Pusat Pengajian Kejuruteraan Kimia - Monograf

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Effect of membrane selectivity and configuration on purity and recovery of hydrogen from syngas
(2021-01-01)
Thamudoran, Mohashiniee
In this thesis, simulation of a membrane gas separation system for purification of hydrogen from syngas has been discussed. The simulation was done to study the effects of membrane selectivity, flow configuration, stage cut and feed pressure on the purity and recovery of hydrogen from syngas. In order to model the membrane, a complete mixing model was applied to study these effects. The mathematical modelling involved in the simulation was done in Mathcad and the results were analysed using the analysis of variance (ANOVA) under the Response Surface Methodology (RSM) method. In order to produce high purity hydrogen that is accepted as commercial industrial grade hydrogen, we studied two types of flow configuration models. Configuration 1 involves a carbon dioxide permeable membrane while configuration 2 model involves a hydrogen permeable membrane. As a result, it is noticed that in the first configuration, at the stage cut of 0.2, feed pressure of 5 bar and CO2/H2 selectivity of 1500, the highest purity of hydrogen at 52.24% and recovery of 59.58% at the permeate stream is achieved. Meanwhile in the retentate stream, the purity and recovery of carbon dioxide achieved is 52.21% and 55.53% respectively. The second configuration is when a hydrogen permeable membrane is applied. This configuration results in the highest possible purity of hydrogen of 100% with recovery of 32.52% and carbon dioxide purity and recovery at 27.35% and 90.42% respectively, at stage cut of 0.2, feed pressure of 25 bar and H2/CO2 selectivity of 500.
Conentrating of phosphate with simultaneous removal of sodium chloride via nanofiltration
(2021-01-01)
Vengedesweren, Durgashene
Recovery of phosphorus has been gaining importance due to its natural scarcity and high economical value. Aquaculture and poultry effluent with significant phosphate content required further treatment before discharging to the environment. However, its trace quantity makes the whole process not feasible. Moreover, the presence of salt (NaCl) makes the effort to recover the phosphate as fertilizer less attractive due to its unwanted salinity. In this study. nanofiltration had been tested to recover/concentrate the phosphate ions and at the same time removing the sodium chloride. The study was conducted using Desal DK5 membrane in dead-end mode using Dead End Stirred Cell at different pressures and concentration to investigate the effect of transmembrane pressure (TMP) and feed concentration on the rejection of phosphate ions, average permeate flux and concentrating factor. The highest phosphate ion rejection, 99.86%, was achieved at the lowest pressure, 2 bar, and lowest concentration of potassium dihydrogen phosphate solution (20 ppm). However, in the same parameter, the permeate flux and the concentrating factor (CF) obtained were the lowest compared to other sets of experiment which are 20.15 L/m2 .h and 1.55 respectively. The maximum CF of could be achieved at 6 bar. The removal of NaCl increases with pressure, however the presence of NaCl further reduce the phosphate ion rejection, lowering the average permeate flux and concentrating factor. The results obtained is very promising in terms of harvesting the nutrient from aquaculture effluent and at the same time removing the unwanted salinity.
