Displaying publications 121 - 140 of 951 in total

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  1. Utilization of Malaysia EAF slags for effective application in direct aqueous sequestration of carbon dioxide under ambient temperature
    Omale SO, Choong TSY, Abdullah LC, Siajam SI, Yip MW
    Heliyon, 2019 Oct;5(10):e02602.
    PMID: 31667417 DOI: 10.1016/j.heliyon.2019.e02602
    Iron and steel industries are among the contributors of CO2 emission in large volume into the atmosphere, causing detrimental effects to the environment and the ecosystem at large scale. These industries also generate solid wastes in the form of electric arc furnace (EAF) slag during operations which result in about 10-15% slag wastes per ton of steel produced. In this study, the EAF slags from an iron and steel-making factory in Klang, Malaysia was utilized for CO2 sequestration through direct aqueous mineral carbonation. According to the surface area analysis, the fresh EAF slag has a mesoporous structure, its elemental composition shows the presence of 20.91 wt.% of CaO that was used for the sequestration of CO2 through carbonation. The sequestration capacity was found to be 58.36 g CO2/kg of slag at ambient temperature in 3 h, with the liquid/solid (L/S) ratio of 5:1 and using <63μm particle size. Moreover, the shrinking core model (SCM) was used to analyze the solid-fluid reaction in a heterogeneous phase and the CO2 sequestration shows to be controlled by the product layer phase. The EAF slag is demonstrated to have the potential of CO2 sequestration at ambient temperature.
  2. Optimization of the antioxidant-rich xanthone extract from mangosteen (Garcinia mangostana L.) pericarp via microwave-assisted extraction
    Mohammad NA, Abang Zaidel DN, Muhamad II, Abdul Hamid M, Yaakob H, Mohd Jusoh YM
    Heliyon, 2019 Oct;5(10):e02571.
    PMID: 31667409 DOI: 10.1016/j.heliyon.2019.e02571
    Total phenolic content (TPC) and antioxidant properties of xanthone extract from mangosteen pericarp via microwave-assisted extraction (MAE) method was optimized by response surface methodology (RSM). The MAE extraction conditions to obtain optimum antioxidant-rich xanthone extract were at 2.24 min of irradiation time, 25 mL/g of solvent-to-solid ratio and 71% of ethanol concentration. The predicted results for four responses were as follows; 320.31 mg gallic acid equivalent/g extract, 83.63% and 93.77% inhibition (DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2'-Azino-bis-3-ethylbenzthiazoline-6-sulfonic acid) assays), and 144.56 mg Trolox equivalent/g extract (FRAP, Ferric reducing antioxidant power). The predicted and actual values were statistically insignificant (P > 0.05). Therefore, these results confirmed that the examined model was acceptable and relevant. MAE led to a slightly similar antioxidant capacity and a higher extraction of α-mangostin, a major xanthone of mangosteen pericarp as compared to water bath-maceration technique.
  3. Fulltext Extension of planned behavioral theory to consumer behaviors in green hotel
    Bashir S, Khwaja MG, Turi JA, Toheed H
    Heliyon, 2019 Dec;5(12):e02974.
    PMID: 31872131 DOI: 10.1016/j.heliyon.2019.e02974
