Titanium dioxide (TiO2) has been widely used as pigment in paints, fillers for plastic and paper, coatings, adsorbents, cosmetics, catalysts, and gas sensors. A novel process for TiO2 production has been developed by the Institute of Process Engineering. This work develops the novel process by using the NaOH/KOH binary molten salt (50 mol % NaOH, 50 mol % KOH) instead of NaOH molten salt. Under conditions of temperature 350 °C and mixed alkali-to-titanium slag ratio 1.4:1, the titanium conversion ratio obtained is >98% with reaction time around 90 min. The kinetics investigation indicates that the decomposition of titanium slag is controlled by mass diffusion in thed residual layer and the apparent activation energy is 43.1 kJ/mol. 98% of KOH and 86% of NaOH can be recycled by a water leaching process. On the basis of the experimental results, a flow sheet was developed and tested, and the content of TiO2 obtained in the product reached 99.5%. As the NaOH/KOH binary molten salt system provides a liquid as relatively low temperature, the energy consumption of this technology may probably be lower than that of the existing one.

A sodium modification–direct reduction coupled process was proposed for the simultaneous extraction of V and Fe from vanadium- bearing titanomagnetite. The sodium oxidation of vanadium oxides to water-soluble sodium vanadate and the transformation of iron oxides to metallic iron were accomplished in a single-step high-temperature process. The increase in roasting temperature favors the reduction of iron oxides but disfavors the oxidation of vanadium oxides. The recoveries of vanadium, iron, and titanium reached 84.52%, 89.37%, and 95.59%, respectively. Moreover, the acid decomposition efficiency of titanium slag reached 96.45%. Compared with traditional processes, the novel process provides several advantages, including a shorter flow, a lower energy consumption, and a higher utilization efficiency of vanadium-bearing titanomagnetite resources.

•V (V) was effectively separated from high-acidity chloride liquor with many ions.•Synergistic coefficient of 3.26 was obtained by Aliquat 336–TBP extraction system.•Over 90.0% of vanadium and almost no other cations were extracted in three stages.•Vanadium stripping in one stage was above 92.0% and V2O5 product was prepared.•Mechanism on V (V) extraction by mixed extractant was studied by FT-IR and UV–vis.A selective synergistic extraction process for recovering vanadium (V) from the high-acidity chloride leaching liquor was proposed. Vanadium (V) extraction from the simulated high-acidity leaching liquor with numerous impurities using a mixed extractant consisting of tricaprylmethylammonium chloride (Aliquat 336) and tri-n-butyl phosphate (TBP) was studied while obvious synergism was found. According to synergistic enhancement coefficient and physical property of organic phase, the suitable extractant composition was the volume ratio of Aliquat 336 to TBP 1:4. The vanadium (V) extraction increased sharply as HCl concentration increased from 1.01 mol/L to 4.13 mol/L. Under the optimum extraction conditions (extractant concentration of 50 vol%, 1 min, 25–30 °C, and phase ratio (O/A) of 1:1), the vanadium extraction with three stages was above 90.0%. Almost no other impurity ions, such as Ca, Al, Mg, Cr, Ti, Mn, and Si, were co-extracted. Under the optimum stripping conditions, the vanadium stripping was above 92.0% in a single stage using water as the effective stripping reagent. High-quality V2O5 product was obtained after precipitation and calcination. The mechanism of vanadium (V) extraction by Aliquat 336–TBP mixed extractant was discussed based on the analysis of FT-IR and UV–vis spectra.

•Good color performance of Cr2O3 pigment was prepared by hydrothermal reduction.•The conversion of chromate easily reaches 99 wt% by adding NaHCO3.•Mineralizer promotes the agglomeration of chromium hydroxide.•Mineralizer changes surface properties of chromium hydroxide.•Mineralizer affects the formation of Cr(III) complex and chromium hydroxide.A chromium oxide green pigment was prepared by thermal decomposition of chromium hydroxide via hydrothermal reduction of a high concentration mixture of Na2CrO4 (300 g/L) using NaHCO3 as a mineralizer. The mineralizer effects on the hydrothermal process, conversion of chromate, properties of amorphous Cr(OH)3, and color performance of Cr2O3 were investigated. Compared with sodium carbonate and urea, sodium bicarbonate significantly reduces the Na2CrO4 concentration and, consequently, improves the conversion of Na2CrO4 during the hydrothermal process. Additionally, homogeneous particles were obtained by adding NaHCO3. The changes in the amount of trapped water, oxygen chemisorption, and negative charge on the surfaces of chromium hydroxide particles caused by adding a mineralizer were analyzed using Fourier-transform infrared spectroscopy and zeta potential analysis. The Cr2O3 pigments were characterized using X-ray diffraction, scanning electron microscopy, and an automatic differential colorimeter. A good color performance by the Cr2O3 pigment, comparable to that of a commercial pigment, was obtained.An appropriate amount of mineralizer was contributed to reach high conversion of chromate and form homogeneous amorphous chromium hydroxide particles, promoting good color performance of a Cr2O3 green pigment, comparable to that of a commercial pigment.

