Silica Extraction Research Articles

Sugarcane Bagasse as a Renewable Source of Silica to Synthesize Santa Barbara Amorphous-15 (SBA-15)

Sugarcane bagasse is an agricultural waste that is potentially used as natural silica resources. Natural silica claimed to be safe in handling, cheap and can be generate from cheap resource. In this study, Santa Barbara Amorphous-15 (SBA-15) was synthesized using sodium silicate that is extracted from Sugarcane bagasse ash (SCBA). Post treatment method using hydrochloric acid (HCl) was introduced during the silica extraction process to improve its purity. The result indicated that the amount of SiO2 present in the raw sugarcane bagasse ash was 53.10% while the silica composition in acid treatment sample was 88.13%. The FTIR pattern of extracted sodium silicate shows a similar spectrum with the commercial pattern of sodium silicate. While the Inductive Coupled Plasma (ICP) result shown that the concentration of silica in extracted sodium silicate was 4873ppm. Then the extracted sodium silicate produce was used as a silica precursor in the synthesis of mesoporous silica, Santa Barbara Amorphous-15 (SBA-15). The formation of SBA-15 was characterized using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The result indicated that the synthesis SBA-15 have present peaks 100, 110 and 200 which represent the hexagonal mesoporous material associated with p6mm symmetry.

Studies on Thermal Degradation Behavior of Siliceous Agriculture Waste (Rice Husk, Wheat Husk and Bagasse)

Abstract Various siliceous agriculture waste (SAW) such as rice husk, wheat husk and bagasse have been investigated to study their thermal degradation behavior using Thermogravimetric Analyzer (TGA) technique. The focus of this research is to conduct TGA of raw and acid treated (20% HCl & 1M H2SO4) SAW at heating rate 10°C/min in the atmosphere of nitrogen. The results were analyzed on the basis of thermograms and it was inferred that 24 hours soaking with 20% HCl prior to thermal degradation enhanced the percent weight loss. The process also improved the percentage of residual weight of SAW indicating the extraction of amorphous silica with increased purity. The effect of acid treatment was verified by determining chemical composition of SAW samples before and after soaking with 20% HCl. Proximate analysis, thermal degradation temperature ranges and percentage of residual weight at 800°C for each of rice husk, wheat husk and bagasse were also quantified to observe the thermal degradation behavior. XRF analysis was performed to observe the effect of acid treatment for extraction of pure silica.

Simultaneous utilization of soju industrial waste for silica production and its residue ash as effective cationic dye adsorbent

AbstractSoju industrial waste is an important biomass resource. The present study aimed to utilize soju industrial waste for silica extraction, and residual ash (RA) as a low cost adsorbent for the removal of methylene blue (MB) from aqueous solution. A high percentage of pure amorphous nanosilica was obtained from soju industrial waste ash by the acid dissolution-precipitation process. The synthesized nanosilica and the RA were characterized well using various techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), and field-emission electron microscopy with energy dispersive spectroscopy (EDS). The amorphous nature of nanosilica and its 99% purity were confirmed by XRD and EDS profiles, respectively. Transmission electron microscopy (TEM) micrographs show the nano range (14–18 nm) of synthesized silica. The adsorption capacity of RA was evaluated as a function of initial dye concentration, pH, and contact time. The sorption equilibrium data were modeled with isotherms; the Langmuir isotherm model fits well with maximum monolayer adsorption capacity of 232.5 mg/g at 30°C. The adsorption kinetics was best fitted with the pseudo-second-order model, suggesting that chemisorption plays a significant role in the adsorption process. The results showed that soju industrial waste is a potential waste for silica extraction and that its byproducts are effective adsorbents.

Extraction and physical characterization of amorphous silica made from corn cob ash at variable pH conditions via sol gel processing

Herein, we disclose a novel approach for the synthesis of nano-silica using corn cob ash (CCA). Also, we identify that silica is amorphous at pH 7 and crystalline at pH 10 at the critical salt concentration for monovalent NaOH. A zeta potential study was used to characterize the surface charge of nanoparticles. The silica nanoparticles were characterized by SEM-EDS, XRD, FTIR, TEM and XRD confirmed the crystalline nature and TEM images showed spherical silica nanoparticles. Brunauer–Emmett–Teller, cation exchange capacity, and N2 analyses showed excellent support material for catalysis at pH 7. The CCA-mediated synthesized particles showed excellent stability at pH 7.

