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CN-117839634-B - Modified tea stalk hydrothermal carbon, preparation method and application thereof in removing Cr (VI) in water

CN117839634BCN 117839634 BCN117839634 BCN 117839634BCN-117839634-B

Abstract

The invention discloses modified tea stalk hydrothermal charcoal, a preparation method and application thereof in removing Cr (VI) in water. According to the invention, tea stalk powder, sodium hydroxide and 3-chloro-2-hydroxypropyl trimethyl ammonium chloride aqueous solution are uniformly stirred in the aqueous solution, then modified tea stalk hydrothermal carbon with the surface rich in active functional groups such as quaternary amine groups, carboxyl groups and hydroxyl groups is prepared by a one-step hydrothermal amination method with a simple process, and the modified tea stalk hydrothermal carbon is used as a Cr (VI) adsorbent in a water body, wherein the adsorption quantity of Cr (VI) in water is 240.85 mg.g ‑1 , and the adsorption balance time is 24 hours. Can be used in the field of Cr (VI) containing wastewater treatment. The preparation method has the characteristics of simple process, abundant raw materials, low cost, large-scale production and the like, and simultaneously opens a new way for recycling the tea stems, thereby realizing the treatment of wastes with the wastes.

Inventors

  • ZHENG DAFENG
  • CHEN JIAYAO
  • YANG DONGJIE

Assignees

  • 华南理工大学

Dates

Publication Date
20260505
Application Date
20240105

Claims (5)

  1. 1. The application of the modified tea stalk hydrothermal carbon as an adsorbent for removing heavy metal pollutants Cr (VI) in water is characterized in that the preparation method of the modified tea stalk hydrothermal carbon comprises the following steps: (1) Dissolving tea stalk powder in water, and adding alkali and quaternary amination modifier to obtain a uniformly mixed solution; (2) Carrying out hydrothermal carbonization reaction on the uniformly mixed solution, and obtaining the modified tea stalk hydrothermal carbon after cooling, suction filtration, washing, drying and sieving; the quaternary amination modifier in the step (1) is 3-chloro-2-hydroxypropyl trimethyl ammonium chloride aqueous solution, the mass fraction of the 3-chloro-2-hydroxypropyl trimethyl ammonium chloride aqueous solution is 60%, and the alkali in the step (1) is sodium hydroxide; The mass ratio of the tea stalk powder to the alkali in the step (1) is 1:0.2, and the mass ratio of the tea stalk powder to the quaternization modifier is 1:2.5; The temperature of the hydrothermal carbonization reaction in the step (2) is 220 ℃ and the time is 4 hours.
  2. 2. The use according to claim 1, wherein the ratio of tea stalk powder to water in step (1) is 1g:9g.
  3. 3. The use according to claim 1, wherein the tea stalk powder in step (1) has a mesh size of 60-100 mesh.
  4. 4. The application of the method according to claim 1, wherein the suction filtration in the step (2) is vacuum suction filtration, water and absolute ethyl alcohol are sequentially and alternately washed for 3-4 times in the suction filtration process, the drying is carried out at 80+/-10 ℃ for 24+/-8 hours, and the sieving is carried out by a sieve of 80-100 meshes.
  5. 5. A method for removing Cr (VI) in water, which is characterized by comprising the following steps: Adding the modified tea stalk hydrothermal charcoal into water containing Cr (VI) with the concentration of 1-100 mg.L -1 according to the concentration of 0.4-0.8g.L -1 , regulating the pH value of the solution to 2+/-1, the temperature to 303-323K, and filtering out the adsorbent after 24-48 h of adsorption; The preparation method of the modified tea stalk hydrothermal charcoal comprises the following steps: (1) Dissolving tea stalk powder in water, and adding alkali and quaternary amination modifier to obtain a uniformly mixed solution; (2) Carrying out hydrothermal carbonization reaction on the uniformly mixed solution, and obtaining the modified tea stalk hydrothermal carbon after cooling, suction filtration, washing, drying and sieving; the quaternary amination modifier in the step (1) is 3-chloro-2-hydroxypropyl trimethyl ammonium chloride aqueous solution, the mass fraction of the 3-chloro-2-hydroxypropyl trimethyl ammonium chloride aqueous solution is 60%, and the alkali in the step (1) is sodium hydroxide; The mass ratio of the tea stalk powder to the alkali in the step (1) is 1:0.2, and the mass ratio of the tea stalk powder to the quaternization modifier is 1:2.5; The temperature of the hydrothermal carbonization reaction in the step (2) is 220 ℃ and the time is 4 hours.

