Skip to Main Content

Strategic Business Insights (SBI) logo

Nanomaterials April 2019 Viewpoints

Technology Analyst: Ivona Bradley

Photocatalyst for Microplastic Degradation

By Madeeha Uppal
Uppal is a technology analyst with Strategic Business Insights.

Why is this topic significant?

As microplastic pollution becomes prevalent in the environment, the need for efficient remediation methods is increasing.

Description

In the past few years, researchers have found tiny fragments of plastic—microplastics—in soil, air, and tap and bottled water and in more than 50 species of comestible marine animals. Research about earthworms has shown the detrimental effects of microplastics, and concern is growing about microplastics' harmful effects on human health.

Scientists at the KTH Royal Institute of Technology (KTH) are leading research funded by the European Union's Horizon 2020 program CLAIM (Cleaning Marine Litter by Developing and Applying Innovative Methods in European Seas) to develop nanorods that can degrade microplastics. The nanorods are composed of zinc oxide, a common photocatalyst, with varying lengths and widths. The scientists tested the degradation of low-density polyethylene microplastic films in the presence of water and the nanorods. After 175 hours under visible-light illumination, the scientists examined the films using optical imaging. The images clearly showed the appearance of cracks and holes in the films as a result of breakdown of polymeric bonds. In addition, the scientists found that the longer nanorods instigate a larger degradation of film surface.

Implications

Each year, millions of tons of plastic flow into the oceans, and because of weathering, with time the plastic breaks down into microplastic. Other sources of microplastic include car tires, clothes, personal-care products, and waste from plastic factories. Current remediation methods require high amounts of energy and often generate toxic products. The KTH zinc oxide photocatalyst is advantageous because it is inexpensive and easy to synthesize. Furthermore, the photocatalyst is energy efficient because it functions in ambient conditions.

Microplastics can carry chemicals that some scientists claim are toxic, carcinogenic, and hormone disrupting in animal models. Some research has also shown that bacteria tend to adhere and proliferate on the surface of microplastics. One of CLAIM's objectives is to develop a photocatalytic device that organizations can install in wastewater-treatment plants, where the device can aid microplastic degradation. In such a device, the KTH nanorods could function as both a photocatalyst for microplastic degradation and an efficient antimicrobial agent.

Impacts/Disruptions

Plastic takes hundreds of years to degrade. With industry experts expecting production to triple by 2050, the need exists to develop methods—such as the KTH technology—for degrading plastic. Concern also exists that with time, plastic and microplastic in the oceans will likely break down into nanoplastics, which—because of their very small size—cells of marine life may absorb, enabling the nanoplastics to move into animal tissue. In December 2018, the UK government announced an investment of £60 million in technologies that tackle plastic waste to achieve the government's goal of zero avoidable waste by 2050.

Many countries have banned rinse-off products containing microbeads, but microplastics are still present in some consumer products, such as cleaning products and cosmetics, and can also unintentionally end up in the environment during simple tasks such as washing of synthetic clothing. However, the European Union's recent proposal of a ban on 90% of microplastic pollutants may lead to less such microplastics-containing products' reaching consumers. In the interim, a need exists for water-treatment plants to intercept microplastic and have effective plastic-recycling or microplastics-degrading technologies on-site.

Scale of Impact

  • Low
  • Medium
  • High
The scale of impact for this topic is: Medium

Time of Impact

  • Now
  • 5 Years
  • 10 Years
  • 15 Years
The time of impact for this topic is: 5 Years to 10 Years

Opportunities in the following industry areas:

Wastewater-treatment plants, recycling, photocatalysis, plastic remediation

Relevant to the following Explorer Technology Areas:

Combining Metal-Organic Frameworks and Nanocrystals

By Madeeha Uppal
Uppal is a technology analyst with Strategic Business Insights.

Why is this topic significant?

New methods of synthesizing multifunctional MOF structures could likely lead to more MOF products' seeing commercial use.

Description

Metal-organic frameworks (MOFs) are crystalline materials consisting of metal ions coordinated to organic linkers, thus forming extended, networked structures. MOFs have attracted considerable interest because of their tunable porous structures and massive surface areas; some MOF surface areas even surpass surface areas of zeolites. Research groups around the world are developing techniques to synthesize hybrid MOF-nanocrystal (NC) structures that offer the beneficial properties of both MOFs and nanocrystals. Challenges exist because MOFs and NCs are contrasting materials, the former being porous and lightweight and the latter being a dense crystalline structure.

Researchers at the Lawrence Berkeley National Laboratory have developed a method of synthesizing a MOF-and-NC superstructure. They demonstrated the method by constructing a two-dimensional, bilayered structure consisting of MOF nanoparticles above iron oxide NCs. The result is a dual-purpose material with both MOF and NC properties intact. The scientists can control the assembly process through molecular interactions.

Another study—conducted by scientists at Rice University—shows how MOFs can grow on aluminum NCs. The scientists developed a simple, one-pot hydrothermal technique that yields NCs enveloped in a MOF shell layer without altering the size or shape of the NC. By varying reaction conditions, the scientists were able to alter the final size and plasmonic properties of the structure. The researchers claim that the MOF layer enhances the photocatalytic activity of the NCs while maintaining its own high, selective, carbon dioxide–absorption capabilities. Furthermore, the hybrid structures were chemically and thermally stable. The scientists also claim that this process is scalable to industrial scale.

Implications

Individually, MOFs and NCs have exceptional properties that are useful in catalysis, chemical separation, electronics, energy storage, optics, and sensing applications. Uniting the two types of materials could lead to novel, dual-functionality materials that exhibit a combination of their properties. Most industrial catalysts use high amounts of energy for optimum performance. Scientists claim that hybrid MOF-NC materials could potentially function as green catalysts that work at much lower temperatures and pressures than the temperatures and pressures at which conventional industrial catalysts work or even harness power from sunlight.

Both studies show how MOFs and NCs can form materials that show superior properties. Additionally, scientists could tailor the properties of the resulting hybrid materials by changing reaction conditions or by choosing different linkers and NCs, such as metallic, semiconducting, or magnetic nanoparticles. Scientists could also alter pore sizes and shapes to develop structures that are selective to molecules or change plasmonic properties for desired wavelength absorption.

Impacts/Disruptions

MOFs are likely to affect many fields of technology significantly. Already, some MOF products are seeing commercialization. For example, MOF Technologies markets a MOF product that elongates the shelf life of fruit and vegetables. The company is also collaborating with IBM to develop MOF products for heat storage. MOFs' fully reversible uptake of gases makes the materials useful as potential gas-storage systems, negating the need for bulky, pressurized tanks and avoiding leaks. NuMat Technologies is an example of one company that supplies highly toxic gases in MOF-delivery platforms. And in medicinal applications, MOFs can have use in drug delivery and medical imaging; MOF antimicrobial systems already exist in the market.

Scale of Impact

  • Low
  • Medium
  • High
The scale of impact for this topic is: Medium

Time of Impact

  • Now
  • 5 Years
  • 10 Years
  • 15 Years
The time of impact for this topic is: 5 Years

Opportunities in the following industry areas:

Catalysis, medicine, carbon capture, urban cleanup, energy storage, sensors, gas storage

Relevant to the following Explorer Technology Areas: