Preparation of mesoporous and macroporous materials from rubber of tyre wastes

From residual rubber (RR) separated from tyre wastes, adsorbent materials were prepared by applying thermal, chemical and combined (thermal and chemical or vice versa) methods. In the preparation of samples, RR was heated at 200-900 degreesC for 2 h in N-2 atmosphere. The material was also contacted with H2SO4, HNO3, and H2SO4/HNO3 solutions for 24 h. Finally, RR was first heated at 400 degreesC for 2 h in N-2 and the resultant product was then treated chemically with an H2SO4/HNO3 solution for 24 h, or vice versa. Both RR and the products derived from it were characterised texturally by gas adsorption (N-2, 77 K), mercury porosimetry, and helium and mercury density measurements. Usually, the yield is lower for the heat treatments than for the single chemical treatments (e.g., the smallest yield values are 33.0 and 60.5 wt.%). For the combined treatments, as compared to the single treatments, the yield is higher. RR is a nonporous solid. The treatments of RR as a rule result in a great porosity development mainly in the mesopore and macropore ranges for the heat and chemical treatments, respectively. The presence of HNO3 in the acid solution used in the treatments of RR has proved to be an essential factor for the development of the porosity made up of large pores. When RR is subjected to combined treatments, the predominant effect on the porosity development is that of the treatment effected first. By successive heat and chemical treatments, a product containing the same volumes of mesopores and macropores is obtained. The micropore content is low for all products, but especially for those prepared chemically. (C) 2003 Elsevier Inc. All rights reserved.