CN107456951A - A kind of rice straw adsorbent of modification and its preparation method and application - Google Patents

Abstract

The invention discloses a modified rice straw adsorbent and its preparation method and application. The adsorbent is rice straw modified by amine groups; the preparation method is as follows: (1) first remove impurities, wash and dry the rice straw Then crush or grind, and sieve; (2) Weigh the treated rice straw in step (1), add epichlorohydrin and dimethylformamide, and stir at 90-100°C for 1-2h to make it fully reaction; then add diethylenetriamine and continue to stir for 1‑2h; finally, add triethylamine and keep the temperature to continue the reaction for 2‑3h; filter the resulting material and rinse it with water; (3) the step (2 ) and dry the rinsed material, that is. The raw material of the modified adsorbent in the present invention is rice straw, which is cheap and easy to obtain; the adsorbent removes chromium and nickel in water through physical methods, and the adsorption efficiency is high. No secondary pollutants are generated during the entire adsorption removal process, and there is no impact Harmful substances produced.

Description

A modified rice straw adsorbent and its preparation method and application

technical field

The invention belongs to the technical field of water treatment, in particular to a modified rice straw adsorbent and its preparation method and application.

Background technique

With the rapid development of industrial production and human society, the problem of environmental pollution has become increasingly serious. Numerous pollutants are discharged into the water environment, among which heavy metal pollutants are highly toxic or carcinogenic and difficult to biodegrade. In addition, heavy metals are easy to accumulate in organisms and then accumulate in organisms or humans through the food chain.

Chromium and nickel ions are widely used in leather, electroplating, cement manufacturing, dye industry, etc. In view of the harmfulness of chromium and nickel and its wide application in various industrial production and manufacturing processes, it is of great significance to effectively remove chromium and nickel from industrial wastewater. There are two main types of common treatment methods for removing chromium and nickel in water, one is traditional treatment methods, including chemical (reduction) precipitation, electrochemical methods, membrane filtration, ion exchange methods, etc.; the other is adsorption methods. Traditional treatment methods have low treatment efficiency, high investment and treatment costs, and inconvenient operation. Compared with many traditional treatment methods, the adsorption method usually uses the porosity of the adsorption material to fix the harmful substances in the sewage on its surface to remove them. At the same time, it has the advantages of no energy consumption, no secondary pollution, and easy operation. Therefore, it is extremely important to find an adsorbent with low cost and high adsorption efficiency.

In recent years, there have been many reports on adsorbents prepared from industrial raw materials such as activated carbon and graphene and their modified materials. Industrial waste such as fly ash and waste rubber can also adsorb heavy metals to a certain extent after treatment. my country is a large agricultural production country. Researchers in the field of agriculture are also thinking about whether it is possible to use agricultural waste materials to prepare adsorbents with good adsorption effect and easy operation. The Chinese patent application with the application number CN2012105884866 discloses an oleic acid modified peanut shell adsorbent. After the peanut shell is pretreated, the peanut shell is modified with oleic acid, n-hexane and sulfuric acid to obtain the modified peanut shell adsorbent. This application mainly uses the carboxyl group in the carboxylic acid to carry out the esterification reaction with the hydroxyl group in the peanut shell. The carboxyl group ionized in the water of the esterification product can form an adsorption effect on heavy metal ions, but this application has a better adsorption effect on heavy metal lead. Treatment of chromium and nickel is not mentioned.

Contents of the invention

In view of the deficiencies of the existing problems, the purpose of the present invention is to provide a modified rice straw adsorbent and its preparation method and application. The raw materials are easy to obtain, the preparation process is simple, and the obtained adsorbent has good adsorption effect. Polluted heavy metals have good adsorption and removal effects, and can be used to solve the problem of difficult treatment of chromium and nickel pollutants in wastewater by existing technologies.

To achieve the above object, the technical solution adopted in the present invention is:

A modified rice straw adsorbent is prepared by pulverizing and pretreating rice straw, then subjecting the pretreated straw to a modifying agent for amino group modification reaction at high temperature, washing and drying.

A preparation method of a modified rice straw adsorbent, comprising the steps of:

(1) Pretreatment of rice stalks: first remove impurities from the rice stalks, wash and dry them, then crush or grind them, and sieve them;

(2) Modification of rice stalks: Weigh the treated rice stalks in step (1), add modifiers for high-temperature modification, the order of adding modifiers is: first add epichlorohydrin and dimethyl formaldehyde For amides, stir at 90-100°C for 1-2h to make it fully react; then add diethylenetriamine, keep warm and continue stirring for 1-2h; finally, add triethylamine, stir for 2-3h at the same temperature; The resulting material is separated by filtration and rinsed with water;

(3) drying the material rinsed in step (2) to obtain the product.

