Application of Fly Ash as an Adsorbent for Removal of Air and Water Pollutants

Air pollutants such as volatile organic compounds (VOCs), nitrogen oxides (NOx), and sulfur dioxide (SO2), as well as water pollutants (e.g., heavy metals phosphorous, fluoride, boron, phenolic compounds, and dyes), are harmful to humans and the environment. Effective control and reduction of their pollution is therefore an important topic for today's scientists. Fly ash (FA) is a type of industrial waste that can cause multiple environmental problems if discharged into the air. On the other hand, because of its high porosity, large specific surface area, and other unique characteristics, FA can also be used as a low-cost and high efficient adsorbent for treatment of environment pollutants. This paper reviews the effects of FA on treatment of the air and water pollution, including to the current status of global FA utilization, physicochemical properties, principle of adsorption, and the application direction of FA in the future. Since most researchers only studied the adsorption capacity of pure FA or zeolite (synthesized from FA), the research on the fabrication of nanofiber membranes using FA is still lacking, especially the adsorption of VOCs from air and heavy metals from wastewater using FA nanofiber membranes. Therefore, in this paper, we focus on reviewing and summarizing that FA can be spun into a fiber membrane via electrospinning with the ability to adsorb VOCs and heavy metals from air and wastewater. Moreover, we also evaluate the future application value of FA nanofiber membranes in the field of environmental pollution control. Utilization of nanofiber technology to fabricate multi-functional FA emerging composite materials to mitigate air and water pollution has great potential in the future, especially the use of pollutant materials to control other pollutants.