The production of silver-loaded zeolites either by ion exchange method or by isomorphous substitution of silver ions into zeolites frameworks and their antimicrobial activity is presented. Silver-loaded zeolites produced by ion-exchange in this work include silver-exchanged zeolite X, silver-exchanged zeolite A and silver-exchanged high-alumina Phillipsite. Silver-doped Analcime was produced by isomorphous substitution of silver ions into the Analcime framework. The silver-loaded zeolites were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, particle size analysis and Fourier transformed infrared (FTIR) spectroscopy. Studies showed that the amount of silver ions loaded into the zeolites frameworks differed for each zeolite. XRD analysis showed little or no changes in the phase purity of all zeolites before and after ion exchange or before and after substitution of silver ions. SEM analysis and particle size analysis showed that the morphology of each zeolite particles was closely related before and after ion exchanged or before and after substitution of silver ions. The antimicrobial activity of these silver-loaded zeolites was investigated by exposing Escherichia coli K12W-T, Staphylococcus aureus NCIMB6571 and Pseudomonas aeruginosa NCIMB8295 suspended in tryptone soya broth (TSB) to the silver-loaded zeolites. The first stage of the investigation involved the exposure of the strains to silver-loaded zeolites in TSB for a duration of 24 hours at different concentration of silver-loaded zeolites. The second stage involved the exposure of the strains to silver-loaded zeolites in TSB over a period of two hours. The persistency of antimicrobial activity of silver-loaded zeolites was investigated by retrieving each silver-loaded zeolite from the first exposure cultures, washed copiously with de-ionised water and adding to fresh bacterial suspensions. To understand the mode of antimicrobial activity of the silver-loaded zeolites, the uptake of silver ions by the strains, composition of fatty acid, as well as the DNA content of Escherichia coli K12W-T was studied. The results obtained showed silver ions appeared to elute from the zeolites frameworks into the TSB in anomalous trend. All three microorganisms were completely inhibited within one hour with the silver-loaded zeolites retaining their antimicrobial activity. The release of silver ions from the zeolites frameworks followed first-order kinetics with varying rate constants and half-lives. The fatty acid composition of all strains as well as the DNA content of Escherichia coli K12W-T were affected by the action of silver ions.

Made available in DSpace on 2016-12-08T15:50:02Z (GMT). No. of bitstreams: 1 PGMS13DA015.pdf: 947168 bytes, checksum: 441cf02feb1ab108ff82cb196578a985 (MD5) Previous issue date: 2013-03-20 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Chemical modifications in the soil near fertilizer granules affect plant nutrient availability and, thus, knowing them may help to select the Best management practices for soil fertilization. This study comprised three experiments with the aim of: a- to evaluate the soil chemical composition around granules of calcium or ammonium phosphates when appled together with KCl as well as nutrient mobility in the soil; b- to quantify nutrient concentration in both soil and solution phases and soil solution P and K activity in the adjacencies of phosphate and potassium fertilizers; c- to evaluate nutrient uptake from maize seedlings after localized addition of phosphate fertilizers in the soil. It was used two acid soils, and treatments varied according to each experiment: in the first two it was compared phosphate sources in presence of KCl and liming; in the third, it was quantified nutrient uptake by maize plants as affected by phosphates, in a greenhouse. Rates of P2O5 e K2O were 100 mg kg-1in the first study; 700 and 1236 mg kg-1 for each soil, respectively, in the second experiment; and 200 mg/pot in the last study. The high doses were applied in order to simulate the concentrations in the near fertilizer granules. Near fertilizer granules of the mineral phosphate, the chemical composition of the soil is affected by different phosphorus sources, where the TSP proves more effective than DAP in the release of P. Localized application of phosphate fertilizers increases the movement of nutrients in the soil in which the phosphorus mobilization occurs up to four centimeters. The extraction method overestimates Mehlich 1 P values when applied to the soil TSP. DAP increases the concentration of HPO4- in soil solution. The MAP is shown to be an efficient source of P in the release and uptake by plants / As alterações químicas no solo ao redor dos grânulos de fertilizantes afetam a disponibilidade de nutrientes às plantas e o conhecimento das mesmas pode indicar as práticas e as fontes mais eficientes de fertilização do solo. Neste contexto, este estudo foi dividido em três experimentos. O primeiro experimento teve por objetivo avaliar a composição química do solo ao redor de grânulos de fosfatos de amônio ou de cálcio, aplicados juntamente com cloreto de potássio (KCl), e a mobilidade dos nutrientes por eles adicionados. O objetivo do segundo experimento foi quantificar as concentrações dos nutrientes na fase sólida e na solução do solo nas adjacências dos locais de aplicação dos fertilizantes fosfatados e potássico minerais, assim como as atividades de P e K em solução. O terceiro objetivou avaliar a absorção de P e demais nutrientes pelas plântulas de milho em função da aplicação localizada de fosfatos de cálcio e de amônio. Utilizaram-se dois solos ácidos catarinenses. Os tratamentos variaram entre os experimentos: no primeiro compararam-se os efeitos do superfosfato triplo (SFT) e do diamônio fosfato (DAP) na presença de cloreto de potássio (KCl), e as doses de P2O5 e K2O equivaleram a 100 mg kg-1 de solo. No segundo, também comparou-se o efeito do SFT e do DAP na presença ou não de KCl e de calcário, com doses de P2O5 e K2O iguais a 700 e 1236 mg kg-1 para o NV e CH, respectivamente. E no terceiro cultivaram-se plantas de milho avaliando-se o efeito da adição localizada de SFT, DAP, superfosfato simples (SS) e monoamônio fosfato (MAP), nos quais aplicou-se 200 mg de P/vaso. As doses aplicadas foram altas com a finalidade de simular as concentrações nas adjacências dos grânulos. Nas adjacências dos grânulos dos fertilizantes fosfatados minerais, a composição química do solo é afetada pelas diferentes fontes fosfatadas, onde o SFT mostrase mais eficaz que o DAP na liberação de P. A aplicação localizada dos fertilizantes fosfatada aumenta a movimentação dos nutrientes no solo, na qual a mobilização do fósforo ocorre até quatro centímetros. O método de extração Mehlich 1 superestima os valores de P quando aplica-se SFT ao solo. O DAP aumenta as concentrações de HPO4 - na solução do solo. O MAP mostra ser uma fonte eficiente na liberação de P e na sua absorção pelas plantas