As a preferred technical solution of the present application, in the step (1), after the rice stalks are rinsed with distilled water, they are placed in an oven at 80-100° C. for 20-24 hours, and the dried stalks are crushed and ground and then dried 40-200 mesh sieve.

As a preferred technical solution of the present application, in the step (2), 31-36 mL of modifier is added every time 9-10 g of rice straw is weighed, wherein epichlorohydrin and dimethylamide, dimethicone The volume ratio of ethylenetriamine and triethylamine is 3-3.6:2.5-3:1-1.2:2.5-3; the washing water is deionized water or distilled water.

As a preferred technical solution of the present application, a magnetic stirrer is used in the step (2) to stir.

As a preferred technical solution of the present application, in the step (3), the drying temperature is 80-100° C., and the drying time is 20-24 hours.

The present invention also provides an application of the modified rice straw adsorbent prepared by the above method in adsorbing heavy metals in wastewater.

Rice straw is composed of cellulose, hemicellulose and lignin, etc., which can effectively adsorb heavy metals in the solution. Using waste agricultural materials as adsorbents can not only make full use of waste resources, but also improve the adsorption effect through modification as water treatment. The application of high-efficiency adsorbents in China; amines are easily protonated in acidic environments, and adsorb metal ions through electrostatic attraction and ion exchange to improve adsorption efficiency. Based on the above excellent properties, rice straw can be used for the adsorption of chromium and nickel, and the rice straw modified with amine group has better adsorption performance.

Compared with the prior art, the present invention has the following beneficial effects:

(1) the agricultural material rice stalk used as raw material in the present invention is cheap and easy to obtain;

(2) The modified material is non-hazardous and non-polluting, and the preparation method of the adsorbent is simple and easy to operate;

(3) The final product adsorbs and removes chromium and nickel in water through physical methods, and the adsorption efficiency of chromium and nickel is high, and no secondary pollutants are generated during the entire adsorption removal process, and no substances harmful to the human body are produced;

(4) The present invention makes full use of materials, makes the best use of everything, and achieves the purpose of energy saving and environmental protection.

detailed description

The present invention is described in further detail below in conjunction with embodiment. The reagents or instruments used are not indicated by the manufacturer, and they are all regarded as conventional products that can be purchased through the market.

Example 1

A preparation method of a modified rice straw adsorbent, comprising the following steps:

(1) Pretreatment of rice straw: firstly, the collected rice straw was washed with distilled water, and then dried in an oven at 80° C. for 24 hours. Then the dried straw is crushed and ground and passed through a 100-mesh sieve;

(2) Modification of rice straw: Take 10 g of rice straw to be modified in step 1 and place it in a round bottom flask, add 10.8 mL of epichlorohydrin and 9 mL of dimethylformamide, and place the flask at 100 ° C Under the condition of stirring for 1h, it fully reacted. Subsequently, 3.6 mL of diethylenetriamine was added to the flask, and the stirring was continued at 95° C. for 2 h; finally, 9 mL of triethylamine was added to the flask, and stirring was continued at 90° C. for 3 h. Then, the resulting material was separated by filtration and washed with deionized water;

(3) Put the material obtained in step 2 into an oven at 100°C and bake for 20 hours to obtain the product.

The powder material prepared by the above method is the modified rice straw adsorbent, and the adsorbent is stored in a desiccator for standby.

Example 2

A preparation method of a modified rice straw adsorbent, comprising the following steps:

(1) Pretreatment of rice straw: firstly, the collected rice straw was washed with distilled water, and then dried in an oven at 80° C. for 24 hours. Then the dried stalks are crushed and ground and passed through a 40-mesh sieve;

(2) Modification of rice straw: take 9g of rice straw to be modified in step 1 and place it in a round bottom flask, add 12mL epichlorohydrin and 10mL dimethylformamide, and then place the flask at 90°C Under stirring for 2h, it fully reacted. Then 4 mL of diethylenetriamine was added to the flask, and the stirring was continued for 1 h at 100° C.; finally, 10 mL of triethylamine was added to the flask, and the stirring was continued at 100° C. for 2 h. Then, the resulting material was separated by filtration and washed with deionized water;

(3) Put the material obtained in step 2 in an oven at 80°C for 24 hours to obtain the product.

The powder material prepared by the above method is the modified rice straw adsorbent, and the adsorbent is stored in a desiccator for standby.

