Mechanistic study of the calcination process in magnesium production: Application of the Darcy-Clausius coupling model for improving environmental efficiency.

In the process of industrialization, it is found that the calcination process is an important factor affecting the reduction rate, which determines the energy consumption and carbon emission of the reaction process. In this study, the micro-nano physical model of the factors affecting the reduction rate of calcined precursors was constructed by coloring the SEM results of pellets before and after calcination with Gaussian height expression and combining Clausius and Gibbs equations. The influence of the formation degree of the internal pores of the pellets on the reduction rate was analyzed by controlling the calcination time of the precursor.

The Customized Heat Treatment for Enhancing the High-Temperature Durability of Laser-Directed Energy Deposition-Repaired Single-Crystal Superalloys.

The high-temperature durability performance plays a crucial role in the applications of single-crystal (SX) superalloys repaired by laser-directed energy deposition (L-DED). A specialized heat treatment process for L-DED-repaired SX superalloys was developed in this study. The effect of the newly customized heat treatment on the microstructure and high-temperature mechanical properties of DD32 SX superalloy repaired by L-DED was investigated.

Preparation of polyamidoamine dendrimer-functionalized chitosan beads for the removal of Ag(I), Cu(II), and Pb(II).

Chitosan bead grafted by third-generation dendrimers (CB-G3) with a diameter of 1.40 mm was synthesized to investigate their performance in recovering Ag(I), Cu(II), and Pb(II) ions in aqueous media. The prepared adsorbents were characterized by XRD, FT-IR, elemental analysis, TGA, and SEM, and the effects of pH, contact time, concentration, and temperature were examined.

A comprehensive review of aluminium electrolysis and the waste generated by it.

Aluminium is produced by electrolysis using alumina (AlO) as raw material and cryolite (NaAlF) as electrolyte. In this Hall-Héroult process, the energy consumption is relatively large, and solid wastes such as spent anodes and spent pot liner, flue gas and waste heat are generated. Therefore, this article discusses from the perspective of high energy consumption and high pollution and summarizes the methods to reduce energy consumption and solve pollution problems.

Summary of research progress on separation and extraction of valuable metals from Bayer red mud.

Bayer red mud is a strong alkaline solid waste discharged during alumina production. Due to large emissions and strong alkalinity, red mud is now mostly dammed or buried, which not only occupies huge land but also contaminates the surrounding ecosystem, causing the risk of collapse and landslide. In addition to its overall utilization in building materials, agriculture, the environment, and the chemical industry, red mud also contains valuable metals such as sodium, aluminum, iron, titanium, and scandium and is considered to be an important secondary resource.

Removal of Cr(VI) and Ag(I) by grafted magnetic zeolite/chitosan for water purification: Synthesis and adsorption mechanism.

In this paper, a novel grafted zeolite/FeO/chitosan (ZMC-MAH-TEPA) adsorbent was greenly synthesized and evaluated for the removal of Cr(VI) and Ag(I) in single and bi-component solutions. The characterization data of XRF, XRD, FT-IR, VSM, TGA, BET and SEM showed the successful fabrication of the adsorbent with abundant -NH and -NH- as well as great recovery properties (11.70 emu/g).

Research on the Dealkalization Treatment of Bauxite Residue and Deep Extraction of Alumina.

Bauxite residue is the bulk solid waste generated by the alumina industry, and the environmental treatment of bauxite residue has always been a focus of attention. In this study, in the high calcium system, the bauxite residue was intensively digestion by the calcification-carbonation method, and the mole ratio of solution, the mass ratio of CaO/SiO of the digestion process were changed, so that the high-efficiency dealkalization of bauxite residue was realized and the aluminum oxide in bauxite residue was deeply extracted. The experimental results showed that the calcification process could achieve the recovery of 17.

Research on the mechanism of sodium separation in bauxite residue synergy preparation of potassium-containing compound fertilizer raw materials by the hydrothermal method.

Bauxite residue poses an increasingly serious ecological safety problem in the alumina industry. A novel process for removing sodium in bauxite residue synergistic preparation of potassium-containing compound fertilizer raw materials was proposed to relieve pressure on the fertilizer industry. In this paper, synthetic sodalite and katoite were used to simulate the main mineral phases of bauxite residue to determine the suitable conditions for the method, and the transformation mechanism of the process was researched by analyzing the phase structure and microscopic morphology of the samples using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and specific surface area detection.

Study on Iron Extraction from High Iron Bauxite Residue by Pyrite Reduction.

A new method of solid-phase reduction magnetic separation with pyrite as a reducing agent was proposed in order to realize resource utilization of high iron bauxite residue while reducing environmental harm. FeS powder and high iron bauxite residue powder were uniformly blended and roasted in a closed environment. A magnetic separator was utilized to separate the magnetic iron concentrate at 2400 GS, and the recovery rates were calculated.

Calcification-Carbonation Method for Bayer Red Mud Treatment: Carbonation Performance of Hydrogarnets.

