CN110065988B

CN110065988B - Application of composite hydrogel in heavy metal ion removal

Info

Publication number: CN110065988B
Application number: CN201910328332.5A
Authority: CN
Inventors: 曹美文; 位强; 沈阳; 闫云鹏; 王生杰; 夏永清
Original assignee: China University of Petroleum East China
Current assignee: China University of Petroleum East China
Priority date: 2019-04-23
Filing date: 2019-04-23
Publication date: 2022-03-01
Anticipated expiration: 2039-04-23
Also published as: CN110065988A

Abstract

The invention discloses an application of a Graphene Oxide (GO)/poly N-isopropylacrylamide (PNIPANM) composite reversible sol-gel system in heavy metal ion removal, and belongs to the technical field of environmental protection. Adding GO/PNIPAM compound aqueous solution into sewage with excessive heavy metal ions, and heating the system to above 35 ℃ to form composite hydrogel. By cooling to below 32 ℃, the hydrogel will drain a large amount of water within 5 minutes, phase separating to form an aqueous phase and a highly condensed gel phase. Meanwhile, the GO sheet layer adsorbed with a large amount of heavy metal ions is fixed in the highly condensed gel phase, the water phase and the highly condensed gel phase can be separated through simple two-phase separation, and the heavy metal ions in the sewage can be removed in a 'class extraction' mode.

Description

Application of composite hydrogel in heavy metal ion removal

Technical Field

The invention relates to application of Graphene Oxide (GO)/poly N-isopropylacrylamide (PNIPANM) compounded temperature-responsive hydrogel in heavy metal ion removal, and belongs to the technical field of environmental protection.

Background

With the development of industry and the increase of activities of human beings, a large amount of industrial wastewater and municipal domestic sewage containing heavy metal pollutants are discharged into rivers and lakes. Therefore, the national government makes regulations on factories which need to discharge pollutants such as heavy metal ions, and clearly requires that each heavy metal ion in the discharged sewage cannot exceed a certain concentration. At present, most of factories treat discharged sewage in a way that a large amount of alkali is added to make heavy metal ions form hydroxides to precipitate. Although simple, the method requires a long processing period and often requires a large amount of manpower, material resources and financial resources. Although a small number of factories adopt an ion exchange method or an electrochemical method for treating heavy metal ions, the plants also have the problems of waste liquid generation, poor long-period adaptability and high cost.

At present, one of the methods for treating heavy metal ions with a better application prospect is an adsorption method, which has many advantages for treating heavy metal wastewater, many adsorbents have been developed, but the adsorption effect is very good and can reach the national sewage discharge standard or less, so many adsorption materials with good adsorption performance are to be discovered, and the ion adsorption method becomes a hot spot of research in recent years. The invention mainly provides a novel reversible sol-gel system, and a specific preparation and application method for removing heavy metal ions in water through adsorption and phase separation of the heavy metal ions.

Disclosure of Invention

The invention provides a GO/PNIPAM composite system which has temperature-responsive 'sol-gel' reversible transformation and can adsorb heavy metal ions in water with high efficiency and carry out separation and removal by a phase separation method. In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

the application of the GO/PNIPAM composite hydrogel in heavy metal ion removal provided by the invention comprises the following steps:

(1) fully dissolving 0.1-0.5mg of GO and 10.0-40.0mg of solid PNIPAM powder (the ratio is between 1: 20 and 1: 400) in 1.0mL of pure water to obtain GO/PNIPAM suspension;

(2) adding the GO/PNIPAM suspension into wastewater containing heavy metal ions, uniformly mixing (the proportion is ensured to be between 1: 1 and 1: 5), and heating to the temperature of more than 35 ℃ to form solid-phase hydrogel;

(3) cooling the GO/PNIPAM hydrogel system formed by heating to below 32 ℃, wherein the system can generate phase separation to form solid-phase hydrogel and liquid-phase solution;

(4) and (4) carrying out 'quasi-extraction' mode separation on the product in the step (3), and separating solid-phase hydrogel from liquid-phase solution, wherein the liquid-phase solution is the wastewater from which the heavy metal ions are removed.

Preferably, the step (1), the dissolving sufficiently in water is to subject the mixture of PNIPAM powder and water to ultrasonic wave to accelerate dissolving.

Preferably, in the step (1), the content of the GO/PNIPAM suspension is 0.1mg/mL and 40mg/mL respectively.

Preferably, in the step (2), the mixed wastewater is reacted at a temperature of more than 35 ℃ for at least 10 min.

Preferably, in step (4), the filtration separation step should be carried out while hot (25-31 ℃).

