Pusat Pengajian Kejuruteraan Kimia - Tesis

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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.
Adsorption of chloramphenicol and bisphenol a using cellulosic carbonaceous fibrous strand adsorbent
(2022-04-01)
Ahammad, Nur Azian
Recently, the problem of water contamination due to organic compounds residues detected in natural wastewater streams has become more alarming. These pollutants are referred to as new emerging pollutants. New emerging pollutants such as Chloramphenicol (CPC) and Bisphenol A (BPA) have been discovered in many water resources. This study aims to synthesis carbonaceous fibrous strand adsorbent (CFSA) via Schweitzer’s reagents for the adsorption of CPC and BPA from aqueous solution. CFSA had a surface area of 650.921 m2.g-1 , a total pore volume of 0.485 cm3.g-1 and an average pore diameter of 2.930 nm. Batch and continuous adsorption study were conducted for the removal of CPC and BPA. The maximum adsorption capacity, Qmax for CPA and BPA adsorption was 234.03 mg.g-1and 118.97 mg.g-1, respectively at 50 °C. For both adsorption systems, the kinetics of adsorption followed a pseudo-second-order kinetic model. The adsorption diffusion behaviour was evaluated by intraparticle diffusion. Based on the Boyd plots, the adsorption of CPC and BPA onto CFSA was mainly governed by film diffusion. Thermodynamic findings demonstrated that CPC and BPA adsorption onto CFSA were spontaneous and endothermic in nature. Next, the adsorption profile for both CPC and BPA were best fitted Freundlich isotherm models, suggesting a heterogonous adsorption surface for both systems. From the isotherm, kinetic and thermodynamic results, we can conclude that a combination of chemisorption and physisorption takes place, i.e., physicochemical adsorption is involved in adsorption of CPC and BPA. The fixed-bed adsorption profile for CPC and BPA system were fitted well to Thomas and Yoon-Nelson.
Adsorptive Cathodic Stripping Voltammertries Of Lead In Water Samples Using 2, 2'-Bipyridyl; 1,10- Phenanthroline And Nitrite Ions
(2013-02)
Jawad, Masar Hadi
A new differential pulse adsorptive cathodic stripping voltammetric (DPAdCSV) method was developed for the determination of lead concentration in aqueous solution.. This was based on complexation of lead with combination of two complexing agents viz 2,21-hipyridyl and 1,1 O-phenanthroline with nitrite at hanging mercury drop electrode (HMDE). Variables affecting the response such as pH, supporting electrolyte, initial purge time, drop size, stirring speed, deposition potential, deposition and equilibration times, sweep rate, pulse amplitude and ligand concentration were investigated. Using the first reagent 2,2'-bipyridyl with nitrite[reagent (I)] and under optimized conditions the relationship between peak current and lead concentration was linear in the range of 10-500 ng mL-l. The limit of detection was found to be 0.48 ng mL-l. The relative standard deviation (RSD) for n= 9 determinations of standard 25 ng mL-I Pb2+ was to 1.74% with linear regression coefficient (R2) 0.9991.
Agro-Based Catalyst Systems For Converting Palm Based Oils With High Fatty Acids And Water Contents Into Methyl Esters
(0008-12)
Ganesan, Shangeetha
Present work focuses on producing a dual catalyst system to esterify fatty acids and . transesterify triglycerides into methyl esters in the presence of methanol. Firstly, boiler ash sourced from waste empty fruit bunches of the palm oil industry was characterized and used as a pseudo-homogeneous base catalyst for transesterification of palm olein. Boiler ash successfully transesterified palm olein at mild reaction conditions (3 wt.% dried boiler ash, 15: 1 methanol : oil molar ratio, methanol refluxing temperature and reaction time of 0.5 b) to produce 90% methyl esters. Calcium oxide (calcined at 900 oe for 2 h) was added to boiler ash in order to increase the free fatty acids and water tolerance of boiler ash for transesterification of low quality oils. A mixture of boiler ash-calcium oxide was found to be able to tolerate 3 wt.% water and 4 wt.% free fatty acids.