Example 3

A preparation method of a modified rice straw adsorbent, comprising the following steps:

(1) Pretreatment of rice straw: first, the collected rice straw was rinsed with distilled water, and then dried in an oven at 100° C. for 24 hours. Then the dried stalks are crushed and ground and passed through a 200-mesh sieve;

(2) Modification of rice straw: take 9.1 g of rice straw to be modified in step 1 and place it in a round bottom flask, add 10 mL of epichlorohydrin and 8.8 mL of dimethylformamide, and then place the flask at 95 Stir at ℃ for 1.4h to fully react. Then, 3.3 mL of diethylenetriamine was added to the flask, and the stirring was continued at 90° C. for 1.6 h; finally, 9 mL of triethylamine was added to the flask, and the stirring was continued at 95° C. for 2.5 h. Then, the resulting material was separated by filtration and washed with deionized water;

(3) Put the material obtained in step 2 in an oven at 95°C for 22 hours to obtain the product.

The powder material prepared by the above method is the modified rice straw adsorbent, and the adsorbent is stored in a desiccator for standby.

The modified rice straw (MRS) obtained in Examples 1-3 and the unmodified rice straw (RS) were used as adsorbents for comparative experiments to verify the effect of the above two adsorbents on the adsorption of chromium and nickel in water. Specifically:

Chromium (VI) and nickel (II) solutions with different concentrations were respectively prepared to test the adsorption effect of the adsorbent on chromium (VI) and nickel (II). Take the adsorbent quality as 0.2g, 0.3g and 0.4g respectively; the concentration of chromium (Ⅵ) solution is 20mg/L, 40mg/L and 60mg/L; the concentration of nickel (Ⅱ) solution is 20mg/L, 40mg/L and 60mg /L. The volumes of chromium (Ⅵ) solution and nickel (Ⅱ) solution are both 50mL.

Under the condition that other conditions remain unchanged, the corresponding adsorption properties of different mass adsorbents for different concentrations of chromium (VI) solutions and nickel (II) in the test examples and comparative examples are shown in Table 1 and Table 2 below, respectively.

Table 1 Treatment effect of rice straw adsorbent chromium (Ⅵ)

Table 2 Treatment effect of rice straw adsorbent nickel(Ⅱ)

Referring to Table 1 and Table 2, comparing the adsorption data of chromium and nickel on rice straw before and after modification, it can be seen that the adsorption performance of modified rice straw has been greatly improved, and the adsorption efficiency has also been greatly increased.

As shown in the above table, the higher the initial concentration of chromium (VI) and nickel (II), the higher the adsorption capacity of the corresponding adsorbent; , even if the amount of adsorbent is increased, the adsorption effect is limited.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.

Claims (7)

1. A modified rice stalk adsorbent, characterized in that the rice stalks are pulverized and pretreated first, and then the pretreated stalks and modifiers are subjected to amino modification reactions at high temperatures, cleaned and dried Do it and get it. 2. the preparation method of the modified rice straw adsorbent of claim 1, is characterized in that, comprises the steps: (1) Pretreatment of rice stalks: first remove impurities from the rice stalks, wash and dry them, then crush or grind them, and sieve them; (2) Modification of rice straw: Weigh the treated rice straw in step (1), add modifiers for high-temperature modification, the order of adding modifiers is: first add epichlorohydrin and dimethyl formaldehyde For amides, stir at 90-100°C for 1-2h to make it fully react; then add diethylenetriamine, keep warm and continue stirring for 1-2h; finally, add triethylamine, stir for 2-3h at the same temperature; The resulting material is separated by filtration and rinsed with water; (3) Dry the material rinsed in step (2) to get ready. 3. The preparation method of the modified rice straw adsorbent according to claim 2, characterized in that, in the step (1), after the rice straw is rinsed with distilled water, it is placed in an oven at 80-100°C and baked for 20 -24h, the dried straw is crushed, ground and passed through a 40-200 mesh sieve. 4. The method for preparing the modified rice straw adsorbent according to claim 2, characterized in that, in the step (2), 31-36 mL of the modifier is added every time 9-10 g of the rice straw is weighed , wherein the volume ratio of epichlorohydrin to dimethylamide, diethylenetriamine and triethylamine is 3~3.6:2.5~3:1~1.2:2.5~3; the washing water is deionized water or distilled water. 5 . The method for preparing the modified rice straw adsorbent according to claim 2 , wherein a magnetic stirrer is used for stirring in the step (2). 5 . 6 . The method for preparing the modified rice straw adsorbent according to claim 2 , characterized in that, in the step (3), the drying temperature is 80-100° C., and the drying time is 20-24 hours. 7. The application of the modified rice straw adsorbent as claimed in claim 1 in the adsorption of heavy metals in waste water.