Displaying publications 21 - 40 of 73 in total

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  1. Response surface methodology analysis of the photocatalytic removal of Methylene Blue using bismuth vanadate prepared via polyol route
    Abdullah AH, Moey HJ, Yusof NA
    J Environ Sci (China), 2012;24(9):1694-701.
    PMID: 23520879
    Visible-light driven photocatalyst bismuth vanadate (BiVO4) photocatalyst was synthesized by the polyol route using ethylene glycol. The precipitate was washed, dried and calcined at 450 degrees C for 3 hr. The sample was characterized by X-ray diffractometry (XRD), field emission scanning electron microscopy (FE-SEM), zeta potential, surface area (BET method) and band gap energy via diffuse reflectance spectroscopy (DRS). The synthesized BiVO4 has a monoclinic phase with a surface area of 4.3 m2/g and a band gap energy of 2.46 eV. A majority of the particles were in the range of 90-130 nm as obtained from the particle size distribution histrogram. The efficiency of the sample as a visible-light driven photocatalyst was examined by photodegrading Methylene Blue (MB). The effects of some operational photodegradation parameters such as mass loading, initial dye concentration and pH were also examined. Experimental design methodology was applied by response surface modeling and optimization of the removal of MB. The multivariate experimental design was employed to develop a quadratic model as a functional relationship between the percentage removal of MB and three experimental factors (BiVO4 loading, MB initial concentration and pH). The percentage removal of MB approached 67.21% under optimized conditions. In addition, a satisfactory goodness-of-fit was achieved between the,predictive and the experimental results.
  2. Fulltext Delaunay triangulation as a new coverage measurement method in wireless sensor network
    Chizari H, Hosseini M, Poston T, Razak SA, Abdullah AH
    Sensors (Basel), 2011;11(3):3163-76.
    PMID: 22163792 DOI: 10.3390/s110303163
    Sensing and communication coverage are among the most important trade-offs in Wireless Sensor Network (WSN) design. A minimum bound of sensing coverage is vital in scheduling, target tracking and redeployment phases, as well as providing communication coverage. Some methods measure the coverage as a percentage value, but detailed information has been missing. Two scenarios with equal coverage percentage may not have the same Quality of Coverage (QoC). In this paper, we propose a new coverage measurement method using Delaunay Triangulation (DT). This can provide the value for all coverage measurement tools. Moreover, it categorizes sensors as 'fat', 'healthy' or 'thin' to show the dense, optimal and scattered areas. It can also yield the largest empty area of sensors in the field. Simulation results show that the proposed DT method can achieve accurate coverage information, and provides many tools to compare QoC between different scenarios.
  3. Photocatalytic treatment of 4-chlorophenol in aqueous ZnO suspensions: intermediates, influence of dosage and inorganic anions
    Gaya UI, Abdullah AH, Zainal Z, Hussein MZ
    J Hazard Mater, 2009 Aug 30;168(1):57-63.
    PMID: 19268454 DOI: 10.1016/j.jhazmat.2009.01.130
    The photocatalytically driven removal of eco-persistent 4-chlorophenol from water using ZnO is reported here. Kinetic dependence of transformation rate on operating variables such as initial 4-chlorophenol concentration and photocatalyst doses was investigated. A complete degradation of 4-chlorophenol at 50 mg L(-1) levels was realised in 3h. Analytical profiles on 4-chlorophenol transformation were consistent with the best-line fit of the pseudo zero-order kinetics. The addition of small amounts of inorganic anions as SO(4)(2-), HPO(4)(-), S(2)O(8)(2-) and Cl(-) revealed two anion types: active site blockers and rate enhancers. Fortunately, Cl(-) and SO(4)(2-) commonly encountered in contaminated waters enhanced the rate of 4-chlorophenol degradation. The reaction intermediates and route to 4-chlorophenol mineralisation were elucidated by combined RP-HPLC and GC-MS methods. In addition to previously reported pathway products of 4-chlorophenol photo-oxidation catechol was detected. A radical mechanism involving o-hydroxylation is proposed to account for the formation of catechol.
