As a result of increasing cost, efficiency and environmental pressures ferrochrome producers strive towards lower overall energy consumption. Increases in local electricity prices have placed particular pressure on South African ferrochrome producers. Pelletised chromite pre–reduction is likely the currently applied ferrochrome production process option with the lowest specific electricity consumption. In this process fine chromite, together with a carbonaceous reductant and a clay binder is milled, pelletised and pre–reduced. In this dissertation it is demonstrated that the functioning of the clay binder in this process is not as straightforward as in conventional metallurgical pelletisation processes, since the cured pre–reduced pellets are characterised by an oxidised outer layer and a pre–reduced core. Conventional performance characteristics of clay binders (e.g. compressive strength and abrasion resistance) therefore have to be evaluated in both oxidative sintering and reducing environments. Two clay samples, i.e. attapulgite and bentonite, were obtained from a local ferrochrome producer and investigated within the context of this study. Results indicated that the compressive and abrasion resistance strengths of oxidative sintered pellets for both clays were substantially better than that of pre–reduced pellets. Thus, although the objective of the chromite pre–reduced process is to achieve maximum pre–reduction, the strength of pre–reduced chromite pellets is significantly enhanced by the thin oxidised outer layer. The strength of the bentonite–containing pellets was found to be superior in both pre–reducing and oxidative sintering environments. This is significant, since the attapulgite clay is currently the preferred option at both South African ferrochrome smelting plants applying the pelletised chromite pre–reduction process. Although not quantitatively investigated, thermo–mechanical analysis indicated that the hot strength of the attapulgite pellets could be weaker than the bentonite–containing pellets. The possible effects of clay binder selection on the level of pre–reduction were also investigated, since it could have substantial efficiency and economic implications. For both case study clays investigated, higher clay contents resulted in lower pre–reduction levels. This has relevance within the industrial process, since higher clay contents are on occasion utilised to achieve improved green strength. The average pre–reduction of the bentonite–containing pellets were also consistently higher than that of the attapulgite–containing pellets. Again, this is significant, since the attapulgite clay is currently the preferred option. In general the case study results presented in this dissertation indicated that it is unlikely that the performance of a specific clay binder in this relatively complex process can be predicted; based only on the chemical, surface chemical and mineralogical characterisation of the clay. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2012.

As a result of increasing cost, efficiency and environmental pressures ferrochrome producers strive towards lower overall energy consumption. Increases in local electricity prices have placed particular pressure on South African ferrochrome producers. Pelletised chromite pre–reduction is likely the currently applied ferrochrome production process option with the lowest specific electricity consumption. In this process fine chromite, together with a carbonaceous reductant and a clay binder is milled, pelletised and pre–reduced. In this dissertation it is demonstrated that the functioning of the clay binder in this process is not as straightforward as in conventional metallurgical pelletisation processes, since the cured pre–reduced pellets are characterised by an oxidised outer layer and a pre–reduced core. Conventional performance characteristics of clay binders (e.g. compressive strength and abrasion resistance) therefore have to be evaluated in both oxidative sintering and reducing environments. Two clay samples, i.e. attapulgite and bentonite, were obtained from a local ferrochrome producer and investigated within the context of this study. Results indicated that the compressive and abrasion resistance strengths of oxidative sintered pellets for both clays were substantially better than that of pre–reduced pellets. Thus, although the objective of the chromite pre–reduced process is to achieve maximum pre–reduction, the strength of pre–reduced chromite pellets is significantly enhanced by the thin oxidised outer layer. The strength of the bentonite–containing pellets was found to be superior in both pre–reducing and oxidative sintering environments. This is significant, since the attapulgite clay is currently the preferred option at both South African ferrochrome smelting plants applying the pelletised chromite pre–reduction process. Although not quantitatively investigated, thermo–mechanical analysis indicated that the hot strength of the attapulgite pellets could be weaker than the bentonite–containing pellets. The possible effects of clay binder selection on the level of pre–reduction were also investigated, since it could have substantial efficiency and economic implications. For both case study clays investigated, higher clay contents resulted in lower pre–reduction levels. This has relevance within the industrial process, since higher clay contents are on occasion utilised to achieve improved green strength. The average pre–reduction of the bentonite–containing pellets were also consistently higher than that of the attapulgite–containing pellets. Again, this is significant, since the attapulgite clay is currently the preferred option. In general the case study results presented in this dissertation indicated that it is unlikely that the performance of a specific clay binder in this relatively complex process can be predicted; based only on the chemical, surface chemical and mineralogical characterisation of the clay. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2012.

