Identifying the best materials for the removal of airborne toluene based on performance metrics - A critical review

For air quality management purposes, numerous materials have been developed and proposed as treatment media for volatile organic compounds such as benzene, toluene, and formaldehyde. Of the numerous airborne volatile organic compounds, toluene, a bulk industrial commodity, is a representative airborne pollutant. To date, numerous materials have been tested for the sorptive treatment of toluene, but all of them, including diverse functionalized materials, suffer from varying degrees of shortcomings for practical applications, such as low sorption capacity at ambient conditions (pollutant pressures <1 Pa). In this respect, activated carbon is currently the most preferable and economical option. This review is organized to offer an updated view on the best sorptive technology for toluene based on performance metrics such as sorption capacity at ambient conditions (e.g., <1 Pa toluene pressure) and economic feasibility by applying the Anna Karenina principle. The results of this investigation will enable the selection of the most practical sorbents for the treatment of toluene and other important volatile organic compounds. Of the low pressure 10% breakthrough volume (toluene <1 Pa, 298 K) of all materials reviewed, an activated carbon is best at 25,000 L g⁻¹. Of the advanced materials, the metal organic framework, MIL-101 has an acceptable value of 985 L g⁻¹. Likewise, judgement based on a figure of merit basis (e.g., regeneration, reusability, breakthrough volume, and cost) confirms the apparent superiority of activated carbon for the removal of aromatic hydrocarbons like toluene over all sorbent materials evaluated on parallel basis.