Issues: Kỹ thuật và Công nghệ cho Phát triển bền vững Vol 33.4 (10/2023)
1. Thermal and Thermo-oxidative Degradations of Polyvinyl Alcohol with 2,5-Furandicarboxylic Acid Acting as A Crosslinking

Pham Thi Ni, Tran Hoang An, Pham Thu Phuong, Nguyen Ngoc Mai, Tran Quang Tung, Tran Thi Thuy*

This study assesses the thermal and thermo-oxidative for PVA with 2,5-furandicarboxylic acid (FDCA) acting as a crosslinking. PVA-crosslinked-FDCA were synthesized via catalyst-free solid-state esterification at 120 °C. PVA and FDCA with different contents of inorganic phase (1, 5, and 10 % (w/w)) were characterized by Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy. The thermal degradation of the obtained products was studied by Thermal Gravimetric Analysis/ Differential Thermal Gravimetric Analysis under air and nitrogen atmosphere. The effect of FDCA content on thermal and thermo-oxidative stability of PVA was discussed. The thermal stability of PVA was significantly improved, particularly at low FDCA concentrations of 1% and 5%. In these cases, the degradation maximums occurred at 361°C and 375°C, respectively, compared to 300°C for unmodified PVA in a nitrogen atmosphere. Moreover, the degradation maximums occurred at 363°C and 399°C, respectively, compared to 337°C for unmodified PVA in an air atmosphere. In addition, thermal stability of the films under air is even better than that under nitrogen atmosphere.

Article Code:23033

# Poly(vinyl alcohol), 2,5-furandicarboxylic acid, crosslinking

Page: 1-7

Field: Chemical Engineering
2. Effect of Key Parameters on Heterogeneous Fenton-like Oxidation of Indigo carmine catalyzed by Fe2V4O13

Nguyen Vân-Anh*, Bui Ba Canh, Cao Hong Ha

In this study, Fe2V4O13 nanoparticle (FeV2) as a hetero-Fenton catalyst was synthesized using a low-temperature hydrothermal method and characterized by X-ray, SEM, EDX, TEM and Raman techniques. The effectiveness of the heterogeneous Fenton catalyst of FeV2 towards the degradation and mineralization of indigo carmine dye (Ind, 0.1 mM) was studied by UV-Vis, ICP-MS and COD measurement. The optimal conditions for maximum degradation were pH 4, 66.7 mg/L of Fe2V4O13, 0.3 mM of initial H2O2 concentration with 0.1 mM of initial Ind concentration, at a reaction temperature of 298K. The effect of temperature on the reaction was also investigated, resulting in the activation energy of the reaction Ea = 53.5 kJ mol-1. Using the Eyring equation, activated parameters were calculated, indicating the controlling parameter is the activated enthalpy, the step of activated complex formation is an associative and endothermic reaction. It also performed that the FeV2 catalyst was highly influential in the degradation and mineralization of indigo carmine dye, with a degradation efficiency of more than 90% and 85% of COD after 10 minutes under the optimal operating condition. Additionally, the FeV2 catalyst displayed good stability after four cycles, indicating that Fe2V4O13 could be a promising catalyst for treating textile dye wastewater containing indigo carmine.

Article Code:23032

# heterogeneous Fenton-like system, hydroxyl radical, Indigo carmine, textile dyes, wastewater

Page: 8-16

Field: Chemical Engineering
3. Nitrogen Removal by Sulfur-Based Carriers: Effect of Physical Properties of Carriers on Autotrophic Denitrification

Tran Duc Thao, Nguyen Tan Phong*, Vo Thi Kim Quyen, Pham Ngoc Hoa, Nguyen Thu Hien

Sulfur-based autotrophic denitrification is an effective treatment technique to remove nitrogen in water and wastewater, in which sulfur compounds act as an electron-donors for the conversion of nitrate to nitrogen gas by autotrophic microorganisms. The main advantage of this process is no external organic carbon source compared with the conventional heterotrophic denitrification process, which resulted in reducing the cost of treatment and the poisoning effect of some organic carbon compounds. In this study, two sulfur-based carriers (C1 and C2) which have different mass ratios with the same core components as elemental sulfur and calcium carbonate but varying adhesive volumes were prepared to evaluate the sulfur-driven denitrification performance. The results show that the nitrate removal rates of C1 and C2 were 0.34 ± 0.04 and 0.32 ± 0.02 kg NO3--N/m3/d, respectively. Beside that, the sulfate concentration generated by autotrophic denitrification were quite high at 273.5 ± 27.8 and 251.3 ± 17.0 mg SO42-/L, respectively.

