Removal of volatile organic compounds using fixed bed adsorption: optimization using Taguchi methodology and grey relational analysis

This paper emphasizes the need for the stripping of the volatile organic compounds (VOCs) released from various sources owing to their deleterious effects on health and the environment. Granular activated carbon was applied as an adsorbent to adsorb VOCs such as toluene and xylene. This study investigated the influence of the operating variables such as length of the packed bed (0.015-0.025 m), VOC concentration in the inlet gas (2500-7500 ppm), and volumetric flow rate of gas (35-105 mL min-1) on the performance of the adsorption column. Adsorption capacities as high as 6.2 kg kg-1 and 9.054 kg kg-1 were observed for toluene and xylene, respectively, at the VOC inlet concentration of 7500 ppm. Taguchi methodology was then used for the design of experiments by utilizing an L9 orthogonal array with an objective to get a longer breakthrough time and maximum utilization of the adsorbent till the breakthrough. The breakthrough times obtained were 10.9 h (toluene) and 18.04 h (xylene). The maximum adsorbent usage till breakthrough (in %) was estimated to be 73.24 (toluene) and 84.36 (xylene). Subsequently, the grey relational analysis technique yielded the optimal parameters (length of the packed bed = 0.025 m, VOC concentration in the inlet gas = 5000 ppm, and volumetric flow rate of gas = 35 mL min-1) when both the responses were optimized simultaneously. Gas flow rate was found to be the most sensitive parameter.