CN103464119B - Preparation and application of a cysteine modified palm bark adsorbent - Google Patents

Abstract

The invention discloses a preparation method and application technology of a cysteine-modified palm bark adsorbent, which is characterized in that: the palm bark is soaked in water in a container, dried and pulverized, treated with isopropanol and NaOH solution, Soak in a mixed solution of epichlorohydrin and NaOH, boil, filter with suction, and dry to obtain epoxy palm bark. In the reactor, add according to the following composition mass percentages, cysteine: 3~11%, epoxy palm bark: 9~26%, sodium carbonate: 4~12%; Water: 52~82%, each The sum of the components is 100%, react at a constant temperature of 50±3°C, stir, and reflux for 4~8 hours. After cooling, wash with deionized water and filter with suction until the filtrate is neutral. After washing with a small amount of ethanol, put it in Dry in a vacuum oven at 40±5°C to obtain cysteine-modified palm bark. The adsorbent has high adsorption efficiency for heavy metal ions, high speed, good desorption performance, mechanical properties, strong regeneration ability, low cost and environmental protection.

Description

Preparation and application of a cysteine modified palm bark adsorbent

technical field

The invention relates to a preparation method of a biosorbent and the technical field of heavy metal adsorption application, in particular to a preparation method of a cysteine-modified palm bark adsorbent and an application technology for heavy metal ion adsorption.

Background technique

Heavy metals, especially mercury, cadmium, lead, chromium, etc. have significant toxicity. They cannot be degraded by microorganisms in water, but can only undergo various forms of mutual transformation, dispersion, and enrichment. Heavy metals are highly toxic and carcinogenic to living organisms, and will be enriched and accumulated in organisms to produce high toxicity, and will also have amplifying effects through the food chain. Because the toxicity produced by heavy metals cannot be biodegraded, heavy metal ions in water and soil environments have attracted increasing attention. To remove heavy metals, chemical precipitation, flocculation, ion exchange, and electrolysis are usually used, but these methods have disadvantages such as high cost and low efficiency. In recent years, various adsorbents have been modified and synthesized by using natural polymer fibers (such as cotton, hemp, palm bark, loofah, bagasse, peanut shells, etc.), which are cheap, easy to obtain, renewable, Biodegradable and other advantages.

Palm tree is a perennial evergreen tree plant, up to 7 meters high; the trunk is erect, unbranched, and covered by a brown coat formed by leaf sheaths; therefore, the fibers of the palm bark are very long and strong, and are usually used to make mattresses , is one of the most precious ecological resources and a renewable resource. At present, palm trees are widely planted in the area south of the Yangtze River and are very precious long-fiber raw materials. This kind of natural polymer material has the characteristics of natural, green, biodegradable, high mechanical strength and strong corrosion resistance. Palm bark can be regenerated and reused many times as an adsorbent, and has a large adsorption capacity for dyes. There are very few foreign reports on the chemical modification and adsorption properties of palm bark. The Chinese patent application number is: 201310147720.6, which discloses a preparation method and application of mercapto palm bark adsorbent, which is characterized in that: In the reactor, add according to the following composition mass percentage, thioglycolic acid: 30~45%, tetrahydrofuran: 25~40%, alkalized palm bark: 20~35%, glacial acetic acid: 0.5~2.5%, concentrated sulfuric acid: 0.15~0.3%, the sum of each component is 100%, plugged, at 40~45°C, static reaction for 48~60 h, then washed with deionized water, suction filtered, until the filtrate is neutral, washed with a small amount of ethanol Finally, it is dried in an oven at 35-45°C to obtain the mercapto palm bark adsorbent. The adsorption capacity of its mercapto palm bark adsorbent for Cd ²⁺ can be as high as 286mg/g, the maximum adsorption capacity for Pb ²⁺ is 521mg/g, the maximum adsorption capacity for Cu ²⁺ is 165mg/g, and the highest adsorption rate can be Up to 98%.

Cysteine is a common amino acid, which has effective detoxification and anti-aging effects, so there is no problem of polluting the environment. In addition, the sulfhydryl group and carboxyl group on the side chain of cysteine can combine with heavy metals There are also reports on the preparation of adsorbents by modifying cysteine. Li Qing et al. studied the adsorption of Hg ²⁺ on cysteine-modified mesoporous materials, (Li Qing et al., Cysteine-modified mesoporous materials Research on the performance of highly selective separation and enrichment of Hg ²⁺ , Analytical Chemistry, 2013, 41 (1): 93~97); Yang Yaling et al. studied the adsorption performance of cysteine-modified bagasse on Cd ²⁺ . The maximum adsorption capacity for Cd ²⁺ is: 122.75 mg/g, (Yang Yaling et al., Adsorption of Epichlorohydrin and Cysteine Modified Bagasse to Cd ²⁺ , Yunnan Chemical Industry, 2010, 34(1), 11 ~14). The adsorbent is prepared by modifying palm bark with cysteine, which not only has the property of strong chelation between sulfhydryl groups and some heavy metal ions, but also has the advantages of renewable, degradable, environmentally friendly, and cheap natural polymers. , is an important biological resource. The use of cysteine to modify palm bark to prepare adsorbents has not been reported.

