DESIGN, CHARACTERIZATION AND ENHANCED BIOAVAILABILITY OF HYDROXYPROPYLCELLULOSE-BASED NOVEL BIOCONJUGATES FOR INCLUSION OF A FLUOROQUINOLONE ANTIBIOTIC – GEMIFLOXACIN

Polysaccharides are beneficially used as drug carriers via prodrug formation and offer a mechanism for better effectiveness and delivery of the drug. The unique geometry of hydroxypropylcellulose (HPC), a polysaccharide, allows the attachment of drug molecules with a higher degree of substitution. Therefore, HPC-gemifloxacin conjugates, i.e., macromolecular prodrugs, were synthesized using acylation reagents, i.e., tosyl chloride and carbonyldiimidazole using N,N-dimethylacetamide as a solvent. The reactions were carried out at 80 °C under stirring for 24 h in inert environment. This strategy of reaction appeared efficient to obtain a high degree of drug substitution (DS = 0.42-1.34) on the polymer parent chain, as calculated by UV-visible spectrophotometry after hydrolysis of the samples. The method provides high efficacy as product yields were high (71-76%). Macromolecular prodrugs with different DS of gemifloxacin (GEM) designed were found soluble in organic solvents. The pharmacokinetic studies showed that the t1/2 and tmax values of GEM from HPC-GEM conjugate were considerably higher, which indicates improved bioavailability of the drug after conjugate formation.

PERFORMANCE OF UREA/NaOH AS A GREEN SOLVENT IN DISSOLVING RECYCLED CELLULOSIC FIBER FINES RESIDUES

Using lignocellulosic materials for producing more value-added bioproducts is an attractive mission. Fiber fines, which represent an important part of the wastes generated by paper recycling mills, have been considered in the current research. Dissolving these lignocellulosic residues in environmentally friendly and inexpensive solvents can be a great achievement. For this purpose, the performance of urea/sodium hydroxide in dissolving printing and writing pulp (RPW) fines was investigated. Although using sodium hydroxide alone had a positive effect on the dissolution of recycled printing and writing pulp (RPWP) fines, the addition of urea increased the dissolution of fines from 23% to 56%. Different levels of urea consumption had no significant effect on the dissolving process. The performance of the urea/sodium hydroxide system in dissolving fines suspensions with different concentration (1, 3 and 5%) showed that reducing the concentration leads to an increase in fines dissolution (56, 36 and 7%, respectively). The results of FTIR confirmed the presence of cellulose without any hemicelluloses and lignin in the dissolving part. The results of X-ray diffraction analysis of soluble cellulose showed that the type-I cellulose structure probably changed to type-II cellulose. No reduction in the DP of dissolved cellulose and the integrated structure of the final cellulosic film confirmed by the FE-SEM images affirmed the successful dissolution of the RPWP fines in this system.

EFFECT OF CHITOSAN ADDITION DURING PAPER-MAKING ON AGEING STABILITY OF DOCUMENT PAPER

The aim of the present work has been to study the influence of chitosan addition into the composition of paper intended for documents on its ageing stability, with a view of enhancing the resistance of paper strength and optical properties over time. The chitosan solution was added during the formation of the paper sheets in various amounts: 0.2%, 1% and 2% o.d.f. Paper samples of different fibrous compositions were prepared from bleached sulphate softwood pulp (BSWP) and bleached sulphate hardwood pulp (BHWP) in the following ratios: 50% BSWP:50% BHWP, 80% BSWP:20% BHWP, 100% BSWP and 100% BHWP. Then, paper samples were subjected to accelerated thermal ageing for 24 hours at 105 °C. It was found that the use of chitosan as additive in the composition of bleached cellulose paper samples led to improved strength and hygroscopic properties. The study showed that chitosan could be used in the production of kraft document papers comprising aluminium sulphate, as the presence of aluminium sulphate had no negative effect on the action of the biopolymer. Regarding the complex evaluation of the properties of the obtained papers, it could be summarized that, for the studied fibrous compositions, the optimum amount of the additive was 1% chitosan for a fibrous composition of 50% bleached softwood pulp and 50% bleached hardwood cellulose. Therefore, preparing document paper with the addition of chitosan is a convenient procedure to enhance a number of paper properties, even after the ageing process.

