Science & Technology Development Journal - Engineering and Technology

Research on the reuse of alkali solution in rubber pretreatment process to minimize chemical costs

2020-07-06T23:38:24+00:00

Agricultural and forestry wastes are the popular renewable resources due to its price and efficiency. In recent decades, there are a lot of successful researches about bioethanol from lignocellulose to decrease the fossil fuels consumption. To produce bioethanol from lignocellulose materials, the prerequisite step is pretreatment step to remove lignin, to break the tight structure of lignin-cellulose-hemicellulose complex, to facilitate the contact between hydrolysis agent and cellulose. Alkaline pretreatment has been known as the most popular method. In this study, NaOH solution after the first pretreatment will be used again, adding a minimum amount of NaOH. The addition is calculated so that the total amount is reduced while maintaining the pretreatment efficiency. Analysis results showed that an aqueous solution of 2.0 wt.% NaOH can be used to pretreat the biomass for the first time in 24h, the first pretreatment allow the cellulose enrichment of raw materials from 41.2 % to 53%, in the second reused pretreatment, the addition give the same efficiency. The total amount of alkaline solution decreases 30.3% and the pure water decrease 41.2%, compared to the traditional method. The proposed method achieves the main goal: reduce significantly chemical costs, have a positive and practical meaning in contributing to solve the economic - technical problem of the second generation bioethanol’s production technology.

Preparation of activated red mud and its application for removal of hydrogen sulfide in air

2020-07-06T23:38:25+00:00

Red mud is a highly alkaline solid waste from the Bayer process for aluminum production. Red mud reservoirs are usually considered as a potential environmental risk. The treatment of red mud is costly due to the lack of an effective and economical treatment technology. On the other hand, the main components of red mud are Fe2O3, Al2O3, SiO2, and Na2O, which could be employed as a promising precursor for the preparation of various nanomaterials. In this study, we prepared activated red mud by thermal and acid treatment method and applied it for adsorption of H2S in air. The red mud was activated under different temperatures (i.e., 200, 400, 600, and 800 oC for 4 h), types of acid (i.e., H2SO4 and HCl), and acid concentrations (i.e., 0.5, 1.5, and 2.5 M). The produced materials were then applied for H2S removal in air with concentration of 90 – 110 mg/m3 using a fix-bed adsorption column test. Results showed that red mud activated at 800 oC and with 1.5 M H2SO4 solution had the highest adsorption capacity of 29.38 mg/g with an average removal efficiency of 80.2%. The effects of gas flow rate and initial H2S concentration were also investigated, and the highest removal capacity was achieved at an inlet concentration of 100 mg/m3 and flow rate of 1 L/min. Both Langmuir and Freundlich adsorption isotherms were employed for modelling the H2S adsorption by this material and the experimental result was more fitted with the Langmuir isotherm. The thermal desorption and recyclability test were also conducted for evaluating the practical application of activated red mud material and 200 oC was the suggested desorption temperature with 81.7% adsorption capacity recovery.

Developement of 3D printer for silicate-based materials

2020-07-06T23:48:59+00:00

3D printer and 3D printing technology are now considered as one of the key factor in the manufacturing industry. In the near future, we could envisage different application of 3D printing method in the sector of materials processing and production. In the sector of civil engineering, they existed somewhere some construction works developed with 3D printing technology. In this study, we aim to manufacture laboratory-scale printers with nozzles and extrusion feeding systems suitable for paste such as the case of clay-based materials of silicate industry. The movement system was encoded and controlled via the motherboard (Mach 3 controller software). Stepper motors and shaft drives were also implemented in the frame element of such printer. The feeding system was designed based on the extrusion method including cylinder and piston element. Based on that, sample size 200x300x300mm was available for operation testing. Concerning the performance of the instrument, we have obtained printed specimens with different geometric shapes with complexity. From the obtained result, we also discussion on the feasibility up scaling the study and developing a 3D printer for silicate based materials.

