Biological, chemical and mathematical sciences

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Browsing Biological, chemical and mathematical sciences by Subject "Adsorption—Materials—Environmental aspects"

Now showing 1 - 5 of 5
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    Henna extract as a potential sacrificial agent in reducing surfactant adsorption onto quartz sand and kaolinite
    (Universiti Teknologi Malaysia, 2019) Mohd Musa, Mohd. Syazwan
    Surfactant flooding is one of enhanced oil recovery techniques to increase oil recovery. However, the main concern of this technique is the adsorption of surfactant onto reservoir rock which can reduce the effectiveness of the surfactant in reducing interfacial tension of oil and water. In this case, surfactant adsorption is normally reduced with the help of a sacrificial agent (SA). Studies have recently discovered the potential of plant extracts as an environmentally friendly and easily available alternative to chemical SAs. The main objective of this study is to evaluate the performance of henna extract as a SA in reducing surfactant adsorption. First, henna leaves were extracted and characterised to determine the functional groups responsible for adsorption. The ability of the henna extract to adsorb onto quartz sand and kaolinite was then analysed. Moreover, the adsorption limitation of the henna extract onto both quartz sand and kaolinite in different salinities, pH, and temperature was investigated. Finally, the performance of the surfactant adsorption onto quartz sand and kaolinite in the presence of the henna extract was evaluated. The results show that phenolic compounds are responsible for adsorption of the henna extract. Besides, twice the amount of henna extract was adsorbed onto kaolinite than quartz sand. Also, the henna extract managed to adsorb further when salinity was increased and pH was lowered. However, the adsorption of henna extract reduced with increasing temperature. The adsorption of henna extract is mainly through hydrogen bonding and electrostatic attractions while hydrophobic interactions play a minor role in the adsorption process. The henna extract reduced surfactant adsorption onto quartz sand and kaolinite by 46% and 55%, respectively, in 30,000 mg/L of NaCl. At pH 3, the surfactant adsorbed onto quartz sand and kaolinite was reduced by 32% and 39% respectively. Meanwhile, at 25oC, the surfactant adsorption onto quartz sand and kaolinite was reduced by 23% and 36%, respectively. This finding proves the profound reduction in surfactant adsorption with the addition of henna extract, suggesting the possibility of utilising the extract as a sacrificial agent to reduce surfactant adsorption. In conclusion, the adsorption behaviour of henna extract in different salinity, pH, and temperature was successfully demonstrated and the henna extract was found effective as a sacrificial agent in reducing surfactant adsorption.
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    One-step synthesis and adsorptive characteristics of composite magnetic activated carbon for rhodamine B removal
    (Universiti Teknologi Malaysia, 2019) Lee, Lin Zhi
    Most of adsorption research has been carried out with dyes since their existence affects not only the quality of water but also changes the aquatic ecosystems as well as reduces the light penetration. Fine activated carbons are effective in dye adsorption, but they are extremely difficult to be separated from the solution when the carbons become exhausted. Magnetic activated carbon (MAC) has an advantage for the separation of spent activated carbon due to its excellent magnetic properties. However, complicated and multiple steps in the preparation process, and smaller adsorption capacity as compared to conventional activated carbon are the significant drawbacks of magnetic activated carbon. A simple synthesis method which simultaneously involves the activation and magnetization in a single step was introduced. This work was aimed at evaluating the adsorptive properties of composite magnetic activated carbons prepared from palm kernel shell. The activated carbons were prepared at various impregnation ratios of ZnCl2 and FeCl3, activation temperatures ranging between 300 and 800oC and times of 1 to 3 h. ZMAC-2.5 prepared at 600oC and 2 h with impregnation ratios of ZnCl2:FeCl3:PKS = 1.5:1.0:1.0, which has BET surface area of 1775 m2/g and mesoporosity of 93.8 % endowed a higher rhodamine B (RB) adsorption of 371 mg/g. For the purpose of comparison, MACs prepared by conventional magnetization methods and non-magnetic activated carbon (ZAC-1.5) were also employed in adsorption studies. MACs were characterized based on proximate analysis, elemental analysis, textural characteristics, chemical properties and magnetic properties. The batch adsorption was evaluated for equilibrium isotherm, kinetics and thermodynamics properties of RB by MACs. Langmuir isotherm model gave the best conformity of equilibrium data