A large proportional of volatile organic compounds (VOCs) are released into the environment from various industrial processes. The current study elucidates an application of a simple adsorption phenomenon for removal of three main types of VOCs, i.e., benzene, xylene and toluene, from an air stream. Two kinds of adsorbents namely acid digested adsorbent and activated carbon are prepared to assess the removal efficiency of each adsorbent in the indoor workplace environment. The results illustrate that the adsorbents prepared from corrugated sheets were remarkably effective for the removal of each pollutant type. Nevertheless, activated carbon showed high potential of adsorbing the targeted VOC compared to the acid digested adsorbent. The uptake by the adsorbents was in the following order: benzene > xylene > toluene. Moreover, maximum adsorption of benzene, toluene and xylene occurred at 20 °C and 1.5 cm/s for both adsorbents whereas minimum success was attained at 30 °C and 1.0 cm/s. However, adsorption pattern are found to be similar for each of the the three aromatic hydrocarbons. It is concluded that the corrugated sheets waste can be a considered as a successful and cost-effective solution towards effective removal of targeted pollutants in the air stream.
How to cite: Arshad, R., and Raza, H.M.H., 2016. Removal of VOCs from Air Stream with Corrugated Sheet as Adsorbent. Bulletin of Environmental Studies 1(1) 10-17.
Copyright © 2016 Arshad, Raza,. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Edited by: Naeem Shahid (UFZ, Germany)
Reviewed by: Muhammad Shahid (COMSATS, Pakistan) & Sudibyo bin Solikan (KFUPM, Saudi Arabia)
Published Online: 13/10/2016
VOCs are an important class of air pollutants whose widespread contamination is a matter of growing public concern. They are usually present in the atmosphere as gases, but can also exist as liquid or solids under normal conditions of temperature and pressure, i.e., their vapor pressure ranges between 0.13 kPa to 101.3 kPa at 20 °C (Boeker and Grondelle, 2011).VOCs come into the environment by both natural (i.e., forest fires, grasslands, anaerobic processes, swamps, blogs, marshes), and anthropogenic activities (i.e., chemical industries, oil refining, petrol storage, landfill wastes, solvent usage, burning of fossil fuels) (Haughton and Hunter, 2003). Notwithstanding, their indoor sources include building materials, furnishings, occupant activities and even ventilated air (Zhibin et. al., 2000). Among different types of VOCs, benzene, toluene, xylene, and styrene are found in higher proportions in the indoor environment (Yao, 2008).
Many of the VOCs are harmful to living organisms as they can cause liver disorders, kidney failure and complications to central nervous system. The onset of asthma is another serious health impairment which has been associated with VOCs. Moreover, some of the VOCs such as benzene, formaldehyde, naphthalene, trichloroethylene etc. have been recognized as human carcinogens (Yao, 2008). Hence, their removal from the environment is a key challenge for future studies. Adsorption, being a cost-effective and environmental friendly methodology, has been widely used to remove the variety of VOCs from gas streams (Parvulescu et. al., 2012). Different materials have been employed to test the adsorption of array of VOCs such as fruits (Won et. al., 2001), Arundo donax L. shoots (Basso et. al. 2005), cork powder waste (Cardoso et. al., 2008), coconut shell (Li et. al., 2011), date pits, and olive stones (Daifullah et. al., 2003) . Chemically activated carbon has been appeared as a common and inexpensive adsorbent with good potential to remove VOCs due to its high adsorption capacity (Silvestre-Albero et. al., 2009). Heavy metals enter into plants mainly via roots from the soil and travel along the food chain (Shahid et al., 2015). Once entered in the bodies of living organisms, heavy metals can pose serious threats due to their non-biodegradable nature, long biological half-lives and their potential to accumulate in different body parts, e.g., fatty tissues (Shahid et al., 2015). Moreover, most of the heavy metals are extremely toxic because of their solubility in water. Even low concentrations of heavy metals have damaging effects on human and animal populations (Uzu et al., 2011) by causing cardiovascular, kidney, nervous, mental impairment and bone diseases (Yargholi et al., 2008). It has been reported that the prolonged consumption of heavy metals contaminated food can impair liver, kidney, cardiovascular, nervous and/or cancers (Järup, 2003).
