Silica Adsorbents Research Articles

Application of response surface methodology (rsm) for optimisation of cod removal from tofu wastewater in an adsorption process using silica adsorbent

The entry of pH, turbidity, COD, and TSS pollutants from tofu wastewater decreases discharge water quality and may affect the discharge water treatment process. This study aims to find variations in the mass and size of silica and the optimum adsorption time on the removal efficiency of pH, turbidity, COD, and TSS from tofu wastewater using silica adsorbent with applying surface response methodology. Chemical treatment was carried out to meet turbidity, COD, and TSS parameters. The research method used a laboratory-scale batch system with adsorbent size, mass, and adsorption time variations. From the research conducted, it obtained that the best removal for the pH test was the 100 mesh silica variation in the treatment of 3.295 gr with an adsorption time of 37 minutes; the pH value after removal was 4.87, for the turbidity test was 80 mesh silica variation in the treatment of 10 gr with an adsorption time of 15 minutes and the turbidity value after removal was 114 NTU, for the COD test, the best removal was obtained from a variation of 8.74937 gr of 104,342 mesh size silica at 39.0248 minutes of contact time with a COD value after removal of 851.33 mg/l, then for the TSS test was the 80 mesh silica variation in the treatment of 10 gr with an adsorption time of 59 minutes and the TSS value after removal was 65 mg/l.

Adsorption of anionic methyl orange dye on hybrid spherical silica in fixed-bed column

The textile sector is recognized for contributing the most dye residue, which is one of today's environmental challenges. It is a risky technique since wastewater includes toxins that can damage water sources and endanger human health and aquatic life. As a result, wastewater must be treated before disposal. There are numerous methods for removing dyes from wastewater, which categorized into chemical treatments, physical and biological procedures.. This study chose the continuous adsorption approach, which falls under the physical method since it is simple and effective. The oil-in-water emulsion was used to synthesize spherical silica (SSi) adsorbent in order to effectively remove and remediate one of the water-soluble anionic dyes, methyl orange dye (MO). The effect of influent concentration (10 to 50 ppm) and bed height (1.0 to 2.0 cm) on the continuous process was investigated. The breakthrough time exhibited an increase as the dye concentration decreased for all solutions that were examined. The removal efficiency of MO increased as the bed height increased, which can be attributed to the longer contact time between the MO dye and the adsorbent. The Thomas model exhibited a more favorable level of conformity to the data than Adams-Bohart and Yoon-Nelson. According to Thomas ' model, the maximum adsorption capacity (qo) increased as bed height decreased, and concentration increased. Moreover, Correlation values ranged from 0.882 to 0.979. Therefore, spherical silica adsorbent has the highest methyl orange dye adsorption capability at a bed height of 2.0 cm and concentration of 50 ppm.

Determination of Optimum Conditions for Nitrate Anion (NO3 −) Desorption on Mesoporous Silica Modified with Dimethylamine (DMA)

Mesoporous silica is an inorganic material that has high potential to be applied in various industrial fields, one of its applications is the adsorption method. To maximize the adsorption of mesoporous silica, modification of the silica surface was carried out by adding amine compounds. The amine compound used as a modifier is dimethylamine (DMA), using glycidoxypropyltrimethoxysilane (GPTMS) as a linking compound. The column method uses mesoporous silica, modified with dimethylamine, in the nitrate anions adsorption process. The adsorption capacity of the nitrate anion is 0.0917 mg/g. After adsorbed, the desorption process was carried out to release the adsorbed nitrate anions. The desorption process found that HCl was the best desorption agent used on nitrate anions. The optimum concentration of HCl was 0.15 M, with the number of nitrate anions desorbed as much as 0.0459 mg with a 100% desorption percentage.