Description

Modified tea stalk hydrothermal carbon, preparation method and application thereof in removing Cr (VI) in water Technical Field The invention relates to the technical field of recycling solid wastes and removing heavy metals thereof, in particular to modified tea stalk hydrothermal carbon, preparation and application thereof in removing Cr (VI) in water. Background With the rapid development of industrialization, industrial activities and production scales of electroplating, metallurgy, dye printing and the like are increased, and as heavy metal chromium (Cr) is widely applied in the industries to generate a large amount of chromium-containing wastewater, the random discharge of the chromium-containing wastewater has become an environmental problem of increasing attention worldwide. Chromium exists mainly in the form of Cr (VI) and Cr (III) in water. Cr (VI) can induce canceration and mutation, and can cause acute and chronic toxic effects after being ingested by human body, thereby causing symptoms such as vomit, nausea, diarrhea and the like, and causing damage to internal organs, particularly liver and kidney. Therefore, the concentration of Cr (VI) must be reduced to below 0.05mg/L recommended by the world health organization before the wastewater is discharged so as not to cause serious harm to human health and ecological environment. There are a number of different techniques currently being applied to Cr (VI) removal from wastewater, including chemical precipitation, ion exchange, membrane separation and adsorption. The adsorption method is convenient to operate, low in energy consumption and capable of being recycled to be applied on a large scale, but the traditional adsorbent is mainly coal-based activated carbon, and the traditional adsorbent is confronted with the problems of insufficient adsorption capacity and shortage of raw materials, so that development of a novel adsorbent with high performance, sustainability, environmental friendliness and economy is urgently needed. The hydrothermal carbon is a solid product obtained by taking biomass precursors such as low-cost agricultural and forestry waste, animal waste and the like as raw materials and carrying out hydrothermal carbonization at 150-350 ℃. The hydrothermal carbon has the characteristics of low cost, low energy consumption and environmental friendliness, and the surface of the hydrothermal carbon is rich in oxygen-containing functional groups, but the application of the hydrothermal carbon in the adsorption field is limited due to the lack of binding sites with anionic pollutants on the surface of the hydrothermal carbon. In order to improve the adsorption performance of the hydrothermal carbon, functional groups such as hydroxyl groups, carboxyl groups and the like which are rich on the surface of the hydrothermal carbon are used as reaction sites for further functional modification. Research shows that the adsorption capacity of the hydrothermal carbon on heavy metals can be remarkably improved by grafting functional groups such as amino, carboxyl and the like on the surface of the hydrothermal carbon. However, the currently widely used functionalization modification methods such as post-grafting method and chemical oxidation method have the defects of complicated treatment process, difficult purification, high cost and the like. Further searching for a proper modifier is needed, the modification process is simplified, and the high-efficiency and low-cost functional hydrothermal carbon is prepared. The largest tea industry in the world is owned by China, the tea yield in 2022 China reaches 335 ten thousand tons according to the data of the national statistical bureau, and the tea stalks are the most main waste in the tea production and account for 20% of the total yield of the tea. The tea stalk is composed of cellulose, hemicellulose, lignin, polyphenol compounds, moisture and the like, has a certain pore structure, and is hopeful to be developed into a novel adsorbent. At present, the utilization rate of tea stems is low, most of the tea stems are treated in modes of incineration, burial and the like, and serious problems of resource waste and environmental pollution are caused. Disclosure of Invention In order to solve the defects and shortcomings of the prior art, the invention aims to provide modified tea stalk hydrothermal carbon, a preparation method and application thereof in removing Cr (VI) in water. According to the invention, through a one-step hydrothermal method with a simple process, quaternary amine roots are successfully grafted on the surface of the hydrothermal carbon, in addition, the number of active sites such as carboxyl, hydroxyl and the like on the surface of the hydrothermal carbon is increased, the Cr (VI) removal capability of the hydrothermal carbon in a water body is obviously improved, and the problems of complex process, high cost, low tea stalk recycling utilization rate and the like of the existing