The current study aims to remove an abundant class of VOCs namely benzene, toluene and xylene from the work environment. For this purpose an adsorbent was formed by treating corrugated sheets.
Materials and Methods
Reagents and Materials
All chemicals and reagents were of analytical grade. The laboratory equipment was washed with distilled water and placed in 6 Molar Hydrochloric Acid for 24 hours and washed again with doubly distilled water. 5% HCl (Riedel-deHaen) was prepared by dissolving 10ml in 190ml of distilled water and was standardized against 0.1N sodium hydroxide. Phenolphthalein Indicator (Riedel-deHaen) was prepared by dissolving 0.5gm in 50ml of Ethanol (Riedel-deHaen) and 50ml distilled water. The hardware employed included Air Pump (ACO 9630, Coastal Koi), 12V DC Battery (UBC 002, UltiPower System Engineering), Digital Thermometer (HI 8314, HANNA Instrument), Electronic Weighing Balance (JW-604, Zhengya Weighing Apparatus), and an oven with temperature ranging from 0°C to 300°C (UN75PA, Memmert).
Sample Collection, Drying and Shredding
Approximately, 5kg of cardboard boxes (corrugated sheets) were collected from SOMA Lab, Samanabad, Lahore. The cardboard boxes served as packing cases in which medicine and other equipment were brought to the Lab.The collected corrugated sheets were cropped to small cubes and placed in an oven for 24 hours at 100 °C to remove any moisture content. The small cubes were weighed again after oven drying to estimate the final weight. 4.7 kg of sample was fed to the shredding machine to obtain smooth shredded sample and sieved through a mesh size of 0.6 mm.
Procedure for Preparing Acid Digested Adsorbent: 1.5 kg of shredded sample was washed thrice with distilled water and later with 5% of HCl. After washing, the sample was placed in an oven for 24 hours at 100 °C or until it was completely dried. The final pH was set to 6 since acid digested adsorbent was being prepared (Ashoka and Inamdar, 2010).
Procedure for Preparing Activated-Carbonized Adsorbent: A medium sized mud vessel was used for carbonization of the sample. Approximately, 3 kg of dried sample was put in the vessel whose lid was sealed with the help of calcium sulfate. In order to create an inert oxygen free atmosphere inside the vessel, two holes were drilled into the lid with the help of a drill machine. The nitrogen gas was passed through one of the holes using glass tube at a pressure of 2 kg F/cm2, while the other hole was left open to remove the internal air. Subsequently, after 3 minutes of gas flow, both holes were sealed tightly and then the vessel was placed on a medium intensity flame. The carbonization process took approximately 10 hours followed by activation procedure, in which 1.96 kg of the above charcoal was activated by applying concentrated hydrochloric acid (HCl). The charcoal was mixed with 300 ml of HCl and then left for 24 hours. The mixture was filtered and the residue was washed with distilled water until all the acid was removed. The acidity was checked in the filtrate using phenolphthalein as an indicator. The washed residue of the activated charcoal was then dried in an oven at 100 °C for 24 hours or until the entire sample was dried. The prepared activated charcoal was then stored in an air-tight glass jar having final pH of 5 (Tan et. al. 2008).