C18 -functionalized zirconized silica for effective removal of phorate pesticide from agricultural runoff involving groundwater remediation

Phorate, a highly toxic organophosphorus pesticide, is frequently used in agriculture to control insects and pests. It can persist for long periods in water sources, posing a risk to human health, aquatic life, and wildlife. Thus, this study developed a practical method for the removal of toxic phorate from water using C18-modified zirconized silica (named C18–ZrSi) adsorbent. Batch adsorption experiments were conducted by varying pH, adsorbent amount, phorate concentration, incubation time, and temperature. The optimal conditions for maximum adsorption of phorate were found to be at pH 7.0 and a temperature of 20–30 °C. X-ray- related and electron microscopies were implemented to characterize the features of the C18–ZrSi adsorbent and demonstrated the phorate adsorption on their surface. The C18–ZrSi adsorbent exhibited adsorption behaviour towards phorate that adhered to a mixed Freundlich and Langmuir isotherm, with a spontaneous and exothermic adsorption process, pseudo-second-order kinetics, and multiple stages of adsorption. The maximum Langmuir adsorption capacity of the C18–ZrSi adsorbent for phorate was identified as 30.5 mg g−1. It is proved that the C18–ZrSi adsorbent efficiently capture phorate from water through the hydrophobic interaction, hydrogen bonding, and Lewis acid-base force. In addition, the C18–ZrSi adsorbent recovered more than 89% of phorate after the third adsorption and desorption. We demonstrated that the C18–ZrSi adsorbent exhibited good selectivity for the removal of phorate from agriculture runoff water samples.

Adsorption of Phenoxyacetic Herbicides from Water on Carbonaceous and Non-Carbonaceous Adsorbents.

The increasing consumption of phenoxyacetic acid-derived herbicides is becoming a major public health and environmental concern, posing a serious challenge to existing conventional water treatment systems. Among the various physicochemical and biological purification processes, adsorption is considered one of the most efficient and popular techniques due to its high removal efficiency, ease of operation, and cost effectiveness. This review article provides extensive literature information on the adsorption of phenoxyacetic herbicides by various adsorbents. The purpose of this article is to organize the scattered information on the currently used adsorbents for herbicide removal from the water, such as activated carbons, carbon and silica adsorbents, metal oxides, and numerous natural and industrial waste materials known as low-cost adsorbents. The adsorption capacity of these adsorbents was compared for the two most popular phenoxyacetic herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA). The application of various kinetic models and adsorption isotherms in describing the removal of these herbicides by the adsorbents was also presented and discussed. At the beginning of this review paper, the most important information on phenoxyacetic herbicides has been collected, including their classification, physicochemical properties, and occurrence in the environment.

Determination of Al(III), Pb(II), and Cu(II) in Gunshot Residue Using Amino-Functionalized Silica Adsorbents in Dispersive Solid Phase Microextraction (DSPME) with Capillary Electrophoresis (CE)

Here is reported the design, synthesis, and application of an amino silica adsorbent for the extraction and determination of Al(III), Pb(II), and Cu(II) in gunshot residue (GSR) from the dorsal and palmar zones by capillary electrophoresis. The extraction procedure was used to determine the adsorbent composition by varying the molar ratio of the cross-linking agent tetramethyl orthosilicate (TMOS) and the functional monomer 3-aminopropyl trimethoxysilane (APTMS). (5.0:0.0 to 0.0:5.0). The optimal composition (3.0:2.0) was characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and adsorption isotherm analysis. A univariate method was used to optimize critical factors in dispersive solid phase microextraction (DSPME), including the adsorbent mass, contact time, sample volume, and elution solution. Using the optimal conditions (adsorbent, 10 mg; contact time, 10 min; sample volume, 5 mL; eluent solution, methanol/10−1 mol L−1 HNO3), the method provides limits of detection of 0.06 mg L−1 for Pb(II), 0.08 mg L−1 for Cu(II), and 0.11 mg L−1 for Al(III). The precision and accuracy were evaluated in terms of inter- and intra-day repeatability (n = 3) with a relative standard deviation below 10%. The developed method was applied for gunshot residue analysis, providing concentrations from 12.6 to 702 mg L−1 for Al(III), 11.8 to 280 mg L−1 for Pb(II), and 29.8 to 395.6 mg L−1 for Cu(II).

