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Coal ?y ash from coal-fired power stations in Vietnam, which can cause serious environmental problems if managed improperly, is a promising silicon source for zeolite synthesis. This paper investigated the effects of ultrasound (UTS) energy on the extraction of silicon from the coal fly ash produced by the Duyen Hai thermal power plant using a 20-kHz probe immersed in the reaction mixture. Silicon was extracted from the ?y ash in an alkaline solution at different temperatures, times, and ultrasonic powers. The second-order design, or the central composite design, was employed to investigate the effect of each parameter on silicon extraction. Data analysis was performed by Response Surface Methodology (RSM) using Design Expert software. With ultrasound assistance, the efficiency of silicon extraction reached 65.92 %, which is a very high extraction efficiency considering the short extraction time and lack of fusion step. With the use of ultrasound, the extraction efficiency is significantly increased compared to the fusion method. The optimal region predicted from the empirical modeling is around the center point (90 °C, 50 min, 50 % amplitude).

Recently, bio-based materials that are both environmental-friendly and highly functional were synthesized from various waste and biomass. Rice straw, a by-product of paddy production, is abundant lignocellulosic biomass with high cellulose content. The utilization of this natural resource for high functional material often meets with difficulties due to a large amount of lignin and silica present in the material matrix. While rice straw has been employed for biofuel production on pilot scale, its use for cellulose recovery has only been performed in laboratory-scale equipment. Here we show a simple process to effectively recover cellulose from rice straw on a pilot scale, after which the extracted cellulose was used for the preparation of aerogel. The alkali pretreatment removed the majority of lignin and silica, yielding semi-product with cellulose content of 73 %, then the bleaching step with hydrogen peroxide further eliminated colored impurities to increase the cellulose content to 90 %. The obtained cellulose was then employed to fabricate cellulose aerogel with low density, high surface area, and porous structure, which showed a good performance in the separation of oil and water, with the maximum capacity reaching 21.7 g/g. The process is a promising solution for converting rice straw into a more valuable product for water treatment on a larger scale.

Nanocellulose is one of the most valuable biomass-derived materials, possesses outstanding properties, and is widely used in numerous applications for biomedical fields, packaging, and environmental waste treatment. Rice straw is an abundant by-product from the rice industry and among cellulose-rich feedstocks. The pristine structural network of this raw material is complicated composing cellulose, hemicellulose, and lignin. Therefore, the pretreatment step is necessary to facilitate further stages in the biomass conversion process. The effect of such methods on the characteristics of nanocellulose products from rice straw has not been widely investigated in comparison with other types of biomass. This review summarized the common methods for rice straw pretreatment and the effects of distinct methods on the obtained nanocellulose. Alkaline pretreatment is considered as one of the most effective method for the extraction of cellulose from lignocellulosic complex. Based on a comprehensive summary, this review also shows that cellulose nanocrystals (CNCs) which is usually isolated by acid hydrolysis, has a high crystallinity index due to the removal of amorphous region. Cellulose nanofibrils (CNFs) is obtained by employing mechanical methods to reduce the particle size of cellulose fibers.

Aerogels from cellulose and its derivatives, especially cellulosic wastes, have been known as an excellent heat insulation material in steam generation, buildings, intelligent food packaging, fire-retardant clothing, and thermal protective equipment because of their lightweight properties, high stability, and extremely low thermal conductivities. Towards the scope of maximizing the bio-based resources utilization in day-to-day life, pineapple leaves (PLs) are converted into microfibrillated cellulose (MFC) fibers. PLs are first pretreated step by step with NaOH and NaOH/H2O2 solution to enrich cellulose content. This was followed by acid hydrolysis (H2SO4 40 wt%) and high-speed homogenization for MFC production. The obtained cellulose microfibers are further exploited to produce cost-effective, eco-friendly, and high-value engineering aerogels cross-linked by a common polyamide amine-epichlorohydrin (PAE) for the first time. The developed procedure is feasibly applied to mass production at a pilot-scale because of its simplicity, cost-effectiveness, and environmental friendliness. The resulting aerogels exhibit ultra-low density (below 30.0 g/cm3) and high porosity (above 98.0 %) along with high elasticity. Morphology analysis reveals that most of the pores within the aerogels are macroporous, and the diameter of fibers is around 2-3 µm. The heat conductivity of as-fabricated aerogels is in the range of 0.035-0.043 W/m?K, which is comparable to some heat insulation products such as glass wool (0.031-0.043 W/m?K), cellular glass (0.038-0.043 W/m?K), and mineral wool (0.034-0.045 W/m?K). The effects of cellulose and PAE contents on the morphology, physical, mechanical, and thermal behaviors of the synthesized aerogels are also investigated. The MFC aerogels from pineapple leaves are considered novel and promising candidates for bio-based heat insulation applications.

