Suportes à base de quitosano para regeneração óssea

Mestrado em Ciência e Engenharia de MateriaisTissue engineering research attempts to satisfy the needs of support, reinforcement and in some cases organization of the regenerating tissue with a controlled supply of bioactive substances that might positively influence the behaviour of incorporated or ingrowing cells. As demonstrated by the recent advances on biomaterials, the ideal scaffold for tissue regeneration should offer a 3D interconnected porous structure behaving as a template to promote cells adhesion and proliferation and vascularisation as well thus stimulating the new tissue ingrowth. A special interest has been focused on chitosan (CH - the partially deacetylated derivative of chitin) scaffolds for bone regeneration due to its biological and physical properties, in spite of some drawbacks regarding its lack of mechanical strength and bioactivity. The incorporation of bioactive calcium phosphates materials in the polymer matrix is expected to reinforce chitosan scaffolds improving their mechanical performance and osteoconductivity. In the present work, chitosan based scaffolds were produced by freeze-drying CH solutions containing calcium phosphate (CaP) particles, either as fibers of hydroxyapatite (HA), platelets of monetite or a mixture of both. CaP particles were prepared by a wet precipitation method. The calcium phosphate precipitation was monitored by taking a number of samples during 3-days. Evolution of the morphology and crystal phase composition of the precipitated particles were followed by scanning electron microscopy (SEM), N2 adsorption using the BET isotherm (BET), and X-ray diffraction (XRD). It was observed that the increase of refluxing temperature allowed a faster transformation of octacalcium phosphate fibers into HA fibers, hence shortening the precipitation time required for obtaining HA fibers, Chitosan based scaffolds suspensions at two different pH values were frozen at three different temperatures before freeze-drying (thermally induced phase separation-TIPS). SEM, XRD, microcomputed tomography (μ-CT) and Fourier transformed infrared spectroscopy (FTIR) were used to analyze the physical and chemical properties of the composite scaffolds. Compressive mechanical tests were also undertaken to characterize the materials. Bioactivity studies were performed in simulated body fluid (SBF) solutions by monitoring the Ca and P concentration variations of SBF solutions. Highly interconnected macroporous scaffolds with a pore size ranging from of 50 to 250μm, interconnectivity around 91-98.5%, and porosity higher than 80% were obtained. The freezing temperature and the pH of chitosan solution/suspension revealed to play a significant influence in the pore structure. The higher pH (pH=5) and the higher freezing temperature (T=0ºC) were found as the most favourable conditions for ice crystal growth which resulted in larger pores. It was also observed that CaP particles incorporation in the CH matrix increased the scaffold mechanical strength which was also conditioned by the pore size and by the reinforcing particle morphology. The bioactivity studies revealed the CaP contribution for the scaffold bioactivity. The composite scaffolds having brushite and HA (obtained at pH=2) exhibited enhanced bioactivity as compared to composite CH/HA scaffolds based. CH based scaffolds were also prepared by incorporating HA granules loaded with dexamethasone (DEX), a drug model, in CH solution. The granules were obtained by spray drying HA nanosized particles suspended in DEX solution. The drug release profiles of DEX were determined in phosphate-buffered solution (PBS) by DEX concentration evaluation in the releasing medium by Ultraviolet (UV) spectroscopy at the wavelength of 242 nm. Among the different DEX release patterns corresponding to the various DEX loading methodologies which were tested, an adequate release profile could be selected: it showed that the release of 80% of the DEX loaded amount could be ensured during ~30 days, thus enabling a prolonged and slowest DEX release as compared to literature reports. It is thus found that the CH scaffolds engineered with a calcium phosphate based drug delivery system (DDS) provides the desirable association of a bioactive and osteoconductive matrix with an in situ controlled release of a therapeutic agent. These results point out an additional potential of the composite CH/HA scaffolds for