Molecular Simulation Techniques as Applied to Silica and Carbon-Based Adsorbents for Carbon Capture

There has been ongoing interest in research to mitigate climate change through carbon capture (CC) by adsorption. This guideline is meant to introduce computational chemistry techniques in CC by applying them to mesoporous structures and disordered morphologies. The molecular simulation techniques presented here use examples of literature studies on silica and carbon-based adsorbents. An initial summary of molecular simulation techniques and concepts is first presented. This is followed by a section on molecular simulation applications in mesoporous amorphous silica, both functionalized and not. Novel strategies to validate and output useful results are discussed, specifically when modelling chemisorption. The use of computational chemistry to build upon experimental results is reviewed, and a similar summation is presented for carbon-based adsorbents. The final section provides a short review of computational chemistry methods in novel applications and highlights potential complications. Computational chemistry techniques provide a streamlined method of gathering data across a range of conditions. Alongside experimental studies, these techniques can provide valuable information on underlying molecular mechanisms. This paper aims to be a starting point for navigating these numerical methods by providing an initial understanding of how these techniques can be applied to carbon capture while clarifying the current and inherent limitations present.

Ionic liquid – grafted mesoporous silica exhibiting reverse selectivity for ethane/ethylene separation

Development of paraffin-selective adsorbents for the separation of ethane/ethylene mixtures, as an alternative technology to the energy-intensive cryogenic distillation, is challenging. Herein, we report surface-functionalized mesoporous silica adsorbents exhibiting reverse selectivity prepared by controlled in-situ synthesis of paraffin-selective ionic liquids (ILs) onto the pre-silanized surface of MCM-41 mesoporous silica. The surface modification switched the selectivity of the adsorbents from being inherently olefin-selective to becoming paraffin-selective, due to the enhanced van der Waal’s interactions between the grafted IL functionalities and the ethane molecules. A range of silica-based adsorbents functionalized with ILs of different loadings and anion and cation types were synthesized, characterized and investigated for their ethane/ethylene adsorption behavior. In addition to reversing the selectivity yielding values of up to 3.4 for ethane over ethylene, the adsorbents exhibited low isosteric heat of adsorption, indicatively 12 kJ/mol for ethane, while their performance was stable upon pressure swing adsorption and breakthrough cyclic testing. Dynamic packed bed experiments with ethane/ethylene mixtures demonstrated a breakthrough ethylene productivity of up to 1.2 mmol/g with a breakthrough selectivity of 2.4.

Equilibrium steps for adsorption of nitrogen compounds : examining the potential of silica application as adsorbent

The hydrotreating (HDT) process currently used to reduce the sulphur content in fuels requires high energy consumption and hydrogen. Furthermore, the presence of nitrogen compounds makes them more severe. This work studies the removal of nitrogen compounds present in a sample of heavy diesel using a commercial silica sample. Adsorption tests were performed in a stirring bath to generate the equilibrium data. Three test conditions were used at temperatures of 40, 80 and 100 °C. In adsorption studies in a fixed bed, the influence of temperature and liquid hourly space velocity (LHSV) was observed . In the regeneration test of the adsorbent, adsorption was achieved at 80 °C and desorption at 60 °C. Ethanol was used as the solvent and fourteen adsorption tests and thirteen desorption tests were performed. The removal of sulphur compounds in the stirring bath tests were checked. From a comparative perspective, the silica adsorbent used showed a higher affinity to the removal of nitrogen compounds than those related to sulphur in the stirring bath tests. The recovery test showed a reduction of approximately 20% in adsorption capacity of the adsorbent treated after the adsorption cycle in relation to the fresh adsorbent. This result indicates that the silica sample can be reused.

