Optimum Roasting Conditions Research Articles

Process and mechanism of Zn and Co leaching from cobalt xanthate slag enhanced by oxidative roasting

Cobalt xanthate slag is the waste slag produced by the use of xanthate cementation and decontamination before the wet refining and electrowinning of Zn, in which Zn, Co, Cd, etc., and butyl xanthate exist in the form of hydrophobic complexes, which are poorly soluble with water. In addition, most of the cobalt xanthate in the slag exists in the form of high-valent Co, which lowers the extraction rate when directly leaching the metal elements. In this study, the atmosphere of the roasting process is regulated to destroy the hydrophobic complexes and change the mineral phase structure of the cobalt xanthate slag. In the cobalt xanthate slag, the Co and Fe valence states change during the roasting and leaching steps; specifically, during the roasting process, the complexes first decompose into CS2, reducing part of the Co3+. Following the disappearance of this sulfur-rich environment, the oxygen in the flowing air oxidises Fe2+ to Fe3+, but the valence state of Co remains unchanged. During the subsequent leaching process, Co3+ and Fe2+ further react to realise the benign transformation of Co3+ to Co2+ and Fe2+ to Fe3+ without an added redox agent. The rapid redox reaction between Co3+ and Fe2+ controls Co3O4 dissolution; thus, the reaction rate is controlled by the slower process of internal diffusion. Under the optimal roasting conditions, the Co3+ content in cobalt xanthate slag decreases to 21.10 % and that of Fe2+ to 48.78 %. Consequently, the optimum Zn and Co leaching rates reach 99.92 % and 99.57 %, respectively, and only 0.86 % of Fe in the final leaching solution exists in the form of Fe2+.

Selective extraction of lithium and solidified fluoride from overhaul slag by the calcium sulfate roasting and water leaching

Overhaul slag is a hazardous waste which is from the process of aluminum electrolysis industry. In this work, a technology of calcium sulfate roasting and water leaching was developed to dispose of overhaul slag. The effects of roasting and leaching parameters were investigated in detail. Under the optimal roasting conditions, the fluorine could be stably solidified into CaF2, and lithium could be converted into soluble NaLi(SO4). The roasted clinker was then subjected to water leaching for the selective extraction of lithium. About 99.74 % of lithium was extracted and 99.82 % of fluoride was solidified by the leaching process under the optimal leaching conditions. After water leaching, the concentration of lithium can reach 2.3 g/L. XRD analysis shows that the main phases of the aqueous solution after evaporation and crystallization are NaLi(SO4) and Na2SO4, and a small amount of impurities can be further removed and concentrated to prepare Li2CO3. The main components of leaching slag are C, Al2O3 and CaF2, which can be used as fast setting cement. The process proposed in this paper is not limited to the recovery of high-value lithium from overhaul slag, and can be applied to the extraction of other valuable waste substances in aluminum industry.

Study of the influence of temperature and duration of chlorinating roasting on the extraction of gold from E-waste

In this work, based on experimental studies, the effect of roasting temperature and duration on the chlorination of gold from E-waste under low-temperature conditions was studied. It has been established that in the low-temperature range of 150-300 °C, the gold content in the residue shows a sharp decrease, reaching its minimum of 8 ppm at 250 °C. A further increase in temperature does not affect the gold content in the cinder. It has been shown that during chlorinating roasting above a temperature of 250 °C, side reactions should be expected to occur with the formation of additional phases representing chlorides of copper, iron and other elements. The results of SEM and XRD analyzes of the solid phase obtained after chlorinating roasting at a temperature of 250 °C and a roasting duration of 20 minutes showed the presence of copper and iron chlorides in them. Optimal technological parameters and modes of the process of chlorinating roasting of E-waste with gaseous chlorine have been established: temperature – 250 °С; roasting duration – 20 minutes; chlorine consumption is 1.5 times more than the stoichiometrically required amount (SRA) for gold chlorination. Under optimal roasting conditions, a high, up to ~97.6%, recovery of gold in the form of gold chloride (AuCl3) was achieved. The results of the experiments can be a basic basis and make it possible to conduct more representative experiments (scaling) in the future, taking into account the established optimal technological parameters. This will provide a chance to evaluate the possibility of extracting gold from E-waste of different types and compositions and to conduct further research on obtaining pure gold from the collected representative amount of gold sublimate AuCl3 by smelting.

