scholarly journals Preparation of gold-coated sand for ultratrace mercury analysis

2015 ◽  
Vol 18 (2) ◽  
pp. 211-220
Author(s):  
An Quoc Trieu ◽  
Mai Thi Huynh Le ◽  
Nho Thanh Nguyen ◽  
Dong Van Nguyen
Keyword(s):  
Certified Reference Materials ◽  
Gold Solution ◽  
Amino Groups ◽  
Silanol Groups ◽  
Sand Surface ◽  
Nano Gold ◽  
Mercury Analysis ◽  
Modified Surface ◽  
Ultra Trace ◽  
Coated Sand

In this study, the gold-coated sand was prepared to make gold-trap for mercury analysis at ultra-trace levels. The preparation process was conducted with the etching of sand surface to form silanol groups using a mixture of H2O2/H2SO4 followed by the replacement of the silanol groups by amino groups with aminopropyltriethylsilane. The amino-modified surface is embedded with Au atoms by soaking the amino modified sand in nano gold solution then the Au film is thickened with a mixture of Au(III)+NH2OH.HCl. The gold-coated sand can capture up to 21 μg Hg per 1 g of sorbent. The interferences for the efficiency of mercury sorption such as HNO3, HCl, H2SO4 and temperatureare were investigated. The goldcoated sand was successfully applied for mercury analysis in certified reference materials (DORM-4) by CV-AAS and combustion/thermal decompostion methods.

scholarly journals To the question of the influence of a silanol cover on the protolytic properties of aminopropyl silica gels

2020 ◽  
Vol 7 (4) ◽  
pp. 222-228
Author(s):  
O. V. Filisteev ◽  
A. V. Sharov
Keyword(s):  
Electric Double Layer ◽  
Silica Gels ◽  
Hydrogen Ions ◽  
Structure And Properties ◽  
Amino Groups ◽  
Acid Base ◽  
Preliminary Calculation ◽  
Silanol Groups ◽  
Surface Filling ◽  
Protolytic Properties

The paper proposes a model that describes the acid-base properties of amino groups grafted onto the surface, taking into account their interaction with silanol groups. For this, aminopropyl silica was chosen as an object with well-studied methods of preparation, structure and properties. The isotherms of sorption of hydrogen ions on aminopropyl silica were obtained by potentiometric method. The experimental points were analyzed numerically, taking into account the presence of an electric double layer, the presence of surface processes competing with the sorption of hydrogen ions, and the peculiarities of the behavior of silanol groups when the degree of surface filling with hydrogen ions changes. The resulting model makes it possible to carry out a preliminary calculation of the sorption of hydrogen ions on the surface of aminopropyl silica.

Competitive adsorption of copper and lead ions on an iron-coated sand from water

2000 ◽  
Vol 42 (3-4) ◽  
pp. 149-154 ◽  
Author(s):  
C.H. Lai ◽  
C.Y. Chen ◽  
P.H. Shih ◽  
T.H. Hsia
Keyword(s):  
Iron Oxide ◽  
Metal Ions ◽  
Competitive Adsorption ◽  
Copper Ions ◽  
Column Experiment ◽  
Continuous Treatment ◽  
Lead Ions ◽  
Treatment Unit ◽  
Sand Surface ◽  
Coated Sand

Iron oxides are good adsorbents for some metal ions. However, the adsorbent properties of these oxides are not fully exploited in water or wastewater operations because of difficulties associated with their separation from the aqueous phase. An oven process with agitators for applying an iron oxide coating onto the sand surface to utilize the adsorbent properties of the coating and filtration properties of the sand media was developed. The competitive adsorption of iron-coated sand for copper and lead ions from water was investigated by batch and column experiments. Among the two metal ions studied, the coated sand has greater affinity for the removal of lead ions compared to copper ions at a concentration of 5×0-5M, 1×10-4M and an interval of pH=2.5∼6.5. Adsorption behaviors of copper and lead ions at the iron oxide/water interface could be proved to form chemisorption through the SEM/EDAX analysis. From the column experiment results, both copper and lead ions could be removed simultaneously by the iron-coated sand in a continuous treatment unit.