indicating a monolayer adsorption of RB onto activated carbons. The kinetics data were fitted better with pseudo-second-order model. The intraparticle diffusion and Boyd models revealed that both film and pore diffusion may be involved in the adsorption process, but none is the sole rate-limiting step. The positive values of enthalpy change and entropy change indicate that the adsorption process is endothermic and spontaneous at high temperature. The activation energy of 24.1 - 28.9 kJ/mol suggested that the adsorption of RB onto ZMAC-2.5 is a physisorption process. In fixed bed adsorption, the effect of initial RB concentration, flow rate and bed height were evaluated. The increase in initial concentration or flow rate, or the decrease in bed height could result in increasing adsorption capacity but decreasing breakthrough time. The column data fitted well with Thomas, Yoon-Nelson and Bohart-Adams models with high coefficient of determination (R2) and low sum of squared errors (SSE). These models describe that the adsorption process is controlled by the interaction between RB molecules and ZMAC-2.5 surface. In hot water regeneration studies, ZMAC-2.5 showed a higher recovery than ZAC-1.5 for three consecutive regeneration cycles due to its magnetic properties. The optimum conditions were found to be 68.3 oC and 1 h to achieve the regeneration efficiency of 36.8 % and recovery of 93.7 %. Magnetic activated carbon showed a great potential to ease the separation of exhausted activated carbon using permanent magnet in wastewater treatment.
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    Synthesis and characterization of surface modified banana trunk as absorbent for benzene removal from aqueous solution
    (Universiti Teknologi Malaysia, 2017) Kong, Helen
    Petroleum monoaromatics especially benzene contamination in water and wastewater is the major concern in the industry today. Various removal techniques have been studied. The adsorptive removal process is considered as one of the most cost-efficient and feasible methods because it does not require a large amount of energy and additional chemical. In adsorption technology, several problems such as adsorbent cost, adsorption selectivity and adsorbent reusability are the main concerns. Therefore, the potential conversion and modification of agrowaste adsorbent into an effective adsorbent alternative to removing benzene constituent from the wastewater were studied. The banana trunk (BT) was selected as an agrowaste model in the present study. The raw BT (Raw-BT) was first mercerized and this mercerized BT (M-BT) was then reacted with different surfactants, namely cetyltrimethylammonium bromide, CTAB (M-CTAB-BT), 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol, Triton X-100 (M-TX100-BT) and sodium dodecyl sulfate, SDS (M-SDS-BT). Surface etherification was also conducted by using 3-chloro-2-hydroxypropyl trimethylammonium chloride, CTA with the mass ratio of 1 and this etherified BT (M-1CTA-BT) was then coated with SDS (M-1CTA-SDS-BT). All the adsorbents were characterized by using a Fourier transform infrared spectrometer, a field emission scanning electron microscope, an x-ray photoelectron spectroscopy analyzer and nitrogen adsorption/desorption analysis. The experimental batch adsorption studies showed that the adsorption capacity increased in the following order: Raw-BT < M-BT < M-CTAB-BT < M-TX100-BT < M-1CTA-SDS-BT. The Langmuir maximum benzene adsorption capacity, qL,max achieved by the M-1CTA-SDS-BT was 468.187 × 10-3 mmol/g. The fundamental adsorption equilibrium and kinetic studies revealed that the benzene adsorption data were fitted well into the Langmuir isotherm and pseudo-second order kinetic models which suggested that the adsorption process was governed by a physical phenomenon. The film diffusion was considered as the rate-limiting step for the overall benzene adsorption process. The adsorbents were chemically stable within the pH range. It was revealed the benzene adsorption was an endothermic and non-spontaneous process. The regeneration study using 50 % ethanol-water as the desorbing agent, demonstrated that the modified adsorbents could withstand five adsorption/desorption cycles without a drastic reduction of adsorption uptake (8.5 - 13.0 %). The BT could potentially be employed as an adsorbent precursor for benzene adsorptive removal from aqueous solution
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    Synthesis of nickel-cobalt-iron supported alumina composite via electrolysis for palladium ions adsorption
    (Universiti Teknologi Malaysia, 2016) Muhamad Salleh, Nur Fatien
