Physics, Engineering and Material Science

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Browsing Physics, Engineering and Material Science by Subject "Adsorption—Materials"

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    Development of adsorbents from rice residues for mercury removal process
    (Universiti Teknologi Malaysia, 2017) Song, Shiow Tien
    Mercury is one of the heavy metals considered as a serious toxic to both human and the environment. Conventional treatment technologies for the removal of mercury commonly suffer some limitations like high operating cost, incomplete precipitation, and sludge generation. Adsorption which has been proven as an effective separation process for a wide variety of applications emerged as a solution. In this study, rice residues (rice husk and rice straw) were utilized as potential lowcost adsorbent for removing mercury from aqueous solution. The modification of adsorbent such as grafting with organosilane, carbonization and chemical activation process was carried out to enhance its adsorption capacity. The synthesized adsorbents were characterized using proximate analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, elemental analysis, nitrogen adsorption/desorption analysis and surface acidity test. The effects of operational parameters such as pH, initial concentration, contact time and temperature were investigated in batch adsorption experiment. The experimental data were correlated with several isotherm and kinetic models for the determination of the adsorption potential. Based on the analyses, the mercury adsorption process was mainly controlled by film diffusion and chemical process mechanism. It was found that samples RSGM (grafting with organosilane), RSCC300 (dry pyrolysis), RHT300 (wet pyrolysis) and RSACS (single-step acid activation) showed highest adsorption rate with 98.98 %, 98.96 %, 97.17 % and 99.12 %, respectively. The selected adsorbents were further investigated in continuous adsorption mode for the possible scale-up studies. The effect of flow rate, bed-height and inlet ion concentration on the adsorption characteristics were investigated in a fixed-bed adsorber. The isotherm data of continuous adsorption were best fitted to the Langmuir isotherm model, while the breakthrough data were found to be in good agreement with the Yoon-Nelson models for all experimental conditions used. The adsorbent regeneration results indicated a good adsorption-desorption process reversibility in both batch and continuous system. The process design of the fixed-bed adsorber was successfully demonstrated by using the height of an equivalent transfer unit and empty bed contact time analysis to predict the breakthrough curves of the scale-up adsorber. The adsorption efficiency of the adsorbent was also evaluated by measuring the extent of adsorption of mercury in oil-field produced water. The use of rice residues to remove mercury leads to the production of a highly effective adsorbent generated from less expensive raw materials from renewable resources
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    Modifications of coconut pith as mercury adsorbents for industrial applications
    (Universiti Teknologi Malaysia, 2016) Saman, Norasikin
    Contamination of wastewater by mercury ions poses a great concern due to its toxicity and threat to the public health and ecological systems. This study was conducted to investigate utilization of coconut pith (CP) as adsorbents for the removal of mercury ions, Hg(II) and MeHg(II). The CP underwent several modification processes: pre-treatment; silane-grafting and dye-loading, aiming for better Hg(II) and MeHg(II) adsorption performance. The adsorption performance study was conducted in batch and continuous adsorption system. The physical and chemical properties of CP adsorbents changed after modifications. The silanegrafting using mercaptopropyltriethoxysilane (CP-MPTES) and dye-loading using Reactive Red 120 (CP-RR) resulted in the highest removal efficiency towards both mercury ions. This is due to the presence of functional groups which have high affinity towards both mercury ions. Batch adsorption studies found that the adsorption capacity of both mercury ions was dependent on initial pH, adsorbent dosage, initial concentration, contact time and temperature. The maximum adsorption capacity of Hg(II) onto CP-Pure, CP-MPTES and CP-RR was 2.60, 2.61, and 2.60 mmol/g, while 0.50, 1.13 and 0.76 mmol/g was observed for MeHg(II), respectively. The equilibrium and kinetic data analyses found that the mechanism of mercury ions adsorption onto CP adsorbents is a combination of physical and chemical processes. The high regenerability was only observed in Hg(II) adsorption. The competence of Hg(II) and MeHg(II) adsorption in oilfield produced water and natural gas condensate samples, respectively, found that the presence of other metal ions reduced the adsorption performance of the mercury ions. The mercury ion adsorption in continuous fixed-bed adsorber studied at various conditions showed that the increase of flow rate and initial concentration caused the exhaustion time (texh) to occur earlier, but higher bed height prolonged the texh. The breakthrough curves of mercury ions adsorption were analyzed using Thomas, Bohart-Adam, Yoon-Nelson, Wolborska and Clark models. Thomas and Yoon-Nelson models fit most of the experimental data. However, empty bed contact time analysis found that the Yoon-Nelson model is more applicable to predict the breakthrough curves of the scale-up adsorber. The regenerability studies had low performance towards Hg(II) adsorption and fair performance towards MeHg(II) adsorption. In overall, the batch and continuous mercury ion adsorption results show the potential application of the CP adsorbents as low-cost adsorbent for industrial mercury ion removal process