S. Sabar

Microcrystalline cellulose: Isolation, characterization and bio-composites application-A review.

Considering its widespread usage in various fields, such as food, pharmaceutical, medical, cosmetic and polymer composites industries, microcrystalline cellulose (MCC) is becoming impellent due to increasing demand of alternatives to non-renewable and scarce fossil materials. Although it still suffers from some drawbacks, MCC has recently gained more interest owing to its renewability, non-toxicity, economic value, biodegradability, high mechanical properties, high surface area and biocompatibility. New sources, new isolation processes, and new treatments are currently under development to satisfy the increasing demand of producing new types of MCC-based materials on an industrial scale. Therefore, this review assembles the current knowledge on the isolation of MCC from different sources using various procedures, its characterization, and its application in bio-composites. Challenges and future opportunities of MCC-based composites are discussed as well as obstacles remaining for their extensive uses.

Photocatalytic decolourisation of Reactive Red 4 dye by an immobilised TiO2/chitosan layer by layer system

The synergistic photocatalysis-adsorption processes by the immobilized TiO(2)/chitosan layer by layer system on a glass support (TiO(2)/CS/glass) were investigated for the decolourisation of Reactive Red 4 (RR4) dye solution. Effects of different reaction parameters such as TiO(2) loading, initial pH of the solution, visible light, dissolved oxygen and radical quenchers were studied. The decolourisation rate of RR4 by TiO(2)/CS/glass was more than 32 times faster than a single layer of TiO(2) but was highly dependent on the TiO(2) loading and the initial pH of the solution. A thin layer of TiO(2) and acidic conditions favoured the adsorption of RR4 at the TiO(2)/CS interface. The h(+)/OH() species that diffused from the TiO(2) layer into the TiO(2)/CS interface oxidised the chemisorbed RR4 anions at the interface, and the generated electrons were then transferred to the conduction band of TiO(2). Excess electrons in the conduction band of TiO(2) increased the number of superoxide ions produced and thus improved the photocatalytic decolourisation of RR4. Therefore, apart from the synergistic photocatalysis-adsorption processes, a charge transfer process was also found to be responsible for maintaining the efficiency, sustainability and reusability of the TiO(2)/CS/glass layer by layer system.

Photocatalytic removal of Reactive Red 4 dye by immobilised layer-by-layer TiO2/cross-linked chitosan derivatives system

AbstractThe synergistic photocatalysis–adsorption processes of immobilised TiO2/chitosan (TiO2/CS/glass) layer-by-layer systems have been improved by the cross-linking of the chitosan (CS) sub-layer with different cross-linkers, namely epichlorohydrin (ECH) and glutaraldehyde (GLA). The immobilised layer-by-layer system was applied for the removal of an anionic Reactive Red 4 (RR4) dye solution in the presence of air and light irradiation under a 45-W compact fluorescent lamp. Based on the results, the pseudo-first-order rate constant of the TiO2/CS-ECH/glass was more than two times faster compared to the TiO2/CS-GLA/glass. But as the pH decreases, the TiO2/CS-GLA system showed higher photocatalytic performance due to its better mechanical and optical properties compared to the TiO2/CS-ECH system. In addition, the TiO2/CS-GLA system showed excellent reusability with complete removal of the RR4 dye from the first to at least four cycles of extended usage.

Microwave-assisted preparation of mesoporous-activated carbon from coconut (Cocos nucifera) leaf by H3PO4 activation for methylene blue adsorption

ABSTRACT Mesoporous-activated carbon was prepared from fallen coconut (Cocos nucifera) leaf, an agricultural waste through a microwave-induced H3PO4 activation process. The characterization of the coconut leaf–activated carbon (CAC) was evaluated through the iodine number, ash content, bulk density, and moisture content. Fourier transform infrared spectroscopy, scanning electron microscope, Brunauer–Emmett–Teller (BET) surface area, X-ray diffraction, and pHPZC. CAC has a mesopore content of 84% with an average pore size of 36.5 Å and a large BET surface area of 632 m2/g. The uptake properties of the CAC with methylene blue was evaluated at different CAC dosage levels (0.2–10 g/L), initial pH (3–10), methylene blue concentration (50–350 mg/L), and time (0–360 min) using batch mode operation. The kinetic profiles were described by the pseudo-second-order kinetics. The equilibrium data were well fitted to the Langmuir model with a maximum monolayer adsorption capacity of 250 mg/g at 30°C. Thermodynamic functions indicate a spontaneous and exothermic nature of the adsorption process. This study indicates that coconut leaves are a promising renewable precursor that can be utilized to develop an efficient mesoporous-activated carbon.