    The discharge of palladium (Pd) effluents from industries may cause serious environmental effect to aquatic life and humans due to its toxicity and harmful effects. Thus, the removal of Pd from an aquatic system is very crucial and this process can be achieved by the adsorption method. In this study, nickel loaded alumina (Al2O3) was prepared by electrochemical (NiAl) and physical method for the adsorption of Pd from an aqueous solution. Due to the higher adsorptivity shown by the electrochemical method, the performance of electrochemically prepared cobalt (Co) and iron (Fe) onto NiAl with different metal loading (3-10 wt%) were also investigated. The adsorbents were characterized using x-ray diffraction, Fourier transform infrared spectroscopy, surface area analysis, transmission electron microscopy, electron spin resonance spectrometer, and vibrating sample magnetometer. The adsorption of Pd was conducted in a batch system under varying initial pH (3-8), adsorbent dosage (0.005- 0.05 g), initial concentration (10-100 mg L-1) and temperature (303-323 K). The adsorptivity of those adsorbents toward Pd ions is in the following order: FeCoNiAl > CoNiAl > NiAl > cobalt oxide > iron oxide > nickel oxide. The FeCoNiAl was able to remove the Pd with an adsorption capacity of 250 mg g-1 at pH 5 when using 0.05 g adsorbent, initial concentration of 75 mg L-1 at 303 K. The characterization result revealed that adsorptivity was significantly affected by the formation of metal spinel which induced the magnetism properties. Besides, the hydrogen atoms of hydroxyl (– OH) groups on the surface of Al2O3 also exchanged with the Pd ions. The consecutive addition of metals led to a greater formation of surface –OH, oxygen defects as well as spinel phases that contributed to a higher degree of magnetism, which provide more adsorption sites for the Pd ions. The equilibrium data followed the Langmuir model and the kinetics was best described by the pseudo-first-order model, while the thermodynamic study indicated that the adsorption was exothermic. Further optimization by the response surface methodology with a central composite design model was performed and the results showed that the reaction temperature plays a major role for the adsorption, which most probably affected the magnetism of the composites. This study provides a new perspective in the synthesis of composites with superior properties for the removal of Pd ions as well as for other applications
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    Synthesis, characterization and performance of adsorbents for mercury vapor removal
    (Universiti Teknologi Malaysia, 2015) Johari, Khairiraihanna
    Mercury pollution is a growing concern due to its toxicity, volatility, and bioaccumulation in the environment. The main and most problematic source of mercury emission comes from the coal-fired power plants and gas processing activities. Hence, mercury needs to be removed and adsorption has been proven to be an excellent method due to easiness of operation and efficiency. In this study, coconut husk such as coconut pith and fiber were used as alternative low-cost adsorbents in exchange to the existing conventional elemental mercury (Hgo) adsorbents. The potential use of coconut based-adsorbents for elemental mercury removal from gas streams has not yet been fully explored due to lack of research in this regard. This research focused on synthesis and modifications of coconut husk such as surface, carbonization and sulfurization treatments in order to enhance elemental mercury adsorption performance. The adsorbents were characterized using proximate analysis, scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, nitrogen adsorption/desorption (NAD), carbon-hydrogennitrogen- sulfur (CHNS) analysis and X-ray photoelectron spectroscopy (XPS) measurement. The Hgo adsorption experiments were conducted using a conventional flow type packed-bed reactor system with nitrogen as carrier gas. The results show that the chemical, physical, morphological and spectral properties of the adsorbents were greatly influenced by the modification methods used. Adsorbents obtained through carbonization and sulfurization treatments produced the best Hgo adsorption capacity. The experimental data exhibited that the increase of thermal carbonization up to 900 °C, resulted in high adsorption capacity of 6067.49 µg/g. The sulfurization at lower temperature (i.e. CPS300) resulted in the highest adsorption capacity (26077.69 M-g/g). Enhancement in Hgo adsorption capacity might due to the higher sulfur compounds on the surface which acts as active site towards elemental mercury. The adsorption data revealed that the adsorbent with larger equilibrium adsorption capacity possessed poor adsorption reaction kinetics and diffusion process. This study also revealed that the char adsorbent could sustain Hgo adsorption capacity over multiple regeneration cycles. However, sulfurized-char is non-regenerative adsorbent, which can be utilized for longer adsorption process. Finally, the present findings indicate that the coconut husk can be potential low-cost elemental mercury adsorbents by applying appropriate modifications such as carbonization and sulfurization treatments. In addition, the utilization of coconut husks can reduce waste disposal problems and thus improving environmental quality and sustainability