29 research outputs found
Uveitis and gender: The course of uveitis in pregnancy
No full text10.1155/2014/401915Journal of Ophthalmology201440191
In-situ photocatalytic remediation of MTBE-contaminated water: effects of organics and inorganics
No full textThis investigation is part of a feasibility study which uses photocatalysis as a potential technology for cleaning up contaminated groundwater. It is likely that the presence of other constituents in groundwater may affect the performance of the process. Therefore, this study was conducted to investigate the effect of organic compounds and dissolved ions on the removal efficiency of a contaminant, methyl tert butyl ether (MTBE), using a reactor reported previously, Honeycomb II. Toluene, ethylbenzene and o-xylene (TEo-X), and iron, calcium, nitrate and chloride were used to represent organic and inorganic constituents, respectively, in this study. The MTBE removal efficiency decreased with increasing TEo-X concentration. The low MTBE removal efficiency at iron concentrations of 15 and 30 mg L−1 could be suppressed by the effect of chloride ion via possible mechanisms such as OH radical scavenging and/or blocking of active sites via adsorption onto the catalyst surface in acidic conditions. The MTBE removal efficiency peaked at iron concentrations of 50 mg L−1. When flowing through the reactor in a single pass, the MTBE removal efficiency of Honeycomb II increased with increasing hydraulic residence time (HRT), similar to a previous study but at lower efficiencies. When both TEo-X and dissolved ions were present, the MTBE removal efficiency remained circa 50% after 8 h operation despite the variation of TEo-X and dissolved ion concentrations. Although the catalyst was used for six experiments prior to the double pass flow experiment, about 80% MTBE removal was achieved after two passes in 48 h, in the presence of TEo-X and dissolved ions. This study demonstrated that this photocatalytic reactor can still degrade MTBE in the presence of other constituents without any process optimisation measures and reinforces its potential use for in situ groundwater remediation
Feasibility study of a photocatalytic reactor for in-situ groundwater remediation of organic compounds
No full textRemediation of groundwater contaminated by gasoline leakage from underground structures is usually complicated and costly. This work describes the use of an underground reactor, in a sand tank, placed downgradient from a simulated leakage of MTBE and other gasoline components. The reactor, Honeycomb I, is full scale in the horizontal plane. It tested the remediation of MTBE plumes at various velocities and in the presence of other gasoline compounds (toluene, ethylbenzene and o-xylene – TEo-X). The overall performance of Honeycomb I was evaluated and the efficiencies of two different experimental scales were compared. The MTBE plume was longer but narrower with increasing groundwater to MTBE velocity ratio. MTBE appeared to have a minor co-solvent effect on the TEo-X migration as TEo-X migrated at the MTBE migration rate but at significantly low concentrations. The MTBE removal efficiency decreased by about 8% in the presence of TEo-X. The scaled up Honeycomb I successfully treated 212 L of groundwater in 24 days and demonstrated its reliability over a 10-month period, achieving an overall 76% MTBE removal. In essence, this study demonstrated the potential of the immobilised photocatalytic reactor for in situ groundwater remediation, at the velocities tested in this study
In situ photocatalytic remediation of MTBE-contaminated water: Effects of organics and inorganics
No full textFeasibility study of a photocatalytic reactor for in situ groundwater remediation of organic compounds
No full textRemoval of Atrazine from Aqueous Solutions Using HNO3 Treated Oil Palm Shell-Based Adsorbent
No full textActivated carbon is a prominent material for adsorption of atrazine, however its usage is restricted due to the high cost. Thus, alternative adsorbent derived from agricultural waste has been investigated. This study focused on the feasibility of developing low-cost adsorbent from oil palm shell for removal of atrazine from aqueous solutions. The adsorbent was derived from oil palm shell using HNO3 treatment. The derived adsorbent was characterized for the surface morphology and surface chemistry using SEM and FTIR, respectively. Adsorption equilibrium experiments were carried out in batch mode to investigate the effects of adsorbent dosage, initial concentration, contact time and solution pH on the adsorption uptake of atrazine on the adsorbent. The Freundlich isotherm model showed a better correlation compared to Langmuir isotherm model to fit the equilibrium data, giving the adsorption capacity of 0.046 mg/g(l/mg)1/n at 30 oC. Atrazine solutions with pH 2 showed the highest adsorption uptake of 17.68%. The highest percentage removal was found to be 6.06% with adsorbent dosage of 2 g/200 ml. The adsorption process was found to follow the pseudo-second-order kinetic model more than the pseudo-first-order kinetic model as the correlation coefficients, R2 for the pseudo-second-order kinetic model were relatively higher for all atrazine concentrations, ranging from 0.878-0.999. The adsorbent derived was proven to be feasible in removing atrazine from aqueous solutions.