Experimental Setup and Analysis
Approximately 28 grams of adsorbent was packed in a glass column with an internal diameter of 1.25 cm and a height of 40 cm. The glass column was wrapped in an insulating layer and the adsorbent was heated by spiraled electric wire present inside the glass column. The wires were directly attached to a battery that was a source of current to the system. Digital thermometer was used to measure the fixed bed temperature. Air was pumped to the conical flask containing the liquid aromatic hydrocarbons by means of air pump whose flow was adjusted with a flow meter. The system temperature was maintained by cooling bath. The mixture of air and hydrocarbons were carried to the bottom of the column which up-flowed through the adsorption fix bed. As adsorption began, the weighing scale of the electric balance revealed an increase in the weight of the glass column and continued to increase until there was no change in weight of the column thus indicating the ultimate saturation (Dobre, T. et. al. 2010). Schematic diagram for the experimental setup is shown as graphical abstract.
Results and Discussion
The difference in net weight of corrugated sheet before and after oven drying, shredding, acid digestion, and carbanization are presented in Table 1. Each of the applied method resulted into loss of net weight; particularly, 5% for oven drying, 4.74% for shredding, 20% for acid digestion, and 34.5% for carbonization. The findings are in accordance with the previous studies conducted for different adsorption purposes (Mohee et al., 2008).
Detailed description on removal of each pollutant (benzene, toluene, and xylene) by acid digestion and carbonization is further provided in Table 2. It can be seen that both of the adsorbents exhibited visible uptake of the adsorbates however, the activated carbon had more potential and efficiency to remove the three VOCs in comparison to the acid digested adsorbent. This may be due to the fact that activated carbon presents a much larger surface area thus enhancing the adsorption capacity of the adsorbent (Khalili, et. al., 2000). Moreover, adsorption by the solid phase proceeded linearly until a saturation value was reached. Maximum adsorption of benzene, toluene and xylene was achieved at 20 °C and 1.5 cm/s for both adsorbents whereas minimum levels were attained at 30 °C and 1.0 cm/s. At lower temperatures, higher adsorption values were observed in a shorter time span and vise verse. This could be due to the fact that stated VOC vaporize less vigorously hence allowing them to efficiently bind with the adsorbent (McClenny and Holdren, 1999). The graphical representation of all the results can be seen in supplementary dataset (supplementary figures a-l) at different temperatures and airflow velocities.
The experimental data exhibits that the adsorbents, both acid digested and activated carbon, prepared from corrugated sheets were effective for the removal of aromatic hydrocarbon like benzene, toluene and xylene. The adsorption efficiency of both adsorbents had been remarkable. Comparatively, activated carbon bore more potential of adsorbing the targeted VOC then acid digested adsorbent. The uptake by the solid phase was in the order of benzene > xylene > toluene. Maximum adsorption of benzene, toluene and xylene was achieved at 20°C and 1.5cm/s for both adsorbents whereas minimum levels were attained at 30°C and 1.0cm/s. Adsorption pattern was same for the three aromatic hydrocarbons. At lower temperatures, higher adsorption values were observed in a shorter time span and vise verse. Since the studies in the literature focusing specifically on VOCs removal is rare, the results of this study may contribute to the following research on VOCs biosorption.
Compliance with ethical standards
Conflict of Interest
The authors declare no conflict of interest.
Ashoka, H. S., Inamdar, S. S., 2010. Adsorption removal of Methyl Red fom Aqueous Solution with treated Sugarcane Baggase and Activated carbon – A Comparative Study, Golbal Jouranl of Environmental Research, 4(3), pp. 175 – 182.
Basso, M. C., Cukierman, A. L., 2005. Arundo donax-Based Activated Carbons for Aqueous-Phase Adsorption of Volatile Organic Compounds, Industrial and Engineering Chemistry, 44(7), pp. 2091–2100.
Boeker, E., Grondelle, R., 2011. Environmental Physics: Sustainable Energy and Climate Change, 3rd Edition, John Wiley & Sons, England, pp. 128-129.
Cardoso, B., Mestre, A. S., Carvalho, A. P., Pires, J., 2008. Activated Carbon Derived from Cork Powder Waste by KOH Activation: Preparation, Characterization, and VOCs Adsorption, Industrial and Engineering Chemistry, 47(16), pp 5841–5846.