DEVELOPMENT OF ACID MODIFIED CELLULOSE ACETATE MEMBRANES FOR SALT WATER TREATMENT

The main objective of this work has been to study the performance of membranes developed for water treatment. Polymeric membranes (CTP and CTP-Acid) were developed from solutions containing cellulose acetate (CA), cellulose triacetate (CTA) and polysulfone (PSF), using maleic acid (MA) and acetic acid (AA) as additives and chloroform/dioxane as solvent. The NIPS-type phase inversion method was chosen as the membrane film manufacturing technique. The incorporation of 2.5% and 5% by weight of acids in the membrane mixture allowed us to study the additive effect on the morphological structure, and to predict the performance of the membranes formed. The characterization of the membranes was performed by SEM and FTIR analyses. Examining the flux, permeability and selectivity of the membranes also permitted to study the efficiency and performance of each membrane. The addition of AA and MA additives within the mixture increased the hydrophilic character and improved the flux rate by increasing it from 75 Lm-2h-1 to 142.74 Lm-2h-1 for 5% maleic acid addition. The 5% CTP AA membrane gave very satisfactory results in terms of selectivity, with a maximum removal of 84% of NaCl salt. Therefore, this membrane has been considered to be the most efficient one, with a flux of 120 Lm-2h-1 to 15 bar and a NaCl salt retention that meets the standards required by the World Health Organization (WHO).

REACTIVE DYE PRINTING ON COTTON FABRIC USING MODIFIED STARCH OF WILD TARO CORMS AS A NEW THICKENING AGENT

This study investigated the use of a thickening agent derived from modified starch of wild taro corms in the screen printing of cotton fabric using reactive dye. The best conditions for developing the print paste and steaming time in order to obtain maximum color yield were established. The results revealed impressive color fastness properties in the printed samples; although, the printed fabric possessed slightly lesser tensile and tear strength, in comparison with the unprinted fabric. The printed fabric also exhibited increased bending stiffness properties. Largely, this study reveals that the printing paste containing the thickening agent derived from carboxymethyl starch within wild taro corms can be utilized in the printing of cotton fabric using reactive dye.

COMPARISON OF STINGING NETTLE ADSORPTION PERFORMANCE TOWARDS ANIONIC AND CATIONIC DYES

Stinging nettle was used as lignocellulosic adsorbent for the removal of cationic dye – malachite green (MG), and anionic dye – Congo red (CR), from aqueous solution, without any chemical pretreatment. The adsorption equilibrium data fitted well with the Langmuir model for the adsorption of both dyes, with the calculated maximum adsorption capacity of 270.27 mgg-1 and 172.14 mgg-1 for MG and CR, respectively. The adsorption process was controlled by the pseudo-second-order model in the adsorption of MG and by the pseudo-first-order model in the adsorption of CR. The thermodynamics modelling displayed that the process was spontaneous and endothermic. The π–π electron–donor interaction, hydrogen bonds and pore diffusion may also be effective, besides electrostatic interaction between the adsorbate and the adsorbent in the mechanism of MG and CR uptake.

SEPARATION OF HEMICELLULOSES FROM AN INDUSTRIAL STREAM BY NANOFILTRATION AND ULTRAFILTRATION PROCESSES

The performance of nanofiltration (NF) and ultrafiltration (UF) membranes was studied for separating hemicelluloses from a highly alkaline industrial stream, containing 17-18 wt% sodium hydroxide, resulting from the viscose process. Initially, screening experiments were performed to select suitable membranes, which were then investigated on a pilot scale spiral module. Screening experiments showed that the UF membrane, with a nominal molecular weight cut-off (MWCO) value of 3 kDa, and the NF one, with a nominal MWCO value of 0.5 kDa, showed a similar range of filtration performance and a flux of 4.2 L/m2.h. Further, a retention efficiency of 50% was observed for the 5 kDa and the 10 kDa membranes, indicating absence of any significant proportion of hemicelluloses in this range of molecular weights. The effects of process conditions were studied to understand their correlation with membrane performance with respect to hemicelluloses retention and permeate flux. UF membranes were found to be more prone to performance deterioration over time and with the number of cycles of usage during the pilot scale study, whereas the NF membrane showed consistent performance. It was seen that feed dilution can improve the membrane performance with respect to sodium hydroxide recovery. Significant reduction in feed viscosity with dilution resulted in a 50% increase in flux after normalizing for concentration.