  4. Fulltext Synthesis and evaluation of a molecularly imprinted polymer for 2,4-dinitrophenol
    Zakaria ND, Yusof NA, Haron J, Abdullah AH
    Int J Mol Sci, 2009 Jan;10(1):354-65.
    PMID: 19333450 DOI: 10.3390/ijms10010354
    Molecular imprinted polymers (MIP) are considered one of the most promising selective and novel separation methods for removal phenolic compound in wastewater treatment. MIP are crosslinked polymeric materials that exhibit high binding capacity and selectivity towards a target molecule (template), purposely present during the synthesis process. In this work MIP were prepared in a bulk polymerization method in acetonitrile using 2,4-dinitrophenol, acrylamide, ethylene glycol dimethacrylate, and benzoyl peroxide as template, functional monomer, cross-linker and initiator, respectively. An adsorption process for removal of nitrophenol using the fabricated MIP was evaluated under various pH and time conditions. The parameters studied for 2,4-dinitrophenol includes adsorption kinetics, adsorption isotherm, and selectivity. The maximum adsorption of nitrophenol by the fabricated MIP was 3.50 mg/g. The adsorption of 2,4-dinitrophenol by the fabricated MIP was found effective at pH 6.0. A kinetics study showed that nitrophenol adsorption follows a second order adsorption rate and the adsorption isotherm data is explained well by the Langmuir model.
  5. The use of classroom training and simulation in the training of medical responders for airport disaster
    Idrose AM, Adnan WA, Villa GF, Abdullah AH
    Emerg Med J, 2007 Jan;24(1):7-11.
    PMID: 17183034
    There is a dire need to have complementary form of disaster training which is cost effective, relatively easy to conduct, comprehensive, effective and acceptable. This will complement field drills training. A classroom-based training and simulation module was built by combining multiple tools: Powerpoint lectures, simulations utilising the Kuala Lumpur International Airport (KLIA) schematic module into 'floortop' model and video show of previous disaster drill. 76 participants made up of medical responders, categorised as Level 1 (specialists and doctors), Level 2 (paramedics), Level 3 (assistant paramedics) and Level 4 (health attendants and drivers) were trained using this module. A pre-test with validated questions on current airport disaster plans was carried out before the training. At the end of training, participants answered similar questions as post-test. Participants also answered questionnaire for assessment of training's acceptance. There was a mean rise from 47.3 (18.8%) to 84.0 (18.7%) in post-test (p<0.05). For Levels 1, 2, 3 and 4 the scores were 94.8 (6.3)%, 90.1 (11)%, 80.3 (20.1)% and 65 (23.4)% respectively. Nevertheless Level 4 group gained most increase in knowledge rise from baseline pre-test score (51.4%). Feedback from the questionnaire showed that the training module was highly acceptable. A classroom-based training can be enhanced with favourable results. The use of classroom training and simulation effectively improves the knowledge of disaster plan significantly on the back of its low cost, relatively-easy to conduct, fun and holistic nature. All Levels of participants (from specialists to drivers) can be grouped together for training. Classroom training and simulation can overcome the problem of "dead-document" phenomenon or "paper-plan syndrome".
  6. Fulltext An overview of data routing approaches for wireless sensor networks
    Anisi MH, Abdullah AH, Razak SA, Ngadi MA
    Sensors (Basel), 2012 03 27;12(4):3964-96.
    PMID: 23443040 DOI: 10.3390/s120403964
    Recent years have witnessed a growing interest in deploying large populations of microsensors that collaborate in a distributed manner to gather and process sensory data and deliver them to a sink node through wireless communications systems. Currently, there is a lot of interest in data routing for Wireless Sensor Networks (WSNs) due to their unique challenges compared to conventional routing in wired networks. In WSNs, each data routing approach follows a specific goal (goals) according to the application. Although the general goal of every data routing approach in WSNs is to extend the network lifetime and every approach should be aware of the energy level of the nodes, data routing approaches may focus on one (or some) specific goal(s) depending on the application. Thus, existing approaches can be categorized according to their routing goals. In this paper, the main goals of data routing approaches in sensor networks are described. Then, the best known and most recent data routing approaches in WSNs are classified and studied according to their specific goals.
