Evaluation of Ozone Removal by Spent Coffee Grounds

Activated carbon is the most known material used to adsorb ozone. Activating carbonaceous materials by ozonation is commonly used to produce activated carbon, however, requiring sophisticated skills and professional equipment. This paper presents a reversed idea: to adsorb ozone using an unactivated carbonaceous material, coffee. Three powder adsorbents are presented: fresh coffee (unactivated), spent coffee grounds (unactivated), and activated carbon (commercially available). The test is conducted by measuring and comparing the ozone concentration in an ozone-supplied chamber with or without the ozone adsorbent. The results show that, at the specific conditions, the peak ozone concentration is lowered by 38% to 56% when the chamber has the activated carbon. At the same conditions, the peak ozone concentration is lowered by 25% to 43% when the chamber has the coffee powders (either fresh or spent). The elemental analysis demonstrates that the oxygen content after the ozone adsorption increases by 20%, 14.4%, and 34.5% for the fresh coffee, the spent coffee grounds, and the activated carbon, respectively. The characteristic analysis (the Fourier-transform infrared spectroscopy, the thermogravimetric, and the Brunauer-Emmett-Teller) suggests that the unactivated coffee is not porous, however, contains various organic compounds that could react with and consume ozone.