Extraction, characterization, and catalytic potential of amorphous silica from corn cobs by sol-gel method

A simple method based on alkaline extraction followed by acid precipitation can be used to form silica aquagel from corn cob ash (CCA). SEM-EDS analysis confirmed the high silicon and oxygen content of the extracted silica. XRD diffraction indicated that the obtained product was amorphous silica, while FTIR data demonstrated the presence of siloxane and silanol groups. TEM images revealed the silica to be amorphous, and have an agglomeration form with an average diameter of ∼50nm. CCA-extracted silica (0.1g/20ml) was observed to have good catalytic potential with 100% removal of 12×10−4M methylene blue.

Silica Extraction from Rice Husk by Warm Water Pretreatment

Rice husk (RH) has high content of silica. In this study, the extraction of silica from rice husk while maintaining the organics was carried out by warm water pre-treatment followed by alkaline hydrolysis. RH powder was treated with water at 50oC and 100oC prior to treatment with 1 M of sodium hydroxide (NaOH) aqueous solution at 50oC. The filtrate from the alkaline hydrolysis was then further reacted with 1 M of hydrochloric acid (HCl) for silica extraction. The samples obtained after each stage of the treatments were carefully characterized and their chemical compositions were determined. The morphology of the untreated and treated RH powder was analyzed by Scanning Electron Microscopy (SEM). Estimation on the silica content was made by Energy Dispersive X-ray (EDX). The functional group present in untreated and treated RH were determined by Fourier Transform Infrared Spectroscopy (FTIR). The percentage of silica extracted from ΔH2O/NaOH-RH filtrate was higher (18.9%) than from H2O/NaOH-RH filtrate (12.6%). FTIR spectroscopy data indicated the disappearance of siloxane group when RH was treated with hot water and warm water followed by alkaline hydrolysis. The selected extraction method has successfully recovered silica at high yield but at the same time maintaining the organic compounds in the rice husk.

Effects of Hydrothermal Duration on Synthesized Zeolite Rice Husk Particles

Zeolite particles were synthesized through in-situ extraction of silica from rice husk ash without seeding method in the absence of organic template by a static hydrothermal condition at various duration for 8, 12, and 24h. The effect amorphous silica content on hydrothermal duration of synthesis products was evaluated with X-ray diffraction (XRD), and field emission microscopy (FESEM). The present of zeolite Y without seeding method via XRD analysis show a mixture of zeolite A, Y and P. The transformation of amorphous rice husk particle was increased gradually with the increased of hydrothermal reaction. The FESEM images showed agglomerated cubic-shaped morphology of the powders with increase in crystallization reaction. .

Determination of Lead and Cadmium in Water and Pharmaceutical Products by Inductively Coupled Plasma Optical Emission Spectrometry with Preconcentration by Thiourea Immobilized Silica

Thiourea immobilized silica was prepared and applied to the separation and preconcentration of trace lead and cadmium in environmental water and pharmaceutical products followed by inductively coupled plasma optical emission spectrometry (ICP-OES) determination. Factors affecting thiourea immobilized silica extraction were investigated in detail. Lead and cadmium were selectively retained by the modified material, and then eluted quantitatively with 1.0 mol L−1 HNO3 and 1.0 mol L−1 HCl plus 1.0 mol L−1 HNO3, respectively. With enrichment factors of 20, the detection limits of lead and cadmium were 6.36 and 0.093 µg L−1, and the relative standard deviations were 7.5% for lead (n = 11 at 0.5 μg mL−1) and 1.7% for cadmium (n = 11 at = 0.05 μg mL−1). The method was successfully applied for the determination of lead and cadmium in environmental water and pharmaceutical products with satisfactory results. In order to validate the developed procedure, a GSB 07-1185-2000 certified reference environmental water was analyzed and the results were in good agreement with the certified value.

