Os processos de separação com membranas estão presentes nas mais diversas aplicações industriais. Em especial, a microfiltração e a ultrafiltração vêm sendo extensivamente utilizadas no tratamento de água e de efluentes. Com o aumento da demanda, muitos estudos têm sido feitos para melhorar o desempenho dos processos com membranas, porém a escolha apropriada da membrana é um fator crucial para atingir esse objetivo. As membranas à base de polietersulfona (PES) estão entre as mais utilizadas industrialmente para esse tipo de aplicação devido às suas excelentes propriedades mecânicas, estabilidade térmica e resistência química. No entanto, por serem pouco hidrofílicas, essas membranas apresentam baixos fluxos de água e elevada tendência ao fouling e ao biofouling. A fim de melhorar essas propriedades, muitos autores têm proposto modificações nas membranas para torná-las mais hidrofílicas e, portanto, aumentar o fluxo de água e diminuir o fouling. Dentro desse contexto, o presente trabalho teve como objetivo preparar membranas de ultrafiltração de PES, utilizando a ftaloil-quitosana (FQ) como aditivo, a fim de se obter membranas com propriedade antifouling. Membranas de PES e PES/FQ foram preparadas pelo processo de inversão de fases e caracterizadas quanto à morfologia, à estrutura química, à estabilidade térmica, ao caráter hidrofílico, à permeância hidráulica, à massa molar de corte (MMC) e ao desempenho em ultrafiltração de solução proteica. As membranas modificadas com o aditivo apresentaram estrutura mais heterogênea e com macrovazios maiores, maior caráter hidrofílico e maior permeância hidráulica. Os resultados de MMC não foram conclusivos. No teste de ultrafiltração, essas membranas apresentaram maiores fluxos e menor tendência ao fouling, indicando que o aditivo utilizado foi adequado na melhoria das propriedades desejadas. A retenção proteica, a perda de fluxo e a recuperação de fluxo após limpezas não apresentaram diferenças significativas. / In recent years, membrane separation processes have been widely used in all kinds of industries and applications. Particularly microfiltration and ultrafiltration have been extensively used for drinking water and wastewater treatments. With the increasing demand, many efforts have been done in order to enhance the process performance, but the choice of the appropriate membrane is a crucial factor to achieve this goal. Polyethersulfone (PES) based membranes are among the most commonly used for such applications due to their excellent chemical resistance, thermal stability and mechanical properties. However, because of its low hydrophilicity, these membranes have low water flux and high fouling and biofouling tendency. In order to improve these properties, many authors have proposed membrane modifications to make them more hydrophilic and thus increase the water flux and reduce fouling. Within this context, this work aimed to prepare PES ultrafiltration membranes using phthaloyl-chitosan (FQ) as an additive in order to obtain membranes with antifouling property. PES and PES/FQ membranes were prepared by phase inversion process and their morphology, chemical structure, thermal stability, hydrophilicity, hydraulic permeance, molecular weight cutoff (MWCO) and performance in ultrafiltration of protein solution were characterized. The membranes modified with additives showed more heterogeneous structure with larger macrovoids, higher hydrophilicity and higher hydraulic permeance. The MWCO results were inconclusive. In the ultrafiltration test, these membranes exhibited higher fluxes and lower fouling tendency, indicating that the additive used was adequate in improving the desired properties. The protein retention, flux reduction and flux recovery after cleaning showed no significant differences.

