scholarly journals Synthesis of Cryolite (Na3AlF6) from Secondary Aluminum Dross Generated in the Aluminum Recycling Process

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3871
Author(s):  
Bingbing Wan ◽  
Wenfang Li ◽  
Wanting Sun ◽  
Fangfang Liu ◽  
Bin Chen ◽  
...  
Keyword(s):  
National Standard ◽  
Molar Ratio ◽  
Recycling Process ◽  
Water Leaching ◽  
Secondary Aluminum ◽  
Co2 Gas ◽  
Aluminum Dross ◽  
Aluminum Recycling ◽  
Ignition Loss ◽  
Polyhedral Shape

Secondary aluminum dross (SAD) is regarded as a solid waste of aluminum recycling process that creates serious environmental and health concerns. However, SAD can also be used as a good source of aluminum, so that utilizing the SAD for the production of valuable products is a promising approach of recycling such waste. In the present work, a novel eco-friendly three-step process was proposed for the synthesis of cryolite (Na3AlF6) from the SAD, and it consisted of (1) water-washing pretreatment of SAD, (2) extraction of Al component via pyro-hydrometallurgy, including low-temperature alkaline smelting, water leaching and purification of leachate in sequence, (3) precipitation of cryolite from the purified NaAlO2 solution using the carbonation method. By analysis of the parameter optimization for each procedure, it was found that the maximum hydrolysis efficiency of aluminum nitride (AlN) in the SAD was around 68.3% accompanied with an extraction efficiency of Al reaching 91.5%. On this basis, the cryolite of high quality was synthesized under the following optimal carbonation conditions: reaction temperature of 75 °C, NaAlO2 concentration of 0.11 mol/L, F/(6Al) molar ratio of 1.10, and 99.99% CO2 gas pressure, and flow rate of 0.2 MPa and 0.5 L/min respectively. The formation of Na3AlF6 phase can be detected by XRD. The morphological feature observed by SEM revealed that the as-synthesized cryolite had a polyhedral shape (~1 μm size) with obvious agglomeration. The chemical composition and ignition loss of the as-synthesized cryolite complied well with the requirements of the Chinese national standard (GB/T 4291-2017).

scholarly journals The Investigation of Optimizing Leaching Efficiency of Al in Secondary Aluminum Dross via Pretreatment Operations

Processes ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1269
Author(s):  
Haigang Feng ◽  
Guofan Zhang ◽  
Qun Yang ◽  
Luobing Xun ◽  
Siyuan Zhen ◽  
...  
Keyword(s):  
Chemical Interaction ◽  
Acid Leaching ◽  
Scanning Electron Micrographs ◽  
Water Leaching ◽  
Secondary Aluminum ◽  
Aluminum Dross ◽  
Process Mineralogy ◽  
Leaching Experiments ◽  
Physical And Chemical ◽  
Leaching Efficiency

Secondary aluminum dross (SAD) is an inevitable by-product from the secondary aluminum industry and has caused serious environmental issues. In this study, the effect of pretreatment operations on the subsequent acid leaching operation was studied by process mineralogy, a series of leaching experiments, XRD, and SEM. Leaching results showed that the leaching efficiency of Al in direct acid leaching was only 22.99%. Process mineralogy showed the complex intertexture and continuous network structure in the SAD. Pretreatment operations were extremely efficient in destroying the structure by physical and chemical interaction. Interestingly, by adding the grinding and water leaching operations, the leaching efficiency of total aluminum in the SAD reached approximately 28.70%. XRD results showed that nearly all metallic Al, AlN, and partial Al2O3 were leached by grinding–water leaching–acid leaching. The scanning electron micrographs showed that the residue particles mainly included some insoluble components and had a smooth surface.

Synthesis of various layered double hydroxides using aluminum dross generated in aluminum recycling process

2012 ◽  
Vol 110-111 ◽  
pp. 46-52 ◽  
Author(s):  
Norihiro Murayama ◽  
Ikuo Maekawa ◽  
Hiroyuki Ushiro ◽  
Takayuki Miyoshi ◽  
Junji Shibata ◽  
...  
Keyword(s):  
Layered Double Hydroxides ◽  
Recycling Process ◽  
Aluminum Dross ◽  
Aluminum Recycling ◽  
Double Hydroxides

scholarly journals Integrated Recycling Process of Matrices of Organic Moulding Sands

2013 ◽  
Vol 58 (3) ◽  
pp. 809-812 ◽  
Author(s):  
R. Dańko
Keyword(s):  
Recycling Process ◽  
Conceptual Approach ◽  
Assessment Index ◽  
Experimental Stand ◽  
Synthetic Resins ◽  
The Matrix ◽  
Ignition Loss ◽  
On Line ◽  
The Given ◽  
Reclamation Process