Amoxicillin, chloramphenicol and oxytetracyclines antibiotics adsorption by activated carbon generated from tecoma wood waste
(2023-08-01)
Mohamad Nasran Bin Nasehir Khan
The occurrence of antibiotics in the environment has contributed to negative consequences towards human health and aquatic life. Antibiotics are very difficult to be removed from wastewater using traditional techniques due to their highly soluble nature. This study focuses on synthesizing Tecoma chip based activated carbon (TCAC) to adsorb antibiotics namely amoxicillin (AMOX), chloramphenicol (CAP) and oxytetracyclines (OXY) from aqueous solution. TCAC was prepared by physicochemical activation which includes microwave heating, carbon dioxide (CO2) gasification and potassium hydroxide (KOH) chemical treatment. Response surface methodology (RSM) was used as the optimizing tool in producing TCAC. Optimum preparation conditions were found at 657 watts for radiation power, 20 minutes for radiation time and 0.99 for impregnation ratio (IR), which resulted into 27.68% of TCAC’s yield with 84.06 %, 87.84 % and 82.71 % removal of AMOX, CAP and OXY, respectively. Optimized TCAC shows high BET surface area of 924.85 m2/g and total pore volume of 0.3854 cm3/g. In the equilibrium study, adsorption uptakes increased with adsorbates initial concentration. Isotherm study revealed that AMOX-TCAC and OXY-TCAC adsorption systems followed Langmuir model while CAP-TCAC adsorption system followed Freundlich model. Langmuir monolayer adsorption capacities, Qm of TCAC were found to be 357.14 mg/g, 434.78 mg/g and 344.83 mg/g for adsorbing AMOX, CAP and OXY, respectively. In term of kinetic study, all adsorption systems followed pseudo-second order kinetic model. Adsorption mechanism study found that the rate controlling step were film diffusion based on the Boyd plots. The thermodynamic study revealed that all adsorption systems studied were endothermic, spontaneous in nature and controlled by physisorption. In bed column studies, the adsorbates percentage removals were found to increase with bed height while decrease with adsorbate flowrate and initial concentration. The best model fitted the breakthrough curve for both AMOX-TCAC and CAP-TCAC were Yoon Nelson model while OXY-TCAC was excellent with Thomas model for these studies. TCAC was found to be suitable in removing AMOX, CAP and OXY from an aqueous solution.
Assessing putat river water quality using one dimensional river system model and total maximum daily load method
(2023-08-01)
Nurlailah Binti Abdillah
Putat River is one of Melaka River’s main tributaries and the most polluted tributary, especially for biochemical oxygen demand (BOD) and ammonia nitrogen (NH3-N). Currently, there is no comprehensive technique to monitor and assess the water quality of Putat River that considers the effects of pollutant loading within the catchment. This study identified the current status of Putat River water quality as well as the main contributors to the deterioration of water quality. This study also introduced water quality modelling and Total Maximum Daily Load (TMDL) analysis as a pollution control mechanism and water quality management of Putat River. The research methodology involved the water quality assessment based on the relationship between the river’s carrying capacity and the contribution of pollution sources through the application of a developed integrated one-dimension (1D) numerical model and TMDL analysis. As a result, the water quality of Putat River was polluted, especially in the downstream part. Through modelling, scenario 11 was selected in TMDL analysis, where the targeted BOD concentration, 3 mg/L in class IIA, was achieved through a 70-90% reduction of the main contributors of point and non-point sources of pollution. The maximum daily load and load allocation obtained from this study could be used to guide the TMDL implementation plan.
Attached benthic microalgae cultivation on flat sheet and tubular biofilm photobioreactor
(2023-04-01)
Siti Mariam Md Poad
Microalgae are currently in the spotlight due to its various potential such as feedstock food, livestock feed, fuel, fertilizers, fine chemicals and other value-added products. However, large cultivation of microalgae is not necessarily economically viable due to the high capital and operating cost. This leads to biofilm cultivation where the microalgae are grown on the surface of a porous substrate that ease the microalgae harvesting process and reduces water consumption and eventually the cost of cultivation. Thus, this study intended to study the cultivation of microalgae on the surface of the porous substrate. It comprises of four species of microalgae from benthic origin (Amphora coffeaformis, Cylindrotheca fusiformis, Navicula incerta and wild strain) and two types of flat sheet membrane as the porous substrate namely polyvinylidene fluoride (PVDF) and polyethersulfone (PES) and one tubular capillary PES membrane. Contact angle analysis revealed that PES membrane is more hydrophilic to PVDF membrane. For flat sheet membrane, the experiment was carried out on a glass plate covered with cellulose based absorbent paper in a glass chamber with medium circulation at 40.0 ml/min. Throughout 7 days of cultivation, highest areal biomass was achieved by PES membrane which at 16.26 ± 0.89 g DW/m2 for A. coffeaformis, 22.86 ± 1.05 g DW/m2 for C. fusiformis, 11.55 ± 1.95 g DW/m2 for N. incerta and 16.14 ± 2.76 g DW/m2 by wild strain. C. fusiformis achieved the highest areal biomass and biomass productivities on PES membrane compared to other species. This lead to the selection of PES material for porous substrate and C. fusiformis to be further studied on the tubular capillary porous substrate photobioreactor (PSBR). The experiments were carried out in a fabricated tubular column designed for microalgae cultivation with 0.5 ml/min medium circulation. The tubular capillary PSBR system C. fusiformis achieved areal biomass of 5.30 ± 0.34 g DW/m2 and is able to approach the biomass productivity of the conventional suspension culture.
Bioregenera Tion Of Granular Activated Carbon Loaded With Phenol And Ocresol By Immobilized Biomass: Quantification And Kinetic Studies
(2013-11)
Toh, Run Hong
The objectives of this study were to (i) develop a novel approach to bioregenerate GAC loaded with phenol and a-cresol, respectively, using immobilized biomass as well as immobilized PAC-biomass, (ii) quantify and compare the bioregeneration efficiencies of GAC loaded with phenol and a-cresol, respectively using suspended and immobilized biomasses as well as immobilized PAC-biomass, and (iii) develop kinetic models to describe the bioregeneration process of GAC loaded with phenol and a-cresol, respectively, using the immobilized biomass.
