Sodium Hydroxide Leaching Research Articles

Sodium Hydroxide Leaching of Germanium from Lead Slag

Sodium Hydroxide Leaching of Germanium from Lead Slag

A New Route to Upgrading the High-Phosphorus Oolitic Hematite Ore by Sodium Magnetization Roasting-Magnetic Separation-Acid and Alkaline Leaching Process

In this paper, an innovative method is proposed to upgrade iron and remove phosphorus from high-phosphorus oolitic hematite ore by the sodium magnetization roasting–magnetic separation–sulfuric acid and sodium hydroxide leaching process. The process parameters of sodium magnetization roasting, acid leaching, and alkaline leaching were optimized. The results show that by only adopting traditional magnetization roasting–magnetic separation, an iron ore concentrate containing 57.49% Fe and 1.4% P2O5 at an iron recovery rate of 87.5% and a dephosphorization rate of 34.27% was produced, indicating that it is difficult to effectively dephosphorize and upgrade iron by the conventional magnetization roasting–magnetic separation process. The obtained rough magnetic concentrates were then subjected to acid and alkaline leaching steps, and the final product, assayed at 64.11% iron and 0.097% P2O5, was manufactured successfully. Moreover, the added NaOH could promote the mineral phase reconstruction of aluminum- and silica-bearing minerals during magnetization roasting and intensify the upgrading of iron as well as enhance the growth of iron grains.

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.

Recovery of tungsten trioxide from waste diamond core drilling crowns by nitric acid leaching

A cost-effective and simple hydrometallurgy procedure for recycling the diamond core drilling crowns by nitric acid leaching, followed by the sodium hydroxide leaching, has been developed. The effect of temperature, nitric acid/sodium hydroxide concentration, leaching time and stirring rate were studied. For the acid leaching process the optimal values for parameters were 60 °C, 1.0 M HNO3, 2.5 h, and 800 rpm. It has been noted that the key factors in the alkaline leaching process were temperature and NaOH concentration. For the alkaline leaching, the optimal parameters were 100 °C, 40% concentration of NaOH solution, and leaching time of 4 h. Identification and characterisation of products in all technological processes were performed by X-Ray Diffraction (XRD), scanning electron microscope using energy-dispersive X-ray spectroscopy (SEM-EDS), and laser desorption ionisation mass spectrometry (LDI-MS). The analysis of solutions in all phases was performed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The use of LDI-MS as a new approach to identify the products after phases in the recycling process was an important part of the study, and the results were consistent with the XRD analysis. The total tungsten recovery was over 95.6%, with a high purity of the obtained tungsten trioxide.

Recovery of zinc and lead from Yahyali non-sulphide flotation tailing by sequential acidic and sodium hydroxide leaching in the presence of potassium sodium tartrate

The recovery of zinc and lead from Yahyali non-sulphide flotation tailing using sulfuric acid followed by sodium hydroxide leaching in the presence of potassium sodium tartrate was experimentally investigated. In the acidic leaching stage, the effects of pH, solid-to-liquid ratio and temperature on the dissolution of zinc from the tailing were explored. 82.3% Zn dissolution was achieved at a pH of 2, a temperature of 40 °C, a solid-to-liquid ratio of 20% and a leaching time of 2 h, whereas the iron and lead dissolutions were determined to be less than 0.5%. The sulfuric acid consumption was found to be 110.6 kg/t (dry tailing). The leaching temperature had no beneficial effect on the dissolution of zinc from the tailing. The acidic leach solution was subjected to an electrowinning test. The cathode product consisted of 99.8% Zn and 0.15% Fe. In the alkaline leaching stage, the Pb dissolution increased slightly in the presence of potassium sodium tartrate. More than 60% of Pb was taken into the leach solution when the leaching temperature increased from 40 to 80 °C. The final leach residue was analyzed by XRD and XRF. The XRD results indicated that the major peaks originated from the goethite and quartz while minor peaks stem from smithsonite and cerussite. The XRF analysis demonstrated that the residue contained 70.3% iron oxide. Based on the sequential leaching experiments, the zinc and lead were excellently depleted from the flotation tailing, leaving a considerable amount of iron in the final residue.

