Types Of Silica Gel Research Articles

Systematic screening and evaluation for an optimal adsorbent in a facade-integrated adsorption-based solar cooling system for high-rise buildings

Solar-powered adsorption chillers are a climate-friendly solution for building cooling, but costs and space requirements limit their widespread adoption. Recently developed adsorption cooling facade systems (ACFS) save installation space and further reduce CO2 emissions. The performance of ACFS depends on the implemented adsorbent. To achieve low costs and high performance of ACFS, this study systematically screened and scored adsorbents using the analytic hierarchy process (AHP) method, focusing on price, stability, driving temperature and adsorption capacity. This method narrowed down 293 adsorbents to top 10 scored adsorbents including 4 silica gels, 4 active carbons and 2 molecular sieves. The adsorbent-specific performance is evaluated by numerical simulation, revealing silica gel Type A++, Type 2560, Siogel and molecular sieve AQSOA-FAM-Z02 have peak adsorber temperatures 1.5–9.3 °C lower and increase solar cooling efficiency (SCE) by 25–27 % compared to reference adsorbent Zeolite 13X. A sensitivity analysis of the Dubinin-Astakhov equation shows increasing E and decreasing V leads to an only minor adsorber temperature decrease and minor system efficiency increase. Lower temperatures and higher capacity cannot guarantee better system performance. This underscores that improving system performance cannot be achieved solely through adsorbent optimization but requires system optimization in parallel.

New pretreatment method for detecting petroleum hydrocarbons in soil: silica-gel dehydration and cyclohexane extraction

Oil is a primary source of energy worldwide. However, the use of oil produces large amounts of pollutants, which are detrimental to the environment. The presence of petroleum hydrocarbons in soil is a critical marker of environmental pollution and safety. Rapid on-site detection technology has been broadly used in emergency tracking, offering critical information support for effective reactions to environmental emergencies. Thus, it is expected to play an increasingly critical role in environmental remediation efforts. The current approach for petroleum hydrocarbon detection in soil mainly involves Soxhlet extraction with a combination of solvents, including acetone and n-hexane. The samples are then analyzed after rotary evaporation, dehydration with anhydrous sodium sulfate, and purification using a magnesium silica-type adsorbent. Unfortunately, this approach requires sample analysis to be performed in the laboratory, which is tedious and time consuming, and consumes large amounts of solvents. Moreover, the rotary evaporator is not portable. Therefore, this method is not appropriate for the rapid on-site detection of petroleum hydrocarbons. In this study, a rapid on-site detection method based on silica-gel dehydration and cyclohexane extraction was developed for the extraction and pretreatment of petroleum hydrocarbons (C10-C40) in soil. First, an appropriate amount of silica gel was added to the soil, and the mixture was completely ground to eliminate moisture. Next, petroleum hydrocarbons were extracted with 40 mL of cyclohexane, and the extract was cleaned by Florisil solid-phase extraction (SPE) column elution. Finally, the samples were analyzed by gas chromatography (GC) to evaluate the above method. The silica gel exhibited optimal adsorption properties compared with anhydrous sodium sulfate, calcium oxide, and molecular sieves, with recovery of 87.5%. The effects of different soil water content (5%, 10%, and 20%) and silica gel (1, 3, 5, and 10 times the moisture content) dosage on the extraction of petroleum hydrocarbons were investigated. The recoveries of petroleum hydrocarbons increased from 74.0% to 103.8% after 15 min of invasive extraction (relative standard deviation, RSD, <10.1%) when silica gel amounting to 10 times the moisture content was used. Five types of silica gels with different properties were purchased from four manufacturers, and the effects of these silica gels on the dehydration and extraction efficiency of petroleum hydrocarbons in soil were assessed. The results showed that amorphous silica gel led to low recoveries (<60%), spherical silica gel achieved extraction efficiencies of approximately 70%-90%, and alkaline silica gel produced recoveries with poor precision. Therefore, neutral spherical silica gel was used for further experiments. The fingerprints of petroleum hydrocarbons with different carbon numbers are an important reference for identifying pollution sources. Thus, ensuring good recoveries throughout the entire carbon range is necessary to ensure the accuracy of the fingerprint analysis results. The proposed method showed good recoveries for petroleum hydrocarbons of all carbon numbers (75%-101%). The findings above indicate that the developed method could be an efficient means to extract petroleum hydrocarbons from soil for both total quantity and fingerprint analyses. Compared with standard methods, the proposed method requires lower solvent dosages and features simpler processing steps. Another advantage of this method is that it does not require the use of highly toxic halogenated solvents; thus, it does not contribute to environmental pollution. It can be applied to the laboratory analysis of soil petroleum hydrocarbons and coupled with other rapid on-site detection techniques for soil petroleum hydrocarbons, such as infrared spectroscopy and portable GC. However, because it does not include a concentration process, the developed method exhibits relatively low sensitivity. In the future, we plan to develop a simple and flexible on-site sample-concentration system to further improve various indicators of this method.

