Alkaline Roasting Research Articles

Effects of Preheating and Alkaline Roasting on Gangue Removal During the Alkaline Hydrothermal Treatment of Low-Grade Iron Ores

Effects of Preheating and Alkaline Roasting on Gangue Removal During the Alkaline Hydrothermal Treatment of Low-Grade Iron Ores

Kinetics Study on Microwave Alkaline Roasting-Water Dissolving of Germanium from Zinc Oxide Dust

Abstract Zinc hydrometallurgy plants produce large amounts of germanium (Ge)-containing zinc oxide (ZnO) dust during the production process. However, the present leaching percentages of Ge by the sulfuric leaching process from ZnO dust are generally lower than 60%. Thus, a novel process of microwave alkaline roasting followed by water dissolving is proposed to further improve Ge extraction from ZnO dust, and the kinetic behaviors and related theoretical models are studied. Perhaps it can be promoted Ge leaching percentages by water after microwave alkaline roasting, the dissolving reaction kinetics follow the diffusion control model, and the apparent activation energy is 15.46 kJ/mol.

Processing of waste (tails) after flotation of copper production slag to obtain iron oxide pigment

At this work, the processing of waste after flotation of copper production slag to obtain iron oxide pigment is presented. Based on the results of the experiments, the influence of various factors and parameters on the processing of iron-containing waste (tailings) of the copper concentration plant-2 of the AMMC was studied; This approach is both uncomplicated and efficient for extracting Fe2O3, which is regarded as a primary ingredient in the manufacturing of iron pigment. It was found that when caustic soda is used for alkaline roasting, the iron oxides in the tailings react with nitrates and hydrates to form an insoluble solid phase. Additionally, it was discovered that firing temperatures above 350 °C result in the formation of a sodium aluminate compound. This compound and the iron compounds dissolve in solutions and negatively affect the quality of the resulting Fe2O3 pigment.

Purification of Waste Graphite from Crucibles Used in Photovoltaic Crystallization by an Alkali-Acid Method

The photovoltaic industry generates large amounts of waste graphite (WG) that contains useful metals that can be recycled into high-value products. This study elucidated the impurity elements and their existence states in WG, analyzed and verified the source of the main impurity phase SiC, and determined the SiC content to be 4.66%. WG was purified using an alkaline-acid method, whose optimal process parameters were a solid alkali ratio of 3, calcination temperature of 600 °C, calcination time of 120 min, HCl concentration of 1 M, and acid leaching time of 40 min. Under these conditions, a graphite product with a fixed carbon content of 98.45% was obtained. Impurities were determined to migrate via three pathways: (1) Most main elements (Al, K, and Si) in silicates were removed by alkaline roasting, while the remaining elements were dissolved in acid. (2) Impurities containing metal elements such as Fe, Mg, Ca, and Zn were decomposed in NaOH to form hydroxides or oxides that were dissolved in HCl. (3) Silicon carbide impurities were removed by the alkaline-acid method without decomposition and often existed with graphite in the acid-leaching slag.

Study on separation of N, F and Al from hazardous aluminum dross by alkaline roasting

Study on separation of N, F and Al from hazardous aluminum dross by alkaline roasting

Methods of Extracting TiO2 and Other Related Compounds from Ilmenite

Although ilmenite and rutile are extensively used to extract TiO2 at the industrial level, through the sulphate and chloride processes, they can also be recognized to possess the potential to be employed as the raw material to synthesize other titanium compounds as well. The Pulmoddai mineral sand deposit in Sri Lanka is considered as a valuable resource containing pure ilmenite and can be used as a very good source of both titanium and iron. Because of the lower TiO2 content compared to rutile, processes, such as the Becher process, Laporte process and Kataoka process, have been developed to upgrade ilmenite into higher grade synthetic rutile. Additionally, research studies have been carried out to develop methods, such as the hydrochloride process, H3PO4/NH3 process, alkaline roasting process, aluminothermic reduction method, alkaline decomposition method, molten salt electroreduction method and magnesiothermic reduction method, to synthesize TiO2 and other related titanium compounds, such as titanium and iron oxides, composites and alloys, from naturally occurring ilmenite where these methods possess both rewards as well as drawbacks over the others.