•Swelling of pellet during reduction was examined by a consecutive imaging method.•Swelling index (SI) increased with temperature but weakened with addition of H2.•Formation of massive wüstite phase led to the swelling firstly.•Different iron precipitation caused difference in swelling states in the later.Hydrogen and carbon monoxide mixtures are main reducing agents for gaseous direct reduction (DR) processes. In the present study, volume change of pellet reduced in H2–CO mixtures at 800–1000 °C was examined with a novel consecutive imaging method. Results showed that pellet expansion intensified with temperature and CO content in atmosphere and it reached the maximum at reduction degree of 20%–40% due to the formation of massive wüstite phase. Pellet in H2 rich atmospheres passed the wüstite stage rapidly and swelling consequently weakened. Iron whiskers that formed in the later reduction stage led to persistent swelling as pellet reduced by CO. However, pellets contracted obviously in H2 containing atmospheres for the collection of iron phase in the later. Compressive strength of pellets during reduction dropped to be the lowest in 10–20 min. And the time for pellets remained in the “low strength zone” (< 500 N/P) prolonged with temperature and CO proportion in reducing gas, which showed good correlation with their swelling behavior.

•Recovery of V (IV) from chloride solution with high Fe (II) concentration.•Vanadium extraction of 99% using D2EHPA and vanadium stripping of 98%.•High overall separation coefficient of V and Fe (β = 200).•Purity of V2O5 product is 99.2%.Vanadium (IV) bearing chloride solution with the Fe (II)/V (IV) mass ratio of 60 was prepared to simulate the acidic liquor by hydrochloric acid leaching of reduced vanadium-bearing titanomagnetite. Extractant of bis (2-ethylhexyl) phosphoric acid (D2EHPA) was used to extract vanadium from the solution. Under the optimal extraction conditions of equilibrium H+ concentration of 0.27–0.42 mol/L, D2EHPA concentration (v/v, diluted in n-heptane) of 10%, extraction temperature of 20–25 °C, equilibrium time of 60 min, phase ratio (O/A) of 1:1, more than 99% of vanadium can be extracted. Loaded organic phase were stripped by dilute H2SO4 solution under the optimal stripping conditions of H2SO4 concentration of 20 wt.%, phase ratio (O/A) of 10:1, stripping time of 120 min, and 98% of vanadium can be stripped. The concentrations of V and Fe in the stripping solution were 13.0 g/L and 3.9 g/L, respectively. V2O5 products with purity of 99.2% were obtained after oxidation, precipitation and calcination. The overall separation coefficient of V and Fe was 200. Experimental results indicated that V (IV) can be also separated from other metal ions such as Mg (II), Ni (II), Zn (II), Ca (II), Al (III) and Cu (II) in the chloride solution. A flow sheet on the recovery of vanadium from vanadium-bearing chloride solution containing high concentration of iron was proposed.

•We report a novel process for preparing Ti-enriched slag from low-grade V–Ti concentrate.•Macro impurities in the V–Ti concentrate were removed by dilute HCl leaching.•M3O5 structure in V–Ti concentrate can be destroyed by homogeneous pressure leaching.•The content of TiO2 in the Ti-enriched slag prepared can reach 92.5% with further removal of residual carbon.Low-grade, highly reactive V–Ti concentrate was obtained from V-bearing titanomagnetite via selective reduction–magnetic separation. The main phases of the concentrate are anosovite and pyroxene. Two-stage acid leaching was employed to remove the impurities in the concentrate. The leaching behavior of impurities Ca/Mg/Al/Si under different acid leaching conditions in the first stage was investigated in detail. The optimal leaching conditions of the first-stage were as follows: 383 K leaching temperature, 1.40 mol/L HCl concentration, 1/10 solid–liquid mass ratio, and 120 min leaching time, under which the residue obtained contained 79.54% of TiO2 and 2.50% of V2O5. The result of molecular structure simulation indicate that the Ti–O and Mg–O bonds in the anosovite phase are broken under oxygen pressure conditions in the second stage by reacted with HCl solution. The content of TiO2 in the Ti-enriched slag prepared by two-stage acid leaching can reach 92.5% with further removal of residual carbon.