    This study aims to contribute to the development of an extended theory of planned behavior to understand the indicators of consumer behavior. A conceptual framework highlighting four study constructs (i.e., personal norms, intention towards green hotels, environmental consciousness, and green consumer behavior) was tested using 394 general Malaysian lodging consumers. The findings indicate that to devise green branding strategies for the hotels, the managers must first consider how the environmental consciousness of consumers positively affects their personal norms and behavior towards green hotels. Second, consumers' personal norms and behavioral intention towards environmentally responsible lodging positively affect their green behavior. Third, Personal norms mediates the significant positive relationship between; environmental consciousness and behavioral intention towards environmentally responsible lodging of a consumer; and environmental consciousness and green consumer behavior. Lastly, behavioral intention towards environmentally responsible lodging mediates the significant positive relationship between a consumer's personal norms and green consumer behavior.
  4. Fulltext The de novo transcriptome of workers head of the higher group termite Globitermes sulphureus Haviland (Blattodea: Termitidae)
    Hussin NA, Najimudin N, Ab Majid AH
    Heliyon, 2019 Dec;5(12):e02969.
    PMID: 31872129 DOI: 10.1016/j.heliyon.2019.e02969
    The subterranean termite Globitermus sulphureus is an important Southeast Asian pest with limited genomic resources that causes damages to agriculture crops and building structures. Therefore, the main goal of this study was to survey the G. sulphureus transcriptome composition. Here, we performed de novo transcriptome for G. sulphureus workers' heads using Illumina HiSeq paired-end sequencing technology. A total of 88, 639, 408 clean reads were collected and assembled into 243, 057 transcripts and 193, 344 putative genes. The transcripts were annotated with the Trinotate pipeline. In total, 27, 061 transcripts were successfully annotated using BLASTX against the SwissProt database and 17, 816 genes were assigned to 47, 598 GO terms. We classified 14, 223 transcripts into COG classification, resulting in 25 groups of functional annotations. Next, a total of 12, 194 genes were matched in the KEGG pathway and 392 metabolic pathways were predicted based on the annotation. Moreover, we detected two endogenous cellulases in the sequences. The RT-qPCR analysis showed that there were significant differences in the expression levels of two genes β-glucosidase and endo-β-1,4-glucanase between worker and soldier heads of G. sulphureus. This is the first study to characterize the complete head transcriptome of a higher termite G. sulphureus using a high-throughput sequencing. Our study may provide an overview and comprehensive molecular resource for comparative studies of the transcriptomics and genomics of termites.
  5. Fulltext Corrigendum to "Impact of the cognitive learning factors on sustainable organizational development" [Heliyon Volume 5, Issue 9, September 2019, e02398]
    Turi JA, Sorooshian S, Javed Y
    Heliyon, 2020 Jan;6(1):e03179.
    PMID: 32021921 DOI: 10.1016/j.heliyon.2020.e03179
    [This corrects the article DOI: 10.1016/j.heliyon.2019.e02398.].
  6. Fulltext Airport passengers' adoption behaviour towards self-check-in Kiosk Services: the roles of perceived ease of use, perceived usefulness and need for human interaction
    Taufik N, Hanafiah MH
    Heliyon, 2019 Dec;5(12):e02960.
    PMID: 31890945 DOI: 10.1016/j.heliyon.2019.e02960
    Purpose: The purpose of this paper is to examine the factors influencing passenger adoption and behaviour of self-service technology (SST) in airports. This study adopted the Theory Acceptance Model (TAM) and extended the model by including the need for human interaction (NI) construct in the study framework.