Modelling of gas diffusion in mesoporous tin dioxide (sno2) as gas sensor in detecting acetone vapour
(2021-01-01)
Mohan, Khamini
Mesoporous semiconductor based gas sensors have been extensively researched and employed in the detection of traces poisonous and flammable gases such as nitrogen dioxide (NO2), carbon monoxide (CO), sulphur dioxide (SO2) and volatile organic compounds (VOCs) such as ethanol, methanol and acetone which are dangerous to both people and the environment. In this research, mesoporous tin dioxide based gas sensor, SnO2 is utilized due to its low cost, high sensitivity and quick response. In order to determine the most effective techniques for optimising the gas sensing properties of mesoporous SnO2, the effect of acetone concentration and operating temperature on the sensitivity of a gas sensor was investigated using a diffusion mechanism model. The gas detecting mechanism was controlled by Knudsen diffusion of the target gas through the porous film and its interaction with adsorbed oxygen, which followed a first-order reaction kinetic. In the diffusion mechanism model equation, a general expression of sensitivity, S (Ra/Rg) as a function of pre-exponential constants, α0 and k0, reaction activation energy for gas dependent, Ea, universal gas constant, R, temperature, T, concentration, 𝐶𝐴𝑠, film thickness, L, reaction activation energy for temperature dependent, Ek, pore radius, r and molecular weight of target gas, M was derived under steady state condition. Theoretically, the variations of sensitivity with the sensor operating temperature resulted in a bell-shaped curve with optimum temperature, whereas increasing gas concentration resulted in increased sensitivity before saturation was attained. When comparing the previous result with the MATLAB simulation, it is clear that the sensitivity increases as the temperature rises, resulting in a linear line rather than a bell shape curve. This can be said the developed model is not suited for the stimulated various operating temperature. The model was used to do a sensitivity analysis based on film thickness, L, and pore radius, r. According to simulation results, sensitivity improved with decreasing layer thickness at 300oC because of greater interaction between the gas to be detected and the sensor surface. The sensitivity of the gas sensor increased with increasing pore radius in the model at a given temperature of 300 oC, which can be explained adequately by the equation of Knudsen diffusion coefficient, Dk.
Modelling of reactive distillation for the production of methyl tert-butyl ether (mtbe) parametric sensitivity study on kinetic model
(2021-05-01)
Mohamed Zubir, Mohamed Fahim
Modelling of reactive distillation for the production of MTBE has been presented in this thesis. A reactive distillation column modelled by using RADFRAC module in the Aspen Plus V10 software for the production of MTBE. The simulation was done on an equilibrium basis. Prior to running the simulation, all the necessary data were collected. The kinetic data which is the coefficients of the equilibrium equation were collected from the equilibrium equation. The values obtained were 357.094, -1492.77, -77.4002 and 0.507563.These values were entered into the Aspen Plus V10 built-in Keq expression. The simulated model was verified by comparing to the published data. Once it was verified, the simulation was then used to carry out parametric sensitivity study on kinetic model. The effect of changes in the kinetic data and four different operating conditions of choice such as the feed flowrate of methanol, the feed flowrate of mixed butenes, the reflux ratio and the composition of isobutylene on the simulation results in terms of MTBE purity and isobutylene conversion were studied in detail. The individual best values for each operating conditions were determined. Then optimization carried out. The optimized values were 209.3 mol/s for methanol feed flowrate, 583.2 mol/s for mixed butenes feed flowrate, 7 for reflux ratio and 0.357 for isobutylene mole fraction. From these set of values, a MTBE purity and isobutylene conversion of 100.00 % obtained successfully. This study shows that the changes in parameters influences the performance of reactive distillation process for the production of MTBE.
Optimization and thermal degradation kinetics of cellulose nanoparticles (cnps) production from coconut fiber
(2021-06-01)
Tim, Mau Sean
Optimization and thermal degradation kinetics of the cellulose nanoparticles (CNPs) production from coconut fibers were presented in this research project. The research project was carried out by using the data collected from the thesis with the title of ‘Dissolution of Natural Fiber using Ionic Liquid for Production of Cellulose Nanoparticles’ by Nadzirah binti Yahya. For optimization part, the CNPs production from coconut fibers was simulated using the Response Surface Methodology (RSM) via Central Composite Design (CCD) in Design Expert software to determine the relationship between the affecting parameters (extraction time, extraction temperature and ratio of coconut fiber (CF) to ionic liquid (IL)) on the response (ultrafine CNPs distribution). The simulation results showed that both the extraction temperature and CF:IL ratio were more significant to the regression model. The maximum ultrafine CNPs distribution obtained through the optimization process was 58.074 %, under the operating conditions of 30 mins of extraction time, 69.518 °C of extraction temperature and 0.01 w/w of CF:IL ratio. For the thermal degradation kinetics study of CNPs produced from coconut fibers, both the model-free isoconversional Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods were used to determine the activation energy, Ea of the CNPs. However, the calculated results of Ea were not satisfied, which were ranged from -0.039 to -3.134 kJ/mol. The values deviated very much from the Ea value of common CNPs, and the possible source of error was predicted to be from the inaccurate results from the collected data.