The caking and adhesion of intermediate product on reactor surfaces during TiO2 production via the NaOH molten salt method are a serious problem. The consolidation of intermediate product can lead to low heat transfer efficiency and low titanium fractional conversion. Furthermore, frequent cleaning is generally required. An anti-caking method that can be applied during low-grade titanium slag decomposition in the NaOH system was studied. The method, which involves the two-step reaction of low-grade titanium slag with molten NaOH without the introduction of additives, can significantly reduce the extent of caking. The NaOH and low-grade titanium slag mixture was first reacted at 350 °C for 60 min. The temperature was then increased to 550 °C in 40 min. Finally, the mixture was reacted at 550 °C for 75 min. The effects of the reaction temperatures, NaOH-to-slag mass ratio and the reaction time on the titanium extraction were investigated. The Brunauer–Emmett–Teller (BET) surface area and apparent density were used to characterize the extent of caking. In the low grade titanium slag, silicate phase prior to pseudobrookite phase reacts with molten NaOH at 350 °C in the process of two-step molten reaction and formed sodium silicate. Microstructural and Fourier transform infrared (FT-IR) absorption results show that the firstly formed sodium silicate did not diffuse into the entire reaction system and powder-shaped intermediate product was formed. Approximately 97% of titanium in the titanium slag could be extracted under the optimal reaction conditions. In addition, the content of TiO2 obtained in the product reached 99.3%.Anti-caking in the process of produce titanium dioxide without introducing additives has been achieved successfully. Powder shaped intermediate product can be obtained by the two-step molten salt reaction process. Silicate phase in the low-grade titanium slag was reacted with molten NaOH ahead of pseudobrookite at 350 °C.Highlights► Anti-caking in the process of produce titanium dioxide without introducing additives has been achieved successfully. ► Powder shaped intermediate product was obtained through new method. ► BET surface area and apparent density were used to characterize the extent of caking. ► Silicate phase in the low-grade titanium slag was reacted with molten NaOH ahead of pseudobrookite at 350 °C.

NaCl-type crystal structure sodium titanate (Na2TiO3), which exhibits a unit cell parameter of a=4.49 Å, was obtained by high temperature molten salt reaction. An intermediate phase product with layered structure was prepared by leaching the obtained Na2TiO3. We propose that the layered titanate structure is composed of Na2TiO3 and H2O, corresponding to the host-layer and guest-substance, respectively. Furthermore, the crystal structures of layered titanate were optimized by the density functional theory (DFT). This indicates that water molecules are distributed in an orderly manner in the interlayer through the formation of hydrogen-bonded chain. Moreover, the position of the adjacent lamella translates to c/2 along the c-axis after the intercalation of water.Graphical abstractHighlights► Ti4+ and Na+ ion occupy the same position in unit cell of NaCl-type Na2TiO3. ► Na+ is part of host-layer when layered titanate is obtained from NaCl-type Na2TiO3. ► A first-principles prediction of ideal layered titante structure.

The hydrous alumina/silica double-layer surface coating of TiO2 pigment was prepared by precipitation method under two different conditions. High-resolution transmission electron microscopy (HRTEM), Energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectrum (FTIR) as well as ζ-potential analysis were used to characterize the morphology, structure and surface electrokinetic behavior, respectively. The results show that hydrous alumina is continuously coated on the surface of silica-coated TiO2 particle with a compact layer at 60 °C, pH 4.0. There is a chemical interaction between the hydrous alumina layer and silica layer. An AlOSi bond was formed and a thin film of aluminosilicate was existed. A flocculent hydrous alumina layer was formed at 60 °C, pH 8.0. The XPS spectra of O1s show that the peak of 531.2 eV is assigned to AlO(OH) for the loose and flocculent morphology. The theoretical calculations reveal that the coated Al2O3·H2O on SiO layer combined with (−1 1 1) lattice plant of rutile TiO2 is more stable than the coated AlO(OH) and the discrepancy of total energy between them is about −1.303 eV, i.e., the sample obtained at 60 °C, pH 4.0 has a more stable thermodynamic property. In addition, the adsorption of H+ ion on AlO(OH) surface is easier than that on Al2O3·H2O surface, as the discrepancy of total energy between them decrease to −0.721 eV.Graphical abstractThe structure of (a) 4AlO(OH)/4SiO2/12TiO2; (b) Al2O3·H2O/4SiO2/12TiO2; (c) 2H+/4AlO(OH)/4SiO2/12TiO2; (d) 2H+/2Al2O3·H2O/4SiO2/12TiO2.Highlights► Hydrous alumina/silica layer by layer surface coating of TiO2 pigment was prepared. ► There is a chemical interaction between the hydrous alumina layer and silica layer. ► Possible structure of coated layers were investigated by computer simulation. ► The coated Al2O3·H2O on SiO layer is more stable than the coated AlO(OH) on it.