Made available in DSpace on 2014-12-17T14:07:00Z (GMT). No. of bitstreams: 1 AntonioCSC_DISSERT.pdf: 3611638 bytes, checksum: 66d2009e96e503fa1be4ca56924e34a1 (MD5) Previous issue date: 2011-03-14 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The clay mineral attapulgite is a group of hormitas, which has its structures formed by microchannels, which give superior technological properties classified the industrial clays, clays of this group has a very versatile range of applications, ranging from the drilling fluid for wells oil has applications in the pharmaceutical industry. Such properties can be improved by activating acid and / or thermal activation. The attapulgite when activated can improve by up to 5-8 times some of its properties. The clay was characterized by X-ray diffraction, fluorescence, thermogravimetric analysis, differential thermal analysis, scanning electron microscopy and transmission electron microscopy before and after chemical activation. It can be seen through the results the efficiency of chemical treatment, which modified the clay without damaging its structure, as well as production of polymer matrix composites with particles dispersed atapugita / A atapulgita ? um argilomineral do grupo das hormitas, que tem suas estruturas formadas por microcanais, que lhe conferem propriedades tecnol?gicas superiores a argilas classificadas industriais, esse grupo de argilas tem um leque de aplica??es muito vers?til, que vai de fluido de perfura??o para po?os de petr?leo at? aplica??es na ind?stria farmac?utica. Tais propriedades podem ser melhoradas por ativa??o acida e/ou ativa??o t?rmica. A atapulgita quando ativada pode melhorar em at? de 5 a 8 vezes algumas de suas propriedades. A argila foi caracterizada por difra??o de raios X, fluoresc?ncia, an?lise termogravim?trica, an?lise t?rmica diferencial, microscopia eletr?nica de varredura e microscopia eletr?nica de transmiss?o antes e depois da ativa??o qu?mica. ? poss?vel observar, atrav?s dos resultados a efici?ncia do tratamento qu?mico, que modificou a argila sem danificar sua estrutura, assim como produ??o de composito de matriz polim?rica com part?culas dispersas de atapugita

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) PHBV is a biodegradable polyester produced by various microorganisms, which has been studied as an option for the production of disposable items in place of polymers derived from petroleum, thus contributing to the preservation of the environment. However, this thermoplastic has some disadvantages that limit its use in industrial scale applications: the relative difficulty of processing, low elongation at break, high degree of crystallinity and high cost of production relative to conventional polymers. An alternative to improve the properties of PHBV is the incorporation of small amounts of clay to the polymer, producing polymer /clay composites. The attapulgite is a typical fibrous clay. It has a surface area around 125 to 210 m2 /g and a cation exchange capacity from 20 to 30 milliequivalents per 100g of clay. The objective of this work was the production and characterization of biodegradable composites of poly (3-hydroxybutyrate-co- 3-hydroxyvalerate) - PHBV reinforced with natural attapulgite (AT) or attapulgite modified with hexadecylmethylammonium chloride (ATM) in different compositions ( 1, 3 and 5%). The composites were characterized by X-Ray Diffraction (XRD), Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Nuclear Magnetic Resonance (NMR). The best results were obtained with incorporation of ATM levels greater than 3% (w /w). In these cases, it was observed reduction of the degree of crystallinity and decreasing of melting and glass transition temperatures as compared to PHBV films. However, the presence of attapulgite decreased the thermal stability of PHBV. / O poli(3-hidroxibutirato-co-3-hidroxivalerato) - PHBV é um poliéster biodegradável, produzido por diversos microorganismos que vem sendo estudado como uma opção para a produção de artigos descartáveis em substituição a polímeros derivados de petróleo, contribuindo, assim, para a preservação do meio ambiente. No entanto, este termoplástico apresenta algumas desvantagens que limitam seu uso no desenvolvimento de aplicações industriais: relativa dificuldade de processamento, baixo alongamento na ruptura, alto grau de cristalinidade e custo elevado de produção em relação a polímeros convencionais. Uma alternativa para melhorar as propriedades do PHBV é a incorporação de pequenas quantidades de argilomineral ao polímero, produzindo compósitos polímero/argila. A atapulgita é um argilomineral tipicamente fibroso. Possui uma área superficial em torno de 125 a 210 m2/g e uma capacidade de troca catiônica de 20 a 30 miliequivalentes por 100g de argila. O objetivo deste trabalho foi a obtenção e caracterização de nanocompósitos biodegradáveis de poli (3- hidroxibutirato-co-3-hidroxivalerato) - PHBV reforçados com atapulgita natural (AT) ou com atapulgita modificada com cloreto de hexadecil trimetil amônio (ATM), em diferentes composições (1, 3 e 5%). Os compósitos foram caracterizados por Difração de Raios X (DRX), Espectroscopia no Infravermelho com Transformada de Fourier (FTIR), Microscopia Eletrônica de Varredura (MEV), Calorimetria Diferencial de Varredura (DSC), Análise Termogravimétrica (TGA) e Ressonância Magnética Nuclear (RMN). Quando comparados com os filmes de PHBV, a incorporação de teores de ATM maiores do que 3% (p/p) propiciaram a redução do grau de cristalinidade, diminuição das temperaturas de fusão e de transição vítrea. A presença da atapulgita diminuiu a estabilidade térmica do PHBV. Foi observada uma diminuição na temperatura de cristalização e uma diminuição no grau de cristalinidade do polímero em função do acréscimo de argila à matriz do PHBV.

