Wan Izhan Nawawi

Kinetics of photocatalytic decolourization of cationic dye using porous TiO2 film

Abstract In this work, the kinetics of the photocatalytic decolourization of methylene blue (MB) is investigated using different surface morphologies of multilayer TiO2 coating onto a glass plate under irradiation from a 55-W household florescent lamp. A simple direct dip-coating technique was used, and the coating properties of TiO2 powder were improved by adding epoxidized natural rubber (ENR) as an organic binder in the coating formulation. The effects of the fundamental parameters that govern the kinetics of the photocatalytic decolourization of MB, such as the mass of TiO2 coated onto the glass plate, the pH and the TiO2 surface morphology, were also studied. The kinetics of the MB decolourization in all cases was found to be pseudo-first-order kinetics and was fitted to the Langmuir–Hinshelwood model. The degraded part of the ENR binder led to generating pores within the surface of the TiO2/ENR film and converting it into porous form, as confirmed by SEM analysis. Furthermore, TGA, FTIR and leachability analyses were conducted to further confirm the depletion of the ENR from the TiO2/ENR film. The kinetics of the MB decolourization and the efficiency of the MB colour removal indicated that the porous TiO2/ENR film becomes approximately twice as fast as the non-porous TiO2/ENR film.

Fabrication and Characterization of Porous Activated Carbon from Coconut Shell by Using Microwave-Induced KOH Activation Technique

Coconut shell-based activated carbon (CSAc) was prepared by chemical activation method using microwave-induced KOH technique. The activation process was successfully carried out with varying microwave power ranging from 100 to 1000 W and impregnation ratio of 1.0 to 3.0. The surface area, pore sizes, surface morphology and specific capacitance of the produced activated carbon were analyzed by using an automatic quantachrome instrument (Autosorb1C) volumetric sorption analyzer, scanning electron microscope (SEM) and automatic battery cycler. The optimum activation power and impregnation ratio were found at 600 W and 1.5, respectively. The resulted product, C3 has maximum surface area and specific capacitance value of 1768.8 m2 g-1 and 156.33 F g-1 respectively, with carbon yield of 58 %.

Multi-Cycle Photodegradation of Anionic and Cationic Dyes by New TiO2/DSAT Immobilization System

In this work, titanium dioxide (TiO2) photocatalyst was generally immobilized onto glass plate support material by employing double sided adhesive tape (DSAT) as a thin layer binder. The photocatalytic performance of this new non-additive immobilization system was observed under the degradation of two different charges of dyes namely anionic reactive red 4 (RR4) and cationic methylene blue (MB) dyes. Photocatalytic degradation of RR4 and MB dyes under immobilized TiO2/DSAT were compared with TiO2 in suspension mode respectively. Immobilized TiO2/DSAT was observed to have up to 30 cycles of reusability thanks to DSAT that is able to provide a very strong intact between the glass plate and TiO2 layers. In fact, a better photodegradation activity was observed by number of photocatalysis cycles due to increasing pores formation on TiO2 surface as observed by Scanning Electron Microscopy (SEM) analysis.

Characteristics and Thermal Behaviour of Low Rank Malaysian Coals towards Liquefaction Performance via Thermogravimetric Analysis

In this study, thermal behaviour of two low-rank Malaysian coals namely Mukah Balingian (MB) and Batu Arang (BA) were obtained under pyrolysis conditions via Thermogravimetric analysis (TGA) at a heating rate of 20°C min-1. The thermal characteristics of the coals were investigated prior to direct liquefaction in order to determine the liquefaction performance, i.e. coal conversion and oil yield. The differential weight loss (DTG) results for both coals showed that there are three main stages evolved which consists of moisture, volatile matter and heavier hydrocarbons that correspond to temperature range of 150, 200-500 and 550-800°C, respectively. Apparently, the DTG curves of BA coal reveals a similar pattern of thermal evolution profile in comparison to that of the MB coal. However, the calculated mean reactivity of BA coal is higher than that of MB, which implied that BA would probably enhance coal conversion and oil yield in comparison to MB coal. Interestingly, results showed that under the same liquefaction conditions (i.e. at 4MPa pressure and 420°C), conversion and oil yield of both coals were well correlated with their reactivity and petrofactor value obtained.

Crystallinity, Tapping and Bulk Density of Microcrystalline Cellulose (MCC) Isolated from Rice Husk (RH)

The isolation of microcryostalline cellulose (MCC) from rice husk (RH) via acid hydrolysis process has been successfully prepared by using different molarity of nitric acid (HNO3) and hydrochloric acids (HCl). The properties of MCC obtained such as tapping and bulk densities, thermal stability and percentage crystallinity were studied. Tapping and bulk densities shown comparable results regardless of different acid used that reflecting the potential of MCC as reinforcement filler in composite fabrication. The usage of 2M HNO3 gives highest percentage crystallinity (69%) in comparison with 2M HCl (49%). The result indicates the stability of MCC-RH obtained using HNO3 has great potential to replace strong acid in acid hydrolysis process.