    Design/methodology/approach: The research framework is based on the theoretical concepts of SST usage from the inter-disciplinary field. Four hundred two questionnaires were collected from passengers who used the self-check-in kiosks in Kuala Lumpur International Airport (KLIA and KLIA2). The collected data were analysed using the structural equation modelling (SEM) technique.

    Findings: Different factors determine passengers' willingness and adoption of SSTs. Perceived ease of use and perceived usefulness significantly affect passenger adoption and behaviour of SSTs in airports. However, the passenger was much comfortable with the SST as the moderating effect of need for human interaction shows a negative result.

    Practical implications: The findings contribute to an understanding of how and why passengers use SSTs, which is critical from a customer relationship management (CRM) perspective. Better strategies can be developed to manage and coordinate SSTs delivery in the airport by understanding the passengers' experience from the self-check-in kiosks.

    Originality/value: This paper goes beyond the basic SSTs usage and intentions study by highlighting the nonimportance of human interaction in SSTs usage specifically by airport passengers.

  7. Fulltext Induction approach via P-Graph to rank clean technologies
    Low CX, Ng WY, Putra ZA, Aviso KB, Promentilla MAB, Tan RR
    Heliyon, 2020 Jan;6(1):e03083.
    PMID: 31909259 DOI: 10.1016/j.heliyon.2019.e03083
    Identification of appropriate clean technologies for industrial implementation requires systematic evaluation based on a set of criteria that normally reflect economic, technical, environmental and other aspects. Such multiple attribute decision-making (MADM) problems involve rating a finite set of alternatives with respect to multiple potentially conflicting criteria. Conventional MADM approaches often involve explicit trade-offs in between criteria based on the expert's or decision maker's priorities. In practice, many experts arrive at decisions based on their tacit knowledge. This paper presents a new induction approach, wherein the implicit preference rules that estimate the expert's thinking pathways can be induced. P-graph framework is applied to the induction approach as it adds the advantage of being able to determine both optimal and near-optimal solutions that best approximate the decision structure of an expert. The method elicits the knowledge of experts from their ranking of a small set of sample alternatives. Then, the information is processed to induce implicit rules which are subsequently used to rank new alternatives. Hence, the expert's preferences are approximated by the new rankings. The proposed induction approach is demonstrated in the case study on the ranking of Negative Emission Technologies (NETs) viability for industry implementation.
  8. Fulltext Teachers' burnout: A SEM analysis in an Asian context
    Prasojo LD, Habibi A, Mohd Yaakob MF, Pratama R, Yusof MR, Mukminin A, et al.
    Heliyon, 2020 Jan;6(1):e03144.
    PMID: 31938746 DOI: 10.1016/j.heliyon.2019.e03144
    Researchers in educational psychology have researched Teacher Self-Concept (TSC) and Teacher Efficacy (TE) as two main predictors predicting burnout. Guided by a model developed by Zhu, Liu, Fu, Yang, Zhang & Shi (2018), the researchers aimed at building a model involving TSC, TE, and three components of burnout; Emotional Exhaustion (EE), Depersonalization (DP), and Reduced Personal Accomplishment (RPA) through Structural Equation Modeling (SEM). The researchers investigated predicting factors of burnout by reporting TSC and TE that might directly affect the components and examine the probability of TE to become a mediator of the correlation between TSC and burnout. This research also examined whether the difference emerges constantly among demographic information (gender and teaching experience) regarding all involved variables. A sample of 876 teachers across three Indonesian provinces completed a printed form of questionnaires. Some statistical procedures namely Content Validity Index (CVI), Exploratory Factor Analysis (EFA), Confirmatory Factor Analysis (CFA), Covariance-Based Structural Equation Modeling (CB-SEM), and t-test were conducted. Findings informed that the model is valid and reliable. TSC could directly affect EE, DE, and RPA, as well as indirectly influence them mediated by TE. Besides, TE is also reported to have significant relationships with EE, DE, and RPA. No significant differences in terms of age and teaching experiences emerge, except for EE.
  9. Fulltext Hypertension in a mountainous province of Vietnam: prevalence and risk factors
    Nam KD, Van NB, Hoang LV, Duc TP, Thi Ha TT, Tuan VT, et al.
    Heliyon, 2020 Feb;6(2):e03383.
    PMID: 32072063 DOI: 10.1016/j.heliyon.2020.e03383
    Background: Hypertension (HTN) significantly contributes to global disease burden, and its prevalence varies amongst different countries and regions. This work is aimed to characterize the hypertensive prevalence and identify risk factors for HTN among the residents in five locations (four communes and one town) of Moc Chau district (Son La province, Vietnam).

    Methods: A cross-sectional study with a cross-sectional methodology was done in selected places from August 2018 to December 2018. We interviewed 197 participants aged equal to or more than 18 years old and measured their blood pressure (BP). Univariate and multivariate logistic regression were applied.

    Results: The overall HTN prevalence of 30.0% was recorded. The differences of HTN prevalence rates were seen by several characters including age groups (p <0.001), accompanying disease (p <0.001) and alcohol drinking (p <0.05). Factors independently associated with hypertension were age (ORs: 3.1 [1.1-9.1]; 6.1 [1.7-22.3]), much salty consumption (OR: 2.6 [1.1-6.6]), alcohol use (OR: 3.1 [1.2-8.1]), HTN familial history (OR: 4.2 [1.3-13.3]) and at least one suffering disease (OR: 5.2 [2.1-12.7]).

    Conclusions: Thus, this study highlighted the high overall HTN prevalence in the Vietnam Northwestern region. Significant differences of HTN rate were observed among several characteristics such as age groups, accompanying disease and alcohol drinking. Age group, much salty consumption, alcohol use, hypertension familial history and at least one suffering disease were risk factors for HTN in study group.

