Production of active carbons from waste tyres––a review Edward L.K. Mui, Danny C.K. Ko, Gordon McKay * Department of Chemical Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong Received 22 September 2003; accepted 26 June 2004 Abstract A review of the production of activated carbons from waste tyres is presented. The effects of various process parameter ticularly,temperature and heating rate, on the pyrolysis stage are reviewed. The influence of activating conditions, physical and chemical, nature of the activation chemicals, on the active carbon properties are discussed. Under certain process conditio active carbons with BET surface areas over 1000 m 2 /g have been produced with extensive micropore volumes, over 40% of the tot pore volume. A review is carried out of the reaction kinetic modeling applied to the pyrolysis of tyres and the chemical activation of ty models cover one step and two step pyrolysis models, plus more recent models which are based on the actual chemical co such as natural rubber, SBR and other additives. 2004 Elsevier Ltd. All rights reserved. Keywords: A. Activated carbons; B. Activation, Pyrolysis; C. Modeling; D. Reaction kinetics 1. Introduction The disposal of tyres represents a major environmen- tal issue throughout the world, since the same properties that make them desirable as tyres, most notably durabil- ity, also make their disposal and reprocessing difficult, they are almost immune to biological degradation. The EU, the USA and Japan together were responsible for the disposal of a totalof 5 million tones of scrap tyres per year [1]. The major aspects of tyre problems are listed as fol- lows: Tyres stockpiles provide breeding ground for mosqui- toes and vermin, this in turn, causing serious disease and affecting human health. Fire hazardsin large stockpilesthat could conse- quently cause uncontrollable burning and air pollu- tion. The current‘‘conservation of naturalresource con- cept’’, i.e. the reuse (retread) first, then reuse of rub- ber prior disposal, does notaccommodate the ever increased dumping of tyres. Due to the high cost of legal disposal for tyres, illegal dumping may increase. Disposalof tyres is becoming more expensive, while this trend is likely to continue as landfill space be- comes more scarce. Tyres take up landfill space. The production of pyro-oil from tyre pyrolysis as a fuel source hasgenerated considerable interest [1–3]. However,most research emphasis has been focused on the identification of the pyro-oil components [3–8]. Dur- ing the past10–15 years, severalfundamental studies have reported that carefully controlled tyre pyrolysis 0008-6223/$ - see front matter 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbon.2004.06.023 * Corresponding author. Tel.: +852 2358 7133; fax: +852 2358 0054. E-mail address: kemckayg@ust.hk (G. McKay). Carbon 42 (2004) 2789–2805 www.elsevier.com/locate/carbon