Graphene Oxide Controls Heavy Metal Pollution: New Materials Solve Old Problems

"The Chinese body is a periodic table of elements!"

Although this exaggeration is not an exaggeration, it vividly expressed the people's concern about heavy metal pollution. In 2005, the Pearl River tributaries Beijiang cadmium pollution, the 2006 Hunan Yueyang arsenic pollution, the 2010 Fujian Zijin Mining major pollution, and the 2012 Guangxi Hechi cadmium pollution... The shocking major water resource pollution incident sounded the alarm for water resources protection. The problem of heavy metal contaminated soil has also raised serious issues for our food production safety, and has also set a higher standard for effective treatment of heavy metal pollution in water resources.

At present, the commonly used materials for the treatment of heavy metals in water resources are activated carbon, zeolites and exchange resins, while the adsorptive capacity of activated carbon and zeolites with lower cost is poor, and the resins with strong adsorption capacity and carbon fibers are expensive. Recently, Science and Technology Daily reporter learned from Lite Nanotechnology Co., Ltd. that the company's “Thousand Talents Program” overseas distinguished expert Dr. Hou Shifeng team developed a new type of graphene oxide material, which effectively solved the contradiction between adsorption capacity and cost.

Adsorption force: more than ten times of activated carbon

Graphene is actually a two-dimensional structure of carbon as a single-layered carbon atomic material peeled from a graphite material. Graphene became famous for a long time: In 2010, the physicists Andrei Heim and Konstantin Novoselov of the University of Manchester in the United Kingdom won the year with the “groundbreaking experiments on two-dimensional graphene materials”. Nobel Prize in physics, graphene is famous for this.

Although graphene has a long way to go, it is not a small thing. It is said that it has the fewest features in the world: the world’s thinnest material is known, and the highest known material is currently the most known conductive material. Excellent material...

In recent years, graphene materials have found a new place for use as a water treatment agent by virtue of their excellent adsorption properties. At the beginning of 2012, Prof. André Heim found that graphene oxide films can block all molecules except water. Lockheed Martin has invested heavily in desalination equipment based on graphene materials. Graphene materials are expected to Cleansing, sewage treatment, and other areas have shown their talents. At present, the United States and other countries have also made great progress in this regard. And Dr. Hou Shifeng’s current research on the status quo and existing problems of heavy metal pollutants in China, independently developed for the treatment of environmental heavy metal graphene oxide materials is also the world's first.

Graphene oxide is a carbon nanomaterial that is prepared from natural graphite and has a structure similar to carbon nanotubes. Hou Shifeng told a reporter from Science and Technology Daily that compared to the adsorption capacity of activated carbon, carbon nanotubes, and graphene materials for low-concentration lead-containing wastewater, the adsorption capacity of graphene oxide for lead is as high as 800 mg/g, which is much higher than that of activated carbon 60 to 120 mg/g. At the same time, graphene oxide has a very strong regeneration capability, and the adsorption capacity after repeated adsorption/elution cycles only decreases by 5 to 10%.

Why does Graphene Oxide have such a strong adsorption capacity for heavy metals? There are two reasons: one is that graphene oxide is a two-dimensional nanostructured material with monolayer thickness, its theoretical surface area can reach 2600 m 2 /g, and it is the largest among all carbon nanomaterials; the second is graphene oxide. In the preparation process, a large number of active groups such as carboxyl group, carbonyl group, hydroxyl group, epoxy group and the like are formed on the surface thereof. Therefore, graphene oxide has the most basic elements required for an excellent adsorbent: a sufficiently large specific surface area and a sufficiently high surface functional group density.

Hou Shifeng introduced that the utilization of graphene oxide materials can reduce the lead-containing wastewater discharge concentration in the lead-acid battery industry from 100-1000 ppb to 1-10 ppb and the lead recovery rate to 95%-99%. Technology is reduced by 90%. The reporter learned that the results can be effectively extended to other heavy metal pollution systems such as cadmium, nickel, arsenic, copper, chromium, and radioactive elements, and have considerable economic and social benefits.