Biotransformation Of Ferulic Acid Extracted From Biomass To Biovanillin By Amycolatopsis Sp. Atcc 39116
(2014-11)
Abu Sepian, Noor Raihana
This study focuses on the biotransformation of synthetic and extracted ferulic acid (FA) from lignocellulosic biomass using growing cells of Amyco/alopsis sp. ATCC 39116 as a biocatalyst. Preliminary alkaline hydrolysis showed that the hydrolyzate from oil palm empty fruit bunch (OPEFB) contained the highest amount of FA (199.4 mg/l) among the other three lignocellulosic wastes (i.e. oil palm frond, coconut fiber and sheIl). Optimization of extraction was carried out using Response Surface Methodology (RSM) via Central Composite Design (CCD) on the effect of three independent variables, i.e. concentration of NaOH (1.5-5 M), solid/liquid ratio (0.03-0.084 g/ml) and time (16-32 h). The optimum FA concentration of 2.04 mg/g OPEFB (365.19 mg/l) was obtained under the optimal conditions of 1.5 M ofNaOH concentration, 0.03 g/ml of solid/liquid ratio and 32 h of extraction time. The extracted FA was further purified using polyvinylpolypyrrolidone (PVPP) and activated carbon, and about 97.26% was successfully recovered from the extract using PVPP. The partially purified FA was converted into 38.47% molar yield of vanillin, showing the ability of Amyco/alopsis sp. ATCC 39116 to convert the extracted FA from lignocellulosic waste.
Carbon dioxide capture using hydrophobic-modified surfacetemplated polyvinylidene fluoride membrane via membrane contactor
(2024-08-01)
Chang, Pei Thing
Membrane gas absorption (MGA) emerges as a potential technology for separating CO2 from flue gas, offering significant advantages over conventional CO2 removal methods. In MGA, the porous membrane physically separates the gas and liquid phases. The gas separation role is fulfilled by the absorbent which attracts the CO2. However, MGA efficiency is often constraint by membrane wetting issues and low CO2 permeability. To address these challenges, it is hypothesized that synthesizing PVDF membrane with opposing surface wettability can enhance wetting resistance, especially for long-term process and simultaneously improving CO2 capture efficiency in MGA. In this work, two PVDF membranes were synthesized from polymers with different molecular weight (350 kDa and 300-320 kDa). PVDF membrane fabricated with high molecular weight PVDF powder (HMW/g-PVDF) exhibited critical wetting issues due to the presence of a more polar -polymorph on the membrane surface, which has a higher affinity for water. It led to a low water contact angle (WCA) of 92°. To overcome this, high molecular weight PVDF powder was used to fabricate superhydrophobic membrane via a non-solvent induced phase inversion method with non-woven substrate. Membranes produced with water (tPVDF-DI) and ethanol (tPVDF-E) coagulation bath displayed micro- and nano-level hierarchical structures on the membrane surface. The change in the surface structure exhibited high WCA of 153.6° and 155.1° and low contact angle hysteresis (CAH) of 15° and 11.8°, respectively. The patterned membrane showed a higher CO2 absorption flux at 7.00 x 10-2 mol/m2 s, which was nearly 10 times higher than the non-printed membrane. The flux remained unchanged even after 20 days of contact with amine absorbent, as the trapped air within printed structures on the membrane surface inhibited amine penetration into the membrane pores. To further enhance CO2 capture efficiency, the opposite side of the patterned surface was modified with ethylenediamine (EDA) and graphene oxide (GO) to construct a CO2-philic surface. Compared to membrane without a CO2-philic surface (tPVDF-DI) in mixed gas MGA process, the tPVDF/EDA5/GO membrane showed better MGA performance, with a CO2 absorption flux of 4.010-3 mol/m2 s and a gas selectivity of 6.0. The presence of amine and rich oxygen-containing functional groups on the membrane surface attracted more CO2 molecules to flow across the membrane to be absorbed by the amine absorbent. Overall, the combination of a printed hierarchical structure membrane surface with a CO2-philic surface represents a significant innovation that effectively prevents membrane wetting and enhances CO2 passage through the membrane in the MGA process.
