Now showing 1 - 10 of 66
  • Publication
    Photocatalytic Degradation of Sugarcane Vinasse Using ZnO Photocatalyst: Operating Parameters, Kinetic Studies, Phytotoxicity Assessments, and Reusability
    Abstract: Photocatalytic degradation performance is highly related to optimized operating parameters such as initial concentration, pH value, and catalyst dosage. In this study, the impact of various parameters on the photocatalytic degradation of anaerobically digested vinasse (AnVE) has been determined through decolourization and chemical oxygen demand (COD) reduction efficiency using zinc oxide (ZnO) photocatalyst. In this context, the application of photocatalytic degradation in treating sugarcane vinasse using ZnO is yet to be explored. The COD reduction efficiency and decolourization achieved 83.40% and 99.29%, respectively, under the conditions of 250 mg/L initial COD concentration, pH 10, and 2.0 g/L catalyst dosage. The phytotoxicity assessment was also conducted to determine the toxicity of AnVE before and after treatment using mung bean (Vigna radiata). The reduction of root length and the weight of mung bean indicated that the sugarcane vinasse contains enormous amounts of organic substances that affect the plant's growth. The toxicity reduction in the AnVE solution can be proved by UV–Vis absorption spectra. Furthermore, the catalyst recovery achieved 93% in the reusability test. However, the COD reduction efficiency and decolourization were reduced every cycle. It was due to the depletion of the active sites in the catalyst with the adsorption of organic molecules. Thus, it can be concluded that the photocatalytic degradation in the treatment of AnVE was effective in organic degradation, decolorization, toxicity reduction and can be reused after the recovery process. Graphical abstract: [Figure not available: see fulltext.].
  • Publication
    Effect of operating temperature in the anaerobic degradation of palm oil mill effluent: Process performance, microbial community, and biokinetic evaluation
    This research paper presents the thermophilic anaerobic digestion (TAD) of palm oil mill effluent (POME), which is an extension of a previously conducted mesophilic anaerobic digestion (MAD) study. An anaerobic suspended growth closed bioreactor was operated at various hydraulic retention times (HRT) between 24 and 8 days. The effect of operating temperature on the performance, microbial identification, and biokinetic coefficients was evaluated. Performance was quantified by the production of biogas and the chemical oxygen demand (COD) reduction efficiency. Biogas production in TAD (64.56 L/day) was higher than MAD (46.76 L/day). A higher COD reduction efficiency was also achieved in TAD (90.90%) compared to MAD (89.66%). Other than that, more species of methanogenic bacteria were also identified in TAD through 16S rDNA. Furthermore, the modified Monod model implemented in the biokinetic evaluation revealed that higher values of maximum substrate utilization rate (rx,max) and maximum specific biomass growth rate (μmax) contributed to the better performance in TAD. The high rx,max value explains the higher COD reduction efficiency obtained in TAD. The critical retention time (θC) in TAD is also higher than MAD, making it less prone to the washout of active microbes when operating near low retention times. Additionally, TAD also achieved higher methane yield (YCH4) as opposed to MAD. The extension study concluded that the TAD of POME demonstrated improved performance in terms of biogas production and COD reduction when evaluated against the previously conducted MAD.
  • Publication
    Effect of cold exposure on the biofoam produced from different types of Oyster mushroom
    ( 2024-07)
    Tan Siu Siew
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    Nur Mawaddah Majib
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    ;
    Mycelium-based biofoam is a sustainable material derived from the growth of fungal mycelium on lignocellulosic agricultural waste substrate, as it has potential use in a variety of applications. The main objective of this research is to advance the sustainable alternatives for various application by investigating the mycelium growth of the biofoam produced from Pleurotus >lorida and Pleurotus sajor-caju on rice husk substrate, in improving the properties of the biofoam through innovative cold exposure. This study showed P. >lorida can produce mycelium biofoam at a faster rate, 7.022mm/day compared to P. sajor-caju 6.08mm/day). By cold exposure at 0°C and 10°C for 3 hours, every 2 days and 5 days, respectively until the mycelium are fully grown in the substrate, sample exposed to the latter condition for P. >lorida exhibits a faster growth rate at 7.3037 mm/day. However, cold exposure on biofoam produced from P sajor-caju had not improved the mycelium growth rate. Cold exposure samples at 0°C every 5 days and 10°C every 2 days have demonstrated capability in water (103.51%) and oil absorption (143.23%), proving their effectiveness in absorbing pollutants for the purpose of environmental remediation. The FTIR analysis con>irmed the presence of hydrophilic and oleophilic characteristics in the biofoam, indicating its capability to absorb water and oil. By subjecting biofoam to cold exposure, its properties can be altered, broadening its potential applications.
