A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Masters of Science, 2017 / The tailoring of zeolites surface properties using organic functionalising agents displaying higher binding affinity for metal ions is a widely explored approach for water treatment. In this study, amine functionalised zeolites and phosphate functionalised zeolites were separately synthesised from similar natural zeolite precursors using reflux methods. The surface composition and morphological elucidations were achieved by characterising the adsorbents using Fourier Transform Infra-red spectroscopy (FTIR), thermogravimetric analysis (TGA), Zeta potential, Point of zero charge (pHPZC), and the Brunauer, Emmett and Teller analysis (BET). In case study 5.1, the sorption mechanisms of the uranyl ion onto amine functionalised zeolites (AMZ), activated carbon (AC) and natural zeolite (NZ) were studied as function of various environmental batch parameters. There was effective adsorption when uranium existed as uranyl ions: UO22+ and UO2OH+. The data fitted numerous kinetic and isotherm models suggesting that the equilibrium mechanisms were characteristic of a combination of chemisorption and physisorption for these three adsorbents. The Dubinin-Radushkevich (DR) model did not fit the data and therefore the energy values derived from it were not used to predict the mechanisms involved. However, the thermodynamic evaluations of parameters ∆H, ΔG and ∆S° showed that equilibrium mechanisms were exothermically, randomly and spontaneously favoured for all adsorbents at temperatures ranging between 22 and 40oC. The adsorption capacity of 0.452 mg g-1 was achieved at pH 3 by 500 mg AC dosage using 20 mL volume of 10 mg L-1 uranyl ion solution after equilibrating for 6 h within the temperature ranges of 22 to 30oC. Under the same conditions of sorbent dosage of 500 mg, uranyl solution volume of 20 mL and 10 mg L-1 U(VI) solution concentration, the maximum adsorption capacity of 0.506 mg g-1 for NZ and 0.480 mg g-1 for AMZ were both achieved at pH 4 after equilibration time of 21 h and 6 h with the optimum temperature range of 22 to 30oC, respectively. The model results predict that intraparticle diffusion thorough pores decreased in the order AC ˃ NZ ˃ AMZ while estimating that chemisorption occurred in a reverse order. On the basis of the modelled data, it was deduced that amine functionalisation of natural zeolites improves their chemisorption capability for uranyl ion and can therefore be used as a cost efficient adsorbent for small-scale remediation of contaminated aquatic systems. In another case study 5.2, the surface properties of successfully prepared aminomethyl phosphonic acid functionalised natural zeolite (APZ) were compared to those of commercial silica polyamine composites (SPC) for uranium uptake in batch aqueous solutions. The FTIR spectrum revealed that (3-aminotrimethyl) phosphonic acid functional groups were successfully grafted onto natural zeolite. The TGA analysis showed that the APZ had higher thermal stability and fewer active sites compared to SPC. The optimum adsorption capacity (qe) of 49 mg g-1 and 44 mg g-1 uranium was achieved using 25 mg SPC and 100 mg APZ, respectively at pH 4, 25oC after 1 and 6 h equilibrating time. The data best fitted the pseudo second-order kinetic model and Freundlich isotherm model. The thermodynamic studies showed that adsorption occurred chemically and exothermically for both APZ and SPC. The overall selectivity order for APZ was; Na ˃ Mn ≥ U ˃ Ca ˃ Fe and for SPC was; Fe ˃ Mn ≥ Ca ˃ U˃ Na. The findings showed that phosphate- and amine-functionalised zeolite bind strongly to uranium compared to the unmodified natural zeolite and other conventional adsorbents such as activated carbon. Their selectivity for this element was commendable. With further improvements in the synthetic protocols e.g. by using microwave-based methods, it should be possible to obtain functionalised zeolite that has superior properties to SPC. / XL2017

