Toward pulping process for enhancing the RS-black liquors as precursor of activated carbons for aqueous adsorbent purposes.

This work deals with providing a green pulping process of rice straw with zero waste discharged, via valorization of its by-product as a promising precursor for production of carbon nanostructures. The carbon nanostructures (BL-CNSs) from rice straw pulping liquors (BLs) are prepared in one step with phosphoric acid activation. The carbon nanostructures (BL-CNSs) from rice straw pulping liquors (BLs) are prepared in one step with phosphoric acid activation. The optimal pulping approach for achieving effective adsorbent (BL-CNSs) of cationic and anionic dyes is recommended from using different BLs precursors resulting from different reagents (alkaline, neutral, and acidic reagents). The carbon precursors are characterized by elemental, thermal (TGA and DTG) and ATR FTIR analyses. While the impact of pulping route on performance of CNSs is evaluated by their adsorption of iodine, cationic dye and anionic dye, as well as ATR-FTIR, textural characterization, and SEM. The data of elemental analysis displayed a high Carbon content ranges from 57.85 to 66.69% suitable for CNSs preparation, while the TGA showed that Sulphur-containing BLs (Kraft, neutral sulfite and acidic sulfite) have higher degradation temperature and activation energies as compared with other BLs. The optimum BL-CNSs adsorbent is prepared from the disposed neutral sulfite black liquor, with the following characteristics: cationic dye adsorption capacity 163.9 mg/g, iodine value 336.9 mg/g and SBET 310.6 m2/g. While the Kraft-CNSs provided highest anionic adsorption (70.52 mg/g). The studies of equilibrium and kinetic adsorption of dyes showed that the adsorption equilibrium of all investigated BL-CNSs toward MB follow the Langmuir and mainly Freundlich models for BB adoption. Their adsorption kinetics are a good fit with the pseudo-second-order model. The textural characterization and SEM revealed the CNSs exhibit a mixture of mesoporous and microporous structure.

Molecular Weight Determination of Aloe Polysaccharides Using Size Exclusion Chromatography Coupled with Multi-Angle Laser Light Scattering and Refractive Index Detectors.

Background: Size exclusion chromatography (SEC)/refractive index (RI) were used to determine molecular weight (MW) and molecular weight distributions (MWD) of polysaccharides. In aloe product research and quality control, commercially available pullulan and dextran are most commonly employed as calibration standards. Significant difference in the MW and MWD were found in literature when different methods were used. Objectives: This study was to investigate the traditional methods and more recent technologies used to determine the MW and MWD of Aloe vera polysaccharides. Methods: In this study, multi-angle laser light scattering (MALS) detection was studied on three polysaccharides, 1, 2, and 3, that were isolated and purified from A. vera leaf. The chemical structures of 1-3 were characterized as 1, 4-ß-linked glucomannans by monosaccharide composition and glycosidic linkage analysis. Absolute MW and root-mean-square radius were determined by MALS on the isolated aloe polysaccharides. The conditions to obtain reliable results from MALS measurement were examined. Results: MALS analysis demonstrates that the 1, 4-ß-linked glucomannan adopt the conformation of random coils or hard spheres in the analytical environment of a 0.1 M NaCl solution. Non-size exclusion effects and interactions between polysaccharide molecules were also observed in some aloe polysaccharides in the current analysis. The weight-average MW obtained by MALS measurement for 1, 2, and 3 are 55, 129, and 962 kDa, respectively. Comparing the results with SEC/RI calibrated by pullulan and dextran standards, marked differences in the MWD are found. Both overestimated the MW of 1 and 2 by factors of 4.4 and 4.2, and 2.4 and 1.6, when using dextran and pullulan calibration, respectively. Using pullulan calibration underestimated the MW of 3 by a factor of 3.1, but a similar result was obtained from dextran calibration compared to MALS measurement. The two isolated aloe polysaccharides were employed to be broad calibration standards or to be combined with narrow polydispersity pullulan calibration standards. Several aloe samples were tested using the different calibration curves, and the determined MWs were compared with the results obtained by MALS measurement. Conclusions: The results clearly indicated that until true polysaccharide standards become available MW and MWD's will be simply relative to the standards employed and the technologies used.

Chemical Investigation of Major Constituents in Aloe vera Leaves and Several Commercial Aloe Juice Powders.

Background: There are a substantial number of papers in the scientific literature reporting on the chemical composition of the Aloe vera plant. None of these investigations are truly comprehensive nor address the differences in composition that occur through processing variations in fresh leaves and commercially available product forms. Objectives: This work was to analytically examine a range of these forms and compile the findings. Methods: Fresh A. vera leaves and a number of commercial aloe juice powders were investigated for their major chemical constituents. Samples included fresh leaves from China and Mexico, plus commercial powders from different manufacturers made from different plant parts and/or manufacturing processes. The test results include moisture, ash, fiber, protein, lipids, minerals, organic acids, free sugars, and polysaccharides. The analytical methods employed comprise inductively coupled plasma-optical emission spectroscopy for minerals, high-performance anion-exchange chromatography equipped with pulsed amperometric detection for free sugars, HPLC for organic acids, and size exclusion chromatography (SEC)-multi-angle laser light scattering (MALS)-differential refractive index (dRI) for polysaccharide analyses. The absolute MW and MW distribution were determined using MALS measurement. Results: The major constituents of A. vera fresh leaf are fibers, proteins, organic acids, minerals, monosaccharides, and polysaccharides, which accounted for 85-95% of the total composition determined. In the commercial powdered aloe juice samples, four major components-organic acids, minerals, monosaccharides, and polysaccharides-accounted for 78-84% of the total composition. Apart from the four major components, products manufactured by ethanol precipitation contained high amounts of fiber and protein, while the free sugars were removed. In ethanol-precipitated products, the polysaccharide MW was less affected by manufacturing conditions and the concentration of aloe polysaccharides was higher than in products made in the nonethanol manufacturing processes. The overall chemical profiles were found to be consistent, except for the MW and content of polysaccharides in the commercial aloe samples analyzed, which were largely dependent on the types of manufacturing processes employed. Conclusions: This present study provides a comprehensive investigation of the major chemical composition of A. vera leaf and commercially derived products. The use of the SEC combined with MALS and differential RI detectors has proved to be an improved tool for the accurate determination of polysaccharide MW and contents of the various commercially available A. vera products in this study.