  7. Fulltext Removal of toxic mercury from petroleum oil by newly synthesized molecularly-imprinted polymer
    Khairi NA, Yusof NA, Abdullah AH, Mohammad F
    Int J Mol Sci, 2015;16(5):10562-77.
    PMID: 26006226 DOI: 10.3390/ijms160510562
    In recent years, molecularly-imprinted polymers (MIPs) have attracted the attention of several researchers due to their capability for molecular recognition, easiness of preparation, stability and cost-effective production. By taking advantage of these facts, Hg(II) imprinted and non-imprinted copolymers were prepared by polymerizing mercury nitrate stock solution (or without it) with methacrylic acid (MAA), 2-hydroxyl ethyl methacrylate (HEMA), methanol and ethylene glycol dimethacrylate (EGDMA) as the monomer, co-monomer solvent (porogen) and cross-linker, respectively. Thus, the formed Hg(II) imprinted polymer was characterized by using Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), Brunauer, Emmett and Teller (BET) and thermal gravimetric analysis (TGA). The separation and preconcentration characteristics of Hg(II) imprinted polymer were investigated by solid phase extraction (SPE) procedures, and an optimal pH of 7 was investigated as ideal. The specific surface area of the Hg(II) imprinted polymer was found to be 19.45 m2/g with a size range from 100 to 140 µm in diameter. The maximum adsorption capacity was observed to be 1.11 mg/g of Hg(II) imprinted beads with 87.54% removal of Hg(II) ions within the first 5 min. The results of the study therefore confirm that the Hg(II) imprinted polymer can be used multiple times without significantly losing its adsorption capacity.
  8. Fulltext PES-Ag3PO4/g-C3N4 Mixed Matrix Film Photocatalyst for Degradation of Methyl Orange Dye
    Mukhair HM, Abdullah AH, Zainal Z, Lim HN
    Polymers (Basel), 2021 May 27;13(11).
    PMID: 34071758 DOI: 10.3390/polym13111746
    In the present study, we explored the effectiveness of PES-Ag3PO4/g-C3N4 film photocatalyst in degrading methyl orange dye under visible light irradiation. The PES-Ag3PO4/g-C3N4 film photocatalyst was prepared via a non-solvent-induced phase inversion process and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser scanning microscopy (LSM), X-ray photoelectron spectra (XPS), UV-diffuse reflectance (DRS), and water contact angle. The incorporation of the Ag3PO4/g-C3N4 composite into the PES matrix improved the pristine PES film's hydrophilicity, as evidenced by the reduction of water contact angle from 79.03° to 54.33° for a film containing 15 wt % of Ag3PO4/g-C3N4 composite. The film's photoactivity showed that 13 wt % was the best loading of Ag3PO4/g-C3N4 composite, and the degradation performance was maintained up to three cycles. The •O2- and h+ were the predominant species responsible for the methyl orange degradation.
  9. Cognitive reserve in stroke patients
    Abdullah AH, Sharip S, Rahman AHA, Bakar L
    Psych J, 2021 Jun;10(3):444-452.
    PMID: 33517588 DOI: 10.1002/pchj.423
    At present, a limited amount of information exists on the association between cognitive reserve and cognitive impairment in stroke populations. To determine predictors of cognitive reserve among stroke patients, 80 stroke patients attending the neurological and rehabilitation clinic in two different Malaysian general hospitals participated in this study. The Malay Cognitive Reserve Index questionnaire (CRIq-M), Depression Anxiety and Stress Scales-Short Form (DASS-21), WHO Quality of Life assessment BREF-21 (WHO-QOL BREF-21), Montreal Cognitive Assessment (MoCA), and modified Rankin Scale (mRS) were used as instruments in this study. The study found that cognitive reserve (CRIq-M) is positively correlated with cognitive function (MoCA), r = 0.529, p 
  10. Natural anti-aging skincare: role and potential
    Ahmed IA, Mikail MA, Zamakshshari N, Abdullah AH
    Biogerontology, 2020 06;21(3):293-310.
