Science & Technology Development Journal - Engineering and Technology

Synthesis of polyamide thin film composite nanofiltration membrane for Arsenic removal

2020-01-17T12:35:47+00:00

Arsen (As) is one of the most detrimental substances in drinking water owing to its carcinogenic impact on human health. Among many techniques for removing Arsenic, membrane filtration process has emerged as an efficient technology for removing As from water. In this study, nanofiltration (NF) thin-film composite membrane based on polyamide is synthesized via interfacial polymerization between piperazine (PIP) in water and trimesoyl chloride (TMC) in hexane onto polyacrylonitrile (PAN) supporting substrate. The influence of PIP and TMC concentrations in the two insoluble solvents on the separation performance (flux and rejection) of the obtained membrane is studied. The physicochemical properties of the derived membranes are characterized by ATR-FTIR and pure water contact angle measurements. The separation performance of the membrane is evaluated for filtering pure water and 150 ppb arsenate (Na₂AsHSO₄) aqueous solution. The results indicate that the PIP and TMC concentrations affect the physicochemical properties and thus the separation performance of the polyamide membrane. The hydrophilicity of the membrane surface increases as rising the TMC concentration. Nevertheless, the increment of PIP concentration results in the decline of hydrophilic property of the membrane. The increase in TMC and PIP concentrations lead to increasing the As(V) rejection, while the TMC concentration is dominant to an increment of the thickness of the synthesized membrane. Thus, the permeability of the membrane decreases more significantly with an increase in TMC concentration. The PIP concentration of 2 wt.% and TMC concentration of 0.15 wt.% is found to produce the NF membrane for reducing As(V) in drinking water with high flux of 64 Lm^-2 h^-1 and good rejection of 95%.

Research to use vegetable oil to replace DOP to produce rubber products applied in water supply and drainage industry

2020-01-17T12:35:46+00:00

Nowadays di-2-ethylhexyl phthalate (DOP) plasticizer is commonly used for compounding in products made from rubber. However, there is an incresing concern about negative health effects (eg,. adversed sex hormone or breast cancer) upon exposure of phthalate plasticizers including DOP to human. In this research, epoxidized soybean oil (ESO) and cardanol (CDN) were evaluated as alternatives to traditional DOP at two different contents (20% and 25%). Rubber compounds were prepared on a two-roll mill and determined for optimum curing time (T90) by moving die rheometer at 150 ^◦C. Tensile strength, tear strength, and thermal stability of rubber compounds were also measured. The results showed that rubber compounds formulated with ESO and CDN had shorter curing times of 4.25 and 5.58 minutes respectively than the compound with DOP (6.25 minutes). Especially, the curing time is further reduced for the compound with ESO at a higher content. The value of tensile strength is similar for all three compounds with 20% plasticizer content. The rubber compound with 25% ESO content has a tensile strength of 12.8 N/mm² which is much higher than ones with DOP and CDN at the same content. Yet, compound with DOP showed a greater tear strength value of 52.94 N/mm² while the tear strength is only improved for compound with ESO upon reducing content. A similar result is also obtained when comparing the effect of three plasticizers in abrasion resistance test. Based on the acquired mechanical properties, we can conclude that ESO can be a good candidate to replace traditional phthalate in rubber products; especially it can fulfill requirements of rubber o-rings in drainage pipe system.

The application of Viscozyme to extract astaxanthin from Haematococcus pluvialis

2020-01-17T12:35:41+00:00

Astaxanthin is a natural compound, which has a higher antioxidant effect than vitamin C, has the effect of stimulating growth, resist some diseases, create attractive colors; so astaxanthin is widely used in agriculture and food, medicine, especially in salmon farming techniques. Astaxanthin is obtained from materials of natural origin such as seafood (shrimp shells, salmon), red yeast, microalgae, or from chemical synthesis. Haematococcus pluvialis is microalgae with high ability to synthesize astaxanthin. The subject is extracting astaxanthin from Haematococcus pluvialis by adding Viscozyme. The results showed that the conditions of extracting algae by enzyme were optimal at 40 ℃, 45 minutes with enzyme concentration at 2%, 35.60 mg/g of astaxanthin in dry algae and the ability to extract soluble substances reached 37%. Extracting astaxanthin using added enzyme gave better results than the non-enzyme sample with a high yield of 38%, the ability of astaxanthin in capturing ABTS free radicals with IC50 reached 13.53 mg/l, 3 times higher than vitamin C (IC50 40.50 mg/l) and higher than the non-enzyme sample. Astaxanthin is very insoluble in water; we’re making the complexes between astaxanthin and β-cyclodextrin to increase water solubility of astaxanthin. When the ratio of astaxanthin (extract) to β-cyclodextrin is 1/50, the efficiency of astaxanthin dissolution is the highest with astaxanthin concentration of 18.85 mg/l, this is a precursor of the application of astaxanthin to food, and beverage...