Drawings

FIG. 1 is the adsorption of copper onto hydrogel of 0.5mg/ml GO +40mg/ml PNIPAM at different reaction temperatures;

FIG. 2 is the relationship of the adsorption efficiency of 0.5mg/ml GO +40mg/ml PNIPAM versus pH;

FIG. 3 is an electron micrograph of 0.1mg/ml GO dissolved in water (scale bar 5 μm);

FIG. 4 shows the gradual transition from liquid to solid state of poly-N-isopropylacrylamide hydrogel.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

(1) Preparing 25.0mg/mL copper standard solution;

(2) fully dissolving GO solution and solid PNIPAM powder (the mass ratio of GO to PNIPAM is 1: 400) in water to obtain GO/PNIPAM suspension, and adjusting the pH of the suspension to about 6.0;

(3) and (3) fully mixing the 25.0mg/mL copper standard solution and the GO/PNIPAM suspension in the steps (1) and (2), and heating the system to over 35 ℃ to form the composite hydrogel. The hydrogel can be separated into a water phase and a highly condensed gel phase within 5 minutes by cooling to 25-31 ℃;

(4) carrying out phase separation on the product obtained in the step (3) at 25-31 ℃, and removing solid-phase gel to obtain a liquid-phase solution;

(5) adding 1mL of the liquid phase solution separated in the step (4) into a separating funnel, adding 49.0mL of pure water into the separating funnel for dilution, then adding 5mL of Ethylene Diamine Tetraacetic Acid (EDTA) -ammonium citrate solution and 2 drops of cresol red indicator solution, and adjusting the pH value to 8-8.5 (changing the red color into light purple color through yellow color) by using ammonium chloride-ammonium hydroxide buffer solution;

(6) 5.0mL of sodium diethyldithiocarbamate solution was added to the separatory funnel, shaken well, and allowed to stand for 5 min. Accurately adding 5.0mL of carbon tetrachloride, oscillating for no less than 2min, standing to layer;

(7) and (4) taking 1.0mL of the carbon tetrachloride layer solution in the liquid separating funnel in the step (6), and putting the solution into a 5mm cuvette. At the wavelength of 440nm, respectively, using carbon tetrachloride as reference, measuring absorbance by using an ultraviolet spectrophotometer, and calculating the concentration of copper ions by a standard curve. Tests show that when the initial copper ion concentration is 25.0mg/mL, the copper ion concentration in water is reduced to 2.1mg/mL after the composite hydrogel is used for adsorption, and the adsorption efficiency is 91.6%.

Example 2

(1) Preparing a 25.0mg/mL lead standard solution;

(2) fully dissolving liquid-phase graphene oxide and solid PNIPAM powder (the ratio is 1: 400) in water to obtain GO/PNIPAM suspension, and adjusting the pH of the suspension to about 6.0;

(3) and (3) fully mixing the 25mg/mL lead standard solution and the GO/PNIPAM suspension in the steps (1) and (2), and heating the system to over 35 ℃ to form the composite hydrogel. The hydrogel can be separated into a water phase and a highly condensed gel phase within 5 minutes by cooling to 25-31 ℃;

(5) and (4) detecting the solution obtained in the step (4) by using atomic absorption spectroscopy. Through detection, when the concentration of lead ions is 25.0mg/mL, the concentration of the lead ions in water is reduced to 1.7mg/mL after the composite hydrogel is used for adsorption, and the adsorption efficiency is 93.2%.

Example 3

(1) Preparing 25.0mg/mL nickel standard solution;

(3) and (3) fully mixing the 25.0mg/mL nickel standard solution and the GO/PNIPAM suspension in the steps (1) and (2), and heating the system to over 35 ℃ to form the composite hydrogel. The hydrogel can be separated into a water phase and a highly condensed gel phase within 5 minutes by cooling to 25-31 ℃;

(5) and (4) detecting the solution obtained in the step (4) by using atomic absorption spectroscopy. Through detection, when the concentration of nickel ions is 25.0mg/mL, the concentration of the nickel ions in water is reduced to 2.8mg/mL after the composite hydrogel is used for adsorption, and the adsorption efficiency is 88.8%.

Claims

1. The application of the composite hydrogel in heavy metal ion removal is characterized in that:

(1) fully dissolving 0.1-0.5mg of graphene oxide and 10.0-40.0mg of poly-N-isopropylacrylamide powder in 1.0mL of pure water to obtain a graphene oxide/poly-N-isopropylacrylamide suspension;

(2) adding the graphene oxide/poly-N-isopropylacrylamide suspension into the wastewater containing heavy metal ions, uniformly mixing, and heating to over 35 ℃ to form solid-phase hydrogel;

(3) cooling the graphene oxide/poly N-isopropylacrylamide hydrogel system formed by heating to 25-31 ℃, wherein the system can be subjected to phase separation to form solid-phase hydrogel and liquid-phase solution;

(4) and (3) carrying out 'similar extraction' mode separation on the solid-phase hydrogel and the liquid-phase solution, and separating the solid-phase hydrogel from the liquid-phase solution, wherein the liquid-phase solution is the wastewater from which the heavy metal ions are removed.

2. The application of the composite hydrogel in heavy metal ion removal according to claim 1, wherein the pH of the wastewater is adjusted to be more than or equal to 6.0.