Comparison of simple and economical photocatalyst immobilisation procedures
No full textPhotocatalysis is extremely useful for the removal of organic contaminants in water. However, the conditions used for preparing and fixing the catalyst to a substrate have a great effect on its performance. The determination of a suitable immobilisation procedure for specific application becomes more complicated with a plethora of methods developed over the years. The aim of this paper is to determine a suitable titanium dioxide immobilisation procedure using an economical and simple method. Various dip coating alternatives are compared: sol-gel, reverse micelles, hybrid and TiO2 slurries. The coatings were evaluated in terms of deposition and photocatalytic activity, by weight and methylene blue demineralisation, respectively. A hybrid coating on woven fibreglass exhibited the highest amount of deposition and photocatalytic activity. Five coating cycles calcined at 500 degrees C for I h are sufficient in obtaining a favourable coating performance. SEM images showed that woven fibreglass, coated 5 times and calcined at 500 degrees C for 1 h, was well coated. However, some cracking and detachment was observed. The hybrid procedure outlined above will be applied in subsequent studies in our research on removal of groundwater contaminants. This work may be useful to researchers by providing the relative performance of different dip-coating alternatives tested under identical conditions
Synthesis and characterization of biocoal from Cymbopogon citrates residue using microwave-induced torrefaction
No full textEffect of Mercerization and Acetylation on Properties of Coconut Fiber and its Influence on Modified Bitumen
No full textCoconut fiber, one of many types of natural fibers, is an agricultural waste which is left unutilized after the coconut fruits and juice are extracted. In this research, the effect of the different chemical treatments on the morphological, chemical and physical properties of coconut fiber and its influence on the properties of the modified bitumen were studied. The mercerization effectively altered the surface morphology and reduced the diameter of the coconut fiber. The waxy layer present on the surface of
the coconut fiber was significantly reduced after mercerization. Acetylation reported minor reduction on the waxy layer and did not cause any significant changes on the diameter of the coconut fiber. The chemical characterization reported that the hemicelluloses were present only on the surface of the natural coconut fiber whereas the peak of Fourier Transform Infrared spectra associated with the presence of waxes was observed for natural and chemically treated coconut fibers. The bitumen modified with chemically treated coconut fibers exhibited lower penetration values and higher softening point. From the analyses of
penetration value, softening point and penetration index, the bitumen modified with 10% NaOH and 50% CH3COOH treated
coconut fibers resulted in enhanced properties for paving binders to be used in warmer region
Encapsulated biochar-based sustained release fertilizer for precision agriculture: A review
No full textThe excessive use of conventional fertilizers leads to environmental issues associated with the loss of nutrient through leaching, volatilization, denitrification and surface run-off. Biochar-based fertilizer has gained much research interest as it can be used as a slow release fertilizer. Biochar-based fertilizer can alleviate the properties of soil to slow down the nutrient release rate. However, the sustained release mechanism of biochar-based fertilizer is still facing limitations. As a solution to mitigate this issue, the integration of encapsulating technology and biochar-based fertilizer has been introduced to improve the sustained release mechanism. This paper presents an extensive overview on the various formulations of biochar-based fertilizer and encapsulated biochar-based fertilizer. Additionally, the influence of the inorganic mineral, polymer and hydrogel-based fertilizers on the nutrient release behaviour are also critically discussed. The various methods used to synthesize the fertilizers and their effects on soil amendment are also discussed in detail. This paper could be used as a good source of information on the current advances and future perspectives of encapsulated biochar-based sustained release fertilizer for precision agriculture.The authors acknowledge the research grant provided by Universiti Malaysia Sarawak under Cross Disciplinary Research Grant [ F02/CDRG/1830/2019 ].Scopu
