Pusat Pengajian Kejuruteraan Kimia - Tesis

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Polyvinylidene fluoride/calcium carbonate membranes with the nonwetted and wetted surface for dual-phase separation
(2024-09)
Sarah Qistina binti Zaliman
Dual-phase separation using membranes involves the permeation of target compounds between gas-liquid and liquid-liquid phases. However, the permeation can be restricted by surface wetting important. In this work, poly(vinylidene fluoride) (PVDF) membranes with switchable surface wetting were developed through nanoparticle incorporation and 3D-imprinting, followed by drying or wetting after phase inversion. In order to achieve the nanoroughness, low cost and biocompatible calcium carbonate (CaCO3) nanoparticles were introduced into PVDF dope solution. A micro-roughness was imprinted on the membrane by phase inversion in a water bath after casting on a woven support. For nanotemplating, the nanoparticles were premodified using stearic acid to reduce surface energy or removed using ethylenediaminetetraacetic acid. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to observe the presence of CaCO3 nanoparticles. As a result of the addition of CaCO3 and stearic acid-modified CaCO3 (SA-CaCO3), the membrane pore size and porosity were significantly improved due to demixing during phase inversion. Removing CaCO3 nanoparticles using ethylenediaminetetraacetic acid enlarged the pore size greatly. PVDF/CaCO3 and PVDF/SA- CaCO3 membranes attained superhydrophobic surface after drying. Working as the membrane gas contactor, the PVDF membrane incorporated with SA-CaCO3 reached a high CO2 permeation flux of 1.86 ±0.05×10-2 mol m-2 s-1 and slight changes in surface hydrophobicity after 50 h of being immersed in amine solution. On the other hand, the hydrophobic PVDF and PVDF/SA-CaCO3 membranes developed in this work were rinsed with absolute ethanol and immersed in distilled water to attain a wetted surface. The non-wetted and wetted membranes were then tested in the separation of oil in water (O/W) and water in oil emulsion (W/O), respectively. A dead-end filtration setup was used to examine their separation efficiency for the liquid-liquid phase under the operating pressure of 0.2 bar (O/W) or 1 bar (W/O). The oil (O/W) could be separated effectively without significant fouling due to the formation of an underwater oleophobic surface. However, the removal of water (W/O) was considerably inefficient slow due to the large pore size.
Adsorption of acetaminophen and Chloramphenicol by corn cob based Activated carbon: experimental and Modelling analysis
(2024-09-01)
Mohamad Razif, Mohd Ramli
The wastewater containing pharmaceutical compounds has threatened human health and aquatic life. Previous studies have explored various types of activated carbon derived from agricultural waste for the adsorption of pharmaceutical compounds. They often face limitations such as low adsorption capacity, non- optimized preparation conditions, and the use of non-renewable precursors. So far, there has been limited research focusing on optimizing the preparation and application of corn cob based activated carbon specifically for the adsorption of acetaminophen and chloramphenicol with different molecular structure and characteristics. This study aims to produce corn cob based activated carbon (CCAC) for the adsorption of pharmaceutical compounds, namely acetaminophen (ACP) and chloramphenicol (CP). The CCAC was prepared via a physicochemical activation method and optimized using response surface methodology. From the analysis of variance (ANOVA), all developed models have shown significance, with p-values less than 0.05. The optimum preparation conditions were found to be 3.86 min for activation time, 616 watt of radiation power, and 2.5 g/g for impregnation ratio (IR), which resulted in 16.6% of CCAC’s yield, with adsorption capacities of 22.3 mg/g for ACP and 20.2 mg/g for CP. The CCAC exhibited favourable characteristics in terms of BET surface area, mesopore surface area, pore volume, and pore diameter, which were 976.29 m 2 /g, 2 631.48 m /g, 0.3933 cm 3 /g, and 2.38 nm, respectively. CCAC showed adsorption capacities of 22.43 and 20.68 mg/g, respectively for ACP and CP adsorption at 30 °C. The adsorption of ACP and CP onto CCAC followed Langmuir and Freundlich isotherms, respectively. For ACP-CCAC and CP-CCAC adsorption system, the kinetic of adsorption followed a pseudo-second order and pseudo-first order kinetic models, respectively. Thermodynamic studies confirmed that the ACP-CCAC and CP-CCAC exhibit endothermic nature. The mass transfer (MT) model indicated the calculated adsorption capacity of 21.14 mg/g and 21.48 mg/g for adsorption of ACP and CP, respectively. The artificial neural network (ANN) is applied in this study because of its ability to accurately model complex, non-linear relationships in the adsorption process, optimize process parameters, and provide reliable predictions. This application contributes to a deeper understanding and enhancement of the adsorption capacity of CCAC for pharmaceutical compounds. The Levenberg-Marquardt (LM) algorithm was used to train 164 experimental data points input (contact time, initial concentration, temperature, and pH) into the ANN model to predict adsorption capacity. The predicted and actual values of the desired output variables achieved an 2 R above 0.90 for training, validation, and testing. Improvements in mean square error and test error resulted in the optimal number of neurons in the hidden layers (NHL) decreasing from 12 to 5 for CP adsorption. However, the optimal NHL remained at 10 neurons for ACP adsorption. The developed framework can predict the adsorption capacity of adsorbents for adsorbates.
