Fabrication of dialysis membrane from cotton Giza 86 cellulose di-acetate prepared using Ac2O and NiCl2 as a new catalyst

This attempt has been made to synthesize the cellulose di-acetate in a solvent-free acetylation system of cotton Giza 86 cellulose with Ac₂O (200 and 300 ml) in the presence of NiCl₂^.6HO (1.0, 1.5 and 2.0 g) as an effectively available and new catalyst by the conventional reflux and microwave irradiation methods. This study also illustrates the preparation of a dialysis membrane made from a cellulose di-acetate-dichloromethane-methanol-polyethylene glycol (MW: 200) casting solution. The microwave irradiation method for the synthesis of cellulose di-acetate showed excellent yields and short reaction time, which is an important feature of this method. The impact of the two methods on the cellulose di-acetate formation and its used in the dialysis membrane formulations was studied. The experimental degree of substitution of the prepared cellulose di-acetate values (DS = 2.00-2.7) showed an agreement with the calculated values by FTIR and ¹H-NMR analysis methods. The formation of cellulose di-acetate with percentage yields varied from 62.85 to 89.85%. The applicability of the prepared membrane in dialysis operation was evaluated in terms of urea clearance, rejection of Bovine Serum Albumin (BSA) and flux of pure water. Characterization of cellulose di-acetate was achieved through ¹H-NMR, FTIR, TGA, and BET analyses. The CA-PEG blend membrane was examined by contact angle measurement, porosity, and water uptake of the membrane. The cellulose acetate membrane surface morphology was determined using SEM. It is observable that the fabricated CA-PEG blend membrane from synthesized cellulose di-acetate by using Nickel chloride as a catalyst is showing remarkable rejection of BSA and urea clearance up to 100 and 67.2%, respectively. The present work is promising and applicable in dialysis membranes.

Improvement in Acid Resistance of Polyimide Membranes: A Sustainable Cross-Linking Approach via Green-Solvent-Based Fenton Reaction

In this study, we present a facile surface modification method using green solvents for a commercial polyimide (PI) nanofiltration membrane to exhibit good acid stability. To enhance acid stability, the PI organic solvent nanofiltration membrane was modified using Fenton's reaction, an oxidative cross-linking process, using environmentally friendly solvents: water and ethanol. The surface properties of the pristine and modified PI membranes were investigated and compared using various analytical tools. We studied the surface morphology using scanning electron microscopy, performed elemental analysis using X-ray photoelectron spectroscopy, investigated chemical bonds using attenuated total reflectance-Fourier transform infrared spectroscopy, and studied thermal stability using thermogravimetric analysis. The acid resistances of the pristine and modified membranes were confirmed through performance tests. The pristine PI nanofiltration membrane exposed to a 50 w/v% sulfuric acid for 4 h showed an increase in the normalized water flux to 205% and a decrease in the MgSO₄ normalized rejection to 44%, revealing damage to the membrane. The membrane modified by the Fenton reaction exhibited a decline in flux and improved rejection, which are typical performance changes after surface modification. However, the Fenton-modified membrane exposed to 50 w/v% sulfuric acid for 4 h showed a flux increase of 7% and a rejection increase of 4%, indicating improved acid resistance. Furthermore, the Fenton post-treatment enhanced the thermal stability and organic solvent resistance of the PI membrane. This study shows that the acid resistance of PI membranes can be successfully improved by a novel and facile Fenton reaction using green solvents.

Prospecting cellulose fibre-reinforced composite membranes for sustainable remediation and mitigation of emerging contaminants

Many environmental pollutants caused by uncontrolled urbanization and rapid industrial growth have provoked serious concerns worldwide. These pollutants, including toxic metals, dyes, pharmaceuticals, pesticides, volatile organic compounds, and petroleum hydrocarbons, unenviably compromise the water quality and manifest a severe menace to aquatic entities and human beings. Therefore, it is of utmost importance to acquaint bio-nanocomposites with the capability to remove and decontaminate this extensive range of emerging pollutants. Recently, considerable emphasis has been devoted to developing low-cost novel materials obtained from natural resources accompanied by minimal toxicity to the environment. One such component is cellulose, naturally the most abundant organic polymer found in nature. Given bio-renewable sources, natural abundance, and impressive nanofibril arrangement, cellulose-reinforced composites are widely engineered and utilized for multiple applications, such as wastewater decontamination, energy storage devices, drug delivery systems, paper and pulp industries, construction industries, and adhesives, etc. Environmental remediation prospective is among the fascinating application of these cellulose-reinforced composites. This review discusses the structural attributes of cellulose, types of cellulose fibrils-based nano-biocomposites, preparatory techniques, and the potential of cellulose-based composites to remediate a diverse array of organic and inorganic pollutants in wastewater.

Thermoresponsive properties of poly(N-isopropyl,N-methylacrylamide) and its statistical and block copolymers with poly(N,N-dimethylacrylamide) prepared by B(C6F5)3-catalyzed group transfer polymerization

B(C₆F₅)₃-catalyzed GTP synthesis of poly(N-isopropyl,N-methylacrylamide) as a new thermoresponsive material.

Fouling resistant functional blend membrane for removal of organic matter and heavy metal ions

This study investigates the removal of heavy metal ions and humic acid using Cellulose acetate (CA) and Poly (methyl vinyl ether-alt-maleic acid) (PMVEMA) blend membranes. Antifouling properties of blend membranes were also investigated. Flat sheet membranes were prepared by phase inversion technique using different concentrations of CA and PMVEMA. The prepared membranes were characterized and their performance was evaluated by measuring pure water flux, water uptake capacity and humic acid removal. Rejection of humic acid (HA) was observed to be around 97% for all the blend membranes because of electrostatic interactions between the functional groups of HA and blends. The fouling characteristics of the membranes was assessed using HA as a foulant and the antifouling capacity of blend membranes was observed to be greater with a flux recovery ratio of almost 95% when compared to bare CA, commercial CA (TechInc) and other reported CA blends used for HA rejection. Also, the blend membranes were very effective in removing heavy metal ions (Pb²⁺, Cd²⁺ and Cr⁺⁶) and humic acid simultaneously. Overall, the PMVEMA modified CA membranes can open up new possibilities in enhancing the hydrophilicity, permeability and antifouling properties.

Humic acid removal using cellulose acetate membranes grafted with poly (methyl methacrylate) and aminated using tetraethylenepentamine

Graft copolymerization of cellulose acetate (CA) and poly (methyl methacrylate) (PMMA) was synthesized through free radical polymerization in the presence of cerium sulfate (CS) as initiator under nitrogen atmosphere in an aqueous solution. During the grafting reactions, the effects of polymerization time and temperature on the grafting were investigated. Furthermore, functionalization of the synthesized product was done using amine group (tetraethylenepentamine, TEPA). The results from Nuclear Magnetic Resonance (¹H NMR) spectra confirmed a successful grafting of PMMA on the CA membrane surfaces. Zeta potential (ζ), field emission scanning electron microscopy (FESEM), and atomic absorption spectrophotometer (AAS) characterization studies were done. The maximum removal efficiencies for un-grafted CA (un-g-CA), CA-g-PMMA, and CA-g-PMMA-TEPA membranes at pH of 7.0 were 34.5%, 83.3%, and 99.1%, respectively. The removal percentage results were detected to increase with increasing in the regeneration cycles. At the end of the fourth cycle, the HA removal percentages were 41.6%, 87.4%, and 99.9% for un-g-CA, CA-g-PMMA and CA-g-PMMA-TEPA membranes, respectively.

Superhydrophobic, Hybrid, Electrospun Cellulose Acetate Nanofibrous Mats for Oil/Water Separation by Tailored Surface Modification

Electrospun cellulose acetate nanofibers (CA-NF) have been modified with perfluoro alkoxysilanes (FS/CA-NF) for tailoring their chemical and physical features aiming oil-water separation purposes. Strikingly, hybrid FS/CA-NF showed that perfluoro groups are rigidly positioned on the outer surface of the nanofibers providing superhydrophobic characteristic with a water contact angle of ∼155°. Detailed analysis showed that hydrolysis/condensation reactions led to the modification of the acetylated β(1 → 4) linked d-glucose chains of CA transforming it into a superhydrophobic nanofibrous mat. Analytical data have revealed that CA-NF surfaces can be selectively controlled for fabricating the durable, robust and water resistant hybrid electrospun nanofibrous mat. The -OH groups available on the CA structure allowed the basic sol-gel reactions started by the reactive FS hybrid precursor system which can be monitored by spectroscopic analysis. Since alkoxysilane groups on the perfluoro silane compound are capable of reacting for condensation together with the CA, superhydrophobic nanofibrous mat is obtained via electrospinning. This structural modification led to the facile fabrication of the novel oil/water nanofibrous separator which functions effectively demonstrated by hexane/oil and water separation experiments. Perfluoro groups consequently modified the hydrophilic CA nanofibers into superhydrophobic character and therefore FS/CA-NF could be quite practical for future applications like water/oil separators, as well as self-cleaning or water resistant nanofibrous structures.

Preparation of cellulose-graft-polylactic acid via melt copolycondensation for use in polylactic acid based composites: synthesis, characterization and properties

MCC-g-PLA copolymer can improve the elongational viscosity of PLA at elongation rates of 0.1 s⁻¹.