M. Tech. (Department of Chemistry, Faculty of Applied And Computer Sciences), Vaal University of Technology. / Biodiesel has an ability to solve the problem associated with the use of fossil fuels as a source of energy. The aim of this study was to produce biodiesel from waste cooking oil (WCO) by transesterification, catalysed with potassium hydroxide (KOH) supported on attapulgite (ATP) clay as the heterogeneous catalyst. WCO was used on the basis that it is one of the cheapest feedstocks for biodiesel production, is readily available and can minimise environmental impact. ATP clay was first crushed and sieved to particle sizes of ≤ 90 μm and subsequently treated with hydrochloric acid (HCl) to remove impurities. The KOH supported ATP catalyst was prepared through ion exchange method by soaking ATP into KOH solution, dried in an oven and later calcined at 400 ℃ in a furnace. The prepared catalyst and ATP clay were characterised using Hammett indicator to determine the basic strength of the catalyst. XRF and EDX were used to determine the elemental composition of the catalyst whilst XRD was used to determine the crystallinity of the ATP after modification. The functional groups of ATP were determined by FTIR. BET was utilised to determine the changes on the surface area, pore volume and pore diameter of ATP and on the other hand, SEM was used to determine the morphological changes on the surface of ATP. The XRD, FTIR, BET AND SEM-EDX showed that addition of potassium caused changes on the surface of the ATP. The optimal conditions for the transesterification reaction of waste cooking oil with methanol were found to be oil-to-methanol molar ratio of 1:15, 3wt% catalyst amount, 65 ℃, 3 h of a reaction time, at 200 rpm stirring rate and 94 % biodiesel yield was obtained. After the catalyst was reuse three consecutive times, the decrease in biodiesel yield was observed (Figure 17) after each cycle. However, the 5MKOH/ATP catalyst is heterogeneous and can be used to transesterify WCO with good yield.