Two-step harmless treatment of secondary aluminum dross (SAD) by vacuum distillation and alkaline roasting

Two-step harmless treatment of secondary aluminum dross (SAD) by vacuum distillation and alkaline roasting

Optimization of Alkaline Roasting to Enable Acid Leaching of Titanium from Anatase Ores

Optimization of Alkaline Roasting to Enable Acid Leaching of Titanium from Anatase Ores

Niobium and tantalum recovery from the primary source and from tin slag, an industrial challenge: A review

AbstractNiobium (Nb) and Tantalum (Ta) are used to increase materials' mechanical resistance and produce lighter alloys. Worldwide Nb production reached 78 000 t in 2020. The reduced ore offer justifies the recycling of these metals from tin slag, contributing to the circular economy. Nb2O5 and Ta2O5 extraction either from the primary source or the tin slag is an industrial challenge. Nb and Ta dissolution processes already implemented are fluoride leaching, sulphuric leaching, alkaline leaching, and alkaline roasting. The fluoride process raises environmental concerns about waste control. The sulphuric method can be managed to have higher Nb and Ta extraction in a less aggressive process, if some changes are implemented, such as increasing the number of extraction steps, decreasing the pulp density, or increasing the temperature; however, the efficiency of this methodology must be tested for tin slag. The alkaline method seems to be more selective to Nb and Ta by reactants and temperature control. Despite those well‐established Nb and Ta treatments, they must be adapted to recover Nb and Ta from slag. The slag has low Nb and Ta content, while high Si and Ca concentrations exist in the matrix. This paper brings the main methods used to extract the Nb and Ta from the primary resources and an overview of Nb and Ta recovery from the slag. This investigation comes as a tool to guide the development of new methods to recover Nb and Ta from low‐grade sources such as tin slag.

Efficient Extraction of Ta and Nb from a Coltan Ore Through Alkaline Roasting, Water Leaching, Precipitation, and Oxalic Acid Leaching

Efficient Extraction of Ta and Nb from a Coltan Ore Through Alkaline Roasting, Water Leaching, Precipitation, and Oxalic Acid Leaching

Effective Extraction of the Al Element from Secondary Aluminum Dross Using a Combined Dry Pressing and Alkaline Roasting Process.

Secondary aluminum dross (SAD) is a hazardous solid waste discharged from aluminum electrolysis and processing and the secondary aluminum industries, which causes severe environmental pollution and public health disasters. The stable presence of the α-Al2O3 and MgAl2O4 phases in SAD makes it difficult for it to be efficiently utilized. A combined dry pressing and alkaline roasting process was proposed for extracting the valuable Al element from SAD. Two alkaline additives (NaOH and Na2CO3) were selected as a sodium source for extracting the aluminum source from SAD in order to perform the thermodynamic analysis and roasting experiments. The phase transition behavior and the leaching performance tests were conducted using X-ray diffraction, scanning electron microscopy, X-ray fluorescence, leaching kinetics and thermal analysis. The recovery of Al and Na reached the values of 90.79% and 92.03%, respectively, under the optimal conditions (roasting temperature of 1150 °C, Na2CO3/Al2O3 molar ratio of 1.3, roasting time of 1 h, leaching temperature of 90 °C, L/S ratio of 10 mL·g−1 and leaching time of 30 min). Meanwhile, the removal efficiency of N and Cl reached 98.93% and 97.14%, respectively. The leaching kinetics indicated that the dissolution of NaAlO2 clinkers was a first-order reaction and controlled by layer diffusion process. The green detoxification and effective extraction of the Al element from SAD were simultaneously achieved without any pretreatments.

Recent Progress in Electric Furnace Titanium Slag Processing and Utilization: A Review

Titanium slags produced through ilmenite electric furnace smelting contain 60–80%TiO2, a vital titanium resource in the titanium industry. The processing and utilization of titanium slag is faced with many challenges, such as complex mineral structures, high requirements, severe environmental pollution, and heavy additives and energy consumption. This study aims to review the technologies for the processing and utilization of titanium slag. First, we analyze the characteristics of titanium slag from different regions. Then, we discuss in detail the methods for processing and using titanium slag. The progress in electric furnace titanium slag processing and utilization can be divided into two areas: the preparation of titanium dioxide and high-quality titanium-rich materials. These include H2SO4 leaching, HCl leaching, fluoride leaching, sulfur roasting–leaching, alkaline roasting–leaching, oxide roasting–leaching, oxidation and reduction roasting–leaching, phosphorylation roasting–leaching, and ammonia decomposition leaching. Further development of oxide roasting–leaching for the extraction of titanium from titanium slag is recommended.