Carbon dioxide reduction with methane over cerium oxide and indium oxide nanocomposite photocatalysts
(2023-01-01)
Tharani Kulandaivalu
Photocatalytic carbon dioxide (CO2) reduction with methane (CH4) offers a great potential to convert two notorious greenhouse gases to value-added fuels using inexhaustible solar energy. The present study aimed to develop novel silver (Ag) and ceria (CeO2) modified indium oxide (In2O3) photocatalysts for photocatalytic CO2 reduction with CH4 to convert highly stable CO2 and CH4 into syngas. At first, a comparison study was conducted for CeO2/In2O3 composite photocatalysts that were synthesised using two different facile methods, namely wet-impregnation (WI) and hydrothermal co-precipitation (CP) methods and the as-synthesised composite were denoted as CeO2/In2O3-WI and CeO2/In2O3-CP, respectively.The morphological observation verified the formation of interfaces between CeO2 and In2O3 in both the CeO2/In2O3 samples. Both preparation methods resulted in the formation of Ce3+ entities as predominant species on the surface of CeO2/In2O3. The presence of higher content of Ce3+ reflected a strong interfacial contact between CeO2 and In2O3 indicating the formation of heterojunction. However, CeO2/In2O3-WI produced excess portion of Ce3+ species and oxygen vacancies that became recombination centers. The photocatalytic CO2 reduction with CH4 results revealed that the reaction over CeO2/In2O3-CP formed a total yield of 174 μmol/gcat CO and H2 and was 1.5 and 3.6 times higher than that of CeO2/In2O3-WI. However, the selectivity of CO over CeO2/In2O3-WI was higher than that of CeO2/In2O3-CP, with a selectivity of 94 and 85% respectively. When H2O was used as reductant to substitute CH4, the selectivity of H2 was gradually suppressed from 26 % to 9 and 4 % over 0.2 CeO2/In2O3-WI and 0.2 CeO2/In2O3-CP respectively. Based on the experiment findings, the superior photoactivity of CeO2/In2O3-CP was ascribed to its smaller and uniform particle size distribution, higher surface area, enhanced light absorption capacity and suppressed recombination of electron-hole pairs as compared to CeO2/In2O3-WI. Following that, a non-precious Ag metal was photodeposited over CeO2/In2O3-CP to construct Ag-CeO2/In2O3 ternary photocatalysts for photocatalytic CO2 reduction with CH4. At an optimum loading of 0.5 wt. %, the formation of CO and H2 was improved remarkably with a total yield of 253 μmol/gcat which is about ~0.5 times higher than that of binary CeO2/In2O3. A mechanism of reaction was developed based on Type II heterojunction for Ag-CeO2/In2O3 photocatalyst in which charges travel in the direction of In2O3→CeO2→Ag where Ag acts as an electron sink to effectively trap electrons from CeO2, reducing their recombination. Among the operating parameters studied, feed ratio was the most influential to drastically affect the product yield. The stability test showed prolonged stability and reusability of Ag-CeO2/In2O3 in five cycles of photoreaction. The Langmuir–Hinshelwood model revealed that yield rates of products were dependent on efficient adsorption of the reactants and desorption of products over the photocatalyst surface. In conclusion, this study proved the conversion of CO2 and CH4 to syngas using photon energy over the novel highly efficient Ag-CeO2/In2O3 photocatalysts.
Catalytic co-pyrolysis of high-density polyethylene/polypropylene mixture and oil palm fibre to liquid fuel
(2022-09-01)
Abel Williams Gin
Green House Gas (GHG) emission and environmental pollution remain the two main issues of concern in the globe today because of the continuous and unrestricted dumping of both plastic and agricultural biomass residues across the globe. Hence, a conversion of these solid wastes into highly valuable liquid fuel could be a potential solution to alleviate this environmental issue. In this work, oil palm fibre (OPF), a major agricultural biomass in Malaysia, was mixed with an equal mass of high-density-polyethylene (HDPE) and polypropylene (PP) and converted to liquid fuel via non-catalytic and catalytic co-pyrolysis in a fixed-bed-reactor. The synthesized catalysts, SBA-15 exhibited a highly ordered mesoporous structure while ladle furnace derived - hydroxyapatite (HAP-LF) demonstrated metal-rich microporous structure, respectively. The influence of process parameters (temperature, feedstock ratio, catalyst/feedstock ratio) indicated that the maximum composition of the desirable compounds (alcohol and hydrocarbons) using HAP-LF was 71.65 % (Temperature = 450 oC, OPF-plastic mixture ratio = 1:3). The yield of these compounds was higher than maximum value of 60.54 % obtained using SBA 15 (600 oC, OPF-plastic mixture ratio = 1:1). The HAP-LF catalyst/feedstock ratio of 1:8 produced the maximum composition of the desired compounds in oil while SBA 15 catalyst/feedstock ratio of 1:6 produced maximum composition of the desired compounds. These results indicated that HAP-LF is a more suitable catalyst for the catalytic co-pyrolysis of the feedstock mixture. The heating value of the produced oil was found to be 44.5 kJ/mol. Recyclability studies of the HAP-LF catalyst indicated that it could be used up four consecutive recycle times without serious deactivation. The kinetic studies using thermogravimetric analyzer showed a reduction in activation energy from 13.98 - 92.11kJ/mol to 21.58 - 59.33 kJ/mol across the three degradation stages of the feedstock mixture.