Optimization of Roasting Conditions on the Functional Properties of Jackfruit Seed Flours

Roasting of jackfruit seeds may improve the functional properties of jackfruit seed flours produced, which is vital for applications in baking and confectionaries. The objectives of this study were to determine the optimum roasting conditions of jackfruit seeds and to evaluate the functional properties of roasted jackfruit seed flours. Response surface methodology (RSM) was employed to optimize the roasting process in a temperature range (120 - 170 ℃) and in a duration range (20 - 70 min). The roasting temperature had a significant effect (p < 0.05) on water absorption capacity (WAC) and water solubility index (WSI), while roasting time significantly influenced (p ˂ 0.05) WAC, oil absorption capacity (OAC), bulk density (BD), WSI and swelling power (SP) of the jackfruit seed flours. Based on the results obtained from RSM, the optimum roasting conditions were 162 ℃ for duration of 20 min. The predicted values were 1.45 g/g, 0.96 g/g, 0.49 g/ml, 9.74 % and 4.35 g/g for WAC, OAC, BD, WSI and SP, respectively with the overall desirability of 0.693. The optimum conditions obtained from RSM can be used to produce roasted jackfruit seed flours with desirable functional properties for future development of bakery products.

Characterization of taste and aroma profile in pomegranate (Punica granatum L.) seed oil using electronic sensors, GC-MS/olfactometry

In this study, electronic sensors, gas chromatography–mass spectrometry (GC-MS), and GC-olfactometry (GC-O) were used to analyze the flavor of pomegranate seed oil (PSO) extracted from roasted pomegranate seeds. A preliminary study was conducted to determine the extent to which roasting treatment positively affects the physicochemical and sensory properties of pomegranate seeds, and a total of four conditions including raw were selected (raw, 160 °C for 15 min, 160 °C for 20 min, 180 °C for 10 min). This study aimed to determine if the beneficial effects of roasting seeds are retained when the oil is extracted from the seeds, and to explore their potential use in the food industry as a fat-soluble material. Electronic tongue (E-tongue) analysis revealed that roasting enhanced umami and sweetness while reducing bitterness. A total of 46 and 50 volatile compounds were detected using the electronic nose (E-nose) and GC-MS, respectively. The major volatile compounds were Maillard reaction products, which were not detected in the raw samples, and the terpene content decreased after roasting. A total of 13 odor-active compounds analyzed by GC-O were identified, with the majority having odor-active value (OAV) above 1. This study provides an aroma profile of PSO that can be used as a primary database for controlling the aroma and selecting optimal roasting conditions for application in food processing.

XPS Investigation of Magnetization Reduction Behavior and Kinetics of Oolitic Hematite in Gas-Based Roasting

Magnetization reduction roasting is an important method for the utilization of oolitic magnetite. In this study, the magnetization reduction behavior and kinetics of oolitic hematite in gas-based roasting were systematically investigated by X-ray photoelectron spectroscopy (XPS). The results revealed that under optimal roasting conditions of 650 °C, a roasting time of 60 min, and a CO concentration of 30%, the magnetization reduction rate of the roasted product reached 44.34%. Furthermore, the weak magnetic separation concentrate presented a TFe of 58.09% and a concentrate iron recovery of 94.3%. The results of the XPS spectrum indicated that the peak area ratio (Fe2+/Fe3+) gradually increased with an increase in roasting temperature, roasting time, and CO concentration, while over-reduction occurred when the roasting temperature exceeded 750 °C. The investigation of magnetization roasting kinetics for varying particle sizes demonstrated that the magnetization reduction process is controlled by chemical reaction, with a corresponding activation energy range of 42.96 kJ/mol to 63.29 kJ/mol, indicating the particle size has little effect on the magnetization reduction of oolitic hematite.

Effects of roasting conditions on the properties of Amaranth (Amaranthus cruentus L.) grain using response surface methodology