Effects of transient recovery voltage and degradation solutions when opening shunt reactor at 500 kV O Mon substation

2020-01-17T12:35:34+00:00

In 500 kV power systems, shunt reactors are usually used to control the reactive power balance and regulate the operating voltage within the permissible limits. Therefore, shunt reactors may be frequently switched daily. Using circuit breakers to switch shunt reactors will produce transient components during this period. When a shunt reactor is switched on, the inrush current will appear and when the shunt reactor is switched off, the transient recovery voltage (TRV) will occur between two terminal contacts in the circuit breaker. This paper will focus on analyzing TRV components that occur when opening the circuit breaker to interrupt inductive loads with small currents, namely the analysis of TRV that occurs when opening the circuit breaker of the shunt reactor 500 kV - 128 MVar at 500 kV O Mon substation by using ATP/EMTP transient analysis software. The simulation has indicated that the obtained results are suitable to the practical case and they are can be used a basis for a suggestion of solutions to reduce the TRV for other 500 kV substations with shunt reactors in Vietnam. This study also has significant technical and economic contributions. In the economy, the application of this model for shunt reactor circuit breakers will provide an evaluation of their TRV standing level in the practical operation, leading to reducing the maintenance and replacement costs of circuit breakers. In the technique, this solution will help to solve the problems of selecting appropriate circuit breakers, the best operation procedure, and effective reduction of TRV.

The surveys of the methods for reducing the water content of honey

2020-01-17T12:35:33+00:00

Honey is a nutritious, sweet-tasting drink with the natural fragrance of flowers, so it is favored and widely used in many areas of life. Hard qualitative norms on honey quality are such as color, content of HMF, reducing sugar, microorganisms ... One of the causes of rapid change in bile quality during use is the amount of water in honey. The surveys of the methods for reducing the water content of honey with the results obtained are as follows: Using temperature to reduce water content in honey makes honey color darker. Although silica gel is very effective in reducing water content, it reduces honey amount and changes the original honey scent. In particular, the “hive model” industrial equipment reduces the water content (18.08%) compared to the raw honey (22.01%). Analyzing the sugar components: fructose, glucose, maltose, and saccharose almost unchanged. Nine volatile compounds have been identified in samples of raw honey and honey with low water content, especially aromatic compounds that characterize the fragrance of nectar such as furanoid linalool oxide, cis- and furanoid linalool oxide in honey with low water content are not significantly lower compared to raw honey. During the 2-month follow-up period, honey with low water content had lower sugar content (3%) and HMF increase (9%) compared to the raw honey (11% and 41%). The results show that the method of removing water from honey is a solution to help stabilize the quality of honey preservation.

Temperature spreading simulation by using 3D model - thermal power plant in the coastal Degi, Binh Dinh

2020-01-17T12:35:30+00:00

Thermal energy accounts for more than 50% of the country's total power supply system and plays a particularly important role in the national power supply system. However, the process of cooling the turbine systems of plants and the discharge of used water after cooling are the reasons for the large impact on the aquatic environment and ecosystem. Therefore, it is necessary to calculate the distribution and dispersion of heat in coastal areas removed by thermal power plants. According to the project, the drain source was built near the cooling water intake, so it can affect the source of cooling water. The investor was also considering the construction of a dam to reduce the impact on the supply of cooling water. Both of these options should be considered and analyzed. Therefore, the research team applied a modeling approach to calculate and evaluate the effect of heat propagation in two scenarios. MIKE21, 3 FM instruments combined with meteorological - oceanographic data. The results showed that the source of discharge affected the inlet position in the station area, and during the construction of the dam, the degree of influence of the source of discharge on the source of cooling water intake of the Binh Dinh power plant was significantly reduced. Before starting the model, the calibration and verification steps are performed, which give satisfactory reliability.

Comparison of settlement between granular columns with and without geosynthetic encasement

2020-01-17T12:35:31+00:00

Granular columns have been used to improve load bearing capacity and to reduce the settlement of the soft soils for the past three decades. However, for soft soils with less than 15 kPa of undrained shear strength, the use of granular columns is ineffective because the soft soil does not mobilize sufficiently lateral confinement stress to balance the column lateral stress, which leads to the laterally deformed column (bulging) at the top section of the column. To overcome this limitation, many researchers have developed a new method of soil improvement using granular columns with geosynthetic encasement, which are actually an extension of the granular columns. This new approach, which is more advantageous than the granular columns, is thanks to geosynthetic providing additional confinement stress in conjunction with the soil surrounding the column. In this paper, the authors apply analytical solutions based on “unit cell concept” model in order to compare the effect of settlement between stone columns and stone columns with geosynthetic encasement implementing to reinforce the soft soil ground of Vifon II plant in Long An. The authors also investigate the effect on the column settlement due to variables of the column diameter, column spacing and embankment height. The results show that in all cases, the settlement of stone column is about 50-80% higher than stone column with geosynthetic encasement, which have proved the superior efficiency of geosynthetic encased column (GEC) compared to conventional stone applied in soft soil improvement.

Applying improved Backward/Forward method in optimizing power distribution connected DG

2020-01-17T12:35:36+00:00

In recent years, there is robust development of distributed generations (DG) connected into the electrical system. Thus, The issues such as the optimization problem of the position and capacity of power distribution sources has taken into account the re-configuration on the electricity distribution system to minimize the total Power loss on the ray distribution grid as well as minimizing the total calculation time which is an essential requirement. This paper proposes enhancement Backward/Forward method which is change for Newton - Graphson and Gauss - Seidel methods are being used. We used PSO optimization algorithm accompanied by power distribution calculation tool which is Backward/Forward method to calculate the power distribution in the optimsize location and capacitance of Distributed Generations considering the re-configuration of the electrolytic grid. The algorithm has been simulated on three IEEE ray power distribution systems which includes 3 types of power grids: 33-node power distribution system, 69 nodes and 119 nodes. Simulation result presents that our proposal improves the performance of distribution grid system and better than some other algorithms.