Contents of the invention

One of the purposes of the present invention is to provide a method for preparing cysteine-modified palm bark adsorbent, which mainly makes the obtained cysteine-modified palm bark adsorbent have a larger adsorption capacity as heavy metal adsorbent in water , By adjusting the difference in pH value, heavy metal ions can be separated.

The purpose of the present invention is achieved through the following technical solutions.

A preparation method of cysteine modified palm bark adsorbent, characterized in that the method has the following processing steps:

(1) Palm bark pretreatment: Cut the palm bark into small pieces, wash with water to remove soil and impurities, soak in water for 24 to 48 hours in a container, and then crush it after vacuum drying. The solid-to-liquid ratio is 50~100g/L, use a mixed solution of isopropanol and 1.0~3.5mol/L NaOH solution with a volume ratio of 1:4~10, soak at room temperature for 12~20h, boil for 10~30nm, After cooling, wash with deionized water until neutral, filter with suction, and dry at 50-60°C to obtain pretreated palm bark;

(2) Preparation of epoxy-based palm bark: use the above pretreated palm bark at a solid-to-liquid ratio of 100~200g/L, and use epichlorohydrin and 1.0~3.5mol/L NaOH solution at a volume of 1:3~6 The mixed solution is soaked at room temperature for 12-20 h, then boiled for 10-20 min, washed with deionized water until neutral, then washed with ethanol, filtered and dried at 55-65°C to obtain epoxy palm bark;

(3) Preparation of cysteine-modified palm bark: In the reactor, add according to the following composition mass percentage, cysteine: 3~11%, epoxy-based palm bark: 9~26%, sodium carbonate : 4~12%; water: 52~82%, the sum of each component is 100%, at 50±3℃ constant temperature, stirring, reflux reaction for 4~8 h, after cooling, wash with deionized water, suction filter, until The filtrate is washed with a small amount of ethanol until it is neutral, and then dried in a vacuum oven at 40±5°C to obtain cysteine-modified palm bark, wherein the mass ratio of cysteine to sodium carbonate is 1:1 ~1.5 between.

Another object of the present invention is to provide a cysteine-modified palm bark adsorbent for the adsorption of heavy metal ions in water systems, such as Cd ²⁺ , Pb ²⁺ , Hg ²⁺ , Cu ²⁺ , which is characterized by : Soak the prepared cysteine-modified palm bark adsorbent with deionized water for 2-4 hours, and adsorb according to the static method.

The prepared cyclocysteine-modified palm bark adsorbent was soaked in deionized water for 2-4 hours, and adsorbed according to the dynamic method.

Advantage and effect of the present invention are:

(1) The cysteine-modified palm bark adsorbent obtained in the present invention has good physical and chemical stability and excellent mechanical strength. Compared with modified peanut shells and bagasse, it has a large adsorption capacity for heavy metals and is wear-resistant , repeated use times, up to more than 10 times;

(2) The cysteine-modified palm bark adsorbent obtained in the present invention can absorb and elute heavy metal ions in water, with high adsorption efficiency, fast speed, good desorption performance, and can be used in a wide acid-base range ;

(3) Good stability, is a natural green product, biodegradable;

(4) The conditions required for the synthesis process are easy to control, the energy consumption is low, the operation is simple, and there is no "three wastes" discharge in the whole production process, which belongs to the clean production process and is easy for industrial production.