behaving as a controlled drug release system (DDS).A investigação em engenharia de tecidos (ET) tem procurado soluções para as necessidades de reforço e de regeneração dos tecidos recorrendo por vezes a substâncias bioactivas que podem favorecer a proliferação celular. Os avanços recentes em ET têm beneficiado da utilização de matrizes tridimensionais porosas (scaffolds) que permitem a adesão, proliferação e regeneração das células bem como a vascularização, estimulando a formação de novo tecido. A obtenção de scaffolds de quitosano (CH) para a regeneração óssea tem merecido especial interesse devido às suas propriedades biológicas e físicas, apresentando no entanto o inconveniente da falta de resistência mecânica e de bioatividade. A obtenção de scaffolds compósitos por incorporação na matriz polimérica de materiais bioactivos de fosfato de cálcio, permite reforçar o scaffold, melhorando o seu desempenho mecânico e a sua osteocondutividade. No presente trabalho, produziram-se scaffolds compósitos de quitosano/hidroxiapatite por processos de congelamento e liofilização de suspensões de fosfatos de cálcio (CaP) em soluções de CH. Utilizaramse CaP sintetizados laboratorialmente, quer na forma de fibras de hidroxiapatite (HA), quer de lamelas de monetite, quer de mistura dos dois. Os CaP foram sintetizados por um método de precipitação em meio aquoso, tendo-se monitorizado a precipitação de fosfato de cálcio durante 3 dias. Avaliou-se a evolução das fases cristalinas e da morfologia das partículas precipitadas por microscopia eletrónica de varrimento (SEM), difracção de raios X (XRD) e por adsorção de N2 usando a isotérmica de BET. Os resultados evidenciaram que o aumento da temperatura de refluxo acelera a transformação das fibras de octacalcium fosfato em fibras de HÁ, permitindo reduzir o tempo de precipitação total para obtenção de fibras de HA As soluções de quitosano e as suspensões de HAP em solução de CH, a dois valores de pH (pH=2 e pH= 5), foram congeladas a três temperaturas diferentes antes de serem liofilizadas. Caracterizaram-se os scaffolds por SEM, DRX, microtomografia computorizada (μ-CT) e espectroscopia de infravermelhos com transformada de Fourier (FTIR), tendo-se ainda avaliado o seu comportamento mecânico em compressão. Obtiveram-se scaffolds compósitos macroporosos com porosidade superior a 80%, tamanho de poro na gama 50-250μm e porosidade interconectada com grau de interconexão de 91-98.5%. Verificou-se que o tamanho e morfologia de poro dos scaffolds é condicionado pelo pH das suspensões e pela temperatura de congelamento. O valor de pH mais elevado (pH=5) e a temperatura de congelamento mais elevada (T=0ºC) são as condições que mais favorecem o crescimento de cristais de gelo e por conseguinte a formação de poros de maior dimensão. Verificou-se também que a incorporação de partículas de CaP na matriz polimérica de CH aumenta a resistência mecânica do scaffold, que é também condicionada pelo tamanho de poro e pela morfologia da partícula de CaP. O estudo do comportamento bioactivo dos scaffolds compósitos em soluções simuladoras do plasma humano (SBF), monitorizando a variação das concentrações de Ca e P na solução de SBF, evidenciou o contributo das partículas de CaP para a bioactividade do scaffold. Os scaffolds compósitos em que coexistem brushite e HA (preparados a pH=2) evidenciaram bioactividade superior á dos scaffolds compósitos CH/HA. Preparam-se também scaffolds incorporando grânulos de hidroxiapatite carregados com um fármaco modelo, a dexametasona (DEX), na solução inicial de CH. Os grânulos obtiveram-se por atomização de suspensões de HA nanométrica em solução de DEX. Construíram-se os perfis de libertação da DEX em solução tampão fosfato (PBS) por determinação da concentração de DEX por espectroscopia de ultravioleta (UV) ao comprimento de onda de 242 nm. Entre as várias curvas de libertação de DEX decorrentes das diferentes metodologias testadas para carregamento do fármaco, evidenciou-se um perfil de libertação de DEX segundo o qual cerca de 80% da DEX é libertado ao longo de ~30 dias, assegurando-se assim uma libertação mais lenta e prolongada do que as referidas na literatura para a DEX As características dos scaffolds compósitos preparados no presente trabalho apontam os materiais produzidos como promissores para aplicação em engenharia de tecidos, apresentando como potencial adicional a capacidade de se comportarem como sistemas de libertação controlada de fármacos