Development and modification of leucaena wood-derived adsorbent for carbon dioxide capture
(2024-09-01)
Nuradibah, Mohd Amer
The persistent increase in carbon dioxide (CO2) concentration in the atmosphere, which is the main anthropogenic greenhouse gas causing tremendous impacts on global warming, highlights the necessity for research focused on carbon capture and storage (CCS). The unique properties of biochar prove its ability as a promising carbon-based material as CO2 capturing medium at low adsorption temperature. This work aims to highlight the development of biochar from woody biomass feedstock, specifically Leucaena wood (LW) and its subsequent modification for post combustion CO2 capture. Accordingly, slow pyrolysis was performed to develop biochar at different temperatures of 500, 700 and 900 ℃. Biochar produced at 900 ℃ showed the highest CO2 capture capacity of 52.18 mg/g compared to the ones pyrolyzed at 500 and 700 ℃. Subsequently, different vanadium oxide loadings (1, 3, 4, 5, and 8 %) were introduced to biochar’s structure via impregnation method to increase its surface basicity which is favourable to interact with acidic CO2 molecules. The finding revealed that an increment of 38.3 % in adsorption capacity (72.14 mg/g) to the pristine biochar when impregnated with 4 % of vanadium. Considering that high pyrolysis temperature is necessary to develop biochar, another potential method, namely hydrothermal carbonization using water as a heating medium at low temperature could be implemented. Hydrochar was synthesized at 170 ℃ for 90 min. Further, urea-functionalized hydrochar was prepared at different ratios of urea to hydrochar (1:1, 2:1 and 3:1 w/w), activation temperatures (400-800 ℃) and heating rates (5-15 ℃/min). Urea-functionalized hydrochar possessed the highest adsorption capacity of 76.20 mg/g when activated at 600 ℃ for 60 min with urea to hydrochar ratio of (2:1). Here, the introduction of N-functional group from the incorporation of urea to hydrochar helps to increase the surface basicity which beneficial for CO2 adsorption. of Both modified adsorbent via metallization and urea functionalization showed consistent performance in 11 cycles of CO2 adsorption-desorption and exhibited high affinity towards CO2 compared to other gases such as nitrogen (N2), methane (CH4) and air. Several adsorption kinetic models were used to represent the experimental data which Avrami fitted the data better at any adsorption temperatures. Physisorption was chief governing mechanism of adsorption for pristine biochar, metallized-biochar and urea-functionalized hydrochar implied from their low activation energy, indicating weak interaction of adsorbent and CO2 molecules. In the next phase, the pristine biochar, metallized-biochar and urea-functionalized hydrochar were subjected to CO2 adsorption in a fixed-bed column. The effects of different total gas flowrates (30, 40, 50 and 60 ml/min), initial CO2 concentrations (5, 10, 15 %) and adsorption temperatures (30, 40, 50 and 70 ℃) on CO2 adsorption capacity were investigated. Correspondingly, the optimized process variables for pristine biochar, metallized-biochar and urea-functionalized hydrochar were at 30 ml/min of total gas flowrate, 15 % of initial CO2 concentration and 30 ℃ of adsorption temperature with maximum CO2 adsorption capacity of 165.67 mg/g, 176.24 mg/g and 195.54 mg/g, respectively. Overall, LW is a potential woody biomass in developing adsorbent to capture CO2.