Synthesis of methyl acetate by lipase catalyzed esterification
(2021-06-01)
Izudin @ Mohamad, Muhammad Firdaus
The beginning of esterification process is mostly by using chemical synthesis with the help of chemical catalyst which often involved binary or tertiary azeotropic mixture which lead to difficulty in producing high purity of product and environmental issues. Hence, esterification with the aid of biocatalyst was introduced which is proven to have a better potential especially with lipase in producing esters through enzymatic esterification. In this study, methyl acetate which has high market demand due to its end uses was synthesise by direct esterification reaction catalysed by immobilized lipase from Candida rugosa by using n-hexane as organic solvent in batch system. Celite-545 was used as a support material on immobilized Candida rugosa lipase with catalytic activity of 0.6833 U/mg. One-Factor-at-One-Time (OFAT) method was studied in order to identify the effect of the optimizing parameters including reaction time, enzyme loading, agitation speed and substrate molar ratio of acetic acid and methanol. The optimal acid conversion for methyl acetate was 58% obtained at 2 hours incubation time with 10 U/ml of enzyme loading at 45 and 150 rpm of agitation speed with a substrate molar ratio of 1:3 (acetic acid to methanol). The comparison between kinetic models of enzyme catalysed esterification with the secondary data from the article was also performed by using non-linear regression analysis. (-rAc)fmax= 2.972 mmol/min.1.g, KmAc = 0.2488 mol/l, LmAl, KiAl = 0.953 x 10-3mol/l, KiAc = 1.03 x 10-3 mol/l.
Study on the effect of nitrite and free nitrous acid on cultivation of microalgae
(2021-06-01)
Chan, Jyh Loong
Chlorella vulgaris was widely used as potential nutrients elimination microalgae in wastewater treatment plant due to its high removal efficiency of total nitrogen (TN) and totalphosphorous (TP). The aim of this study was to study the effect of nitrite addition on microalgae cultivation by introduce 0 mg/L, 50 mg/L, and 100 mg/L of nitrite into batch reactors respectively, to investigate the effect of free nitrous acid (FNA) on microalgae cultivation by controlling microalgae cultivation condition in pH 4, 6, and 8 with addition 50mg/L of nitrite into batch reactors respectively, and to evaluate the influence of FNA concentration on the extracellular polymeric substances (EPS) secretion from microalgae by conducting EPS extraction as well as proteins and polysaccharides analysis. The results show that 50 mg/L of nitrite introduced into microalgae cultivation had highest growth rate in the result of oxygen inhibition had been eliminated, while 100 mg/L of nitrite introduced into microalgae cultivation had lowest growth rate because of high FNA concentration presented. Moreover, microalgae cultivation with addition 50 mg/L of nitrite and pH 4 culturing condition show the lowest growth rate, and the growth rate for microalgae cultivated at pH 8 had slightly higher than microalgae cultivated at pH 6. From the aspects of proteins and polysaccharides released in EPS, the peak points for protein (PN) concentration released with condition of pH 4, 6, 8 were 156.06 ug/mL (at first day), 171.35 ug/mL (at seventh day), and 173.71 ug/mL (at ninth day), while polysaccharide (PS) released with pH 4 was up to 91.02 ug/mL at third day and reduced to 13.43 ug/mL at seventh day which almost similar trend with others cultivation systems. In overall, microalgae cultivation with addition 50 mg/L of N and pH culturing condition more than 6 could enhance the microalgae cultivation.
