Advantages and Disadvantages of Bioplastics Production from Starch and Lignocellulosic Components.

The accumulation of plastic wastes in different environments has become a topic of major concern over the past decades; therefore, technologies and strategies aimed at mitigating the environmental impacts of petroleum products have gained worldwide relevance. In this scenario, the production of bioplastics mainly from polysaccharides such as starch is a growing strategy and a field of intense research. The use of plasticizers, the preparation of blends, and the reinforcement of bioplastics with lignocellulosic components have shown promising and environmentally safe alternatives for overcoming the limitations of bioplastics, mainly due to the availability, biodegradability, and biocompatibility of such resources. This review addresses the production of bioplastics composed of polysaccharides from plant biomass and its advantages and disadvantages.

Kraft lignin fractionation by organic solvents: Correlation between molar mass and higher heating value.

The new concept of integrated biorefineries has significantly changed pulp and paper industries. Lignin, which until then was only burned to generate energy, is now an important raw material for new products production. Kraft lignin (KL) fractions obtained by sequential fractionation with five organic solvents. This sequence allows to extract fractions from lower molar mass to higher molar one, resulting in more homogeneous samples. Lignin's fractions were characterized by FTIR, GPC, TGA and Higher Heating Value (HHV). HHV for KL was 24966, the lowest being 17,891 (F5) and the highest being 27051 J/g (F1), inversely proportional to the molar masses of fractions. This is a very important result indicating that the lower HHV fractions can be used for certain applications, such as antioxidants, additives, polymers, among others, adding value to kraft lignin. Fractions with higher HHV could be used for energy generation in the cellulose paper industry.

Three-Dimensional Stable Alginate-Nanocellulose Gels for Biomedical Applications: Towards Tunable Mechanical Properties and Cell Growing.

Hydrogels have been studied as promising materials in different biomedical applications such as cell culture in tissue engineering or in wound healing. In this work, we synthesized different nanocellulose-alginate hydrogels containing cellulose nanocrystals, TEMPO-oxidized cellulose nanocrystals (CNCTs), cellulose nanofibers or TEMPO-oxidized cellulose nanofibers (CNFTs). The hydrogels were freeze-dried and named as gels. The nanocelluloses and the gels were characterized by different techniques such as Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA), while the biological features were characterized by cytotoxicity and cell growth assays. The addition of CNCTs or CNFTs in alginate gels contributed to the formation of porous structure (diameter of pores in the range between 40 and 150 µm). TEMPO-oxidized cellulose nanofibers have proven to play a crucial role in improving the dimensional stability of the samples when compared to the pure alginate gels, mainly after a thermal post-treatment of these gels containing 50 wt % of CNFT, which significantly increased the Ca2+ crosslinking density in the gel structure. The morphological characteristics, the mechanical properties, and the non-cytotoxic behavior of the CNFT-alginate gels improved bioadhesion, growth, and proliferation of the cells onto the gels. Thus, the alginate-nanocellulose gels might find applications in tissue engineering field, as for instance, in tissue repair or wound healing applications.

Preparation of Cellulose Nanofibrils from Bamboo Pulp by Mechanical Defibrillation for Their Applications in Biodegradable Composites.

There is a growing interest in cellulose nanofibrils from renewable sources for various industrial applications. However, there is a lack of information on cellulose arising from bamboo pulps. Nanofibrils from refined bamboo pulps, including bleached, unbleached, and unrefined/unbleached, were obtained by mechanical defibrillation for use in biodegradable composites. The influence of industrial processes, such as pulping and refining of unbleached pulps, as well as of alkali pretreatments and bleaching of refined pulps, on the chemical composition of the samples was analyzed. Morphological, structural, thermal, optical and viscometric properties were investigated as a function of the number of passages of refined/bleached suspensions through a defibrillator. For the unbleached suspensions, the effects of refining and bleaching on the properties of nanofibrils were evaluated, fixing the number of passages through the defibrillator. Microscopic studies demonstrated that nanoscale cellulose fibers were obtained from both pulps, with a higher yield for the refined/bleached and refined/unbleached pulp, at the expense of the unbleached/unrefined pulps. The study showed that, in addition to the effectiveness of the pre-treatments, there was an increase in the production efficiency of nanofibrils, as well as in the transparency of the bleached suspensions, while viscosity, thermal stability and crystallinity had reduced levels as the number of passages through the defibrillator increased, showing a gradual improvement in the transition from the micro- to the nano-scale. The present study contributed to the different methods that are available for the production of bamboo cellulose nanofibrils, which can be used in the production of biodegradable composites for various applications.

Monodisperse lignin fractions as standards in size-exclusion analysis: comparison with polystyrene standards.

The difficulty of preparing monodisperse lignin fractions on a large scale is a limiting factor in many applications. The present paper addresses this problem by examining the properties and size-exclusion behavior of lignin isolated by the acetosolv pulping process from post-extraction crushed sugarcane bagasse. The isolated lignin was subjected to a solvent pretreatment, followed by preparative gel permeation chromatography fractionation. The fractions were analyzed by high-performance size-exclusion chromatography (HPSEC) and these samples showed a great decrease in polydispersity, compared to the original acetosolv lignin. Several fractions of very low polydispersity, close to unity, were employed as calibration curve standards in HPSEC analysis. This original analytical approach allowed calibration with these lignin fractions to be compared with the polystyrene standards that are universally employed for lignin molecular mass determination. This led to a noteworthy result, namely that the lignin fractions and polystyrene standards showed very similar behavior over a large range of molecular masses in a typical HPSEC analysis of acetosolv lignin.

Adsorption of heavy metal ion from aqueous single metal solution by chemically modified sugarcane bagasse.

This work describes the preparation of new chelating materials derived from sugarcane bagasse for adsorption of heavy metal ions in aqueous solution. The first part of this report deals with the chemical modification of sugarcane bagasse with succinic anhydride. The carboxylic acid functions introduced into the material were used to anchor polyamines, which resulted in two yet unpublished modified sugarcane bagasse materials. The obtained materials were characterized by elemental analysis and infrared spectroscopy (IR). The second part of this reports features the comparative evaluation of the adsorption capacity of the modified sugarcane bagasse materials for Cu(2+), Cd(2+), and Pb(2+) ions in aqueous single metal solution by classical titration. Adsorption isotherms were studied by the Freundlich and Langmuir models.

Adsorção de metais pesados em serragem de madeira tratada com ácido cítrico / Heavy metals sorption on treated wood sawdust

Neste estudo, avaliou-se a capacidade da madeira Paraju (Manilkara longifolia), modificada quimicamente, para a retenção de íons metálicos. A modificação refere-se a um tratamento com ácido cítrico que leva à reação de grupos carboxilato com a celulose da biomassa. A introdução desses grupos foi observada através de espectrometria de infravermelho. Foram realizados ensaios em sistemas de batelada contendo cádmio e cobre. Os ensaios foram conduzidos em condições de equilíbrio, ajustados segundo o modelo de Langmuir. Obteve-se um carregamento máximo nos sistemas contendo apenas um metal, de 0,56 mmol-Cd/g e 0,94 mmol-Cu/g. O carregamento de cádmio reduziu-se de 0,56 mmol-Cd/g para 0,21 mmol-Cd/g, à medida que a concentração de cobre cresceu no sistema mostrando que existe uma competição entre os metais pelos grupos de troca.