SINTESIS SILIKA GEL DARI LIMBAH SEKAM PADI (Oryza Sativa) DENGAN VARIASI KONSENTRASI JENIS ASAM

Rice Husk Ash (RHA) is a material that has the potential to be used in Indonesia because of its high production with sampling results during the rice milling process which produces quite a lot of waste, which is equal to 20% of the grain weight with the characteristics of rice husk which is coarse, has low nutritional value, has a high density. low and high ash content. The high content of silica in rice husk can be a reference for its use as a raw material for making silica. Through this research the authors did this to determine variations in the concentration of acid types on the quality of the water content (%) of the resulting silica gel and to determine the characteristics of acid type silica gel. After conducting research using quantitative methods through data collection and data processing, it was found that the concentration of various types of hydrochloric acid (HCl) had a higher level of water content than the type of citric acid (C6H8O7), obtained the concentration of 9 M, while the FTIR test results showed that silica in the type of acid used contained OH groups which identified silanol (SI-OH) absorption range 3450 - 3550 cm-1 and siloxane functional groups (Si-O) absorption ranges of Si-O functional groups, namely 1075 - 1095 cm-1.

Three Dimensional CFD Simulation Model with Experimental Validation of Silica Gel–Water Pair Adsorption Cooling Bed

In this paper, a three-dimensional full simulation model of a solar-driven adsorption cooling system integrated with user-defined functions (UDF) is successfully validated with a manufactured adsorption chamber filled with silica-gel type A. model is validated on the desorption phase with a maximum deviation error of 1.7%. Temperature with adsorption contours are shown for more understanding of the heat flow with adsorption behaviour inside the chamber in all directions. The maximum temperature at the desorption phase is reached after 300 seconds at fins area, and adsorption maximum uptake reached 0.16 kg/kg at fins wall but reached from 0.13 to 0.14 kg/kg around fins area. The average adsorption uptake reached 0.136 at the end of the adsorption process. The resultant uptake between adsorption and desorption is 0.018 kg/kg with a refrigerant mass of 1.8 kg in a complete cycle time.

Study of the Influence of Different Clothing Materials for Mine Ventilation Clothing on Human Body and Microclimate under Clothing

In order to study the influence of clothing materials on the cooling effect of mine ventilation clothing, the temperatures of human skin and micro-environment under clothing were used as reflection indexes of the cooling effect, and numerical simulations were carried out using fluent software to compare and analyze the temperature changes of human skin and micro-environment under the influence of mine ventilation clothing made of different clothing materials. The results regarding the human skin temperature showed that the modal fiber type resulted in a 0.4 °C lower temperature than the pure cotton type and that the pure cotton type resulted in a 0.6 °C lower temperature than the silica gel type. The temperature comparison of the micro-environment under clothing showed that the modal fiber type resulted in a lower value than the pure cotton type and that the pure cotton type resulted in a lower value than the silicone type; the cooling effect of the three kinds of mine ventilation clothing was modal fiber type &gt; cotton type &gt; silica gel type. In summary, fabric with good permeability and moisture permeability was helpful in improving the cooling effect of mine ventilation clothing.

Accumulation and Emission of Water Vapor by Silica Gel Enriched with Carbon Nanotubes CNT-Potential Applications in Adsorption Cooling and Desalination Technology

This paper presents a study of the application of the properties of water vapor as a gas with high potential energy, strongly dependent on temperature and pressure. Analyses of water vapor sorption on two types of silica gels (SG) (90 wt.%) enriched with carbon nanotubes (CNTs) (10 wt.%), in the context of their application in the design of adsorption beds in adsorption cooling and desalination systems were conducted. The sorption experiments were performed by gravimetric method at a relative humidity of 0% &lt; RH &lt; 100% and temperatures of 298 K, 313 K, and 333 K. The addition of CNTs to SG caused a decrease in the sorption capacity and depended on the temperature. As the process temperature increased, a lower SG/CNT mixtures sorption capacity to vapor was obtained. The highest influence of CNTs was observed at the highest temperature, and the average decrease of sorption capacity was several percent. The ratio of SG/CNT sorption capacity to pure SG values was below 1 in most measurements.

Solvent Influence on Zeta Potential of Stationary Phase-Mobile Phase Interface.