    PMID: 32162126 DOI: 10.1007/s10522-020-09865-z
    The deterioration of the skin morphology and physiology is the first and earliest obvious harbinger of the aging process which is progressively manifested with increasing age. Such deterioration affects the vital functions of the skin such as homeodynamic regulation of body temperature, fluid balance, loss of electrolytes and proteins, production of vitamin D, waste removal, immune surveillance, sensory perception, and protection of other organs against deleterious environmental factors. There are, however, harmful chemicals and toxins found in everyday cosmetics that consumers are now aware of. Thus, the natural beauty industry is on the rise with innovative technology and high-performance ingredients as more consumers demand healthier options. Therefore, the aims of this review are to give some critical insights to the effects of both intrinsic and extrinsic factors on excessive or premature skin aging and to elaborate on the relevance of natural beauty and natural anti-aging skincare approaches that will help consumers, scientists and entrepreneurs make the switch. Our recent investigations have shown the potential and relevance of identifying more resources from our rich natural heritage from various plant sources such as leaves, fruits, pomace, seeds, flowers, twigs and so on which can be explored for natural anti-aging skincare product formulations. These trending narratives have started to gain traction among researchers and consumers owing to the sustainability concern and impact of synthetic ingredients on human health and the environment. The natural anti-aging ingredients, which basically follow hormetic pathways, are potentially useful as moisturizing agents; barrier repair agents; antioxidants, vitamins, hydroxy acids, skin lightening agents, anti-inflammatory ingredients, and sunblock ingredients.
  11. TraPy-MAC: Traffic Priority Aware Medium Access Control Protocol for Wireless Body Area Network
    Ullah F, Abdullah AH, Kaiwartya O, Cao Y
    J Med Syst, 2017 Jun;41(6):93.
    PMID: 28466452 DOI: 10.1007/s10916-017-0739-y
    Recently, Wireless Body Area Network (WBAN) has witnessed significant attentions in research and product development due to the growing number of sensor-based applications in healthcare domain. Design of efficient and effective Medium Access Control (MAC) protocol is one of the fundamental research themes in WBAN. Static on-demand slot allocation to patient data is the main approach adopted in the design of MAC protocol in literature, without considering the type of patient data specifically the level of severity on patient data. This leads to the degradation of the performance of MAC protocols considering effectiveness and traffic adjustability in realistic medical environments. In this context, this paper proposes a Traffic Priority-Aware MAC (TraPy-MAC) protocol for WBAN. It classifies patient data into emergency and non-emergency categories based on the severity of patient data. The threshold value aided classification considers a number of parameters including type of sensor, body placement location, and data transmission time for allocating dedicated slots patient data. Emergency data are not required to carry out contention and slots are allocated by giving the due importance to threshold value of vital sign data. The contention for slots is made efficient in case of non-emergency data considering threshold value in slot allocation. Moreover, the slot allocation to emergency and non-emergency data are performed parallel resulting in performance gain in channel assignment. Two algorithms namely, Detection of Severity on Vital Sign data (DSVS), and ETS Slots allocation based on the Severity on Vital Sign (ETS-SVS) are developed for calculating threshold value and resolving the conflicts of channel assignment, respectively. Simulations are performed in ns2 and results are compared with the state-of-the-art MAC techniques. Analysis of results attests the benefit of TraPy-MAC in comparison with the state-of-the-art MAC in channel assignment in realistic medical environments.
  12. Accurate and dynamic predictive model for better prediction in medicine and healthcare
    Alanazi HO, Abdullah AH, Qureshi KN, Ismail AS
    Ir J Med Sci, 2018 May;187(2):501-513.
    PMID: 28756541 DOI: 10.1007/s11845-017-1655-3
    INTRODUCTION: Information and communication technologies (ICTs) have changed the trend into new integrated operations and methods in all fields of life. The health sector has also adopted new technologies to improve the systems and provide better services to customers. Predictive models in health care are also influenced from new technologies to predict the different disease outcomes. However, still, existing predictive models have suffered from some limitations in terms of predictive outcomes performance.

