A.R. Abdul Aziz

Recent advances in DNA-based electrochemical biosensors for heavy metal ion detection: A review

The presence of heavy metal in food chains due to the rapid industrialization poses a serious threat on the environment. Therefore, detection and monitoring of heavy metals contamination are gaining more attention nowadays. However, the current analytical methods (based on spectroscopy) for the detection of heavy metal contamination are often very expensive, tedious and can only be handled by trained personnel. DNA biosensors, which are based on electrochemical transduction, is a sensitive but inexpensive method of detection. The principles, sensitivity, selectivity and challenges of electrochemical biosensors are discussed in this review. This review also highlights the major advances of DNA-based electrochemical biosensors for the detection of heavy metal ions such as Hg2+, Ag+, Cu2+ and Pb2+.

Fibre Optic Sensors for Selected Wastewater Characteristics

Demand for online and real-time measurements techniques to meet environmental regulation and treatment compliance are increasing. However the conventional techniques, which involve scheduled sampling and chemical analysis can be expensive and time consuming. Therefore cheaper and faster alternatives to monitor wastewater characteristics are required as alternatives to conventional methods. This paper reviews existing conventional techniques and optical and fibre optic sensors to determine selected wastewater characteristics which are colour, Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD). The review confirms that with appropriate configuration, calibration and fibre features the parameters can be determined with accuracy comparable to conventional method. With more research in this area, the potential for using FOS for online and real-time measurement of more wastewater parameters for various types of industrial effluent are promising.

Effects of niobium and molybdenum impregnation on adsorption capacity and Fenton catalytic activity of magnetite

In the present study, a number of modified magnetite samples were prepared by impregnating magnetite with Nb and Mo (Fe3−x−yNbxMoyO4, x + y = 0.2). The characteristics of the samples in terms of durability, crystalline phase, morphology, size, surface area and composition, and magnetic property were determined. Subsequently, the effect of Nb and Mo incorporation on adsorption capacity of magnetite and its activity in heterogeneous Fenton oxidation of methylene blue was investigated. The amount of MB adsorbed on the synthesized samples increased considerably, mainly due to the increase in their specific surface area. In addition, the presence of Nb and Mo significantly improved degradation of MB, especially at higher contents of Nb + Mo. About 90% of MB (100 mg L−1) and 46% of TOC were removed under the studied conditions. MB adsorption and Fenton degradation using synthesized samples were well described by pseudo-second-order and pseudo-first-order equations in kinetics, respectively. The samples demonstrated good durability and insignificant loss of performance in three consecutive experiments. The obtained results verified that Nb and Mo co-incorporation could effectively improve magnetite properties towards higher adsorption and remarkable activity in heterogeneous Fenton process at neutral condition.

Mechanistic analysis of cavitation assisted transesterification on biodiesel characteristics

The influence of sonoluminescence transesterification on biodiesel physicochemical properties was investigated and the results were compared to those of traditional mechanical stirring. This study was conducted to identify the mechanistic features of ultrasonication by coupling statistical analysis of the experiments into the simulation of cavitation bubble. Different combinations of operational variables were employed for alkali-catalysis transesterification of palm oil. The experimental results showed that transesterification with ultrasound irradiation could change the biodiesel density by about 0.3kg/m(3); the viscosity by 0.12mm(2)/s; the pour point by about 1-2°C and the flash point by 5°C compared to the traditional method. Furthermore, 93.84% of yield with alcohol to oil molar ratio of 6:1 could be achieved through ultrasound assisted transesterification within only 20min. However, only 89.09% of reaction yield was obtained by traditional macro mixing/heating under the same condition. Based on the simulated oscillation velocity value, the cavitation phenomenon significantly contributed to generation of fine micro emulsion and was able to overcome mass transfer restriction. It was found that the sonoluminescence bubbles reached the temperature of 758-713K, pressure of 235.5-159.55bar, oscillation velocity of 3.5-6.5cm/s, and equilibrium radius of 17.9-13.7 times greater than its initial size under the ambient temperature of 50-64°C at the moment of collapse. This showed that the sonoluminescence bubbles were in the condition in which the decomposition phenomena were activated and the reaction rate was accelerated together with a change in the biodiesel properties.

