Leaching Stage Research Articles

Leaching behavior and environmental risk assessment of toxic metals in municipal solid waste incineration fly ash exposed to mature landfill leachate environment

Solidification/stabilization pretreatment + landfill disposal in municipal solid waste (MSW) landfill sites is a widely accepted MSW incineration (MSWI) fly ash (FA) management strategy in China. However, in reality, the stability of FA disposed in MSW landfill sites may be affected by the organic landfill leachate environment. The purpose of this study was to explore the mobility and environmental risks of six toxic metals (Mn+, Pb/Zn/Cu/Cd/Cr/Ni), from raw and solidified/stabilized FA, by simulating a leaching environment with mature landfill leachate (MLL). The leaching of Mn+ mainly occurred in the early leaching stage, and their leaching behavior was controlled by the diffusion of surface Mn+ in the FA matrix. The destructive effect of dissolved organic matter (DOM) on the local precipitation-dissolution equilibrium of FA-leachate interface, the formation of non-adsorptive DOM-Mn+ complex (easy to migrate), and the competitive effect of DOM on the binding sites of Mn+ on the surface of the FA matrix may play an important role in increasing the leaching level of most Mn+. By contrast, the potential of solidified FA in reducing the environmental risk level of leached Mn+ was better than that of stabilized FA. However, the immobilization capability of solidification/stabilization pretreatment on various types of Mn+ in FA should be judged according to their practical disposal environment. Compared to MLL leaching tests, Acetic Acid Buffer Solution Method (HJ/T300-2007) can effectively strengthen the exposure environment and provide a reliable reference level of environmental risk for MSWI FA disposed in MSW landfill sites.

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.

Silicon recovery from diamond wire saw silicon powder waste with hydrochloric acid pretreatment: An investigation of Al dissolution behavior

Silicon recovery from diamond wire saw silicon powder (DWSSP) waste is of great significance for increasing production profits and alleviating hazardous effects on the ecological environment. The purity of recovered silicon powder is determined by the purification efficiency during acid leaching pretreatment. Because the metallic impurities present in DWSSP are mostly physically mixed rather than chemically bound, the reaction rate is very fast in the initial stage of acid leaching, whereas it is difficult to dissolve the retained impurities in the later stage with the depletion of metal fragments adhered on the surface of the silicon matrix. Many prior studies have failed to consider the retained metallic impurities that reside in the inner silicon particle surfaces. Therefore, this study investigates the dissolution behavior of retained impurities via the dissolution of Al in HCl solution as an example. Thermodynamic results indicate that the Al dissolution process is dominated by entropic changes (ΔS0), rather than enthalpic changes (ΔH0). Furthermore, the dissolution behavior of Al is in accordance with the diffusion-controlled step in the Avrami mode, and the kinetic parameters were found to be A=5.85×107, Ea=49.27kJ·mol-1, and m<1. The determined dissolution behavior provides a clear understanding of the removal of retained metallic impurities from DWSSP via an acid leaching pretreatment. This study provides enlightenment for the further purification of silicon recovered from DWSSP waste.

Selective extraction of valuable metals from spent EV power batteries using sulfation roasting and two stage leaching process

Selective extraction of valuable metals from spent electric vehicles (EVs) power batteries was undertaken by a sulfation roasting-water leaching-acidic leaching process. After sulfation roasting (acid-to-lithium molar ratio (nH2SO4:nLi) = 0.95, 550 °C and 3 h), the roasted products were subject to the 1st stage of water leaching. Under optimum conditions (30 °C, 2 h and liquid-to-solid (L/S) ratio of 4 mL/g), the extraction of Li and Mn reached 90% and 10%, whereas extractions of Co and Ni were negligible. The water leaching residues were then treated by the 2nd stage of acidic leaching (2 mol/L H2SO4 solution with L/S ratio of 5 mL/g at 60 °C for 2 h) which resulted in an additional 98% Ni, 97% Co and 90% Mn being leached from the residue. An investigation of the phase transformation mechanism indicated that the extraction behaviors of valuable metals might be induced by the different reduction pathways of the metals while controlling the roasting conditions. With roasting temperature <550 °C and roasting time <2 h, Li within the crystalline LiCoxNiyMn1-x-yO2 was de-intercalated and transformed to soluble Li2SO4, while Ni, Co and Mn in the LiCoxNiyMn1-x-yO2 decomposed to MnCo2O4 and Ni6MnO8 because of the co-existence of sulfuric acid and carbon reductant from the graphite anode material. When nH2SO4:nLi was higher than 1.2, Li was further converted to Li2Mn2(SO4)3. Under the conditions of roasting temperature > 550 °C and roasting time >2 h, MnCo2O4 and Ni6MnO8 were further reduced into low-valence states CoO and (NiO)0.75(MnO)0.25. These results provide a fundamental basis for the development of an efficient and selective extraction strategy for the recycling of valuable metals from spent EV power batteries.