Detailed ways

Example 1

(1) Palm bark pretreatment: Cut the palm bark into small pieces, wash with water to remove soil and impurities, soak in water for 24 hours in a container, and then crush it after vacuum drying. Mix 10g of dried and crushed palm bark with 40mL A mixed solution of isopropanol and 160mL 1.0mol/L NaOH, soaked at room temperature for 15h, boiled for 20nm, washed with deionized water until neutral after cooling, filtered with suction, and dried at 55°C to obtain pretreated palm bark;

(2) Preparation of epoxy-based palm bark: 10g of the above-mentioned pretreated palm bark was soaked in a mixed solution of 20mL epichlorohydrin and 100mL3.0mol/L NaOH at room temperature for 12 hours, then boiled for 15min, and used after cooling. Wash with deionized water until neutral, then wash with ethanol, and dry at 55°C after suction filtration to obtain epoxy-based palm bark;

(3) Preparation of cysteine-modified palm bark: In the reactor, add cysteine: 4g, epoxy-based palm bark: 10g, sodium carbonate: 5g; water: 81mL, each component The sum is 100%, react at a constant temperature of 50±3°C, stir, and reflux for 5 hours. After cooling, wash with deionized water and filter with suction until the filtrate is neutral. After washing with a small amount of ethanol, place it at 40±5°C Dry in a vacuum oven to obtain the cysteine-modified palm bark.

Example 2

(1) Palm bark pretreatment: Cut the palm bark into small pieces, wash with water to remove soil and impurities, soak in water for 40 hours in a container, dry in a vacuum and then crush it. Take 20g of the dried and crushed palm bark in 50mL A mixed solution of isopropanol and 300mL 2.0mol/L NaOH, soaked at room temperature for 12h, boiled for 30nm, washed with deionized water until neutral after cooling, filtered with suction, and dried at 50°C to obtain pretreated palm bark;

(2) Preparation of epoxy-based palm bark: 20g of the above-mentioned pretreated palm bark was soaked in a mixed solution of 30mL epichlorohydrin and 180mL2.0mol/L NaOH at room temperature for 20 hours, then boiled for 10min, and then used after cooling. Wash with deionized water until neutral, then wash with ethanol, and dry at 60°C after suction filtration to obtain epoxy palm bark;

(3) Preparation of cysteine-modified palm bark: In the reactor, add cysteine: 4g, epoxy-based palm bark: 10g, sodium carbonate: 5g; water: 81mL, each component The sum is 100%. React at a constant temperature of 50±3°C, stir, and reflux for 6 hours. After cooling, wash with deionized water and filter with suction until the filtrate is neutral. After washing with a small amount of ethanol, place it in a vacuum at 40±5°C. drying in a drying oven to obtain cysteine-modified palm bark.

Example 3

(1) Palm bark pretreatment: Cut the palm bark into small pieces, wash with water to remove soil and impurities, soak in water for 32 hours in a container, dry in a vacuum and then crush it. Take 30g of the dried and crushed palm bark in 50mL A mixed solution of isopropanol and 250mL 3.0mol/L NaOH, soaked at room temperature for 20h, boiled for 10nm, washed with deionized water until neutral after cooling, filtered with suction, and dried at 60°C to obtain pretreated palm bark;

(2) Preparation of epoxy-based palm bark: 20g of the above-mentioned pretreated palm bark was soaked in a mixed solution of 50mL epichlorohydrin and 150mL3.5mol/L NaOH at room temperature for 15 hours, then boiled for 20min, and used after cooling. Wash with deionized water until neutral, then wash with ethanol, and dry at 55°C after suction filtration to obtain epoxy-based palm bark;

(3) Preparation of cysteine-modified palm bark: In the reactor, add cysteine: 6g, epoxy-based palm bark: 12g, sodium carbonate: 6.5g; water: 31mL, each group The sum of the fractions is 100%, react at a constant temperature of 50±3°C, stir, and reflux for 8 hours. After cooling, wash with deionized water and filter with suction until the filtrate is neutral. After washing with a small amount of ethanol, place it at 40±5 °C in a vacuum drying oven to obtain cysteine-modified palm bark.

Example 4

(1) Palm bark pretreatment: Cut the palm bark into small pieces, wash with water to remove soil and impurities, soak in water for 24 hours in a container, and then crush it after vacuum drying. Mix 10g of dried and crushed palm bark with 40mL A mixed solution of isopropanol and 160mL 1.0mol/L NaOH, soaked at room temperature for 15h, boiled for 20nm, washed with deionized water until neutral after cooling, filtered with suction, and dried at 55°C to obtain pretreated palm bark;

(2) Preparation of epoxy-based palm bark: 10g of the above-mentioned pretreated palm bark was soaked in a mixed solution of 20mL epichlorohydrin and 100mL3.0mol/L NaOH at room temperature for 12 hours, then boiled for 15min, and used after cooling. Wash with deionized water until neutral, then wash with ethanol, and dry at 55°C after suction filtration to obtain epoxy-based palm bark;

(3) Preparation of cysteine-modified palm bark: In the reactor, add cysteine: 4g, epoxy-based palm bark: 6g, sodium carbonate: 5g; water: 35mL, each component The sum is 100%, react at a constant temperature of 50±3°C, stir, and reflux for 5 hours. After cooling, wash with deionized water and filter with suction until the filtrate is neutral. After washing with a small amount of ethanol, place it at 40±5°C Dry in a vacuum oven to obtain the cysteine-modified palm bark.