Fenton oxidative treatment of petroleum refinery wastewater: process optimization and sludge characterization

Sludge generation is one of the major concerns in Fenton treatment of recalcitrant wastewaters. In this work, mineralization (reduction of Dissolved Organic Carbon (DOC)) of petroleum refinery effluent (PRE) and the accompanying sludge generated in treating PRE was investigated. The mineralization level of 53% at optimum conditions produced 0.16 L of wet sludge per litre of wastewater. Further investigation of the sludge properties was conducted to assess the ease of handling and potential reuse of the sludge. For this purpose, sludge generated at studied conditions exceeding 30% DOC reduction were characterized by sludge volume index (SVI), sludge settling rates (Vs) and volumes of settled sludge within the first 30 minutes (SSV30). High Vs (≈0.16 cm s−1) and low SVI (<100 mL g−1) and SSV30 (<50 min s−1) values indicated that the sludge has good settling and compaction properties. The results confirmed that the sludge generated could be managed systematically with appropriate operating conditions.

Using D-optimal experimental design to optimise remazol black B mineralisation by Fenton-like peroxidation

The mineralisation of remazol black B (RBB) was studied at concentrations ranging from 20-1000 mgL−1. The work was aimed at investigating the Fenton-like peroxidation of RBB at a concentration typically obtained in Batik cottage industries. Other response parameters were degradation and colour removal efficiencies. The parameters that were measured included total organic carbon (TOC), chemical oxygen demand (COD) as well as absorbance for mineralisation, degradation and colour. To optimise the process, the interaction effects of several controlling variables on the treatment process were examined using dispersion matrix-optimal design and response surface analysis. Four specific variables: initial dye concentration (Dye)o; the molar ratio of oxidant to dye organic strength (H2O2):(COD); the mass ratio of the oxidant to the catalyst (H2O2):(Fe3+) and reaction time (t r), were observed. Three reduced empirical models, one for each response, were developed for describing the treatment process. For 20, 510 and 1000 mgL−1, the optimum %TOC reduction and oxidation times were 44% for 95 min, 52% for 52.5 min and 68% for 10 min corresponding to 67, 81 and 75% COD reduction, respectively. The optimum COD reduction and oxidation times were 89% for 95 min, 91% for 10 min and 84% for 95 min for concentrations of 20, 510 and 1000 mg L−1, respectively. For all concentrations, total colour removal was achieved. A comparison of the results obtained in this study with literature values for traditional Fenton, photo-Fenton and photo-Fenton-like oxidation indicated that the TOC reduction obtained using the Fenton-like process was satisfactory.

Temperature Compensation in Determining of Remazol Black B Concentrations Using Plastic Optical Fiber Based Sensor

In this study, the construction and test of tapered plastic optical fiber (POF) sensors, based on an intensity modulation approach are described. Tapered fiber sensors with different diameters of 0.65 mm, 0.45 mm, and 0.35 mm, were used to measure various concentrations of Remazol black B (RBB) dye aqueous solutions at room temperature. The concentrations of the RBB solutions were varied from 0 ppm to 70 ppm. In addition, the effect of varying the temperature of the RBB solution was also investigated. In this case, the output of the sensor was measured at four different temperatures of 27 °C, 30 °C, 35 °C, and 40 °C, while its concentration was fixed at 50 ppm and 100 ppm. The experimental results show that the tapered POF with d = 0.45 mm achieves the best performance with a reasonably good sensitivity of 61 × 10−4 and a linearity of more than 99%. It also maintains a sufficient and stable signal when heat was applied to the solution with a linearity of more than 97%. Since the transmitted intensity is dependent on both the concentration and temperature of the analyte, multiple linear regression analysis was performed to combine the two independent variables into a single equation. The resulting equation was then validated experimentally and the best agreement between the calculated and experimental results was achieved by the sensor with d = 0.45 mm, where the minimum discrepancy is less than 5%. The authors conclude that POF-based sensors are suitable for RBB dye concentration sensing and, with refinement in fabrication, better results could be achieved. Their low fabrication cost, simple configuration, accuracy, and high sensitivity would attract many potential applications in chemical and biological sensing.