Evaluation of microwave acid baking on Indian red mud sample

The present study validates the application of microwave heating for acid baking of red mud and the dissolution of metallic values during water leaching. The effect of microwave power and exposure time is evaluated on the sulfation and decomposition mechanism of the constituent phases present in the red mud. It is inferred that the processing time can be significantly reduced to less than 3 min for the enrichment of Fe (~41%) and Ti (~15%) in the residue by employing microwaves as a heating source. The low solution pH value (<2) for baking experiments with less than 90 s synergized to improve metal dissolution during the leaching stage. The metallic values in the solution were precipitated and calcined to produce a product containing refractory phases such as mullite, alumina, and hematite, which can be segregated using a conventional magnetic separation process. The dissolved titanium values interact with iron values and occur in ilmenite and pseudobrookite phases in the calcined precipitate. The microwave-assisted acid baking process is a potential first step process for the complete utilization of red mud and separation of iron and titanium values.

Genetic mechanisms of Permian Upper Shihezi sandstone reservoirs with multi-stage subsidence and uplift in the Huanghua Depression, Bohai Bay Basin, East China

Braided river sandstones in the Permian Upper Shihezi (US) Formation in the Huanghua Depression, Bohai Bay Basin, East China, are reservoirs with large accumulations of hydrocarbons. The Upper Paleozoic formations, including the Carboniferous and the Permian strata experienced multi-stage of subsidence and uplift in the past 320 Ma, leading to occurrence of subaerial exposure and deep burial of the Permian US sandstones. Due to complex tectonic evolution, the Upper Paleozoic formations in different tectonic zones of the Huanghua Depression experienced various burial-thermal histories, resulting in the development of long-term open (LTO), early-open to late-closed (EOLC), and long-term closed (LTC) geochemical systems in different Permian US sandstones, as well as different evolutionary patterns of diagenesis and reservoir quality. After extensive diagenetic alteration, the present sandstones are primarily quartzose, subfeldsarenite, and sublitharenite sandstones. Pores in shaly sandstones and fine-grained sandstones were destroyed extensively, only pebbly to medium-grained sandstones can be potential effective reservoirs. The Permian US sandstones with the LTO systems, which are currently overlain by the Paleogene strata and buried less than 2500 m, experienced two stages of meteoric freshwater leaching and are characterized by extensive feldspar dissolution and weak precipitation of authigenic kaolin and quartz. Intergranular and intragranular pores dominate the 10–20% porosity, and permeability ranges from 1mD to 800 mD. The Permian US sandstones with the EOLC systems, which are currently overlain by thick Jurassic and Cretaceous strata on a regional scale and buried deeper than 3000 m, experienced both meteoric freshwater leaching and deep burial leaching and are currently characterized by extensive feldspar dissolution, extensive kaolin precipitation, and weak-moderate quartz cementation. Intragranular secondary pores and kaolin intercrystal pores dominate the 5–15% porosity, and permeability ranges from 0.1 mD to 10 mD. The Permian US sandstones with the LTC systems, which are currently overlain by a thick Permian Shiqianfeng Formation on a regional scale and buried deeper than 3000 m, experienced no meteoric freshwater leaching but only burial dissolution; they are currently characterized by extensive feldspar dissolution and extensive precipitation of clays and quartz cements. Intercrystal pores in the authigenic clay and intragranular secondary pores dominate the 5–10% porosity, and permeability ranges from 0.01mD to 1mD. Since the unconformities, overlying strata, and tectonic evolution relevant to the Permian US sandstone unit can be analyzed using seismic data, the proposed genetic models can support the predrill evaluation of reservoir quality of the Permian sandstones.