Example 5

(1) Palm bark pretreatment: Cut the palm bark into small pieces, wash with water to remove soil and impurities, soak in water for 40 hours in a container, dry in a vacuum and then crush it. Take 20g of the dried and crushed palm bark in 50mL A mixed solution of isopropanol and 300mL 2.0mol/L NaOH, soaked at room temperature for 12h, boiled for 30nm, washed with deionized water until neutral after cooling, filtered with suction, and dried at 50°C to obtain pretreated palm bark;

(2) Preparation of epoxy-based palm bark: 20g of the above-mentioned pretreated palm bark was soaked in a mixed solution of 30mL epichlorohydrin and 180mL2.0mol/L NaOH at room temperature for 20 hours, then boiled for 10min, and then used after cooling. Wash with deionized water until neutral, then wash with ethanol, and dry at 60°C after suction filtration to obtain epoxy palm bark;

(3) Preparation of cysteine-modified palm bark: In the reactor, add cysteine: 5g, epoxy-based palm bark: 10g, sodium carbonate: 5g; water: 30mL, each component The sum is 100%. React at a constant temperature of 50±3°C, stir, and reflux for 6 hours. After cooling, wash with deionized water and filter with suction until the filtrate is neutral. After washing with a small amount of ethanol, place it in a vacuum at 40±5°C. drying in a drying oven to obtain cysteine-modified palm bark.

Example 6

(1) Palm bark pretreatment: Cut the palm bark into small pieces, wash with water to remove soil and impurities, soak in water for 32 hours in a container, dry in a vacuum and then crush it. Take 30g of the dried and crushed palm bark in 50mL A mixed solution of isopropanol and 250mL 3.0mol/L NaOH, soaked at room temperature for 20h, boiled for 10nm, washed with deionized water until neutral after cooling, filtered with suction, and dried at 60°C to obtain pretreated palm bark;

(2) Preparation of epoxy-based palm bark: 20g of the above-mentioned pretreated palm bark was soaked in a mixed solution of 50mL epichlorohydrin and 150mL3.5mol/L NaOH at room temperature for 15 hours, then boiled for 20min, and used after cooling. Wash with deionized water until neutral, then wash with ethanol, and dry at 55°C after suction filtration to obtain epoxy-based palm bark;

(3) Preparation of cysteine-modified palm bark: In the reactor, add cysteine: 3g, epoxy-based palm bark: 18g, sodium carbonate: 4g; water: 75mL, each component The sum is 100%, react at a constant temperature of 50±3°C, stir, and reflux for 7 hours. After cooling, wash with deionized water and filter with suction until the filtrate is neutral. After washing with a small amount of ethanol, place it in a vacuum at 40±5°C. drying in a drying oven to obtain cysteine-modified palm bark.

Example 7

The cysteine-modified palm bark prepared in the above examples has the same sulfhydryl content as detected by chemical methods.

Application method of cysteine-modified palm bark: Soak the prepared cysteine-modified palm bark in deionized water for 2 h, one is static adsorption method, the other is dynamic adsorption method, for Metal ion adsorption for application.

The adsorption performance was measured by static adsorption method. 20 mL of metal ion solutions with different concentrations were taken, and an equal amount of cysteine-modified palm bark was added under the same conditions. The concentration of metal ions is calculated according to the concentration change of metal ion solution before and after adsorption.

The adsorption performance was determined by a dynamic method. A certain amount of cysteine-modified palm bark was loaded into the adsorption column by a wet method, and metal ion solutions with different concentrations were taken, and the pH value was adjusted with dilute acid and dilute alkali. The flow rate of min passes through the adsorption column, and the amount of metal ions adsorbed on the filtrate and the column is measured by atomic absorption, thereby calculating the adsorption rate.