Simulation of reactive distillation column of methyl tert- butyl ether production
(2021-06-01)
Shanmugasundaram, Parrathen
Reactive distillation is an efficient technique of combination of both reaction and separation in a single unit beneficial for equilibrium-limited reactions, cost-effective , reduce energy and improvement purity of the product. The usage of reactive distillation column has increased attention because of its high potential for process intensification and therefore this process needs to be studied fully so that the reaction conversion and purity of the product are assured before its implementation in industrial scale. In this work, Aspen Plus was used for simulation of reactive distillation column where methanol and butene undergo esterification reaction to produce Methyl tert-butyl ether (MTBE) and undergo continuous separation process. Firstly, the results are compared for both literature and simulation studies. The simulated results obtained by Aspen Plus showed that it is acceptable range since the simulation values obeyed that of the literature with a purity errors of top and bottom for MTBE is 0.0048% and 0.0026% respectively. In addiction, simulation results have been performed for sensitivity analysis. Sensitivity analysis on the same RadFrac model showed that reflux ratio of 7, number of reactive stages at 10, and reboiler of 11.45have significant effects on met MTBE purity. Sensitivity analysis conducted shows that the MTBE purity were maximum at reflux ratio 7. The best feed location for butene at stage 3 while methanol feed at stage 12.
Dynamic simulation of phenol adsorption using microwave induced coconut shell activated carbon
(2021-06-01)
Lim, Kai Wen
Coconut shell is a cheap, sustainable, and abundant resources in Malaysia as a raw material for making the activated carbon to be used as adsorbent in the adsorption process. In this study, the adsorption performance of the microwave induced coconut shell activated carbon is tested on the continuous adsorption of phenol by using ASPEN Adsorption software. The effects of the process parameters such as flow rate, initial phenol concentration and adsorbent bed height to the adsorption performance are investigated and the results showed that those 3 parameters have a significant effect on the adsorption performance. The adsorption performance of the phenol by using the microwave induced coconut shell activated carbon is evaluated by using the breakthrough time and the breakthrough adsorption capacity. The phenol adsorption performance is studied for both experiment and simulation and the results show a similar trend on the varying of process parameters. Higher amount of phenol is adsorbed on the activated carbon when the feed flow rate is lowered. In the other hand, the amount of phenol adsorbed also increased as the initial phenol concentration and bed height increased. The breakthrough behaviour of phenol adsorption is predicted by using three dynamic models which are Thomas model, Yoon-Nelson model and Adams-Bohart model. All three models are capable in providing a good fit to both the experimental data and simulation results based onthe high r2 values.
Gravitational ultrafiltration of river water fouling and cleaning efficiency study
(2021-06-01)
Bachok @ Joffri, Luqman Hakim
Gravity Driven Ultrafiltration System is a promising technology which could produce potable water to the community with no electricity and proper wastewater treatment. This project focuses on the construction of the non-point source, modular type GDU system to filter the river water using the Krian river as source water. The GDU systems are tested under both depleting and constant hydrostatic pressure conditions. Underdepleting hydrostatic pressure at 40 cm, the highest flux was found at 0.58 LMH and it reduce to almost zero due to reduction of hydrostatic pressure and exhaustion of river water in the module. The module can recover its flux up to 85.17% after being backwash for 5 cycles. Under constant hydrostatic pressure, it was found that 40 cm length hollowfibres produce the lowest permeation flux stabilization due to the larger extent of fouling. Therefore, the tendency for fouling is higher at longer membrane. This can be seen through the characterization of membrane using SEM and FTIR by comparing the pristine membrane with the fouled membrane. Water quality test using different parameters are used to determine the amount in the river water before and after undergoing GDU system. It was found out the concentration of parameters tested on the permeate water is lesser compared to the river water, especially on the bigger molecule. The quality of the permeate is safe for human activity according to the guideline outlined by WHO. The module can recover its flux up to 36.83,86.26 and 94.32% for 40,35 and 30 cm respectively after backwash for 5 cycles. The modular GDU system is promising to provide the clean water for the community that is deprived of electricity and water treatment facilities.
