Production and Optimization of Bio-Based Silica Nanoparticle from Teff Straw (Eragrostis tef) Using RSM-Based Modeling, Characterization Aspects, and Adsorption Efficacy of Methyl Orange Dye

The brown teff straw was utilized in this study to produce silica using the sol-gel technique. After pretreatment, the raw material of brown teff straw was characterized. The data were analyzed using the central composite design and response surface technique, and four independent parameters, namely, temperature, NaOH concentration, rotational speed, and extraction time, were evaluated for process optimization. Before extracting silica with an alkaline solution, the silica content in the ash was determined using an AAS spectrometer. The silica content of teff straw ash is around 92.89%. The ash was treated with NaOH solution in the concentrations range of 1 M to 3 M (0.5 M interval). The extraction time varied at intervals of 55, 70, 85, 100, and 115 minutes. Temperatures were changed using magnetic stirrer equipment in the range of 80°C to 100°C (5°C interval). At 350 rpm, 400 rpm, 450 rpm, 500 rpm, and 550 rpm, the rotating speed was adjusted. The best extraction conditions for amorphous silica were 1.50 M NaOH, 109.99 min, 94.98°C, and a rotating speed of 499.57 rpm, with a maximum yield of 85.85%. XRD and FTIR analyses were used to assess the physicochemical characteristics of the extracted silica. The aqueous solutions of methyl orange were used to test the adsorption efficiency of silica. The percent of removal efficiency for methyl orange was 90.48%.

Effects of source location on the pozolannic properties of Rice Husk Ash (Rha) and strength properties of concrete

This paper presents the effects of variability in the chemical and elemental composition of Rice Husk Ash (RHA) sourced from four (4) different locations on Tensile Properties of Concrete. RHA is an agricultural waste gotten from rice mills after removal of rice paddy for food and burnt in open air or under controlled processes. RHA is found to be pozzolanic and can be used to partially replace cement to enhance the strength and quality of concrete. The different sources where RHA was gotten are; Ogoja, Abakaliki, Adani and Adikpo in Nigeria. It is discovered that the pozolanic properties of RHA varies based on their source location. Samples from Ogoja where found to have the highest pozzolanic properties followed by Abakaliki, Adani, and Adikpo, their silica content was found to be 84.55, 76.3, 70.12, 70.11, respectively. RHA was used to replace cement in concrete at 5, 10,15,20,25 and 30%. The compressive strength was determined and the values are as follows; And the compressive strength values at 28 days was found to be in the range of 37-42N/mm2 at 5%RHA, 35-39.5N/mm2 at 10%RHA, 30-34.5N/mm2 at 15%RHA, 27-29N/mm2 at 20%RHA, 22-25.6N/mm2 at 25% RHA and 21-24N/mm2 at 30% RHA compared to the controlled sample with a strength value of 42.64N/mm2. Cylindrical columns concrete of size 100mm diameter by 200mm long were moulded and stored in water for 28 days before testing for tensile splitting strength. The values determined from the split tensile test are as follows; 2.1-3.1N/mm2 at 5%RHA, 2.1-2.5N/mm2 at 10% RHA, 1.8-2.10 N/mm2 at 15% RHA, 1.2-1.7 N/mm2 at 20%RHA, 1.1-1.3 N/mm2 at 25% RHA and 0.62-0.9 N/mm2 at 30% RHA while the results of the controlled sample is 3.1 N/mm2.From the results above it can be deduced that source location influences the chemical properties of RHA strength characteristics of the Concrete with RHA as partial replacement.

