Research article Preparation, characterization and application of polystyrene based activated carbons for Ni(II) removal from aqueous solution L. Gonsalvesh a, ⁎, S.P. Marinov a , G. Gryglewicz b , R.Carleer c , J.Yperman c a Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria b Department of Polymer and Carbonaceous Materials, Faculty of Chemistry, Wrocław University of Technology, Gdańska 7/9, 50-344 Wrocław, Poland c Research Group of Applied and Analytical Chemistry, CMK, Hasselt University, Agoralaan — gebouw D, B-3590 Diepenbeek, Belgium abstract article info Article history: Received 9 September 2015 Received in revised form 21 March 2016 Accepted 23 March 2016 Available online xxxx The production of activated carbon from polystyrene waste is tested in order to limit its negative environmental impact through conversion to value added products. For this purpose modification of the precursor, slow pyrol- ysis and subsequent activations, i.e. high temperature steam activation and low temperature air oxidation, are applied. The physical/chemical properties as well as adsorption capacities of obtained activated carbons (ACs) towards Ni(II) removal in aqueous solutions are explored. Steam activated carbon S-ACMPS performs superior in Ni(II) removal at applied circumstances. Ni(II) adsorption by this AC has been investigated using different process parameters and occurs through cation exchange mech- anism optimal at pH range of initial solution of 4–8. Several reaction based kinetic models, i.e. pseudo-first, pseudo-second and Elovich models, and intra-particle diffusion model, are applied on experimental data. The adsorption kinetics of Ni(II) is best approximated by a pseudo second-order model. The equilibrium adsorption data best fits the Langmuir adsorption isotherm. Calculated maximum adsorption capacity for S-ACMPS is 40.8 mg g -1 . © 2016 Elsevier B.V. All rights reserved. Keywords: Polystyrene waste Activated carbon Nickel Adsorption Kinetics 1. Introduction Activated carbons (ACs) are highly effective adsorbents with wide range of applications that are generally produced through pyrolysis and subsequent physical or chemical activation of different materials with high carbon and low inorganic content. However, due to the high production cost, ACs tend to be more expensive than other adsorbents and their widespread application is somewhat limited. This instigated a growing interest into production of low cost activated carbons through the usage of low-cost raw materials that are economically at- tractive and at the same time show similar or even better performance than the conventional ones. Therefore, cheaper and common precursors as lignocellulosic biomasses have been widely tested for ACs prepara- tion [1]. Recently, a large number of studies are dealing with the preparation of ACs from various polymeric wastes as well [2–4]. These materials are successfully used for the production of high yield of ACs characterized by low ash content, high adsorption capacity and consid- erable mechanical strength. Thermoplastic polymers, i.e. polypropylene, polyethylene, polyvinylchloride, polystyrene, polyamide, etc., are the major constitu- ents of municipal solid waste. More than 25 million tons of plastic waste is annually generated in the region of European countries [5]. This cre- ates significant ecological concern since the degradation of plastic waste on a landfill is an extremely slow process, ongoing for centuries. Consequently, the use of these waste materials for higher-value prod- ucts preparation such as fuels, carbon nanotubes, and porous carbons is very attractive to decrease the negative impact on the environment and the costs of waste disposal or treatment. Polystyrene (PS) is a petroleum-based plastic which is available as a solid or foamed. Several papers have been published in recent years on ACs preparation from “pure” PS wastes or their blends with an addi- tional carbon source [6–9] as well as from polystyrene-based macroreticular ion-exchange resin spheres (copolymer of polystyrene and divinylbenzene) [10–11]. Although these studies focus on physical and chemical characterization of obtained ACs, information concerning ACs adsorption efficiency towards heavy metals removal is rather scarce. Water polluted by heavy metals can be problematic due to their stability, mobility and toxicity. A number of technologies have been used to remove heavy metals, i.e. chemical precipitation, ion exchange, membrane separation, flotation, electrocoagulation, etc. from wastewa- ters. However, most of them suffer from disadvantages such as incom- plete removal, expensive equipment/reagent usage, production of toxic sludge requiring disposal, and long treatment time. [12]. An alter- native and attractive choice for heavy metal removal from aqueous so- lutions appears to be their adsorption since it is considered as a simple, Fuel Processing Technology 149 (2016) 75–85 ⁎ Corresponding author at: Central Scientific Research Laboratory, Assen Zlatarov University, Yakimov Str. 1, Burgas, Bulgaria. E-mail address: lenia_gonsalvesh@abv.bg (L. Gonsalvesh). http://dx.doi.org/10.1016/j.fuproc.2016.03.024 0378-3820/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Fuel Processing Technology journal homepage: www.elsevier.com/locate/fuproc