Immobilized Tio2/Chitosan Layered System Incorporating Reactive Red 4 Dye For The Photocatalytic Degradation Of Phenol

An immobilized TiO2/chitosan layered system incorporating Reactive Red 4 (RR4) dye has been successfully fabricated, optimized and applied for the removal of phenol under a 45 W compact fluorescent lamp. The immobilized photocatalyst was prepared by adsorbing RR4 dye on chitosan (CS) sub-layer supported by glass plate, before being coated by TiO2 as the top layer (known as TiO2/RR4-CS/glass). Studies on the adsorption of RR4 dye by CS sub-layer showed that the highest RR4 uptake by CS/glass can be achieved at CS loading of 0.65 mg cm-2 (corresponding to 6.15 ± 0.13 μm in thickness), and pH 6.0 under room temperature (300 K). Thinner layer of CS/glass is favorable and more effective in adsorbing RR4 compared to thicker layer as it increases the surface area and porosity of CS. Langmuir and Freundlich isotherm models correlated well with the adsorption data with qmax of 86.2 mg g-1, suggesting that CS/glass is a viable mode for anchoring the dye

Chemically modified water-soluble chitosan derivatives : Modification strategies, biological activities, and applications

Chitosan, a biocompatible and nontoxic heteropolymer derived from chitin, offers various applications. However, its limited solubility above pH 6.5 hinders its broader applications. Chemical, physical, and enzymatic modifications have greatly improved chitosan properties, producing water-soluble chitosan (WSC) and derivatives. WSC and its derivatives possess unique structures, properties, and water solubility, meeting the demands of functional materials. This review highlights native chitosan characteristics, modification strategies for WSC and emphasizes its applications in food production, wastewater treatment, biomedical, and agriculture. Future perspectives for WSC and its derivatives are also discussed at the end of this paper

Insight into the photodegradation mechanism of bisphenol-A by oxygen doped mesoporous carbon nitride under visible light irradiation and DFT calculations

Oxygen doped mesoporous carbon nitride (O-MCN) was successfully synthesized through one-step thermal polymerization of urea and glucose utilizing nanodisc silica (NDS) from rice husk ash as a hard template. The CO2 gas, NH 3 and water vapor produced during the thermal process reshaped the morphology and textural properties of the of O-MCN compared to pristine mesoporous carbon nitride (MCN). Highest bisphenol A (BPA) removal achieved under visible light irradiation was 97%, with 60% mineralization ([BPA] ¼ 10 mg L�1 : catalyst dosage ¼ 40 mg L-1 ; pH ¼ 10; 180 min). In addition to mesoporosity, the sub-gap impurity states created from the oxygen doping reduced recombination rate of photogenerated carriers. Holes (h+ ) and superoxide (O2c�) were identified as the predominant active species responsible for the photodegradation process. The photodegradation route was proposed based on the intermediates detected by LC-time-of-flight/mass spectrometry (LC/TOF-MS). The Density of States (DOS) showed that oxygen doping resulted in a higher photoactivity due to the stronger localization and delocalization of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). The adsorption pathway of the BPA on the O-MCN and MCN was successfully predicted using the DFT calculations, namely molecular electrostatic potential (MEP), global and local descriptors

Enhanced photocatalytic degradation of phenol by immobilized TiO2/dye loaded chitosan

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Development of immobilized microcrystalline cellulose as an effective adsorbent for methylene blue dye removal

This article presents the work done on the utilization of microcrystalline cellulose (MCC) extracted from oil palm fronds (OPF) as a renewable and novel adsorbent. Poly (vinyl chloride) (PVC) and epoxidized natural rubber-50 (ENR-50) were used for the immobilization of MCC/ENR/PVC on the glass substrate to evaluate in a fabricated glass cell. It was revealed that the adsorption of MB dye with immobilized OPF MCC gives a maximum adsorption capacity, qmax of 12.85 mg g−1 in Langmuir isotherm. It was proposed that monolayer adsorption occurred at the homogenous surface of the immobilized OPF MCC. Besides, the adsorption process dominant physisorption that was verified by the Gibbs free energy of adsorption (ΔG°). Meanwhile, the adsorption kinetic studies revealed the coefficient of determination in Elovich model was fitted moderately resulted in physisorption, even though the experimental data was corresponded to pseudo-second order kinetic model. Additionally, the intra-particle effect was observed to be more significant at high concentration, which was shown in the increment of the rate constant with initial dye concentration. This study indicates that immobilized OPF MCC has the potential as a green adsorbent and offered the unique advantage of convenient use. Keywords: Adsorbent, Methylene blue, Microcrystalline cellulose, Oil palm frond

Kinetic study of metal ions adsorption by immobilised chitosan

Chitosan, a biopolymer produced from crustacean shells, may be used as a sorbent for metal ions removal from industrial wastewaters. This study was carried out to evaluate the efficiency of metal ions removal fromaqueous solutions using immobilised chitosan as an adsorbent in a batch adsorption system. Chitosan was immobilised on glass plates using a simple casting technique. Adsorption experiments were carried out as a function of contact time and initial metal ions concentration. The adsorption efficiency increased with increasing initial metal ions concentration (5 –20 mg L-1) and the observed trend was: Ag2+> Cu2+ > Ni2+> Fe3+> Cd2+> Zn2+.The experimental data were fitted to pseudo-first, pseudo-second-order, intra-particle, and liquid film diffusion kinetic models. The applicability of the pseudo-second-order kinetic model indicated that the adsorption behaviour was ascribed by chemisorption. Further data analysis by the diffusion kinetic models suggested that the adsorption of metal ions was controlled by more than one step:adsorption at the active sites, intra-particle, and liquid film diffusion. Overall, this work has shown the possibility of removing metal ions from water using immobilised chitosan. The use of glass plates as the solid support would facilitate the sorbent recovery during and post-adsorption process

Enhanced decolourization of methyl orange by immobilized TiO2/chitosan-montmorillonite

Many attempts have been made to improve the photocatalytic performance of immobilized photocatalysts for large-scale applications by modification of the photocatalyst properties. In this work, immobilized bilayer photocatalyst composed of titanium dioxide (TiO2) and chitosan–montmorillonite (CS–MT) were prepared in a layer-by-layer arrangement supported on glass substrate. This arrangement allows a simultaneous occurrence of adsorption and photocatalysis processes of pollutants, whereby each layer could be independently modified and controlled to acquire the desired degree of occurring processes. It was found that the addition of MT clay within the CS composite sub-layer improved the mechanical strength of CS, reduced its swelling and shifted its absorption threshold to higher wavelengths. In addition, the band gap energy of the photocatalyst was also reduced to 2.93 eV. The immobilized TiO2/CS–MT exhibited methyl orange (MO) decolourization rate of 0.071 min−1 under light irradiation, which is better than the single TiO2 due to the synergistic processes of adsorption by CS–MT and photocatalysis by TiO2 layer. The MO dye took 6 h to achieve complete mineralization and produced sulfate and nitrate ions as the by-products. Furthermore, the immobilized TiO2/CS–MT could be reused for at least ten cycles of application without significant loss of its activity