Journal Articles

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  • Publication
    Adsorption and toxicity of heavy metals on activated sludge
    ( 2010)
    Ong Soon An
    ;
    Eiichi Toorisaka
    ;
    Makoto Hirata
    ;
    Tadashi Hano
    The adsorption of Cu, Cd, Ni, Zn, and Cr from synthetic solutions on powdered activated carbon (PAC), activated sludge, and dried sludge were investigated under laboratory conditions to assess its ability to remove heavy metals. The adsorption efficiency increased rapidly within the first 30 min and then slowed down as it approached a steady state after 5 h of contact time. The results showed that activated sludge and PAC had a higher adsorption capacity than dried sludge. However, PAC showed a better adsorption capacity for Cu, Zn, and Ni than activated sludge. The maximum adsorption capacity, as quantified by the Langmuir parameter Q for activated sludge was 44, 30, 24, 23, and 18 mg/g for Cu, Ni, Cd, Cr, and Zn, respectively. In the case of dried sludge, the respective values of Q were 20, 13, 11, 3, and 10 mg/g. The acute toxicity of these five heavy metals to the activated sludge microorganisms was determined on the basis of the reduction in the specific oxygen uptake rate (SOUR). The results obtained from the SOUR measurements indicated a decreasing toxicity scale, Cu > Cd > Ni ' Cr > Zn on activated sludge microorganisms.
      1  12
  • Publication
    Fly ash-based geopolymer lightweight concrete using foaming agent
    ( 2012)
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Kamarudin Hussin
    ;
    Mohamed Bnhussain
    ;
    Khairul Nizar Ismail
    ;
    Zarina Yahya
    ;
    Rafiza Abdul Razak
    In this paper, we report the results of our investigation on the possibility of producing foam concrete by using a geopolymer system. Class C fly ash was mixed with an alkaline activator solution (a mixture of sodium silicate and NaOH), and foam was added to the geopolymeric mixture to produce lightweight concrete. The NaOH solution was prepared by dilute NaOH pellets with distilled water. The reactives were mixed to produce a homogeneous mixture, which was placed into a 50 mm mold and cured at two different curing temperatures (60 °C and room temperature), for 24 hours. After the curing process, the strengths of the samples were tested on days 1, 7, and 28. The water absorption, porosity, chemical composition, microstructure, XRD and FTIR analyses were studied. The results showed that the sample which was cured at 60 °C (LW2) produced the maximum compressive strength for all tests, (11.03 MPa, 17.59 MPa, and 18.19 MPa) for days 1, 7, and 28, respectively. Also, the water absorption and porosity of LW2 were reduced by 6.78% and 1.22% after 28 days, respectively. The SEM showed that the LW2 sample had a denser matrix than LW1. This was because LW2 was heat cured, which caused the geopolymerization rate to increase, producing a denser matrix. However for LW1, microcracks were present on the surface, which reduced the compressive strength and increased water absorption and porosity.
      3  32
  • Publication
    The role of sodium surface species on electrochemical promotion of catalysis in a Pt/YSZ system: The case of ethylene oxidation
    ( 2013-04-23)
    Naimah Ibrahim
    ;
    Danai Poulidi
    ;
    Ian S. Metcalfe
    The role of sodium addition as foreign (impurity) species on the electrochemical promotion of ethylene oxidation in a Pt/YSZ system was investigated. It was found that the presence of sodium surface species on the catalyst surface can significantly affect its catalytic and electrocatalytic properties, but there is no clear evidence at this stage that such species are necessary for the observation of EPOC. Under negative polarisation, low coverage sodium was found to have a pronounced effect on the electrochemical promotion of ethylene oxidation as an electronic promoter. The reaction changed behaviour from electrophilic at low sodium coverage (0.11%) and low to intermediate oxygen partial pressure (pO2 ⩽ 3.0 kPa) to electrophobic at high sodium coverage (65%) and under high oxygen partial pressures (pO2 = 8.0 kPa). In between the two sets of conditions, the reaction showed volcano-type behaviour depending on the coverage of sodium and gas-phase oxygen partial pressure.