EFFICIENT ADSORPTION OF Ce (III) ONTO POROUS CELLULOSE/GRAPHENE OXIDE COMPOSITE MICROSPHERES PREPARED IN IONIC LIQUID

A novel adsorbent made of porous cellulose/graphene oxide composite microspheres (PCGCM) was synthesized in [Bmim]Cl ionic liquid. The as-prepared PCGCM was evaluated for the removal of Ce (III) via static adsorption experiments. The results showed that the adsorption equilibrium of Ce (III) onto PCGCM was achieved within 50 min and the adsorption was highly pH dependent. An excellent adsorption capacity as high as 415.1 mg•g-1 was obtained at a pH of 4.9, which was much higher than most adsorbents reported in the literature. The pseudo-second order kinetic model and Langmuir isotherm model were found to fit the adsorption behavior of PCGCM well. The XPS analysis confirmed that the adsorption was based on the ion exchange mechanism. Meanwhile, PCGCM could be regenerated with 1 mol•L-1 HCl for repetitious adsorption of Ce (III). This work provides an attractive approach for the removal of rare earth ions as pollutants.

UTILIZATION OF WATER HYACINTH FOR DYE EFFLUENT PURIFICATION

Water hyacinth (Eichhornia crassipes) (WH) is an invasive plant floating freely on the water, which is widely spread in tropical and subtropical regions. The plant is characterized by high porosity and a high number of functional groups, such as hydroxyl (-OH), carboxyl (–COOH), and amino groups (–NH2). Activated carbon, which is widely accepted on an industrial level for the adsorption of dyes from wastewaters, is a highly expensive material. Thus, in this research, a bioadsorbent material was prepared based on WH biomass and investigated as an alternative tool for water quality remediation, in the case of dye pollutants (RR HE3B). The WH plants were collected from the nearby Lake Tana and used as an adsorbent material without chemical treatment. The batch adsorption test was performed by varying the pH of the solution, adsorbent dosage and initial dye concentration. The powdered WH and RR HE3B dye loaded WH were characterized using FTIR, revealing the emergence of new stretching vibration peaks in the range from 2800 to 3000 cm-1 on the spectrum of Reactive Red HE3B (RR HE3B) dye loaded WH, confirming that -CH and -CH2 were responsible for the adsorption. The analysis of the adsorption isotherm and of the suitability of different models for describing it has led to the following order: Freundlich > Langmuir > Temkin > Dubinin-Radushkevich, based on their correlation coefficient value. This implies that the WH adsorbent surface is heterogeneous and the adsorption of the dye onto it depends not only on the specific reaction sites, as the n-value of the Freundlich constant confirms that the physical adsorption process might be favored. Therefore, WH could be a potential alternative adsorbent to remove the RR HE3B dye from dye polluted wastewaters.

OPTIMIZATION OF XYLAN EXTRACTION PROCESS FROM RICE STRAW FOR PRODUCTION OF AUTOHYDROLYSATES RICH IN PREBIOTIC XYLOOLIGOSACCHARIDES

Rice straw, an abundant agricultural waste, possesses immense potential to serve as renewable, eco-friendly and non-edible feedstock to generate value-added products. Therefore, the present study aimed to obtain prebiotic neutral xylooligosaccharides (XOS)-rich autohydrolysate from rice straw xylan. The central composite design of response surface methodology was employed to optimize the conditions for the alkaline extraction of xylan, i.e. NaOH concentration (6-14%, w/v), reaction time (1-3.5 h) and temperature (50-100 °C). Autohydrolysis of xylan was carried out at 121 °C and 15 psi for varied hydrolysis times (10, 25 and 40 min) and sulphuric acid concentrations (0.1, 0.5 and 1.0M) to obtain XOS-rich autohydrolysate. The optimum conditions were found to be as follows: 11.04% (w/v) NaOH, 3.126 h and 80.146 °C, so that the maximum xylan yield of 19.97% was predicted by the software. This value was quite close to the experimental yield of 19.4%, with 80.83% xylan being recovered per gram of rice straw. The best autohydrolysis treatment for xylan was found to be using 0.1M sulphuric acid for 10 min, which allowed 34.5% of 100 mg xylan to be depolymerized to produce neutral XOS (degree of polymerization up to 7), with xylose, xylobiose and xylotriose constituting 4.45, 10.14 and 7.83 mg, respectively. These autohydrolysates promoted higher growth of Lactobacillus rhamnosus and Lactobacillus casei than established prebiotic fructooligosaccharides. The study attempts to solve disposal issues of rice straw through production of XOS-rich autohydrolysates in demand on the global nutraceuticals market.