  10. Fulltext The influence of leadership quality towards community cohesion in Iban community in Malaysia
    Rezaul Islam M, Wahab HA, Anggum LA
    Heliyon, 2020 Feb;6(2):e03370.
    PMID: 32072057 DOI: 10.1016/j.heliyon.2020.e03370
    This study aimed to examine the influence of the traditional leadership qualities towards to develop community cohesion in the Iban community in Malaysia. A quantitative approach was used to conduct this study, where data were collected through a self-administered survey questionnaire from 210 chiefs in the Iban longhouse at the Pakan District in Sarawak, Malaysia. A pre-tested questionaire was administrered to the respondents using a simple random sampling in the District of Pakan, Sarawak. The leadership quality was measured based on the leadership traits, leadership style, leadership behaviour, situational leadership, and trsnformational leadership; while the community cohesion was measured by a sense of belonging, social alienation, social support, rootedness, social solidarity, and social ties. The results of the correlation and regression analysis showed that the traditional leadership qualities had a significant correlation with the development of social cohesion. The findings proved that the traditional leadership is essential to increase community cohesion in the Iban community. The findings would be important guideline to the development thinkers, practitioners, community leaders, and development institutions.
  11. Investigating the expansion characteristics of geopolymer cement samples in a water bath and compared with the expansion of ASTM Class-G cement
    Rahman SHBA, Irawan S, Shafiq N, Rajeswary R
    Heliyon, 2020 Feb;6(2):e03478.
    PMID: 32140594 DOI: 10.1016/j.heliyon.2020.e03478
    In selecting the binder composition for oil well application, its stability is an important design parameter. This paper presents the results of an experimental study conducted for comparing the linear expansion characteristics of geopolymer cement with the traditionally used ASTM Class G cement system. The expansion test was done in a water bath at 60 °C subjected to different curing intervals. The linear expansion of a cement system defines as the dimensional changes occur in the system, which is sometimes required to avoid the cement shrinkage during the hydration phase. In the case when the desired level of expansion is not achieved in the system, then the commercially available expandable materials are added in the class G cement system that enables the system to expand to the desired level. Shrinkage in the cementing system causes the formation of a microannulus or induces a gap that may allow the migration of fluid, hence the integrity of the system could be lost. This experimental study has revealed that the geopolymer cement tends to expand 0.15%-0.2% without the addition of any admixture, whereas the ASTM Class G cement has shown a lower value of linear expansion, which was obtained less than 0.1% after 18 days of curing. In the case of Class G cement, the addition of expandable material helped to increase the expansion; in the case of a geopolymer system, the additive has further accelerated the expansion.
  12. Fulltext A method of estimating age of undocumented children and young adults of different socioeconomic status in Cambodia
    Kar May L, Mei Shian AY, Durward C, Jayaraman J
    Heliyon, 2020 Feb;6(2):e03476.
    PMID: 32140592 DOI: 10.1016/j.heliyon.2020.e03476
    A growing number of Cambodian children without legal documentary evidence of date of birth are vulnerable to exploitation. This study aimed to evaluate the applicability of southern Chinese reference dataset for dental age estimation on Cambodian children and young adults of different socioeconomic status. Dental panoramic tomographs (DPT) of 371 Cambodian children and young adults belonging to lower and higher socioeconomic status (SES) groups were analyzed. All the left maxillary and mandibular permanent teeth including the third molars were scored based on Demirjian's classification of tooth development stages. Chronological age (CA) was calculated from the date of birth and date of exposure of radiograph. The mean age of attainment for each stage of development was obtained from the southern Chinese reference dataset. Dental age (DA) was calculated by averaging the mean age scores for all the teeth. Paired t-test and correlation analysis were conducted to measure associations between the chronological age and the dental age for males and females in the lower and higher socio-economic status groups. Underestimation of age was observed in both SES groups using the southern Chinese reference dataset. For the higher SES group, the difference between the chronological and dental age (CA-DA) was 0.26 years for females and 0.11 years for males. The difference was statistically significant only in females (p < 0.05). In the low SES group, the results showed a difference of 0.07 years in females and 0.01 years in males; the differences were not statistically significant in both sexes (p > 0.05). A strong correlation was observed between the CA and DA in both sex and SES groups ranging from 0.969 to 0.988 (p < 0.05). The southern Chinese dental reference dataset can be used to estimate the age of undocumented Cambodian male and female children and young adults of both higher and lower SES.