Catalytic cracking of waste cooking oil using activated carbon based supported trimetal oxides catalyst
(2024-12-01)
Muhammad Shafizruddin Firdaus, Fazli Ku
Compared to ZSM-5 and Al2O3, which are commonly used in the catalytic cracking of waste cooking oil (WCO), activated carbon showed higher liquid yield with more C9–C27 hydrocarbons. Due to bamboo possessing a higher surface area and porosity than wood-based activated carbon and charcoal, it performs better in catalytic cracking. Catalytic activity of activated carbon supported transition metal oxides (NiO, Fe3O4, CuO, CoO2, Al2O3 and ZnO) in catalytic cracking of WCO were studied in a batch reactor. The yield of the liquid product increased with the incorporation of metal oxides. AC supported Ni, Fe, and Zn oxides shown high selectivity towards C15 and C17 hydrocarbons in comparison to other catalysts in the study. The catalytic performance was compared with activated carbon supported bimetal oxide and trimetal oxide catalysts to examine their synergistic interaction. Trimetallic oxide catalyst often exhibit higher catalytic activity compared to monometallic and bimetallic oxide catalyst due to the synergistic effects between the different metals that could enhance the catalytic cracking. NiO-Fe3O4-ZnO/AC has a BET surface area of 835.85 m2/g with the strongest acidic sites of 20114 μmol/g. The catalytic activities also were studied in the temperature range of 340-400 °C, 30 – 120 minutes reaction and 1.0-6.0 g catalyst loading for the operating parameters study. The liquid product yield further improved to 93.17 wt% with 62.60% hydrocarbons yield and 94 vol% liquid product temperature range via NiO-Fe3O4-ZnO/AC at 400 °C, 1 hour reaction and 3.6 g catalyst loading. The influence of reaction temperature, reaction time and catalyst loading on its catalytic activity were tested. The catalysts can be used up to 5 cycles in the catalyst reusability test.
Catalytic cracking of waste cooking oil using sulfonated activated carbon supported la/ce bimetallic catalysts for biofuel production
(2023-08-01)
Samah Zaki Naji
The biofuel industry is poised for exponential growth due to increasing global fuel demand, environmental regulations, and energy security concerns. The aim of this study was to assess the performance of different catalysts based on modified activated carbon in the catalytic cracking of waste cooking oil (WCO) into alkane-based hydrocarbons. The catalysts were prepared by subjecting the coconut-shell activated carbon (AC) to acidification using varying concentrations of sulfuric acid to increase surface acidity and subsequent incorporation with lanthanum (La) and cerium (Ce) metals enhancing both physical and chemical properties. The objective was to determine the most effective catalyst formulation that would yield the highest amount of alkane-based hydrocarbons. The catalytic cracking activity was evaluated in a fixed bed reactor under N2 flow at 450 °C and a weight hourly space velocity (WHSV) of 8 hr-1 with 60 min collection time. The physical and chemical properties of the prepared catalysts were characterized using a range of techniques, including BET, SEM-EDX, XRD, TPD-NH3/CO2, FTIR, and TGA. The synthesized catalysts were tested in terms of organic liquid yield (OLP), coke, gas, hydrocarbon yields, and n(C15+C17) selectivity along with alkane yield. Response surface methodology (RSM) was applied to determine the optimal La and Ce loading concentrations for maximizing OLP and hydrocarbon yields. La and Ce metal loading were tested in the range of 0 to 5 wt.% and 0 to 10 wt.%, respectively, on sulfonated activated carbon using central composite design (CCD). The results showed that the optimum metal loading concentrations were 5 wt.% of La and 5 wt.% of Ce over sulfonated AC. Overall, the optimum catalyst (5La-5Ce/SAC) achieved an OLP yield of 83.91% comprising 97.77% hydrocarbons that were mostly alkane (82.04%) and n-(C15+C17) selectivity (57%). the effect of operating conditions was examined in terms of catalyst performance. These include reaction temperature (390 ̊C to 510 ̊C), WHSV (4 hr-1 to 12 hr-1), and reaction time (60 min to 240 min). The optimum operating conditions were identified as 450 ̊C reaction temperature, 8 hr-1 WHSV, and 60 min reaction time. The recyclability of 5La-5Ce/SAC was then being carried out at optimum operating conditions. 5La-5Ce/SAC showed significant catalytic cracking with high activity for the first recycled run but decrease after the second recycled run due to coke formation that deposits on the catalyst's surface. Besides, the mechanism of palmitic and oleic acids during catalytic cracking over 5La-5Ce/SAC was also studied using model systems. The major reaction pathway of both acids over 5La-5Ce/SAC catalyst was found to be decarbonylation reaction. The kinetics of catalytic cracking of palmitic and oleic acids have been studied over a temperature range of 350°C to 450 °C using 5La-5Ce/SAC catalyst and WHSV of 6hr-1 to 10hr-1. The reaction activation energies of palmitic and oleic acid were found to be 45.47 kJ/mole and 19.50 kJ/mole respectively.