Adsorption of copper (ii) ions in wastewater using mangrove-based activated carbon
(2021-06-01)
Bong, Sock Ving
Water pollution due to the discharging of industrial wastewater consisting of heavy metals has become a serious issue. A cheap adsorbent is required to support the pollutant adsorption technique. Thus, the main goal of the research is to optimise the preparation and adsorption conditions of activated carbon from cheap raw materials. The production of mangrove-based activated carbon using microwave heating activation is cost-effective because mangrove is abundantly available in Malaysia and microwave heating requires less time and lower electricity. The optimal activated carbon was produced at 616 W and 2 mins under nitrogen flow. The ideal KOH: Char ratio was found to be at IR of 0.75 with 99.67% of activated carbon yield and 77.256% of copper (II) ions removal. The AC was examined by Fourier transform infrared spectroscopy, nitrogen adsorption/desorption isotherm and elemental analysis. Aside from optimisation, the adsorption process using the mangrove adsorbent was examined under various conditions. From the experimental data, the adsorption reached equilibrium after 3 hours at 10ppm and 60℃. Freundlich isotherm models with R2 values of 0.9995 and 1/n smaller than one explains the multilayer and heterogenous nature of adsorption. The maximum adsorption capacity of mangrove based activated carbon obtained using Langmuir Isotherm was 33.557 mg/g, which shows its intrigue value as a potential adsorbent. Furthermore, the data was well fitted to Pseudo-second-order kinetics models with R2value of 0.9997. Finally, the thermodynamic analysis revealed that the adsorption studied is endothermic process, and the adsorption is spontaneous at 50 and 60°C.
Esterification of ethanol and acetic acid catalysed by immobilized candida rugosa lipase
(2021-06-01)
Mohd Radzi, Nurul Adila
Ethyl acetate is a versatile ester used as solvent and diluents. The conventional esterification reaction of ethanol and acetic acid was catalysed by sulphuric acid, H2SO4. Enzyme is a sustainable approach for the esterification reaction to produce ethyl acetate. In this study, the esterification reaction of ethanol and acetic acid catalysed by immobilized candida rugosa lipase (CRL) in n-hexane was optimized. The free CRL was immobilized by physical adsorption on support, Amberlite XAD7 which resulted in specific activity of 0.13 U/mg. The effect of reaction time, temperature, substrate molar ratio and enzyme loading were studied. Maximum conversion of 88% was attained at 2 hours of reaction time, temperature of 50°C, acetic acid to ethanol ratio of 0.5 and enzyme loading of 80 U. Next, the kinetic modelling of bi-substrate enzymatic transesterification of ethyl butyrate was studied using secondary data from research paper. The data was fitted to the rate equation of the kinetic model using non linear regression to obtain the kinetic parameter. Based on the Lineweaver-Burk double reciprocal plot, the transesterification reaction follows ping-pong bi-bi mechanism with competitive inhibition by ethyl caprate. The kinetic parameters obtained was, Vmax = 1.1918 M, Km,A = 0.0117 M, Km,B = 0.1674, Ki,A = 0.1091 M, and Ki,B = 0.0031.