Extracting and determining components in the carotenoids colorant from pumpkin (Cucurpita pepo)

2020-07-06T23:46:59+00:00

In this paper, the extraction of carotenoids colorants from three types of pumpkin (Vam Rang (C. maxima), ho lo (C. moschata) and Japan pumpkin (Delica)) were investigated to scale up. With suitable conditions, the pumpkin powder should be extracted with alcohol 96^o with a solvent / material ratio of 12/1 mL/g at 50°C for 60 minutes. The content of carotenoids (7,5- 8 mg/mL) and the extraction efficiency of the color extract (88,37 mg/g) of ho lo pumpkin was the highest. The carotenoid concentration and extraction efficiency were determined by UV/Visible spectroscopy (432, 444 and 468 nm), and high performance liquid chromatography (the mobile phase condition isopropanol/MeOH:2/98, 450 nm. The results of the two methods were also suitable for each other. The results showed that the complex carotenoids were composition of 3 types compounds. In addition, more research is needed to enhance the durability of carotenoids.

Investigation of methylene blue adsorption capacity of porous chitosan particles

2020-07-06T23:53:03+00:00

Chitosan obtained from shrimp shells and SiO₂ nanoparticles obtained from rice husk ash were used to synthesize chitosan - SiO₂ composite materials. In order to obtain a porous chitosan adsorbent, the SiO₂ particles in the chitosan - SiO₂ composite material were removed with NaOH solution. With the orientation of applying adsorbent in wastewater treatment of textile industry, the ability of methylene blue adsorption of chitosan with porous structure has been investigated. Survey results show that chitosan has porous structure with good adsorption capacity of methylene blue. The adsorption capacity of materials depends on many factors such as: structure of particles; pH of adsorption medium and temperature. Adsorbent material is made of composite chitosan - SiO₂ with the ratio of chitosan/SiO₂ equal to 1/1 (w/w) with the best adsorption capacity. Materials with good adsorption capacity at pH = 6, at low pH, the adsorption capacity of the material is significantly reduced. Temperature has a great influence on the adsorption capacity of the material. The suitable temperature for adsorption of materials is 40 ^oC. With a higher temperature, the desorption process will be accelerated. This makes the adsorption capacity of the material decrease. The maximum methylene blue adsorption capacity of the material is determined about 7.25 mg/g after 40 minutes of adsorption time.

Thermal oxidation of carbon monoxide in air using various self-prepared catalysts

2020-07-07T00:01:34+00:00

Carbon monoxide (CO) is a very toxic pollutant emitted from wood fired boiler, which is widely used in small and medium enterprises in Vietnam. The treatment of CO containing flue gas faces many difficulties due to the inert property of CO and cannot be removed by traditional adsorption and absorption methods and one of the effective CO treatments is catalytic oxidation. Therefore, we aimed to prepare various catalysts on different carriers for treatment of CO in flue gas, including γ-Al₂O₃-based metal oxides (Co₃O₄/Al₂O₃, Cr₂O₃/Al₂O₃, and CuO/Al₂O₃), CuO–MnOx/OMS-2, and CuO-MnOx/zeolite. The CO removal tests were conducted in a continuous fixed bed reactor in laboratory scale with temperature range of 50 – 550 ^oC. The characteristics of catalytic materials were then determined by various methods such as Brunauer-Emmett-Teller measurement, X-ray diffraction, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. Results showed that CuO-MnOx/OMS-2 was the best catalyst with high removal efficiency of 98.41% at reactor temperature of 250 ^oC while gas outlet temperature of < 50 ^oC, proving the suitability of this material for practical treatment of CO in flue gas. The reaction follows Mars-Van-Krevelen mechanism with the presence of Cu²⁺-O^2--Mn⁴⁺ ↔ Cu⁺-o-Mn³⁺ + O₂ redox in the structure of the material. Moreover, the effect of environmental factors such as flow rate, inlet CO concentration, and catalysts amount on the CO removal efficiency were investigated and noted for designing and operation purposes. Concentration of outlet CO met well QCVN 19: 2009/BTNMT - National technical regulation on industrial emissions for dust and inorganic substances. Therefore, CuO-MnOx/OMS-2 catalyst material could be a potential catalyst for treatment of CO in flue gas of boiler.