      21  2
  • Publication
    Analysis of short time period of operation of horizontal ground heat exchangers
    ( 2015)
    Salsuwanda Selamat
    ;
    Akio Miyara
    ;
    Keishi Kariya
    Ground source heat pump (GSHP) systems have been proven to have higher efficiency compared to conventional air source heat pump systems for space heating and cooling applications. While vertical ground heat exchangers (GHE) are favorable in GSHP installation, this type of configuration requires higher capital costs as opposed to horizontal configuration. Numerical simulation has been used to accurately predict the thermal performance of GHE. In this paper, numerical analysis of thermal performance for slinky horizontal GHE loops in different orientations and operation modes is discussed. It was found that the loop orientation is not so important due to the little effect it has on thermal performance. While the mean heat exchange rate of copper loop increases 48% compared to HDPE loop, the analysis supports the common claim that heat exchange rate is predominantly limited by the thermal conductivity of the ground. With the same amount of circulation work, the mean heat exchange rate increases by 83%–162% when operated in parallel loops operations. The performance in these operations can be further optimized to 10%–14% increase when spacing between adjacent loops was provided. The spacing helps to minimize interference of heat flow that would penalize the overall thermal performance.
      2  17
  • Publication
    Optimization of NaOH molarity, LUSI mud/alkaline activator, and Na₂SiO₃/NaOH ratio to produce lightweight aggregate-based geopolymer
    ( 2015)
    Rafiza Abd Razak
    ;
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Djwantoro Hardjito
    ;
    Kamarudin Hussin
    ;
    Khairul Azwan Ismail
    ;
    Zarina Yahya
    This paper presents the mechanical function and characterization of an artificial lightweight geopolymer aggregate (ALGA) using LUSI (Sidoarjo mud) and alkaline activator as source materials. LUSI stands for LU-Lumpur and SI-Sidoarjo, meaning mud from Sidoarjo which erupted near the Banjarpanji-1 exploration well in Sidoarjo, East Java, Indonesia on 27 May 2006. The effect of NaOH molarity, LUSI mud/Alkaline activator (LM/AA) ratio, and Na₂SiO₃/NaOH ratio to the ALGA are investigated at a sintering temperature of 950 °C. The results show that the optimum NaOH molarity found in this study is 12 M due to the highest strength (lowest AIV value) of 15.79% with lower water absorption and specific gravity. The optimum LUSI mud/Alkaline activator (LM/AA) ratio of 1.7 and the Na2SiO3/NaOH ratio of 0.4 gives the highest strength with AIV value of 15.42% with specific gravity of 1.10 g/cm3 and water absorption of 4.7%. The major synthesized crystalline phases were identified as sodalite, quartz and albite. Scanning Electron Microscope (SEM) image showed more complete geopolymer matrix which contributes to highest strength of ALGA produced.
      1  17
  • Publication
    A proposed aerobic granules size development scheme for aerobic granulation process
    ( 2015-04)
    Farrah Aini Dahalan
    ;
    Norhayati Abdullah
    ;
    Ali Yuzir
    ;
    Gustaf Olsson
    ;
    Myzairah Salmiati
    ;
    Mohd Fadhil Mohd Hamdzah
    ;
    Siti Aqlima Din
    ;
    Khalilah Abdul Ahmad
    ;
    Aznah Nor Khalil
    ;
    Zainura Zainon Anuar
    ;
    Zaini Noor
    Aerobic granulation is increasingly used in wastewater treatment due to its unique physical properties and microbial functionalities. Granule size defines the physical properties of granules based on biomass accumulation. This study aims to determine the profile of size development under two physicochemical conditions. Two identical bioreactors namely Rnp and Rp were operated under non-phototrophic and phototrophic conditions, respectively. An illustrative scheme was developed to comprehend the mechanism of size development that delineates the granular size throughout the granulation. Observations on granules’ size variation have shown that activated sludge revolutionised into the form of aerobic granules through the increase of biomass concentration in bioreactors which also determined the changes of granule size. Both reactors demonstrated that size transformed in a similar trend when tested with and without illumination. Thus, different types of aerobic granules may increase in size in the same way as recommended in the aerobic granule size development scheme.