Industrial applications of amaranth seeds (Amaranthus species L.) have not been fully explored, which may be due to dearth of information on its various forms of use or applications. Roasting is one of such ways amaranth grain can be processed for immediate snacking or preparation prior to use for varying other purposes. The focus of this study was on the effect of roasting conditions on the properties of amaranth grain, using response surface methodology design to develop, improve, and optimize the process. Data was analyzed using regression and analysis of variance (ANOVA) at α 0.05. Five levels of roasting temperature and durations were employed. The roasted amaranth seeds were subjected to evaluation for proximate, colour, functional and sensory properties using standard methods. Effect of roasting conditions on properties were modeled and optimized. The roasting conditions had a significant effect on the proximate, colour, functional and sensory properties of roasted amaranth seeds. The optimal roasting conditions were a roasting temperature of 180 °C, roasting duration of 8 mins with desirability of 0.69. The optimum roasting conditions resulted in roasted amaranth seeds with protein of 16.26%, moisture of 18.30%, ash of 1.86%, fat of 2.22%, crude fibre of 8.92%, carbohydrates of 52.70%, bulk density of 1.29%, Oil Absorption capacity of 6.26 g/g, water absorption capacity of 9.20 g/g, solubility of 6.49%, swelling power of 14.16%, colour of 198.31°, and overall sensory acceptability score of 7.20. Roasted amaranth grains or its flour creates a value added product from amaranth grain which could be used as is for varying purposes, or in composite form for diverse uses.

Effect of roasting on the total polyphenol content and antioxidant activity of sesame (Sesamum indicum L.) seeds grown in Ethiopia

Consumers prioritize safe and high-quality foods, underscoring the importance of ensuring the quality of agricultural products to meet their expectations. Sesame (Sesamum indicum L.) is the most widely grown food crops, cultivated in different cultivars and types throughout the world. It is the second most valuable crop next to coffee in Ethiopia's foreign exchange earnings. The present study aimed to determine the total phenolic content and antioxidant activity of raw and roasted sesame seeds from seven major sesame-producing areas in Ethiopia. The total phenolic and flavonoid contents of raw seeds ranged from 67 to 154 mg GAE/100 g DW and 19–43 mg CE/100 g DW, with DPPH scavenging activity between 0.55 and 0.85 mg AAE/g. Conversely, roasted seeds had average phenolic and flavonoid levels, as well as antioxidant activity, averaging 56–97 mg GAE/100 g DW, 14–21 mg CE/100 g DW, and 0.63–1.04 AAE/g, respectively. Significant differences (p < 0.05) were observed between the raw and roasted seeds in these parameters. The roasting process led to a decline in polyphenol and flavonoid contents, likely due to heat-induced degradation and/or alteration of these compounds. However, the roasted seeds exhibited enhanced antioxidant properties, probably ascribed to the formation of new substances having antioxidant activities. The study suggests further investigation into optimal roasting conditions to minimize polyphenol loss.

A sustainable approach for recovering copper and zinc from copper smelting flue dust: Paving the path for waste reduction

The recovery of metals without generating secondary waste is a critical focus in the management of hazardous copper smelting dust. To tackle the challenges associated with arsenic-containing solid waste and waste acid generated by traditional recycling processes, we propose a two-stage roasting process that prioritizes low-temperature roasting for arsenic removal, followed by high-temperature roasting for desulfurization of sulfates. This work focuses on the high-temperature desulfurization behavior of residue after arsenic removal. The changes in composition during roasting were analyzed using TG-DSC, XRD, and SEM. The results revealed that the reaction temperature and the addition of bituminite are pivotal in the desulfurization process. The optimal roasting conditions were obtained to be a reaction temperature of 700 °C and a roasting duration of 3 h. Subsequently, approximately 98.77% of copper and 97.17% of zinc could be leached under conditions of a leaching temperature of 80 °C, a reaction time of 4 h, a sulfuric acid dosage of 3 times the theoretical amount, and a liquid-to-solid ratio of 10:1. This process mitigates the generation and accumulation of arsenic-containing waste acid during copper electrodeposition in the traditional hydrometallurgical process of copper smelting flue dust. It lays the foundation for clean and efficient recovery and also provides insights for recycling other copper-containing wastes.

Extraction of Fe and Al from red mud using carbothermic reduction followed by water leaching

Red mud, a solid byproduct from bauxite ore processing for Al2O3 production, encompasses valuable industrial metals, including Fe and Al. The objective of the present study was to investigate the feasibility of an integrated route for the efficient use of red mud for the multistep extraction of Fe and Al. Carbothermic roasting was performed in the presence of Na2CO3 to reduce iron oxide to metallic iron. Optimal roasting conditions (reductant dosage: 1 g, temperature: 900 °C, time: 120 min, and charge ratio 10:5:1) yielded a 95.6 % recovery of the magnetic fraction. Applying a magnetic gradient of 0.1 T resulted in a 92.5 % recovery of metallic iron. Subsequent water leaching, performed under optimal conditions (time: 120 min, temperature: 70 °C, pulp density: 10 %), achieved a 98.5 % leaching efficiency of Al from a nonmagnetic fraction, with and without sodium carbonate, demonstrating 26 % efficiency. Incorporating sodium salt during carbothermic roasting facilitated the reduction of iron oxide to metallic iron and activated alumina for leaching. Finally, a value-added Al product, AlPO4, was precipitated from the leachate. This approach primarily attempts to contribute to a more circular economy, reducing waste and minimizing the environmental impact.