Synthesis of Magnesium Aluminate Spinel Powder from the Purified Sodium Hydroxide Leaching Solution of Black Dross

Synthesis of magnesium aluminate spinel (MgAl2O4) was investigated by employing ball milling and co-precipitation methods. The starting materials (aluminum hydroxides) were obtained from the purified sodium hydroxide leaching solution of black dross. The characteristics of the synthesized spinel was analyzed through X-ray diffraction (XRD), scanning electron microscopy (SEM) images. In this work, the effect of calcination temperature and time on the formation of spinel by the two methods was compared. Calcination temperature showed a great effect on the formation of spinel in both methods. The results showed that the co-precipitation method has many advantages over the ball milling method. In ball milling method, complete conversion of the starting materials to spinel was impossible even at 1500 °C, while complete conversion to spinel was accomplished at 1000 °C for 5 h by the co-precipitation method. The average size of the spinel synthesized at these optimum conditions of the co-precipitation method was about 17 nm. A process can be developed to synthesize spinel from the black dross which is regarded as hazardous materials.

Basic Leaching Behavior of Mechanically Activated Zinc Plant Residue

Zinc plant residue is a secondary metal source because it has precious metals such as zinc and lead. However, since this residue contains partial ferrite structure, there is no large-scale recovery in metallurgy industry. The aim of this study is to investigate the effect of mechanical activation of zinc plant residue in sodium hydroxide leaching. The results showed that mechanical activation obtained from high-energy mill had positive effect on the leaching of metals under condition of limited grinding time. Mechanical activation over 1 min caused the increase in particle size. It was also determined that specific surface area decreased due to onset of agglomeration of fine particles on the surface. Leaching efficiency of long-time milled residue was lower than short-time milled material’s leaching. It was determined that lead dissolution from zinc plant residue was higher than zinc dissolution in all experiments due to the presence of zinc in ferrite structure as franklinite form. Furthermore, sodium hydroxide leaching of this residue could be considered as a selective leach, since no iron was present in the solution.

Recovery of gibbsite from secondary aluminum production dust by caustic leaching

The disposal of aluminum bearing dust can cause heat and gases, as well as the potential generation of leachate from landfills. In this research, we suggested a two-step process - leaching and precipitation - for recovering gibbsite from secondary aluminum production dust. First, a sodium aluminate solution, containing about 20 g/L of aluminum, was prepared using 1 M of sodium hydroxide leaching. Precipitation of the gibbsite was then conducted for 30 min after a pH adjustment. As the results indicate, the overall aluminum recovery rate was about 87% by weight after leaching and precipitation, and the major component of the precipitate was Al(OH)3 based on an X-ray diffraction(XRD) analysis.

Ball Milling Treatment of Black Dross for Selective Dissolution of Alumina in Sodium Hydroxide Leaching

A process consisting of ball milling followed by NaOH leaching was developed to selectively dissolve alumina from black dross. From the ball milling treatment, it was found that milling speed greatly affected the leaching behavior of silica and the oxides of Ca, Fe, Mg, and Ti present in dross. The leaching behavior of the mechanically activated dross was investigated by varying NaOH concentration, leaching temperature and time, and pulp density. In most of the leaching conditions, only alumina and silica were dissolved, while the leaching percentage of other oxides was negligible. The leaching percentage of silica decreased rapidly to nearly zero as pulp density increased to 100 g/L. At the optimum leaching conditions (5 M NaOH, 50 °C, 2 h, pulp density of 100 g/L), the purity of Al in the leaching solution was higher than 98%, but the leaching percentage of alumina was only 35%.

Successive desilication and dealumination of HZSM-5 in catalytic conversion of waste cooking oil to produce aromatics

An integrated modified HZSM-5 was prepared by sodium hydroxide leaching and followed by hydrothermal process in series, and the co-modified zeolites were then used to conduct the catalytic fast pyrolysis of waste cooking oil to investigate whether an enhanced production of aromatics could be obtained. X-ray diffraction, N2 adsorption–desorption, TEM and NH3-TPD were utilized to characterize the modified zeolites. Experimental results indicated that the crystal structure of HZSM-5 was damaged as alkali treatment time was beyond 4h, and a micro-mesopore hierarchical system was created inside the zeolites. Simultaneously, the strong acid sites decreased with the increment of modification time, while the weak acid sites performed an opposite inclination. The relative yields of aromatics and olefins presented deviation when alkali treatment time exceeded the specific limitation, and a moderate alkali treatment time of 4h was beneficial for promoting the yield of aromatics.

