Developing a zero liquid discharge process for zeolitization of coal ﬂy ash to synthetic NaP zeolite Jamshid Behin a , Syed Salman Bukhari b , Hossein Kazemian b,c,⇑ , Sohrab Rohani b,⇑ a Department of Chemical Engineering, Razi University, Kermanshah, Iran b Department of Chemical and Biochemical Engineering, University of Western Ontario, London, Ontario, Canada c College of Science and Management, University of Northern British Columbia, Prince George, BC, Canada highlights  Coal ﬂy ash zeolitized using a zero liquid discharge technique.  Zeolitization of CFA is techno-economically feasible at larger scales.  Elimination of liquid discharge will obviate the need to comply with environmental regulations.  Zeolitic product can be used in eco-friendly technologies to immobilize different pollutants. article info Article history: Received 7 November 2015 Received in revised form 14 December 2015 Accepted 29 December 2015 Available online 6 January 2016 Keywords: Coal ﬂy ash Leachate Trace elements Zeolite Zero discharge abstract Successful conversion of coal ﬂy ash (CFA) to synthetic NaP zeolite with zero liquid discharge is reported in this article. The process eliminates the need for large amounts of water and the need for a huge wastewater treatment unit. The need for water, as a make-up stream, is only to compensate water losses during sampling and drying. Savings associated with minimizing make-up water and eliminating wastewater treatment unit can be substantial. Water and sodium hydroxide consumption is reduced by 90% and 50%, respectively. Furthermore, quality of the NaP zeolite (CFA-ZP) obtained is comparable to conventional method. The zeolitized product shows high crystallinity and leach resistance toward heavy metal and trace element content of the product. Leaching tests revealed that the concentrations of most of trace elements in leachate of CFA-ZP were less than threshold limit for landﬁll leachate and wastewater efﬂuent for discharging into river and surface water. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction CFA is a by-product of coal ﬁred power plants, which is consid- ered as a solid waste [1–3]. The recycling of CFA to be used for other applications is rather low [4,5]. Currently less than 50% of worldwide produced CFA is being re-used for different applications [6]. Coal ﬂy ash is mainly used as a construction material, in which majority of the CFA utilization is in concrete production as poz- zolan. More than 50% of the world production of CFA is disposed into landﬁll ponds at signiﬁcant cost for the coal-ﬁred power plants. Furthermore, there have been accidents that landﬁlls lea- chates found their ways to the environment causing millions of dollars’ worth of damage [7]. It seems that production rate of CFA is much faster than the development of cement production; which means larger volume of CFA are expected to accumulate even more in the future that increases the risk of environmental disasters as a result releasing of toxic compounds to the water bod- ies and soil [8]. CFA contains trace amounts of toxic compounds and heavy met- als such as arsenic, beryllium, cadmium, barium, chromium, cop- per, lead, molybdenum, nickel, selenium and vanadium, some of which are known to be detrimental to the human health [9]. Lea- chate of the CFA landﬁlls may contaminate ground/surface water leading some of the toxic elements entering into the food chain affecting human health. Safe and efﬁcient disposal of CFA is a glo- bal issue because of its massive production rate and its harmful effects on the environment [1,10,11]. It has been found that the surface layer of coal ﬂy ash particles of micrometers in diameter contain a signiﬁcant amount of readily leachable material, which are deposited during cooling after combustion [5,12,13]. http://dx.doi.org/10.1016/j.fuel.2015.12.073 0016-2361/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors at: Department of Chemical and Biochemical Engineer- ing, University of Western Ontario, London, Ontario, Canada (H. Kazemian and S. Rohani). E-mail addresses: hossein.kazemian@unbc.ca (H. Kazemian), srohani@uwo.ca (S. Rohani). Fuel 171 (2016) 195–202 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel