Zoheb Karim

Nanoporous membranes with cellulose nanocrystals as functional entity in chitosan: Removal of dyes from water

Fully biobased composite membranes for water purification were fabricated with cellulose nanocrystals (CNCs) as functional entities in chitosan matrix via freeze-drying process followed by compacting. The chitosan (10 wt%) bound the CNCs in a stable and nanoporous membrane structure with thickness of 250-270 μm, which was further stabilized by cross-linking with gluteraldehyde vapors. Scanning electron microscopy (SEM) studies revealed well-individualized CNCs embedded in a matrix of chitosan. Brunauer, Emmett and Teller (BET) measurements showed that the membranes were nanoporous with pores in the range of 13-10nm. In spite of the low water flux (64 Lm(-2) h(-1)), the membranes successfully removed 98%, 84% and 70% respectively of positively charged dyes like Victoria Blue 2B, Methyl Violet 2B and Rhodamine 6G, after a contact time of 24h. The removal of dyes was expected to be driven by the electrostatic attraction between negatively charged CNCs and the positively charged dyes.

High-flux affinity membranes based on cellulose nanocomposites for removal of heavy metal ions from industrial effluents

Fully biobased affinity membrane processing and its application in the removal of heavy metal ions from mirror industry effluents were successfully demonstrated; indicating the potential use of the ...

Phosphorylated nanocellulose papers for copper adsorption from aqueous solutions

Copper is a major problem in industrial wastewater streams, seriously affecting the quality of potential drinking water. Several approaches, including continuous membrane processes or batch-wise application of adsorbents, are in use to tackle this problem. Unfortunately, these processes suffer from their particular drawbacks, such as low permeance or disposal of saturated adsorbents. However, a combination of these processes could constitute a step towards a more efficient copper removal solution. Here, we present a nanopaper ion-exchanger prepared from cellulose nanofibrils produced from fibre sludge, a paper industry waste stream, for the efficient, continuous removal of copper from aqueous solutions. This nanopaper ion-exchanger comprises phosphorylated cellulose nanofibrils that were processed into nanopapers by papermaking. The performance of these phosphorylated nanopaper membranes was determined with respect to their rejection of copper and permeance. It was shown that this new type of nanopaper is capable of rejecting copper ions during a filtration process by adsorption. Results suggest that functional groups on the surface of the nanopapers contribute to the adsorption of copper ions to a greater extent than phosphate groups within the bulk of the nanopaper. Moreover, we demonstrated that those nanopaper ion-exchangers could be regenerated and reused and that in the presence of calcium ions, the adsorption capacity for copper was only slightly reduced.

In situ TEMPO surface functionalization of nanocellulose membranes for enhanced adsorption of metal ions from aqueous medium

The current work demonstrates an innovative approach to develop nanocellulose based membranes with high water permeability, mechanical stability and high functionality via (1) tailoring the composition of the support layer of sludge microfibers/cellulose nanofibers (CNFSL) and (2) in situ TEMPO functionalization of the thin functional layer of cellulose nanocrystals (CNCBE) to enhance the metal ion adsorption capacity. SEM studies showed a porous network structure of the cellulose support layer and a denser functional layer with CNCBE embedded within gelatin matrix. AFM studies indicated the presence of a nanoscaled coating and increased roughness of membranes surface after TEMPO modification whereas FT-IR and conductometric titration confirmed the introduction of carboxyl groups upon TEMPO oxidation. The contact angle measurement results showed improved hydrophilic nature of membranes after in situ TEMPO functionalization. High networking potential of CNFSL made the membrane support layer tighter with a concomitant decrease in the average pore size from 6.5 to 2.0 μm. The coating with CNCBE further decreased the average pore size to 0.78 and 0.58 μm for S/CNCBE and S–CNFSL/CNCBE, respectively. In parallel, a drastic decrease in water flux (8000 to 90 L MPa−1 h−1 m−2) after coating with CNCBE was recorded but interestingly in situ functionalization of top CNCBE layer did not affect water flux significantly. The increase in adsorption capacity of ≈1.3 and ≈1.2 fold was achieved for Cu(II) and Fe(II)/Fe(III), respectively after in situ TEMPO functionalization of membranes. Biodegradation study confirmed the stability of layered membranes in model wastewater and a complete degradation of membranes was recorded after 15 days in soil.