Efficient Method for α-TiP Synthesis using Alkaline Decomposition Pretreatment of Ilmenite Natural Beach Sand

The layered, acidic compound; α-TiP is widely popularized as a sorbent material for heavy metal removal from wastewater, as catalysts for biomass conversion and as an intermediate to produce high purity titanium dioxide particles. One of the conventional route for its synthesis is to react ilmenite with orthophosphoric acid under reflux conditions. However, the major drawback of this method is that the titanium recovery is only 35 wt. % and about 10 wt. % of the initial ilmenite remain unreacted as the residue. The conversion of ilmenite into an easily acid digestible compound could be attained via alkaline roasting. The objective of this research was to increase the yield of α-TiP from ilmenite using an additional alkaline roasting pre-treatment step to the acid leaching. Potassium hydroxide was selected for the alkaline roasting step since it is regarded to be an environmentally benign chemical. The pre-treatment of ilmenite with a 1:4 molar ratio of KOH to ilmenite at 700 C generated potassium iron oxides and potassium titanium oxides as intermediate compounds which were then washed with distilled water, filtered and dried at 100 C for 24 hours. The solid compound was reacted with orthophosphoric acid with a solid to liquid ratio of 1/8 under reflux conditions for 4 hours. Then the remaining acid leachate was decanted and the white precipitate from the leach liquor was filtered, washed and dried at 100 C for 24 hours. The obtained powder was characterized using X-Ray Diffraction (XRD) analysis, X-Ray Fluorescence (XRF) spectroscopy, FTIR spectroscopy and Raman spectrophotometry and was confirmed to be α-TiP. The parameters; the effect of KOH/ilmenite ore molar ratio, calcination temperature, solid to liquid ratio in the acid leaching step, acid leaching reflux time on the titanium recovery were fine tuned. This research concluded the possibility of increasing the titanium extraction. Therefore the research concludes the increment of α-TiP yield after the pre-treatment step using KOH.
 Keywords: Ilmenite, Titanium phosphate, Alkaline roasting, Alkaline pretreatment

Alternative Method for Treating Electric Arc Furnace Dust: Simulation and Life Cycle Assessment

The technical and environmental aspects of treating electric arc furnace dust (EAFD) using a novel process including alkaline roasting and organic acid leaching were evaluated and compared to the globally applied conventional Waelz process. The global warming potentials of the roasting–organic acid leaching process (with co-product credits) and the Waelz processes were 7.48 and 4.71 kg CO2-eq with 33% Zn dust as the feed material. However, with decreasing Zn content, the novel process become environmentally more competitive, and with 12% Zn, the corresponding GWP values were 6.31 and 9.26 kg CO2-eq. Co-product recovery decreased the net environmental impacts from the processing of the dust, which gave some benefits to the novel process. The Waelz process was observed to be energy intensive; however, the high consumption of leaching and roasting chemicals was the issue in the novel process. The excess caustic soda in the roasting step was observed to be a significant factor in the overconsumption of the organic acid in the leaching stage, and therefore, optimization of the roasting step is crucial. Other ways to decrease leaching chemical consumption include investigating the possibility to reuse the raffinate in leaching, or scrubbing the leach calcine from acid-consuming alkali. Evaluating the impacts of novel processes early enables iterative and agile process development and the directing the focus on the problem areas.Graphical

Removal of Silicon, Aluminum and Phosphorus Impurities from Low-grade Iron Ore by Reverse Froth Flotation and Alkaline Roasting

Removal of Silicon, Aluminum and Phosphorus Impurities from Low-grade Iron Ore by Reverse Froth Flotation and Alkaline Roasting

Migration behavior of impurities during the purification of waste graphite powders

Metal-laden solid wastes (e.g., waste graphite powders) have attracted great attention owing to their hazardous effects on the surrounding soil and water. Additionally, the metal-bearing impurities also hinder the reutilization of waste graphite powders. Thus, it is necessary to remove these inorganic impurities and figure out the removal mechanism of impurities in the purification process. In this study, an alkaline roasting-water washing-acid leaching (AWA) method was used to upgrade the waste graphite powders, and the migration behavior of diverse impurities has been qualitatively and quantitatively investigated. A graphite product with high impurity removal efficiencies is attained under optimal conditions. The removal of impurities mainly follows three routes: (1) V-, P-, and S-bearing impurities were complete removed (some formed soluble salts during alkaline roasting, and the remainder was dissolved in acid); (2) most Al-, K-, and Si-bearing impurities were removed by alkaline roasting, with the remainder was dissolved in the acid-leaching process; and (3) Fe-, Mg-, Ti-, Ca-, and Zn-bearing impurities were decomposed at high temperature and reacted with alkali to form hydroxides or oxides, which was subsequently dissolved in acid. In addition, the treatment of the generated wastewater is also discussed. The uncovered migration mechanisms of diverse impurities would guide the purification and reutilization process of other metal-bearing solid wastes efficiently.