Catalytic hydrogenolysis of lignin into aromatic compounds over mesoporous ni-based bimetallic catalysts in the presence of hydrogen donor solvent
(2024-05-01)
Ewuzie Nnadozie Remigius
Lignin, a renewable biopolymer is the most common source of aromatics and carbon on the Earth. Valorization of lignin into aromatic compounds has received limited attention due to its intricate structure. Lignin hydrogenolysis holds huge potential to produce aromatic compounds. This study focused on the development of promoted Ni-based bimetallic catalysts, specifically Ni-Co/C, and Ni-Cu/C, on activated carbon support. Also, Ni-Co/HZSM-5 and Ni-Cu/HZSM-5 on zeolite support. And to evaluate their performance on lignin hydrogenolysis reaction in an 80 mL stainless-steel batch reactor under internal hydrogen donor solvents (isopropanol and methanol), and to compare their performance with their corresponding monometallic catalysts. Their promotional effect on lignin hydrogenolysis was evaluated. The catalysts were synthesized by the incipient wetness impregnation method. BET, SEM, EDX, and XPS measurements revealed their physicochemical properties and promotional effects. This promotional effect led to improved hydrogen transformation ability and enhanced hydrogenolysis activity, resulting in high lignin conversion and yield of monomeric products. Effects of reaction parameters such as temperature (220-260 ℃), pressure (2-5 MPa), time (2-5 h), stirring speed (500-800 rpm), and catalyst dosage (0.05 to 0.3 g) on lignin hydrogenolysis were elucidated. Catalyst reusability and high heating values were also investigated, and the kinetic parameters were elucidated. The addition of cobalt and copper to nickel as promoters enhanced the lignin conversion and monomeric product yield because they providedmore active sites for catalyst-lignin interaction. Activated carbon support demonstrated better dispersion and stability of the active components compared to zeolite support due to its larger surface area of 537.6 m2/g. 20%Ni-10%Co/C bimetallic catalysts achieved the highest lignin conversion and yield of monomer products of 94.2% and 53.1 wt.%, while Ni-Co/HZSM-5 bimetallic catalysts achieved 91.2% lignin conversion and 44.9 wt.% yield of monomer products in isopropanol solvent. Similarly, Ni-Cu/HZSM-5 bimetallic catalysts achieved a remarkable lignin conversion of 90.6% and a significant monomer product yield of 40.8 wt.% in methanol solvent. Meanwhile, Ni-Cu/C bimetallic catalysts achieved 84.7 % lignin conversion affording 33.0 wt.% monomer product in isopropanol solvent under optimal reaction conditions at 250 ℃, 4 MPa, 4 h, 700 rpm, and 0.3 g. GC-MS, GC-FID, FT-IR, GPC, and elemental analysis were employed to investigate the volatile and non-volatile products. The effective depolymerization of alkali lignin was revealed by GPC analysis. A total of 20 aromatic compounds were successfully identified by the GC-MS analysis. Based on the excellent results obtained, possible reaction mechanisms were proposed to elucidate the catalytic pathways involved. The results demonstrated that Ni-based bimetallic catalysts exhibited superior catalytic performance, enhanced stability, and product selectivity than their corresponding monometallic catalysts.
Chemically modified graphene as nano-adsorbent for environmental application
(2023-01-01)
Rabita Bt. Mohd Firdaus Achutan
Carbon dioxide (CO2) emissions and pollution by dyes have a significant environmental impact, and it is imperative that cost-effective and recyclable adsorbents are developed to reduce their effect on the ecosystem and human health. Research was conducted to develop porous graphene-based macrostructures for two different environmental applications including adsorption of CO2 gas and Congo red dye respectively. The first part of this research is focused on developing 2D graphene oxide (GO) and further modifications on GO were carried out with two different approaches: physical and chemical activation. The structural and the chemical properties of the prepared activated graphene were deeply characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometry (XPS) and Brunauer–Emmett–Teller (BET) nitrogen adsorption. The temperature used for the activation process was found to be the key parameter leading to enhance CO2 adsorption capacity of the GO-based materials. The specific surface area was increased from 219.3 m2 g−1 for starting GO to 762.5 m2 g−1 and 1060.5 m2 g−1 after physical and chemical activation, respectively. The performance of CO2 adsorption was gradually enhanced with the activation temperature for both approaches. For the best performances, a factor of enhancement of 6.5 and 9 after physical and chemical activation, respectively was reached. The CO2 adsorption capacities for physically and chemically activated graphene were 27.2 mg g−1 and 38.9 mg g−1, respectively, at 25 °C and 1 bar. In addition, the impact of the used temperature for the activation treatment on the CO2 adsorption capacity has been investigated and discussed leading to a comprehensible mechanism. The second phase of this study was to construct 3D graphene based monoliths (GBMs) by self-assembling of GO in which GO was reduced by hydrothermal method using ascorbic acid, as the reductant agent. Different concentrations of GO (1-6 mg mL-1) in the starting stable aqueous dispersion obtained at pH 10 were investigated to optimize the self-assembly process. The structural properties including surface area, pore volume, pore size and surface chemistry were measured and discussed considering their performance for CO2 capture. The results showed that the optimized adsorbents (2 mg mL-1) exhibited the highest surface area and total pore volume of 331 m2 g-1 and 0.80 cm3 g-1 respectively. In the developed 3D GBMs, the best CO2 adsorption capacity (74.0 mg g-1) was measured at a GO concentration of 2 mg mL-1, nearly twice than that measured for activated 2D graphene. In the second part, a thin layer of alumina was deposited on the optimized 3D GBMs to prepare a 3D Al2O3 / GBM hybrids. In order to deposit alumina homogeneously on the inner walls of the porous structures, atomic layer deposition (ALD) technique was selected since its principle involves the use of gaseous precursors that facilitate their diffusion. Furthermore, alumina is shown to be deposited at the core of 3D GBMs using advanced and powerful characterisation techniques such as focused ion beam technology (FIB), transmission electron microscopy (TEM), scanning transmission