As(V) removal from aqueous media using an environmentally friendly zwitterion L-cysteine functionalized silica adsorbent

An L-cysteine functionalized environmentally friendly adsorbent was synthesized via sol–gel processing and applied in the removal of As(V) from aqueous media. The adsorbent demonstrated enhanced As(V) uptake capacities with maximum uptake of 147.5 mg g−1 at pH 3. Equilibrium was reached at 120 min. Kinetic data were explained by a pseudo-second order model; isotherm data were fitted by a Freundlich model. Reuse of adsorbent after 5 adsorption/desorption cycles indicated ∼23% removal capacity loss. Elemental analysis results indicated high ligand densities of SG-3PS-Cys. The L-cysteine moieties were thermally stable up to ∼170 °C. Solid state NMR and XPS techniques confirmed the presence of cysteine on the surface of SG-3PS-Cys. Efficient adsorption of As(V) was ensured by the formation of a bidentate complex between the AsO2(OH)2- anion, the NH3+ and carboxyl groups of L-cysteine. The results of this work demonstrated that SG-3PS-Cys possesses potential in the removal of As(V) from industrial wastewater discharges.

Thermodynamics of Azo Dye Adsorption on a Newly Synthesized Titania-Doped Silica Aerogel by Cogelation: A Comparative Investigation with Silica Aerogels and Activated Charcoal.

The adsorption isotherms of azo dyes on a newly synthesized titania-doped silica (TdS) aerogel compared to silica aerogels and activated charcoal (AC) are systematically investigated. Monolithic TdS aerogels were synthesized by the cogelation process followed by supercritical drying of tetraethyl orthosilicate (TEOS) as a gel precursor and titanium(IV) isopropoxide (TTIP) as a metal complex precursor for co-polymerization in ethanol solvent. An acid-base catalyst was used for the hydrolysis and condensation of TEOS and TTIP. The effect of Ti4+ doping in a silica aerogel on the mesoporous structure and the adsorption capacity of methylene blue (MB) and crystal violet (CV) dyes were evaluated from the UV-vis absorption spectra. In order to compare the adsorption isotherms, the surface areas of silica and TdS aerogels were first normalized with respect to AC, as adsorption is a surface phenomenon. The azo dye equilibrium adsorption data were analyzed using different isotherm equations and found to follow the Langmuir adsorption isotherm. The maximum monolayer adsorption capacities for the adsorbent TdS aerogel normalized with the AC of the Langmuir isotherm are 131.58 and 159.89 mg/g for MB and CV dyes, respectively. From the Langmuir curve fitting, the Q max value of the TdS aerogel was found to increase by 1.22-fold compared to AC, while it increased 1.25-1.53-fold compared to the silica aerogel. After four cycles, regeneration efficiency values for MB and CV dyes are about 84 and 80%, respectively. The study demonstrates the excellent potential and recovery rate of silica and TdS aerogel adsorbents in removing dyes from wastewater. The pore volume and average pore size of the new aerogel, TdS, were found to be lower than those of the silica aerogel. Thus, a new TdS aerogel with a high capacity of adsorption of azo dyes is successfully achieved.

Precise separation and efficient enrichment of palladium from wastewater by amino-functionalized silica adsorbent