  13. Fulltext Insight into the origin of chikungunya virus in Malaysian non-human primates via sequence analysis
    Suhana O, Nazni WA, Apandi Y, Farah H, Lee HL, Sofian-Azirun M
    Heliyon, 2019 Dec;5(12):e02682.
    PMID: 31867449 DOI: 10.1016/j.heliyon.2019.e02682
    Chikungunya virus (CHIKV) is maintained in the sylvatic cycle in West Africa and is transmitted by Aedes mosquito species to monkeys. In 2006, four verified CHIKV isolates were obtained during a survey of arboviruses in monkeys (Macaca fascicularis) in Pahang state, Peninsular Malaysia. RNA was extracted from the CHIKV isolates and used in reverse transcription polymerase chain reactions (RT-PCR) to amplify PCR fragments for sequencing. Nucleic acid primers were designed to generate overlapping PCR fragments that covered the whole viral sequence. A total of 11,238 base pairs (bp) corresponding to open reading frames (ORFs) from our isolates and 47 other registered isolates in the National Center for Biotechnology Information (NCBI) were used to elucidate sequences, amino acids, and phylogenetic relationships and to estimate divergence times by using MEGA 7.0 and the Bayesian Markov chain Monte Carlo method. Phylogenetic analysis revealed that all CHIKV isolates could be classified into the Asian genotype and clustered with Bagan Panchor clades, which are associated with the chikungunya outbreak reported in 2006, with sequence and amino acid similarities of 99.9% and 99.7%, respectively. Minor amino acid differences were found between human and non-human primate isolates. Amino acid analysis showed a unique amino acid at position 221 in the nsP1region, at which a glycine (G) was found only in monkey isolates, whereas arginine (R) was found at the same position only in human isolates. The time to the most recent common ancestor (MRCA) estimation indicated that CHIKV probably started to diverge from human to non-human primates in approximately 2004 in Malaysia. The results suggested that CHIKV in non-human primates probably resulted from the spillover of the virus from humans. The study will be helpful in understanding the movement and evolution of CHIKV in Malaysia and globally.
  14. Fulltext Water transport properties of boron nitride nanosheets mixed matrix membranes for humic acid removal
    Tang CY, Zulhairun AK, Wong TW, Alireza S, Marzuki MSA, Ismail AF
    Heliyon, 2019 Jan;5(1):e01142.
    PMID: 30723824 DOI: 10.1016/j.heliyon.2019.e01142
    Ultrafiltration grade polysulfone-based mixed matrix membranes (MMMs) incorporated with two-dimensional boron nitride nanosheet (BNNS) was prepared via phase inversion method. The amount of BN incorporated was varied and the influence on membrane morphology, contact angle, surface charge, as well as water permeability and humic acid rejection were investigated. Results revealed that the addition of BN to the membrane matrix resulted in profound increase in water permeability (almost tripled to that of neat PSf) and humic acid rejection due to the increase in pore size and surface negative charge. Beyond the morphological changes imparted by the inclusion of BNNS, we postulated that the presence of BNNS within the membrane matrix also contribute to the enhancement in flux and rejection based on surface-slip and selective interlayer transport. Despite the favourable augmentation of water transport and filtration performance, the MMMs suffered with fouling problem due to the entrapment of foulant within the enlarged pores and the membrane valleys. Its inherent adsorptive character could be a disadvantage when utilized as membrane filler.
  15. Fulltext An investigation on longitudinal residual strains distribution of thin-walled press-braked cold formed steel sections using 3D FEM technique
    Mutafi A, Yidris N, Ishak MR, Zahari R
    Heliyon, 2018 Nov;4(11):e00937.
    PMID: 30839801 DOI: 10.1016/j.heliyon.2018.e00937
    Steel sections are normally shaped via cold work manufacturing processes. The extent of cold work to shape the steel sections might induce residual stresses in the region of bending. Previously, researchers had performed studies on the influences of local buckling on the failure behavior of steel compression members which shown that failure will happen when most of the yielding has extended to the middle surface in the bend region of the sections. Therefore, these cold work methods may have major effect on the behavior of the steel section and also its load-bearing capability. In addition, another factor may play significant role in formed section's load-bearing capacity which is the longitudinal residual strain. The longitudinal residual strain raised during forming procedure can be used to define the section imperfection of the formed section and its relation to the existence of defects. Therefore, the main motivation of this research paper is to perform three-dimensional finite element (3D-FE) to investigate peak longitudinal residual strains of a thin-walled steel plate with large bending angle along member length. A 3D finite element simulation in ABAQUS has been employed to simulate this forming process. The study concluded that the longitudinal residual strain at the section corner edge was higher than those at the rest of the corner region. These strains at the edge were higher than the yield strain