Optimization of rice husk pretreatment for energy production

One of the most widely cultivated crops in the world is rice, leading to millions of tons of rice husks (also known as rice hulls or chaffs). The large amount of this lignocellulosic biowaste has resulted in an extensive search for its utilization. One such usage of this waste is for the production of electricity, such as in combined heat and power or gasification units. However, one of the disadvantages of using rice husks is their high silica content which produces large amounts of undesirable ash upon combustion leading to operation problems such as slagging and clogging. Here, alkali pretreatment for the extraction of silica in the form of sodium silicate has been studied using response surface methodology (RSM) and Analysis of Variance (ANOVA). Three independent variables namely reaction temperature, duration, and alkali concentration were considered using a Box–Behnken design (BBD). The operating conditions were optimized under different scenarios. The first optimization focused on the two goals of high ash removal and high solid yield while the next optimization rounds added the criteria of low NaOH usage and robust design (using propagation of error (POE)). The final treated rice husks can therefore be more suitably used as feed for thermal and/or electric units. The developed empirical predictive models were successfully validated through additional experimentation.

Optimising the extraction of amorphous silica by NaOH from soils of temperate-humid climate

This study focuses on optimising amorphous silica extraction from soils by using NaOH. Based on the results of this test series, a method for quantifying amorphous silica in soils from temperate-humid climate is proposed. All tests were carried out on materials of known composition (well-defined samples of feldspar, clay minerals, bio-opal, silica gel, and mixtures of these components) and on soil samples, to determine the optimum set of conditions, in terms of solid : solution ratio, temperature and extraction time, for dissolving amorphous silica without considerably attacking other solid silicon compounds. A solution of 0.2 m NaOH almost completely extracted amorphous silica, and when applied at room temperature and a solid : solution ratio of 1 : 400, only slightly broke down crystalline Si compounds. The predictable and reproducible underestimation was considered more acceptable than the variable partial dissolution of silicates that occurs during extraction at higher temperatures. We therefore recommend using this method on soils from temperate-humid climate to estimate the amorphous Si fraction.

Agricultural waste as a source for the production of silica nanoparticles

The major interest of the paper deals with the extraction of silica from four natural sources such as rice husk, bamboo leaves, sugarcane bagasse and groundnut shell. These waste materials in large quantities can create a serious environmental problem. Hence, there is a need to adopt proper strategy to reduce the waste. In the present investigation, all the waste materials are subjected to moisture removal in a hot plate and sintered at 900°C for 7h. The sintered powder was treated with 1M NaOH to form sodium silicate and then with 6M H2SO4 to precipitate silica. The prepared silica powders were characterized by FT-IR, XRD and SEM-EDAX analysis. The silica recovered from different sources was found to vary between 52% and 78%. Magnesium substituted silica was formed from the groundnut waste and further treatment is required to precipitate silica.

Preparation of Silica by Alkaline-Heating and Precipitation Method from Corn Straw Ash

The preparation of silica by an alkaline-heating and precipitation method from corn straw ash (CSA) obtained from a biomass power plant was the focus of this study. Sodium hydroxide was used as the silica extraction reagent, and H2SO4 was the precipitator. The concentration of sodium hydroxide solution was confirmed to have a significant influence on the production of sodium silicate from CSA. The optimum technological parameters for the preparation of sodium silicate and the suitable parameters for the preparation of silica were obtained by experiments and analysis. Fourier transform infrared spectroscopy (FT-IR) was used for confirming that the as-obtained silica has characteristic IR absorption peaks of typical hydrated silicon dioxide. The microstructures of the as-obtained silica products were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Comparison using HG/T3061 (2009) standards, and the characteristics of silica products were used to estimate whether the as-obtained silica products reached market requirements. The results show that the silica products are superior to the standard requirements and have a large market potential.

The preparation of a green shape-stabilized composite phase change material of polyethylene glycol/SiO2 with enhanced thermal performance based on oil shale ash via temperature-assisted sol–gel method

A novel polyethylene glycol (PEG)/SiO2 shape-stabilized composite phase change material (ss-CPCM) was prepared with the ‘hazardous waste’ oil shale ash. In this composite, PEG serves as the phase change material for thermal energy storage and SiO2 acts as the carrier matrix to provide structural strength and prevent the leakage of melted PEG. The calcination-alkali leaching method was applied to prepare the sodium silicate solution with the ash. When the calcination temperature, calcination time, sodium hydroxide concentration, reaction time and liquid/solid ratio were 900°C, 60min, 20wt%, 4h, and 4mL/g, respectively, the silica extraction efficiency could reach 60.36%. Then the PEG/SiO2 ss-CPCM was prepared with sodium silicate solution as the precursor via the temperature-assisted sol–gel method without any co-solvent or surfactant. Various characterization techniques were adopted to study the structures and properties of the prepared PEG/SiO2 ss-CPCM. SEM, FT-IR, and XRD results indicated that PEG was well encapsulated and that no chemical change took place during the phase change process. TGA results showed that the composite presented an excellent thermal stability. DSC analysis results indicated that the composite had considerably high phase change enthalpy, encapsulation ratio, encapsulation efficiency and thermal storage capability. Moreover, the supercooling extent, melting and solidifying time of the composite were respectively 22.3%, 26.5% and 22.6% less than those of pristine PEG. Based on the element analysis, there are no safety hazards for the prepared ss-CPCM to be seen as a potential candidate for thermal energy storage applications in building envelopes.