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Agradecemos a compreensão. on 2016-04-14T19:49:13Z (GMT) / Submitted by MILENA RODRIGUES BONIOLO null (milenaboniolo@yahoo.com.br) on 2016-04-15T00:59:57Z No. of bitstreams: 1 REPOSITORIO_Boniolo.pdf: 2914406 bytes, checksum: 1b92b8a055ad1cfc71027ce20781089a (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-04-15T12:55:02Z (GMT) No. of bitstreams: 1 boniolo_mr_dr_rcla.pdf: 2914406 bytes, checksum: 1b92b8a055ad1cfc71027ce20781089a (MD5) / Made available in DSpace on 2016-04-15T12:55:02Z (GMT). No. of bitstreams: 1 boniolo_mr_dr_rcla.pdf: 2914406 bytes, checksum: 1b92b8a055ad1cfc71027ce20781089a (MD5) Previous issue date: 2016-02-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A escassez qualitativa e quantitativa de água associada aos impactos ambientais impostos por águas residuárias tem agravado o cenário da situação ambiental brasileira. Um setor que merece destaque é o de mineração de urânio visto que o Brasil é a sexta maior reserva mundial deste elemento e existe grande quantidade de rejeitos acumulados contendo íons metálicos, semimetálicos e radiotóxicos. A biossorção tem se mostrado eficiente no tratamento das águas residuárias com íons que mesmo em baixas concentrações são tóxicos. O objetivo deste trabalho foi avaliar a redução da concentração de urânio em soluções e em amostras de águas de drenagem ácida de minas da mina Osamu Utsumi das Indústrias Nucleares do Brasil por meio da biossorção. As biomassas escolhidas para uso como biosorvente foram cascas de banana, sementes de moringa e borra de café. Ensaios de decomposição térmica, porosimetria de adsorção de nitrogênio e microscopia eletrônica de varredura foram efetuados de modo a caracterizar fisicamente os biosorventes. As variáveis analisadas para os ensaios em batelada como tamanho e massa do biosorvente, temperatura do ensaio, tempo de contato, pH e concentração inicial da solução de urânio foram definidas com o planejamento fatorial de experimentos. A partir dos ensaios em batelada realizados, pôde-se observar que as biomassas com maior área superficial e menor volume de poros resultaram em maiores valores de eficiência de remoção, sendo a ordem crescente destes parâmetros: cascas de banana < borra de café < sementes de moringa. Dentre os biosorventes estudados as sementes de moringa apresentaram os maiores valores de eficiência de remoção, seguida pela borra de café e cascas de banana. Em soluções de 100 mg L-1 as eficiências de remoção das sementes de moringa e cascas de banana foram iguais a 0,7429 e 0,2483, respectivamente; em valores de concentração de 25 mg L-1 as borras de café apresentaram eficiência de remoção igual a 0,9358. Em amostras de efluente com concentrações de urânio na ordem de 5 mg L-1 , as sementes de moringa apresentaram-se como o biosorvente com melhor eficiência de remoção (~0,8) quando comparadas as cascas de banana (~0,5) e borra de café (~0,7). / The qualitative and quantitative water scarcity associated with environmental impacts posed by wastewater has worsened the brazilian environmental scenario. Uranium mining is a prominent sector in Brazil context, since this country owns the sixth biggest uranium reserve in the world and there is large amount of accumulated tailings containing metallic, semi-metallic and radiotoxic ions. In general, biosorption has shown significant efficiency on effluent treatment, removing ions which even in low concentrations present toxicity. This work aimed to reduce the concentration of uranium by using biosorption in both cases, lab scale solutions and acid mining drainage effluent samples from Osamu Utsumi mine, wich belongs to Usinas Nucleares do Brasil. The selected biomasses used as biosorvent were banana peels, moringa’s seeds and coffee waste. Thermal decomposition, nitrogen adsorption porosimetry and scanning electron microscopy were performed for physical characterization. The studied variables for the batch tests as size and mass of biosorvent, temperature of tests, contact time, pH and initial concentration of solutions of uranium were defined by using design of experiments. From the tests carried out it was observed that the biomasses with a higher surface area and smaller pore volume resulted in higher removal efficiency values, with an ascending order of these parameters: banana peels <coffee grounds <seed moringa. Among the studied biosorvents, moringa seeds showed the highest values of removal efficiency followed by the coffee waste and banana peel. Based on tests using uranium solutions of 100 mg L-1, the removal efficiency of moringa seeds and banana peel were 0,7429 and 0,2483, respectively; assuming concentration of 25 mg L-1 the coffee wastes has shown efficiency of removal of 0,9358. In effluent samples with uranium concentrations in the order of 5 mg L-1, the moringa seeds were presented as the biosorbent with better removal efficiency (~ 0.8) when compared to banana peels (~ 0.5) and coffee waste (~ 0.7).