Necessity of enzymatic hydrolysis for production and functionalization of nanocelluloses

Nanocellulose (NC) from cellulosic biomass has recently gained attention owing to their biodegradable nature, low density, high mechanical properties, economic value and renewability. They still suffer, however, some drawbacks. The challenges are the exploration of raw materials, scaling, recovery of chemicals utilized for the production or functionalization and most important is toxic behavior that hinders them from implementing in medical/pharmaceutical field. This review emphasizes the structural behavior of cellulosic biomass and biological barriers for enzyme interactions, which are pertinent to understand the enzymatic hydrolysis of cellulose for the production of NCs. Additionally, the enzymatic catalysis for the modification of solid and NC is discussed. The utility of various classes of enzymes for introducing desired functional groups on the surface of NC has been further examined. Thereafter, a green mechanistic approach is applied for understanding at molecular level.

Immobilization of horseradish peroxidase on β-cyclodextrin-capped silver nanoparticles: Its future aspects in biosensor application

ABSTRACT This study aimed to work out a simple and high-yield procedure for the immobilization of horseradish peroxidase on silver nanoparticle. Ultraviolet–visible (UV-vis) and Fourier-transform infrared spectroscopy and transmission electron microscopy were used to characterize silver nanoparticles. Horseradish peroxidase was immobilized on β-cyclodextrin-capped silver nanoparticles via glutaraldehyde cross-linking. Single-cell gel electrophoresis (Comet assay) was also performed to confirm the genotoxicity of silver nanoparticles. To decrease toxicity, silver nanoparticles were capped with β-cyclodextrin. A comparative stability study of soluble and immobilized enzyme preparations was investigated against pH, temperature, and chaotropic agent, urea. The results showed that the cross-linked peroxidase was significantly more stable as compared to the soluble counterpart. The immobilized enzyme exhibited stable enzyme activities after repeated uses.

Nanocellulose as Novel Supportive Functional Material for Growth and Development of Cells

The exploration of biological polymer is a new interest due to its favorable properties used in biomedical and clinical applications. Within the used biopolymer, cellulose emerged as a most exploitable functional material at nanoscale. Working with nanosize cellulose, provides some additional advantages compare to other manmade functional polymers. The fabrication of cellulosic scaffold as a platform for growth and development of cells is a thrust area of tissue engineering but this fabricated scaffold needs to have some fundamental prerequisite before implantation in donor. Thus, this short report discusses about the NC based scaffolds for the growth and development of cells and tissue. The main focus is on derived wood and microbial NCs. Thereafter; some interesting examples will be discussed to understand the necessity of cellulose-based supports in tissue engineering field.

Green Composites: Versatile Material for Future

The growing concern towards environmental problems and the urgent need for more versatile environmental friendly materials has led to increasing attention about polymer composites, i.e. fillers/reinforcing materials coming from renewable sources and biodegradable, especially from forest. The composites usually referred to as “green”, can find several industrial applications as discussed in this chapter. Biodegradable polymers coming from natural resources are also one important constituent of green composites. This chapter provides tactic for readers regarding the materials used for the fabrication and specific application of green composites in various fields. Furthermore, a discussion of the major material attributes of green composites is provided. From these focuses, a series of balancing application properties are explained. The chapter concludes that green composites have potential for use in a number of applications, but as with all design, one must carefully match the material to the application.

Bacterial cellulose: Preparation and characterization

This chapter reports the most relevant aspects related to the isolation, production, and characterization of bacterial nanocellulose (BC). Furthermore, various used strains for high-yield production of BC were summarized. Some vital parameters (e.g., mode of culture, type of bioreactor, media, etc.) for high-yield production of BC were further exemplified. Moreover, various characterization techniques were reported to understand the physiochemical properties of BC. Specific focus has been given to morphological, structural, and mechanical characterization, to utilize these properties for further application.