Coir (i.e., coconut fiber) is one of the popular agricultural waste products, especially in Vietnam, mostly discarded when copra and coconut water are taken, causing environmental pollution and waste of potential biomass. Various research has been done to reuse this resource as advanced materials. In this study, the NaOH-urea-H2O2 combination was utilized to make cellulose aerogel from coir fibers for the first time. Cellulose aerogel was synthesized by the sol-gel method combined with the freeze-drying technique. The properties of cellulose aerogel were determined, such as density, porosity, surface morphology analysis by FTIR, SEM, and thermal stability evaluation by TGA analysis. They exhibit low density (0.0099 - 0.0158 g/cm3), high porosity (98.96 - 99.35 vol%), and the methyl blue adsorption experiment shows cellulose aerogel's ability to treat color in water is significant.

In recent years, the presence of antibiotics in the environment has become a new threat to living organisms. Many advanced treatment technologies have been applied to treat antibiotic residues, especially in advanced oxidation processes. The traditional wastewater treatment process can be replaced by advanced oxidation (AOP), highly reactive free radicals, especially hydroxyl radicals (•OH) generated via Fenton (H2O2/Fe), peroxone (O3/H2O2), electrochemical oxidation, photochemical, serve as the main oxidant. In this study, antibiotic residues of Fluoroquinolones (Ofloxacin) are assessed in hospital wastewater after treatment and evaluated factors affecting peroxone oxidation process. The results show that the treatment efficiency is 72 % at initial OFL concentration of 20 µg.L-1, O3 (5 mg.L-1) flow rate is 1 L.min-1, initial H2O2 concentration of 50 mg.L-1 at pH 7. The OFL removal efficiency by peroxone process decreased when inorganic ions (CO32-, HCO3-, Cl-) were added at the concentration of 1mM. . The peroxone process is a promising technique to replace traditional technologies to treat antibiotic residues in wastewater.

In order to protect rescue personnel from the harmful effects of vapors during fire or chemical incidents, respirators are used as a mandatory requirement. The toxic gas adsorbent is a very important component of the respirator. In this study, carbon aerogel filter with a nonwoven fabric (polypropylene - PP, polyethylene terephthalate - PET) was fabricated by a sol-gel method incorporating thermal processes. Carbon nanomaterials are determined specific surface area by Brunauer-Emmett-Teller (BET), material surface shape and structure by Scanning Electron Microscopy (SEM), density. Experimentally evaluate the benzene vapor adsorption capacity of the filter plate at the initial benzene concentration of 5ppm, the temperature of 40 °C and the gas flow up to 30 L.min-1. The resulting carbon aerogel filter has a surface area of ??720.5–805.6 (m2/g), porosity (97.5-98.9 vol%) and pore size (6.1-22.2 Å). CAF-PP and CAF-PET filters have capacity equivalent adsorption, 2.3 and 2.4 mg/g. Breakthrough time for both materials is more than 30 min. CAF-PET filter has shown to be more suitable for use in respirator than CA-PP filter when have lower pressure loss. The results show that the carbon aerogel is suitable for use as an adsorbent for respirator.

