Abstract Kaolinite clay (KC) obtained from redemption camp; Nigeria was modified by surface grafting and investigated for the removal of Pb2+ and Cd2+ ions from aqueous solution by adsorption. KC and the modified kaolinite clay (MKC) were characterized using X-ray Diffraction analysis (XRD), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analyzer, Fourier Transform Infrared spectrometer (FTIR), Particle Size Distribution (PSD), zeta potential, elemental analysis (CHNS/O analyzer) and Energy Dispersive Spectroscopy (EDS). Equilibrium, thermodynamics and kinetic studies were conducted by considering the effects of pH, initial metal ion concentration, contact time, adsorbent weight and temperature. Modification of KC increased its equilibrium adsorption capacity from 8.01 mg/g to 24.41 mg/g for Cd2+ and from 24.75 mg/g to 36.41 mg/g for Pb2+ ions. The adsorption process obeys Freundlich and Temkin isotherms. The adsorption was second-order-kinetic and controlled by both intra-particle and liquid film diffusion. Values of ΔGo, ΔHo and ΔSo for KC and MKC showed a stable adsorbent-adsorbate configuration.

Resumo Os novos materiais restauradores em desenvolvimento devem evitar danos aos tecidos dentários. Portanto, o objetivo deste estudo foi avaliar a biocompatibilidade de uma marca comercial de cimento de ionômero de vidro convencional (CIV) modificado com microfibras de celulose (CIV+MC) ou nanocristais de celulose (CIV+NC) através da implantação de três amostras em tecido subcutâneo na região dorsal de 15 ratos Rattus norvegicus albinus. Cada rato recebeu um exemplar de cada cimento, resultando nos seguintes grupos (n=15): Grupo CIV (controle, n=15), Grupo CIV+MC e Grupo CIV+NC. Nos intervalos de 7, 30 e 60 dias os animais foram sacrificados e os seguintes aspectos foram avaliados histologicamente: tipo de células inflamatórias, fibroblastos, vasos sanguíneos, macrófagos, células gigantes, tipo de reação inflamatória e espessura da cápsula (µm). Estes eventos foram quantitativamente classificados conforme os escores: (-) ausente, (+) suave, (++) moderado e (+++) intenso. Os resultados foram analisados estatisticamente pelo teste Kruskal-Wallis e pós-teste Mann-Whitney. Aos 7 dias, o Grupo CIV+NC demonstrou um nível mais elevado de reparação tecidual porque havia maior quantidade de fibroblastos (p=0,022) e uma menor quantidade de macrófagos (p=0,008) e células mononucleares (p=0,033). Neutrófilos e células gigantes estavam ausentes em todos os períodos experimentais. Aos 60 dias, o Grupo CIV+NC apresentou cápsula de tecido fibroso com espessura mais reduzida (26,72±2,87 µm) em comparação ao Grupo CIV+MC (41,21±3,98 µm (p=0,025). No geral, todos os materiais apresentaram satisfatória biocompatibilidade, no entanto, o cimento de ionômero de vidro modificado com nanocristais de celulose proveu reparação tecidual mais avançada comparativamente aos demais materiais avaliados.

Developing new restorative materials should avoid damage to tissue structures. This study evaluated the biocompatibility of a commercial dental glass ionomer cement (GIC) mechanically reinforced with cellulose microfibers (GIC+CM) or cellulose nanocrystals (GIC+CN) by implantation of three test specimens in subcutaneous tissue in the dorsal region of 15 Rattus norvegicus albinus rats. Each rat received one specimen of each cement, resulting in the following groups (n=15): Group GIC (Control), Group GIC+CM and Group GIC+NC. After time intervals of 7, 30 and 60 days, the animals were sacrificed and the following aspects were histologically evaluated: type of inflammatory cells, fibroblasts, blood vessels, macrophages, giant cells, type of inflammatory reaction and capsule thickness (µm). These events were scored as (-) absent, (+) light, (++) moderate and (+++) intense. The results were statistically analyzed by Kruskal-Wallis test and Mann-Whitney post test. At 7 days, Group GIC+NC showed more favorable tissue repair because quantitatively there were more fibroblasts (p=0.022), fewer macrophages (p=0.008) and mononuclear cells (p=0.033). Polymorphonuclear neutrophils and giant cells were absent in all experimental periods. At 60 days, test specimens in Group GIC+NC were surrounded by a fibrous tissue capsule with reduced thickness (26.72±2.87 µm) in comparison with Group GIC+CM (41.21±3.98 µm) (p=0.025). In general, all biomaterials showed satisfactory biocompatibility, but glass ionomer cement modified with cellulose nanocrystals showed a more advanced tissue repair.

