Now showing 1 - 10 of 49
  • Publication
    Bioinspired Crosslinked Nanocomposites of Polyvinyl Alcohol-Reinforced Cellulose Nanocrystals Extracted from Rice Straw with Ethanedioic Acid
    ( 2022-01-01)
    Chin K.M.
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    ; ; ;
    Tan W.K.
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    Vannaladsaysy V.
    In this study, cellulose nanocrystals (CNC) were extracted from rice straw and incorporated into polyvinyl alcohol (PVOH) as reinforcement nanofillers. Multiple nanocomposites with different CNC contents were prepared. Extracted CNC appear as long, well-defined rodlike crystals with a high aspect ratio (41). Nanocomposites with 3 wt% of CNC significantly exhibit improved tensile strength (60.4%) and maximum degradation temperature (287°C). Moreover, they demonstrate a decrease in water vapor permeability rate and in the swelling and solubility indices of PVOH/CNC. Significant improvements were observed when nanocomposites were crosslinked specifically in terms of tensile strength (104.8%) and maximum degradation temperature (364°C). They also demonstrate greatly reduced water vapor permeability rate, swelling, and solubility indices. The optimum CNC amount for both nanocomposites is 3 wt%.
  • Publication
    Revealing the influences of functional groups in azo dyes on the degradation efficiency and power output in solar photocatalytic fuel cell
    ( 2020-12-01)
    Khalik W.F.
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    ; ; ;
    Yusoff N.A.
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    Lee S.L.
    In this study, the degradation efficiency and electricity generation of the azo dyes affected by the functional groups and molecular structure in a solar photocatalytic fuel cell (PFC) system were investigated and discussed in detail. Four different azo dyes such as, Acid Orange 7 (AO7), Acid Red 18 (AR18), Reactive Black 5 (RB5), Reactive Red 120 (RR120) with different molecular structure were evaluated. The degradation efficiency of AO7, AR18, RB5 and RR120 achieved 5.6 ± 0.3%, 11.1 ± 0.6%, 41.9 ± 0.9% and 52.1 ± 1.3%, respectively, after 6 h irradiated under solar light. In addition, the maximum power density, Pmax for AO7, AR18, RB5 and RR120 was 0.0269 ± 0.01, 0.111 ± 0.03, 1.665 ± 0.67 and 4.806 ± 1.79 mW cm−2, respectively. Meanwhile, the concentration of COD for AO7, AR18, RB5 and RR120 reduced to 16 ± 0.1, 10 ± 0.3, 7 ± 0.6 and 3 ± 0.9 mg L−1, respectively. The concentration ratio of benzene / naphthalene, benzene / azo bond and naphthalene / azo bond, respectively, was analyzed to investigate the impact of the functional groups over photodegradation of the azo dyes in PFC. Electron releasing groups (-OH and –NH2) and electron withdrawing groups (-SO3Na) which attached to the naphthalene or benzene ring also played a pivotal role in the degradation mechanism.
  • Publication
    Synergistic Effect Between Iron and Food/Microorganism (F/M) Ratio in Biological Wastewater Treatment
    ( 2022-01-01)
    Subramaniam L.S.
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    ; ; ; ;
    Siripatana C.
    Biological wastewater treatment is mainly dependent on the actions of microorganisms that can be used to treat wastewater. Microorganisms will start to stick together when they degrade the organic matter in wastewater for food and flocculate to settle the pollutants. This study aimed to investigate the effect of food to microorganism (F/M) ratio and iron in a biological process using aerobic treatment. For this purpose, four aerobic tanks (A, B, C, D) were set up using activated sludge as the seed sludge, air pump as air diffuser to provide oxygen to the system, and three litres of synthetic medium as carbon source for each tank. A specific amount of iron (II) sulfate was added into tanks B, C, and D with the weight of 3 g, 6 g, and 9 g, respectively. Tank A act as a control, and no iron dosage was added. The F/M ratio for tanks A, B, C, and D were 0.8, 0.5, 0.4, and 0.3 mg BOD/mg MLVSS, respectively. The aerobic tanks were operated for 40 days in sequential batch mode and sampling was collected four times per week to observe the COD and MLVSS. This study has found that Tank D shows the best performance compared to all tanks with 84.71% COD removal efficiency and a fivefold increment of microorganism growth rate. These findings suggest that a relationship exists between the iron and F/M ratio to enhance the aerobic treatment process.
  • Publication
    Effects of magnesium ions in microbial cells adhesion of attached growth system for the enhancement of biogas production
    This research aims to improve the biogas production by employing cell immobilisation technique under thermophilic conditions. The thermophilic fermentative biogas production was carried out by immobilising the anaerobic sludge obtained from palm oil mill treatment plant on granular activated carbon (GAC) in repeated batch mode. Different concentration of magnesium ions (Mg2+) (0.25, 0.5, 0.75, 1.0 and 1.5 g/l) on biogas production was investigated at 60°C with an initial sucrose concentration of 5 g/l as feedstock. The effect of Mg2+supplementation at the initial stage of immobilisation process is important to increase the formation of biofilm in the attached growth system. This study had found that Mg2+could enhance the biogas production capacity with optimum Mg2+concentration of 0.75 g/l.