  • Publication
    Flexural and morphology properties of rHDPE/BF composites: effect of surface modification of bamboo filler by NaOH treatment
    (AIP Publishing, 2020)
    Aini Asifa Ahmad Kamal
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    ; ; ;
    Omar S. Dahham
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    N. A. Latip
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    M. U. Umar
    This study is about the effect of alkaline treatment on bamboo filler reinforced with recycle high density polyethylene (rHDPE) composites. The alkaline treatment was done by sodium hydroxide (NaOH) at three different concentrations (2.5 wt.%, 5.0 wt.% and 7.5 wt.%) for two hours at room temperature. The bamboo filler and rHDPE was compound with the extrusion method and the granule was form. The granule of rHDPE/bamboo filler composites was inject by using injection molding to produce the sample of end product. The samples of rHDPE/bamboo filler was tested using conventional universal testing machine. Field emission electron microscopy (FESEM) was used to analyze the morphology of filler and Fourier Transform Infrared Spectroscopy (FTIR) for characterization of functional group in the filler and composites. The result showed that the flexural properties of rHDPE/bamboo filler composites were slightly affected by the alkaline treatment on the bamboo filler.
  • Publication
    Bioprotein optimization from spent mushroom substrate for fish feed application
    (AIP Publishing, 2020) ;
    Z. Masyitah
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    ; ; ;
    Omar S. Dahham
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    Saad S. Dahham
    The utilization of spent mushroom substrate as potential substrate for bioprotein production is being explored in this study. The objectives of this study were to screen three different types of fungi in bioprotein production from spent mushroom substrate and to optimize the process condition of the best fungi for production of bioprotein by using Design Expert Software. In this present study, screening of three different strains; Aspergillus terreus UniMAP AA-1, Aspergillus niger (ATCC 16404) and Phanerochaete chrysosporium (ATCC 24725), was done for bioprotein production by solid state fermentation process. P. chrysosporium produced the highest amount of protein on the sixth day, with the amount of 0.3951 mg/mL. Optimization of two parameters; substrate concentration and inoculum size for the selected fungi, P. chrysosporium was done conducted by Response Surface Methodology (RSM): Central Composite Design (CCD) to investigate optimal condition of bioprotein production. The optimum condition for P. chrysosporium to produce bioprotein using SMS was achieved at 60% of substrate concentration and 15% (w/v) of inoculum size with maximum protein concentration of 0.3812 mg/mL.
  • Publication
    The effects of different bamboo filler loading on HDPE/BF composites and rHDPE/BF composites: flexural and morphology
    (AIP Publishing, 2020)
    Aini Asifa Ahmad Kamal
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    ; ; ;
    Omar S. Dahham
    ;
    M. U. Umar
    ;
    Izwan Johari
    In this article, wood plastic composite (WPC) is a composite material made up from bamboo as filler (BF) and high-density polyethylene and recycle high density polyethylene (HDPE) plastic as matrix. This research was conducted in order to investigate the mechanical properties of HDPE/BF and rHDPE/BF composites with different filler loading (5 wt.%, 10 wt.%, 15 wt.% and 20 wt.%). From the morphology test by using Field Emission Scanning Electron Microscopy (FESEM), the bonding between filler and matrix to 10 wt.% show a positive effect and have a great bonding. The, Fourier Transform Infrared Spectroscopy (FTIR) used to analyze the functional group in the bamboo filler which contain lignin, cellulose and hemicellulose. The flexural test was conducted to study the mechanical properties of rHDPE/BF composites. Based on the flexural test result, the HDPE/BF and rHDPE/BF composites with 10 wt.% BF show the highest flexural result as decreasing filler loading will reduce the strength of the composites.
  • Publication
    Tailoring polylactic acid properties for packaging applications: effects of co‐addition of halloysite nanotubes and selected plasticizers
    (Trans Tech Publications Ltd., 2020)
    Abdulkader M. Alakrach
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    ;
    Awad A. Al-Rashdi
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    Omar S. Dahham
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    Polylactic acid (PLA) has recently given a huge attention because of its mechanical properties and good physical like good biodegradability and processability, high tensile modulus and strength. In the current research, the researchers utilized sesame oil (SO) and low molecular weight polyethylene glycol (PEG) as hydrophobic and hydrophilic plasticizers, towards improvise the ductility and toughness of PLA. The researchers synthesized nanocomposites by solution casting of the neat PLA/HNTs and PLA blends with weight ratio of (0,10, 20 and 30 wt%) for PEG and (0, 5 and 10 wt%) for SO. The influence of both plasticizers on chemical, thermal and mechanical properties of the nanocomposites were investigated. Characterization of the systems was achieved by mechanical testing and thermogravimetric analysis (TGA), field emission scanning electron microscope (FESEM), Fourier transform infrared spectroscopy (FTIR). The FTIR analyses confirmed the existing of hydrogen bonding between PLA and both PEG and SO. significant improvement was shown by the plasticized nanocomposites in elongation at break with the adding of PEG and SO, meanwhile, the plasticized films’ strength were decreased. For the thermal analyses, all the films exhibited lower thermal stability compared to PLA/HNTs film.
