Guimes Rodrigues Filho

Water state of cuprophan (hemodialysis membrane)

Abstract The system water-Cuprophan® has been studied by infrared spectroscopy, sorption isotherm and X-ray spectroscopy. It is concluded that near saturation water sorbed in the membranes has a comparable degree of association that approach that of liquid water. Similar conclusions can be derived from the form of the sorption isotherm and infrared data for water dissolved in organic solvents with a high hydrogen-bond acceptor capacity. The state of water in Cuprophan explains the larger solubility of ions and other solutes compared to Cellophan and Cellulose acetate membranes.

Synthesis and Characterization of Methylcellulose Produced from Bacterial Cellulose under Heterogeneous Condition

In this work, methylcellulose (MC) was produced from bacterial cellulose (BC), using dimethyl sulfate in a 3 h (MC3h) or 5 h (MC5h) reaction under heterogeneous conditions, with reagent substitution at each hour. MC3h showed a degree of substitution (DS) of 2.26 ± 0.13 and MC5h showed a DS of 2.33 ± 0.05. The two samples were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), differential thermal analysis (DTA), thermal gravimetric analysis (TGA), 13C nuclear magnetic ressonance (NMR) and 1H NMR techniques. The FTIR spectra of the BC and MC samples present significant differences in the regions from 3750 to 2750 cm−1 and from 1500 to 750 cm−1, which evidence the methylation of the samples. Solid state NMR spectroscopy of the MC samples was used to identify the 13C NMR signals of substitution at sites C-2, C-3 or C-6 in the glucopyranose units. The modification of bacterial cellulose produced a material with a high DS, determined by three different techniques (chemically and using the liquid 1H and solid 13C NMR spectra). These samples also demonstrate high crystallinity and thermal stability. With the MC samples synthesized in this work, transparent and resistant films were prepared and also a highly porous sponge like material.

Application of the cuprammonium process (process for the production of regenerated cellulose membranes for hemodialysis) to sugar-cane bagasse

Abstract The present report describes the extraction, purification and transformation of sugar-cane bagasse into a regenerated cellulose membrane in an attempt to produce hemodialysis membranes. Unfortunately, this process was not successful since it led to dangerously high residual levels of Cu(II). Purified sugar-cane bagasse was dissolved in ammonium copper (II) hydroxide (cuprammonium) and regenerated in the form of a membrane by successive reactions with 3 M NaOH and 2 M HCl. The following methods were used for purification: 20% EtOh/HNO 3 (v/v), 3 hr of reflux; sodium chlorite (standard method); pretreatment with 0.25 M NaOH/4.2 M EDA followed by 1.5 hr of reflux with the 20% EtOH/HNO 3 mixture (v/v). Purification was determined by iodometric analysis of the Cu(II) content in the membranes produced and by UV/Vis spectroscopy of cellulose and lignin solutions. The results obtained with the above methods were 6.18%, 4.70% and 3.67%, respectively, whereas the level obtained for industrial membranes is 0.005%. The viability of the method using sugar-cane bagasse for membrane production by the cuprammonium procedure was demonstrated. However, although the alternative purification method reduced the Cu(II) level to a percentage below that of the standard method, it also reduced the holocellulose content.

Caracterização de acetato de celulose obtido a partir do bagaço de cana-de-açúcar por ¹H-RMN

A celulose do bagaco de cana-de-acucar foi usada para sintetizar acetato de celulose com diferentes graus de substituicao, os quais foram caracterizados por 1H-RMN atraves da relacao entre as areas dos picos dos atomos de hidrogenio presentes nos grupos acetato (-(C=O)OCH3) e os picos dos hidrogenios ligados aos atomos de carbono dos aneis glicosidicos. A supressao de alguns sinais foi feita para remover sinais de ressonância da agua residual nos materiais e tambem para remover sinais de impurezas no triacetato de celulose. Um metodo de deconvolucao para o calculo computacional do grau de substituicao foi proposto. Os graus de substituicao das amostras de acetato de celulose foram 2,94 e 2,60, o que esta de acordo com os resultados por determinacao quimica atraves de uma titulacao acido base.

Cellulose triacetate films obtained from sugarcane bagasse: Evaluation as coating and mucoadhesive material for drug delivery systems.