Evaluasi Perbandingan Kinerja Attached Culture Bioreaktor dan Hybrid Membran Bioreaktor dalam Mendegradasi Air Limbah

Restaurant wastewater is categorized as grey wastewater, which is low strength wastewater with a chemical oxygen demand (COD) concentration of <1,000 mg/L. Therefore, further treatment is necessary before it is discharged into the environment. This study focused on comparing the performance of an attached culture bioreactor and a Hybrid Membrane Bioreactor (HMBR) in degrading restaurant wastewater. The bioreactors used a mesh filter support media of 70-80 μm. The bioreactors were operated with COD feed concentration 600 ppm and HRT 13 hour, with artificial grey water waste feed consisting of sugar, urea, KH2PO4, and tapioca flour. The %COD removal achieved by the attached culture bioreactor and HMBR was 90,48% – 90,95% and 96,28%– 96,79%, the turbidity out achieved by the attached culture bioreactor and HMBR was 57,42 – 60,25NTU and 4,95 – 5,62NTU, MLSS value reached  2,36 – 2,86ppm and 2,36 – 2,86ppm. The conclusion of this research shows that the HMBR has relatively better performance than the attached culture bioreacto

Efisiensi air di gas conditioning tower untuk mengurangi kadar SO2 pada emisi industri semen

Industri kimia dan juga termasuk di dalamnya, industri semen, menghadapi tantangan untuk dapat terus melakukan perbaikan proses untuk melakukan efisiensi sumber daya dan meminimalkan beban pencemaran ke lingkungan. Salah satu hal yang penting di industri semen adalah kandungan SO2 pada emisinya. Kandungan emisi ditentukan oleh proses pengolahan gas, yang dilakukan dengan penyemprotan air di gas conditioning tower (GCT) dan bag filter sebelum dikeluarkan ke lingkungan melalui cerobong. Di sisi lain, konsumsi air di GCT merupakan salah satu titik penggunaan air yang tertinggi di industri semen. Studi ini bertujuan untuk menganalisis efisiensi penggunaan air di GCT dengan menggunakan seven tools mulai dari analisis masalah hingga pembuatan usulan standard operating procedure (SOP) baru. Dari analisis ini didapatkan bahwa tergantung pada kadar SO2 dan SO3 di emisi dan bahan baku, maka dapat dilakukan pengendalian temperatur inlet bag filter yang selanjutnya akan mengendalikan volum air di GCT. Hasil pengembangan/inovasi ini menunjukkan bahwa SOP baru dapat menghemat air di GCT secara signifikan

Optimasi Biaya dalam Proses Pemurnian Metanol untuk Mengurangi Resin sebagai Limbah Bahan Berbahaya dan Beracun di PT Kaltim Methanol Industri