Made available in DSpace on 2014-12-17T14:07:03Z (GMT). No. of bitstreams: 1 LuandaGD_DISSERT.pdf: 2374976 bytes, checksum: 5b49cc11854aa2427f22f38d6ff109c2 (MD5) Previous issue date: 2012-08-24 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The study aimed at the treatment of attapulgite for the development and characterization of composite recycled low density polyethylene - PEBD_rec embedded with natural attapulgite - ATP_NAT, sifted - ATP_PN and attapulgite treated with sulfuric acid - ATP_TR in different compositions (1, 3 and 5%) and compared with the PEBD_rec. The atapulgitas, natural, screened and treated, were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), particle size analysis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and determining the area specific surface (BET). The composites were characterized by thermogravimetry (TG), differential scanning calorimetry (DSC), Xray diffraction (XRD), torque rheometry, scanning electron microscopy (SEM) and traction. The composite PEBD_rec / ATP (natural, sieved and treated) were produced by mixing in the molten state in a single screw extruder matrix wire with subsequent reprocessing matrix tape. It was found that the screening of attapulgite not reduce the quantity of quartz and the acid treatment completely extracted dolomite aggregate impurities of the channels attapulgite, and increase their surface area. The addition of attapulgite in PEBD_rec acts as a catalyst, reducing the thermal stability of the polymer. The increased concentration of attapulgite, increases resistance and reduces the elongation at break and modulus of elasticity of the composite PEBD_rec / attapulgite / O trabalho teve como objetivo o tratamento da atapulgita para o desenvolvimento e a caracteriza??o de comp?sito de polietileno de baixa densidade reciclado PEBD_rec incorporado com atapulgita natural ATP_NAT, peneirada ATP_PN e com atapulgita tratada com ?cido sulf?rico ATP_TR, em diferentes composi??es (1, 3 e 5%) e comparado com o PEBD_rec. As atapulgitas, natural, peneirada e tratada, foram caracterizadas por difra??o de raios X (DRX), fluoresc?ncia de raios X (FRX), an?lise granulom?trica, microscopia eletr?nica de varredura (MEV), espectroscopia de energia dispersiva (EDS) e determina??o da ?rea superficial espec?fica (BET). Os comp?sitos foram caracterizados por an?lise termogravim?trica (TG), calorimetria diferencial explorat?ria (DSC), difra??o de raios X (DRX), reometria de torque, microscopia eletr?nica de varredura (MEV) e tra??o. Os comp?sitos de PEBD_rec /ATP (natural, peneirada e tratada) foram produzidos por meio de mistura no estado fundido em uma extrusora monorosca com matriz de fio com posterior reprocessamento com matriz de fita. Verificou-se que o peneiramento da atapulgita n?o reduziu o teor de quartzo e que o tratamento ?cido extraiu completamente a dolomita, impureza agregada nos canais da atapulgita, al?m de aumentar sua ?rea superficial. A adi??o da atapulgita no PEBD_rec atua como catalisador, reduzindo a estabilidade t?rmica do pol?mero. O aumento da concentra??o de atapulgita aumenta a resist?ncia e reduz o alongamento na ruptura e o m?dulo de elasticidade do comp?sito PEBD_rec / atapulgita

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Composites hydrogels were developed in film shape based on poly vinyl alcohol (PVA) using acidified attapulgite as crosslinking agent. The hydrogel composites were obtained in solution with amounts of attapulgite ranging from 0.05 to 2% in the polymer matrix in order to study its influence on the crystallinity, in the swelling properties and in the release of gentamicin sulphate. The obtained composites were characterized by XRD, FTIR and DSC. According to XRD data the polymer crystallinity is not affected by the clay addition, however, the presence of attapulgite modifies the melting and crystallization temperatures, behavior observed by DSC measures. In general, graphical profile of FTIR showed that there are interactions between PVA and attapulgite. The hydration kinetics at 37°C is independent of pH values and shown to obey the Fickian diffusion mechanism with values of n<0.5. Thus, the viability of hydrogels in drug delivery systems was evaluated by the swelling degree and by in vitro release. These two aspects were dependent on the concentration of the drug. Thus, although preliminaries, the results from release of gentamicin sulphate using PVA/attapulgite composites hydrogels proved be promising for future application. / Foram desenvolvidos hidrogéis compósito na forma de filme a base de poli (álcool vinílico) (PVA) usando a atapulgita acidificada como agente de reticulação. Os hidrogéis compósitos foram obtidos em solução variando a quantidade de atapulgita (0,05-2%) na matriz polimérica visando estudar sua influência na cristalinidade, nas propriedades de intumescimento e na liberação do sulfato de gentamicina. Os materiais preparados foram caracterizados por DRX, FTIR, DSC. Segundo os dados do DRX a cristalinidade do polímero não é afetada pela adição da argila, em contrapartida, a presença da atapulgita altera as temperaturas de fusão e cristalização, comportamento verificado pelo DSC. De maneira geral, o perfil gráfico do FTIR evidenciou que há interações entre a atapulgita e o PVA. A cinética de hidratação a 37°C mostrou ser independente do valor de pH e demostrou obedecer ao mecanismo de difusão fickiana com valores de n<0,5. Desse modo, a viabilidade dos hidrogéis em sistema de liberação de fármacos foi avaliada pelo grau de intumescimento e liberação in vitro. Estes dois aspectos foram dependentes da concentração do fármaco. Assim, apesar de preliminares, os resultados de liberação do sulfato de gentamicina utilizando hidrogéis compósito PVA/ atapulgita mostraram-se promissores para uma futura aplicação.