Applied Surface Science 266 (2013) 118–125 Contents lists available at SciVerse ScienceDirect Applied Surface Science jou rn al h om epa g e: www.elsevier.com/locate/apsusc Surface modification of oil fly ash and its application in selective capturing of carbon dioxide Ali L. Yaumi, Ibnelwaleed A. Hussien, Reyad A. Shawabkeh ∗ Department of Chemical Engineering, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia a r t i c l e i n f o Article history: Received 22 June 2012 Received in revised form 22 October 2012 Accepted 21 November 2012 Available online 7 December 2012 Keywords: Fly ash Adsorption Carbon dioxide Chemical treatment CO2 capturing a b s t r a c t Oil fly ash from power generation plants was activated with 30% NH 4 OH and used for selective adsorption of carbon dioxide from CO 2 /N 2 mixture. The treated samples were characterized for their surface area, morphology, crystalline phase, chemical composition and surface functional groups. Energy dispersive X-ray analysis showed an increase in the carbon contents from 45 to 73 wt% as a result of leaching out metal oxides. XRD proved that chemical activation of ash resulted in diminishing of major crystalline phases of zeolite, and other alumino-silicates leaving only quartz and mullite. BET analysis showed an increase in surface area from 59 to 318 m 2 /g after chemical activation and the pore volume increased from 0.0368 to 0.679 cm 3 /g. This increase in pore volume is supported by the results of SEM, where more micropores were opened with well-defined particle sizes and porous structure. The TGA of the treated fly ash showed stability at higher temperature as the weight loss decreased with increasing temperature. For treated ash, the FTIR displayed new peaks of amine functional group. The treated ash was used for the removal of CO 2 from CO 2 /N 2 mixture and the maximum adsorption/capturing capacity was found to be 240 mg/g. This capacity increases with increase in initial gas concentration, inlet flow rate and temperature suggesting the endothermic nature of the interaction between the gas molecules and the surface of the ash. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The combustion of coal and fossil fuel results in a by-product called fly ash which are normally collected by means of cyclones (mechanical devices) or electrostatic precipitators to control air pollution [1]. This material has no economical value and is one of the major waste materials in that required disposal. Approximately 50 million tons of coal combustion products were produced in 2010, about 43% of the total generated by coal burning power plants were recycled in a variety of beneficial uses [2]. However, large quanti- ties of fly ash are produced in United States and China with 32% and 40% utilization levels, respectively [3,4]. In the United States, more than 71 million tons of fly ash are produced annually in the coal power plants but only 45% is reused in different application [5]. They are used as fillers in polymer, cementitious materials, as a replacement of Portland cement, asphalt, stabilizing agent, and wastewater treatment [6–12]. Particular attention has been given to fly ash as an econom- ical adsorbent for its leachability of metals from waste water and removal of flue gases because of its readily availability and ∗ Corresponding author. E-mail address: rshawabk@kfupm.edu.sa (R.A. Shawabkeh). abundance, another advantage of using fly ash is its ability to eas- ily solidify after the pollutants are adsorbed [13] .The components of fly ash are basically alumina, silica, iron oxide and residual carbon [1], Toxic constituents include arsenic, beryllium, boron, cadmium, chromium, chromium VI, cobalt, lead, manganese, mer- cury, molybdenum, selenium, strontium, thallium, and vanadium, along with dioxins and PAH compounds [14] but these constituents vary according to the coal type used and the degree of combustion [15]. Shawabkeh et al. studied the enhancement of surface prop- erties of oil fly ash (OFA) by chemical treatment [16]. Bada et al. investigated the property of fly ash when subjected to chemical and heat treatment for adsorption purposes. The Chemical treatment was performed using hydrochloric acid solution and compared with untreated heat treated samples. The analysis revealed that the chemically treated fly ash has a higher specific surface area as a result of corrosion of the outer layer of the fly ash to ash which dis- integrates its stable glassy layer [17]. Kishore et al. studied the effect of surface treatment of fly ash by performing adhesion experiments in order to study the behavior of polymer composite [18]. Gray et al. reported the amination of fly ash carbons possessing alcoholic and carboxylic acid moieties on the surface with chloropropylamine. They evaluated the oxidation of the carbon surface with KOH in an effort to create more sites for amine anchoring. The surfaces of carbons are easily modified by functionalization with amines 0169-4332/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apsusc.2012.11.109