Characteristics of Smoldering on Moist Rice Husk for Silica Production

In order to assess the possibility of silica production via smoldering of moist rice husk, experiments of washed (moist) rice husk (7 kg with moisture content of 51%) in a newly designed smoldering apparatus was performed. The temperature inside the fuel bed during smoldering was recorded, and characteristics of ash were analyzed. Results showed that the highest temperature in the middle of the naturally piled fuel bed was about 560.0 °C, lower than those in most of combustors. Some volatiles from the lower part of the fuel bed adhere to its upper ash during piled smoldering. Silica content and specific surface area of ash from smoldering of washed (moist) rice husk were 86.4% and 84.9 m2/g, respectively. Compared to our experiments, they are close to smoldering of unwashed rice husk (89.0%, 67.7 m2/g); different from muffle furnace burning (600 °C, 2 h) of washed (93.4%, 164.9 m2/g) and un-washed (90.2%, 45.7 m2/g) rice husk. The specific surface area is higher than those from most industrial methods (from 11.4 to 39.3 m2/g). After some improvements, the smoldering process has great potential in mass product of high quality silica directly from moist rice husk.

Lightweight Structural Concrete

Using of Lightweight concrete (LWC) amounts to a lower cost and a better thermal performance due to its unique properties and light density. The main disadvantage in using lightweight concrete is that its mechanical properties are relatively poor. An effective method to improve the mechanical properties of lightweight concrete is using a dosage of nano-silica in the concrete mix. The gained enhancement of mechanical properties promotes a more serious discussion of structural applications of lightweight concrete. There exists an optimum dosage of nano-silica by which the mechanical properties enhancement is maximized. Increasing the nano-silica content beyond the optimum dosage degrades the mechanical properties. However, a fixed optimum dosage is not agreed upon in literature. This paper investigates the optimum dosage of NS to enhance the mechanical properties and microstructure of a lightweight concrete made with lightweight expanded clay aggregates (LECA). The results concluded that a dosage of 0.75% of nano-silica is optimum for the studied lightweight concrete mixes.

Lanskap Budaya Pacitan dan Korelasinya dengan Sebaran Hunian, Artefak, dan Bahan Baku di Kawasan Gunung Sewu

Abstract, Pacitan Cultural Landscape and Correlation with The Distribution of Occupation, Artifacts, and Raw Materials in The Gunung Sewu Area. The results of archaeological research in the Gunung Sewu area provide an overview of the cultural landscape of space and time. During the Pleistocene, paleolithic remains were scattered mainly in the Baksoko watershed, Pacitan, and the Oyo River watershed, Gunungkidul. Traces of the cultural heritage of the Gunung Sewu area that last hundreds of thousands of years show a shift in choosing a place to work. An area is selected for activities based on the availability of basic human needs, both food sources (flora-fauna) and raw materials for making equipment. The need for raw materials equipment is an essential factor in describing the cultural landscape map because the choice of location as an activity is reflected in the human mind at that time. Applying paleolithic technology to Pacitan culture and neolithic technology generally uses rock materials that are easy to flake and chip. Therefore, selecting rock material with high hardness (silica content) will determine its sharpness. To reconstruct the cultural landscape in Pacitan in the dimensions of space and time, this aims to explain based on the hypothesis that if a culture is created in a particular natural environment, then the activity will occupy a particular natural environment. The approach used is landscape archeology. Based on this, it can be reconstructed that there are differences in stone raw materials for tool making between the upstream and downstream areas of the river with different technologies. In addition, there was a shift in an occupation that was initially centered around rivers during the Pleistocene, then shifted to karst hills in caves or niches during the Early Holocene. Abstrak. Hasil penelitian arkeologi di Kawasan Gunung Sewu memberikan gambaran lanskap budaya ruang dan waktu. Pada kala Pleistosen tersebar tinggalan paleolitik, terutama di Daerah Aliran Sungai (DAS) Kali Baksoko, Kabupaten Pacitan dan DAS Kali Oyo, Kabupaten Gunungkidul hingga tinggalan neolitik kala Holosen di Ngrijangan lengkap ditemukan di kawasan Gunung Sewu. Jejak tinggalan budaya Kawasan Gunung Sewu tersebut berlangsung ratusan ribu tahun yang menunjukkan adanya pergeseran dalam memilih tempat mereka beraktivitas. Suatu daerah dipilih untuk beraktivitas didasarkan pada tersedianya kebutuhan pokok manusia, baik sumber makanan (flora-fauna) maupun bahan baku untuk pembuatan peralatan. Kebutuhan bahan baku untuk peralatan merupakan faktor penting dalam menggambarkan peta lanskap budaya karena pilihan lokasi untuk beraktivitas tecermin bagaimana alam pikiran manusia pada waktu itu. Penerapan teknologi paleolitik pada budaya Pacitanian dan teknologi neolitik umumnya memakai bahan batuan yang mudah diserpih dan dipangkas. Oleh karena itu, pilihan material batuan dengan kekerasan tinggi (kandungan silikaan) sangat menentukan ketajamannya. Untuk merekonstruksi lanskap budaya di Pacitan dalam dimensi ruang dan waktu ini bertujuan menjelaskan yang didasarkan suatu hipotesis apabila suatu budaya tercipta pada lingkungan alam tertentu, Dengan demikian, suatu aktivitas akan menempati lingkungan alam tertentu. Pendekatan yang digunakan adalah arkeologi lanskap. Berdasarkan hal tersebut, dapat direkonstruksi adanya perbedaan bahan baku batu untuk pembuatan alat antara daerah hulu dengan ilir sungai dengan teknologi yang berbeda. Selain itu, terjadi pergeseran hunian, pada awalnya berpusat di sekitar sungai pada masa Pleistosen, kemudian bergeser ke perbukitan karst di gua atau ceruk pada awal Holosen.