ADSORPTIVE CHARACTERISTICS OF CADMIUM AND LEAD ON THE GOETHITE-COATED SAND SURFACE

2001 ◽  
Vol 36 (5) ◽  
pp. 747-763 ◽  
Author(s):  
Chin-Hsing Lai ◽  
Chih-Yu Chen ◽  
Bai-Luh Wei ◽  
Chia-Wei Lee
Keyword(s):  
Sand Surface ◽  
Cadmium And Lead ◽  
Coated Sand

Evaluating an iron-coated sand for removing copper from water

1994 ◽  
Vol 30 (9) ◽  
pp. 175-182 ◽  
Author(s):  
C. H. Lai ◽  
S. L. Lo ◽  
C. F. Lin
Keyword(s):  
Iron Oxide ◽  
Copper Ions ◽  
Packed Column ◽  
Drinking Water Treatment ◽  
Heating Process ◽  
Order Kinetic ◽  
Sand Surface ◽  
Adsorption Equation ◽  
The Media ◽  
Coated Sand

In drinking water treatment systems, the conventional process (coagulation, sedimentation and filtration units) cannot remove trace metals efficiently. Iron oxide is an excellent, regenerable adsorbent, and often controls free metals through adsorption. The utilization of heating process for coating iron oxide on sand surface allowed the media to be used in a packed column. The adsorbent media were investigated for removing copper ions from water using both batch and column experimental methods. A one-dimensional convective-dispersive transport model with a combination of second-order kinetic adsorption equation was adopted for predicting copper retention in a 80 cm depth filter bed. The concentration of copper ions in influent ranged from 0.64 to 3.2 mg/l. The experimental results indicated that the copper could be removed completely until the breakpoint. Once breakthrough occurred, the regeneration of the media could be achieved by soaking with acid solution (pH = 3.0). The simulation results of the transport-adsorption equation fit experimental data quite well. Consequently, the coated sand can be applied for the conventional rapid filtration process to remove copper ions from water.

scholarly journals Chemie an starren Grenzflächen, 8. [1] Kinetik der Heterogenumsetzung kovalent über Spacer an Aerosil gebundener Aminogruppen (Aminoaerosil) mit homogen gelösten Isothiocyanaten / Chemistry on Rigid Interfaces, 8 . [1] Kinetics of Suspensions of Aminoaerosil (Aerosil Covalently Linked with 3-Aminopropylgroups) with Isothiocyanates in Homogeneous Solution

1987 ◽  
Vol 42 (10) ◽  
pp. 1333-1342 ◽  
Author(s):  
L. Horner ◽  
W. Roth
Keyword(s):  
Adsorption Energy ◽  
Homogeneous Solution ◽  
Reaction Rates ◽  
Amino Groups ◽  
Silanol Groups ◽  
Coverage Density ◽  
Covalently Linked ◽  
Kinetics Of

Abstract In aminoaerosil, the products of the reaction of γ-aminopropyltriethoxysilane with aerosil. an intraparticular interaction of the basic amino groups with the acidic silanol groups is observed. This behaviour was established a) by adsorption experiments using n-butylamine on aerosil. resp. aminoaerosil of different support density, and b) by microcalorimetric determination of the adsorption energy of acetonitrile using aerosil and aminoaerosils of different support density as substrates. Aminoaerosils react with isothiocyanates according to (I) with formation of covalently linked thiourea groups. Fig. 3 and Fig. 5 (with trimethylamino) show the time-turnover curves of aminoaerosils of different support density with phenylisothiocyanate. The influence of the tem­perature on the thiourea formation is demonstrated in Table III. Depending on the polarity and the size of the ligands R. the isothiocyanates react with different reaction rates with aminoaerosil (Fig. 6). Aminoaerosils with different coverage density, but with an equal molarity of amino groups and varying specific surfaces, react non-uniformly with phenylisothiocyanate (Table IV). The comparison of the reaction of phenylisothiocyanates a) with heterogeneously by suspended aminoaerosil and b) with n-butylamine in homogeneous solution, both with equal molar amounts of NH2, shows characteristic differences (Fig. 8). The amount of the covalently linked NH2-groups in aminoaerosils can be determined using Sanger’s reagent.

Arsenic(V) Removal by Sulfate Modified Iron Oxide-Coated Sand (SMIOCS) in a Fixed Bed Column

2006 ◽  
Vol 41 (2) ◽  
pp. 157-163 ◽  
Author(s):  
Rakesh Chandra Vaishya ◽  
Sudhir Kumar Gupta
Keyword(s):  
Granular Media ◽  
Fixed Bed ◽  
Water System ◽  
Experimental Conditions ◽  
Fixed Bed Column ◽  
Sand Surface ◽  
Two Parameters ◽  
Coated Sand ◽  
Removal Of Arsenic ◽  
Effective Sorbent

