Key Engineering Materials Vol. 797

Abstract: Titanium dioxide (TiO₂) photocatalyst is one of the promising semiconductors used for the degradation of commercial dyes. However, it has to be doped with other metals to increase its efficiency, reactivity and stability. This study was carried out to synthesize hybrid Cu-doped TiO₂ using wet impregnation method by varying the loading of copper precursor (0.3-1.0 wt%), incubation temperature (50-90°C) and incubation time (1-24 h). The synthesized hybrid Cu-doped TiO₂ was characterized using XRD, EDX, FESEM and BET to obtain the structural, elemental, and surface morphological information. The photocatalytic activities of the synthesized Cu-doped TiO₂ were investigated for the degradation of methyl orange (MO) under UV-light irradiation. The results revealed that the optimum Cu loading was at 0.5wt% Cu with incubation temperature of 50°C and 2h incubation time. The hybrid Cu-doped TiO₂ showed an excellent dye degradation efficiency ranging from 40-82% under UV-light irradiation.

Abstract: The conditions (adsorption duration and pH) for removal of nickel ions from nickel electroplating wastewater by adsorbing on activated carbon were studied. Ni/AC catalysts prepared by adsorption under alkaline conditions with high removal rate of Ni(II) has been chosen for catalytic steam reforming of toluene, and its catalytic performances were evaluated compared to that of Ni/AC catalysts prepared by impregnation. Alkaline conditions facilitated the removal of Ni(II) from nickel electroplating wastewater by AC and pH=9 in especial, was a critical point above which Ni(II) could be removed efficiently. The removal rate within 20 min reached up to more than 97%. After H₂ reduction, the catalytic activity of Ni/AC-Ad was observed in catalytic steam reforming of toluene and then gradually decreased with the reaction time. Both the toluene conversion and hydrogen production with Ni/AC-Ad were about 65% of those with Ni/AC-Im at similar Ni loading rate. Under alkaline conditions, most of the nickel adsorbed on AC was Ni(OH)₂ complex. This adsorption state led to a larger average size of nickel particle in Ni/AC-Ad than that in Ni/AC-Im. The uneven size of nickel particles on the surface caused poor dispersion of active spots, agglomeration and sintering, resulting in gradual deactivation of Ni/AC-Ad prepared under alkaline conditions during catalytic steam reforming of toluene.

Abstract: Gasification is raised as the most promising technologies of municipal solid waste (MSW) removal as well as energy recovery. The principal problem related with the gasification process is the high amount of tar released during the gasification process that causes environmental and operational problems. The purpose of this study is to investigate the performance of MSW gasification using tyre char as an alternative option for catalytic gasification to produce tar free clean gas. Catalytic performance of tyre char was compared with performance of MSW gasification alone without the tyre char in a bench scale downdraft reactor. The waste tyre char removed 80% of tars in syngas at 700 °C. Analysis of the syngas compositions indicated that concentration of H₂ and CO were significantly increased. Therefore, it was concluded that chars especially tyre char can be an effective and inexpensive catalyst for tar removal and syngas production of MSW gasification.

Abstract: The objective of this study was to evaluate the ability of ultrasonic irradiation to remove ammonia-nitrogen in synthetic solution by considering the factors including initial concentration, pH and irradiation time. Ultrasonic bath was used to provide a constant effective power, frequency and temperature of 150 W, 37 kHz and 60°C, respectively during sonication. It was revealed that the removal efficiency of ammonia-nitrogen improved at lower concentration with basic water environment and extended irradiation time. Based on this judgement, optimization is carried out by using response surface methodology (RSM) of Box Behnken design to develop a quadratic regression model in order to analyze the interactions between the three factors and their effects on the removal efficiency. Optimum removal achieved from the model was found to be 82.26% at 10 mg/L of initial concentration with pH of 11 and sonication for 30 minutes. Verification of the quadratic regression model is done by comparing with the experimental work conducted within the experimental domain.

Abstract: In this paper, chemically modified cellulose was used instead of cellulose as it offers higher adsorption capacities, great chemical strength and good resistance to heat. As part of Phyto-Adsorption Remediation Method, citric acid modified cellulose (CAMC) was used to treat ferric ion. However, there is a large possibility that CAMC molecule might interact with water molecule that contain hydrogen bond and hence pose as a competitor to ferric acid and reduces the efficiency of CAMC in ferric ion removal. Thus, the aim of this work is to identify the most stable hydrogen bond between CAMC and water, by using a computational technique. The interaction between the water molecules and CAMC was observed by varying the volume of water molecule with modified cellulose by an expansion in amorphous region. The simulation result shows that for water loading less than 20 molecules, the interaction between water molecules and CAMC is higher at temperature 311K, whilst for water loading higher than 20 molecules, the interaction weakens at higher temperature. This work proves that water molecules have the tendency to bind to carboxyl group of glucose, to oxygen of ester and to oxygen of anhydride acid of the CAMC molecule, which might pose a competition for ferric acid removal. The calculation of coordination number has shown that the number of atoms present in the first hydration shell (of radius < 2.5Å) is more as the temperature increases from 298K to 311K, which indicates that the adsorption is better at higher temperature. For hydration shell at radius >2.5Å, cell temperature is not significant to the number of atoms present.

