Acetosolv-solubilized lignins were characterized by their solubility in different organic solvents, Fourier transform infrared, 13 C-NMR, UV, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. Solvents having a solubility parameter in the range of 10-12.7 and a hydrogenbonding parameter in the range of 3.6-5 were considered good solvents for acetosolv lignins. Fourier transform infrared spectra of the lignins were typical for lignins containing p-hydroxy phenylpropane (H), guaiacyl (G), and syringyl (S) units. The lignins contained more conjugated and fewer nonconjugated C¼ ¼O groups, and the guaiacyl groups were etherified and condensed.13 C-NMR confirmed partial acetylation of the lignins and the presence of b-O-4 and b-5 linkages. Acetosolv lignins also showed the typical UV spectrum of annual plants.The effects of the acetic acid concentration and pulping time on the molecular weights of the lignins were explained with the presieving and condensation concepts. The thermal behavior of the acetosolv lignins was also studied.

synopsisThermal degradation of carboxymethylcellulose, cellulose acetate, grailed wood pulp, and viscose rayon have been studied using thermogravimetric analysis and differential thermal analysis. The values of rate constant K and the activation energy E were calculated from the kinetic of weight loss using the theory of the firsborder reaction. The activation energy of grafted cellulose and viscose rayon was > cellulose acetate > carboxymethylcellulose.

Thermal gravimetric analysis, and differential thermal behavior of holo‐ and hemicelluloses obtained from rice straw and bagasse were investigated. Degradation was found to be of first order reaction. The activation energy values and the rate constants were calculated from the kinetic of weight loss. Hemicellulose was found to be less stable than holocellulose, and the stability of the samples was arranged in the order, rice straw holo‐ > bagasse holo‐ > rice straw hemi‐ > bagasse hemicellulose. Degradation of rice straw (holo‐ as well as hemicellulose) was performed via two exothermic processes, whereas bagasse hemicellulose combustion was completed through three exothermic processes. The magnitude and the shape of the exotherms depend, mainly, on the chemical composition of the sample.

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Sugarcane bagasse (B), a low-cost agricultural waste, was modified via esterification and coating with polyacrylonitrile (PAN) and evaluated as a hydrophobic sorbent for diesel oil removal from artificial seawater. Esterification was carried out using stearic acid (SA) and CaO, the reaction conditions, including B:SA mass ratio, CaO concentration, reaction time and temperature were optimized. Additional hydrophobicity was achieved by coating the esterified bagasse (EB) with a hydrophobic polymer (PAN). The advantages of hydrophobicity were clearly expressed by decreased water absorption capacity and increased oil adsorption capacity. The presence of hydrophobic groups was evidenced through Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. FTIR spectroscopy showed some changes in the spectrum of B. XRD patterns indicated that the crystalline structure of B turned amorphous. SEM micrographs illustrated that the surface of EB roughened and PAN was unevenly deposited on it, which led to an increase in the surface area of both sorbents. Moreover, efficient desorption and resorption of diesel oil, paraffin oil, gasoline oil and vegetable oil were recorded in six cycles. Generally, the results are promising and the prepared sorbents can positively contribute to environmental remediation.