An amine-based functionalized mesoporous silica (SBA-15-TEPA) adsorbent constructed from mesoporous silica was produced to realize efficient and highly selective recovery of palladium from wastewater. SEM-EDS, TEM, TG-DSC, and N2 adsorption-desorption isotherm were used to evaluate the as-prepared SBA-15-TEPA, and the results demonstrate that the material has a good open pore structure, a high loading rate, and a sizable specific surface area. The performance analysis demonstrates that SBA-15-TEPA exhibits excellent selectivity (Separation factor of palladium for impurity ions >5565) in a broad range of acidity and good repeatability (≥5) toward palladium, good repeatability is important for clean adsorption, with a maximal capacity of 94.92 mg Pd/g at pH = 1.5 at 315 K. 0.1 M thiourea - 0.1 M HNO3 was capable of desorbing the adsorbed Pd(II) almost entirely. The mechanism of adsorption and desorption was investigated by FT-IR, XPS and DFT calculation, which proves that the coordination structure occurs mainly between N in the adsorbent and Pd(II) with NO3− participation for change balance, i.e., the strong chemical complexation between the electron pair acceptor Pd(II) and the electron pair donor N. The dynamic separation of Pd(II) by SBA-15-TEPA from simulated electroplating wastes was evaluated by column experiment, and nearly 100% recovery of Pd(II) was obtained with demonstrating outstanding enrichment coefficients (>104). SBA-15-TEPA met the requirements of dynamic adsorption experiments and successfully achieved the complete separation and high enrichment of palladium from waste liquids in high throughput. This result fills the gap where functionalized silicon-based materials could not be separated and enriched for palladium in column experiments and will also provide new ways to address palladium scarcity, environmental protection and ensure cleaner production.

Interface interaction between silica and organic macromolecule conditioned forward osmosis membranes: Insights into quantitative thermodynamics and dynamics

Silica scaling is a rising concern in forward osmosis membrane-based water treatment process. The coexistence of ubiquitous organic macromolecules causes complex silica scaling. The silica scaling mechanism on the surface of the organic conditioned membrane remains unclear. An integrated multi scale thermodynamic and dynamic approach was used in this study to provide in-depth insights into the binding effect at the interface between the silica and the organic conditioned membrane at the molecular level. Sodium alginate (SA) was used as the model polysaccharide, bovine serum albumin (BSA) and lysozyme (LYZ) were chosen as two oppositely charged proteins. The results show that the silica scaling degree of different organic conditioned membranes follows the order LYZ > BSA > SA. The binding strength between silica and organic macromolecules and the membrane surface charge are the major factors governing the degree of silica scaling. Quartz crystal microbalance with dissipation (QCM-D), isothermal titration calorimetry (ITC), and extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) model analyses were conducted to quantify the binding capacity of silica to the organic conditioned membrane. The LYZ conditioned membrane exhibits the highest affinity for silica adsorption, and electrostatic interaction was the main molecular interaction force. This study provides fresh insights into how silica and an organic conditioned membrane interact and induce silica scaling, providing new information on potential mechanisms and control strategies to prevent membrane scaling.

Methylthiazole Schiff base functionalized SBA-15 for high-performance Pb(Ⅱ) capture and separation

Selective recovery of Pb(II) from effluent reduces its toxic impact on environment and benefits for saving non-renewable lead resources. To capture and separate Pb(II), a kind of methylthiazole Schiff base modified mesoporous silica, denoted as MTCI-SBA-15, was fabricated via grafting amino groups onto SBA-15 which was followed by Schiff condensation with 4-methylthiazole-5-carboxaldehyde. A variety of characteristic methods monitored the evolution of the modified adsorbent. Pb(II) uptake to MTCI-SBA-15 was studied in batch mode concerning pH, contact time, initial concentration, temperature, coexisting metallic ions, etc. Kinetic analyses revealed that the pseudo-second-order model was suitable for describing adsorption process. The adsorption isotherms were well represented by the Langmuir model. The thermodynamic study confirmed that the sorption was spontaneous and endothermic. The maximal load ability of MTCI-SBA-15 (283 mg g−1) for Pb(II) outperformed that of most modified mesoporous silica adsorbents. Moreover, Pb(II) removal efficiency higher than 99% can be reached with a low initial concentration (<50 mg L−1). Testing on the effects of competing ions suggested that MTCI-SBA-15 exhibited a desirable selectivity for Pb(II). Further, MTCI-SBA-15 was recyclable, retaining 93.1% of the adsorption capacity after five successive cycles. Mechanisms investigation indicated that the imine N atom on the Schiff base and the S atom on the 4-methylthiazole ring played a synergistic role during the adsorption process for Pb(II). The MTCI-SBA-15 showed excellent application potential for Pb(II) capture and separation.

