scholarly journals Methods to Improve nZVI Adsorbance on Silicates Surface for Nitrate Reduction

2021 ◽  
Author(s):  
◽  
Handayani Fraser
Keyword(s):  
Silica Fume ◽  
Western Australia ◽  
Column Experiment ◽  
Exchangeable Cation ◽  
Sand Column ◽  
Silica Surfaces ◽  
Pure Silica ◽  
Acid Washing ◽  
Silicate Surface ◽  
Aluminium Silicate

<p>Efforts to remove excess nitrate in the groundwater typically involves expensive ion-exchange membranes or slow reacting bio-reactors. Nano-sized zero valent iron (nZVI) has been used successfully to reduce nitrate into ammonia in various sites in USA and Europe. However, nZVI has a number of major setbacks associated with it, namely the tendency to agglomerate due to magnetic properties, and the possible toxicity due to the nano-sized material.  To circumvent these two setbacks, nZVI could be adsorbed onto solid support. In this research, geothermal sediment microsilicate 600 (Misi) was utilised as a support. Initial results suggested that Misi has potential as a support for nZVI, however modifications were required to improve the adsorbance of nZVI onto Misi surface. Calcination, activation, acid wash and iron oxyhydroxide coating were used as surface modifications for Misi. It was found that the two most important modifications for nZVI adsorption was calcination at either 400 or 600 °C and acid washing in 5.6 M HCl.  Equipped with this knowledge, other silica and silicates were also used to adsorb nZVI. For pure silica surfaces, 3-APTES and 3-TPTMS ligands and pore enlarging methods of calcination of porogen and salt wash were also used. nZVI was not able to be fully adsorbed on pure silica surfaces. Four other silicates were examined: Rice husk ash, Western Australia silica fume, Mt Piper fly ash, and precipitated aluminium silicate. Of these, only Western Australia silica fume and precipitated aluminium silicate showed potential as nZVI support. Based on the SEM-EDS XRD data of all the silica and silicates, it could be tentatively concluded that nZVI requires an aluminium silicate surface for successful adsorption. Aluminium silicate surfaces typically has an exchangeable cation present, and this cation might play a part in nZVI adsorption.  The nZVI/Misi surface was then utilised to reduce nitrate. It was discovered that even though activation and FeOOH did not play a part in nZVI adsorption onto Misi surface, these two steps were important in reduction of nitrate, as the presence of activation and FeOOH increase the reduction of nitrate significantly within 60 minutes. The Misi-supported nZVI were also shown to be more stable in dispersion, and less agglomerated as shown in a sand column experiment.</p>

scholarly journals Methods to Improve nZVI Adsorbance on Silicates Surface for Nitrate Reduction

2021 ◽  
Author(s):  
◽  
Handayani Fraser
Keyword(s):  
Silica Fume ◽  
Western Australia ◽  
Column Experiment ◽  
Exchangeable Cation ◽  
Sand Column ◽  
Silica Surfaces ◽  
Pure Silica ◽  
Acid Washing ◽  
Silicate Surface ◽  
Aluminium Silicate

<p>Efforts to remove excess nitrate in the groundwater typically involves expensive ion-exchange membranes or slow reacting bio-reactors. Nano-sized zero valent iron (nZVI) has been used successfully to reduce nitrate into ammonia in various sites in USA and Europe. However, nZVI has a number of major setbacks associated with it, namely the tendency to agglomerate due to magnetic properties, and the possible toxicity due to the nano-sized material.  To circumvent these two setbacks, nZVI could be adsorbed onto solid support. In this research, geothermal sediment microsilicate 600 (Misi) was utilised as a support. Initial results suggested that Misi has potential as a support for nZVI, however modifications were required to improve the adsorbance of nZVI onto Misi surface. Calcination, activation, acid wash and iron oxyhydroxide coating were used as surface modifications for Misi. It was found that the two most important modifications for nZVI adsorption was calcination at either 400 or 600 °C and acid washing in 5.6 M HCl.  Equipped with this knowledge, other silica and silicates were also used to adsorb nZVI. For pure silica surfaces, 3-APTES and 3-TPTMS ligands and pore enlarging methods of calcination of porogen and salt wash were also used. nZVI was not able to be fully adsorbed on pure silica surfaces. Four other silicates were examined: Rice husk ash, Western Australia silica fume, Mt Piper fly ash, and precipitated aluminium silicate. Of these, only Western Australia silica fume and precipitated aluminium silicate showed potential as nZVI support. Based on the SEM-EDS XRD data of all the silica and silicates, it could be tentatively concluded that nZVI requires an aluminium silicate surface for successful adsorption. Aluminium silicate surfaces typically has an exchangeable cation present, and this cation might play a part in nZVI adsorption.  The nZVI/Misi surface was then utilised to reduce nitrate. It was discovered that even though activation and FeOOH did not play a part in nZVI adsorption onto Misi surface, these two steps were important in reduction of nitrate, as the presence of activation and FeOOH increase the reduction of nitrate significantly within 60 minutes. The Misi-supported nZVI were also shown to be more stable in dispersion, and less agglomerated as shown in a sand column experiment.</p>