Bionanocomposites derived from poly(L-Lactide) (PLLA) were reinforced with chemically modified cellulose nanocrystals (m-CNCs). The effects of these modified cellulose nanoparticles on the mechanical and hydrolytic degradation behavior of polylactide were studied. The m-CNCs were prepared by a method in which hydrolysis of cellulose chains is performed simultaneously with the esterification of hydroxyl groups to produce modified nanocrystals with ester groups. FTIR, elemental analysis, TEM, XRD and contact angle measurements were used to confirm and characterize the chemical modifications of the m-CNCs. These bionanocomposites gave considerably better mechanical properties than neat PLLA based on an approximately 100% increase in tensile strength. Due to the hydrophobic properties of the esterified nanocrystals incorporated into a polymer matrix, it was also demonstrated that a small amount of m-CNCs could lead to a remarkable decrease in the hydrolytic degradation rate of the biopolymer. In addition, the m-CNCs considerably delay the degradation of the nanocomposite by providing a physical barrier that prevents the permeation of water, which thus hinders the overall absorption of water into the matrix. The results obtained in this study show the nanocrystals can be used to reinforce polylactides and fine-tune their degradation rates in moist or physiological environments.

This review reports the preparation and characterization of bionanocomposites based on biodegradable polymers reinforced with cellulose nanocrystals (CNC) described in the literature. The outstanding potential of cellulose nanocrystals as reinforcement fillers of biodegradable polymers is presented with an emphasis on the solution casting process, which is an appropriate method to investigate the physico-chemical effects of the incorporation of CNC into the polymeric matrices. Besides solution casting, other small scale methods such as electrospinning and layer-by-layer are also covered.

O objetivo do trabalho foi desenvolver uma embalagem biodegradável utilizando como matriz polimérica o amido de mandioca plastificada com glicerol e reforçada com a incorporação de nanocelulose da fibra de coco, bem como, avaliar o efeito da adição de um aditivo natural (erva-mate) nas formulações de nanobiocompósitos com ação antioxidante. Os nanocristais de celulose (L/D=39) foram obtidos por hidrólise ácida com H2SO4 a 65%. Os filmes foram preparados por casting contendo 4,5 e 6,0% de amido, 0,5 e 1,5% de glicerol, 0,3% de nanocelulose e 20% de extrato de erva-mate. O armazenamento do azeite de dendê embalado com os filmes contendo o aditivo foi monitorado por 40 dias sob condições de oxidação acelerada (63%UR/30°C). Constatou-se que, à medida que aumentam as perdas de Polifenóis Totais nos filmes, ocorre um menor aumento do Índice de Peróxidos do produto embalado, demonstrando, assim, que, ao invés do produto, os compostos da embalagem é quem estão sofrendo oxidação. A incorporação de extrato de erva-mate não alterou as propriedades mecânicas e de barreira desses filmes.

The objective was to develop biodegradable packaging using a polymer matrix as the cassava starch plasticized with glycerol and reinforced with the incorporation of nanocelulose of coconut fiber, as well as to evaluate the effect of the addition of an additive nature (yerba mate) in nanobiocompósitos formulations with antioxidant action. The nanocrystal cellulose (L/D=39) were obtained by acid hydrolysis with 65% H2SO4. The films were prepared by casting containing 4.5 and 6.0% starch, 0.5 and 1.5% glycerol, 0.3% nanocelulose and 20% extract of yerba mate. The palm oil storage packed with films containing the additive was monitored for 40 days under conditions of accelerated oxidation (63%UR/30°C). It was found that as the losses increase polyphenol films, there is a smaller increase of the peroxide value of the packaged product, thus demonstrating that instead of the product, the compounds of the package's who are suffering oxidation. The incorporation of yerba mate extract did not alter the mechanical and barrier properties of these films.

One of the difficulties reported for the suspension polymerization is control the size and granulometry of beads. The purpose of this work was to evaluate the use of cellulose nanowhiskers and mesoporous silica as stabilizers to reduce the size and the particle distribution. To monitor polymerization process was used FTIR-ATR spectroscopy. The morphology was analyzed by scanning electron microscopy. The particle size distribution was characterised using a CILAS granulometer. Thermal stability was studied by thermogravimetric analysis. The results indicated that cellulose nanowhiskers may provide stabilization and increase the thermal stability of the beads in contrast to mesoporous silica.