Progress in Hydrophobic or Superhydrophobic Modification of Activated Carbon
Activated carbon is one of the most widely used absorbents in the field of removing various organic substances in polluted environments,due to its abundant pore structure and a high degree of surface reactivity.However,the surface chemical properties of activated carbon are rich in hydrophilic functional groups.This means that when water molecules and organic pollutants coexist,they compete for active sites on the surface of activated carbon.In this situation,activated carbon tends to preferentially adsorb water molecules,which drastically diminishes its adsorption capacity of the desired organic pollutants.This negatively affects its efficiency when used in humid environments.Therefore,how to improve the moisture and water resistance of activated carbon is an urgent problem that needs to be resolved in the application of an complex multi-component environment.A large number of studies have shown that modifying activated carbon to be hydrophobic or superhydrophobic can effectively tackle the thorny problem.Currently,numerous researchers both domestically and internationally have studied primary hydrophobic or superhydro-phobic methods of activated carbon,which include high-temperature heating treatment modification,loaded metal oxide modification,organic molecular modification,silicone coating modification,and organic-inorganic composite superhydrophobic coating modification.Those methods have been confirmed effectively isolate water vapor from being adsorbed into the pore space by activated carbon.Researchers have also found that improving the moisture and water resistances of the modified activated carbon is of great significance.Such developments demonstrate the practical application value and far-reaching prospects of hydrophobic or superhydrophobic activated carbon.This review aims to highlight the progress made in research on the application of hydrophobic or superhydrophobic modification of activated carbon.Based on the mechanism of activated carbon's adsorption and desorption for organic matter,the significant factors that affected its adsorption performance were carefully discussed.It was demonstrated that the physical structures and surface chemistry properties had a significant impact on activated carbon's absorption performance.These influencing characteristics included the specific surface area,pore size and distribution,functional groups and more.To better understand those properties,firstly,an overview of different types and sources of activated carbon was provided.The specific surface area,pore distribution,and surface functional groups of the carbon depended on its type and source,which ultimately affected its absorption performance.To further optimize the activated carbon's performance,there were different hydrophobic or superhydrophobic modification preparation techniques available.Those methods enhanced the hydrophobic and alter the surface chemistry properties leading to increased adsorption capacity.According to those modification preparation techniques,the change in the adsorption capacity of the modified activated carbon to the target organic matter in a humid environment before and after modification were further explored.In addition,the actual application effect of hydrophobic or superhydrophobic activated carbon in a wide variety fields,such techniques as wastewater removal organic treatment,exhaust removal organic gas treatment,and the newly developed electrochemical catalytic hydrophobic treatment were discussed.At the same time,their respective advantages and disadvantages,as well as the current limitations that need to be resolved for the existing technologies were pointed out.In the end,this article examined the challenges faced by activated carbon and explored the potential development trends for the hydrophobic or superhydrophobic modification of activated carbon,which showed great promise.It was hoped to provide theoretical reference and basis for the research and development of hydrophobic or superhydrophobic activated carbon in the field of realistic application.
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