  • Publication
    Characterisation and evaluation of trimesic acid derivatives as disulphide cross-linked polymers for potential colon targeted drug delivery
    ( 2017)
    Siti Nur Aishah Mat Yusuf
    ;
    Ng, Yoke Mooi
    ;
    Ayub, Asila Dinie
    ;
    Ngalim, Siti Hawa
    ;
    Vuanghao Lim
    Discovery and use of biocompatible polymers offers great promise in the pharmaceutical field, particularly in drug delivery systems. Disulphide bonds, which commonly occur in peptides and proteins and have been used as drug-glutathione conjugates, are reductively cleaved in the colon. The intrinsic stability of a disulphide relative to thiol groups is determined by the redox potential of the environment. The objective of this study was to synthesise a trimesic acid-based disulphide cross-linked polymer that could potentially be used for targeted delivery to the colon. The monomer was synthesised by an amide coupling reaction between trimesic acid and (triphenylmethyl) thioethylamine using a two-step synthesis method. The s-trityl group was removed using a cocktail of trifluoroacetic acid and triethylsilane to expose the thiols in preparation for further polymerisation. The resulting polymers (P10, P15, P21, P25, and P51, generated using different molar ratios) were reduced after 1.5 h of reduction time. Scanning electron microscopy images of the polymers showed spherical, loose, or tight patterns depending on the molar ratio of polymerisation. These polymers also exhibited efficient dissolution under various gastrointestinal conditions. Of the five polymers tested, P10 and P15 appeared to be promising drug delivery vehicles for poorly soluble drugs, due to the hydrophobic nature of the polymers.
      1  22
  • Publication
    Effects of magnesium ions in microbial cells adhesion of attached growth system for the enhancement of biogas production
    (Penerbit UTM Press, 2020)
    Nabilah Aminah Lutpi
    ;
    Wong Yee Shian
    ;
    Tengku Nuraiti Tengku Izhar
    ;
    Yiek Wee Kiong
    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
    Prediction of pressuremeter modulus (EM) using GMDH neural network: a case study of Kenny Hill Formation
    (Springer, 2020)
    Mohd Faiz Mohammad Zaki
    ;
    Mohd Ashraf Mohamad Ismail
    ;
    Darvintharen Govindasamy
    ;
    Frankie Cheah Peng Leong
    Soil investigation (SI) work is a process of collecting subsurface ground profile information in evaluating soil engineering properties for a construction project. The standard penetration method (SPT) is widely accepted worldwide as a feasible and relatively inexpensive method over other field tests. Pressuremeter test (PMT), on the other hand, is costly and more popular in situ method in interpreting soil deformation behavior. Considering SPT is available in almost site investigation works for all sizes of project, it was tempting to establish the correlation between SPT and PMT results, specifically in local geologic setting. The study was conducted in Kenny Hill Formation, Kuala Lumpur, Malaysia. The correlation established in this study is between pressuremeter modulus (EM) and SPT blow count (N60). In addition to in situ methods, the physical properties of soil extruded from boreholes were tested in geotechnical laboratories to determine soil properties, such as particle size distribution, liquid limit, and plastic limit. These parameters need to be considered during prediction of EM. Group method of data handling (GMDH) neural network has been used to achieve this objective. The mean absolute error (MAE) results show that the GMDH neural networks produce values of 8.04 and 8.59 for training and testing. The root mean square error (RMSE) yields 10.61 and 10.84 for training and testing, respectively. Further, the results of the coefficients of determination (R2) are 0.794 and 0.726 for training and testing demonstrates a good correlation exists between predicted and measured values. Based on the GMDH results, N60, sand, and clay are required input variables for determination of EM.