Aminosilane-Modified Ordered Hierarchical Nanostructured Silica for Highly-Selective Carbon Dioxide Capture at Low Pressure

Ordered hierarchical nanostructured silica (OHNS) adsorbents were prepared, and their surface was controllably modified by aminosilanization using two different aminosilanes, one bearing one primary amine unit per molecule (4-aminobutyltriethoxysilane, ABTS) and the other bearing both a primary and a secondary amine (N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, AAMS). Following physicochemical, structural, morphological, and porosity characterization, the CO2 adsorption performance was evaluated at low pressures (up to 100 mbar) and at different temperatures (25, 45, and 60 °C), including determination of CO2 adsorption–desorption, kinetics, CO2/N2 selectivity, regeneration/cycling, heat of adsorption, and CO2 adsorption under humid conditions. The unique hierarchical silica framework together with the aminosilanization scheme applied resulted in enhanced kinetics and CO2 uptake, the latter being increased with temperature, thus revealing a dominant chemisorption mechanism, which was further evidenced by the increase in the enthalpy of adsorption of the modified materials compared to the pristine OHNS. Among the tested adsorbents, at 100 mbar and 25 °C, the OHNS modified by AAMS yielded the highest CO2 uptake under dry (1.3 mmol/g) and wet (1.9 mmol/g) conditions. Notably, at very low pressure (1 mbar), the CO2 capacity of OHNS-AAMS reached >40% of the material’s total uptake at 1 bar. Compared to the unmodified OHNS, the CO2 capacity of the OHNS-AAMS and OHNS-ABTS increased by approximately 21- and 16-fold, respectively, at 1 mbar and 25 °C. At even lower pressure (0.4 mbar), a capacity of 0.55 mmol/g was evidenced for OHNS-AAMS in dry CO2. A very high CO2/N2 selectivity of the AAMS-modified analogue at low pressure was also obtained, i.e., 13,854 at 50 mbar, confirming the significant increase in CO2-philicity via aminosilanization with aminosilanes bearing combined primary and secondary amine groups. Furthermore, the water affinity of the aminosilane-modified OHNS adsorbents was found to decrease, which is beneficial for capture from humid mixtures. Cyclic stability was confirmed by performing 10 thermal pressure swing adsorption (TPSA) cycles up to 100 mbar. The hierarchical nanostructured silica-based framework and the functionalization scheme presented here render these robust systems promising for selective CO2 capture at low pressures in industrial applications and direct air capture.

A method to enrich polypeptidyl-tRNAs to capture snapshots of translation in the cell.

Life depends on proteins, which all exist in nascent states when the growing polypeptide chain is covalently attached to a tRNA within the ribosome. Although the nascent chains, i.e. polypeptidyl-tRNAs (pep-tRNAs), are considered as merely transient intermediates during protein synthesis, recent advances have revealed that they are directly involved in a variety of cell functions, such as gene expression control. An increasing appreciation for fine-tuning at translational levels demands a general method to handle the pep-tRNAs on a large scale. Here, we developed a method termed peptidyl-tRNAenrichment using organic extraction and silica adsorption (PETEOS), and then identify their polypeptide moieties by mass spectrometry. As a proof-of-concept experiment using Escherichia coli, we identified ∼800 proteins derived from the pep-tRNAs, which were markedly biased towards the N-termini in the proteins, reflecting that PETEOS captured the intermediate pep-tRNA population during translation. Furthermore, we observed the changes in the pep-tRNA set in response to heat shock or antibiotic treatments. In summary, PETEOS will complement conventional methods to investigate nascent chains in the cell.