    AIMS AND OBJECTIVES: In order to improve predictive model performance, this paper proposed a predictive model by classifying the disease predictions into different categories. To achieve this model performance, this paper uses traumatic brain injury (TBI) datasets. TBI is one of the serious diseases worldwide and needs more attention due to its seriousness and serious impacts on human life.

    CONCLUSION: The proposed predictive model improves the predictive performance of TBI. The TBI data set is developed and approved by neurologists to set its features. The experiment results show that the proposed model has achieved significant results including accuracy, sensitivity, and specificity.

  13. Fabrication of calix[4]arene/polyurethane for the adsorptive removal of cationic dye from aqueous solutions
    Ishak S, Rosly NZ, Abdullah AH, Alang Ahmad SA
    Environ Monit Assess, 2023 Oct 12;195(11):1303.
    PMID: 37828347 DOI: 10.1007/s10661-023-11909-z
    Calix[4]arene/polyurethane (C4PU) has been synthesized and characterized as an alternative adsorbent for the adsorption of methylene blue (MB) and malachite green (MG) dyes from the aqueous solution. C4PU was synthesized by reacting p-tert-butyl calix[4]arene with hexamethylene diisocyanate (HMDI) as the cross-linking agent. Different polymer ratios were synthesized, and C4PU-4 shows better adsorption than other ratios. The polymer was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) analysis, and point of zero charges (pHPZC). The isotherms and kinetics of the adsorption of MB and MG were studied under a range of experimental conditions, including pH, adsorbent dosage, initial dye concentration, and contact time. The adsorption was determined by the adsorption percentage of MB and MG dyes from the solution. The Langmuir isotherm model best describes the adsorption process for both dyes, and it follows a pseudo-second-order kinetic model, with the maximum adsorption capacity (qmax) of MB and MG, respectively, was found to be 1.991 mg·g-1 and 2.240 mg·g-1.
  14. Fulltext Functionalized Activated Carbon Derived from Palm Kernel Shells for the Treatment of Simulated Heavy Metal-Contaminated Water
    Baby R, Hussein MZ, Zainal Z, Abdullah AH
    Nanomaterials (Basel), 2021 Nov 20;11(11).
    PMID: 34835897 DOI: 10.3390/nano11113133
    Heavy metal contamination in water poses a great risk to human health as well as to the lives of other creatures. Activated carbon is a useful material to be applied for the treatment of heavy metal-contaminated water. In this study, functionalized activated carbon (FAC) was produced by the induction of nitro groups onto activated carbon using nitric acid. The resulting material was characterized in detail using the XRD, Raman, BET, FTIR, and FESEM techniques. The FAC was used for the treatment of heavy metal-contaminated water using different adsorption parameters, i.e., solution pH, contact time, adsorbent dosage and heavy metal ion concentrations, and these parameters were systematically optimized. It was found that FAC requires 90 min for the maximum adsorption of the heavy metal ions; Cr6+, Pb2+, Zn2+ and Cd2+. The kinetic study revealed that the metal ion adsorption follows the pseudo-second-order. The Freundlich and Langmuir isotherms were applied to determine the best fitting adsorption isotherm models. The adsorption capacities were also determined for each metal ion.
  15. Fulltext An experimental investigation into the rheological behavior and filtration loss properties of water-based drilling fluid enhanced with a polyethyleneimine-grafted graphene oxide nanocomposite
    Abdullah AH, Ridha S, Mohshim DF, Maoinser MA
    RSC Adv, 2024 Mar 26;14(15):10431-10444.