Os processos de separação com membranas estão presentes nas mais diversas aplicações industriais. Em especial, a microfiltração e a ultrafiltração vêm sendo extensivamente utilizadas no tratamento de água e de efluentes. Com o aumento da demanda, muitos estudos têm sido feitos para melhorar o desempenho dos processos com membranas, porém a escolha apropriada da membrana é um fator crucial para atingir esse objetivo. As membranas à base de polietersulfona (PES) estão entre as mais utilizadas industrialmente para esse tipo de aplicação devido às suas excelentes propriedades mecânicas, estabilidade térmica e resistência química. No entanto, por serem pouco hidrofílicas, essas membranas apresentam baixos fluxos de água e elevada tendência ao fouling e ao biofouling. A fim de melhorar essas propriedades, muitos autores têm proposto modificações nas membranas para torná-las mais hidrofílicas e, portanto, aumentar o fluxo de água e diminuir o fouling. Dentro desse contexto, o presente trabalho teve como objetivo preparar membranas de ultrafiltração de PES, utilizando a ftaloil-quitosana (FQ) como aditivo, a fim de se obter membranas com propriedade antifouling. Membranas de PES e PES/FQ foram preparadas pelo processo de inversão de fases e caracterizadas quanto à morfologia, à estrutura química, à estabilidade térmica, ao caráter hidrofílico, à permeância hidráulica, à massa molar de corte (MMC) e ao desempenho em ultrafiltração de solução proteica. As membranas modificadas com o aditivo apresentaram estrutura mais heterogênea e com macrovazios maiores, maior caráter hidrofílico e maior permeância hidráulica. Os resultados de MMC não foram conclusivos. No teste de ultrafiltração, essas membranas apresentaram maiores fluxos e menor tendência ao fouling, indicando que o aditivo utilizado foi adequado na melhoria das propriedades desejadas. A retenção proteica, a perda de fluxo e a recuperação de fluxo após limpezas não apresentaram diferenças significativas. / In recent years, membrane separation processes have been widely used in all kinds of industries and applications. Particularly microfiltration and ultrafiltration have been extensively used for drinking water and wastewater treatments. With the increasing demand, many efforts have been done in order to enhance the process performance, but the choice of the appropriate membrane is a crucial factor to achieve this goal. Polyethersulfone (PES) based membranes are among the most commonly used for such applications due to their excellent chemical resistance, thermal stability and mechanical properties. However, because of its low hydrophilicity, these membranes have low water flux and high fouling and biofouling tendency. In order to improve these properties, many authors have proposed membrane modifications to make them more hydrophilic and thus increase the water flux and reduce fouling. Within this context, this work aimed to prepare PES ultrafiltration membranes using phthaloyl-chitosan (FQ) as an additive in order to obtain membranes with antifouling property. PES and PES/FQ membranes were prepared by phase inversion process and their morphology, chemical structure, thermal stability, hydrophilicity, hydraulic permeance, molecular weight cutoff (MWCO) and performance in ultrafiltration of protein solution were characterized. The membranes modified with additives showed more heterogeneous structure with larger macrovoids, higher hydrophilicity and higher hydraulic permeance. The MWCO results were inconclusive. In the ultrafiltration test, these membranes exhibited higher fluxes and lower fouling tendency, indicating that the additive used was adequate in improving the desired properties. The protein retention, flux reduction and flux recovery after cleaning showed no significant differences.

Coagulation/flocculation/sedimentation is a common pretreatment process prior to microfiltration (MF) or ultrafiltration (UF) to alleviate membrane fouling, however there has been limited research on floatation as the pretreatment separation process. The main objective of this study is to compare sedimentation with floatation as part of the pretreatment for ultrafiltration of Ottawa River water (ORW) with relatively high natural organic matter (NOM) content. Water samples pretreated at two full-scale plants were subjected to multiple-day UF membrane fouling tests (constant flux with backwash and chemical cleaning) using an automated bench-scale UF hollow fiber membrane system. For all the experiments, the transmembrane pressure (TMP) increased sharply during the beginning of the operation (~10 h), which indicated the adsorption was significant. In the later cycles, the TMP showed a more linear constant increase, which indicated the built up of the cake layers. The total fouling index (TFI), hydraulically irreversible fouling index (HIFI) and chemical irreversible fouling index (CIFI) for floated water were much smaller than those of settled waters during both summer and winter testing. Thus, for this type of water coagulation/floatation pretreatment was superior process compared to coagulation/sedimentation, the decreased fouling appears to be linked to greater hydrophobic NOM removal by the coagulation/floatation. For all the tests, HIFI/TFIs were less than 0.1, which is to mean most of the fouling was reversible by hydraulic backwashing.Large fluctuation of backwash efficiencies with time were found for all the tested waters. Enhanced chemical backwash with 100 ppm chlorine and chemical clean with 0.1N NaOH & 200 ppm chlorine were found to be very effective at reducing fouling for pretreated ORW. As expected longer filtration cycles resulted in greater fouling but with a slightly greater degree of hydraulically reversible fouling.

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Effect of ionic strength on the efficiency of heavy metal removal and recovery from aqueous solutions via continuous mode polymer enhanced ultrafiltration (PEUF) method was examined. Application of PEUF to divalent ions of cadmium, nickel and zinc after their prior linking with polyethylenimine (PEI) results in complete removal of metal ions from single component aqueous solutions at high pHs. Binding ability and hence the extent of metal retention in high ionic strength medium exhibits differences between solutions containing single and multicomponent metal mixtures. In single component metal solutions, extent of retention decreases but binding order of metals remains unaffected both in low and high ionic strength medium. But, in binary component metal mixtures, with increase in ionic strength the binding order of metals changes. Fractional separation of Cd, Ni and Zn ions from equimolar binary and ternary mixtures of these metals and effect of ionic strength on fractional separation efficiency were investigated. Depending on pH and salt concentration and metal pairs present in the solution fractional separation can be achieved.Dynamic and static light scattering experiments were performed in order to gain insight about the conformational changes in PEI structure due to the pH and ionic strength alternations in solution. It was found that, the increase in ionic strength reduces the size of the macromolecules. A chemical equilibrium model was developed in order to estimate the apparent binding constants of metal-PEI complexes. Based on the data obtained from continuous and batch mode PEUF experiments apparent binding constants were estimated and compared to reveal the performance differences between these operational modes.