Activation pretreatment of Cr-containing limonitic laterite ores by NaOH roasting to remove Cr, Al, and Si, as well as its effect on Ni and Co extraction in the subsequent pressure acid leaching process was investigated. Characterization results of X-ray diffraction (XRD) and scanning electron microscopy/X-ray energy dispersive spectroscopy (SEM/XEDS) show that goethite is the major Ni-bearing mineral, and chromite is the minor one. Experimental results show that the leaching rates of Cr, Al, and Si are 95.6wt%, 83.8wt%, and 40.1wt%, respectively, under the optimal alkali-roasting conditions. Compared with the direct pressure acid leaching of laterite ores, the leaching rates of Ni and Co increase from 80.1wt% to 96.9wt% and 70.2wt% to 95.1wt% after pretreatment, respectively. Meanwhile, the grade of acid leaching iron residues increases from 54.4wt% to 62.5wt%, and these residues with low Cr content are more suitable raw materials for iron making.

Preparing titanium dioxide from titania-rich slag (TiO2 73wt%) by molten NaOH method has been developed. The effects of temperature and reaction time on the titanium conversion were investigated. The results showed that temperature had significant influence on the titanium conversion as well as the structure of the product. About 92% of titanium in the titania-rich slag could be converted after reacting with NaOH at 500°C for 1 h. Metatitanic acid was formed through the steps of washing treatment, acid dissolution, and hydrolysis. Well-dispersed spherical titanium dioxide particles with an average size of 0.1–0.4 μm can be obtained by calcination of metatitanic acid. In addition, the content of titanium dioxide in the product is up to 98.6wt%, which can be used as pigments after further treatment of coating and crushing.

Rutile titanium dioxide (TiO2) white pigment has been prepared by doping and calcination of metatitanic acid (H2TiO3) obtained by the NaOH molten salt method. It was found that the properties of the rutile TiO2 sample prepared were improved by adding K2O, P2O5, Al2O3, and rutile nuclei. The X-ray diffraction (XRD) results show the rutile content of the rutile TiO2 sample prepared is 97%, and scanning electron microscopy (SEM) results show that the rutile TiO2 particles prepared have well-shaped morphology and narrow particle size distribution. The purity and color performance of the rutile TiO2 sample prepared approached the commercial TiO2 pigment standards.

Potassium titanate (K4Ti3O8) was synthesized by the reaction between ilmenite and concentrated KOH solution in the atmosphere of nitrogen, still air, and oxygen, respectively. The obtained samples were systematically investigated by X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometer (ICP-OES), and scanning electron microscopy (SEM). XRD results indicate that K4Ti3O8 have been synthesized in different atmospheres. The oxidizing atmosphere could enhance the conversion rate of Ti from ilmenite to K4Ti3O8, and Fe(II) is easily oxidized to trivalent iron Fe(III) during the reaction. Furthermore, SEM images show that the different atmospheres have significant effect on K4Ti3O8 crystal morphology and particle size. Well shaped K4Ti3O8 crystals are obtained in nonoxidizing atmosphere.

CaTiO3 was decomposed by alkaline roasting method for the production of TiO2. The process included alkaline roasting, water leaching and acid leaching steps. In the alkaline roasting step, the factors such as roasting temperature and NaOH/CaTiO3 molar ratio were investigated and 99.5% TiO2 could be extracted from CaTiO3. In addition, it is believed that only ion-exchange between Ca2+ and Na+ takes place, while the structure of TiO32− in CaTiO3 was not destroyed during the roasting process. In the acid leaching step, Ca(OH)2 could be completely leached at pH = 6−7 and Na2TiO3 was completely hydrolyzed simultaneously. The crystal structure of the leached sample seemed to be affected by pH and sequent calcination temperature. Finally, a flowsheet was proposed for the extraction of TiO2 from perovskite.