Rational design of selective functionalized silica adsorbents for Hg(II) removal from FGD wastewater. A combined experimental and theoretical study.

The binding of Hg2+ by mercaptan-functionalized silica possessing different physical characteristics was explored through experimental investigations and theoretical calculations. The impacts of the pore structure of silica adsorbents on functionalization and the kinetics of Hg2+ adsorption were also studied. The mechanism of Hg2+ adsorption was proposed based on the results of experimental and theoretical studies. The DFT calculations suggested a simultaneous monodentate and bidentate Hg2+ complex formation on sulfur-containing surface functional groups that strongly depends on the Hg2+ concentration. Theoretical Hg2+ adsorption isotherms predicted by DFT calculations have shown that even when the adsorbent surface had heterogeneous adsorption sites capable of simultaneous monodentate and bidentate complexation, the adsorption still followed the Langmuir model.

Synthesis and comparison analysis of modified silica adsorbent and bismuth catalyst for removal of bisphenol A

Synthesis and comparison analysis of modified silica adsorbent and bismuth catalyst for removal of bisphenol A

Determination of the surface properties and adsorption states of nanoporous materials using the zeta adsorption isotherm.

The adsorption process of porous materials has always been a popular field of research in interfacial physics, and the surface physical parameters of materials can be obtained from their adsorption characteristics, which has a great influence on the performance of materials. Based on the zeta adsorption isotherm, we propose a method based on the zeta adsorption isotherm to predict the entire adsorption process of porous materials and determine material surface properties from the measured isotherm data in the heterogeneity-free range. We applied the zeta constants of the silica adsorption system to the corresponding adsorption isotherm of the porous material. The results showed that the predicted adsorption isotherms are in good agreement with the experimental measurements before pore filling and can effectively identify the pressure ratios at the beginning and end of pore filling. In the region of high-pressure ratios, the Kelvin equation was utilized to calculate the pressure ratio at a contact angle of 0°. The surface parameters of the materials were determined by geometrically calculating the variation of the adsorption amount and the desorption isotherms in the high-pressure ratio range were calculated from these surface parameters. The predicted desorption isotherms can well reflect the adsorption process of silica porous materials in the region of a high-pressure ratio. In addition, for the surface parameters of the materials, the specific surface area calculated from the adsorption and desorption isotherms, respectively, differed by less than 7.9%, and the reliability of the method was verified by comparing the results with those of the argon adsorption systems.

Removal of Methyl Orange Using Hybrid Spherical Silica Adsorbents

This study investigated the potential of adsorption behaviour of methyl orange onto hybrid spherical silica adsorbent. Removal of dye has been a problem worldwide and the study of removing dye through adsorption method is quite limited. This study aims to synthesize and characterize spherical silica (SSi) adsorbent and evaluate its adsorption capacity of it. The spherical silica adsorbent (SSi) was prepared using oil-in-water (o/w) emulsion polymerization modification where Tetraethyl Orthosilicate (TEOS) acts as the silica precursor. The physicochemical properties of SiNs were characterized using Fourier transform infrared (FTIR), field emission scanning (FESEM), nitrogen adsorption/desorption analysis (NAD), and transmission electron microscopy (TEM). The batch adsorption study for the methyl orange removal parameters such as pH (2-10 ) and agitation time (0-180 minutes). The experimental adsorption data were further evaluated using several adsorption kinetic models, namely pseudo-first-order, pseudo-second-order and Elovich kinetic models. The diffusion kinetics model includes the Weber-Morris plot, Fick’s Law equation and Boyd plot. The result shows that the spherical silica (SSi) adsorbent at pH 2 has the highest adsorption capacity amongst another adsorbent towards methyl orange which is 45.05 mg/g. Furthermore, the equilibrium time for methyl orange adsorption onto SSi was 120 min. The data fitted into a pseudo-second-order kinetic model indicating chemical adsorption, limited by film diffusion.