    (



    ε


    y



    )


    of the formed section which occurred due to the lack of transverse restraint. This made the plate edge tended to bend toward the normal direction when it was under a high transverse bending. This causes a significant difference in longitudinal strain at the plate edge.
  16. Fulltext A comparative study on foliage and peels of Hylocereus undatus (white dragon fruit) regarding their antioxidant activity and phenolic content
    Som AM, Ahmat N, Abdul Hamid HA, Azizuddin N
    Heliyon, 2019 Feb;5(2):e01244.
    PMID: 30828665 DOI: 10.1016/j.heliyon.2019.e01244
    Hylocereus undatus foliage is believed to contain antioxidants similar to its peel. Numerous studies have been conducted to determine the total phenolic content (TPC) and antioxidant activity on the Hylocereus undatus pulps and peels; however, similar studies on its foliage have yet to be investigated. In this study, Hylocereus undatus foliage and peels were extracted using two different solvents namely; chloroform and methanol through Folin-Ciocalteu method and Diphenyl-1-Ipicrylhydrazyl (DPPH) free radical scavenging assay for TPC and antioxidant activity, respectively. As for TPC, results revealed that the peels gave higher TPC in both methanol (48.15 mg GAE/100g extract) and chloroform (18.89 mg GAE/100g extract) extractions than foliage (30.3 mg GAE/100g extract and 5.92 mg GAE/100g extract, respectively). However, when a comparison was made between foliage and peels in terms of its scavenging effects in DPPH assay, the peels contained more antioxidants (18.71%) than foliage (38.3%) in the chloroform solvent extracts. This study shows that Hylocereus undatus foliage has a similar antioxidant activity as its peels and is potentially a natural antioxidant in food applications.
  17. Fulltext Behavior of schmutzdecke with varied filtration rates of slow sand filter to remove total coliforms
    Matuzahroh N, Fitriani N, Ardiyanti PE, Kuncoro EP, Budiyanto WD, Isnadina DRM, et al.
    Heliyon, 2020 Apr;6(4):e03736.
    PMID: 32280804 DOI: 10.1016/j.heliyon.2020.e03736
    The previous research showed that slow sand filtration (SSF) can remove the total coli by approximately 99% because of the schmutzecke layer in the filter. The presented study aimed to complete the previous research on SSF, especially on the schmuztdecke layer mechanism, to remove total coli. Total coli is a parameter of water quality standard in Indonesia, and the behavior of schmutzdecke affects the total coli removal. In the present study, the raw water from Amprong River was treated using horizontal roughing filter (HRF) and SSF. The variations in SSF rate used were 0.2 and 0.4 m/h. Total coliforms were analyzed using the most probable number test, and schmutzdecke visualization was conducted through scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX). The best coliform concentration in water treated by the combination of HRF and SSF was 4,386 colonies per 100 mL of sample using the filtration rate of 0.2 m/h, and its removal efficiency was 99.60%. However, the quality of water treated by the combination of HRF and SSF did not meet the drinking water quality standard because the removal of total coli must be 100%. The SEM-EDX visualization results in schmutzdecke showed that the average bacteria in the schmutzdecke layer were small, white, opaque, and circular, with entire edge and flat elevation. The Gram test results showed that the schmutzdecke bacteria consisted of Gram-positive and Gram-negative bacteria with basil as the common cell form.
  18. Fulltext The role of silica-containing agro-industrial waste as reinforcement on physicochemical and thermal properties of polymer composites
    Rizal S, Fizree HM, Hossain MS, Ikramullah, Gopakumar DA, Wan Ni EC, et al.
    Heliyon, 2020 Mar;6(3):e03550.
    PMID: 32190763 DOI: 10.1016/j.heliyon.2020.e03550
