Enhanced removal efficiency of toluene over activated carbon under visible light

Toluene removal rates using activated carbon (AC) at various relative humidity (RH) levels (0%, 30%, 60%) were compared under dark and visible-light conditions. Light exposure significantly increased toluene-removal efficiency independent of RH. When AC was pre-treated with an optimal concentration of HNO3, its toluene-removal efficiency was enhanced further with light, an effect that can be attributed to increased surface-area and porosity. Fourier-transform infrared analysis confirmed that exposure of HNO3-modified AC to light induced partial oxidation of toluene. Within visible-light range (380-650 nm), shorter wavelengths were more effective for toluene-removal compared with longer wavelengths. This suggests that hydroxyl groups formed on AC-surface under light strongly interact with aromatic rings of toluene, allowing for greater uptake of toluene. Moreover, AC can sustain its photo-activity when mixed with cement and cured, suggesting its potential applications in airpurifying building materials. An efficient and practical method for regeneration of spent AC is also demonstrated.

Automated summary

The study showed that pre-treating activated carbon with HNO3 can enhance toluene removal efficiency under light exposure. Shorter wavelengths of visible light were more effective in toluene removal compared to longer wavelengths. Activated carbon can sustain its photocatalytic activity when mixed with cement, indicating its potential applications in airpurifying building materials.