Determination of kinetic parameters for thermal decomposition of bamboo leaf to extract bio-silica

ABSTRACT Bio-silica has many applications due to its high reactivity and pozzolanic properties. The extraction of silica from biomass such as bamboo leaf is usually accomplished by thermal decomposition. Currently, the thermal decomposition requires external heat energy input. In this work, the possibility to reuse the heat released during thermal decomposition to make the process self-sustained is explored. The kinetic parameters of the combustion were determined by fitting thermogravimetric analysis (TGA) data to the Flynn–Wall–Ozawa model, where the corresponding activation energy and frequency factor are 211.7 ± 3.8 kJ mol−1 and 4.5 × 1015 s−1, respectively. The lower heating value of bamboo leaf determined is 8.709 kJ g−1, which is comparable to common wood fuels. Hence, the heat released in the combustion of bamboo leaf can be reused to make the process self-sustainable.

Quantitative risk assessment for the transport of ammonia by rail

Risk assessments are considered to be an essential tool in ensuring the safety of engineering projects. The benefits of using risks assessments have prompted its acceptance in the safety legislation for a number of industries. The use of quantitative risk assessment for rail transportation of hazardous materials has gained more attention in recent years, because the amount of the transported hazardous materials is large, and the transportation route often passes through populated areas, such as cities. In this study, the risk for the ammonia transportation by rail in Malaysia was conducted by combining the results from a previous failure frequency analysis and consequence analysis. The assessment results acknowledged the significant effects of train speeds on the overall individual risk. The risk with a tolerable risk limit of 1 × 10−6 per year increased significantly with more train accidents occurring at increasing speeds. Most of the surrounding populations along the transportation route analyzed are exposed to higher risk levels than the tolerable limit. This risk exposure to the public demonstrates the need for proper planning of moving ammonia through populated areas.

Analysis and Optimization of Ultrasound-Assisted Alkaline Palm Oil Transesterification by RSM and ANN-GA

In this study, the effects of ultrasound irradiation on transesterification process and characteristics of the synthesized biodiesel were investigated. The study was divided into two parts. In the first part, response surface methodology (RSM) and Central Composite Design (CCD) were employed to design experiments, develop the regression model, and evaluate individual and interactive impacts of five independent operational variables. The obtained results were then predicted by an optimized artificial neural network-genetic algorithm (ANN-GA) algorithm. The estimated results were compared with the experimental results. In the second part of the work, the impact of ultrasound irradiation on the main characteristics of the synthesized biodiesel was investigated. The analysis of the operating conditions indicated that reaction temperature and MeOH:oil molar ratio were the most important variables on reaction yield. The experimental results showed that there was a change in the main properties of the synthesized palm oil biodiesel with the density changed by about 0.3 kg/m3, viscosity by 0.12 mm2/s, pour/cloud point by 1–2°C, and flash point by 5°C, depending on different combinations of operational parameters. Besides, the numerical optimization technique was employed to optimize process variables in order to obtain the maximum FAME content (reaction yield) along with the best properties using both RSM and ANN-GA techniques. The maximum reaction yields of 95.2% and 95.1% were predicted by the RSM and ANN-GA models, respectively, at the optimum conditions. The conditions predicted by RSM and ANN-GA proved to be feasible for modeling and optimizing transesterfication yield with an accuracy of 99.18% and 99.14% and biodiesel properties of 98.61% and 98.28%, respectively.