  • Publication
    Hybrid polymerisation: an exploratory study of the chemo-mechanical and rheological properties of hybrid-modified bitumen
    (MDPI, 2020)
    Ilya Joohari
    ;
    Filippo Giustozzi
    In this study, the mechanical and rheological properties of hybrid polymer-modified bitumen (PMB) have been investigated. For this purpose, nine different polymers—including crumb rubber, elastomers and plastomers at varying content—were studied to evaluate their mechanical performance as single polymers, first, and as a combination of two or more polymers as a hybrid polymer blend. Subsequently, the hybrid polymer blends were added in a relatively small percentage into the base bitumen to study its influence on the rheological performance of hybrid PMB. The mechanical properties identified from the analysis of the stress-strain curve of the single polymers were the Young’s Modulus, tensile stress, and elongation at break. The chemical structure of the polymer hybrid blends was analysed using FTIR, followed by frequency sweep tests conducted using the dynamic shear rheometer (DSR) to determine the bitumen rheological properties. Results showed that hybrid PMB enhances the viscoelastic behaviour of bitumen at both low and high temperature compared to other PMBs only including single polymers.
  • Publication
    Planning the maintenance of green building materials for sustainable development: a building information modelling approach
    (Emerald Publishing, 2020)
    Zul-Atfi Ismail
    Purpose: Most green building (GB) materials, which are used widely in the construction sector in Malaysia, perform poorly in terms of energy efficiency and sustainability. Nevertheless, during maintenance planning of these materials, the focus is often directed towards comfort and design instead. However, as GB material construction projects grow in scale and complexity, interconnections between the activities and processes can be noticed during problematic planning performance management to monitor the GB material components for corrective and preventive maintenance actions. Design/methodology/approach: The concept of GB material maintenance planning for sustainable development and the main features of information and communication technology tools and techniques are based on analysis of literature reviews of GB material scenarios. Findings: The results show how decision-making support in maintenance planning can be unsuccessful and how planning decisions can frame the content of an integrated system to analyse information and reduce risks of GB material failure. Originality/value: The paper concludes that implementing a research framework for developing such a system can help improve the sustainable performance of maintenance planning of GB material economic, social and environmental issues.
  • Publication
    Green lean practices towards increasing operation value of manufacturing company
    (Penerbit UTHM, 2020)
    Ahmad Nur Aizat Ahmad
    ;
    Md Fauzi Ahmad
    ;
    Norhadilah Abdul Hamid
    ;
    Yunos Ngadiman
    ;
    Mohamed Ismail Pakir
    ;
    Gusman Nawanir
    ;
    Adnan Bakri
    ;
    Mustaqqim Abdul Rahim
    Nowadays, manufacturing industries are rapidly developing. However the constraints faced by today's producers are how to produce their products quickly through low costs while at the same time, the reduction of waste disposal in the environment. The high waste of time in the manufacturing industry is often attributed to the wastage that occurred in the company’s operations. Lean manufacturing is linked for improving the standard working. It is one of the production strategies that drive the industry towards a more efficient production of goods and services. Meanwhile, green manufacturing has been adopted as a requirement to achieve a minimal negative impact on the environment. The green lean is a concept to make sure system more efficient, reduce unwanted product releases and minimize the environmental impact. So, the main objective of this research is to reduce cycle time in manufacturing company by adopting green lean elements. This research focuses on furniture manufacturing and conducted a structural interview question, observation and time study method. To refine those time operation problems, the company had implemented the new green lean practices into the operation department. The results after implement these methods totally show an improved progress. The paper would help the manufacturer to organize and improve their company performance. In conclusion, this research is about to identify and reduce the time waste to improve the operation value of the manufacturing company while at the same time it would reduce the environmental impact in future.
  • Publication
    Influence of Recycled Concrete Aggregate (RCA) towards the performance of Hot-Mix Asphalt (HMA) mixture
    (The World Academy of Research in Science and Engineering, 2020)
    Significant use of Recycled Concrete Aggregate (RCA) has been applied by many countries especially in Hot-Mix Asphalt (HMA) as can possibly improve road construction in the economic and environmental aspects. However, in spite of such promising potentials, insufficient and inconclusive data to be referred based on previous study causes further study to be conducted as to focus more on the performance of aggregate in term of the impact and crushing value by using RCA. Also, to investigate the influence of different percentage 0%, 10%, 20%, 30% and 40% of RCA in the HMA mixture to the Marshall stability, flow value and water absorption. When the percentage of RCA content increase, the performance of all the parameters has become weaker and lowered. But then, RCA still can be used in the HMA as the differences in the performances with the natural aggregate is slightly small. Therefore, the optimum percentage of RCA got on this study is 30% by referred and discussed on all the five parameters. In conclusion, RCA is a great material that can be used to replace natural aggregate as it contributes great benefit in the environment aspect and also helps in the reduction of stockpiles of concrete wastes.