Zeta potential is a surface characteristic formed on the solid surface and liquid interface. It is an interesting way to describe the surface properties of materials; thus, a series of four homemade polar embedded stationary phases that contain phosphate groups incorporated into hydrophobic ligands were investigated according to surface zeta potential. Measurements were carried out using Zetasizer Nano ZS for the stationary phases suspensions prepared in various solvent and solvent binary mixtures. The negative zeta potential values were obtained for most cases due to negatively charged residual silanols and phosphate groups. However, in some solvents: tetrahydrofuran, isopropanol, and toluene zeta potential are positive. Additionally, it was observed that the zeta potential seems to be independent of the type of silica gel used for the stationary phase synthesis.

Theoretical dehumidification capacity of acorn nutshell-based activated carbon under two Asian urban cities’ ambient air condition

• Prepared activated carbon has better dehumidification performance than silica gel under humid ambient air conditions. • Prepared activated carbon can be utilized as desiccant material with a regeneration temperature of lower than 60°C. • The water isotherm shape of prepared activated carbon gives an advantage to the dehumidification performance. Indoor air humidity plays a vital role in determining occupants’ health and industrial product quality. Removing excess humidity by adsorption dehumidification is still facing a challenge in finding a suitable material with high adsorption capacity and low regeneration temperature. In this study, the theoretical dehumidification capacity of prepared acorn nutshell-based activated carbons was calculated and compared with silica gel type RD and RD-2060. The calculation was based on the outdoor air condition in two Asian capital cities: Jakarta and Tokyo. The theoretical study found that prepared activated carbon has better dehumidification performance under Jakarta conditions using regeneration temperatures of less than 60°C. Under Tokyo conditions, activated carbon shows auspicious performance during the summer season. Compared with silica gels, acorn nutshell-based activated carbon has a better dehumidification capacity to process high humidity ambient air with a lower regeneration temperature.

CO2 Capture by Low-Cost Date Pits-Based Activated Carbon and Silica Gel.

The rising levels of CO2 in the atmosphere are causing escalating average global temperatures. The capture of CO2 by adsorption has been carried out using silica gel type III and prepared activated carbon. The date pits-based activated carbon was synthesized using a tubular furnace by physical activation. The temperature of the sample was increased at 10 °C/min and the biomass was carbonized under N2 flow maintained continuously for 2 h at 600 °C. The activation was performed with the CO2 flow maintained constantly for 2 h at 600 °C. The temperature, feed flow and adsorbate volume were the parameters considered for CO2 adsorption. The success of CO2 capture was analyzed by CO2 uptake, efficiency based on column capacity, utilization factors and the mass transfer zone. The massively steep profiles of the breakthrough response of the AC demonstrate the satisfactory exploitation of CO2 uptake under the conditions of the breakthrough. The SG contributed to a maximal CO2 uptake of 8.61 mg/g at 298 K and Co = 5% with F = 5 lpm. The enhanced CO2 uptake of 73.1 mg/g was achieved with a column efficiency of 0.94 for the activated carbon produced from date pits at 298 K. The AC demonstrated an improved performance with a decreased mass transfer zone of 1.20 cm with an enhanced utilization factor f = 0.97 at 298 K. This finding suggests that a date pits-based activated carbon is suitable for CO2 separation by adsorption from the feed mixture.

Experimental Investigation of an Intensified Heat Transfer Adsorption Bed (IHTAB) Reactor Prototype.

The first experience in the operation of intensified heat transfer adsorption bed reactor designed for low-pressure adsorption processes is presented in this paper. This work aims to assess the possibility of fluidizing the porous media bed induced by the pressure difference between the evaporator and the adsorption reactor. The conducted experimental research allowed indicating the type of silica gel recommended to use in fluidized beds of adsorption chiller. The fixed bed of silica gel was observed for the lower pressure differences, while fluidization appeared in the case of the pressure difference between the evaporator and the adsorption chamber higher than 1000 Pa. The most significant differences in the adsorption process between the fixed bed and the fluidized bed are revealed in the changes of sorbent temperatures. The silica gel bed was fluidized with water vapor generated in the evaporator.