Proton-conducting Organic-inorganic Sulfo-containing Membranes for Fuel Cell

Cross-linked organiс-inorganic sulfo-containing membranes of various compositions based on acrylic monomers (acrylonitrile, acrylic acid, 3-sulfopropylacrylate potassium salt, ethylene glycol diacrylate) and sol-gel systems of tetraethoxysilane have been developed. Synthesis of the polymer matrix was carried out by UV-initiated polymerization of the monomer mixture and the inorganic component was formed in situ while conducting the sol-gel process of the precursor. FTIR, SEM, EDS, DMA, impedance spectroscopy were used to characterize the synthesized materials. The influence of inorganic component content on the properties of the membranes was investigated. DMA results show that an increase in silica content leads to a decrease in packing density and an increase in structural heterogeneity in sulfo-containing polyacrylate/silica membranes. The highest values of proton conductivity 1.12 ꞏ 10−2 Sm/cm at 60 °C were found in membranes containing 3 wt.%. of the added sol-gel system. Further increase of silica content does not increase the proton conductivity of the membranes. The proton transfer activation energies in the membranes were calculated from the temperature dependence of proton conductivity. The obtained cross-linked sulfo-containing organic-inorganic materials can be used for the development of proton-conducting membranes for fuel cells.

RESEARCH OF CONCRETE OF REINFORCED CONCRETE SLEEPERS, WHICH DECIDED DAMAGE DURING OPERATION

Purpose. On the railways of Ukraine in some areas there is an intensive premature exit sleepers due to the formation of defects that can affect the safety of trains and cause significant material losses due to a single replacement of a significant number of sleepers. The purpose of the study is to establish the causes of damage reinforced concrete sleepers on a characteristic section of the railway with their intense premature exit. Methodology. The condition of reinforced concrete sleepers of SB3 type under unlined substrate fastenings on 324-332 km of the pair track of the Odnorobivka-Bukine section of the Southern Railway was studied, where since 2007 their intensive output was observed due to defects. Findings. It is established that for 15 years of operation, as 236.3 million tons were put into operation, about 2.8 % of sleepers were replaced due to defects (44 pieces per 1 km of track). Typical defects (damages), due to which the sleepers were removed from the track, were mainly 13.2 and 13.2 according to the classification of CP-0150 – cracks and fractures of sleepers, including ones with crushing concrete. These defects were preceded by the formation of a network of thin cracks on the visible surfaces of sleepers. 3 sleepers with an initial compressive strength of 68…77 MPa produced by the Korosten Reinforced Concrete Sleeper Plant and the Gnivan Special Reinforced Concrete Plant, removed from the track due to characteristic defects, were selected and investigated. Samples were selected from the sleepers, with the help of which there was determined the final strength of concrete and microscopic examinations, including luminescence flaw detection method, were performed. It was found that the network of cracks in sleepers is spatial, mostly developed mostly beneath their top edge, the least developed above the bottom edge, and causes a decrease in compressive strength of concrete by 47…72 %. It is noted that the destruction of concrete during loading occurred behind these cracks. On the inner surfaces of the cracks there are individual grains of aggregates, which have signs of active silica content, that together with the nature of the cracks may indicate that the cause of their formation is corrosion