  • Publication
    Kinetic Study of Substrate Inhibition on the Anaerobic Degradation of Sugarcane Vinasse
    Sugarcane vinasse was utilized as a substrate in thermophilic anaerobic degradation operated at hydraulic retention time (HRT) of 35 to 15 days, corresponding to organic loading rate (OLR) of 2.14 to 5.00 kg COD/m3.day. This study focuses on the soluble chemical oxygen demand (sCOD) reduction performance, kinetic evaluation through substrate inhibition model and model selection through the Akaike information criterion (AIC). The efficiency of sCOD reduction reached 84.7 % at OLR of 2.14 kg COD/m3.day and declined significantly to 51.4 % at OLR of 5.00 kg COD/m3.day. The Solver tool in Microsoft Office Excel was used to fit experimental data to the substrate inhibition models in the evaluation of the maximum specific substrate utilization rate (rxmax), substrate saturation constant (KS) and substrate inhibition constant (Ki). Model discrimination was performed using AIC and Tessier model was selected as the best fitted model with the highest likelihood of occurrence. Kinetic evaluation through the Tessier model gives: rxmax = 14.6745 /day, KS = 16.3218 and Ki = 16.9691.
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  • Publication
    Comparative study on the properties of cross-linked cellulose nanocrystals/chitosan film composites with conventional heating and microwave curing
    Cross-linking of chitosan film composites was carried out by using conventional heating and microwave curing methods in this study. Non-cross-linked and glutaraldehyde (GA) cross-linked neat chitosan and cellulose nanocrystals (CNC)/chitosan film composites were cured by either conventional oven heating or microwave irradiation. Tensile strength and Young's modulus of chitosan composites were enhanced significantly by the addition of CNC and GA especially for the microwave-cured samples. The changes in chemical interaction of the chitosan film composites was determined by Fourier transform infrared (FTIR) spectroscopy. The microwave-cured GA-cross-linked chitosan film composites were more thermally stable than non-cross-linked and conventionally heated GA-cross-linked chitosan film composites due to the formation of a more stable structure between GA and chitosan. Nevertheless, the reduced antimicrobial efficacy of film composites against Escherichia coli, Bacillus subtilis, and Saccharomyces cerevisiae was observed in cross-linked film composites compared with non-cross-linked composites.
      5  25
  • Publication
    A comparative study of microwave welding using multiwalled carbon nanotubes and silicon carbide nanowhiskers as microwave susceptors
    ( 2024-10)
    Phey Yee Foong
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    ; ; ; ; ; ; ;
    Foo Wah Low
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    Muhammad Kashif
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    Nor Azura Abdul Rahman
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    ;
    Veeradasan Perumal
    Recently, microwave welding has arisen as an advanced joining method due to its versatility and rapid heating capabilities. Among others, microwave susceptors play a crucial role in microwave welding, as different classes of microwave susceptors have distinct microwave heating mechanisms. In this work, polypropylene (PP) was utilized as a thermoplastic substrate and two types of microwaves susceptors, namely multiwalled carbon nanotubes (MWCNTs) and silicon carbide nanowhiskers (SiC NWs), were studied for microwave welding. The susceptor was first dispersed in acetone to form susceptor suspension. Next, the susceptor suspension was deposited onto the targeted area on substrate and paired with another bare PP substrate. The paired sample was then exposed to 800 W microwave radiation in a microwave oven. Afterward, the welded joint was evaluated using a tensile test and scanning electron microscopy to determine its joint strength and cross-section microstructure. The results showed that the joint strength increased as the heating duration increased. The welded joint formed using MWCNTs achieved a maximum strength of 2.26 MPa when 10 s was used, while the SiC NWs-formed welded joint achieved a maximum strength of 2.25 MPa at 15 s. This difference in duration in forming a complete welded joint can be attributed to the higher microwave heating rates and thermal conductivity of MWCNTs. However, increasing the heating duration to 20 s caused severe deformation at the welded joint and resulted in low joint strength. Overall, this study highlights the significance of understanding the microwave heating mechanism of different susceptors and provides essential insight into the selection of a microwave susceptor for microwave welding.
      27  2