4 h, washing with distilled water to neutrality, and drying in an oven;

(3) 8.0 g of the resulting pellets were placed in 2 mol/L100 mL FeCl₃·6H₂Performing ultrasonic treatment for 5 min in O solution, then slowly dripping 1 mol/L NaOH solution while stirring until turbid precipitate appears, and then titratingFinishing;

(4) stirring for 20 min, labeling the suspension, standing in the shade for 4 hr, washing with distilled water for 2-3 times, drying in oven for 12 hr, sieving with 180 mesh sieve, packaging, and sealing.

The preparation method of the modified corncob biochar adsorbent is characterized in that the adsorbent is loaded with Fe by an ultrasonic method³⁺。

A method for applying a modified corncob charcoal adsorbent to purify ASA and As (v) combined polluted wastewater simultaneously comprises the following specific steps:

(1) adding the modified adsorbent into the composite polluted wastewater containing ASA and As (v) at normal temperature, wherein the using amount of the adsorbent is 0.4 g/L by mass concentration;

(2) adding 0.1 mol/L NaOH and 0.1 mol/L HCl solution into the composite polluted wastewater treated in the step (1), and adjusting the initial pH value of the composite polluted wastewater to reach 4.0-5.0;

(3) placing the compound polluted wastewater with the pH value adjusted in the step (2) of about 4.0-5.0 into a shaking table with the rotating speed of 180 r/min, and shaking for 2 h;

(4) the residual concentration of ASA and As (v) in the composite wastewater in the shaking table was measured and the removal effect was checked. When the treated composite polluted wastewater reaches less than 10 mug/L, the composite polluted wastewater is centrifuged to discharge liquid.

The application method of the modified corncob charcoal adsorbent comprises the preparation of ASA and As (v); wherein: the preparation method of the waste liquid of 10 mg/LASA +1mg/LAs (V) comprises the following steps:

(1) preparing 100 mg/LAs (V) mother solution, and accurately weighing NaAsO₂0.0173 g is dissolved in a 100 mL volumetric flask;

(2) 100 mg/LASA +10mg/LAs (V) mother liquor, accurately weighing ASA 0.025 g and dissolving in a beaker, then weighing 25 mL from 100 mg/LAs (V) mother liquor, and jointly weighing in a 250 mL volumetric flask;

(3) the assay was performed using 10 mg/LASA +1mg/LAs (V), diluted 100 mg/LASA +10mg/LAs (V) stock solution.

The application method of the modified corncob biochar adsorbent is characterized in that a step-by-step dilution method is adopted in the preparation method of the 10 mg/LASA +1mg/LAs (V) waste liquid.

The invention has the advantages and effects that:

the preparation method takes agricultural waste corncobs as raw materials, and the raw materials are wide in source, low in price and easy to obtain, so that the preparation method has a good application prospect. The invention aims to provide a method for preparing biochar by using corncobs as raw materials through high-temperature calcination, and sodium bicarbonate is used as a pore-increasing agent to enlarge the specific surface area of the biochar. By utilizing the characteristic of large surface area, Fe3+ ions are loaded, NaOH is used as a precipitator, and the adsorbent loaded with the hydroxyl iron oxide corncob biochar is obtained by washing, filtering and drying.

Meanwhile, the modified adsorbent is used for simultaneously removing organic arsenic (ASA) and inorganic arsenic (As (V)) in the wastewater, thereby providing a basis for treating the composite arsenic-polluted wastewater.

The invention takes the homemade corncob biochar As the raw material, Fe is loaded on the corncob biochar, and ASA and As (v) composite polluted wastewater is absorbed at the same time, and the prepared adsorbent has the advantages of no secondary pollution, low price, simple method and the like. The invention realizes the following specific innovation:

(1) the method realizes the simultaneous comprehensive treatment of ASA and As (v) composite polluted wastewater, which is more in line with the actual situation of industrial and agricultural pollution and makes up the defect that only single pollution can be treated in the past;

(2) the used corncob biochar raw materials have wide sources and low cost, can be recycled, and have the characteristics of energy conservation, high efficiency and no secondary pollution;

(3) the prepared purifying agent has large specific surface area, contains various functional groups, can simultaneously perform chemical adsorption and physical adsorption with ASA and As (v), and has good arsenic fixing effect. The method is simple to operate, easy to realize industrialization, can provide a feasible way for large-scale production of the purifying agent, and is a wastewater/sediment treatment method containing ASA and As (v) with great development prospect.