The surface energies of cation substituted Laponite

Clay Minerals ◽  
1993 ◽  
Vol 28 (1) ◽  
pp. 1-11 ◽  
Author(s):  
J. Norris ◽  
R. F. Giese ◽  
P. M. Costanzo ◽  
C. J. van Oss
Keyword(s):  
Divalent Cations ◽  
Contact Angles ◽  
Lewis Base ◽  
Silicate Layer ◽  
Natural Material ◽  
Exchangeable Cation ◽  
Monovalent Cations ◽  
Liquid Drops ◽  
Glass Slides ◽  
Silicate Surface

AbstractLaponite RD forms stable, coherent films which adhere strongly to glass slides. Such films are capable of supporting liquid drops allowing the direct measurement of contact angles for five liquids of which, two were apolar (0:-bromonaphthalene and diiodomethane) and three were polar (water, formamide, glycerol); surface tension components and parameters (γLw, γ⊕ and γ⊖) were determined by solving the Young equation. These determinations were made for homoionic samples saturated with Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba and NH4 as well as the natural material. Whereas the values of γLw (the apolar Lifshitz-van der Waals component) varied only within narrow limits (41-44 mJ/m2), the Lewis base parameter varied comparatively widely (24-41 mJ/m2). The Lewis acid parameter was small and relatively constant (1·3-3·0 mJ/m2). The variation of γ⊖ as a function of the exchangeable cation suggests that the divalent cations are shielded from the silicate surface by the water molecules of their sphere of hydration, whereas the monovalent cations are in direct contact with the oxygen atoms of the silicate surface. Furthermore, the divalent cations may screen the Lewis base sites to a greater degree than do the monovalent cations. Lithium behaves anomalously and this may indicate that it physically enters into the ditrigonal hole in the silicate layer.

Fabrication of Silver Shells onto Silica Sphere for Infrared Emissivity

2012 ◽  
Vol 479-481 ◽  
pp. 541-545 ◽  
Author(s):  
Xiao Yun Ye ◽  
Chan Zheng ◽  
Xue Qing Xiao ◽  
Shu Guang Cai
Keyword(s):  
Infrared Emissivity ◽  
Cycle Times ◽  
Silica Surfaces ◽  
Composite Microspheres ◽  
Pure Silica ◽  
Seeding Method ◽  
Structures And Properties ◽  
Strong Reflection ◽  
Ft Ir ◽  
Shell Composite

SiO2/Ag core-shell composite microspheres were synthesized by silver-seeding method in this paper. In the process, silver nanoparticles as seeds were deposited by repeating the cycle times for further formation of Ag shell. The effects of reaction power and time on the seeding of silica surfaces and the effect of silver ion on the growth of silver shells were investigated. Structures and properties were measured with TEM, UV, FT-IR and Infrared emissometer. The results showed the Ag nanoparticles on the silica surfaces were uniform in size. And the number density was increased growing with the increase of deposition. It was found that the composite exhibited a lower infrared emissivity value in the wavelength range from 8 to 14 μm than that of pure silica as a result of strong reflection of silver metal.

scholarly journals Heavy metals removal from landfill leachate by coagulation/flocculation process combined with continuous adsorption using eggshell waste materials

2021 ◽  
Author(s):  
A. Q. Jaradat ◽  
Dua'a B. Telfah ◽  
Rabah Ismail
Keyword(s):  
Heavy Metals ◽  
Landfill Leachate ◽  
Agricultural Waste ◽  
Column Experiment ◽  
Waste Materials ◽  
Optimum Dose ◽  
Sand Column ◽  
Heavy Metals Removal ◽  
Metals Removal ◽  
Eggshell Waste

Abstract The use of agricultural waste materials to remove heavy metals from wastewater is attractive due to its simplicity and economic efficiency. In this study, the applicability of calcined eggshell waste materials (CES) for heavy metals removal from real wastewater were examined via transport column experiment preceded by coagulation/flocculation process.A column packed with granular activated carbon (GAC) is operated in parallel to CES column to evaluate the adsorptive attributes of CES. The findings are assessed from another set of column experiment consisting of sand followed by CES column to evaluate the effect of particulate matter on CES performance toward heavy metals removal. In coagulation experiment, alum addition at an optimum dose (3.0 g/L) reduced the total suspended solids (TSS) by 80%, whereas the Fe, Pb, Zn, Cu, Ni, and Cr were reduced by 80, 77, 76, 73, 56, and 49% respectively. Under the current applied hydrodynamic conditions, using sand column before CES column improved the removal efficiencies of Fe, Pb, Cu, Zn, Ni, and Cr from 50–92%, 55–93%, 60–87%, 53–76%, 45–65%, and 41–60% respectively. The whole results illustrate that CES can be competitive to GAC for heavy metals removal from landfill leachate, mainly if applied after PM removal by sand filtration.