Purification process of raw methanol from its impurities to produce pure methanol at PT. Kaltim Methanol Industri (PT KMI) is carried out by several steps, including degassing, distillation, and adsorption. One of the impurities, tri methyl amine (TMA), could be removed by adding NaOH. Another method to remove TMA is conducted by adsorption process on ion exchange resin on the vessel called TMA catchpot. The TMA catchpot performance is very crucial in methanol purification process. Thus, monitoring and optimization are required to be performed regularly. Once the TMA catchpot resin has exhausted, the performance will be drop and methanol purification could not be done efficiently. Furthermore, the ion exchange resin should be replaced with new resin. This study evaluates the performance of the TMA catchpot during the charge of 2010, 2012, and 2016, calculates the NaOH consumption during operational time, and optimizes the cost. Resin regeneration option was introduced and compared with the conventional method (i.e. resin replacement). Economic evaluation shows that the lowest annual cost could be obtained by fresh resin replacement every 4 years and resin regeneration every 2 years. Resin regeneration option gives not only annual cost reduction, but also positive impact to the environment, by decreasing the amount of hazardous waste (i.e. spent resin) significantly.Keywords: ion exchange resin; methanol purification; regeneration; tri methyl amineA B S T R A KProses pemurnian metanol mentah (raw) dari pengotornya untuk menghasilkan metanol murni di PT. Kaltim Methanol Industri (PT KMI) dilakukan melalui beberapa tahapan antara lain degassing, distilasi dan adsorpsi. Salah satu zat pengotor adalah tri methyl amine (TMA) yang dapat dihilangkan dengan penambahan NaOH. Metode lain untuk menghilangkan TMA adalah dengan proses adsorpsi menggunakan resin penukar ion di dalam tangki yang disebut TMA catchpot. Performa TMA catchpot sangat penting dalam proses pemurnian metanol. Oleh karena itu, pemantauan dan optimalisasi perlu dilakukan secara berkala. Setelah resin pada TMA catchpot jenuh, performanya akan menurun dan pemurnian metanol tidak dapat dilakukan secara efisien. Selanjutnya, resin penukar ion harus diganti dengan resin baru. Artikel ini mengevaluasi kinerja catchpot TMA pada penggantian resin (charge) 2010, 2012 dan 2016, menghitung konsumsi NaOH sebagai fungsi waktu operasi, dan mengoptimasi biaya pemurnian. Selain itu, disimulasikan opsi regenerasi resin, sebagai pembanding metode konvensional (penggantian resin). Evaluasi ekonomi menunjukkan bahwa biaya tahunan paling rendah didapatkan dengan penggantian resin baru setiap 4 tahun, dan regenerasi resin setiap 2 tahun. Selain biaya tahunan yang rendah, regenerasi ini berdampak positif terhadap lingkungan dengan mengurangi timbulan limbah B3 (resin bekas) secara signifikan.Kata kunci: pemurnian metanol; regenerasi; resin penukar ion; tri metil amin

Energy efficient harvesting of Spirulina sp. from the growth medium using a tilted panel membrane filtration

Membrane fouling is one of the main drawbacks in membrane-based microalgae harvesting. This study assessed the tilted panel to enhance filtration performance of Spirulina sp. broth. The influences of the operating parameters including the tilting angle, aeration rate and membrane materials on filtration performance and energy consumption were evaluated. Results showed that the system was effective and energy-efficient for membrane fouling control. The permeability peaked at a tilting of 45◦ thanks to combination of aeration and panel tilting. The microfiltration performed better than the ultrafiltration membrane due to the effective impact of air bubbles for foulant scouring that maximized the membrane intrinsic property. Small aeration rate of 1.0 L/min offered a high plateau permeability of 540 L/(m2⋅hr⋅bar) in which reversible fouling almost fully absent. The high permeability could be achieved under a low energy input of 0.2 kWh/m3

Micropollutant rejection of annealed polyelectrolyte multilayer based nanofiltration membranes for treatment of conventionally-treated municipal wastewater

The ever-increasing concentrations of micropollutants (MPs) found at the outlet of conventional wastewater treatments plants, is a serious environmental concern. Polyelectrolyte multilayer (PEM)-based nanofiltration (NF) membranes are seen as an attractive approach for MPs removal from wastewater effluents. In this work, PEMs of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) were coated in a layer by layer (LbL) fashion on the surface of a polyacrylonitrile ultrafiltration support to obtain PEM-based NF membranes. The impact of PEM post-treatment, by applying salt and thermal annealing, was then investigated in terms of swelling, hydrophilicity, permeability, and ion rejection. While thermal annealing produced a more compact structure of PEM, it did not improve the ion rejection. Among the different salt concentrations examined for the salt-annealing process, the highest ion rejection was observed for (PAH/PAA)15 membranes annealed in 100 mM NaNO3, interestingly without any decrease in the water permeability. This membrane was studied for the rejection of four MPs including Diclofenac, Naproxen, 4n-Nonylphenol and Ibuprofen from synthetic secondary-treated wastewater, over a filtration time of 54 h. At an early stage of filtration, the membrane became more hydrophobic and a good correlation was found between the compounds hydrophobicity and their rejection. As the filtration continued until the membrane saturation, an increase in membranes hydrophilicity was observed. Hence, in the latter stage of filtration, the role of hydrophobic interactions faded-off and the role of molecular and spatial dimensions emerged instead in MPs rejection. To test the suitability of the membranes for the ease of cleaning and repeated use, the sacrificial PEMs and foulants were completely removed, followed by re-coating of PEMs on the cleaned membrane. The higher MPs rejection observed in salt-annealed membranes compared to the non-annealed counterparts (52–82% against 43–69%), accompanied with still low ion rejection, confirm the high potential of PEM post-treatment to achieve better performing PEM-based NF membranes