of concrete from the interaction of cement alkali with reactive aggregates. On the surfaces of the cracks in the lower part of the sleepers leaching products were found, apparently leached by electro migration, which may indicate that corrosion processes were promoted by leakage currents on electrified DC tracks. Originality Thus, in the study area, the main cause of defects, which caused the replacement of the sleepers – was the corrosion of concrete due to the interaction of cement alkali with reactive aggregates, promoted by leakage currents, as well as a small diagram of sleepers and the use of unlined anchor intermediate rail fasteners. Practical value. The results of the study allow to establish the causes of cracks and other damage in reinforced concrete sleepers during operation and, in turn, reduce the losses of fasteners manufacturers and sleepers from defects and complaints, optimize the total cost of track repairs and subsequent track maintenance due to rational purpose of track construction, reduction of damage and replacement of sleepers during track operation.

Potential uses of the lesser-known tree: Timo (Timonius sericeus (Desf) K. Schum) from Timor Island, East Nusa Tenggara based on its chemical wood properties and calorific value

This study determined the chemical properties and calorific value of Timo (Timoneus sericeus) wood originated from Reknamo village, Timor Island, East Nusa Tenggara. Timo is a potential wood that belongs to the Rubiaceae family, categorised as the lesser known tree. Its basic wood properties have not been thoroughly scientifically investigated. The chemical wood analyses were carried out at the laboratory of chemical forest products in the Forest Products Research and Development Center, Bogor. The Testing methods were according to the ASTM and TAPPI standard, included the content of extractive solubility (in cold water, hot water, benzene-alcohol, and in 1% NaOH), cellulose, pentose, lignin, ash, and silica. The calorific value was measured by the calorimeter. The result showed that the cellulose, pentose, and extractive solubility contents of Timo wood were high; the lignin and ash contents were moderate; the silica content was low; the calorific value was high (4400 cal/g). Based on the results of chemical wood analyses and calorific value, Timo wood is qualified for construction and wood energy; while it is not recommended for pulp and bioethanol.

Utilizing Pyrolytic Biomass Products for Rubber Reinforcement: Effect of the Silica Content in Biomass Feed Stocks

Biochar has been exploited as a substitution of carbon black in the rubber industry and various biochars exhibit diverse reinforcing abilities due to the different compositions. This work aims at studying the effect of silica on the modification process and reinforcing performance through the comparison of three biochars with different contents of silica, pyrolytic rice husks (PRH, 34 wt%), pyrolytic bamboos (PB, 7 wt%) and pyrolytic corn cobs (PC, 0.4 wt%). The results reveal that PRH requires higher rotational speed (300 min–1) than PB (200 min–1) and PC (200 min–1) to achieve similar particle sizes during the ball milling process because of the aggregations of higher silica content. Meanwhile, silica-rich pyrolytic biomass exhibits enhanced reinforcement on mechanical properties and thermal stability of rubber, and the elongation at break of vulcanizates continues to improve with increasing silica contents. Combined with the energy consumption and reinforcement, biochar containing a little amount of silica is more suitable to be widely used as bio-filler in rubber industry. This work should serve as a valuable reference to select appropriate biochar for the production of bio-fillers with high reinforcement.