The degradation of highly concentrated organic wastewater by the sand layer method

1997 ◽  
Vol 35 (8) ◽  
pp. 223-229
Author(s):  
Masatomo Nakayama ◽  
Keijiro Enari
Keyword(s):  
Waste Water ◽  
Organic Waste ◽  
Lower Layer ◽  
Removal Rate ◽  
Column Experiment ◽  
Sand Layer ◽  
Biological Degradation ◽  
Sand Column ◽  
Methanogenic Activity ◽  
Seed Sludge

The osmotic action of highly concentrated organic waste water through soil was investigated by a column experiment. In this experiment, 50cm high sand-filled columns were used. The experiment included to estimate the toxic effects of mercury on the biological degradation of highly concentrated organic waste water. By adding seed sludge to the top of the sand column, 90% of the TOC was removed. The TOC was removed within the first 20-30cm of the sand layer. Though the removal rate of T-N was low, the T-P removal rate was over 86%. The effect of mercury on the removal of TOC, T-N, and T-P was not marked in either case. Both the acidogenic activity and the methanogenic activity were measured, and they showed higher values in the upper layer compared with the lower layer. The values of these activities were low in the column experiment with mercury.

Column Experiment on Cr (VI) Reduction with SiO2-Coated Fe Nanocomposites

2013 ◽  
Vol 690-693 ◽  
pp. 1041-1044
Author(s):  
Yong Chao Li ◽  
Ke Jia Liu ◽  
Bo Zhi Ren
Keyword(s):  
Groundwater Remediation ◽  
Open Systems ◽  
Column Experiment ◽  
Deionized Water ◽  
Coupling Agents ◽  
Saturated Sand ◽  
Sand Column ◽  
Reactive Material ◽  
Water Saturated

SiO2-coated Fe nanocomposites (Fe@SiO2) were prepared without using any of surface-coupling agents. The outer SiO2 coating offered new possibilities for the control of Fe core agglomeration. In order to investigate Cr (VI) reduction in open systems that simulated subsurface conditions, sand column experiments were conducted. When 10 mg/L of Cr (VI) was injected into the columns, the removal efficiencies of Cr (VI) by the Fe@SiO2 were 65 mg Cr/g Fe. The transport tests in deionized water-saturated sand columns indicated that 88.03% of Fe@SiO2 was eluted. Nonetheless, the mobility of Fe@SiO2 decreased when encountering 10 mmol/L Na+ and Ca2+. Presumably, 15 mg/L humic acid enhanced the mobility of Fe@SiO2. Overall, the results of this study indicate that Fe@SiO2 has the potential to become an effective reactive material for in situ groundwater remediation.

Conditions for atomic imaging of mullite

1989 ◽  
Vol 47 ◽  
pp. 418-419
Author(s):  
T. A. Epicier ◽  
G. Thomas
Keyword(s):  
Oxygen Vacancies ◽  
High Resolution Electron Microscopy ◽  
Ceramic Materials ◽  
Work Conditions ◽  
Real Space ◽  
Potential Candidate ◽  
Silicate Mineral ◽  
Resolution Electron ◽  
The Subject ◽  
Aluminium Silicate

Mullite is an aluminium-silicate mineral of current interest since it is a potential candidate for high temperature applications in the ceramic materials field.In the present work, conditions under which the structure of mullite can be optimally imaged by means of High Resolution Electron Microscopy (HREM) have been investigated. Special reference is made to the Atomic Resolution Microscope at Berkeley which allows real space information up to ≈ 0.17 nm to be directly transferred; numerous multislice calculations (conducted with the CEMPAS programs) as well as extensive experimental through-focus series taken from a commercial “3:2” mullite at 800 kV clearly show that a resolution of at least 0.19 nm is required if one wants to get a straightforward confirmation of atomic models of mullite, which is known to undergo non-stoichiometry associated with the presence of oxygen vacancies.Indeed the composition of mullite ranges from approximatively 3Al2O3-2SiO2 (referred here as 3:2-mullite) to 2Al2O3-1SiO2, and its structure is still the subject of refinements (see, for example, refs. 4, 5, 6).

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