    This study was conducted to determine the influence of the oil palm boiler ash (OPBA) reinforcement on the microstructural, physical, mechanical and thermal properties of epoxy polymer composites. The chemical composition analysis of OPBA revealed that it contains about 55 wt.% of SiO2 along with other metallic oxides and elements. The surface morphology of OPBA showed angular and irregular shapes with porous structures. The influence of OPBA as a reinforcement in epoxy composite was studied with varying filler loadings (10-50 wt.%) and different particle sizes (50-150 μm). The result showed that the incorporation of OPBA in composites has improved the physical, mechanical and thermal properties of the epoxy matrix. The highest physical and mechanical properties of fabricated composites were attained with 30 wt.% loading and size of 50 μm. Also, thermal stability and the percentage of char residue of the composite increased with increasing filler loading. Furthermore, the contact angle of OPBA reinforced epoxy composites increased with the increase of filler loading. The lowest value of the contact angle was obtained at 30 wt.% of filler loading with the OPBA particle size of 50 μm. The finding of this study reveals that the OPBA has the potential to be used as reinforcement or filler as well as an alternative of silica-based inorganic fillers used in the enhancement of mechanical, physical and thermal properties of the epoxy polymer composite.
  19. Fulltext Kinetic evaluation of a partially packed upflow anaerobic fixed film reactor treating low-strength synthetic rubber wastewater
    Nor Faekah I, Fatihah S, Mohamed ZS
    Heliyon, 2020 Mar;6(3):e03594.
    PMID: 32258460 DOI: 10.1016/j.heliyon.2020.e03594
    A bench-scale model of a partially packed upflow anaerobic fixed film (UAF) reactor was set up and operated at five different hydraulic retention times (HRTs) of (17, 14, 10, 8, and 5) days. The reactor was fed with synthetic rubber wastewater consisting of a chemical oxygen demand (COD) concentration of 6355-6735 mg/L. The results were analyzed using the Monod model, the Modified Stover-Kincannon models, and the Grau Second-Order Model. The Grau Second-Order model was found to best fit the experimental data. The biokinetic constant values, namely the growth yield coefficient (Y) and the endogenous coefficient (Kd) were 0.027 g VSS/g COD and 0.1705 d-1, respectively. The half-saturation constant (Ks) and maximum substrate utilization rate (K) returned values of 84.1 mg/L and 0.371 d-1, respectively, whereas the maximum specific growth rate of the microorganism (μmax) was 0.011 d-1. The constants, Umax and KB, of the Stover-Kincannon model produced values of 6.57 g/L/d and 6.31 g/L/d, respectively. Meanwhile, the average second-order substrate removal rate, ks(2), was 105 d-1. These models gave high correlation coefficients with the value of R2 = 80-99% and these indicated that these models can be used in designing UAF reactor consequently predicting the behaviour of the reactor.
  20. Fulltext An evaluation of subcritical hydrothermal treatment of end-of-pipe palm oil mill effluent
    Lee ZS, Chin SY, Cheng CK
    Heliyon, 2019 Jun;5(6):e01792.
    PMID: 31245637 DOI: 10.1016/j.heliyon.2019.e01792
    This study evaluates the effects of subcritical hydrothermal treatment on palm oil mill effluent (POME) and its concomitant formations of solid hydrochar, liquid product and gaseous product. The reactions were carried out at temperatures ranged 493 K-533 K for 2 h. The highest reduction of chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were 58.8% and 62.5%, respectively, at 533 K. In addition, the removal of total suspended solids (TSS) achieved up to 99%, with the pH of POME reaching 6 from the initial pH 4. The gas chromatography coupled with mass spectroscopy (GC-MS) analysis showed that the fresh POME contained n-Hexadecanoic acid as the dominant component, which gradually reduced in the liquid product in the reaction with increased temperature, in addition to the attenuation of carboxyl compounds and elevation of phenolic components. The gaseous products contained CO2, CO, H2, and C3 - C6 hydrocarbons. Traces of CH4 were only found at 533 K. CO2 is the dominant species, where the highest of 3.99 vol% per 500 mL working volume of POME recorded at 533 K. The solid hydrochars showed negligible morphological changes across the reaction temperature. The O/C atomic ratio of the hydrochar range from 0.157 to 0.379, while the H/C atomic ratio was in the range from 0.930 to 1.506. With the increase of treatment temperature, the higher heating value (HHV) of the hydrochar improved from 24.624 to 27.513 MJ kg-1. The characteristics of hydrochar make it a fuel source with immense potential. POME decomposed into water-soluble compounds, followed by deoxygenation (dehydration and decarboxylation) in producing hydrochar with lower oxygen content and higher aromatic compounds in the liquid product. Little gaseous hydrocarbons were produced due to subcritical hydrothermal gasification at low temperature.
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