Recently, Assistant Professor Su Yang and collaborators from Shenzhen International Graduate School of Tsinghua University discovered that graphene can be used to efficiently and accurately adsorb gold resources in water. Taking advantage of this phenomenon, they demonstrated the use of graphene to recover gold resources from electronic waste.
(Source: Nature Communications)
The research background of this work can be summarized in one sentence: the sustainable development of global gold resources and the problem of electronic waste pollution. From the perspective of sustainable development of gold resources, under the challenge of global sustainable development, the sustainable development of resources is undoubtedly very important.
As a key resource, gold is not only used in jewelry, but is also widely used in electronic devices. This is mainly because gold has very high conductivity and chemical stability. Many components of our electronic devices, such as mobile phones and computers, require a layer of gold plating to ensure good electrical contact and stable signal transmission.
If you think carefully about the supply and demand relationship of gold resources, you will find that there is a very obvious imbalance. Simply put, gold is a non-renewable resource and its reserves in the earth's crust are limited. But judging from the service life of our commonly used electronic devices, for example, mobile phones are usually replaced in 1-3 years. If the gold resources in these abandoned mobile phones cannot be effectively recycled (in fact, the current global recycling rate of electronic waste is low less than 20%), then this part of the gold resources is wasted.
Of course, there is not much gold on a mobile phone, but if this situation is magnified to a global scale, the amount of gold resources we waste will be very considerable. This means that humans have used a large amount of gold resources, but have not recycled it effectively. If this continues, one day in the future, there will not be enough gold resources for human use.
(Source: Nature Communications)
As for e-waste pollution, because e-waste contains a wide variety of materials, as far as metal materials are concerned, it includes copper, nickel, gold, lead, tin, aluminum, chromium, etc. . Recycling of e-waste means separating and purifying materials of different materials from e-waste so that these materials can be reused.
Currently, the global recycling rate of e-waste is less than 20%. Gold is the element with the highest economic value in e-waste. Therefore, efficiently and selectively extracting gold resources from e-waste will likely promote the recycling rate of e-waste and provide new solutions to solve e-waste pollution.
Back to the research work itself, the interaction between graphene and gold ions was actually reported in 2010, but this was mainly used to dope graphene with gold ions and regulate its electronic structure.
Starting from the material structure, the team used a derivative of graphene (reduced graphene oxide) to study its adsorption of gold ions and explore how to extract gold from waste gold-containing resources. This is new to the field of graphene. discovery. From the perspective of gold ion extraction adsorption materials, many nanoporous materials have previously been reported for similar uses.
This work found that graphene’s adsorption capacity for gold is nearly an order of magnitude higher than that of existing materials, and it can achieve precise adsorption of gold under the conditions of 14 coexisting elements, which is something that previous research has not or is difficult to achieve.
Recently, a related paper titled "Highly Efficient and Selective Extraction of Gold by Reduced Graphene Oxide" was published on Nature Communications [1].
(Source: Nature Communications)
Professor of Shenzhen University of Technology, Chinese Academy of Sciences (in preparation) and Shenzhen Institute of Advanced Technology, Academician Cheng Huiming, Nobel Prize winner in Physics, University of Manchester, and Tsinghua University Shenzhen international graduate student Professor Andre Geim of the Institute of Geim Graphene Center Geim) and Su Yang, assistant professor at Tsinghua University Shenzhen International Graduate School, are the corresponding authors of the paper . Li Fei, a 2020 doctoral student at Tsinghua University Shenzhen International Graduate School, and postdoctoral Zhu Jiuyi are the co-first authors.
▲Picture | Su Yang (Source: Su Yang)
Generally speaking, the reviewers recognized the phenomenon reported this time and the gold adsorption performance of graphene, but they had concerns about the mechanism explained. Of course this is understandable. Therefore, the team spent a lot of time and conducted many experiments to explain the mechanism as clearly as possible.
At the beginning of the research, the research team first screened a batch of graphene materials. It took doctoral student Li Fei about 1-2 months to select graphene oxide reduced with vitamin C. Then they spent about half a year verifying the experimental phenomenon, exploring the mechanism behind the experimental phenomenon, and conducting further experiments to verify it.
This included a series of gold adsorption experiments, the use of real electronic waste for recycling, and the development of a continuous gold adsorption process based on graphene membranes. With these solid experimental evidences, the team spent about 1-2 months discussing this experiment repeatedly with Nobel Prize winner Professor Andre Geim of the University of Manchester in the UK, and they did a more quantitative Su Yang and others also added more experiments to understand the experimental phenomenon more clearly. It took about a year to finalize it.
(Source: Nature Communications)
Su Yang said: "During the research, Teacher Cheng Huiming and Professor Geim raised many questions and hypotheses that we had not thought of before, and encouraged us to verify or eliminate these hypotheses through experiments and theories. We also used this These experiments will make the results more complete. The other is to do useful research.” During
, the two scientists proposed to verify Su Yang’s experimental results in real scenarios, and suggested and encouraged him to test different actual scenarios. Gold extraction performance of graphene.
The cost of graphene raw materials is one percent of the cost of the gold that can be extracted, or even lower. Combined with its efficient and precise gold extraction performance, Su Yang believes that its experimental results may be used to efficiently and accurately extract gold from electronic waste. Another possible potential application is that in the current semiconductor and electronics industry processes, after the concentration of the gold plating solution is reduced to a certain level, it can no longer be used. Therefore, they are currently studying whether graphene can be used to recover gold from these low-concentration electroplating waste solutions.
At present, they are still continuing to do this research. From the perspective of basic research, there are still many phenomena worthy of further exploration. Since there is no clear conclusion yet, we will not go into details here. From an application perspective, it is currently trying to scale up experiments. In addition, continuous adsorption based on graphene membranes is more likely to be directly applied in industrial processes, but there are still many experimental phenomena that need to be explored in depth, and they are also continuing to follow up on the technical problems of large-area preparation.
Reference:
1. Li, F., Zhu, J., Sun, P. et al. Highly efficient and selective extraction of gold by reduced graphene oxide. Nat Commun 13, 4472 (2022). https://doi.org/10.1038/s41467-022-32204-4
