The immobilisation of organic waste by geopolymerisation

Gokhale, Charlene (2001-12)

Thesis (MScEng)--University of Stellenbosch, 2001.

Thesis

ENGLISH ABSTRACT: In excess of24 x 106 tons (1997, Eskom) of coal-derived fly ash is produced annually in South Africa for the production of electric power. A large quantity of this ash is disposed 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 be converted into zeolites to obtain industrial products with applicability In environmental management. Geopolymerisation has emerged during the last few years 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. Immobilisation of phenols by adsorption on zeolites and encapsulation in a geopolymer appears to be a promising solution to this problem. This thesis reports a technique for the production of a low-silica sodium zeolitic material from fly ash (zeolite NaP1), and its application for the stabilisation of phenols by adsorption and subsequent encapsulation in a geopolymer matrix. A commercial zeolite, clinoptilolite was also utilised as an adsorbent. Due to their uniform pore sizes and large surface areas, zeoli tic materials are suitable for ion exchange and adsorption of certain organic substances. Adsorption data show that the commercial zeolite, clinoptilolite was an effective adsorbent for organics. Adsorption data showed that between 51.2ppm and 74.3ppm of chlorophenol or between 15.4ppm and 32.5ppm of phenol could be adsorbed. Physical encapsulation of the coated zeolite loaded with organic within a geopolyrneric matrix increased the compressive strength of the matrix from 28.80 kN to 40.79 kN. Leaching data for the various geopolymer matrices with encapsulated and loaded zeolites show no organics being leached from the system at a detection level of 2ppm. According to the SABS these would have been acceptable organic concentrations within a waste water stream. In utilising waste materials (fly ash and organic waste) and their reactive properties, it is now possible to create various geopolyrners that are not only strong enough to be used as constructionlbuilding materials, but are also effective immobilisation systems for organic waste containment.

AFRIKAANSE OPSOMMING: Meer as 24 x 106 tons (1997, Eskom) vlieg-as word jaarliks deur die verbranding van steenkool vir die produksie van elektrisiteit geproduseer. Die as, wat tans in groot hoeveelhede as soliede afval in vaste-afval stortingsterreine gestort word, word gesien as 'n groeiende omgewingsprobleem. 'n Tekort aan geskikte stortingsterreine maak die ontwikkeling van nuwe gebruike vir die vlieg-as dringend nodsaaklik. Geopolimerisasie van vlieg-as materiale, 'n proses wat die laaste paar jaar ontwikkel is, blyk 'n potensiele oplossing te wees vir sommige afval stabilisering en solidifikasie toepassings. Daar is bewyse dat fenoliese verbindings, selfs op 'n dele per miljoene (dpm) vlak, toksies is vir grondorganismes. Verskeie van die komponente wat deur die Amerikaanse Omgewingsbeskermingsagentskap (US EPA) as prioritats kontaminants geklassifiseer is, is ondermeer fenole. Die huidige werk ondersoek die adsorbsie van fenol op zeoliet NaPI en clinoptiloliet, gevolg deur fisiese omsluiting deur geopolimerisasie. Verskeie outeurs het onlangs verwys na die omsetting van verskeie verbrandings vlieg-asse na zeoliete om bruikbare industriele produkte (vir gebruik in die omgewingsveld) te vorm. Die tesis rapporteer 'n metode vir die produksie van 'n iae silika natrium zeolitiese material (zeoliet NaP!) uit vlieg-as en die gebruik daarvan in die stabilisering van fenole. 'n Kommersieel beskikbare zeoliet, clinoptiioliet, is ook gebruik as adsorbent. Uniforme porie groottes en hoe oppervlak areas maak zeolitiese materiale geskik vir ioonuitruiling, asook die adsorbsie van verskeie orgamese verbindings. Deur die fisiese omsluiting van die zeolitiese materiaal binne 'n geopolimeer matriks, kan materiale met beduidend hoe druksterktes, geproduseer word. Adsorbsie data het getoon data die kornmersiele zeoliet, klinoptilotiet, 'n effektiewe adsorbent vir organiese stowwe is. Adsorbsie waardes het gewissel tussen 51.2dpm tot 74.3dpm vir chlorofenol en 15.4dpm tot 32.5dpm vir fenol. Fisiese enkalsulering van die bebandelde zeoliet (coated fzeo) binne 'n geopolimeer matriks het die saamdrukbaarheidsterkte van die betrokke matriks verhoog van 28.80 kN to 40.79 kN. Logingsdata verkry vir die onderskeie geopolimeer matrikse het getoon dat geen van die organiese stowwe uit die matrikse vrygestel word nie. Indien die organiese stowwe wel vrygestel sou word, sou die waterfase konsentrasie onder 2 dpm, binne die aanvaarbare spesifikasie vir uitvloeisels volgens die SABS standard, gewees het. Verskeie geopolimere, wat nie slegs sterk genoeg is om as konstruksie materiale te dien nie, maar addisioneel effektief as immobilisasie medium dien, kan dus uit die reaktiewe eienskappe van afval materiale (vlieg-as en organiese afval) vervaardig word.

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