Potassic zeolites from Brazilian coal ash for use as a fertilizer in agriculture Camila Gomes Flores a,⇑ , Helena Schneider a , Nilson Romeu Marcilio a , Lizete Ferret b , João Carlos Pinto Oliveira c a Department of Chemical Engineering, Federal University of Rio Grande do Sul – UFRGS, Rua Luiz Englert, s/n° - 90.040-040, Porto Alegre, RS, Brazil b Foundation of Science and Technology – CIENTEC, Rua Washington Luiz, 675, CEP 90.010-460 Porto Alegre, RS, Brazil c Brazilian Agricultural Research Corporation – Embrapa Pecuária Sul, Rodovia BR-153, km 632,9 Vila Industrial, Zona Rural, CEO 96.401-970 Bagé, RS, Brazil article info Article history: Received 14 February 2017 Revised 24 July 2017 Accepted 22 August 2017 Available online xxxx Keywords: Potassic zeolites Coal ash Fertilizer Agriculture abstract Brazilian coal has an ash content ranging from 30 to 50% by weight. Consequently, its use in coal-fired thermoelectric for power production generates a lot of waste. The construction sector is the largest con- sumer of coal ash, but it cannot absorb the entire amount generated. Thus, other applications for coal ash should be studied in aim to optimize the use of this industrial waste. This research had as focus to syn- thesize potassic zeolite from of the coal ash into on potassium fertilizer for the grown wheat plant. In this work, it was used a subbituminous coal from Mina do Leão (RS, Brazil) presenting 48.7% ash content on a dry basis. Concerning the synthesis of potassic zeolite, it was adopted the conventional method of hydrothermal treatment with potassium hydroxide. A schedule of experiments was conducted in order to define the optimum condition of zeolite synthesis that was then used an alkaline solution of 5 M KOH with a reaction time of 24 h at 150 °C. According to this procedure, it was obtained a zeolite with a single crystalline phase, identified through X-ray diffraction as Merlinoite. Subsequently, it was per- formed a set of tests using potassic zeolite as a fertilizer for plants in a greenhouse. The synthesized potassic zeolite showed a good potential for its use as fertilizer in agriculture. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction In terms of volume, the thermoelectric plants for energy pro- duction, generate a significant amount of solid waste known as ash from the burning of coal (Kalhreuth and Levandowski, 2009). According to the Thermal Generation of Electric Power Company, CGTEE (2010), 1.0 kg of raw material produces 1 kWh of energy and 0.5 kg of ash in the case of coal from the Mine of Candiota (Brazil, RS). This coproduct is formed by unburned particles and non-combustible material present in the coal (Pozzobon, 1999). The main applications of ashes are: manufacture and incorpora- tion into the cement and ceramics, stabilizing soils, landscape recultivation, geopolymers production, fertilizers materials, among others (Ahmaruzzaman, 2010; Rhim et al., 2006; Egger et al., 2009; Lee et al., 2011; Bessa et al., 2015; Berekaa, 2015; Li, 2003; Bernardi et al., 2010a; Bernardi et al., 2010b; Li et al., 2014; Bernardi et al., 2015). However, this still occurs on a small scale when compared to the amount of ash generated (Derkowski et al., 2006). Therefore, there is the need to search for more ways to take advantage and add value to this coproduct. In this context, a promising application for ash is its conversion into zeolitic material by hydrothermal treatment with potassium or sodium hydroxide (Henmi, 1987; Querol et al., 1997a, 1997b; Poole et al., 2000; Rayalu et al., 2006; Kolay et al., 2001; Murayama et al., 2002; Fukasawa et al., 2017a). Zeolites are miner- als consisting of aluminum, silicon and hydrous alkali or alkaline earth metals (typically Na, K, Mg and Ca) (Fukasawa et al., 2017b; Lee et al., 2017). Since the coal ash is composed in average of 85% alumina and silica (Fukasawa et al., 2017b; Missengue et al., 2017), this solid waste is a good precursor for zeolite synthesis. Zeolite has microporous structure organized in three- dimensional crystal lattices (Böer, 2013). This gives it great power of adsorption and ion exchange capacity (Luz, 1994), features that are suitable for a wide range of processes like catalysts supports. Therefore, transforming coal fly ash into zeolite adds value to this coproduct. Using ash as raw material minimizes the impacts to the environment and eliminates, in part, the volume of ash for disposal (Holler and Wirsging, 1985). The synthesis of zeolites from coal ash is directly influenced by the following parameters: type and composition of the ash, type http://dx.doi.org/10.1016/j.wasman.2017.08.039 0956-053X/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: camilaflores31@hotmail.com (C.G. Flores). Waste Management xxx (2017) xxx–xxx Contents lists available at ScienceDirect Waste Management journal homepage: www.elsevier.com/locate/wasman Please cite this article in press as: Flores, C.G., et al. Potassic zeolites from Brazilian coal ash for use as a fertilizer in agriculture. Waste Management (2017), http://dx.doi.org/10.1016/j.wasman.2017.08.039