Zif-l@pdms/pes supported ionic liquid membrane for co2/n2 and co2/ch4 separation
(2024-04-01)
Meor Muhammad Hafiz, Shah Buddin
Supported ionic liquid membrane (SILM) formed through the impregnation of ionic liquid (IL) in polymeric membrane structure is effective for selective separation of CO2. This study fabricated a novel SILM configuration by locating zeolitic- imidazole framework-L (ZIF-L) on the skin of a polyethersulfone (PES) hollow fiber membrane to form the composite ZIF-L@PDMS/PES membrane. Subsequently, ZIF- L@PDMS/PES SILM was derived by impregnating [BMIM][BF4] IL. Through the incorporation of ZIF-L and IL in the membrane, the gas transport properties (diffusivity and solubility) of CO2 in the membrane are expected to be enhanced. Since this study fabricates a unique configuration of SILM, the modification of the Resistance-in-Series model is necessary to accurately determine SILM performance. Considering the model's reliance on the permeability data of each composite layer, the first objective of this study focused on investigating ZIF-L@PDMS layer independently. The impact of filler shape, IL type, suitable IL impregnation method and gas transport properties of the ZIF-L@PDMS layer were investigated. The usage of 5 wt% ZIF-L and 0.2M IL enhanced the separation performance of ZIF-L@PDMS. The membrane recorded CO2 permeability, CO2/N2 selectivity and CO2/CH4 selectivity of 5017 Barrer, 36.46 and 23.22, respectively. The time lag analysis confirmed the performance of the IL-modified ZIF-L@PDMS was enhanced due to improved CO2 solubility. Furthermore, the performance data of ZIF-L@PDMS layer was found to be well-fitted by the modified Cussler model that considered aspect ratio. The subsequent phase involved optimizing the coating conditions of ZIF-L@PDMS/PES hollow fiber membranes using a Box-Behnken design (BBD). The optimized conditions (4.70 wt% PDMS, 5 mm/s withdrawal speed, 74 s holding time, and a 1.5:1 ZIF-L:PDMS ratio) were then employed to fabricate ZIF-L@PDMS/PES SILM through post-modification method. The SILM recorded 10.56 GPU of CO2 permeance for pure gas fed at 375 cmHg. Furthermore, the selectivity of CO2/N2 and CO2/CH4 is 42.97 and 21.78, respectively. The combination of the modified Cussler and Resistance-in-series models accurately determined ZIF-L@PDMS/PES SILM performance, at an average absolute relative error (AARE) of less than 5%, even during long operating hours. Minimal error was obtained via the modification of Resistance-in-Series model that considered surface porosity and pore penetration depth. For binary gas feed, the modified Resistance-in-series model was coupled with the operational model to predict ZIF-L@PDMS/PES SILM performance at various CO2 compositions and feed pressures. This approach estimated the performance of SILM at minimal AARE (<5%) for binary gas separation. At 18 mol% CO2, the membrane recorded CO2/N2 and CO2/CH4 selectivity of 28.56 and 19.30, respectively.
Innovative superhydrophobic platforms for growth enhancement in duckweed cultivation
(2024-09-01)
Chua, Mei Xia
Duckweed, a fast-growing aquatic plant with rich nutritional content, contributes significantly to various fields like animal feed and bioenergy production. However, conventional cultivation methods such as ponds and tanks, encounter challenges water loss, nutrient imbalances, and scalability, limiting biomass yield and biochemical compositions. These challenges highlighted the need for efficient and scalable cultivation systems. Hence, this study addresses these challenges by developing a versatile platform through a novel approach of employing superhydrophobic properties to duckweed cultivation system. A robust beeswax superhydrophobic coating (156.06 °) was created by optimizing wax concentration and simplifying preparation of omitting sonication and annealing. The integration of this coating into cultivation platforms increased surface area and minimized water footprint for plant growth. To evaluate the performance of the superhydrophobic platform, duckweed (Lemna minor and Spirodela polyrhiza) was cultivated and compared with conventional platform of glass jar that served as the control. The findings demonstrated that the superhydrophobic platforms significantly improved the biomass production compared to control. L. minor showed superior growth in the superhydrophobic coated acrylic platforms (SHPA), while S. polyrhiza thrived best on the variant of the acrylic platform added with metal mesh (SHPAM). This work demonstrated the effectiveness of superhydrophobic coatings in promoting duckweed cultivation. Impacts of geometrical design of cultivation platforms in terms of efficient distribution of light and nutrient to duckweed were investigated. L. minor and S. polyrhiza were grown on platforms of different geometrical designs, including geometries of rectangle (SHP-R), oval (SHP-O) and circle (SHP-C). Both species showed the best performance of growth, nutrient uptake and biochemical quality in SHP-O. Additionally, a multi-tier cultivation system incorporating superhydrophobic coatings was investigated. The system (SHP-2T) utilized two tiers to enhance space utilization and improve light and nutrient distribution. The growth performance and nutrient uptake of L. minor and S. polyrhiza cultivated in respective tiers were evaluated. Dye-tracking and CFD simulation demonstrated an even flow pattern in SHP-2T system, ensuring efficient nutrient distribution, leading to significant reductions in ammonia and phosphate in the medium for both duckweed species. Both duckweed species displayed good growth rates and biochemical quality within the SHP-2T system, with no significant differences observed between tiers, validating the system's consistency. The successful development of superhydrophobic coatings, coupled with optimized platform design, has the potential to revolutionize duckweed production and unlock its full potential for various applications.

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