Abstract A novel granular media developed by the coating of iron, barium and sulfur on quartz sand surface has been demonstrated to be an effective sorbent for removal of arsenic(V) from a 0.01 M NaNO3-spiked distilled water system in laboratory-scale tests. The results of fixed bed studies indicate that arsenic(V) removal is dependent on pH, the size of sorbent and influent arsenic concentrations. The particle size of media has shown significant differences in reactor breakthrough times in similar experimental conditions. The removal of As(V) may be explained using the surface complexation theory. The presence of alkalinity (250–260 mg/L as CaCO3) and hardness (200 mg/L as CaCO3) slightly increases reactor breakthrough time for similar experimental conditions without alkalinity and hardness. Desorption studies using 0.2 M NaOH as elutant resulted in nearly 92% recovery of arsenic(V). A theoretical model based on two parameters has shown good correlation with observed experimental data generated during depth variation studies.

scholarly journals Geotechnical characteristics of polystyrene treated sand

2019 ◽  
Vol 92 ◽  
pp. 11015
Author(s):  
Boyeong Yoon ◽  
Jang-un Kim ◽  
Jihwan Lee ◽  
Woojin Lee
Keyword(s):  
Adhesion Force ◽  
Polymeric Materials ◽  
Small Strain ◽  
Geotechnical Properties ◽  
Silica Sand ◽  
Engineering Properties ◽  
Interparticle Contact ◽  
Sand Surface ◽  
Geotechnical Characteristics ◽  
Coated Sand

Many polymeric materials are recently used in geotechnical practice for enhancing the engineering properties of soils. Among the various polymers, this study aims at investigating the geotechnical properties of silica sand coated with polystyrene(PS), which is rarely studied in geotechnical engineering. The polystyrene coated sand was prepared by polymerizing styrene monomer on the surface of silanized sand with median diameter of 0.467 mm. Testing specimens were prepared at 3 different initial relative densities (30, 50 and 70%) by air pluviation. Comprehensive experiments, including one-dimensional compression test with bender elements and triaxial test, were performed to observe the change in geotechnical properties due to the coating of PS on sand surface. The results demonstrate that the adsorbed polymer plays different roles according to strain levels. At very small strain, the polymer on the sand surface may increase the interparticle contact area by applying additional adhesion force between soil particles, leading to an increase in Gmax. However, with an increase in strain level, the polymer will act as the lubricant between sand particles; therefore, the coated sand can show increased compression index and decreased friction angle.

Transport and retention of nanoplastic particles in saturated columns packed with iron oxyhydroxide-coated sand

2020 ◽  
Author(s):  
Taotao Lu ◽  
Benjamin S. Gilfedder ◽  
Sven Frei
Keyword(s):  
Porous Media ◽  
Surface Charge ◽  
Energy Barrier ◽  
Dlvo Theory ◽  
Breakthrough Curves ◽  
Solution Chemistry ◽  
Iron Oxyhydroxide ◽  
Charge Heterogeneity ◽  
Sand Surface ◽  
Coated Sand

<p>With the increasing use of nanoplastic products in our daily life, these particles will invariably enter into the subsurface environment. It is, therefore, vital to understand the transport and retention of nanoplastic particles in groundwater systems. Surface charge heterogeneity is one of the basic chemical-physical characteristics of aquifer materials, but little research has been conducted on this topic. This study aimed to understand how the interaction between the porous media, solution chemistry, and NP surface charge influences the transport and retention of PS-NPs in the subsurface. 25 mg/L polystyrene nanoplastic particles (PS-NPs) were injected into columns packed with iron oxyhydroxide-coated sand. In addition, factors such as the content of iron oxyhydroxide-coated sand (λ), pH, ionic strength (IS), and cation valence were systematically studied. DLVO theory was used to evaluate the interactions between PS-NP and the porous media. By comparing the breakthrough curves (BTCs) of PS-NPs, it was clear that all these variables exerted a significant influence on the mobility of PS-NPs in the columns. These effects could be explained by the following: Firstly, by applying the DLVO theory, it was possible to model the electrostatic interaction between quartz sand and PS-NPs. For instance, at different IS (NaCl), the maximum energy barrier (<em>Φ</em><sub>max</sub>) decreased with an increase in IS, which meant PS-NPs could more easily overcome the energy barrier to deposited on the sand surface at higher IS. Secondly, the positively charged iron oxyhydroxide coating provided additional favorable deposition sites for negatively charged PS-NPs. However, when the pH of the solution exceeded the iron oxyhydroxide pH<sub>pzc</sub> (~pH 9), the iron coating became negative and increased the mobility of PS-NPs. Finally, bridging agents, such as Ca<sup>2+</sup> and Ba<sup>2+</sup>, resulted in the significant deposition of PS-NPs on the sand due to the bridging effect connecting the porous media and PS-NPs through the O-containing functional groups on both plastic and mineral surfaces. This study provides a better understanding of how the charge heterogeneity on aquifer materials and groundwater hydrochemistry affect the transport of PS-NPs in aquifers.</p>

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