    PMID: 38572346 DOI: 10.1039/d3ra07874d
    The modern oil and gas industry, driven by a surging global energy demand, faces the challenge of exploring deeper geological formations. Ensuring the robust performance of drilling fluids under harsh wellbore conditions is paramount, with elevated temperatures and salt contamination recognized as detrimental factors affecting the rheological and filtration loss properties of drilling fluids. We successfully synthesized a polyethyleneimine-grafted graphene oxide nanocomposite (PEI-GO), and its functional groups formation and thermal stability were verified through Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). Our findings demonstrated a significant improvement in the plastic viscosity and yield point of the base drilling fluid with the addition of PEI-GO. The inclusion of 0.3 wt% PEI-GO outperformed the base drilling fluid at 160 °C, improving the yield point/plastic viscosity (YP/PV) value and reducing filtration loss volume by 42% and 67%, respectively. The Herschel-Bulkley model emerged as the superior choice for characterizing rheological behavior. PEI-GO exhibited compatibility with high-salt formations, maintaining satisfactory filtration volumes even when subjected to sodium chloride (NaCl) and calcium chloride (CaCl2) contamination concentrations of up to 20 and 10 wt%, respectively. The remarkable rheological and filtration properties of PEI-GO are attributed to its electrostatic interactions with clay particles through hydrogen and ionic bonding. These interactions lead to pore plugging in the filter cake, effectively preventing water infiltration and reducing filtration loss volume. This study emphasizes the potential of PEI-GO in water-based drilling fluids, particularly in high-temperature and salt-contaminated environments.
  16. Fulltext Performance improvement in geographic routing for Vehicular Ad Hoc Networks
    Kaiwartya O, Kumar S, Lobiyal DK, Abdullah AH, Hassan AN
    Sensors (Basel), 2014;14(12):22342-71.
    PMID: 25429415 DOI: 10.3390/s141222342
    Geographic routing is one of the most investigated themes by researchers for reliable and efficient dissemination of information in Vehicular Ad Hoc Networks (VANETs). Recently, different Geographic Distance Routing (GEDIR) protocols have been suggested in the literature. These protocols focus on reducing the forwarding region towards destination to select the Next Hop Vehicles (NHV). Most of these protocols suffer from the problem of elevated one-hop link disconnection, high end-to-end delay and low throughput even at normal vehicle speed in high vehicle density environment. This paper proposes a Geographic Distance Routing protocol based on Segment vehicle, Link quality and Degree of connectivity (SLD-GEDIR). The protocol selects a reliable NHV using the criteria segment vehicles, one-hop link quality and degree of connectivity. The proposed protocol has been simulated in NS-2 and its performance has been compared with the state-of-the-art protocols: P-GEDIR, J-GEDIR and V-GEDIR. The empirical results clearly reveal that SLD-GEDIR has lower link disconnection and end-to-end delay, and higher throughput as compared to the state-of-the-art protocols. It should be noted that the performance of the proposed protocol is preserved irrespective of vehicle density and speed.
  17. Fulltext A novel DNA nanosensor based on CdSe/ZnS quantum dots and synthesized Fe3O4 magnetic nanoparticles
    Hushiarian R, Yusof NA, Abdullah AH, Ahmad SA, Dutse SW
    Molecules, 2014 Apr 09;19(4):4355-68.
    PMID: 24722589 DOI: 10.3390/molecules19044355
    Although nanoparticle-enhanced biosensors have been extensively researched, few studies have systematically characterized the roles of nanoparticles in enhancing biosensor functionality. This paper describes a successful new method in which DNA binds directly to iron oxide nanoparticles for use in an optical biosensor. A wide variety of nanoparticles with different properties have found broad application in biosensors because their small physical size presents unique chemical, physical, and electronic properties that are different from those of bulk materials. Of all nanoparticles, magnetic nanoparticles are proving to be a versatile tool, an excellent case in point being in DNA bioassays, where magnetic nanoparticles are often used for optimization of the hybridization and separation of target DNA. A critical step in the successful construction of a DNA biosensor is the efficient attachment of biomolecules to the surface of magnetic nanoparticles. To date, most methods of synthesizing these nanoparticles have led to the formation of hydrophobic particles that require additional surface modifications. As a result, the surface to volume ratio decreases and nonspecific bindings may occur so that the sensitivity and efficiency of the device deteriorates. A new method of large-scale synthesis of iron oxide (Fe3O4) nanoparticles which results in the magnetite particles being in aqueous phase, was employed in this study. Small modifications were applied to design an optical DNA nanosensor based on sandwich hybridization. Characterization of the synthesized particles was carried out using a variety of techniques and CdSe/ZnS core-shell quantum dots were used as the reporter markers in a spectrofluorophotometer. We showed conclusively that DNA binds to the surface of ironoxide nanoparticles without further surface modifications and that these magnetic nanoparticles can be efficiently utilized as biomolecule carriers in biosensing devices.