Abstract The idea and experimental verification of assumptions of the integrated recycling process of matrices of uniform self-hardening moulding sands with synthetic resins, leading to obtaining moulding sands matrix of expected quality - is presented in the hereby paper. The basis of the presented process constitutes a combination of the method of forecasting averaged ignition losses of moulding sands after casting and defining the range of necessary matrix reclamation treatments in order to obtain its full recycling. Simultaneously, the empirically determined dependence of dusts amounts emitted during the reclamation process of the matrix from the given spent sand on the ignition loss values (which is the most proper assessment index of the obtained reclaimed material quality) was taken into account. The special experimental stand for investigations of the matrix recycling process was one of the elements of the conceptual approach and verification of its assumptions. The stand was equipped with the system of current on-line control of the purification degree of matrix grains from organic binder remains. The results of own investigations, allowing to combine ignition loss values of spent moulding sands after casting knocking out with amounts of dusts generated during the mechanical reclamation treatment of such sands, were utilized in the system.

scholarly journals Efficient Separation of Silicon and Vanadium by Sodium Roasting-Water Leaching from Vanadium Slag and CaV2O6 Preparation

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 255
Author(s):  
Changqing Li ◽  
Haichao Zhang ◽  
Ma Tao ◽  
Xufeng Wang ◽  
Hang Li ◽  
...  
Keyword(s):  
New Product ◽  
Molar Ratio ◽  
Migration Behavior ◽  
Vanadium Slag ◽  
Water Leaching ◽  
Solid Ratio ◽  
Leaching Solution ◽  
Micro Morphology ◽  
Precipitation Ratio ◽  
Separation Behavior

Calcium vanadate (CaV2O6), a new product of vanadium precipitation, was obtained from vanadium slag by sodium roasting-water leaching and calcium precipitation. The separation behavior of vanadium and silicon in vanadium slag during sodium roasting and water leaching was systematically studied, and micro-morphology and valence migration behavior of vanadium and Fe in vanadium slag, roasting slag, and residue were revealed. The Na2CO3 was added to the vanadium slag at 20% mass fraction, roasted at 790 ℃, and kept for 120 min, the roasted sample was added to the deionized aqueous solution with a liquid-solid ratio of (L/S) 5mL/g, and then heated at 90 ℃ for 60 min, 89.54% vanadium and 1.96% chromium were extracted. Sodium carbonate tends to combine with vanadium to form sodium vanadate, while silicon is easy to combine with Fe and Na to form acmite (NaFeSi2O6). When the molar ratio of N (Ca/V) is 0.6 and CaO, is added to adjust the pH of vanadium leaching solution to 6.7 ± 0.1 and precipitate 90 min at 90 ℃, vanadium is precipitated in the form of CaV2O6 with a purity of 95.69%, under these conditions, the precipitation ratio is 95.03%.

scholarly journals Faktor-Faktor yang Mempengaruhi Produksi Biodiesel dari Minyak Sawit Mentah Menggunakan Katalis Padat Kalsium Karbonat yang Dipijarkan

2012 ◽  
Vol 11 (2) ◽  
pp. 129 ◽  
Author(s):  
Amir Awaluddin ◽  
Saryono ' ◽  
Sri Nelvia ◽  
Wahyuni '
Keyword(s):  
Methyl Esters ◽  
National Standard ◽  
Molar Ratio ◽  
High Price ◽  
Homogeneous Catalyst ◽  
World Population ◽  
Crude Palm Oil ◽  
Factors Affecting ◽  
Acid Catalyzed ◽  
Edible Type

The demand for petroleum has increased recently due to the increase of world population, industries andtransportation. Biodiesel (fatty acids methyl esters) has become attractive because of high price of petroleum,limited recourses of crude oil, and environmental concerns. Most biodiesel is produced by transesterification oftriglycerides of refined/edible type oils using methanol and homogeneous catalyst such NaOH and KOH. The useof heterogeneous calcined CaCO3 catalyst, has advantages such as the ease of phase separation betweencatalyst and biodiesel. This paper presents factors affecting the synthesis of biodiesel from crude palm using thecalcined CaCO3 catalyst . The synthesis is carried out by two steps, the acid-catalyzed pre-esterification of free-fatty acid and followed by base-catalyzed transesterification of triglycerides. A study of optimizing the reactioncondition of the esterification followed by transesterification of crude palm oil (CPO) is performed to obtainmaximum production of biodiesel. Under conditions of catalyst calcination temperature of 9000C, reactor time of1.5 hours, catalyst dosage of 1,5%, reaction temperature of 700C and methanol/oil molar ratio of 9 : 1, the oilconversion is 74,6%. The as-synthesized biodiesel meets the requirements of Indonesian National Standard (SNI)for biodiesel.