Drawings

FIG. 1 a is a scanning electron microscope chromatogram of an unmodified adsorbent, b of a modified adsorbent, c of a modified adsorbent after adsorption of arsenic;

FIG. 2 is an FTIR spectrum of an unmodified adsorbent, a modified adsorbent, and a modified adsorbent;

figure 3 is an XRD pattern of the unmodified adsorbent, the modified adsorbent, and the modified adsorbent.

Detailed description of the preferred embodiments

The present invention will be described in detail with reference to examples.

(1) accurately weighing corncobs, putting the corncobs into a crucible to fill the crucible, putting the crucible into a muffle furnace to calcine the corncobs for 1.5 h at 500 ℃, taking the corncobs out after natural cooling, and sieving the corncobs with a 180-mesh sieve for later use.

(2) With 50 mL saturated NaHCO₃Modifying carbonized 10 g corn cob with the solution by ultrasonic cleaning for 5 min

(3) Then stirring in a magnetic stirrer in a water bath for 30 min, standing for 30 min, centrifuging, drying for 4 h, washing with distilled water to neutrality, and drying in an oven.

(4) 8.0 g of the resulting pellets were placed in 2 mol/L100 mL FeCl₃·6H₂Performing ultrasonic treatment for 5 min in O solution, then slowly dripping 1 mol/L NaOH solution while stirring until turbid precipitate appears, and ending the titration

(5) Stirring for 20 min, labeling the suspension, standing in the shade for 4 hr, centrifuging, washing with distilled water for 2-3 times, drying in oven for 12 hr, sieving with 180 mesh sieve, packaging, and sealing.

The preparation method of the modified corncob biochar adsorbent is saturated NaHCO₃The solution was 7.5 g NaHCO₃Dissolved in 100 mL of distilled water.

According to the preparation method of the modified corncob biochar adsorbent, after each substance is modified, the modified corncob biochar adsorbent is washed to be neutral by using deionized water.

The Fe modified corncob biochar adsorption purification arsenic composite wastewater 10mg/L ASA +1mg/L As (v) was obtained by the method, and the results were As follows:

test 1: effect test on reaction time

200 mL of the composite solution having a mass concentration of 10mg/L ASA +1mg/L As (v) was measured and put in a 500 mL Erlenmeyer flask with 0.12 g of modified adsorbent. The initial pH of the solution was adjusted to 6.0. + -. 0.2 with 0.1 mol/L HCl or 0.1 mol/L NaOH and the same pH was maintained throughout the adsorption. Then, the mixture was shaken in a digital double-layer air bath shaker at a speed of 180 rpm/min and at a temperature of 30 ℃. + -. 1 ℃. Samples were taken at 9 time points of 0.083 h, 0.25 h, 0.5 h, 1 h, 2 h, 4 h, 6 h, 8 h, 10 h, respectively. Each sample was taken at 1 mL, and immediately after sampling, the sample was passed through a 0.22 μm filter. The concentrations of ASA and As (v) in the solution were measured by HPLC and atomic fluorescence photometer, respectively, and the equilibrium time under these conditions was found to be 6 h from the experimental results.