Priority recovering of lithium from spent lithium-ion battery cathode powder by pyrolysis reduction of Bidenspilosa

In this paper, the invasive plant Bidens pilosa was used as a carbon material to roast and reduce the cathode powder of spent ternary lithium-ion batteries (LiNixCoyMn1-x-yO2), to alleviate lithium resource scarcity and the problems of large spent of batteries which is harmful to the environment. The transition metals in the cathode powder were reduced to Ni, Co, and MnO, respectively, and the Li element in the cathode powder was reacted to generate Li2CO3. The experiment explored the reduction effect of high valent metals in spent lithium-ion batteries at different roasting temperatures and biomass ratios, and the impact of different time on the leaching of Li element. Results showed that the optimal experimental conditions of reduction roasting were as follows: temperature 700 °C, biomass ratio 20%. The leaching efficiency of Li obtained under optimal roasting conditions through leaching was 94.15%. TG-DSC/MS, XRD, XPS, SEM, and other instruments characterized the experimental results. This method not only efficiently converts Bidens pilosa into a carbon-reducing agent and solves the problem of plant invasion, but also promotes the decomposition of spent cathode powder, reduces high valence metals to single metals and low valence oxides, and generates Li2CO3 through reaction, which can selectively extract lithium element and reduce the amount of reagent added and the use of reducing agent in the subsequent leaching process.

Selective separation of zinc from germanium-bearing iron cake via a roasting–leaching process

Germanium-bearing iron cake (GBIC) produced through the germanium removal process in a zinc smelter is a valuable source of zinc and germanium. However, achieving selective separation of zinc and germanium using pyrometallurgy treatment and sulfuric acid leaching methods is challenging. To address these challenges, this study introduced a novel roasting–leaching process. During roasting, willemite transformed into ammonia-soluble hemimorphite, promoting zinc leaching. This transformation was mainly attributed to the reaction between in situ water in GBIC and willemite within 200–500 °C. Optimal roasting conditions included a particle size range of 49–74 µm, a roasting temperature of 490 °C, and a duration of 4 h. Under optimized leaching conditions—[NH4++NH3] (7 mol/L), NH4+/NH3 molar ratio (2.5), temperature (50 °C), liquid-to-solid ratio (20 mL/g), agitation speed (600 rpm), and time (180 min)—zinc and germanium exhibited leaching yields of 84.92 % and 0.59 %, respectively, in an ammonia–ammonium carbonate system. After three cycles of leaching, the Zn concentration in leachate increased to 20 g/L, facilitating the subsequent recovery of zinc. Moreover, the Ge concentration in the germanium-bearing leaching residue increased by 1.5 times compared with the initial GBIC, making the residue a valuable source of germanium.

Pt and Al Recovery from a Spent Pt/Al2O3 Catalyst via an Integrated Soda Roasting–Alkaline Leaching–Carbonization Process

An integrated soda roasting–alkaline leaching–carbonization process was developed to recover platinum (Pt) and aluminum (Al) from a spent Pt/Al2O3 catalyst. A product with the main component of NaAlO2 was obtained under the optimal roasting conditions of the mass ratio of Na2CO3 to spent catalyst 1, roasting time 2 h and roasting temperature 900 °C. The Al in the roasted residue was effectively leached in a dilute NaOH solution, while Pt was enriched in the leached residue with a Pt content that reached 29.4%, and the calculated concentration factor of Pt yielded 79.4. After carbonization was performed for the leached solution, 99.0% of the Al was recovered as the pseudo-boehmite product, which could be used as the feed for preparing the Al2O3 carrier. Pt and Al2O3 in the spent catalyst were selectively separated and enriched using the above process, which thus has good application prospects.