Enrichment of Sc2O3 and TiO2 from bauxite ore residues

As a major byproduct generated in the alumina industry, bauxite ore residue is an important reserve of scandium and titanium. In this study, the feasibility and mechanism of enriching Sc2O3 and TiO2 from a non-magnetic material, which was obtained from carbothermal reductive roasting and magnetic separation of bauxite ore residue, were investigated based on a two-step (acidic and alkali) leaching process. It was revealed that approximately 78% SiO2 and 30–40% of CaO, FeO and Al2O3 were removed from a non-magnetic material with 0.0134wt.% Sc2O3 and 7.64wt.% TiO2 by phosphoric acidic leaching, while about 95% Al2O3 and P2O5 were further leached by subsequent sodium hydroxide leaching of the upper-stream leach residue. A Sc2O3-, TiO2- rich material containing 0.044wt.% Sc2O3 and 25.5wt.% TiO2 was obtained, the recovery and the enrichment factor of Sc2O3 and TiO2 were about 85% and 5, respectively. The enrichment of Sc2O3 was attributed to higher pH (>3.3) of phosphoric acid solution than its dissolution pH0, and the enrichment of TiO2 was mainly associated with the insoluble perovskite (CaTiO3) in the acidic solution at ambient temperature. As Sc2O3 and TiO2 cannot be dissolved in the alkali solution, they were further enriched in the leach residue.

Kinetic and Thermodynamic Study of Aluminum Recovery from the Aluminum Smelter Baghouse Dust

The recovery and utilization of metals from wastes are important for saving metal resources, as well as for protecting the environment. There are various types of solid wastes that have different origins and forms. Elemental and mineralogical composition of the wastes depends on the industry where they come from; therefore, the recovery processes for these materials are widely different. In general, the recovery of metals from ores and/or concentrates is carried out by extractive metallurgy methods comprising pyrometallurgy, hydrometallurgy, and electrometallurgy. In this research, sodium carbonate and sodium hydroxide leachings with different experimental conditions are tested for the aluminum dissolution. Also, a kinetic and thermodynamic study of sodium hydroxide leaching of the aluminum smelter baghouse dust is conducted. It is determined that when the solids content is 10 g/L, the overall reaction rate is controlled by pore diffusion and the activation energy is calculated to be about 4.8 kcal/mol. At temperatures below 100 °C, the stable form of the recovered compound after leaching is sodium aluminate.

Unfolding the complexities of mechanical activation assisted alkali leaching of zircon (ZrSiO4)

Sodium hydroxide leaching of non-activated and mechanically activated zircon (ZrSiO4) from Indian beach sands has been investigated. Mechanical activation is carried out up to 480min using a planetary mill. The activated samples were characterised in terms of morphology, particle size distribution and degree of amorphisation. Milling resulted in a significant reduction in median size from 195 to 0.99μm and the degree of amorphisation reached a value of ~90% after about 100min of milling. Leaching was carried out with 2.5–7.5M of NaOH in the temperature range of 35–85°C and a solid to liquid ratio of 1:20 (w/v). Mechanical activation resulted in a 2–4 fold increase in the solubility of ZrO2 and SiO2 components of zircon after 480min milling. Dissolution occurs non-congruently and the nature of dissolution was found to depend on the progress of leaching, temperature and mechanical activation time. The rate of dissolution of ZrO2 component exceeds SiO2 component under all the conditions of leaching. The kinetics of dissolution of both the components can be described in terms of a ‘shrinking core model with film diffusion’, and, depending upon mechanical activation time with the apparent activation energies of 17–41kJ/mol for ZrO2 component and 8–23kJ/mol for SiO2 component. The apparent activation energy for ZrO2 component shows an anomalous increase with an increase in mechanical activation time. The anomaly is explained in terms of opposing dual role of mechanical activation, namely enhanced dissolution due to increased reactivity with a simultaneous greater formation of the inhibiting Si-rich surface film/layer due to non-congruent nature of the dissolution.

Synthesis porous carbon-based solid acid from rice husk for esterification of fatty acids

A porous carbon solid acid was synthesized from biomass rice husk by incompletely carbonization, sodium hydroxide leaching and concentrated H2SO4 sulfonation. The solid acid was characterized by XRD, FT-IR, N2 adsorption-desorption and solid-state NMR spectroscopy. The characterization results reveal that the carbon solid acid shows ultra high surface area of 1233 m2/g and stronger acid strength than that of HZSM-5(Si/Al = 38) zeolite. The catalytic performance was tested by the esterification of oleic acid with methanol. The results indicate that this solid acid catalyst is an excellent catalyst compared with other conventional solid acid.