Performance Enhancement of Rotary Desiccant Wheel using Novel Homogenous Composite Desiccant Designs

Rotary solid desiccant wheels are used as sensible and latent heat recovery wheels in the Desiccant-HVAC systems. The two major types of these wheels include enthalpy (total energy recovery) wheels which remove sensible heat and latent heat from process air and transfer them to regeneration air, and dehumidification wheels which transfer a significant amount of moisture (latent heat) at the same time minimizes heat transfer. In this work a set of novel design of hybrid rotary desiccant wheel constructed using a composite homogeneous mixture of solid desiccants (multiple types of silica gel and molecular sieves) are proposed. The transport phenomena taking place in the proposed set of novel design of hybrid rotary desiccant wheel are simulated numerically using an in house finite volume method based CFD code. The performances of these wheels are compared with conventional type of wheels made of molecular sieves and silica gel, respectively. The results show that the performance of these hybrid wheels are enhanced by up to 40 % by using these novel composite wheel designs.

Rhamonolipids produced by Pseudomonas aeruginosa promotes methane hydrates formation in fixed bed silica gel medium

Natural gas hydrates are seen as an alternative future energy source. They have also been valued for their carbon dioxide capturing capability, gas separation, desalination, natural gas storage and transportation. Developing economical and viable gas hydrate based technology is one of the most promising research areas of present decade. Successful commercialization of gas hydrate based technology is often curtailed due to slow formation rate. The present study evaluates biosurfactant as a kinetic promoter of methane hydrates formation in a fixed bed C type silica gel medium. Biosurfactant was produced by growing Pseudomonas aeruginosa strain A11 in glycerol supplemented mineral salt medium. Biosurfactant characterization with FTIR, NMR and MALDI-TOF spectroscopy reveled it to be a glycolipids type biosurfactant namely rhamnolipids. Saturating C type silica gel with of 100 ppm rhamnolipids solution enhanced the rate of methane hydrates formation by reducing the induction time. Mole of methane consumed and percentage of water to hydrate conversion was observed to be more in 1000 ppm rhamnolipids saturated C type silica gel as compared to quiescent water system and water saturated silica gel system. Overall results suggest that rhamonolipids produced by strain A11 in combination with silica gel can be utilized as environmentally safe kinetic promoter for methane hydrate formation.

EXPERIMENTAL CHECKING OF ABSORPTION OF MOISTURE ABSORBERS IN VARIOUS CLIMATE CONDITIONS

The article presents results of tests for moisture absorbers currently used and available on the market. Experimental investigations were carried out for two types of silica gels, the bentonite clay and two types of molecular sieves available on the market, as well as for the reused silica gel currently deployed in weapon systems. As part of the work, the maximum absorbency of moisture absorbers for various climatic conditions, the minimum relative humidity (RH) in the drying measuring chamber for various amounts of absorbent, and the durability of water binding at variable temperature conditions were determined. Analysis of results allowed both to compare advantages and disadvantages of various absorbents, and to assess a degree of the wear for moisture absorbents currently used in armament equipment.

Investigation of Xenon Extraction from ASU Streams by Low-Temperature Adsorption

The article considers a method for extracting xenon from gas concentrates on the basis of batch adsorption separation. An experimental unit for studying xenon adsorption dynamics at cryogenic temperatures was developed. Simulations were carried out in order to investigate the process of xenon adsorption from an air separation unit (ASU) “safety stream” on different sorbent materials (four types of silica gel and active aluminum oxide). A krypton-nitrogen-helium (Kr-N2-He) mixture was selected for the purposes of modeling to comply with fire and explosion safety requirements and to reduce the duration of the experiment. From analyzing the data obtained using the described, specially-developed experimental technique, we selected the sorbent having the maximum dynamic capacity for our application.

Comparative Evaluation of Adsorbents for Natural Gas Dehydration at Liquefied Natural Gas Plant

Adsorption dehydration of natural gas plays an important part in LNG production. The primary goal of this research is increasing efficiency of adsorption dehydration of the gas preparatory to its liquefaction. The results of comparative evaluation and determination of the optimum thermobaric parameters of the process of natural gas adsorption dehydration with KSMG type of silica gel and NaA-BS type of zeolite-containing adsorbent are expounded. It is shown that adsorbent load, adsorber metal content, and regenerating, cooling and heating gas consumptions can be reduced by reducing temperature of the natural gas stream undergoing adsorption dehydration. Recommendations are offered regarding installation of the drying unit after the precooling stage to reduce capital and operating costs. The obtained data are highly useful for designing and updating LNG production processes.