electron microscope (STEM) and electron energy loss spectroscopy (EELS) mapping. This is an unprecedently detailed study of 3D Al2O3 / GBM hybrids, which has not previously been reported. The growth mechanism of alumina on the graphene surface was as well investigated. In contrast to the most approaches which require additives (surfactants or polymers) to enhance graphene reactivity for ALD deposition, reduced GO forming porous aerogel that offers sufficient seeding sites for alumina formation. The proposed growth mechanism comprises a nucleation stage that results in the formation of primarily islands and leading for the highest ALD duration to a continuous covering layer for high ALD cycles. The 3D Al2O3 / GBM hybrids were initially used for CO2 adsorption studies, however, the adsorption capacity gained was reduced from 74.0 mg g-1 to 25.95 mg g-1 compared to the 3D GBMs. Thus, in this section, the prepared 3D Al2O3 / GBM was used for another environment application which is dye adsorption study. The adsorption capacity of Congo red (CR) of the 3D Al2O3 / GBM is much higher than that of pristine / uncovered 3D GBMs. The dominant mechanism in the adsorption process of CR dye by the designed 3D Al2O3 / GBM is based on favourable electrostatic interactions between alumina surface and CR. This work is therefore proof-of-concept research in which the 3D Al2O3 / GBM hybrids was employed as a superior key component in the construction novel materials for adsorption system with promising adsorption performance toward dye pollutants
Conversion of waste slags into functional oxide materials and their application in carbon dioxide capture
(2023-02-01)
Zaza Hazrina Hashim
Slag is a by-product of the smelting process for ores and scrap metals. The issue of excessive slag waste generated in the iron and steel industries has spurred an investigation on slag utilization. Blast furnace slag (BFS) is recovered by melting and separation from blast furnaces that produce molten pig iron, while dephosphorization slag and desiliconization slag are generated during the purification of steel to reduce the phosphorus and silicon content, respectively, and mostly consist of CaO, FeO, SiO2 and other minor oxides. In addition, CO2 emitted from the iron and steel industry accounts for about 5-7% of the total CO2 emissions worldwide, and its separation and recovery is a challenge. Chapter 1 provides background information on global warming and CO2 emissions from the iron and steel industries, as well as carbon capture and sequestration using calcium looping technologies. The problem statement, research objectives, scope of the study, and contents of the thesis are also addressed. Chapter 2 summarizes the iron and steel making process and discusses global steel slag production, chemical composition of steel slag, and CO2 emissions from the steel industry. Carbon capture and sequestration using calcium looping technology, examples of the use of waste slags as CO2 adsorbents and some methods to control sintering of CaO-based adsorbents are also addressed. In chapter 3, the general methodology for converting waste slags into metal oxide composites is addressed, which includes i) synthesis of CaO-Ca12Al14O33 composite adsorbent from blast furnace slag, ii) synthesis of CaO-Fe2O3-SiO2 composite adsorbent from dephosphorization slag, and iii) synthesis of CaO-mesoporous silica composite adsorbent from desiliconization slag. It also describes the chemicals and materials, the methods used to evaluate the CO2 adsorption performance, and the details of the equipment used in the experiments. Chapter 4 describes the structure and CO2 adsorption performance of the CaO-based oxide composites synthesized from three types of slag (blast furnace slag, dephosphorization slag, and desiliconization slag) using various acids (HCl, HNO3, formic acid, acetic acid, and citric acid). In Part I, a CaO-Ca12Al14O33 composite is synthesized from blast furnace slag using HCl and HNO3 as dissolving acids. It is found that the sample synthesized using HNO3 shows a superior CO2 adsorption performance compared to that synthesized using HCl due to easy removal of nitrate ions by a thermal treatment. In Part II, a CaO-Fe2O3-SiO2 composite is synthesized from dephosphorization slag using three kinds of acids (formic acid, HCl and HNO3) and a pore-forming agent (P123). The composite synthesized with formic acid shows the highest CO2 adsorption of 17 wt% under a flow of 10% CO2/N2 and at 700 °C. It is found that the use of organic acids and the addition of a pore-forming agent are effective for the synthesis of an efficient CO2 adsorbent. In Part III, a CaO-mesoporous silica composites are synthesized from desiliconization slag using three types of organic acids (formic acid, acetic acid, and citric acid). The sample synthesized with acetic acid shows a high CO2 adsorption uptake of about 21 wt% and reusability. It is considered that the use of acetic acid promotes the separation of crystalline CaO and SiO2 particles by the reaction of acetate ions and leached Ca2+ ions to form calcium acetate, which suppresses the sintering during CO2 adsorption and improves the durability of the adsorbent
Copper-Tannate Complexes As Antifoulant In Antifouling Paint For Fish-Cage Nets
(2014-05)
Usol Ghafli, Nurul Azwin
Tannin extracted from mangrove bark, Rhizophora apiculata (R. apiculata) was used as a natural-origin source to be complexed with copper(U) salt. The copper-tannate (Cu-T) produced was used as an antifoulant in antifouling paint. Mangrove bark was extracted using 70% (v/v) aqueous acetone and gives 31.1 % extraction yield. The total phenolic content (TPC) of mangrove tannin extract (MT) was 186.0 mg gallic acid equivalent per gram sample, total flavonoid content (TFC) was 96.0 mg catechin equivalent per gram sample and condensed tannin content (CTC) was 95.5% weight content. The optimum condition of copper-tannate complexes (Cu-T) was studied using precipitation curve on varies parameters which were copper dosage, reaction temperature, reaction time and pH of Cu-T solution. The optimum conditions were taking into account of Cu-T percentage yield and IR spectrum analysis. Three derivatives ofCu-T at different pH, which were Cu-T pH 3.5, Cu-T pH 5.0 and Cu-T pH 8.0, were chosen for further analysis. The concentration of copper element in CuT and commercialized antifoulant, Cu-Oma was measured using AAS analysis and shown that Cu-T complexes had lower amount of copper content which are almost 50% lower than Cu-Oma.