English

Sweet sorghum (Sorghum bicolor (L.) moench), a crop that is grown by subsistence farmers in Zimbabwe was used to extract silica gel in order to assess its possible use as a raw material for the production of silica-based products. The gel was prepared from sodium silicate extracted from sweet sorghum bagasse ash by sodium hydroxide leaching. Results show that maximum yield can be obtained at pH 5 and with 3 M sodium concentration. The silica gel prepared at optimum pH 5 had a bulk density of 0.5626 g/cm3 and anestimated porosity of 71.87%. Silica gel aged over 10 h had improved moisture adsorption properties. X-ray fluorescence (XRF) determinations show that the silica content in the ash is 40.1%. Characterization of sweet sorghum ash and silica gels produced at pH 5, 7 and 8.5 by Fourier Transform Infrared spectroscopy gave absorption bands similar to those reported by other researchers.Transmission electron micrographs show that silica prepared under optimum conditions is amorphous and consisted of irregular particles. Sweet sorghum proved to be a potential low cost raw material for the production of silica gel.   Key words: Silica gel, sweet sorghum, extraction, ash, bagasse, X-ray powder diffraction (XRD).

Kinetics of sodium hydroxide leaching of scheelite

It has been reported, historically, that scheelite (CaWO 4) cannot be decomposed using sodium hydroxide under commercial conditions. However, a mechanochemical leaching process using caustic soda at elevated temperature + pressure for the treatment of scheelite has been developed and put into practice successfully in China since the late 1980s. This technology can treat not only high-calcium-content wolframite, but also scheelite–wolframite concentrate blends and even scheelite concentrates directly. Recently, a thermodynamic analysis was made to explain the digestion of scheelite by NaOH, but the kinetics of this leaching process is still not well understood. In this study, the influence of variables, such as temperature, NaOH concentration and mineral particle size on NaOH leaching of scheelite was studied. The experimental data agreed quite well with the shrinking core model for leaching. The leaching rate was controlled by a surface chemical reaction, with an apparent activation energy of 64.6 kJ/mol and a reaction order of 1.74. The kinetics equation of the process was established as: 1 − ( 1 − α ) 1 3 = 23.67 × 10 − 3 [ N a O H ] 1.74 r 0 − 1 e ( − 64600 8.314 T ) t

A green process for recovering nickel from nickeliferous laterite ores

A novel process was proposed for recovering nickel from nickeliferous laterite ores. First of all, silicon and magnesium were removed from lateritic ore by high concentration sodium hydroxide leaching and carbonation respectively, so as to enrich nickel. Then the method of ammonia carbonate leaching was adopted to recover nickel from the carbonized slag, and the remaining residue was used as a raw material for recovering iron. The effects of temperature, ammonia carbonate concentration, liquid/solid ratio and stirring speed on the recovery of nickel were examined. When the leached residue reacted with ammonia carbonate (6 mol·L −1) in a ratio of liquid-to-solid of 5:1 at 60 °C for 150 min at the stirring speed of 300 r·min −1, approximate more than 95% nickel was recovered. During the whole process, there was no contamination produced and the chemical raw materials were recycled, thus the process was a green technology that having good social benefit.

Recycling EAF dust leaching residue to the furnace: A simulation study

Simulation programs have been devel oped to study the effect of recycling the electric arc furnace dust leaching residues to the furnace. Residues from sulfuric acid and sodium hydroxide leaching have been tested. Results enable the furnace-leaching response to be defined in accord with the recycling rate and conditions for zero stabilization to be determined. Either of the two alternative treatments eliminates the resulting environmental problem. Regarding the management and minimization of residues, the alkaline treatment route is more favorable than the acid one. The preliminary economic evaluation of the alkaline method is very promising.

Demineralization Study of Indian Assam Coking Coal by Sodium Hydroxide Leaching

The purpose of this study was to examine the ash removal efficiency of sodium hydroxide leaching from Assam coking coal so that it could be used for the manufacture of graphite electrodes. The parameters tested were sodium hydroxide concentration, panicle size of coal, NaOH solution / coal ratio, leaching temperature and time, and heat treatment of coal. Increase in NaOH concentration up to 500 gL −1 was found to increase the extent of ash removal. The ash content of the leached coal decreased with decrease in particle size, but very finely ground (− 72 mesh) particles reduced the ash removal rate. Increase in leaching temperature (50-120°C) and time (30-180 min) considerably reduced the ash content of the leached coal. Heat-treated (at 1300°C) coal (i.e., coke) has much lower ash removal efficiency than raw coal.

Recovery of vanadium from oil-fired boiler slag by direct leaching and subsequent solvent extraction.

The recovery of vanadium from oil-fired boiler slag was examined, using the techniques of direct leaching and subsequent solvent extraction. Hydrochloric acid leaching showed the best extraction capability for vanadium and other metals in the oil-fired boiler slag. Sodium hydroxide leaching had the highest selectivity for vanadium. A combination of these two leaching methods hastened the recovery of metals and the separation of vanadium. Alternative processes of solvent extraction employed for metal separation from the leachate with a computer program and the best selected process was verified experimentally. As a result 94% of the vanadium in the oil-fired boiler slag was recovered in pure solution form.