Increase in gold dissolution in copper ammonia thiosulfate solution via cobalt surface modification

When gold was leached using copper ammonia thiosulfate solution, the dissolution rate of gold decreased as the leaching time increased. The dissolution of gold powder with 44 and 77 μm particles was studied，and the results indicated that the dissolution rate was not decreased by surface passivation or the decrease in copper concentration but by the changes of the electronic structure of the gold surface caused by the change in the exposed crystal surface. The transmission electron microscopy images of the gold powder revealed that the high-index (220) and (311) crystal surfaces almost disappeared during leaching. Furthermore, the surface of gold consisted mainly of the low-index (111) crystal surface during the later stages of leaching. Owing to the changes in crystal surface, the work function of the gold surface increased from 6.56 to 6.95 eV, and the increase in work function hindered the loss of electrons from the gold surface. When cobalt was used to modify the gold surface, the work function decreased from 6.56 to 5.99 eV. The leaching results indicated that the cobalt modification increased gold dissolution, and the gold leaching percentage was increased by 40% within 8 h. the tendency of gold to dissolve more easily after it underwent surface modification was confirmed by the apparent activation energy of the surface-modified being lower than that of the fresh gold powder, the formation of intermediate products of Co3O4 with high oxidation ability and the galvanic interaction between cobalt and gold electrodes. Dry-grind was applied for gold concentrate calcine and different contents of cobalt powder to study the possibility of industrial application of this effect. The results showed that only adding 50 mg cobalt to 100 g gold ores was beneficial to gold leaching

DISSOLUTION BEHAVIOR OF CORROSIVE ANIONS FROM SABKHA SOIL SOUTHERN KUWAIT UNDER LONG TERM LEACHINGA

Corrosive anions leaching from sabkha soil due to continuous surface or subsurface flow, to ground water can create a corrosive environment for underground structures. This study aimed to investigate the amount of leached chloride (Cl−) and sulfates (SO42-) corrosive anions in terms of quantity and rate as a ratio of Total Dissolved Solids (TDS). In this study representative Sabkha soil sample from southern Kuwait was leached for 40 pore volumes with distilled water. It was determined that corrosive anions, chloride and sulfate, contributed to the high effluent TDS levels in the leachate. For TDS, the corrosive anions dissolution was over 50% in first leached pore volume, increasing to over 75% in the final stages of leaching. Results also showed a distinct tendency of reduction with pore volume in the concentration of SO4-2and CI-anions.These findings will help allow the prevention of underground structure corrosion by evaluating the numerical criteria for particular anions such as chloride and sulfate. In establishing appropriate stabilization techniques, it is necessary to consider anion dissolution as one of the prime criteria.

Pressure leaching of selenium and tellurium from scrap copper anode slimes in sulfuric acid-oxygen media

Copper anode slimes are essential secondary resources from which valuable metals, such as Cu, Se, Te, Au, and Ag, may be recovered. Herein, oxidation pressure leaching is proposed for the pretreatment of copper anode slimes to realize efficient extraction of Cu, Se, and Te and enrichment of Au and Ag in the leaching residue. Detailed investigations were conducted to determine the effects of sulfuric acid concentration, liquid-to-solid ratio, oxygen partial pressure, and reaction temperature on the recovery of Cu, Se, and Te. Results of thermodynamic analyses indicate that high pH values enhanced the transformation of insoluble Se2− into soluble HSeO3−, whereas low pH environments favored the presence of soluble Te(OH)3+. During the first stage of oxygen pressure leaching in H2SO4 (0.5 mol/L) with a liquid-to-solid ratio of 10 mL/g, the leaching ratios of Cu, Se, and Te were 99.54%, 96.95%, and 68.54%, respectively. The results of the SEM-EDS and MLA analyses of the first-stage pressure leaching residue indicate that the remaining Se and Te existed as Ag2Se and TeO2 phases, which were further dissolved in a H2SO4 solution (1 mol/L) with a liquid-to-solid ratio of 20 mL/g to obtain Se and Te leaching ratios of 99.5% and 98.6%, respectively.

Processing of ferromanganese fumes into high-purity manganese sulphate monohydrate

ABSTRACT A novel process for recovering manganese (Mn) values from two types of ferromanganese (FeMn) fumes (wastes from smelters) was developed incorporating several stages of leaching, roasting, and precipitation. Fumes containing high K (as K2O) were first leached in water at ambient conditions to recover K, purified to remove metal impurities, and precipitated as 99.9% pure K2SO4. The residues containing Mn and remaining impurities were then leached in sulfuric acid at 80 °C using oxalic acid as reductant yielding Mn sulphate liquors. The leach liquors were then purified to remove Fe at 95°C as jarosite at pH 2.8 and Fe(III) hydroxides at pH 5.5. Base and transition metal impurities were removed as sulfides. K, Na, Ca, and Mg were separated from Mn in a novel step based on precipitation of Mn hydroxide from the Mn sulphate liquors. Subsequent redissolution of Mn hydroxide in sulfuric acid under reducing conditions using oxalic acid produced a high purity Mn sulphate liquors containing <5 ppm of these impurities. After evaporation by boiling manganese sulphate monohydrate (MSM) was crystallized, achieving purity >99.5%. Another fume containing oil contaminants having low K was subjected to sulfation roasting to produce Mn sulphate. The calcine was water leached to produce Mn sulfate liquors and treated in a similar process to make high purity MSM. Novelty aspects of the proposed process include the recovery of K as a by-product and separation of Mn2+ from other impurities by its selective precipitation to produce a high purity Mn sulphate solution for MSM recovery. Implications: Ferro-manganese smelters discharge wastes (fumes) that are collected by bag filters or electrostatic precipitators and then store them on the ground with coverage to prevent their dispersion into the surrounding atmosphere. The work presented propose a process to reprocess these wastes into high purity manganese sulphate monohydrate (MSM). Processing of wastes containing high potassium as KOH also yields high purity potassium sulfate used as fertilizers. Some smelters spray oil onto the fume dumps to prevent material being blown onto the surrounding area. The oil-contaminated fumes have to be first roasted to burn off the oil, before they can be processed. The process developed therefore converts a hazardous waste into high purity MSM and potassium sulphate used in many applications.