  18. Adsorptive performance of penta-bismuth hepta-oxide nitrate, Bi₅O₇NO₃, for removal of methyl orange dye
    Abdullah AH, Abdullah EA, Zainal Z, Hussein MZ, Ban TK
    Water Sci Technol, 2012;65(9):1632-8.
    PMID: 22508126 DOI: 10.2166/wst.2012.057
    The adsorption of methyl orange dye from aqueous solution onto penta-bismuth hepta-oxide nitrate, Bi(5)O(7)NO(3), synthesized by precipitation method, was studied in a batch adsorption system. The effects of operation parameters such as adsorbent dose, initial dye concentration, pH and temperature were investigated. The adsorption equilibrium and mechanism of adsorption was evaluated by Langmuir and Freundlich isotherm and different kinetic models, respectively. The results indicate that adsorption is highly dependent on all operation parameters. At optimum conditions, the adsorption capacity was found to be 18.9 mg/g. The adsorption data fits well with the Langmuir isotherm model indicating monolayer coverage of adsorbate molecules on the surface of Bi(5)O(7)NO(3). The kinetic studies show that the adsorption process is a second-order kinetic reaction. Although intra-particle diffusion limits the rate of adsorption, the multi-linearity plot of intra-particle model shows the importance of both film and intra-particle diffusion as the rate-limiting steps of the dye removal. Thermodynamic parameters show that the adsorption process is endothermic, spontaneous and favourable at high temperature.
  19. Fulltext Time-dependent effect in green synthesis of silver nanoparticles
    Darroudi M, Ahmad MB, Zamiri R, Zak AK, Abdullah AH, Ibrahim NA
    Int J Nanomedicine, 2011;6:677-81.
    PMID: 21556342 DOI: 10.2147/IJN.S17669
    The application of "green" chemistry rules to nanoscience and nanotechnology is very important in the preparation of various nanomaterials. In this work, we successfully developed an eco-friendly chemistry method for preparing silver nanoparticles (Ag-NPs) in natural polymeric media. The colloidal Ag-NPs were synthesized in an aqueous solution using silver nitrate, gelatin, and glucose as a silver precursor, stabilizer, and reducing agent, respectively. The properties of synthesized colloidal Ag-NPs were studied at different reaction times. The ultraviolet-visible (UV-vis) spectra were in excellent agreement with the obtained nanostructure studies performed by transmission electron microscopy (TEM) and their size distributions. The prepared samples were also characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). The use of eco-friendly reagents, such as gelatin and glucose, provides green and economic attributes to this work.
  20. TiO2/Ag modified penta-bismuth hepta-oxide nitrate and its adsorption performance for azo dye removal
    Abdullah EA, Abdullah AH, Zainal Z, Hussein MZ, Ban TK
    J Environ Sci (China), 2012;24(10):1876-84.
    PMID: 23520859
    A modified hydrophilic penta-bismuth hepta-oxide nitrate (Bi5O7NO3) surface was synthesized via a precipitation method using TiO2 and Ag as modified agents. The synthesized product was characterized by different analytical techniques. The removal efficiency was evaluated using mono- and di-sulphonated azo dyes as model pollutants. Different kinetic, isotherm and diffusion models were chosen to describe the adsorption process. X-ray photoelectron spectroscopy (XPS) results revealed no noticeable differences in the chemical states of modified adsorbent when compared to pure Bi5O7NO3; however, the presence of hydrophilic centres such as TiO2 and Ag developed positively charged surface groups and improved its adsorption performance to a wide range of azo dyes. Dyes removal was found to be a function of adsorbent dosage, initial dye concentration, solution pH and temperature. The reduction of Langmuir 1,2-mixed order kinetics to the second or first-order kinetics could be successfully used to describe the adsorption of dyes onto the modified adsorbent. Mass transfer can be described by intra-particle diffusion at a certain stage, but it was not the rate limiting step that controlled the adsorption process. Homogenous behavior of adsorbent surface can be explored by applying Langmuir isotherm to fit the adsorption data.
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