The Characteristic of Synthesized Zeolite Rice Husk Particles via Different Routes

Zeolite particles were synthesized through in-situ extraction of silica from rice husk ash without seeding method in the absence of organic template by a static hydrothermal condition at 100oC/24h at varied ageing 8-24h. The effect of amorphous silica content on ageing time of synthesis products was evaluated with X-ray diffraction (XRD), Fourier transform infrared (FTIR) and field emission microscopy (FESEM). The present of zeolite Y without seeding method by XRD analysis show a mixture of zeolite A, Y and P. The transformation of amorphous rice husk particle gradually increased as early at 8 hours in ageing and increased with increase in ageing reaction. The vibration bands at around 974 cm-1 indicated Si-OH vibrations of the surface silanols, which is the characteristic of mesoporous silica. The FESEM images showed cubic-shaped morphology of the powders increased with increase in ageing reaction.

Life-cycle assessment of multi-crystalline photovoltaic (PV) systems in China

This study performs a life-cycle assessment for a photovoltaic (PV) system with multi-crystalline silicon (multi-Si) modules in China. It considers the primary energy demand, energy payback time (EPBT), and environmental impacts, such as global warming potential and eutrophication, over the entire life cycle of the PV system, including the upstream process, ranging from silica extraction to the multi-Si purification, the midstream process, involving crystalline silicon ingot growth and wafering; and the downstream process, consisting of cell and module fabrication. The data were collected with recommendations provided by the ISO norms and acquired from typical PV companies in China. The results show that the most critical phase of life cycle of Chinese PV system was the transformation of metallic silicon into solar silicon, which was characterized by high electricity consumption, representing most of the environmental impact. The other electricity generation systems were compared to PV. Considering that Chinese electricity is mainly produced by coal-fired power plants, the installation of multi-Si PV systems is recommended over exporting them from China. Furthermore, being higher solar radiation areas, areas in western China, such as the Tibet Autonomous Region, northeastern Qinghai, and the western borders of Gansu, are best suited for the installation of the PV systems even if the long distance of transportation. Finally, recommendations were provided with respect to the sustainable development of the Chinese PV industry and environmental protection.

Co-Producing Active Carbons and Sodium Silicate from Pyrolyzed Rice Husk by CO<sub>2</sub> Activation Coupled with NaOH Solution Boiling

Active carbon and sodium silicate were produced simultaneously from pyrolyzed rice husk (PRH) by CO2 activation coupled with NaOH solution boiling. Doehlert matrix and Derringer's desirability function were applied to optimizing the boiling conditions to achieve a large specific surface area, a high silica extraction and low alkali consumption. In terms of this purpose, the optimum condition was determined as boiling CO2-activated char with 1mol/L NaOH solution at a liquid/solid ratio of 9.7 mL/g. Under this condition, the modulus of the sodium silicate and the specific surface area (SSA) of the active carbon were 2.62 and 897 m2/g, respectively. The values both reached their respective commercial levels. The pretreatment of the PRH with CO2 activation can markedly increase the SSA of active carbons.

Methanol Dehydration to Dimethyl Ether over Silica Derived from Rice Husk as the Component-Based Catalysts

Dimethyl Ether (DME) an alternative fuel was synthesized by methanol dehydration over the silica-based catalysts. Silica extracted from both rice husk (A) and rice-husk ash (B) was used as the precursors for preparing the catalysts. The SiO2/Al2O3 and the SAPO catalysts prepared from that silica were analyzed using X-ray diffraction (XRD), N2 adsorption (BET surface area), X-ray fluorescence (XRF), NH3 temperature-programmed desorption (NH3-TPD), and thermal gravimetric analysis (TGA). The effects of reaction temperature on the methanol selectivity and conversion to dimethyl ether were investigated. The methanol dehydration reactions were carried out in a packed-bed reactor at the reaction temperature of 250-350°C. DME was the major product and formed with selectivity of 57% over SAPO-B. An increasing of the reaction temperatures resulted in the enhancing of methanol conversion. The highest methanol conversion of 93% was achieved at 325°C. The method of silica extraction had an effect on the selectivity to DME due to the higher BET surface area.