Corrosion inhibition and adsorption mechanism studies of dillenia suffruticosa leaves extract as a green corrosion inhibitor for aluminium in acidic solution
(2023-01-01)
Nur Allia Binti Asri
The use of corrosion inhibitors for aluminium in an acidic medium proved to reduce the corrosion effect of an aggressive environment on aluminium and its alloys. However, the toxicity and health hazards posed by the commercial inhibitors have drawn the attention of the researchers to find alternative greener and safer corrosion inhibitors. Therefore, this work aims to study the performance of the Dillenia suffruticosa leaves extract in hindering the corrosion effect of 1.0 M HCl solution on aluminium. The extraction of D. suffruticosa leaves was done using the Soxhlet extraction technique with ethanol as the extracting solvent. The characterization of the leaves extract by Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry analyses confirmed the presence of bioactive compounds with nitrogen and oxygen heteroatoms in the functional groups. The D. suffruticosa leaves extract possessed high total phenolic content (221.56 mg GAE/g extracts and antioxidant activity with IC50 of 154.97 μg/mL. The maximum inhibition efficiency (% IE) of D. suffruticosa leaves extract obtained from weight loss measurement was 80.79 ± 2.54% when the extract concentration of 0.8 g/L at 30 °C in 2 hours of immersion time was used. The optimization of the process parameters for corrosion inhibition of D. suffruticosa leaves extract was conducted using Response Surface Methodology via Central Composite design. The maximum predicted inhibition efficiency of 76.94 % with a predicted corrosion rate of 67.52 mm/year was achieved under the optimum extract concentration of 0.8 g/L, immersion time of 2 hours at a temperature of 30 °C. The electrochemical measurement of D. suffruticosa leaves extract as corrosion inhibitor for aluminium in 1.0 M HCl was conducted under optimized conditions. In the open circuit potential (OCP) measurement, the OCP value of aluminium in 1.0 M HCl solution with the addition of D. suffruticosa leaves extract (-0.763 V) was more positive compared to aluminium in blank HCl (-0.788 V). The galvanic current density of aluminium in the inhibited solution (0.0167 μA/cm-2) was also lower than the aluminium in the blank HCl solution (0.0239 μA/cm-2). In potentiodynamic polarization measurement, the corrosion current density (Icorr) of aluminium was reduced from 5214.7 μA/cm-2 to 220.04 μA/cm-2 in the inhibited HCl with an inhibition efficiency of 95.78%. The addition of potassium iodide (KI) to the inhibited HCl solution improved the %IE of D. suffruticosa leaves extract from 80.79 % to 92.74% with 10 mM of KI. The corrosion inhibition performance by the extract obeyed the Langmuir adsorption isotherm model as indicated by the monolayer adsorption of the leaves extract on the aluminium surface. The findings from this study have proven the ability of D. suffruticosa leaves extract to inhibit corrosion of aluminium in HCl solution.
Data driven technique for boiler water quality monitoring in palm oil mills
(2022-07-01)
Rusdi, Muhammad Rufaizal Izham
Steam boilers widely used in oil palm mills are intended to generate steam in the factory for process use. Based on the statistical data from DOSH Perak Section Analysis and Process, repair work for boilers in Perak for Palm Oil showed that the number of cases increased between 2014 and 2018. The increasing of repaired cases reported to DOSH need to be studied to help facilitate the operator and in the future as the lesson learn to avoid unscheduled shutdown due to increasing numbers of repaired jobs for boilers failure. In this work, the data was collected from 39 palm oil mills from the year 2017 to 2019. Data driven analysis methods of the data collected were carried out for the parameter namely total hardness, pH, total dissolved solid (TDS), total Iron, hydrate alkalinity, silica, sulphite, phosphate, chloride and cycle of concentration. A centralised data-driven technique for boiler water monitoring systems using statistical process control (SPC) was developed in this study. The application of toolboxes like box plots and correlation coefficients adequate in providing profiles and analysis for all parameters and the correlations between the parameters. From the results of the analysis, 6 parameters that being investigate which are hardness, pH, chloride, silica, total iron and sulfite are not within the recommended ASME guidelines. Total Dissolved Solid (TDS), silica, hardness, and total iron are four factors that have a significant impact on the treatment of boiler water. Therefore, proper monitoring and treatment of boiler feedwater based on ASME guidelines and performing blowdown based on the cycle of concentration for boiler water effectively protect from scaling and corrosion of boiler. As a conclusion, the finding from this study can be introduced to DOSH and it can facilitate DOSH in improving the enforcement of boiler operators to properly monitor and control parameters according to the ASME guidelines in reducing the number of boiler repair jobs, enhance and prolong the life of the boiler.

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