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-03-19T16:27:31Z No. of bitstreams: 1 THIANNE SILVA BATISTA - DISSERTAÇÃO PPGEQ 2016..pdf: 2177027 bytes, checksum: 65931e0e786c26d61bb005c1fd18e0f7 (MD5) / Made available in DSpace on 2018-03-19T16:27:31Z (GMT). No. of bitstreams: 1 THIANNE SILVA BATISTA - DISSERTAÇÃO PPGEQ 2016..pdf: 2177027 bytes, checksum: 65931e0e786c26d61bb005c1fd18e0f7 (MD5) Previous issue date: 2016-05-25 / Capes / O processo de separação por adsorção destaca-se como uma alternativa para minimizar os problemas de contaminação em recursos hídricos e revela uma abrangente aplicabilidade, devido principalmente à utilização de argilas como adsorventes. O presente trabalho teve como objetivo avaliar a capacidade de adsorção da argila atapulgita in natura e modificada com o sal quaternário de amônio, como adsorvente de efluentes oleosos sintéticos. Foram realizados planejamentos experimentais fatoriais 22, em que, tiveram como variáveis independentes, a concentração inicial do óleo presente no efluente e tempo de agitação do processo, e como variável resposta o percentual de remoção de óleo. Em seguida, o ensaio de remoção foi avaliado realizando um estudo de viabilidade do processo de adsorção, com a obtenção do mecanismo de adsorção por meio da cinética, como também, com a definição do modelo que descreve o processo de adsorção através da isoterma. Diante as caracterizações realizadas na argila atapulgita foi possível identificar com a Difratometria de raios X (DRX) que sua estrutura não favorece a um deslocamento na intensidade dos picos após o processo de organofilização, porém, com a Espectroscopia na região do infravermelho (FTIR) fica evidenciada a presença dos grupos orgânicos comprovando, assim, a inserção do sal na estrutura da atapulgita; com a Microscopia eletrônica de varredura (MEV) observou-se uma morfologia fibrosa da argila e a Fisissorção de N2 (Método de BET) indicou a presença de estrutura mesoporosa da atapulgita in natura e macroporosa da argila organofílica. Os ensaios de adsorção demonstrou que o processo de organofilização aplicada à atapulgita favoreceu o processo de adsorção, pois desempenhou 67,57% de remoção de óleo e uma capacidade de adsorção de 7,23 mg de óleo por grama de argila, na concentração inicial de 100 mg.L-1 de óleo e no tempo de agitação de 1 hora. Com a aplicação dos modelos teóricos observou-se um coeficiente de determinação R² = 0,98, indicando uma forte correlação da equação de segunda ordem na cinética de adsorção. Para isoterma de adsorção, verificou-se que a equação de Freundlich, Langmuir e da Sigmoide BiDR, ajustaram-se aos dados experimentais. / The process of adsorptive separation stands out as an alternative to minimize contamination problems in water and shows a broad applicability, mainly due to the use of clays as adsorbent. This study aimed to evaluate the adsorption capacity of natural and modified attapulgite clay, using this material as an adsorbent of synthetic oily wastewater. 22 factorial experimental designs were conducted, wherein, the initial concentration of oil present in the effluent and the stirring time were independent variables and the response variable was the oil removal percentage. Then, the removing test was evaluated by performing a feasibility study of the adsorption process, obtaining the adsorption mechanism through kinetics, as well as with the definition of the model which best describes the experimental data through the adsorption isotherm. From the characterizations performed with the attapulgite clay, it was identified with x-ray diffraction (XRD) that its structure does not favor a shift in the intensity of the peaks after the organophilization process, however, the spectroscopy in the infrared (FTIR) demonstrated the presence of the organic groups confirming the insertion of the salt in the attapulgite structure; furthermore, through scanning electron microscopy (SEM), it was observed a fibrous morphology of the clay and N2 physisorption (BET method) indicated the presence of mesoporous structure of natural attapulgite and macroporous of organoclay. Adsorption tests showed that the organophilization applied to attapulgite favored the adsorption process because a 67.57% removal of oil and an adsorption capacity of 7.23 mg of oil per gram of clay were obtained, with the initial concentration of 100 mg.L-1 oil and a stirring time of 1 hour. With the application of theoretical models, a coefficient of determination of R² = 0.98 was reached, indicating a strong correlation of the second-order equation in the adsorption kinetics. For adsorption isotherm, it was found that Freundlich, Langmuir and Sigmoid BIDR equations fitted the experimental data.