Article Code:23048

# Sulfur-based carrier, autotrophic denitrification, pore size, Thiobacillus, Sulfurimonas.

Page: 17-23

Field: Environmental Science and Technology
4. Research to synthesize cationic polyacrylamide emulsion use for treatment wastewater drain from the paper-making process

Nguyen Huy Tung , Nguyen Pham Duy Linh , Bui Tien Thanh *

Cationic polyacrylamide emulsions (CPAM) are widely applied in industries such as petroleum extraction, paper-making, cosmetics, and wastewater treatment... Currently, on the market CPAM products are very diverse, depending on the needs of each field the selected products have different characteristics such as molecular weights, and cation content... For paper wastewater treatment, CPAM is required to have a cation content of 30–40% and a molecular weight of 6–12 million Da. There are many studies on synthesizing CPAM, but most of them have been implemented by traditional methods, investigating each factor affecting the polymerization process of CPAM, product characteristics as well as the conversion of a synthesis reaction, none has suggested the simultaneous influence of input parameters. In this study, a new approach to finding the optimizing condition for reaction by using model Box – Behnken in Design Expert software. The obtained regression equations and response surface model could help to find the optimizing input factors for reaction faster, saving research time for developing new products and reducing the production costs compared to traditional methods. Additionally, due to the emulsion having a short storage time, so quick optimization of the synthesis conditions for CPAM production could help manufacturers can localized products to rapidly satisfy market demand instead of waiting for import, sometimes products over pot life due to a long time of transportation. This study obtained copolymers with a molecular weight of 8.042.957 Da, a cation degree of 35.68% with optimal conditions: monomer concentration of 25%, the content of cation monomer of 40.70%, the content of initiator of 0.54%, stirring speed of 2600 rpm, reaction temperature of 61°C, and reaction time of 7 hours. The results of trial testing to treat the wastewater collected from the paper-making process show that the synthetic CPAM has a similar performance compared with imported CPAM on the market.
The characterization of CPAM and sludge samples after treatment performed by analysis: FTIR infrared spectroscopy and 1H-NMR magnetic resonance spectroscopy, dynamic light scattering method- DLS, permeation chromatography method gel- GPC, and thermal analysis method TG-DSC. The surface structure of the sludge were analyzed by SEM images.

Article Code:23035

# emulsions, cationic polyacrylamide, molecular weight, cationic degree, paper industry wastewater

Page: 24-31

Field: Chemical Engineering
5. Effect of temperature on mechanical energy absorption of graphene-based honeycomb structure doped boron and nitrogen

Nguyen Minh Son, Nguyen Hoang Linh, Tran The Quang, Vuong Van Thanh, Do Van Truong*

Numerous applications require the use of energy absorption materials (EAM), such as helmets and bulletproof vests. Graphene-based carbon honeycombs (GCHs) are a special type of EAM that have garnered significant attention from scientists due to their mechanical energy absorption capacity, which can reach up to 5440MJ/m3, as well as their high stability under high temperatures. GCHs have shown great potential as mechanical energy absorbers. However, there have been few studies on honeycomb structures made from monolayer C3B, C3N, and NB, which also have mechanical potential similar to graphene. This study focuses on investigating the energy absorption capacity of C3B, C3N, and NB-based honeycomb structures (GBNHs). The study found that GBNHs have an energy absorption capacity of over 5500MJ/m3 and an anti-penetration ability exceeding 9000MJ/m3. These results provide insight into the potential for using GBNHs as a novel and promising EAM in the future.