Amphoteric adsorbent coating for pharmaceutical waste (diclofenac sodium) removal
(2021-06-01)
Abdul Taib, Muhammad Haziq
The removal of diclofenac sodium (DCF) using a novel amphoteric absorbent coating (AAC) has been presented by this thesis. The formulation of the adsorbent was through a formation of a layer on the surface of a cotton cloth through facile method application using acrylic polymer emulsion (APE), smectite-based clay powder, and cationic polyelectrolyte (EPIDMA). SEM and EDX analysis were conducted for the characterization of the adsorbent coating. The experiments were carried out to study the effect of EPIDMA dosage, concentration, contact time, temperature, and pH of DCF solution on the removal efficiency of the DCF. The optimized percentage removal of DCF is at 77.06% at DCF concentration of 50 mg/L, temperature of 30°C and pH of 3 for 5 hours. Adsorption isotherms were developed to study the adsorption mechanism of the adsorption. This study has shown that the aforementioned parameters influence the performance of the AAC for DCF removal. With high removal efficiency and reusability, AAC was found to be a promising adsorbent for DCF removal from pharmaceutical wastewater system.
Adsorption isotherms and kinetic studies on the removal of lead (ii) ions by rubber seed coat
(2021-06-01)
Nor Hisyam, Nur Fatini
Rubber seed coats (RSC) were treated with acid and base to investigate the removal of lead (II) ions by adsorption process. Among all biosorbents that were investigated, base treated rubber seed coats showed the highest removal percentage of lead (II) ions. The experimental data were fitted to Langmuir, Freundlich, Temkin, Dubinin-Radushkevich and Halsey isotherm models to further describe the biosorption process. Generally, from adsorption isotherm models, base treated RSC have the characteristics such as having monolayer coverage of adsorbate on biosorbent surface, adsorption process of indirect interaction between adsorbent with adsorbate and it exhibits physical adsorption process. Next, experimental data were fitted to pseudo first-order, pseudo-second-order, intraparticle diffusion and Elovich model. RSC showed best fit in pseudo-second-order kinetic model. RSC showed that surface adsorption may be contributing to the rate controlling step in the biosorption of lead (II) ions on RSC and based on Elovich kinetic model, chemisorption may be the rate determining step at higher concentration of lead (II) ions.
Zinc removal from the industrial wastewater using activated carbon synthesized from mangrove
(2021-06-01)
Samsudin, Nur Fitri Syafiqah
Most of wastewater effluent contains dangerous heavy metals that must be appropriately handled. Heavy metal pollution is a serious problem in developing countries, as most industrial operations have increased heavy metal contamination in lakes, rivers, and other water sources. Thus, a substantial amount of research has been performed on low-cost adsorbents to examine their potential in heavy metal removal. As a result, a summary and assessment of mangrove as a low-cost adsorbent have been completed in this report. This study assesses the potential of activated carbon derived from mangroves for the removal of a specific heavy metal, zinc. Aside from that, the examination of the key factors that impact heavy metal removal, which are the effect of temperature, initial concentration, and contact duration on heavy metal removal, is also being examined. The adsorption capacity increased with the increase of initial concentration of Zn2+ from 1 ppm to 7 ppm resulted in an increase in adsorption capacity from 0.1604 mg/g to 1.1627 mg/g. As the temperature raised from 30°C to 60°C, the adsorption capability of Zn2+ were decreased indicating the process was exothermic. The capacity for Zn2+ adsorption reduced from 1.241 mg/g to 1.1627 mg/g as the temperature increased. For adsorption isotherm model, Freundlich isotherm model at temperature of 60°C is more suitable to describe Zn2+ adsorption on mangrove activated carbon due to higher correlation coefficient, R2 value at 0.5984. The correlation coefficient, R2 from the pseudo second order model for Zn2+ adsorption was 0.9959 which is higher than pseudo-first order model, 0.9695. This indicate that pseudo-second order is more suitable more kinetic adsorption model for Zn2+ adsorption.