The application of cysteine-modified palm bark in the adsorption of metal ions prepared by the above method. The application of the cysteine-modified palm bark of the present invention in the field of metal ion adsorption is to directly adsorb and elute various metal ions in water bodies. The method is:

(1) For those containing K ⁺ , Na ⁺ , Ca ²⁺ , Mg ²⁺ , Ba ²⁺ , Al ³⁺ , Cu ²⁺ , Zn ²⁺ , Cd ²⁺ , Fe ³⁺ , Ag ⁺ , Co ²⁺ , One or more of Ni ²⁺ , Pb ²⁺ , Se ⁴⁺ , Pt ⁴⁺ , Pd ²⁺ , Au ³⁺ in the water system to be treated, using cysteine modified palm bark with static adsorption Methods Water treatment was carried out, that is, palm bark modified by cysteine was immersed in the water system to be treated, and oscillated and adsorbed for 0.5 h. The adsorption rules were as follows:

a. For alkali metals and alkaline earth metals such as K ⁺ , Na ⁺ , Ca ²⁺ , Mg ²⁺ , Ba ²⁺ , Al ^{3+ ,} etc., it does not adsorb, so the presence of alkali metals and alkaline earth metals in the sample does not affect cysteine Adsorption properties of acid-modified palm bark.

b. It has strong adsorption performance for noble metal ions, and the order of adsorption strength is: Pt ⁴⁺ > Au ³⁺ > Pd ²⁺ > Ag ⁺ .

c. It also has strong adsorption performance for heavy metal ions, and the order of adsorption strength is: Se ⁴⁺ , Ag ⁺ > Cu ²⁺ > Fe ³⁺ , Pb ²⁺ > Zn ²⁺ > Cd ²⁺ > Co ²⁺ , Ni ²⁺ .

The adsorption capacity is related to factors such as the content of sulfhydryl groups in cysteine-modified palm bark, the adsorption temperature, and the pH value of the solution system.

(2) For those containing K ⁺ , Na ⁺ , Ca ²⁺ , Mg ²⁺ , Ba ²⁺ , Al ³⁺ , Cu ²⁺ , Zn ²⁺ , Cd ²⁺ , Fe ³⁺ , Ag ⁺ , Co ²⁺ , One or more of Ni ²⁺ , Pb ²⁺ , Se ⁴⁺ , Pt ⁴⁺ , Pd ²⁺ , Au ³⁺ in the water system to be treated, using cysteine modified palm bark with dynamic adsorption Methods Water treatment, the adsorption rule is the same as above, and the adsorption capacity is related to factors such as the content of sulfhydryl groups in cysteine-modified palm bark, adsorption temperature, pH value of the solution system, and flow rate of the solution.

The obtained cysteine-modified palm bark has an adsorption capacity of up to 295 mg/g for Cd ²⁺ , a maximum adsorption capacity for Pb ²⁺ of 533 mg/g, and a maximum adsorption capacity for Cu ²⁺ of 179 mg/g. The maximum adsorption capacity of Hg ²⁺ is 492mg/g, and the highest adsorption rate can reach 99%.

Claims (3)

1. a preparation method of cysteine modified palm bark adsorbent, characterized in that, the method has the following processing steps: (1) palm bark pretreatment: cut the palm bark into small pieces, wash with water to remove soil and impurities, put into a container and soak in water for 24 to 48 hours, and pulverize after vacuum drying, dry and pulverize the palm bark with The solid-to-liquid ratio is 50-100g/L, use a mixed solution of isopropanol and 1.0-3.5mol/L NaOH solution with a volume ratio of 1:4-10, soak at room temperature for 12-20h, boil for 10-30nm, After cooling, wash with deionized water until neutral, filter with suction, and dry at 50-60°C to obtain pretreated palm bark; (2) Preparation of epoxy-based palm bark: use the above pretreated palm bark at a solid-to-liquid ratio of 100-200 g/L, and use epichlorohydrin and 1.0-3.5 mol/L NaOH solution at a volume of 1:3-6 The mixed solution is soaked at room temperature for 12-20 hours, then boiled for 10-20 minutes, cooled, washed with deionized water until neutral, then washed with ethanol, and dried at 55-65°C after suction filtration to obtain epoxy palm trees Skin; (3) Preparation of cysteine-modified palm bark: in the reactor, add according to the following composition mass percentage, cysteine: 3～11%, epoxy-based palm bark: 9～26%, sodium carbonate : 4~12%; water: 52~82%, the sum of each component is 100%, at 50±3°C constant temperature, stirring, reflux reaction for 4~8h, after cooling, wash with deionized water, suction filter, to the filtrate Until it becomes neutral, it is washed with a small amount of ethanol and dried in a vacuum oven at 40±5°C to obtain cysteine-modified palm bark. 2. according to a kind of cysteine modified palm bark adsorbent preparation method described in claim 1, it is characterized in that, the cysteine described in step (3) is L-cysteine or D-cysteine. 3. according to the preparation method of a kind of cysteine-modified palm bark adsorbent described in claim 1, it is characterized in that, cysteine-modified palm bark adsorbent is to water Cd ²⁺ , Pb ²⁺ , Hg ²⁺ , Cu ²⁺ adsorption applications.