Fly ash (FA), an abundant waste from thermal power plants in Vietnam, has been recycled 100 % into multi-functional aerogel composites for heat and sound insulation by the green fabrication developed in this study. The hollow structure of aerogel composites is created by sublimation of water in a mixture of FA and recycled polyethylene terephthalate (rPET) fibers bound by environmentally friendly adhesives including polyvinyl alcohol (PVA) and xanthan gum (XG). As result, the FA/rPET aerogel composites exhibit an exceedingly low density of 0.045 - 0.060 g/cm3 and high porosity of 94.81 - 97.02 %. The aerogel composites have a low thermal conductivity of 0.035 - 0.040 W/(m·K), a comparably high noise reduction coefficient (NRC) of 0.49, and a high working temperature of 220 °C. The prepared FA/rPET aerogel composites display the ability to slow down the burning in the presence of FA at 3.0 wt% with a burning rate of 1.0 mm/s and extinguish the flame only 30 s. The effect of FA content on the morphology, physical and mechanical properties as well as thermal conductivity, acoustic insulation, and slow-burning of the aerogel composites is also investigated comprehensively. The features of slow-burning aerogel composites from FA and rPET fibers such as lightweight, flexibility, thermal and sound insulation give them great potential in civil engineering towards a green approach and sustainable development.

Water pollution resulted from the discharge of the textile industry limits light penetration into the water, negatively affects the photosynthesis of aquatic organisms, and causes serious risks of cancer and genetic mutation for humans living near the emission site. The utilization of porous materials like aerogels to adsorb dye has been one of the effective methods for wastewater treatment. The fabrication of renewable materials from agricultural waste both to take advantage of its abundance and increase its value has gained research interest in recent years. In this research, this is the first time natural cellulose aerogel from coconut fibers (CFs) have successfully been developed by physically cross-linking cellulose with non-toxic binders including polyvinyl alcohol (PVA) and xanthan gum (XTG) in distilled water, followed by cost-effective freeze-drying to sublimate water and leave the hollow structure. The as-fabricated cellulose aerogel exhibits a tremendously low density (0.041 g/cm3) and high porosity (96.30 %). The aerogels are then tested for methylene blue (MB) adsorption in water to evaluate its applicability in the treatment of dye-contaminated water with varied investigated factors such as contact time, pH values, and MB initial concentrations. The MB adsorption process of the aerogels reaches equilibrium after 50 min and their adsorption isotherms follow the Freundlich model with an R-square value of 0.9453. It is worth noting that the highest adsorption capacity of the synthesized aerogels is up to 11.84 mg/g when the initial MB concentration is 25 mg/L at pH 7. The feasible procedure to synthesize recycled cellulose aerogels from CFs with green chemicals in this study has created good promise for dye adsorbents. About the potential economic benefits, the CFs are abundant agricultural wastes, easy pretreated processing involved in saving energy costs.

Each year in Vietnam, to operate the country's thermal power plants, it is necessary to utilize a large quantity of coal. The power plants then generate a large amount of coal fly ash (FA), which is a hazardous solid waste that can seriously affect the environment. There is an urgent need to develop appropriate solutions for treating or reusing the generated FA. In this study, the layout of coal-fired thermal power plants in Vietnam, as well as the country's coal use and FA emissions, are discussed. Research is reviewed on the potential applications of FA in Vietnam, along with related research from the past 20 y worldwide, and is found to demonstrate that the main application of FA is that of a geopolymer in construction, acting as a low-cost adsorbent that removes compounds, organic matter, emissions, metals, light aggregates, backfills, and auxiliary baselines, and synthesizes zeolites. On that basis, FA samples collected in the northern and southern regions of Vietnam were analyzed for their chemical compositions. The results determined that FA throughout Vietnam has the chemical composition, SiO2 + Al2O3 + Fe2O3 over 70 wt%. This is FA of classification F, according to TCVN 10302: 2014 (2014) and ASTM C618. This study concludes that the fly ash originating in Vietnam is suited to the production of porous, super-light materials with a high technical value, such as aerogels or aerogel composites. Such materials as these possess special properties such as a low density, high specific surface area or porosity, low thermal conductivity, sound insulation, low dielectric constant, low optical refractive index, or a high optical transmission capacity, elasticity, durability, or flexibility. The application of Vietnamese FA in the production of materials such as these is recommended by this paper, as a means of countering the environmental pollution problem of coal-fired thermal power plants and promoting the development of advanced materials in Vietnam.