Hydrogarnets are vital intermediate products in the calcification- carbonation method, which is designed for Bayer red mud treatment. Their carbonation performance greatly depends on SiO substitution. In this study, different SiO-substituted hydrogarnets were synthesized and characterized.

Extraction and Utilization of Valuable Elements from Bauxite and Bauxite Residue: A Review.

Bauxite is the ideal raw material for the manufacturing of alumina. Aside from the primary constituents of aluminum and silicon, bauxite is frequently coupled with many valuable elements such as gallium (Ga), titanium (Ti), scandium (Sc), and lithium (Li). The bauxite residue and circulating spent liquor in alumina production typically include significant amounts of valuable elements, making them a potential source of polymetallic.

Experimental Research on Vortex Melting Reduction of High-Iron Red Mud (Bauxite Residue).

In this study, the advantages of the vortex melting reduction treatment of red mud were verified. Vortex melting reduction can improve the feeding rate, promote the reaction and the directional deposition of iron, which was conducive to the separation of slag and gold. The effects of different adding methods, stirring speed and reaction time on iron recovery were investigated by using red mud, aluminum leached slag and calcified slag as raw materials.

Comprehensive Application Technology of Bauxite Residue Treatment in the Ecological Environment: A Review.

The emission of bauxite residue continues to grow with the increase of alumina production capacity, along with the large amounts of bauxite residue currently stored in stockpiles. The exposed problems of high yield, strong alkalinity, low comprehensive utilization rate, and threats to the ecological environment are becoming increasingly prominent. With the strict requirements of environmental protection, improving the comprehensive utilization rate of bauxite residue and bulk consumption of bauxite residue has become an urgent issue to be solved.

Green method to synthesize magnetic zeolite/chitosan composites and adsorption of hexavalent chromium from aqueous solutions.

This paper aims to synthesis a recyclable adsorbent from solid waste using a clean and environmentally friendly method to deal with Cr(VI) water pollution. Magnetic zeolite/chitosan composites (ZFA/MCS) were prepared by the neutralization method. The adsorption properties of ZFA/MCS, prepared by the neutralization method for Cr(VI) ions under different conditions especially cross-linking, were investigated in detail.

Simultaneous separation of Fe & Al and extraction of Fe from waste coal fly ash: Altering the charge sequence of ions by electrolysis.

A significant amount of coal fly ash is generated and this type of waste material causes severe environmental hazards. Metal (Al and Fe) extraction from coal fly ash is beneficial to the resource utilization of waste coal fly ash. However, the coexistence of Al and Fe in coal fly ash means that the separation of Al and Fe is required, which is a key and difficult step to prepare high value-added products from coal fly ash.

Research on the oxidation characteristics of zinc sulfite in the zinc oxide desulfurization process.

Aiming at the pollution problem of low-content SO in non-ferrous metal production industry, the oxidation kinetics of zinc sulfite in the zinc oxide desulfurization process was studied. The concentration change of Zn, variation of pH, temperature and apparent activation energy in the oxidation process of two ZnSO samples were investigated systematically. The results indicate that the raw material with different crystal water has little effect on the oxidation kinetic of zinc sulfite.

Clean production of porous-Al(OH) from fly ash.

Fly ash is one of the largest solid waste and causes serious environment problems. Extraction of Al(OH) from fly ash is beneficial to environment and economy. We developed a clean electrolysis method to generate hydroxyl groups in situ to extract Al(OH) from fly ash leachate without adding chemicals or using expensive membranes, avoiding the introduction of new impurities, secondary pollutants generation, and membrane limitations.

A perspective of stepwise utilization of hazardous zinc plant purification residue based on selective alkaline leaching of zinc.

A new route for selective recovery of zinc from hazardous zinc plant purification residue was proposed by alkaline leaching process. The thermodynamic analysis revealed that by controlling solution pH in the range from 14.30 to 16.

Recovery of vanadium from calcification roasted-acid leaching tailing by enhanced acid leaching.

Vanadium contained tailing generated from the typical calcium roasting-acid leaching process is contaminant and waste of resource. Atmospheric and pressurized leaching were conducted and compared to recover the vanadium from the vanadium tailing and improve the tailing's environmental quality. Orthogonal experiments were designed and applied for the atmospheric leaching study.

Magnetic resonance imaging appearance of well-differentiated hepatocellular carcinoma.

Objective: To investigate the magnetic resonance imaging (MRI) features of well-differentiated hepatocellular carcinoma (HCC).

Methods: We reviewed the MRI of 32 patients with 33 pathologically confirmed well-differentiated HCC. The MRI protocol included T2-weighted imaging with and without fat saturation, dual-phase T1-weighted imaging, and gadolinium-enhanced dynamic study.

Metastases from gastric carcinoma to colon in the form of multiple flat elevated lesions: a case report.

Gastric carcinoma is a common malignancy worldwide. Advanced stages of the disease may result in metastases to many other organs of the body. However, colonic metastases are rare.