The immobilisation of organic waste by geopolymerisation

[摘要] ENGLISH ABSTRACT:In excess of24 x 106 tons (1997, Eskom) of coal-derived fly ash is produced annuallyin South Africa for the production of electric power. A large quantity of this ash isdisposed of as a solid waste in landfills, thus posing a serious environmental problem.Due to the shortage of landfill sites, new ways of utilising fly ash are needed.Recently several authors have shown that various combustion fly ashes can beconverted into zeolites to obtain industrial products with applicability Inenvironmental management. Geopolymerisation has emerged during the last fewyears as a possible solution to some waste stabilisation and solidification problems.Phenolic compounds have been shown to be toxic to soil microorganisms at the partsper-million level. Indeed several of the organic compounds classified by the U.S.Environmental Protection Agency as priority pollutants, are phenols. Immobilisationof phenols by adsorption on zeolites and encapsulation in a geopolymer appears to bea promising solution to this problem.This thesis reports a technique for the production of a low-silica sodium zeoliticmaterial from fly ash (zeolite NaP1), and its application for the stabilisation ofphenols by adsorption and subsequent encapsulation in a geopolymer matrix. Acommercial zeolite, clinoptilolite was also utilised as an adsorbent. Due to theiruniform pore sizes and large surface areas, zeoli tic materials are suitable for ionexchange and adsorption of certain organic substances. Adsorption data show that thecommercial zeolite, clinoptilolite was an effective adsorbent for organics. Adsorptiondata showed that between 51.2ppm and 74.3ppm of chlorophenol or between 15.4ppmand 32.5ppm of phenol could be adsorbed. Physical encapsulation of the coatedzeolite loaded with organic within a geopolyrneric matrix increased the compressivestrength of the matrix from 28.80 kN to 40.79 kN. Leaching data for the variousgeopolymer matrices with encapsulated and loaded zeolites show no organics beingleached from the system at a detection level of 2ppm. According to the SABS thesewould have been acceptable organic concentrations within a waste water stream.In utilising waste materials (fly ash and organic waste) and their reactive properties, itis now possible to create various geopolyrners that are not only strong enough to beused as constructionlbuilding materials, but are also effective immobilisation systemsfor organic waste containment.

[发布机构] Stellenbosch University