Carbon aerogel is taken into account for a new material with many unique properties that can be applied in many different application fields. The properties of carbon aerogels are distributed across a wide range and are controlled by many conditions in the synthesis process. For each different application area, carbon aerogel is synthesized under different conditions to meet the required properties for materials such as: surface area, specific gravity, conductivity, pore size, etc. Therefore, the assessment of the quality of synthetic carbon aerogels will create a premise to guide them in appropriate fields. Besides, it is also possible to optimize the synthesis process to achieve materials of good quality, properties suitable for each specific requirement. The specific weight less than 0.5 g/cm3. Specific surface area from 633 to 800 m2/g. Pore size from 7 to 22 A With the properties of carbon aerogel materials synthesized, assess the adsorption capacity of carbon aerogel to treat heavy metals Fe, As and pesticides (Cypermethrin / DDT) in laboratory water samples and surface water samples taken from the rivers in the Cuu Long Delta. The results show that the ability to adsorb and process metals and pesticides is very good. Processing efficiency of iron and arsenic reaches 92-99%. Meanwhile, the ability to absorb plant protection drugs Cypermethrin / DDT also reached 95 - 99 %.

The Pinch technology is one of the most advanced methodologies for energy saving in processes and total sites based on thermodynamic principles. In ceramic industry, energy distribution in kiln is very complex. The pinch analysis was used to minimise energy levels for ceramic kiln during operation at Phuoc Du Long ceramic company in Vietnam. Using Pinch technology, it was possible to identify appropriate changes in the core process conditions that could have an impact on energy savings. After the heat and material balance was established, targets for energy saving could be set prior to the design of the heat exchanger network in ceramic kiln. The results showed that the efficiency of the heat exchanger in the flue heat exchanger network had been determined. This also indicated that at the optimisation conditions, the heat loss was at a minimum. The heat and material balance were established in ceramic kiln. From the basic heat and material balance inside the old type of ceramic kiln, the energy lost via flue gas emission and heat transfer was found to be about 600 kJ. The Pinch point at 820 °C was determined to give a chance for energy saving.

Utilising biomass for thermal generation purpose is one of the ways to reduce CO2 emissions. For that reason, the biomass gasification process is used to produce rich heating value fuel which is known as syngas. Because of the complicated nature of this field, the research should comprise both conducting experimental investigation on actual facilities and developing a numerical model. This study compared the affection of two kinds of gasification agents, the air and the air-steam mixture, on the composition of syngas and cumulative CO. The ratio of steam for the best quality of syngas was then determined. The two-dimensional Computational Fluid Dynamics (CFD) was developed for determining the suitable kinetics model. The parameters of geometry were taken from practical pilot plant gasifier. The validation process for this simulation was carried out by comparing the simulation data with experimental data which was measured by online gas analyser-TESTO 350XL. The results illustrate the influence of air-steam mixture on the composition of CO and H2 in syngas, H2/CO ratio, and the advantage of using the stream in gasification on both experimental and simulation results.

The aim of this study was to evaluate the oil and bioactive contents of grape waste by both conventional and microwave-assisted extraction (MAE) methods. Other controlled factors included the segment solvent used (n- hexane-methanol, n-hexane-ethanol), the solid/solvent ratios (1 : 5, 1 : 10, 1 : 20 g/mL) and in MAE, the microwave powers (40 W, 240 W and 440 W). The extracts were analysed for the contents of fatty oil, lipid hydroperoxide content (LP), total phenolic content (TPC), total flavonoid content (TFC), and antioxidant capacity. The optimal conditions for the grape oil recovery were at 240 W, using n-hexane-ethanol solvent, and the ratio of 1 : 10 by using the MAE method. At the same ratio conditions, the highest contents of LP and TPC were 0.032 mM (at 440 W) and 43.657 mg gallic acid (AG)/dry weight (at 240 W). At 440 W and ratio of 1: 10, TFC peaked the highest point at 37.862 mg quercetin/g dry weight. The results indicated that grape waste is a valuable input for a wide range of applications in nutraceutical and food industries, offering an additional economic by-product for the grape processing.