Test 2: effect test of adsorbent addition amount

100 mL of the composite solution with the mass concentration of 10mg/L ASA +1mg/L As (v) is weighed and put into a 250 mL conical flask, and the adding amount of the modified adsorbent is 0.2 g/L, 0.3 g/L, 0.4 g/L, 0.6 g/L, 1.0 g/L and 1.2 g/L in sequence. The initial pH of the solution was adjusted to 6.0. + -. 0.2 with 0.1 mol/L HCl or 0.1 mol/L NaOH and maintained at the same pH throughout the adsorption process. Then, the mixture was shaken in a digital double-layer air bath shaker at a speed of 180 rpm/min and at a temperature of 30 ℃. + -. 1 ℃. Samples were taken at 6 h equilibration time. Each sample was taken at 1 mL, and immediately after sampling, the sample was passed through a 0.22 μm filter. The concentrations of ASA and As (v) in the solution were measured by HPLC and atomic fluorescence photometer, respectively, and the optimum amount of the adsorbent was 0.4 g/L under these conditions.

Test 3: effect test of initial pH

50 mL of ASA solution with a mass concentration of 10mg/L ASA +1mg/L As (v) was measured and placed in a 100 mL Erlenmeyer flask with 0.4 g/L of modified adsorbent. The initial pH of the solution was adjusted to 4.0, 5.0, 6.0, 7.0, 8.0, 9.0 with 0.1 mol/L HCl or 0.1 mol/L NaOH and maintained at the same pH throughout the adsorption. Then, the mixture was shaken in a digital double-layer air bath shaker at a speed of 180 rpm/min and at a temperature of 30 ℃. + -. 1 ℃. At an equilibration time of 6 h, samples were taken. Each sample was taken at 1 mL, and immediately after sampling, the sample was passed through a 0.22 μm filter. The concentrations of ASA and As (v) in the solution were determined by HPLC and atomic fluorescence photometer, respectively, and the optimum pH under these conditions was found to be 4.0-5.0.

Test 4: test for Effect of temperature

100 mL of the composite solution with the mass concentration of 10mg/L ASA +1mg/L As (v) was weighed and placed in a 250 mL beaker, and the addition amount of the modified adsorbent was 0.4 g/L. The initial pH of the solution was adjusted to 4.0-5.0 with 0.1 mol/L HCl or 0.1 mol/L NaOH and maintained at the same pH throughout the adsorption process. Then, the mixture is placed in a water bath kettle for magnetic stirring, the rotating speed is 180 rpm/min, and the temperature is 20 +/-1 ℃, 30 +/-1 ℃ and 40 +/-1 ℃ in sequence. Samples were taken at 6 h equilibration time. Each sample was taken at 1 mL, and immediately after sampling, the sample was passed through a 0.22 μm filter. The concentration of ASA and As (v) in the solution was measured by HPLC and atomic fluorescence photometer, respectively, and the optimum temperature was determined to be 20 ℃ in consideration of economic factors.

After the optimization of the conditions, the influence of the optimized experimental conditions on the time is considered, and after the reaction is carried out for 2 hours, the removal rate of ASA and As (v) reaches over 90 percent, and then gradually becomes gentle. The optimum reaction time was determined to be 2 h in consideration of economic conditions.

Therefore, when the adsorbent prepared by the method is used for simultaneously adsorbing ASA and As (v) composite pollution, the using concentration of the adsorbent is 0.4 g/L by mass, the reaction temperature is about 20 ℃, the reaction pH is 4.0-5.0, and the reaction time is 2 h.

In conclusion, the invention completely discloses the corncob biochar and FeCl₃·6H₂The method for preparing the adsorbent and purifying the ASA and As (v) combined polluted wastewater by using O As a raw material and NaOH As a precipitator simultaneously comprises the following specific steps:

(2) adding 0.1 mol/L NaOH and 0.1 mol/L HCl solution into the composite polluted wastewater treated in the step (1), and adjusting the initial pH value of the composite polluted wastewater to enable the pH value to reach about 4.0-5.0;

(3) placing the compound polluted wastewater with the pH value adjusted in the step (2) of about 4.0-5.0 into a shaking table with the rotating speed of 180 r/min, and shaking for 2 hours;

The preparation method of the modified adsorbent comprises the step of preparing the modified adsorbent by NaHCO₃、FeCl_3`6H₂O。