  • Publication
    Biodegradation improvement of bioinspired crosslinked and noncrosslinked polyvinyl alcohol nanocomposites with cellulose nanocrystals extracted from rice straw through natural soil burial exposure
    ( 2022-10-01)
    Chin K.M.
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    ; ; ;
    Tan W.K.
    Polyvinyl alcohol with different cellulose nanocrystals (CNC) content extracted from rice straw were prepared by using solution casting method and their biodegradability in natural soil burial were studied. Ethanedioic acid (EA) was introduced as a crosslinker. The synthesized noncrosslinked and crosslinked PVOH/CNC nanocomposites films and their biodegradation were characterized with Fourier transform infrared spectroscopy (FTIR), tensile test, weight loss, Field Emission Scanning Electron Microscopy (FESEM), differential scanning calorimetry (DSC). The changes in chemical properties before and after biodegradation were confirmed through FTIR. Tensile test revealed that the tensile strength and elongation at break reduced as time of soil burial increases. Morphological study showed the extent of surface deterioration before and after soil burial, where the addition of CNC displayed greater deterioration. Melting temperature and crystallinity increased with addition of CNC but decreased after crosslinking. However, melting temperature and crystallinity of all nanocomposites increased after biodegradation. PVOH degrading bacteria were isolated and identified to be Bacillus cereus strain CCM 2010 and Bacillus cereus strain ATCC 14579. Biodegradation of the bionanocomposites were concluded to be in the following decreasing order: PVOH/CNC > PVOH/EA/CNC > PVOH > PVOH/EA.
  • Publication
    Pilot scale single chamber up-flow membrane-less microbial fuel cell for wastewater treatment and electricity generation
    ( 2017-04-06)
    Thung W.E.
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    ; ; ; ;
    Oon Yoong Ling
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    Oon Yoong Sin
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    Harvinder Kaur Lehl
    Pilot scale up-flow membrane-less microbial fuel cell (UFML-MFC) was constructed to study feasibility of the bioreactor for simultaneous degradation of organic substance and electricity generation. The performance of the UFML-MFC was evaluated with different anode electrode (cube carbon felt and stacked carbon felt) in terms of voltage output, chemical oxygen demand (COD) and Coulombic efficiency (CE). Carbon flake were used as cathode in the UFML-MFC. UFML-MFC was operated in three stages where included batch-fed, end of batch fed and semi-continuous. The Cube carbon felt as anode have the better performance in terms of voltage output and electricity generation in all 3 stages. Maximum voltage output was 0.311 ± 0.004 V at 75% of COD reduction and thus CE was 0.15%. The result shows the operational mode is the key to improve the voltage output and also COD reduction.
  • Publication
    Sustainable utilization of anthraquinone-rich Rheum officinale as electron shuttle in microbial fuel cell: Strategy for stimulating monohydric phenols degradation and bioelectricity generation
    In an aim to completely degrade refractory phenolic compounds for effective wastewater treatment, a sustainable strategy using anthraquinone-rich herbal plant contents as electron shuttles is presented. This study is the first attempt of treating four different chemical structures of monohydric phenols, while simultaneously generate low-carbon electricity in a microbial fuel cell. An electron shuttle-mediated strategy was introduced to investigate the effect of electron shuttle against the degradation of phenolic pollutants and bioelectricity generation, by employing Rheum officinale extract as electron shuttle. Results revealed that there was a two-fold increase in chemical oxygen demand (COD) removal, degradation extent of phenol and cresol isomers, output voltage and power density of MFC, compared to the mediator-free MFC system. The degradation of phenol yielded higher COD removal, degradation efficiency, output voltage and power generation over cresol isomers, with and without the application of electron shuttle. A complete removal of COD and phenol, with output voltage of 620.06 mV and power density of 252.49 mW/m2 were obtained. Phenol outperformed cresol isomers with regard to its sole activating hydroxy (−OH) group, lower dipole moment and higher electronic conductivity (8.53 mS/cm). Conversely, meta-cresol exhibited the lowest removal efficiency and power generation, ascribed to greater inductive influence of methyl group in meta position on the dissociation energy of the − OH group. Moreover, detection of the phenolic intermediates by gas chromatograph-mass spectrometer analysis was conducted, and detailed degradation pathways were presented.
  • Publication
    Caffeine-containing wastewater treatment and bioelectricity generation in up-flow constructed wetland-microbial fuel cell: Influence of caffeine concentration, operating conditions, toxicity assessment, and degradation pathway
    ( 2022-04-01)
    Teoh T.P.
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    ; ; ; ;
    Oon Y.L.
