Contents lists available at ScienceDirect Environmental Research journal homepage: www.elsevier.com/locate/envres Short communication Simultaneous valorization of polyvinyl chloride and eggshell wastes by a semi-industrial mechanochemical approach Matej Baláž a, ⁎ , Zdenka Bujňáková a , Marcela Achimovičová a,b , Matej Tešinský a , Peter Baláž a a Department of Mechanochemistry, Institute of Geotechnics, Slovak Academy of Sciences, Watsonova 45, 04001 Košice, Slovakia b Institute of Mineral and Waste Processing, Waste Disposal and Geomechanics, University of Technology Clausthal, Walther-Nernst-Strasse 9, 38678 Clausthal-Zellerfeld, Germany ARTICLE INFO Keywords: Waste valorization Eggshell PVC Mechanochemistry ABSTRACT A semi-industrial approach for simultaneous treatment of eggshell and industrial polyvinyl chloride waste uti- lizing tools of ball milling is reported therein. On a hundred-gram scale, it is possible to transfer more than 55% of chlorine present in the polyvinyl chloride representing an environmental burden, into harmless soluble form. On a laboratory scale, a complete dechlorination was achieved. The ratio of eggshell-to-polyvinyl chloride plays a significant role for the effective dechlorination and the kinetics of semi-industrial process follows zero-order kinetics with the rate constant 1.23 × 10 −5 s −1 . Chlorine is mainly in the form of calcium chloride. This study is an example of efficient simultaneous valorization of two waste materials on a semi-industrial scale, as the products can be utilized again. 1. Introduction Polyvinyl chloride (PVC) belongs into the group of halogenated waste and its further treatment represents an environmental problem (Bidoki and Wittlinger, 2010), as it cannot be combusted in a common manner due to the production of toxic dioxins during the process (Braun, 2002; Liu et al., 2012). Moreover, also HCl is produced, which can cause corrosion (Slapak et al., 1999; Starnes, 2012). In addition, the disposal of this material can contaminate groundwater (Poerschmann et al., 2015). This can be resolved by the PVC dechlorination. Many methods have been applied for this issue until now, as can be traced down from the review papers on this topic (Keane, 2007; Moulay, 2010; Yu et al., 2016). Mechanochemistry has an inevitable place among them (Cagnetta et al., 2016b, 2018; Shen et al., 2016). PVC was successfully mechanochemically dechlorinated using various compounds, mainly oxides and hydroxides (Inoue et al., 2006, 2004, 2005; Kameda et al., 2008; Mio et al., 2002; Saeki et al., 2001; Tongamp et al., 2006, 2009b; Zhang et al., 2000), however, also LiCoO 2 and zinc metal were used (Saeki et al., 2004; Xiao et al., 2008). From literature survey it is clear that calcium-based materials are very pop- ular, particularly calcium oxide, but also calcium sulfates (Tongamp et al., 2008a) or calcium carbonate was used. CaCO 3 is of particular interest, as it is the main component of natural waste materials like oyster shells or eggshells, which were also successfully used for me- chanochemical dechlorination in the past (Baláž et al., 2014, 2013; Tongamp et al., 2008b). The latter material has various applications itself (Cordeiro and Hincke, 2011; Guru and Dash, 2014; Laca et al., 2017; Mittal et al., 2016; Oliveira et al., 2013) and ball milling is an effective tool to fur- ther broaden its application spectrum (M. Baláž, 2018). As already mentioned, it was found to be also an effective dechlorination PVC agent. The principle lies in the transformation of insoluble chlorine from PVC into soluble form by reaction with calcium in CaCO 3 and forming CaCl 2 , as proposed by Tongamp et al. 2008b (Eq. (1)). PVC + CaCO 3 → [-CH=CH-] + CO 2 +H 2 O + CaCl 2 (1) All papers on mechanochemical dechlorination of PVC published until now deal with the laboratory-scale experiments and vast majority of them utilized PVC compound as a model (real waste was used only in (Baláž et al., 2014)). In the present study, the possibility to perform dechlorination of industrial PVC waste using eggshell in the up-scaled manner (hundreds of grams) is presented, which is 10–100 times larger amount in comparison with the majority of laboratory-scale experi- ments. As the experiments are performed in a satellite attached to large mill, simulating the process on even larger scale, the amount of treated material can hypothetically be 50 kg in one batch. It is a great example of using the ball milling process to mutually convert two waste mate- rials into valuable ones and simultaneously decreasing the environ- mental pollution. https://doi.org/10.1016/j.envres.2018.12.005 Received 29 September 2018; Received in revised form 26 November 2018; Accepted 5 December 2018 ⁎ Corresponding author. E-mail address: balazm@saske.sk (M. Baláž). Environmental Research 170 (2019) 332–336 Available online 08 December 2018 0013-9351/ © 2018 Elsevier Inc. All rights reserved. T