Control environmental pollutants with heterogeneous catalysts
There has been considerable interest in the applications of molybdenum (Mo) materials due to their abundant electronic properties and their potential applications in the control of environmental pollutants.
To study: Heterogeneous molybdenum catalysts for the control of environmental pollutants. Image Credit: kosmos111 / Shutterstock.com
A recent review in the EcoMat The review aimed to highlight and summarize a range of new developments in the use of Mo-based materials to better control water and air pollutants while exploring a range of methods with the potential to ‘Optimizing Mo-based materials for use in high efficiency catalysts.
Air and water pollution remain one of the world’s most pressing problems, putting at risk vital ecosystems, food chains and the environment necessary for human life.
Water pollution tends to come from heavy metal ions, refractory organic pollutants, and bacteria – toxic and harmful pollutants from industrial processes and wastewater that do not break down naturally. This problem is aggravated by the eutrophication of water bodies which can create favorable conditions for the reproduction of a large number of bacteria, polluting more and negatively affecting the quality of the water.
Air pollution is mainly composed of volatile organic compounds (VOCs), nitrogen oxides (NOx), sulfur oxides (SOx) and carbon dioxide (CO2) – pollutants that come mainly from the combustion of fossil fuels. The impact of CO2 as a greenhouse gas has been widely documented, with significant amounts of CO2 having a considerable impact on the Earth’s climate.
Image credit: Ji, J, Bao et al., EcoMat
A range of technologies and approaches have been developed to meet these challenges, including adsorption on activated carbon, ultrafiltration and advanced oxidation processes (AOP) aimed at tackling water pollution problems. ; and thermal catalysis, photocatalysis and electrocatalysis which are regularly used in the ongoing fight against air pollution.
Catalysts are at the heart of many of these methods and technologies, with molybdenum (Mo) -based catalysts such as molybdenum disulfide (MoS2), molybdenum dioxide (MoO2), molybdenum trioxide (MoO3), molybdenum carbide (MoCx) and molybdenum powder have been widely used in recent decades.
Mo-based materials offer excellent potential for use in water pollution control, given routine use in PDOs as advanced catalysts and co-catalysts. These are also essential to many Fenton or Fenton-type reactions, where the distinct properties of materials, including MoS2, MoO2, and molybdenum powder are used to support processes such as degradation of pollutants, sterilization and reduction of heavy metal ions.
In particular, Mo-based catalysts offer a promising way to address the risks posed by metallurgical wastewater, which typically includes a high number of extremely toxic high-valent metal ions. These ions cause significant damage to human health and can decimate local ecosystems, requiring the development and implementation of robust, reliable and efficient catalysts capable of effectively removing heavy metal ions.
Mo-based catalysts offer a potential solution to this pollution, supporting and enabling reactions and processes such as physical adsorption, chemical redox reaction and photocatalytic reactions capable of removing heavy metals and make them harmless.
Mo-based catalysts have been widely used to support the development of NOx reduction with ammonia, as well as CO2 conversion by the application of thermocatalysis, photocatalysis and electrocatalysis.
Mooing3 is also at the heart of the promotion and stabilization of industrial NH3-SCR catalyst V2O5-Mowling3(AJ3) / TiO2, and although there have been a number of advances in the use of Mo-based molecular sieves, the hypotoxicity of Mo, its minimal cost and its large specific surface area have been enhanced.
Reducing carbon dioxide production is key to tackling air pollution, and Mo-based catalysts have offered excellent potential in a range of CO2 conversion technologies.
For example, MoS2 can be used in CO2 electrochemical reduction and photoreduction, while MoCx offers good potential for use in CO2 hydrogenation and CO conversion2 useful fuel products.
The main drawbacks of many Mo-based materials stem from limitations around cost and capacity, which means that many of these very beneficial materials can only be applied in small-scale or laboratory applications.
In order to realize their full potential to help combat air and water pollution on a global scale, it is necessary to transform these systems into viable applications on an industrial scale. Scaling up and optimizing these catalysts will be essential to enable their widespread use.
As technology advances and their application becomes more integrated into mainstream industrial processes, the highly beneficial and promising properties of Mo-based catalysts are prompting more and more research into their use in the control of a number of environmental pollutants; research which can only lead to their wider and more generalized adoption.
Ji, J, Bao, Y, Liu, X, Zhang, J, Xing, M. Heterogeneous molybdenum catalysts for the control of environmental pollutants. EcoMat. 2021; e12155. doi: 10.1002 / eom2.12155 https://onlinelibrary.wiley.com/doi/full/10.1002/eom2.12155