Cellulose triacetate (CTA) films were produced from cellulose extracted from sugarcane bagasse. The films were characterized using scanning electron microscopy (SEM), water vapor permeability (WVP), mechanical properties (MP), enzymatic digestion (ED), and mucoadhesive properties evaluation (MPE). WVP showed that more concentrated films have higher values; asymmetric films had higher values than symmetric films. MP showed that symmetric membranes are more resistant than asymmetric ones. All films presented high mucoadhesiveness. From the WVP and MP results, a symmetric membrane with 6.5% CTA was selected for the coating of gellan gum (GG) particles incorporating ketoprofen (KET). Thermogravimetric analysis (TGA) showed that the CTA coating does not influence the thermal stability of the particles. Coated particles released 100% of the KET in 24h, while uncoated particles released the same amount in 4h. The results highlight the CTA potential in the development of new controlled oral delivery systems.

Avaliação das características de transporte em membranas de poliamida 66 preparadas com diferentes solventes

In the present study, polyamide 66 (PA 66) membranes were prepared by phase inversion method and characterized in order to verify their potential application in ultrafiltration processes. PA 66 membranes were prepared using two different solvents, formic acid (FA) and hydrochloric acid (HCl), and water as a non-solvent. Fourier-transform infrared spectroscopy (FT-IR) showed that the chemical structure of PA 66 was not altered by the use of solvents in the preparation of membranes. The compaction experiment with pure water performed at a pressure of 1500 kPa revealed that membranes prepared with FA undergo greater compaction of its structure and had a permeate flux value of approximately 17 L.m-2.h-1 whereas the membrane prepared with HCl had a permeate flux of 22.2 L.m-2.h-1. In the ultrafiltration experiment, both membranes had retention values around 70% for egg albumin and 80% for bovine serum albumin. Based on this result, one concludes that both membranes had nominal cut off values for application in ultrafiltration processes.

Utilização do acetato de celulose produzido a partir da celulose extraída do caroço de manga como matriz para produção de sistemas microparticulados

Cellulose acetate produced from mango seed fibers cellulose was used as a matrix for preparation of microparticles empty and load with acetaminophen (Paracetamol) in order to evaluate the incorporation of an active agent during the formation of microparticles. The microparticles are characterized by Fourier Transformed Infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM). The incorporation of paracetamol can be confirmed by the change in value of glass transition temperature (Tg). The formation of microparticles spherical was observed by SEM and showed an average diameter of 1.010 and 0.950 mm for empty and load microparticles respectively.

Alternatives for the reduction of Cu(II) ion levels in hemodialysis membranes produced from sugar-cane bagasse

Abstract The objective of the present study was to seek alternatives for the reduction of Cu(II) ion levels in hemodialysis membranes produced by the cuprammonium process. The alternatives used were: (a) replacement of the solvent Cu(NH 3 ) 4 (OH) 2 , used in the original process, with Cu(EDA) 2 (OH) 2 , and (b) increasing the reflux time of the bagasse purification process from 1.5 to 3.0 h. The experimental results were obtained by analysis of Cu(II) content in the membranes by atomic absorption, by complexometry via UV/Vis spectroscopy of the solutions of filter paper, bagasse and lignin, and by monitoring the various stages of the purification process (by FTIR and by loss of mass), i.e. pretreatment with 0.25 M NaOH followed by treatment with 4.2 M EDA and reflux with EtOH/HNO 3 (20%, v/v). The results showed that the Cu(II) content in the membranes decreased with the use of the Cu(EDA) 2 (OH) 2 solvent, that the purification process could not be improved further since cellulose degradation was observed, and that the Cu(II) content in the membranes produced was still to high for their use for hemodialysis treatment.

Caracterização de membranas assimétricas de acetato de celulose produzidas a partir do aproveitamento do resíduo da palha de milho para uso em ultrafiltração

Cellulose acetates (CA) with different degrees of acetylation were synthesized from cellulose extracted from corn stover. Membranes were prepared for the ultrafiltration process with pure polymers and blend form of CA utilizing a dioxane/acetone system. The membranes were characterized according to their transport properties. The blend form materials presented the best results for application in ultrafiltration experiments. M-TAC/DAC (corn stover triacetate and diacetate) and M-TAC/DAC-Rho (corn stover triacetate and Rhodia diacetate) presented rejection to egg albumin protein of 87.39% and 80.50%, respectively. Thus, MWCO of 45 kDa was determined for these materials.

Síntese de poliestireno sulfonado para aplicações no tratamento de água produzido a partir de copos e bandejas descartadas de poliestireno

In the present paper, the use of poly(styrene sulfonate) (PSS), produced from discarded polystyrene materials through heterogeneous and homogeneous processes, was investigated. The use of PSS for water treatment, using a kaolin suspension as wastewater model, reduced water turbidity for all the employed materials when compared to the blank analysis, without PSS. The most efficient polyelectrolyte was PSS cups obtained by homogeneous route. The same behavior was observed for real system. The homogeneous PSS cups showed a balance between a moderate molecular weight and high anionic character that improved flocks formation and water removal turbidity.