Abstract: Malaysia is one of the countries that strongly promotes industrial development. Therefore, industrial activities have grown rapidly since the 1980s. However, since the development of the country's industry, the country has experienced several major accident hazards, thus sacrificing many lives, causing assets and environmental destruction. For example, Bright Sparklers explosion incident that occurred on 7^th of May 1991 in Sungai Buloh had killed 26 people, injuring more than 100 people and damaging more than 200 residential properties. While at Johor Port Sand Warehouse, a large fire had occurred at Petronas terminal and destroyed three storage tanks and 720,000 liters of petroleum and 240,000 of aviation fuel. This fire has resulted in 100 firefighters. In the latest 2018 incident, Malaysia was shocked by a major fire at Kemaman Bitumen Company. The results of these three insights indicate that a comprehensive analysis needs to be made to assess land use and other risk management decisions. Malaysia is the world’s largest rubber glove producer, therefore, the quantity usage of chlorine is high. As noted by Agency for Toxic Substances and Disease Registry, chlorine is harmful to human body when it is handled improperly. In this paper, a study was conducted to assess the impact of the use of chlorine gas at the rubber glove manufacturing plant. Quantitative risk analysis is used as a tool to prevent major failure in storage, production and transportation of chemicals has been issued. Therefore, this paper investigates the consequences of risk posed by chlorine incident release under wind rose effect at rubber glove manufacturing industry.

Abstract: Succinic acid is a potential co-former to produce co-crystal, thus an understanding of the dissolution behaviour of succinic acid crystal is crucial for designing the co-crystal. In this works, α-succinic acid was chosen as a model compound for this study regardless its attractive crystal chemistry and its diverse surface properties. The aims of this study are to analyse the morphology of succinic acid crystal (form A) and to analyse the dissolution behaviour of succinic acid crystal (form A) in the ethanol solution using molecular dynamic simulation. Prediction of form A succinic acid morphology were conducted with different combination of charge set and potential function i.e ESP and CVFF which produces hexagonal needle-like shape morphology and shows good agreement with the experimental crystal shape. Dissolution of α-succinic acid in ethanol solvent was investigated using dynamic simulation. Visual observation and mobility assessment shows that the molecules at the edge of the crystal tends to dissolve faster compared to the molecules at other position on the facet.

Abstract: Carbamazepine (CBZ) is well known to have low solubility, hence an understanding of crystal behaviour is vital to improve the solubility of the drugs, hence for the oral bioavailability. The objectives of this work are to assess the morphology prediction of the most stable form of CBZ, which form (III) and to access the dissolution behaviour of the crystal. Material Studio 4.0 was used to predict the morphology of CBZ form (III) based on attachment energy calculations in vacuum condition by using the combination of MNDO charges from MOPAC with PCFF potential function. Later, predicted morphology was used for dissolution prediction in ethanol solvent using dynamic simulation with CVFF potential function. From the result, the morphology prediction of CBZ form (III) produced hexagonal – like shape with seven dominated facets; (011), (11-1), (100), (10-2), (020), (110) and (11-2) with the most morphological important is (011) face with 45.23% area while the fastest growing facet is (11-2) which only 0.91% area contributed to the whole crystal. The lattice energy calculated was -21.62 kcal/mol with only 1.36% error compared to the experimental value; -21.33 kcal/mol. The dissolution prediction result shows that small facet area with the amine and carbonyl groups exposed at the surface will dissolve readily than the other facets. This result explains that the small facet area with protruding functional groups that can form the hydrogen bond to ethanol molecules will be the most favourable facet to dissolve.

Abstract: Artificial pancreas (AP) device consists of continuous subcutaneous insulin infusion (CSII)pump, continuous glucose monitoring (CGM) sensor, CGM receiver amd control algorithm which measure and regulate current blood glucose level (BGL) of type 1 diabetes (T1D) patients in automated manner. All components of the AP device are now well-established and readily avaialble in the market; however, its control algorithm is still at infant stage. This sometimes leads to insufficient or excessive amounts of insulin injected into their body causing hyperglycaemia or hypoglycaemia episodes, respectively. Mathematical equations of Hovorka model were widely used in the control algorithm; however, the model had shown somewhat lacking in terms of interaction and interrelation of selected parameters in its glucose-insulin dynamics. An attempt was made by previous workers to modify certain subsytem equations in the Hovorka model involving glucose, plasma insulin and insulin action subsystems by introducing additional parameters which, in turn, resulted in producing so-called improved Hovorka equations. This study aims to develop a computer algorithm in oder to simulate the BGL of T1D patient during their meal intakes using the improved Hovorka equations via MATLAB and model based predictive control (MPC). Resuls showed that different amounts of administered insulin (U_t) namely; 0.0003 U/min and 0.009 U/min were required to maintain the BGL within normal range (4.5 to 6 mmol/L) when the amounts of meals (D_G) taken by the patient were at 57g CHO and 86.5g CHO during lunch and dinner times, respectively. However, the BGL was above the normal range, i.e. hyperglycaemia when D_G and U_t were at 32g CHO and 0.035 U/min, respectively during breakfast time. In conclusion, this study has proven that the improved Hovorka equations can be used to simulate the meal disturbance effect on BGL for T1D patients.

Abstract: Antimicrobial resistance (AMR) is one of the most serious public health threats that results mostly from the selective pressure exerted by antibiotic use and abuse. AMR has become a major problem with global human deaths due to antibiotic resistant infections predicted to reach 10 million by 2050. Antimicrobial peptides (AMPs) has been discovered to have capabilities to kill microorganisms and can take other roles as an alternative to antibiotics which is favorable to the need of minimizing the usage of antibiotics as they lead to the increasing of AMR. AMP can be found naturally in almost all domains of life as part of the innate immune system to combat virus, bacteria, fungi and even cancer cells. It can also be extracted from food proteins using enzymatic hydrolysis. High antimicrobial properties/activities are depend on the degree of hydrolysis (DH) of peptides, peptide source/origin, and type of enzyme used for the hydrolysis process. There are several other variables that can be manipulated to optimum condition to obtain high DH. Variables such as temperature, pH, enzyme concentration and hydrolysis time have proven to bring impact to the DH of peptides. Other bioactive peptides that have been discovered during the process have great potential to bring benefit in medicinal and nutraceutical areas.