Alkaline Roasting Approach to Reclaiming Lithium and Graphite from Spent Lithium-Ion Batteries

Recycling anode materials from spent lithium-ion batteries (LIBs) plays a significant role in relieving the environmental pollution and shortage of graphite and lithium resources. Most of the current routes employed mineral acids to leach out Li from the graphite anode, inevitably producing hazardous hydrofluoric acid (HF) because some Li exists in the form of lithium fluoride (LiF). In this study, we employ a NaOH roasting approach, by which LiF is converted to NaF and LiOH at 350 °C and thereby avoids the generation of HF. After roasting, the Li and graphite can be separated by a water leaching process without using mineral acids. The leaching efficiency of Li is close to 100%. The regeneration process of NaOH was also discussed considering the large-scale application. Additionally, the recovered graphite delivered an initial charge capacity of 370.8 mA h g–1 and a Coulombic efficiency of 90.05%, showing the comparable performances to the commercial graphite. Overall, the alkaline roasting approach does not use mineral acids and thus avoids generating toxic HF and waste acids, promising a green way to recycle anode materials from various spent LIBs.

Recovery of rare earth elements from coal fly ash using enrichment by sodium hydroxide leaching and dissolution by hydrochloric acid

ABSTRACT The most common method to recover valuable rare earth elements from the potential resource coal fly ash is direct leaching in acidic solution. However, the extraction of rare earth elements using only acid leaching is not sufficiently effective due to the presence of Al-Si-based glasses. In the present work, pre-treatment using NaOH leaching was investigated to reduce the content of Al-Si-based phase before subjecting to acid leaching. The treatment at conditions NaOH 5 M, at 100 °C and for 120 min could dissolve 53% of the ash sample, and the rare earth contents were enriched from 267 mg/kg to 556 mg/kg. The NaOH leaching promote the further extraction of rare earth elements in all of acid medias (HCl, HNO3 and H2SO4), and HCl was the most effective leachant. More than 90% of rare earth elements was dissolved in 5 M HCl solution at 50°C after 120 min. The combination of NaOH treatment and HCl leaching presented an effective approach to extract rare earth elements from coal fly ash with enrichment of rare earth element contents, increase the leaching efficiency and avoidance of harmful impacts to the environment due to the conventional pre-treatment using alkaline roasting.

Hydrofluoric Acid-Free Extraction of Ta and Nb from a Coltan Ore (Lulingu, Drc) Through Alkaline Roasting, Water Leaching, Precipitation and Oxalic Acid Leaching

Hydrofluoric Acid-Free Extraction of Ta and Nb from a Coltan Ore (Lulingu, Drc) Through Alkaline Roasting, Water Leaching, Precipitation and Oxalic Acid Leaching

Extraction of Nb and Ta from a coltan ore from South Kivu in the DRC by alkaline roasting – thermodynamic and kinetic aspects

An alkaline roasting of a coltan bearing ore from the Numbi deposit (South Kivu, the DRC) was investigated with particular focus on the extraction kinetics of Ta and Nb. Isothermal roasting experiments were carried out to study the effects from KOH to ore mass ratio, particle size and roasting temperature on the degree of Ta and Nb recoveries. The roasting efficiency was found to be affected by all the parameters being studied with their optimal values being found as following: particle size range +75–45 µm, KOH to ore ratio 3/1, roasting temperature 550 °C and roasting duration of 1 h. Under these conditions, 80% of Ta and 87% of Nb were recovered from the ore. The kinetic data analysis by different kinetic models indicated that the caustic potash roasting of the Numbi coltan ore is governed by a chemical reaction at particle surface. The apparent activation energies for Ta and Nb were estimated as 40.9 and 46.1 kJ.mol-1 respectively. The obtained results demonstrated that it is possible to bring Ta and Nb into solution without using hydrofluoric acid and deliver a pregnant leach solution (PLS) suitable for downstream treatment.