scholarly journals Linking the lithogenic, atmospheric, and biogenic cycles of silicate, carbonate, and organic carbon in the ocean

2009 ◽  
Vol 6 (4) ◽  
pp. 6579-6599
Author(s):  
S. V. Smith ◽  
J.-P. Gattuso
Keyword(s):  
Carbon Storage ◽  
Chemical Weathering ◽  
Dissolved Inorganic Carbon ◽  
North Pacific Ocean ◽  
Atmospheric Co2 ◽  
Molar Ratio ◽  
Co2 Uptake ◽  
Organic C ◽  
Co2 Gas ◽  
The Relationship

Abstract. Geochemical theory describes long term cycling of atmospheric CO2 between the atmosphere and rocks at the Earth surface in terms of rock weathering and precipitation of sedimentary minerals. Chemical weathering of silicate rocks takes up atmospheric CO2, releases cations and HCO3− to water, and precipitates SiO2, while CaCO3 precipitation consumes Ca2+ and HCO3− and releases one mole of CO2 to the atmosphere for each mole of CaCO3 precipitated. At steady state, according to this theory, the CO2 uptake and release should equal one another. In contradiction to this theory, carbonate precipitation in the present surface ocean releases only about 0.6 mol of CO2 per mole of carbonate precipitated. This is a result of the buffer effect described by Ψ, the molar ratio of net CO2 gas evasion to net CaCO3 precipitation from seawater in pCO2 equilibrium with the atmosphere. This asymmetry in CO2 flux between weathering and precipitation would quickly exhaust atmospheric CO2, posing a conundrum in the classical weathering and precipitation cycle. While often treated as a constant, Ψ actually varies as a function of salinity, pCO2, and temperature. Introduction of organic C reactions into the weathering-precipitation couplet largely reconciles the relationship. ψ in the North Pacific Ocean central gyre rises from 0.6 to 0.9, as a consequence of organic matter oxidation in the water column. ψ records the combined effect of CaCO3 and organic reactions and storage of dissolved inorganic carbon in the ocean, as well as CO2 gas exchange between the ocean and atmosphere. Further, in the absence of CaCO3 reactions, Ψ would rise to 1.0. Similarly, increasing atmospheric pCO2 over time, which leads to ocean acidification, alters the relationship between organic and inorganic C reactions and carbon storage in the ocean. Thus, the carbon reactions and ψ can cause large variations in oceanic carbon storage with little exchange with the atmosphere.

scholarly journals Tetraethylammonium Acetate and Tetraethylammonium Bromide-Based Deep Eutectic Solvents as Thermodynamic CO2 Gas Hydrate Inhibitors

2020 ◽  
Vol 10 (19) ◽  
pp. 6794
Author(s):  
Vinayagam Sivabalan ◽  
Nurasyikin Hasnor ◽  
Bhajan Lal ◽  
Zamzila Kassim ◽  
Abdulhalim Shah Maulud
Keyword(s):  
Hydrogen Bond ◽  
Ethylene Glycol ◽  
Gas Hydrate ◽  
Deep Eutectic Solvents ◽  
Molar Ratio ◽  
Tetraethylammonium Bromide ◽  
Hydrate Dissociation ◽  
Co2 Gas ◽  
Vapor Equilibrium ◽  
Liquid Vapor

The thermodynamic gas hydrate suppression behavior of four Deep Eutectic Solvents (DESs) was evaluated in this paper. The mixtures of Hydrogen Bond Acceptors (HBA), Tetraethylammonium Acetate (TEAAC), and Tetraethylammonium Bromide (TEAB) with Hydrogen Bond Donors (HBD), Mono-Ethylene Glycol (MEG), and Glycerol were used to make the DES. The DESs were made at a 1:7 molar ratio for the combinations of TEAAC:MEG, TEAAC:Glycerol, TEAB:MEG, and TEAB:Glycerol. The Hydrate Liquid-Vapor Equilibrium (HLVE) data for CO2 were evaluated through the T-cycle method at different temperature (273.15–283.15 K) and pressure (2–4 MPa) conditions in the presence and absence of 5 wt % aqueous DES solutions. The inhibition effects showed by the DESs, including average suppression temperature (ΔŦ) and gas hydrate dissociation enthalpies (ΔHdiss), were also calculated. The average suppression temperature values of the DESs ranged between 0.4 and 2.4, with the highest inhibition to lowest inhibition order being TEAB:Glycerol > TEAB:MEG > TEAAC:Glycerol > TEAAC:MEG. A comparison of the DES with conventional Thermodynamic Hydrate Inhibitors (THIs) showed that studied Deep Eutectic Solvents had better gas hydrate inhibition. The results proved that DES has the potential to be one of the promising alternatives in gas hydrate inhibition.

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