Experimental study on thermophysical and porous properties of silica gels

Porous silica gel (SG) has been extensively used as an adsorbent in adsorption cooling, dehumidification, and desalination applications. Specific heat capacity (Cp) of SG with temperature variation is not experimentally investigated yet. Therefore, this study focuses on the experimental investigation of Cp along with the porous properties of six types of different particle size silica gels. Adsorbed phase Cp of SG is also determined with 10% and 20% water uptake. The experimental Cp is measured within 30 to 100 °C, and the Cp values vary from 0.8 to 1.10 kJ kg–1 K–1 in the measurement temperature range. RD silica gel of the smallest particle size shows the highest Cp values, whereas indicator type silica gel shows the lowest Cp. The Green-Perry model fits well with the experimental Cp data. The porosity analysis shows that RD silica gels of large particle size (D > 0.7 mm) possess the highest surface area (≈ 770 m2/g), and type B silica gels have the largest pore volume (≈ 0.8 cm3/g) along with larger mesopores. A relationship between pore volume and Cp is also reported. The measured data are novel and essential for rigorous performance prediction of adsorption cooling, dehumidification, and desalination systems.

Optimal thermobaric parameters determination of natural gas dehydration in LNG production

Gas dehydration is one of the main technological processes in natural gas treatment for pipeline transportation and LNG production. The main task of this research is to increase the efficiency of adsorption gas dehydration. This report presents the results of a comparative assessment and determination of the optimal thermobaric parameters of the process of natural gas dehydration with KSMG type of silica gel and NaA-BS type of zeolite-containing adsorbent. It has been shown that reducing the temperature of the natural gas before dehydration reduces the mass of loaded adsorbent, the mass of adsorber, the consumption of regeneration gas, cooling gases, and fuel gas for heating regeneration gas. Recommendations on the dehydration unit placement after pre-cooling stage in order to reduce capital and operating costs are given at the end of the article. The results are important in the design and modernization of technological processes of the LNG production.

Performance enhancement of adsorption beds with silica-gel particles packed in aluminum foams

Effective thermal conductivity of a silica-gel/water adsorption packed bed is significantly enhanced by placing silica-gel particles in a high-porosity aluminum foam. The enhancement leads to several folds increase in the specific cooling power (SCP), cooling capacity per unit volume (CPv) and coefficient of performance (COP) of an adsorption cooling (AD) chiller. The thermal response and adsorption kinetics of various silica-gel/aluminum foam beds under typical operating conditions are investigated experimentally and numerically. Effect of pores per inch (PPI) of the foam, silica-gel particle size, bed height and adsorption isotherm of different types of silica-gel on the bed performance are investigated. Based on the results, aluminum foam with 20 PPI is recommended for adsorption cooling applications due to its high surface area and small cell size. 20 PPI aluminum foam can deliver a SCP of 827 W/kg, a CPv of 517 W/m3 and a COP of 0.75.

Study on building surface and indoor temperature reducing effect of the natural meso-porous material to moderate the indoor thermal environment

This paper aims to investigate the performance of several reflective and evaporative wall coatings, to determine the most effective one to moderate the indoor thermal environment. Eight reflective coatings with different colours and characteristics were selected. For the evaporative coating, three different samples with Wakkanai siliceous shale (WSS) particle; small, medium, large and silica gel type B were produced in the laboratory and another WSS mortar previously developed in the laboratory were selected. At first, an uncoated concrete, reflective coatings and WSS mortar, as a representative of evaporative group, coated blocks were experimented in the chamber under simple boundary conditions. The minimum value of outdoor and indoor surface temperature was recorded for the white uneven coating and white dirt resistant coating that can reduce the outdoor and indoor surface temperature by 6.9 °C and 1.9 °C respectively. The result of steady state experiment reveals that in constant relative humidity, evaporative coatings are not effective. Next, periodic experimentation was conducted with variations of temperature; relative humidity and solar radiation. From the results the minimum value for outdoor surface was found for white uneven thermal barrier coating (SR4), which can reduce the temperature up to 7.9 °C and the minimum inner surface temperature was recorded for WSS particle (L) that can reduce 5.8 °C. The better performance of porous particles was possibly caused by the moisture adsorption at night time and latent heat release at daytime. This study supports that the meso‑porous coatings for building envelopes can significantly contribute to moderate the indoor thermal environment.

An approach for quantitative analysis of pore size distribution of silica gel using atomic force microscopy

This article discusses a direct approach for assessing irregularly shaped pore distribution of porous materials using Atomic Force Microscopy (AFM). Using the tapping mode, AFM is employed to obtain the surface topographic information of the porous materials commonly used in adsorption applications. Three different types of silica gels, commercially used silica–alumina and acetaminophen samples are investigated using an image processing technique to capture the pore size-related information. Macro and mesopores in a specified region are visualized then quantified and counted using 2-D Fast Fourier Transformation (2D FFT) technique. The results obtained by the AFM technique are then compared with the BET surface area and pore size distribution (NLDFT) extracted from the N2 adsorption isotherms.