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    Tan S.M.
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    Ong Y.P.
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    Yap K.L.
    This study explored the potential of caffeine being utilized as the fuel for the microbes to produce electrons for electricity generation in up-flow constructed wetland-microbial fuel cell (UFCW-MFC). The effect of caffeine concentration was investigated to identify the availability of UFCW-MFC in the conversion of caffeine to electrons for electricity production; and the effect of operating conditions (circuit connection, supplementary aeration, and plant) was studied to determine their significance in the treatment of caffeine containing wastewater. The UFCW-MFC achieved about 98% of decaffeination efficiency regardless of caffeine concentration; while a decrease of efficiency was observed when UFCW-MFC operated without supplementary aeration and plant (~93%). COD removal efficiency decreased correspondingly to the increase of caffeine concentration, which could be contributed by the higher concentration of caffeine and its intermediates. The degradation pathway of caffeine in UFCW-MFC was explored in this study. It was remarkable that ammonia was produced and converted to ammonium ions during caffeine catabolism. Supplementary aeration and macrophyte play a crucial role in removing excess caffeine, intermediates as well as accumulated ammonium ions. The toxicity assessment revealed that caffeine was degraded to less toxic products. The closed circuit connection not only contributed to electricity generation but also enhanced the caffeine and COD removal efficiency by 4.6 and 5.4% in the anaerobic region, respectively. The increase of voltage and maximum power density from phase I to phase IV indicated that caffeine could be converted to electrons by the anaerobes for electricity production.
  • Publication
    Enhanced photodegradation of phenol by ZnO nanoparticles synthesized through sol-gel method
    ( 2017-12-01)
    Nik Noor Athirah Nik Yusoff
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    ; ; ;
    Wan Fadhilah Khalik
    ;
    Fahmi Ridzwan
    Zinc oxide (ZnO) utilization in advanced oxidation process (AOP) via solar-photocatalytic process was a promising method for alternative treating wastewater containing phenol. The ZnO photocatalyst semiconductor was synthesized by sol-gel method. The morphology of the ZnO nanostructures was observed by using scanning electron microscope (SEM) and the crystallite phase of the ZnO was confirmed by x-ray diffraction (XRD). The objective of this study was to synthesis ZnO nanoparticles through a sol-gel method for application as a photocatalyst in the photodegradation of phenol under solar light irradiation. The photodegradation rate of phenol increased with the increasing of ZnO loading from 0.2 until 1.0 g. Only 2 h were required for synthesized ZnO to fully degrade the phenol. The synthesized ZnO are capable to totally degrade high initial concentration up until 45 mg L-1 within 6 h of reaction time. The photodegradation of phenol by ZnO are most favoured under the acidic condition (pH3) where the 100% removal achieved after 2 h of reaction. The mineralization of phenol was monitored through chemical oxygen demand (COD) reduction and 92.6% or removal was achieved. This study distinctly utilized natural sunlight as the sole sources of irradiation which safe, inexpensive; to initiate the photocatalyst for degradation of phenol.
  • Publication
    Intermolecular degradation of aromatic compound and its derivatives via combined sequential and hybridized process
    ( 2023-03-01)
    Lau Y.Y.
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    ; ; ; ;
    Teng T.T.
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    Eng K.M.
    The under-treated wastewater, especially remaining carcinogenic aromatic compounds in wastewater discharge has been expansively reported, wherein the efficiency of conventional wastewater treatment is identified as the primary contributor source. Herein, the advancement of wastewater treatments has drawn much attention in recent years. In the current study, combined sequential and hybridized treatment of thermolysis and coagulation–flocculation provides a novel advancement for environmental emerging pollutant (EP) prescription. This research is mainly demonstrating the mitigation efficiency and degradation pathway of pararosaniline (PRA) hybridized and combined sequential wastewater treatment. Notably, PRA degradation dominantly via a linkage of reaction: thermal cleavage, deamination, silication and diazene reduction. Thermolysis acts as an initiator for the PRA decomposition through thermally induced bond dissociation energy (BDE) for molecular fragmentation whilst coagulation–flocculation facilitates the formation of organo-bridged silsesquioxane as the final degradation product. Different from conventional treatment, the hybridized treatment showed excellent synergistic degradability by removing 99% PRA and its EPs, followed by combined sequential treatment method with 86% reduction. Comprehensive degradation pathway breakdown of carcinogenic and hardly degradable aromatic compounds provides a new insight for wastewater treatment whereby aniline and benzene are entirely undetectable in effluent. The degradation intermediates, reaction derivatives and end products were affirmed by gas chromatography–mass spectrometry, Fourier transform infrared spectroscopy and ultraviolet–visible spectrophotometry (GC–MS, FTIR and UV–Vis). This finding provides valuable guidance in establishing efficient integrated multiple-step wastewater treatments. Graphical abstract: [Figure not available: see fulltext.].