  • Publication
    Hybrid intelligent vehicle system for managing construction supply chain in precast concrete building construction projects
    (Emerald, 2020)
    Zul-Atfi Ismail
    Purpose: While the adversarial nature of precast concrete (PC) building construction is frequently cited in the PC building construction press, only a few researchers have investigated construction supply chain management within the construction industry. Due to the interdisciplinary transportation environment, which inevitably results in disruption, the uses of construction supply chain and recovery from construction supply chain risk must be a subject of real interest, yet transportation management research in this area is scarce. Design/methodology/approach: The purpose of this study is to discuss the weakness in system approaches and their application for managing precast concrete building in the context of construction supply chain practice and how to overcome it. As a precursor to this paper, the paper reviews current construction supply chain management occurrence on PC building construction and explores the hybrid intelligent vehicle tools and techniques currently being used on such management. This paper also presents the new hybrid intelligent vehicle-based approach to manage construction supply chain risk and reduce associated tension on PC building construction schemes. Findings: The findings reveal the need for more sophisticated construction supply chain management solutions which accord with the needs of PC building construction schemes. Originality/value: The paper concludes by presenting a research framework for developing such a system in the future.
  • Publication
    Green roof performance under malaysia tropical climates: a review
    (Institute of Advanced Engineering and Science (IAES), 2020)
    Nur Fitriah Isa
    ;
    Hartini Kasmin
    ;
    Norhaizura Yahya
    ;
    Mustaqqim Abdul Rahim
    ;
    Zuhayr Md Ghazaly
    Green roof system is one of sustainable approach for energy consumption reduction and improving the aesthetic value of the built environment. The system has been adopted by most of developed countries; and in Malaysia, research on green roof studies are quite evolving however the implementation of the system is slow due to some perceptions and obstacles. Green roof has potential on providing benefits such as reduction on the urban heat island effect, reduces temperatures, pollution and improves the attenuation of stormwater. This paper will highlights on a preliminary review of the implementation green roof system in Malaysia and explores the performances of Malaysian green roof in order to highlight the performance of green roof under tropical climatic conditions using local configurations.
      7  2
  • Publication
    Lesson learned in maintaining the precast concrete buildings
    (Emerald Publishing Ltd., 2020)
    Zul-Atfi Ismail
    Purpose: The purpose of this study is to identify existing weaknesses in precast concrete building maintenance and how to overcome it. The contemporary practice of conventional methods in the pre-cast concrete (PC) building maintenance entails many issues such as PC component aesthetic and structural defects, no integration between maintenance systems and lack the intelligent capabilities of linking defect diagnosis operations in maintenance due to poor service delivery and defect repetition. A key problem impeding the widespread adoption of emerging technologies is the lack of competent contractor supporting the effectiveness of implemented information and communication technology than conventional methods and the returns on investment. Design/methodology/approach: The shortcomings of conventional methods are assessed from the perspective of PC buildings. Several data were collected through a case study of eight PC buildings from high-rise and complex buildings. Findings: The conventional methods had significantly little emphasis on defect diagnosis tools. It had also increased the inadequate strategic decision making to analyse information in improving the maintenance project outcomes for PC building. Originality/value: Building information modelling tools is suggested from findings and lessons learned as a good practice to reduce the repetition of defects on the design specification used and construction practiced.
      1  10
  • Publication
    Prediction of pressuremeter modulus (E M) using GMDH neural network: a case study of Kenny Hill Formation
    ( 2020-05-01)
    Mohd Faiz Mohammad Zaki
    ;
    Ismail M.A.M.
    ;
    Govindasamy D.
    ;
    Leong F.C.P.