Plasticity: performance can be "customized"

Hou Shifeng told reporters that the adsorption mechanism of toxic heavy metals in graphene oxide nanomaterials, the interaction mechanism between heavy metal and graphene oxide functional groups, the effect of the surface structure of graphene oxide on the adsorption capacity, adsorption kinetics, and mechanism The adsorption and desorption characteristics of graphene oxide are designed in several directions to effectively "customize" the adsorption characteristics of graphene oxide.

As an example of the more mature graphene oxide functionalization technology currently used by Aluminium Nanomaterials Technology Co., Ltd., functional groups can be introduced into the surface of graphene oxide through functionalization reactions. These groups are bonded to resins, activated carbon, and carbon nanotubes. Carbon and nano-materials exhibit excellent adsorption characteristics for heavy metals and significantly improve their ability to remove heavy metal ions such as lead, nickel, and copper.

Through the introduction of the surface-specific group of graphene oxide and the design of the surface molecular level, the adsorption characteristics of the graphene oxide material will be further upgraded, which can effectively cope with specific problems in the treatment of water pollution incidents. The reporter learned that the “advanced” graphene oxide material greatly enhances the rapid adsorption of metal ions (adsorption saturation can be completed within 20 minutes), effectively solving the rapid processing problems required for heavy metal pollution incidents. Moreover, these adsorbent materials can be reused after elution of heavy metals, and their overall economic costs can be lower than conventional precipitation methods and conventional carbon-based adsorbent materials, solving the problem of high operating costs. More importantly, the adsorbed heavy metals can be completely recovered after 100% elution, thus thoroughly solving the secondary pollution problem after the heavy metal leakage treatment.

Maybe you think that new materials with such powerful features are certainly expensive, but they are not. Hou Shifeng told reporters that this is where people have always been skeptical. In fact, although high-quality graphene is expensive, Litano's functionalized graphene oxide has the same production cost as chelating resin, but its adsorption capacity is 2 to 5 times higher. As a result, the overall operating costs are still competitive and within an acceptable range.

High cost performance provides a "stepping stone" for the market promotion of graphene oxide materials. “We are now planning to cooperate with companies that need to deal with heavy metal pollution, establish standard advanced graphene oxide material processing systems and demonstration devices, achieve non-toxic emissions, and further develop practical systems. At the same time, we will develop remediation technologies for heavy metal-contaminated soils.” Hou Shifeng disclosed to reporters.

Industrialization of graphene: breakthroughs in multiple bottlenecks

As a pioneer in the market-oriented development of the preparation and application of graphene and its related materials in China, Lite Nano's products include graphene/graphene oxide preparation and related market development. Although progress has been made in certain fields, Hou Shifeng is very clear that as an emerging industry, the industrialization of graphene in China started from the beginning of 2011. At present, graphene production is generally high in cost, immature technology and unstable products. In order to promote the sustainable development of the graphene industry, it is necessary to improve technology and achieve high-quality, low-cost production of high-quality graphene.

“The controllable quality of graphene is very important for its subsequent application. The layer number, purity, size, thickness, and defects of graphene will all affect its properties. For example, the slight difference of graphene sheet can be its electronic and optical properties. There are different influences.” Hou Shifeng said: “Letter Nano's philosophy is to solve the main problems of uniform control of graphene products first, and give full play to its practical application potential.”

Hou Shifeng told reporters that Lite Nano Materials Co., Ltd., using its own technical reserves, continuously explores new methods and technologies for high flux, multi-level, cross-scale integrated design, efficient preparation and characterization, and development of composite materials, energy, and The graphene design data platform in the environmental field enables precise control of the composition, structure, and properties of graphene materials. The development of graphene green pollution-free preparation technology can realize industrialized production of environmentally friendly, low-pollution, low-energy-consuming, high-yield graphene; design of original graphene energy materials and composite materials; development of materials for environmental pollution and heavy metal processing; R&D A pioneering and forward-looking new graphene material.

"Persistence of mature theories and design concepts is critical to the industrialization of graphene," said Hou Shifeng.