Removal of Formaldehyde and Btex in Indoor Aır Usıng Actıvated Carbon Produced From Horse Chestnut (Aesculus Hippocastanum L.) Shell

Abstract

Activated carbon can be used in the adsorption of volatile organic compounds in abundant quantity in indoor air. This study aims to produce a material to be used for cleaning the indoor air.using activated carbon transformed from horse chestnut (Aesculus hippocastanum L.) shell, which is a kind of organic lignocellulosic waste and easily found in nature. The scope of the research consists of activated carbon production, characterization processes, hydrogen storage capacity measurements, formaldehyde and BTEX (benzene, toluene, ethylbenzene, m, p-xylene, o-xylene) adsorption experiments and cost-benefit analysis.

Activated carbon was produced by chemical activation method using carbonization process at different temperatures (400, 500, 550, 600, 700, 800 and 900°C) and at different concentrations (1 M, 3 M and 5 M) of ZnCl2 in order to determine the most efficient production conditions of activated carbon. As a result of the characterization tests, optimum conditions were determined as the carbonization process at 600°C and the use of ZnCl2 at 3 M concentration. The characteristic properties of activated carbon were revealed by conducting BET, SEM/EDX, XRD, FTIR-ATR, DTA/TG analyzes of the activated carbon samples and measuring the hydrogen storage capacity. Hydrogen storage capacities were tested using ZnCl2 at 25°C and -196°C. The highest capacity was found in the use of 3 M ZnCl2 and at -196°C temperature. Accordingly, capacity was measured as 3.18 wt% under 43907.27 mbar pressure.

A batch reactor with a volume of 0.002 m3 was produced by using glass material for adsorption experiments. In the experiments, commercial activated carbon removal efficiencies purchased from the market were compared with the efficiency of activated carbon produced within the scope of the thesis. Considering the limit values for formaldehyde and BTEX gases values with low concentrations for formaldehyde of 170±14.92, 260±23.76, 720±47, 1040±68.47, 1220±72.14, 1900±83.37, 3290±95.44 and 7650±111.18 μg/m3. Highly concentrated formaldehyde values were studied as 30,000±207,44, 50,000±338,61, 60,000±376,89 and 110,000±497,21 μg/m3. Initial concentrations were determined as 2.4±0.45, 5.5±1.09, 54±10.73 and 322±47.80 μg/m3 for benzene, 3.7±0.58, 9±2.62, 86±15.83 and 414±47.26 μg/m3 for toluene, 9±0.66, 9.2±1.59, 90±15.55 and 430±46.64 μg/m3 for ethylbenzene, 3.4±0.72, 8.5±1.32, 83±12.95 and 397±82.10 μg/m3 for m, p-xylene, 5.2±0.82, 10±2.49, 100±24.38 and 483±102.67 μg/m3 for o-xylene, 18.5±1.89, 42±4.97, 412±48.74 and 2045±203.37 μg/m3 for BTEX. Isotherm parameters for commercial activated carbon and activated carbon produced within the scope of the thesis are presented by comparing. The data were applied to Dubinin-Radushkevich, Langmuir and Freundlich isotherms, and it was observed that the isotherms favorable to the equilibrium data. It was determined that the findings are more suitable for the Freundlich isotherm among these isotherms.

The best performing values in terms of efficiency were found at low concentrations. In the formaldehyde removal test conducted at a concentration of 170±14.92 μg/m3, the efficiency of commercial activated carbon was 47.83%, while the efficiency of the produced activated carbon reached 73.37%, and the highest concentration value was 110,000±497.21 µg/m3. While the values were 26.39% for commercial activated carbon, it was 32.89% for activated carbon produced within the scope of the thesis. Commercial activated carbon was 65.23%, while the activated carbon produced was 73.86% at benzene removal experiment. Commercial activated carbon was 43.44%, while the activated carbon produced was 63.31% at toluene removal experiment. Commercial activated carbon was 50.08%, while the activated carbon produced was 65.96% at ethylbenzene removal experiment. Commercial activated carbon was 42.04%, while the activated carbon produced was 60.28% at m, p-xylene removal experiment. Commercial activated carbon was 78.99%, while the activated carbon produced was 88.07% at o-xylene removal experiment. Commercial activated carbon was 52.43%, while the activated carbon produced was 71.7% at BTEX removal experiment.

The efficiency values obtained with the activated carbon produced within the scope of the thesis were found to be higher than commercial activated carbon for formaldehyde and BTEX concentrations. It was determined that horse chestnut shell is a raw material with a high potential due to its pore structure, high surface area and adsorption capacity in activated carbon production. It was found efficient for the removal of formaldehyde and BTEX from indoor air using decorative products containing activated carbon.