    Soil investigation (SI) work is a process of collecting subsurface ground profile information in evaluating soil engineering properties for a construction project. The standard penetration method (SPT) is widely accepted worldwide as a feasible and relatively inexpensive method over other field tests. Pressuremeter test (PMT), on the other hand, is costly and more popular in situ method in interpreting soil deformation behavior. Considering SPT is available in almost site investigation works for all sizes of project, it was tempting to establish the correlation between SPT and PMT results, specifically in local geologic setting. The study was conducted in Kenny Hill Formation, Kuala Lumpur, Malaysia. The correlation established in this study is between pressuremeter modulus (EM) and SPT blow count (N60). In addition to in situ methods, the physical properties of soil extruded from boreholes were tested in geotechnical laboratories to determine soil properties, such as particle size distribution, liquid limit, and plastic limit. These parameters need to be considered during prediction of EM. Group method of data handling (GMDH) neural network has been used to achieve this objective. The mean absolute error (MAE) results show that the GMDH neural networks produce values of 8.04 and 8.59 for training and testing. The root mean square error (RMSE) yields 10.61 and 10.84 for training and testing, respectively. Further, the results of the coefficients of determination (R2) are 0.794 and 0.726 for training and testing demonstrates a good correlation exists between predicted and measured values. Based on the GMDH results, N60, sand, and clay are required input variables for determination of EM.
      4  21
  • Publication
    A State-of-the-Art review on innovative geopolymer composites designed for water and wastewater treatment
    ( 2021)
    Ismail Luhar
    ;
    Salmabanu Luhar
    ;
    Mohd. Mustafa Al Bakri Abdullah
    ;
    Rafiza Abd Razak
    ;
    Petrica Vizureanu
    ;
    Andrei Victor Sandu
    ;
    Petre-Daniel Matasaru
    There is nothing more fundamental than clean potable water for living beings next to air. On the other hand, wastewater management is cropping up as a challenging task day-by-day due to lots of new additions of novel pollutants as well as the development of infrastructures and regulations that could not maintain its pace with the burgeoning escalation of populace and urbanizations. Therefore, momentous approaches must be sought-after to reclaim fresh water from wastewaters in order to address this great societal challenge. One of the routes is to clean wastewater through treatment processes using diverse adsorbents. However, most of them are unsustainable and quite costly e.g. activated carbon adsorbents, etc. Quite recently, innovative, sustainable, durable, affordable, user and eco-benevolent Geopolymer composites have been brought into play to serve the purpose as a pretty novel subject matter since they can be manufactured by a simple process of Geopolymerization at low temperature, lower energy with mitigated carbon footprints and marvellously, exhibit outstanding properties of physical and chemical stability, ion-exchange, dielectric characteristics, etc., with a porous structure and of course lucrative too because of the incorporation of wastes with them, which is in harmony with the goal to transit from linear to circular economy, i.e., “one’s waste is the treasure for another”. For these reasons, nowadays, this ground-breaking inorganic class of amorphous alumina-silicate materials are drawing the attention of the world researchers for designing them as adsorbents for water and wastewater treatment where the chemical nature and structure of the materials have a great impact on their adsorption competence. The aim of the current most recent state-of-the-art and scientometric review is to comprehend and assess thoroughly the advancements in geo-synthesis, properties and applications of geopolymer composites designed for the elimination of hazardous contaminants viz., heavy metal ions, dyes, etc. The adsorption mechanisms and effects of various environmental conditions on adsorption efficiency are also taken into account for review of the importance of Geopolymers as most recent adsorbents to get rid of the death-defying and toxic pollutants from wastewater with a view to obtaining reclaimed potable and sparkling water for reuse offering to trim down the massive crisis of scarcity of water promoting sustainable water and wastewater treatment for greener environments. The appraisal is made on the performance estimation of Geopolymers for water and wastewater treatment along with the three-dimensional printed components are characterized for mechanical, physical and chemical attributes, permeability and Ammonium (NH4+) ion removal competence of Geopolymer composites as alternative adsorbents for sequestration of an assortment of contaminants during wastewater treatment.