RESUMO Em virtude dos índices de produção da cana-de-açúcar, o bagaço proveniente do processamento da cana na indústria sucroalcooleira é hoje o resíduo agroindustrial produzido em maior volume no Brasil. Em 2019 foram gerados cerca de 192 milhões de toneladas deste resíduo. A utilização deste resíduo tem sido alvo de pesquisas em todo o mundo, com destaque às aplicações que visam atender as prerrogativas do conceito de economia circular. Dentro desse cenário, o bagaço de cana-de açúcar (SB) foi tratado em meio alcalino, formando um material adsorvente, SBNaOH. Os efeitos do tratamento químico foram avaliados quanto a propriedades de superfície e quanto a remoção do herbicida glifosato em meio aquoso. O fenômeno adsortivo foi estudado por meio de ensaios de isotermas. Os resultados obtidos foram ajustados aos modelos clássicos de Langmuir, Freundlich e Dubinin-Radushkevich, onde cada material adsorvente se encaixou em um modelo diferente. A caracterização indicou que o tratamento químico promoveu alteração importante na superfície do resíduo, ampliando a área superficial. SB e o SBNaOH tiveram um comportamento favorável como adsorvente e boa performance na remoção do herbicida, apresentando valores maiores que 65% de em todas as condições de trabalho. A saturação teórica de adsorção regida por Dubinin-Radushkevich (qS) foi na ordem de 8,988 mg/g (R2=0,988) para o SB aos 120 minutos de contato e capacidade máxima encontrada por Langmuir (Qmáx) foi de 13,720 mg/g (R2=0,984) para o SBNaOH aos 40 minutos de contato. O processo foi governado por troca ou partilha de elétrons. O adsorvato se distribui de forma heterogênea na superfície SB, justificando a presença sítios ativos com maior força iônica, e homogeneamente sobre a superfície (monocamada) de SBNaOH. Em geral, o bagaço de cana tratado, provindo de um resíduo agroindustrial, se mostrou um biosorvente alternativo e promissor para remoção de glifosato de sistemas aquosos, gerando assim uma nova aplicação deste resíduo.

ABSTRACT Due to the production rates of sugarcane, nowadays, the sugarcane bagasse stemming in the sugar and alcohol industry is the agro-industrial waste produced in greater volume throughout in Brazil. In 2019, about 192 million tons of this waste were generated. The use of this waste has been the aim of researches around the world, with emphasis on applications that aim to meet the prerogatives of the concept of circular economy. Within this scenario, sugarcane bagasse (SB) was treated in an alkaline medium, forming an adsorbent material, SBNaOH. The effects of chemical treatment were evaluated for surface properties and for glyphosate removal in an aqueous medium. The adsorptive phenomenon was studied through isotherm tests. The results obtained were fitted to classical models of Langmuir, Freundlich and Dubinin-Radushkevich. The characterization indicated that the chemical treatment promoted an important change in the surface of the residue, increasing the surface area. SB and SBNAOH had a feasible behavior as adsorbent and good performance in the removal of the herbicide, presenting values greater than 65% of under all working conditions. The theoretical adsorption saturation governed by Dubinin-Radushkevich (qS) was in the order of 8.988 mg/g (R2=0.988) for SB at 120 minutes of contact and maximum adsorption capacity by Langmuir (Qmax) was 13.720 mg/g (R2=0.984) for SBNaOH at 40 minutes of contact. The process was governed by the exchange or sharing of electrons. The adsorbate is distributed heterogeneously on the SB surface, justifying the presence of active sites with greater ionic strength, and homogeneously on the SBNaOH surface (monolayer). In general, the treated sugarcane bagasse, coming from an agro-industrial residue, proved to be an alternative and promising biosorbent for the removal of glyphosate from aqueous systems, thus generating a new application of this residue.

Abstract There is a great demand to develop different techniques for the continuous removal, immobilization, and remediation of metallic ions from contaminated water. Human contamination by metallic ions could even occur by ingestion of seafood causing carcinogenic and mutagenic activities. In this study, a nanofibrous membrane of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) produced by electrospinning technique and coated with polyaniline (PAni) was tested for the removal of chromium in low-concentration solutions. The viability of ZFL cells (zebrafish liver cells) was performed to evaluate the water quality enhancement after chromium adsorption. The results indicated that the nanofibrous membrane successfully adsorbed the chromium species in low-concentration ( Q e= 2.44 mg/g, at pH 4.5, room temperature (RT) and 24h) by Freundlich model and followed a pseudo-second-order kinetics model indicating a possible chemisorption in multilayers, at pH 4.5, RT and [CrVI] = 5.0 mg/L. At pH 2.0 (24h, RT and [CrVI] = 5.0 mg/L), the membrane adsorbed around 91.64% of CrVI contaminants. The thermodynamic studies revealed that the process was spontaneous and exothermic. The cells viability demonstrated the efficiency of the membrane tested in the aquatic ecosystem protection; the viability increased 19.2% in 5.0 mg/L CrVI solution. Thus, the results of this study shows that the nanofibrous membrane can be an alternative to remove low concentration of CrVI from aqueous solutions.