Non-catalytic and solvent-free esterification of acetic acid with ethanol using coiled flow inverter for ethyl ethanoate synthesis in food industry
(2021-06-01)
Mohamad Alias, Nurul Aina
Non-catalyzed and solvent-free esterification of ethanol and acetic acid has been conducted in a novel intensified equipment, coiled flow inverter (CFI) to study the mixing performance of CFI in obtaining higher amount of ethyl ethanoate in a shorter time. The experimental study was carried out for very low laminar Reynold Number (Re) varies from 0.26 to 0.51 and for high laminar Re starting from 25 to 75 at constant volume ratio 3 : 1 of ethanol to acetic acid and at constant temperature 80℃. The effects of applying different Re towards the acid conversion and ethyl ethanoate concentration were examined. The mixing profile of fluids in laminar flow conditions were validated in COMSOL Multiphysics 5.5 while the aftermath of changing two CFI parameters either internal diameter of tube or coil diameter,was investigated via computational fluid dynamics (CFD) analysis in COMSOL. The experimental results showed that at very low laminar Re condition, high conversion ( > 80%) of ethyl ethanoate can be obtained as the Re decreased approaching 0. However, moderate conversion (>75%) was attained at shorter time when Re increased in high laminar Re condition due to efficient convective mixing created in CFI at high flow rates. It was also observed that smaller diameter of coil able to create more flow inversions while smaller inner diameter of tube promotes greater mixing flow efficiency in the tube. Optimum diameter of coil and tube inner diameter are crucial to be known as it can promote higher mixing efficiency and product concentration for processing ethyl ethanoate at shorter time for food industry.
The effect of carbon dots on conductive ink as a vitamin c electrochemical sensor
(2021-06-01)
Lee, Mun Yi
The demand for portable and disposable electrochemical sensors using conductive ink is increasing due to its flexibility and conductivity. With the recent discovery of carbon dots and its conductivity improvement, it can be modified as an additives in the conductive ink to see its effect as an electrochemical sensor towards vitamin C. In this study, an easy and inexpensive fabrication of unsupported sensor strips using carbon black (CB) as filler and alternate different binder such as polyvinyl alcohol (PVA) and polymethyl methacrylate (PMMA) was fabricated. The conductive ink prepared was casted on non-woven cloth using membrane casting tool and allowed to cured. It was then cut into standard sizes for characterization as well for cyclic voltammetry (CV) for vitamin C detection. The optimum of the conductive ink was 6:4 (m:m) CB: PVA, with higher molecular weight (MW) and hydrolysis degree (DH) of PVA. Crosslinking of PVA was not needed as it will decrease the conductivity of the ink. The lowest resistivity obtained for CB/PVA and CB/PMMA sensor strips were 0.357 ± 0.03 Ω·cm and 2.735 ± 0.2 Ω·cm which show CB/PVA conductive ink has more potential than CB/PMMA conductive ink and even commercial ink. The blending of carbon dots (CDs) was able to decrease the resistivity at optimum amount. However, CB/PVA sensor strip was not able to produce any oxidation and reduction peak in CV showing its non-responsiveness towards detection of vitamin C while CB/PMMA sensor strip was able to measure the vitamin C presence with limit of detection (LOD) of 0.622 mM and linear range of 5 – 15 mM. CDs was coated on CB/PVA and CB/PMMA sensor strips surface but only adhere to CB/PMMA which may due to porous structure of CB/PMMA sensor strip while detaching of CDs observed for CB/PVA. The CDs coated on the surface was able to decrease the resistance up to 36% for both sensor strips and increase the background current of CB/PMMA CV response showing improved conductivity. However, the peak current response decreased due to repulsion reaction of same negative charge of vitamin C and the carboxyl groups on CDs surface. Therefore, the CDs modification was deduced only suitable for detecting positive charge analyte. The proposed sensor strips exhibited great stability with a 10-cycles CV run in neutral, acidic but decent performance in alkaline condition.