Método de extração de sílica da casca do arroz

A influência dos ácidos cítrico, acético e oxálico na extração da sílica a partir da casca do arroz foi estudada. As condições experimentais da extração, como pressão e concentração ácida, também foram estudadas. De acordo com o tamanho dos poros pela adsorção de N2, conforme método BET, foram classificadas como mesoporosa. Comparações entre diferentes tipos de ácidos utilizados foram realizadas pela área de superfície específica da sílica obtida.O ácido que apresentou melhor desempenho foi o acético, resultando em área de superfície específica 271 m²/g; o ácido cítrico apresentou o melhor resultado de pureza, 99,96%.

Evaluation of methods that subdue the effects of polymerase chain reaction inhibitors in the study of ancient and degraded DNA

This study evaluated techniques that can potentially decrease time, cost, and labor in eliminating, circumventing, and/or inactivating as many polymerase chain reaction (PCR) inhibitors as possible while preserving DNA yield. In order to further explore the role of PCR inhibitors in ancient DNA (aDNA) studies, 140 DNA extractions were conducted on 112 Pacific salmonid vertebrae recovered from two archaeological sites located at Dionisio Point on Galiano Island, in southwestern British Columbia, Canada. These DNA extracts and their dilutions at 1:10 and 1:50 were screened for the presence of a 189 base pair (bp) portion of the 12S mitochondrial gene that is used for species identification of Pacific salmonids and other fish. These extracts and their dilutions were also screened for the presence of PCR inhibitors that can cause negative results for amplification of salmonid mtDNA. Repeat silica extraction was conducted on the full concentration extracts until: (1) they either produced a positive result in the salmonid mtDNA reaction, or (2) were deemed to be free of inhibition, but failed to amplify in the salmonid mtDNA reaction. In the latter case, the samples were concluded to not contain sufficient salmonid mtDNA to permit PCR amplification. In obtaining positive salmonid species identification, repeat silica purified extracts (81/133 successes) statistically outperformed dilutions at 1:10 (55/140, p=0.0018), 1:50 (63/140, p=0.0312), as well as across all dilutions combined (118/280, p=0.0025). We also explored the efficacy of EGTA as a decalcifying agent as compared to EDTA, which is commonly employed in aDNA studies. The only extracts that amplified at full concentration (6/140, 4.3%) were those in which EGTA decalcification was used. However, when diluted there was no statistical difference in the success of obtaining positive species identification from bone decalcified with EGTA or EDTA (1:10 and 1:50 dilutions, p=0.7891 and p> 0.9999 respectively). From the results of this study, we recommend that aDNA researchers employ greater flexibility in their methodologies as well as be cognizant of the role that PCR inhibitors may play in their investigations.

Eco-Friendly Synthesis of Nanozeolite NaA from Rice Husk Ash and its Efficiency in Removing Ammonium Ions

The eco-friendly synthesis of nanozeolite need to be developed in order to minimize the consumption of unwanted excess extracted solutions or solvents and maximize the utilization of beneficial wastes as its raw materials. Thus, the synthesis of nanozeolite NaA from rice husk ash (RHA) without extraction of silica from RHA and without organic template has been successfully achieved. Nanozeolite NaA was synthesized from rice husk ash (RHA) via this main step: aging the aluminosilicate suspension (3.190 Na2O: Al2O3: 1.4SiO2:235.07H2O) for 3 days at room temperature with agitation rate of 150 rpm followed by heating at 55 °C for 18 hours. The nanozeolite NaA was confirmed by XRD, FTIR, FESEM and particle size distribution analysis where the highest particle size was in the range of 100 to 400 nm. Its efficiency in removing ammonium ions in aqueous solution was found to be better than that of microsized zeolite NaA thus proved that the lower particle sizes of zeolite NaA (nanosize) tended to have higher adsorption sites and higher exchange capacity.