Abstract This paper investigated the formation of crosslinks in natural rubber compounds in the vulcanization systems: conventional (CV), semi-efficient (SEV), and efficient (EV), processed with three types of accelerators: MBTS (dibenzothiazole disulfide), TMTD (tetramethylthiuram disulfide) and CBS (n-cyclohexyl 2-benzothiazole sulfenamide). The cross-linked densities were determined by organic solvent swelling, dynamic mechanical analysis (DMA), stress vs strain, and low-field nuclear magnetic resonance, the latter being the reference technique for comparison with the other results. It was found that the choice of accelerator type influences the processing time and the cross-linked density of the vulcanizate. The four techniques showed close values of cross-linked density for natural rubber compounds, demonstrating that the analytical techniques studied can be applied to determine cross-linked density.

ABSTRACT In recent years, the technique of electrospinning has been used to develop a novel class of micro- and nanoscale materials based on fibrous structures. Several polymers, in particular elastomers, that have been implemented in this process rely on properties such as elasticity, flexibility, biocompatibility, and low cost. Herein, we describe for the first time the electrospinning of natural rubber fibers without polymeric matrix to obtain self-standing non-woven mats and oriented elastomeric fibers. The fibers average diameters were approximately 5.5 µm. Polyaniline (PAni) was deposited on the membrane surface in order to enhance the conductive properties making easy the charge transportation. We have obtained biocompatible and flexible fibrous materials using natural rubber, this research opens up possibilities of using micro and nanofibers of only-natural rubber in many applications including sensors preparation.

RESUMO As blendas poliméricas obtidas com resíduos que antes eram chamados de lixos vêm crescendo como uma solução viável, permitindo melhorias nas propriedades mecânicas e como alternativas sustentáveis. Este trabalho relata os efeitos de misturas de polietileno de baixa densidade (PEBD) e borracha natural(NR), com cinzas de bagaço de cana-de-açúcar (CBCA) como carga, com e sem polietileno-enxertado com anidrido maleico (PE-g-MA) como agente de ligação. Os comportamentos dinâmico-mecânico e a análise de tensão-deformação foram estudados. Os materiais foram avaliados por calorimetria diferencial de varredura e observações morfológicas. Os resultados mostraram que a incorporação do PE-g-MA reduziu a deformação e melhorou o estresse e o módulo Young das misturas. Além disso, a presença de SCBA aumentou a dureza, mantendo a resistência à tração e o comportamento de alongamento do polímero. Os resultados demonstram o potencial uso da CBCA na mistura de elastômeros e termoplásticos, livres de agentes de vulcanização.

ABSTRACT The polymer blends obtained with residues that before were called wastes has been growing as a viable solution, allowing improvements in the mechanical properties and as sustainable alternative. This work reports the effects of blends of low-density polyethylene (LDPE) and natural rubber (NR), with sugar cane bagasse ash (SCBA) as filler, with and without polyethylene-graft-maleic anhydride (PE-g-MA) how coupling agent. The dynamic mechanical behavior and a stress-strain analysis were studied. The materials were further evaluated by differential scanning calorimetry and morphological observations. The results showed that incorporation of the PE-g-MA reduced the strain and improved the stress and the Young module of the mixtures. Moreover, the presence of SCBA increased the hardness while maintaining the tensile strength and the elongation behavior of the polymer. The results demonstrate the potential use of SCBA in the elastomer and thermoplastic mixture, free of vulcanization agents.

The chemical structure and composition of lignin and hemicellulose, as well as the distribution between inner and outer layers of fiber, can adversely affect bleaching operations or fiber-fiber bond on pulp and, consequently the papermaking process. Herein, we have implemented the fractionation and mechanical peeling techniques in order to identify the fines composition from eucalyptus cellulose as well as to verify the effect over xylan and lignin contents and the impact on oxygen delignification. Lignin and xylans in the material removed from the fiber surface (fines) were measured around to 7.6% and 12% of the composition, respectively. The lignin value is three times higher than the percentage measured to original fiber composition (without treatment). The residual xylans content on the pulp, after treatment of fines removal and peeling, was slightly reduced, around 3% for both treatments as well as fractionation and peeling methods decrease the oxygen delignification efficiency.

Waste recycling has been the subject of numerous scientific researches regarding the environmental care. This paper reports the redirecting of sugarcane bagasse ash (SBA) as new filler to natural rubber (NR/SBA). The NR/SBA composites were prepared using an opened cylinder mixer to incorporate the vulcanization agents and different proportions of residue (SBA). The ash contains about 70-90% of inorganic compounds, with silica (SiO2) being the main compound. The SBA incorporation improved the mechanical properties of the vulcanized rubber. Based on these results, a new use is proposed for the agro-industry organic waste to be implemented in the rubber vulcanization process, aimed at improving the rubber physical properties as well as decreasing the prices of natural rubber composites.