Fate of ochratoxin A in dried red chilies during roasting process

Abstract Dried red chilies are widely used globally and are susceptible to contamination by fungi and fungal toxins. Roasting is a common way of processing dried red chilies. This study explored the effects of Aspergillus niger and ochratoxin A (OTA) contamination on the quality of roasted chilies, and the fate of OTA during the roasting process. Three optimum roasting conditions (140 °C×8 min, 160 °C×6 min, and 180 °C×4 min) were screened out by a combination of instrumental and manual sensory evaluations. Under these roasting conditions, A. niger and OTA contamination diminished the quality and taste of roasted chilies. With increasing roasting temperature and time duration, OTA content and mold counts gradually decreased, together with the DNA degradation of OTA biosynthesis-related genes of A. niger in roasted chilies. The roasting condition at 180 °C×4 min showed the greatest decomposition effect on OTA, while also maintaining good sensory quality of roasted chilies. This study shed light on the fate of OTA during the chili roasting process.

Efficient separation of Li and Mn from spent LiMn2O4 cathode materials by NH4HSO4 reduction roasting-selective ammonia leaching

With the imminent peak in the retirement of rechargeable lithium-ion batteries worldwide, the development of efficient methods for recycling valuable elements from LIBs has attracted considerable attention. In this work, a novel method of NH4HSO4 reduction roasting-selective ammonia leaching was proposed to thoroughly separate Li and Mn from the spent LiMn2O4 cathode materials. Using the TG-DSC-FTIR, XRD, SEM-EDS and ICP methods, the detailed mechanism of reduction roasting process was revealed, showing that the Mn4+ and Mn3+ in the spinel structure of LiMn2O4 were reduced by the NH4+ from the molten ammonium salt, and transformed into water-soluble MnSO4 and Li2Mn2(SO4)3. According to the water-leaching performance of the roasting products, the sulfation conversion rate of Mn reaches 98.1 %, while Li is almost completely transformed under the optimal roasting conditions (475 ℃, 60 min). Using the NH3·H2O-air leaching-system, complete separation of Li and Mn can be achieved. It was shown that the introduction of air into the ammonia solution at a rate of 0.2 L/min under the optimal leaching condition leads to Mn precipitation in the form of nanoscale Mn3O4 particles with a precipitation rate of over 99.99 %, while Li still remains completely leached. Based on the in situ detection of the oxidation reduction potential and pH during the selective leaching, the key mechanism of efficient Mn precipitation was revealed. that is, the increasing potential accelerates the oxidation of Mn(OH)2, and the rapid consumption of Mn(OH)2 promotes the hydrolysis of Mn2+, thereby achieving a significant improvement in the separation efficiency of Li and Mn.

Physico-functional and quality attributes of microwave-roasted black pepper (Piper nigrumL.)

AbstractThe present study was focused on microwave-roasting (300–600 W for 5–15 min) on the quality attributes of black pepper. The increase in roasting power and time decreased the lightness,L* (51.85–25.64), and a visible color change from medium light to dark was observed. Roasting reduced the powder density (bulk density – 0.51–0.41 g/cm3; tapped density – 0.70–0.53 g/cm3), flowability, and crystallinity and showed a higher Hausner’s ratio (1.29–1.42), carr’s index (22.43–29.38), compressibility index (0.22–0.30), cohesion index (13.96–34.80 g mm/g), and caking strength (5225.79–12040.44 g mm). All the samples showed stable flow, and the stability was in the range of 1–1.11. Sample roasted at lower roasting levels had higher antioxidant propertiesviz., phenolic content (36.20–79.62 mg GAE/100 g), flavonoid content (350.52–566.45 mg QE/100 g), % DPPH scavenging activity (53.97–85.12 %), and ABTS assay (2.33–4.81 mmol TE/100 g), whereas the higher roasting conditions reduced the TFC and % DPPH inhibition. The principal component analysis (PCA) and a simple least square method (SLSM) with maximum desirability were used to develop the correlation and optimize the roasting condition, respectively. Results showed that the roasting time had a prominent effect on different quality attributes compared to roasting power, and the optimum roasting condition for BP is 300 W, 15 min.