Daifullah, A. A, Girgis, B. S., 2003. Impact of surface characteristics of activated carbon on adsorption of BTEX, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 214(1-3), pp. 181-193.
Dobre, T., Parvulescu, O. C., Iavorschi, G., Stroescu, M. Stoica, A., 2010. Experimental Study of VOCs Adsorption onto Fixed Bed Activated Carbon, Analele Universității din Oradea, Fascicula: Ecotoxicologie, Zootehnie și Tehnologii de Industrie Alimentar , 25, pp.841-846 Haughton, G., Hunter, C., 2003. Sustainable Cities, Regional Studies Associations, London. p. 147.
Haughton, G. and Hunter, C., 2004. Sustainable cities. Routledge.
Järup, L., 2003. Hazards of heavy metal contamination. British medical bulletin, 68(1), pp.167-182.
Khalili, R. N., Pan, M. Sandi G., 2000. Determination of Fractal Dimensions of Solid Carbons from Gas and Liquid Phase Adsorption Isotherms, Journal of Carbon, 38(4), pp 573 - 588
Li, L., Liu, S., Liu, J., 2011. Surface modification of coconut shell based activated carbon for the improvement of hydrophobic VOC removal, Journal of Hazardous Materials, 192(2), pp. 683-690.
McClenny, W. A. and Holdren, M. W, 1999, Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air, Chapter 15: Determination of Volatile Organic Compounds (VOCs) in Air Collected in Specially Prepared Canisters and Analyzed by Gas Chromatography/Mass Spectrometery, pp 10 - 28
Parvulescu, V. I., Magureanu, M., Lukes, P., 2012. Plasma Chemistry and Catalysis in Gases and Liquids, Wiley-VCH, Germany, pp. 133-136.
Shahid, M., Khalid, S., Abbas, G., Shahid, N., Nadeem, M., Sabir, M., Aslam, M. and Dumat, C., 2015. Heavy metal stress and crop productivity. In Crop Production and Global Environmental Issues (pp. 1-25). Springer International Publishing.
Silvestre-Albero, A., Silvestre-Alb ero, J., Sepúlveda-Escribano, A., Rodríguez-Reinoso, F., 2009. Ethanol removal using activated carbon: Effect of porous structure and surface chemistry, Microporous and Mesoporous Materials, 120(1-2), pp. 62-68
Tan, I. A. W., Ahmad, A. L., Hameed, B. H., 2008. Activated Carbon from Coconut Husk: optimization study on Removal of 2,4,6-Trichlorhenol using Response Surface methodology, journal of hazardous materials, 153(1), pp. 709 – 717.
Uzu, G., Sauvain, J.J., Baeza-Squiban, A., Riediker, M., Sánchez Sandoval Hohl, M., Val, S., Tack, K., Denys, S., Pradere, P. and Dumat, C., 2011. In vitro assessment of the pulmonary toxicity and gastric availability of lead-rich particles from a lead recycling plant. Environmental science & technology, 45(18), pp.7888-7895.
Won, D., Corsi, R. L., Rynes, M., 2001. Sorptive interactions between VOCs and indoor materials, Indoor Air, 11(4), pp. 246-256.
Yao, M., 2008. Removal of Volatile Organic Compounds from Indoor Air Using Regenerative Activated Carbon Fiber Cloth, ProQuest Information and Learning Company, Michigan, p. 1.
Yargholi, B., Azimi, A., Baghvand, A., Liaghat, A., Fardi, G., 2008. Investigation of cadmium absorption and accumulation in different parts of some vegetables. American-Eurasian Journal of Agricultural & Environmental Sciences 3(3), 357-364.
Zhibin, Z., Gang, N., Shaw, C.Y., Gao, L., 2000. Adsorption Capacity of Activated Carbon for n-Alkane, VOCs, Proceedings, Engineering Solutions to Indoor Air Quality Problems, 17(19), pp. 244-253.