Oxalic acid was used for the removal of iron from the intermediates of ilmenite leached by KOH liquor. Various parameters, such as pH, temperature, initial oxalate concentration, and illumination were investigated. Meanwhile, it was found that orthorhombic crystal Ti2O2(OH)2(C2O4)·H2O formed as the leaching proceeded. Scanning electronic microscope (SEM) images implied that the formation of Ti2O2(OH)2(C2O4)·H2O with good crystallinity proceeded through three stages. Calcining Ti2O2(OH)2(C2O4)·H2O, anatase (350·C) or rutile (550·C) type TiO2 was obtained, respectively. Element analysis found that the calcined product contained 94.9% TiO2 and 2.5% iron oxide, but only about 1600 ppm dissolvable iron oxide was left, which indicates that oxalic acid was comparatively effective on iron oxide removal from the intermediates. Finally, an improved route was proposed for the upgrading of ilmenite into rutile.

Highly ordered periodic mesoporous organosilicas (PMOs) with the 1,4-diureylenebenzene moieties incorporated into the silica framework walls were synthesized through co-condensation of bissilylated 1,4-diureylenebenzene and tetraethyl orthosilicate using triblock copolymer P123 as a structure-directing agent in acidic solutions. These PMOs were characterized by powder X-ray diffraction, N2 adsorption/desorption measurements, 13C and 29Si solid state NMR spectra, FT-IR, SEM, TEM and elemental analysis. It is observed that the PMOs containing 1,4-diureylenebenzene groups inside the pore walls possess large surface area ranging from 423 to 223 m2/g and uniform mesopores between 4.7 and 6.2 nm. With the increasing component of the bissilylated precursor to 10 mol%, PMOs with a rod-like morphology were obtained. When the fraction of the bridged organosilane exceeds 10 mol% in the start mixture, the orderness of the PMOs decreases and the mesoporous wall structure collapses under the adopted synthetic conditions.

Mesoporous SBA-15 was functionalized with imidazole groups by a facile two-step post-grafting method. The resultant material has been characterized by powder X-ray diffraction, N2 adsorption/desorption measurements, FT-IR, NMR and elemental analysis to confirm the ordered mesoporous structure and the functionalization of the imidazole groups and employed as an adsorbent of Cr(VI) from aqueous solutions at room temperature. It was showed that the imidazole group can be introduced into the mesoporous channel by the postsynthesis route with high content under controlled reaction conditions. The imidazole-functionalized material exhibits high adsorption capacity of 113 mg/g for Cr(VI) and fast adsorption rate of less than 1 h in aqueous solutions. Equilibrium data were well fitted to the Langmuir adsorption isotherms.

An organic–inorganic hybrid mesoporous material, iminodiacetic acid (IDA)-modified mesoporous SBA-15, was prepared by a two-step post-grafting method. By means of solid-state 13C CP-MAS NMR, thermogravimetic analysis (TGA), Fourier transform infrared (FT-IR), as well as X-ray photoelectron spectroscopy (XPS), the structural and physicochemical properties of the materials were characterized. The cadmium(II) uptake experiments show that the iminodiacetic acid-modified mesoporous SBA-15 (IDA-SBA-15) exhibits excellent ability to remove cadmium(II) from aqueous solutions. The cadmium(II) adsorption isotherm of iminodiacetic acid-modified mesoporous SBA-15 (IDA-SBA-15) is in good accordance with the Langmuir equation.

A flexible, controllable and high-yield (ca. 100%) morphosynthesis route is provided to fabricate perfect monodispersed SBA-15 microspheres. A large series of characterization results (SEM, TEM, XRD, and nitrogen adsorption–desorption analysis) have demonstrated how mesitylene and inorganic salt can drastically influence not only the textural properties of the materials on the nanometer scale but also the morphology of the silica at the micrometer level. Both mesitylene and inorganic salt are necessary for the formation of the silica spheres, in addition to their influence on inner structure of the resulting materials. The absence of stirring is also necessary to achieve perfect SBA-15 microspheres. The use of mesitylene and inorganic salt in the triblock copolymer/silica source/acid solution system introduces more flexibility and diversity into the designed synthesis of shaped mesoporous materials, resulting in well-defined SBA-15 spheres (a few micrometers in diameter) with pore size about 20 nm and pore volume about 2.0 cm3/g.