Recovering cobalt from cobalt oxide ore using suspension roasting and magnetic separation technique

Cobalt ore is a scarce resource in China, often associated with iron ore, and it is well known that its separation and effective recovery are extremely difficult. In this paper, cobalt oxide ore is used as raw material and reduced by suspension roasting method at the atmosphere of H2. Magnetic separation is carried out to obtain cobalt (Co) and Fe concentrate. The experimental results show that the optimal magnetic separation performance of cobalt oxide ore is achieved at 650 °C and 30 % H2 concentration. The Co and Fe concentration are obtained synchronously with the grade of 7.32 % and 62.13 % respectively. X-ray diffraction (XRD) and scanning electron microscope (SEM) reveals that the phase of cobalt oxide ore in H2 roasting process is transformed into CoO→Co and Fe2O3→Fe3O4. The surface of the sample appears cracks after roasting. The vibrating sample magnetometer (VSM) test reflects the magnetic changes of minerals that the optimum roasting condition leads to an increased magnetism. The specific surface and fracture structure are analyzed to illustrate the specific surface area and pore volume of the particles decrease and the average pore size increases as the roasting temperature increases. In general, reduction roasting of cobalt ore makes it possible to recover Co and Fe simultaneously, following by magnetic separation. The beneficiation efficiency is improved along with the reduced cost.

Process optimization for the development of traditionally roasted chickpea flour for meal replacement beverages

Chickpeas are gaining importance as a sustainable, plant-based protein source. The present study was conducted to optimize the conditions for roasting chickpea seeds that can be used in the development of products having characteristics similar to those made by the traditional approach. The temperature range was selected as 140–220 °C and the time was 1–5 min. The effect of roasting parameters on puffing index, bulk density, water absorption capacity, browning index, color difference, TPC, antioxidant activity, and overall acceptability was analyzed. Based on the criteria set, optimum roasting conditions were selected using numerical optimization. The optimum solution was found at 181.64 °C and a time of 3.17 min, with a desirability of 0.871. Roasting significantly affected chickpea flour's physical, proximate, functional, microstructural, thermal, and pasting properties. TPC and antioxidant activity increased, whereas TFC decreased after roasting. The morphology of starch granules was highly modified, and their thermal properties also varied considerably.

Chemical Composition, Fatty Acid Profile, and Optimization of the Sacha Inchi (Plukenetia volubilis L.) Seed-Roasting Process Using Response Surface Methodology: Assessment of Oxidative Stability and Antioxidant Activity.

This study aimed to optimize the roasting conditions for sacha inchi (Plukenetia volubilis L.) seeds using the central composite design (CCD) of the response surface methodology (RSM). The antioxidant activity and oxidation indicators (peroxide and TBA values) were assessed, along with the impact of roasting on the fatty acid profile and chemical characterization of the seeds using gas chromatography. The results demonstrated that roasting partially increased the indicators of lipid oxidation in the oil extracted from roasted seeds, as well as the antioxidant activity of the seeds. The optimal roasting conditions were determined using CCD and RSM, resulting in an optimized temperature of 134.28 °C and 18.84 min. The fatty acid contents were not significantly affected by the roasting intensity, whereas a higher presence of amino acids was found in the seeds roasted at 140 °C for 15 min. In conclusion, it is suggested that the optimal roasting conditions for enhancing amino acid presence, improving antioxidant activity, and maintaining oxidative stability in sacha inchi seeds fall within the temperature range of 134-140 °C and a roasting duration of 15-20 min.

The Recovery of TiO2 from Ilmenite Ore by Ammonium Sulfate Roasting–Leaching Process

TiO2 production is a key part of Ti metallurgy and Ti recycling, and the process itself has turned out to be energy-consuming and material-consuming. New technologies are needed to utilize complex Ti ores, such as ilmenite, and reduce the carbon footprint of TiO2 extraction. Ammonium sulfate roasting has been revealed as an efficient way to carry out phase transformations of complex minerals. A low-temperature sulfation roasting approach was studied to chemically breaking down the crystal structure of ilmenite and generate metal soluble sulfates simultaneously. These roasted products were introduced to water leaching, then the residue of the water leaching was leached by diluted HCl acid, and the TiO2 product was enriched in the leaching residue. The effects of roasting temperature, roasting time, ilmenite-to-ammonium sulfate mass ratio, ilmenite particle size, and second-stage roasting on iron removal and titanium loss leaching efficiency were systematically studied. The results show that the optimum roasting conditions were a roasting temperature of 500 °C, a roasting time of 210 min, an ilmenite-to-(NH4)2SO4 mass ratio of 1:7, and an ilmenite particle size of below 43 µm. Under optimized conditions, the TiO2 grade in the obtained synthetic rutile reached 75.83 wt.%. Furthermore, the phase transformation and reaction mechanism during roasting are discussed and interpreted.