Sherif M.A.S. Keshk

Effect of different alkaline solutions on crystalline structure of cellulose at different temperatures

Effect of alkaline solutions such as 10% NaOH, NaOH/urea and NaOH/ethylene glycol solutions on crystalline structure of different cellulosic fibers (cotton linter and filter paper) was investigated at room temperature and -4°C. The highest dissolution of cotton linter and filter paper was observed in NaOH/ethylene glycol at both temperatures. X-ray patterns of treated cotton linter with different alkaline solutions at low temperature showed only two diffractions at 2θ=12.5° and 21.0°, which belonged to the crystalline structure of cellulose II. CP/MAS (13)C NMR spectra showed the doublet peaks at 89.2 ppm and 88.3 ppm representing C4 resonance for cellulose I at room temperature, Whereas, at low temperature the doublet peaks were observed at 89.2 ppm and 87.8 ppm representing C4 resonance for cellulose II. Degree of polymerization of cellulose plays an important role in cellulose dissolution in different alkaline solutions and temperatures, where, a low temperature gives high dissolutions percentage with change in crystalline structure from cellulose I to cellulose II forms.

New catalyst with multiple active sites for selective hydrogenolysis of cellulose to ethylene glycol

Three different metals were successfully incorporated into the mesoporous siliceous material, TUD-1, for the first time. One-pot synthesis was applied to incorporate isolated Al3+, nanoparticles of WO3, and nanoparticles of metallic Ni with different loadings into TUD-1. The prepared materials were characterized by means of elemental analysis, XRD, N2 physisorption, NH3-TPD, SEM, EDX and TEM. Characterization data confirmed the incorporation of isolated Al3+ ions in the framework of TUD-1, in addition to metallic Ni (3–5 nm) and WO3 (10–15 nm) nanoparticles inside the pores of TUD-1 matrix. Moreover, extra-framework WO3 particles (0.5–1 μm) were also detected. The catalytic activity of the prepared samples was evaluated in the selective hydrogenolysis of cellulose into ethylene glycol at 503 K under 4 MPa of H2 pressure in the presence of water as a solvent. The catalyst with the multiple active sites exhibited the highest cellulose conversion (100%) after reaction for 90 min and the ethylene glycol yield was 76%.

Cellulase Application in Enzymatic Hydrolysis of Biomass

Biomass is biological material derived from living organisms including plant, animal, and vegetable-derived material. Biomass is carbon based and is composed of a mixture of organic molecules containing C, H, O, N, and also small quantities of other atoms, including alkali, alkaline earth, and heavy metals.

Enhancing biocompatibility of some cation selective electrodes using heparin modified bacterial cellulose

Bacterial cellulose (BC) and heparin-modified bacterial cellulose (HBC) were utilized to enhance the biocompatibility of highly thrombogenic PVC-based potassium and calcium membrane electrodes. Three types of membrane electrodes were prepared: (1) conventional PVC electrode (control), (2) PVC-based electrode sandwiched with bacterial cellulose membrane (BC-PVC), and (3) PVC-based electrode sandwiched with heparin-modified bacterial cellulose membrane (HBC-PVC). The potentiometric response characteristics of the modified potassium and calcium membrane electrodes (BC-PVC and HBC-PVC) were compared with those of the control PVC-based potassium and calcium selective electrode, respectively. Response characteristics of the modified membrane electrodes were comparable to the control PVC membrane electrode. The platelet adhesion investigations indicated that (BC) and (HBC) layers are less thrombogenic compared to PVC. Therefore, use of BC or HBC would enable the enhancement of the biocompatibility of PVC-based membrane electrodes for potassium and calcium while practically maintaining the overall electrochemical performance of the PVC sensing film.

Natural biodegradable medical polymers: Cellulose

Abstract Cellulose probably is an important polymer for several products in our life. We are going to understand its chemical structure, formation, and its degradation. In this chapter, we will scope on its usage in medical field owing to its importance.

Natural bacterial biodegradable medical polymers

Bacterial cellulose (BC) has significant advantages over natural cellulose. BC fibrils can be oriented in regular or randomly depending on type of incubation (static, shaking, or agitated). BC generated as a never-dried membrane from static culture is a nearly pure form that contains 99.1 wt% water of which 0.3 wt% is bound and 98.8wt% is free of water. It has more than 200 times greater surface area than isolated softwood cellulose and has a tensile strength similar to that of steel. Many potential high-value markets exist for thin film BC, including acoustic diaphragms, artificial skin, artificial blood vessels, supersorbers, and specialty membrane. Unfortunately, the current price of media and the low production rate of BC limit the commercial usage of it. The potential markets for BC include foods and mining (Nata de coco) and pulp paper industries (as additives to enhance paper properties). A new market and important one is usage in the medical field. Bacterial synthesized cellulose was designed tubular directly during the cultivation with the aim to develop biomaterials. These formed products were implicated as covers in experimental micro nerve surgery and artificial blood vessels. In all, review articles written on BC have been concerned the nature of cellulose structure and biosynthesis and its applications. There is no book that gathers all topics about BC, which can assist the beginner or the advanced people to understand what BC is. In this chapter, we will explore it in detail in three parts. The first part will consider the historical, occurrence, mechanism of production of BC; the second part will concern about the degradation of BC; and finally BC application in medical field.

Grafting of Cellulose Extracted from Kenaf Using Xanthate Method

Mass spectra of reconstructed ion chromatogram (MRIC) technique are used to follow up the grafting copolymerization of 1-vinyl-2-pyrrolidinone (VP), 1-vinyl-3-anisylidine-2-pyrrolidinone (VAP) and ethylmethacrylate (EMA) and cellulose extracted from kenaf using xanthate method. Grafting is carried out under ionic and/or free radical mechanism conditions. Factors affecting grafting yield such as temperature, sodium hydroxide concentration, liquor ratio, carbon disulfide concentration, monomer and grafting time have been studied.