High value activated carbons from waste polystyrene foams

Abstract

Activated carbons (AC) with excellent textural properties have been obtained for the first time from waste polystyrene foam (PF), without any previous treatment, following a simple and conventional two-step procedure (formation of char followed by chemical activation). Even considering that the PF is not a graphitizable material, the best AC produced from this precursor has a very high BET surface area larger than 2700 m 2 g-1 and a pore volume of 1.2 cm 2 g-1 , with a significant contribution of small mesopores. As a consequence, this AC reveals a surprising capacity to adsorption of relatively large molecules and a high specific capacitance when applied as a supercapacitor electrode. The maximum amount of adsorbed methylene blue obtained by batch equilibrium experiments are greater than 1g g-1. In the context of the technical difficulties and low economic return of the reuse and recycling of waste PF, this work offers a strategic destination for this environmentally unfriendly residue.

Mechanism and Stability of a Redox Supercapacitor Based on Methylene Blue: Effects of Degradation of the Redox Shuttle

“…The increase in the activation temperature drastically reduced the resistivity of the ACs, it ranging from 1094 Ω cm (AC 600 ) to only 6 Ω cm (AC 800 ). 23 All this results in a significant variation in the amount of MB adsorbed, which increases from 270 mg g -1 for AC 600, to 536 mg g -1 for AC 700 and to1042 mg g -1 for AC 800 .…”

“…[28][29][30] A macroscopic example that reflects the intensity of the interactions was showed with the high adsorption capacity in the AC 800 , reaching 1042 mg g -1 . 23 Yan et al showed that the interaction between MB and carbon nanotubes is so stable that the composite is preserved even after filtering, drying and its ultrasound redispersion in water. 31 Another interesting example of the complexity of these interactions can be seen in the work of Barreda et al, which has experimentally shown that activated carbons are able to reorient their graphite micro-domains after the adsorption of this cationic dye.…”

“…MB was pre-adsorbed on CA samples prior to the electrode preparation as described previously. 23 and an ion trap analyzer (LCQ-Fleet, Thermo-Scientific). To obtain the spectra, the was pumped in using a syringe (Hamilton 500 μL) at a flow rate of 30 μL min -1 .…”

“…Galvanostatic charge/discharge profiles at 0.20 A g -1 for (a) the redox-SC based on MB, (b) pure EDLC and (c) a second redox-SC as model based on hydroquinone as redox shuttle and CNT as electrodes.An examination of the potential profiles inFigure 2bshows that the curves for pure EDCL are classical and characteristics of a symmetrical SC, with one single storage mechanism (an electric double layer) and with both electrodes having the same charge storage capacity 23. The model system presented inFigure 2cexhibits the behavior of a typical hybrid system, where the positive electrode is working at a constant potential based on the hydroquinone's formal potential (faradaic mechanism), while the negative electrode presents the triangular behavior typical of purely capacitive storage 25.…”

A Porous Carbon with Excellent Gas Storage Properties from Waste Polystyrene

“…Cooper et al studied the crosslinking reaction of various polystyrenes synthesized in situ with different molecular weights; Fu et al [32] reported the same reaction on expanded PS, using 1,2-dichloroethane as the crosslinking agent [33]. Very recently, waste polystyrene foam was used to prepare cross-linked polymers through a Friedel-Crafts reaction with acetone and aluminum chloride in the presence of silica nanoparticles, followed by calcination to obtain a porous carbon [34]; another porous carbon was prepared from PS by pyrolysis and chemical activation with KOH [35]. Then, HCP-PS was chemically and thermally activated, producing a highly porous carbonaceous material, named KPS-1.…”