The Effect of Reactive Red 4 Dye as a Sensitizer in Enhancing Photocatalytic Activity of TiO2 for Degradation of Methyl Orange

In this work, anionic RR4 dye was used to sensitize TiO2/PVA and TiO2/PEG immobilized system in enhancing photocatalytic degradation of anionic methyl orange (MO) dye. 0.3g of TiO2 and polymer binder was coated onto a clean glass plate by using brush technique to develop optimum immobilize TiO2 system. A comparison study between immobilized TiO2/PVA (Im/TiO2/PVA) and immobilized TiO2/PEG (Im/TiO2/PEG) system with and without RR4 sensitizer were carried out under 55-W fluorescent lamp and visible light irradiation. The photocatalytic degradation of MO was significantly enhanced for both RR4 dye sensitized Im/TiO2/PVA and Im/TiO2/PEG with first order rate constant was ca. 0.080 min-1 and 0.071 min-1 respectively under 55-W fluorescent lamp. Same observation as well under visible light irradiation whereby enhanced of those RR4 sensitized immobilized photocatalysts were recorded as compared with immobilized photocatalysts without RR4 as sensitizer. The photocatalytic enhancement under Im/TiO2/PVA/RR4 and Im/TiO2/PEG/RR4 are due to the ability of RR4 dye to become electron (e-) donor for conduction band (CB) of TiO2, thus making TiO2 CB riches with electron, eventually this e is used to remove MO dye by producing hydroxyl radical.

Nitrogen Doped TiO2 Prepared under Microwave Irradiation: Effect of Different Irradiation Light

A visible light active nitrogen (N) doped TiO2 was prepared using commercially available TiO2 P25. In this study, a simple N doped TiO2 was prepared by mixing of TiO2 powder with urea as N precursor under microwave irradiation instead of normal using muffle furnace as heating media. Prepared N doped TiO2 samples shows active under visible light irradiation due to lower band gaps energy of N doped TiO2 observed by UV/Vis-DRS. U3-800 was found as optimum N doped where photodegradation rate of RR4 dye under is 1.6 times faster compared with unmodified TiO2 as well as control TiO2 under normal 55-W fluorescent lamp. An active photo response under visible light was observed from U3-800 with 80 minutes of time irradiation to complete RR4 color removal, while no photocatalytic degradation was observed from unmodified and control TiO2.As a result, this study contributed to purification of effluent specifically toxic dyes with complete mineralization under visible light irradiation. For the future work, the modification of TiO2 with nitrogen and metal doping will indirectly increase the efficiency of photodegradation under visible light. In future, the immobilized technique can also be applied for N doped TiO2 to overcome the reusability issue.

Carbon Coated TiO2 and it Application on Photodegradation of 4-Chlorophenol under Solar Irradiation

The photocatalytic degradation of 4-Chlorophenol (4CP) using carbon C coated TiO2 (C-TiO2) and pristine TiO2 under solar irradiation was carried out in a suspension mode under custom made glass cell reactor with continuous aeration supply. It was found that 0.3 and 0.6 g were the optimum loading for C-TiO2 and pristine TiO2 respectively in the degradation of 20 mg L-1 4CP under solar irradiation. The optimum C-TiO2 was found six times faster than pristine TiO2 based on pseudo first order rate constant of 4CP photodegradation. No adsorption was observed in the photocatalysts. The intermediates observed during this photocatalytic degradation process were maleic acid, hydroquinone (HQ), benzoquinone (BQ), 4-chlorochetol (4CC) and resorcinol.

Extraction of Oil from Jatropha curcas L. Seed and Kernel at Supercritical Hexane via High-Temperature High-Pressure Batch Wise Reactor System

Extraction of oil from Jatropha curcas L. seed and kernel using hexane as solvent was performed at supercritical state of hexane; temperature from 200-280 °C, pressure from 4-12 MPa, with fixed 30 min extraction time, sample ratio to solvent 1:40 (w/v), and 300 rpm in a 1-liter high-temperature high-pressure batch wise reactor system. The percentages of oil yield from seed and kernel obtained via supercritical hexane were 67.2 and 81.2 %, respectively. The percentages of oil yield increase with increasing in pressure and temperature. The percentages of oil yield via supercritical hexane extraction were much better compared to soxhlet extraction (i.e. seed, 37 % and kernel, 48 %) and mechanical pressing techniques (i.e. seed, 30 % and kernel, 25 %). Oils extracted were derivatized into FAMEs before quantified using GC-MS. The results showed that maximum oil yield was obtained at temperature 280 °C, pressure 12 MPa, whereby oleic acid is the most abundance (43.4 %) followed by linoleic acid (29 %), palmitic acid (20.1 %) and stearic acid (7.5 %). Comparison extraction with soxhlet and mechanical pressing showed that the percentages of FAMEs distributions are similar in all extracts and they agree with the previous data obtained by other researchers.

Effect of Carbon and Nitrogen Modified TiO2 on Photoluminescence Property and Photocatalytic Activity

Carbon (C) and Nitrogen (N) modified TiO2 photocatalysts were prepared by using two different precursors namely peat and urea using commercial TiO2-P25. The results from HR-TEM and XPS analyses shows different interactions between C-TiO2 and N-TiO2 photocatalysts where C is only coated on top of TiO2 while N is chemically bonded in TiO2 particle. Higher photocatalytic activity for both C and N modified TiO2 were observed under degradation of reactive red 4 dye (RR4) with the degradation rate were c.a 2.5 and 2.7 times faster compared with pristine TiO2. The photoluminescence (PL) analysis data showed the lowest PL intensity over C coated TiO2 followed by pristine TiO2 while N doped TiO2 exhibited the highest PL intensity. The lowest PL intensity of C coated TiO2 was due to the presence of C as electron acceptor while the highest PL intensity for N doped TiO2 was due to the oxygen vacancies and TiO2 defect structure.