Influences of freely suspended polyelectrolyte on aggregation kinetics of magnetic nanoparticles
(2021-06-01)
Azmi, Muhamad Syakir
This study was carried out to find the influences of freely suspended polyelectrolyte on the aggregation kinetic of coated magnetic nanoparticles. The nanoparticles was first coated with a polymer which is poly(sodium-4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDDA). It is hypothesized that the interplay between the depletion and electrosteric bridging effects would play a dominance role on influencing the colloidal stability of the coated magnetic nanoparticles. Such effect of having freely suspended polyelectrolyte in the suspension was studied at different concentration using UV-vis-spectrophotometer and qualitatively through colour change of the suspension over time. Through this study, it was observed that the aggregation rate and settling velocity of the naked IONPs suspension calculated was the highest at the values of 0.006/min and 0.0372mm/min, respectively. While PSS-IONPs and PDDA-IONPs has considerably lower aggregation rate which was 0.0021/min and 0.0027/min, respectively.The presence of the same charged polyelectrolyte in the suspension of coated nanoparticles will cause higher aggregation rate which was observed highest for the suspension of 100 ppm PSS-IONPs in 100 ppm PSS solution and 100 ppm PDDA-IONPs in 150 ppm PDDA solution with the rate of 0.0031/min and 0.055/min, respectively. Apart from that, the increase of concentration of polyelectrolyte in the suspension causes the sedimentation rate of nanoparticle clusters to decrease and lowest sedimentation rate observed was for suspension of 100 ppm PSS-IONPs in 100 ppm PSS solution and 100 ppm PDDA-IONPs in 100 ppm PDDA solution with the settling velocity of 0.00495mm/min and 0.0057mm/min, respectively. From imaging study, at higher concentration of polyelectrolyte an observable cluster size appeared earlier while the sedimentation rate slower.
Simulation study of biodiesel production via transesterification process from waste cooking oil
(2021-06-01)
Mohamad, Nurul Hazirah
Biodiesel is an environmental-friendly and alternative liquid fuel that can be used to substitute conventional diesel. It can be produced by a variety of feed stocks such as animal fats, non-edible oils and by-product of the refining vegetable oils. Biodiesel becomes a spotlight as a renewable fuel that is non-toxic and is biodegradable. It is usually synthesised by the transesterification of vegetable oil or animal fat with short chain alcohol such as methanol or ethanol. Its high oxygen content makes it a better choice for diesel engines. Waste cooking oil is one of the feedstocks that can be converted into biodiesel. Therefore, in this simulation study, waste cooking oil has been used as the raw material that reacted with methanol. This study was done by using Matlab software to observe how the operating conditions affect on the yield, conversion and selectivity of biodiesel. It was found that the temperature of 60 ̊C exhibited the highest yield of methyl ester. Oil to alcohol ratio of 1:15 gives the highest yield at 59%and catalyst weight of 1.4 wt % leads to the maximum yield of biodiesel. The simulation results obtained reasonable with the literature results and within the range studied by the previous researchers.
Comparison of different rsm designs to predict and optimize the acid violet (av 7) adsorption using rha-cfa adsorbent
(2021-06-01)
Mohamad, Ahmad Aqil Asyraaf
In this study, the factors affecting the performance of rice husk ash (RHA)-coal fly ash (CFA) adsorbent in removing acid violet 7 (AV7) dye were analysed using different type of response surface methodology (RSM). Face-Centered Composite Design, D-Optimal Design and Historical Data Design were compared based on the R2 value, Mean Square Error (MSE) and error in optimization section (%). DOD had the highest accuracy (R2 = 0.9765) in predicting dye adsorption efficiency, while FCC and HDD have lower accuracy but still in good value range (R2= 0.9335). By using Expert Design software, the optimum RHA-CFA adsorbent preparation condition with the highest AV7 dye adsorption efficiency was obtained through the numerical optimization of RSM models. Optimization by FCC and HDD, maximum adsorption efficiency obtained were 45.1% and DOD was 44.4% with RHA/CFA ratio of 3.00 and 1.00 M of NaOH. An additional experiment of RHA/CFA ratio of 3.00 and 1.00 M of NaOH is obtained from the literature and the result from it is used to compare with predicted values of each RSM design. DOD had the lowest error at value of 2.93% and both FCC and HDD models were 4.43%.

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