Micro- and ultrafiltration membranes for wastewater treatment and microalgae filtration: influence of membrane properties and operational conditions on membrane fouling

My research focuses on development of micro- and ultrafiltration membrane processes for wastewater filtration (i.e. activated sludge in aerobic membrane bioreactor (MBR)) and microalgae broth filtration. Optimization of these membrane processes is mainly to reduce fouling phenomena which manifest in a lower permeate membrane flux. Three main factors are exploited for the aforementioned aim, i.e. (1) membrane development, (2) feed, and (3) operational parameters. First, membrane development (synthesis and modification) is carried out mainly based on polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN). Additionally, commercial membranes from Amer-sil, Polyvinyl chloride (PVC)/silica mixed matrix membranes is also used for the studies. Second, different feed is used for filtration, i.e. activated sludge and different species of microalgae. Furthermore, modification study of the feed (in microalgae) is performed by coagulation. Third, variation on filtration operational parameter is investigated, mainly on flux, vibration, chemical cleaning and also filtration cycle time. Moreover, a study to combine membrane processes in MBR and microalgae membrane photobioreactor (MPBR) is performed to treat wastewater.status: publishe

Gradual PVP leaching from PVDF/PVP blend membranes and its effects on membrane fouling in membrane bioreactors

© 2018 Elsevier B.V. Improving the hydrodynamics on the membrane surface in a magnetically induced membrane vibration system (MMV) has been proven efficient for membrane fouling control in membrane bioreactors. This advantage can be further extended by using an optimized membrane. This was realized in this study by preparing porous polyvinylidene fluoride membranes via polyvinylpyrrolidone (PVP) blending and later by leaching out the PVP from the membrane matrix via post-treatment using NaOCl. Results show that increasing the PVP content in the casting solution increases membrane fouling resistance. Slowly leaching of PVP after several periodic NaOCl cleanings increased membrane permeance. No advantage of NaOCl post-treatment was observed. The long-term filtration confirmed the superiority of the highly porous membrane that complemented the advantages offered by the MMV system. This suggests that despite the small quantity of the remaining PVP, its leaching offered a substantial gain to improve membrane filterability.status: publishe

A PVC-silica mixed-matrix membrane (MMM) as novel type of membrane bioreactor (MBR) membrane

© 2015 Elsevier B.V. A highly porous mixed matrix membrane (MMM), made from polyvinyl chloride (PVC) and silica, commonly used as separator in lead acid batteries, is screened here in a first feasibility study as a potential novel type of MBR membrane to treat synthetic wastewater encouraged by: (i) its high chemical and thermal stability and (ii) its high porosity. Its performance was compared with two commercial flat-sheet MBR membranes, a chlorinated PE and a PVDF membrane, in terms of hydraulic performance and membrane fouling. The COD removals of the three membranes were similar. The critical flux measurement also showed the potential of the MMM, being 18. LMH compared to 21. LMH for the commercial membranes. However, both short and long-term filtration tests showed that the MMM suffers from a severe irreversible fouling attributed to the blocking of the large pore mouths, which could not be removed via the applied chemical cleaning with NaOCl. Nevertheless, in a long-term test, despite the occurrence of pore blocking, other types of fouling exist to a much lesser extent in the MMM which maintains its performance comparable with the two commercial membranes.publisher: Elsevier articletitle: A PVC–silica mixed-matrix membrane (MMM) as novel type of membrane bioreactor (MBR) membrane journaltitle: Journal of Membrane Science articlelink: http://dx.doi.org/10.1016/j.memsci.2015.05.074 content_type: article copyright: Copyright © 2015 Elsevier B.V. All rights reserved.status: publishe