The above description is further detailed in connection with the preferred embodiments of the present invention, and it is not intended to limit the practice of the present invention to these descriptions. Those skilled in the art to which the invention pertains will appreciate that alterations, modifications, substitutions, combinations, and simplifications made without departing from the spirit of the invention are intended to be equivalent permutations, and fall within the scope of the invention. As can be seen from FIG. 1, the unmodified corncob is in a flocculent porous structure and has a large specific surface area, iron can be observed to be loaded on the corncob biochar, the aggregation degree is high, pore channels are blocked, and granular objects are widely distributed in the pores and on the surface. The characterization analysis of the reacted material shows that the sample after the modified corncob adsorbs arsenic is in a sheet structure and has a smooth surface.

From FIG. 2, it can be seen that the structure of the biochar functional group of the corncob before and after modification and after adsorption is not significantly changed, wherein the structure is 3361 cm^-1、3379 cm^-1、3384 cm^-1The wider absorption band is associated with OH functional groups, but the strength is slightly different, and the strength of the modified adsorbent is higher; at 2852 cm^-1The characteristic peak of (A) is the symmetric stretching vibration of the C-H bond, and is at 2922 cm^-1And 2923 cm^-1The characteristic peak is the asymmetric stretching vibration of the C-H bond. As shown in FIG. 2, the modified adsorbent was at 1694 cm^-1、1596.41 cm^-1、1436.84 cm^-1、1261.4 cm^-1、875.78 cm^-1、812.47 cm^-1The characteristic peaks on the left and right disappear, which indicates that the modified adsorbent structure is clearly changed, hydrogen bonds are broken, and fibers are cracked to cause adsorptionThe activity of the adjuvant is enhanced. Some characteristic peaks also disappeared significantly after the modified adsorbent adsorbed arsenic, and the peak intensity was greatly reduced, probably due to the generation of Fe-As coprecipitation.

As shown in fig. 3, the unmodified adsorbent body is amorphous, has a large number of burrs, and shows a broad diffraction peak around 2 θ =20 °, and has a characteristic peak of carbon, because the rice husk and the corn cob have a large amount of cellulose structure. The modified adsorbent has no obvious diffraction peak, but is obviously different from the unmodified corn cob. Substances corresponding to 2 theta =35.59 ° and 40.42 ° of the modified adsorbent by phase analysis are FeO (OH), substances corresponding to 2 theta =36.37 ° and 38.04 ° are Fe (OH)₃Showing that the biochar is loaded with FeO (OH) and Fe (OH)₃A substance. The As-MCCB structure is not significantly changed.

Claims

1. The preparation method of the modified corncob biochar adsorbent is characterized by comprising the following preparation processes:

(3) 8.0 g of the resulting pellets were placed in 2 mol/L100 mL FeCl₃·6H₂Carrying out ultrasonic treatment for 5 min in the O solution, then slowly dripping 1 mol/L NaOH solution while stirring until turbid precipitates appear, and ending the titration;

2. The method for preparing the modified corncob biochar adsorbent according to claim 1, wherein the adsorption is carried outFe supported by ultrasonic method for additive³⁺。

3. A method for applying a modified corncob biochar adsorbent is characterized in that the method for simultaneously purifying ASA and As (v) composite polluted wastewater comprises the following specific steps:

(4) measuring the residual concentration of ASA and As (v) in the composite sewage in the shaking table, and checking the removal effect;

when the treated composite polluted wastewater reaches less than 10 mug/L, the composite polluted wastewater is centrifuged to discharge liquid.

4. The method for applying the modified corncob charcoal adsorbent As claimed in claim 3, wherein the configuration of ASA and As (v); wherein: the preparation method of the waste liquid of 10 mg/LASA +1mg/LAs (V) comprises the following steps:

5. The method for applying the modified corncob biochar adsorbent according to claim 4, wherein the 10 mg/LASA +1mg/LAs (V) waste liquid preparation method adopts a stepwise dilution method.