Adsorption of formaldehyde from airflow using activated carbon derived from pistachio shells.

Formaldehyde is a common indoor air pollutant due to its widespread use. This study investigates the adsorption of formaldehyde from polluted airflow using activated carbon derived from waste pistachio shells. Various experimental conditions were tested, including temperatures (25, 35, 45, and 55 ºC), Empty Bed Retention Times (EBRT) (0.66, 0.92, 1.15, 2.31, and 4.62 seconds), pressures (40, 80, 120, and 160 mbar), and formaldehyde concentrations (50, 150, 300, 400, and 600 mg/L). The best results were achieved at 25 ºC, an EBRT of 2.31 seconds, a pressure of 40 mbar, and formaldehyde concentrations of 50, 150, and 300 mg/L, with removal efficiencies of 88.02%, 80.18%, 86.41%, and 100% for temperature, EBRT, pressure, and concentrations, respectively. The adsorption process was mainly limited by sorption and diffusion in bulk and boundary layers, with ion exchange as the primary adsorption mechanism. The maximum adsorption capacity (qm) was 0.094 mg/g, as predicted by the Temkin model, and the sorption energy was calculated to be 2.08 kJ/mol. Efficiency decreased significantly after the third and fourth reuse cycles, while remaining stable during the first two cycles. This research highlights the potential of pistachio shell-derived activated carbon as an effective adsorbent for formaldehyde removal.