A new method was provided to synthesize three kinds of potassium titanates, namely K4Ti3O8, K2Ti2O5·xH2O and KTiO2(OH), by treating TiO2 with concentrated KOH solution under atmospheric pressure. The effects of reaction temperature and KOH concentration on the morphology and species of potassium titanates were determined by XRD, FESEM and ICP-OES. On the basis of the experimental results, a formation diagram has been constructed for the products synthesized in the TiO2–KOH–H2O system under atmospheric pressure with KOH concentration ranging from 55 to 80 wt.% and temperature ranging from 100 to 280 °C. From the experimental results, it can be concluded that well crystallized and single phase potassium titanates can be obtained under the certain temperature and KOH concentration.

Amine groups and polyol groups were sequentially grafted on mesoporous SBA-15 and MCM-41 to synthesize novel organic–inorganic hybrid mesoporous materials as boron adsorbents by a two-step post-grafting method. By means of small-angle XRD, N2 adsorption–desorption, solid-state NMR, Fourier transform infrared (FT-IR) and elemental analysis, the structure and physicochemical properties of the materials were characterized. The behaviors of the resulting adsorbents in adsorption of boron from solutions were investigated. The results show that the organic functional groups are successfully grafted on the SBA-15 and MCM-41, while the quantity and the distribution of the functional groups are varied due to the different pore properties of the materials. The boron adsorption isotherms of the adsorbents are in good accordance with the Langmuir equation. The polyol-functionalized SBA-15 was proved to be a promising adsorbent with the high adsorption capacity of boron up to 0.63 mmol/g as well as the high selectivity towards boron.

A chelating polymeric sorbent was developed by functionalizing poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate), poly(GMA-co-TRIM), with N-methylglucamine (MG) via a simple post-grafting route. The resulting well-defined millimeter-sized spheres of poly(GMA-co-TRIM)–MG had permanent macropore structures and low swelling degree, with accessible ligands of 1.84 mmol/g. The boron adsorption behavior of the sorbent was studied in batch mode by varying different parameters like the pH value, the initial concentration of boron and the adsorption time under noncompetitive conditions. It was found that the sorbent always maintained the high capacity between pH 2.6 and 8.6, in which the optimum pH was 7.5. The adsorption behavior of the sorbent obeyed the Langmuir isotherm well. The adsorption capacity of the sorbent for boron was in the same level as that of a commercially available N-methylglucamine-type polystyrene resin. However, it adsorbed boron more quickly. The sorbent also showed good durability and reusability through the fixed-bed adsorption tests. The study on the separation of boron from brine of salt lake showed a high selectivity of the sorbent, though the capacity for boron decreased due to the interference of diverse ions in brine.

•Atmospheric acid leaching extracts Ni and Fe under mild operating conditions.•This new technology separates valuable Ni and Fe from Si and Mg in the laterite ores.•This new technology can increase the grade of Ni in the hydrolyzate.•This new technology reduces costs by recycling acid media and recovering waste heat.•Hydrolyzate with high Ni content is a suitable raw material for ferro-nickel production.An innovative technology for processing saprolitic laterite ores from the Philippines by hydrochloric acid atmospheric leaching and spray hydrolysis is proposed. The factors that affect the hydrochloric acid atmospheric leaching of the laterite ores and spray hydrolysis of the atmospheric acid leach solution are investigated. Experimental results show that the leaching of Ni, Fe, and Mg is 98.9 wt%, 97.8 wt%, and 80.9 wt%, respectively, under optimal acid leaching conditions. The hydrolysis of Ni and Fe by the atmospheric acid leach solution approaches 100 wt% at the temperature range of 450–500 °C. Characterization results show that a serpentine mineral, nominally Mg3Si2O5(OH)4, is the major component and goethite, FeO(OH), is the minor one in the laterite ores. Treatment by hydrochloric acid atmospheric leaching breaks the mineral lattices of the laterite ores and makes amorphous silica the primary product in the atmospheric acid leach residue. The grade of Ni in the hydrolyzate increases to 4.55%. The hydrolyzate with high Ni content can be utilized for ferro-nickel production.Download full-size image