Article Code:23019

# Temperature effect, Boron-nitrogen honeycomb structures, Energy absorption materials, Molecular dynamics.

Page: 32-40

Field: Materials Science and Engineering
6. Research For the Production of Environmentally Friendly Material from Industrial Waste Stone Powder by Geopolymer Technology

Pham Anh Tuan, Nguyen Thanh Cong, Bui Chuong, Ha Thu Huong*

Geopolymer technology was applied for environment friendly material fabrication with 20 – 23 wt% waste stone powder from artificial stone production process and 0.5 wt% of Na2SiO3 liquid glass (39 wt%). The material met the technical requirements according to TCVN 6477:2016 standard for unburnt material. The time of co-hydrolysis reaction help to create the Si-O-Si interspersed with bonds was not affected by the curing process of PCB40 with the presence of liquid glass (Na2SiO3.nH2O). We are creating a geopolymer network and helping the material reduce brittleness and increase ductility and compressive strength of conventional cement. The peak region at 959 cm-1 of FT-IR analysis and the surface structure morphology of SEM images showed that the Si-O-Al/Si-O-Si bond was formed by the reaction of Na2SiO3 with cement. The surface of the geopolymer material is denser and more tightly bound than the sample without Na2SiO3. The manufacture of unburnt materials from waste stone powder from the artificial stone production process by TCVN 6477:2016 can open a new treatment direction for this type of waste, reducing the harmful effects of landfill on the environment.

Article Code:23028

# geopolymer, sodium silicate, unburnt materials, waste stone powder.

Page: 41-48

Field: Materials Science and Engineering
7. Nitrogen Doped Carbon Dots: A Brief Review on Heavy Metal Ion Sensing

Shweta Vyas*

Carbon dots (CDs) are zero dimensional carbonaceous nanomaterials showing tremendous physicochemical and optical properties, synthesized from any organic precursors rich in carbon content. Due to their greater biocompatibility, non-toxicity, and tiny particle size up to 10 nm, CDs have numerous applications in the field of nanosensing, bio-imaging, solar energy, light-emitting devices, photocatalyis etc. The doping of CDs with any heteroatom can improve photoluminescence (PL) properties with great photo tability and enhanced sensing limits. Thus doped CDs are in great demand for many advanced applications, including sensing heavy metal ions. Herein, Nitrogen doped CDs (NCDs) are reviewed in the light of bottom-up preparative methods to compare their optical and sensing properties towards detection of specific heavy metal ions. From this study, it is revealed that NCDs can detect specific heavy metal ion with higher selectivity by fluorescence quenching or enhancing. The PL quenching of NCDs was found to be more commonly reported for the detection of wide range of metal ion concentrations. It is revealed that NCDs propose a low-cost technology to detect toxic heavy metal ions in aqueous media, without use of any sophisticated instrumentation and specific organic ligand.

Article Code:23051

# Carbon Dots, NCDs, Heavy metal ions, Photoluminescence.

Page: 49-55

Field: Materials Science and Engineering
8. Optimizing Dump Diffuser in Gas Turbineby Bleeding Air Method and Vortex Generators

Duc-Huy Ta, Phuong-Nam Nguyen, Trong-Cuong Pham, Thi-Mai-Anh Bui, Van-Minh LE*

The diffuser is a component that connects the combustion chamber and the compressor in a gas turbine engine. Its main function is to slow down the airflow supplied by the compressor to enhance efficient combustion and avoid excessive total pressure loss. Therefore, the effectiveness of the diffuser is evaluated based on two values: the total pressure loss coefficient and the static pressure recovery coefficient. The smaller the total pressure loss coefficient, the better the static pressure recovery coefficient. In previous studies, attention and research have been given to the inlet angle of the diffuser. It has been observed that there is a clear flow separation on the diffuser wall before the angle of the front diffuser wall is extended to a certain degree. This increases the region of recirculation vortices, thereby increasing the total pressure loss of the system and adversely affecting the performance of the diffuser. However, there have been few studies addressing this issue. In this research, two methods are introduced to improve the diffuser: the bleeding air system and the using vortex generators. This study used numerical methods to simulate the 3D model of the diffuser. The computational results show that swirl generators and air injection methods can be observed to delay the separation process in the front diffuser and reduce the total pressure loss and improve the performance of dump diffuser by over 20%.

Article Code:23031

# dump diffuser, pressure loss, flame tube, vortex generator, bleeding air

Page: 56-62

Field: Mechanical Engineering