Leaching kinetics of potassium and aluminum from phosphorus-potassium associated ore in HCl-CaF2 system

The leaching behaviours of potassium and aluminum from phosphorus-potassium associated ore in HCl-CaF2 media were investigated at temperature from 60 to 90 °C. The higher dissolved fraction of potassium compared with aluminum was found in this study though they were mainly incorporated into the same mineralogical phase of potash feldspar in the ore. Moreover, the dissolved fraction of potassium was always higher than aluminum in all the investigated conditions due to the existence of secondary precipitation phase such as amorphous alumino-silicate or the formation of insoluble AlF complex in the leaching process. In addtion, the leaching kinetic data were successfully examined by a semiempirical kinetic model based on the classical shrinking core model. It was found that there are two distinct stages in the leaching process and the kinetics of both stages follows the semiempirical kinetic model with chemical reaction being the rate-controlling step. The activation energies for potassium and aluminum from the ore were 39.031 and 44.260 kJ·mol−1 at first leaching stage, and 59.274 and 62.944 kJ·mol−1 at second leaching stage, respectively.

Uranium removal from tin smelter slag by bisulfate fusion and acidic leaching

Slag as secondary product (waste) of tin smelter still contains not only valuable elements e.g. Ti, Nb, Ta, Zr, Hf and rare earth elements, but also radioactives such as Th and U, wich are accumulated in the slag phase during the smelting. Due to valuable element content, the slag becomes major of interest in mineral processing industries, hence the slag needs to be decontaminated before it could be processed further.Common approach to reduce U content from the slag using leaching process is considered ineffective due to association of U with refractory elements e.g. Si and Ti in the slag. To break down the refractory phases, the fusion approach by using fusing agent is required in order to release U so that they could be leached out using mild lixiviant.In this research, potassium hydrogen sulfate (KHSO4) and sulfuric acid was used as fusing agent and lixiviant, respectively. The parameters studied includes molar ratio between fusing agent and refractory elements in slag, fusion temperature, fusion time, sulfuric acid concentration in lixiviant and pulp density during leaching stage. The studies so far demonstrated that optimum condition in U removal occurred at fusion temperature 400 °C, fusion time 2 hours, molar ratio of potassium hydrogen sulfate to tin slag 5, sulfuric acid concentration 2 M and pulp density 15 ml/gr. The maximum recovery of U was 85.6%, which was significant compared to the results using direct leaching without fusion (0.1%).

Application of solid-liquid extraction with organic acids for recovery of precious metal from technological waste in disuse

The electro and electronic industry has been increasing gradually, causing an increase in the generation of waste of electrical and electronic equipment, which have several components that have added value such as - for example - gold. Aiming at environmental protection, measures are sought for the recovery of these metals, through tests with several technologies such as leaching. This consists in separating the component from the solid part, transferring it to the liquid part, using acids. It is necessary to study acids that are less harmful to the environment. Thus, microprocessors of obsolete computers were collected, their characterization was carried out and the elements present in the pins were identified. After the characterization, the leaching stage was carried out, firstly with aqua regia; then with acetic and citric acids. The leaching results presented about 10 mg / L of gold with aqua regia and about 0.5 mg / L with citric acid.

From Electronic Waste to Suzuki-Miyaura Cross-Coupling Reaction in Water: Direct Valuation of Recycled Palladium in Catalysis.

From electronic waste to Pd-catalyzed reaction! The straightforward valuation of palladium recovered from electronic waste is reported here. Following a classical leaching stage, palladium is selectively extracted from a complex aqueous mixture of metallic cations into an organic phase. Afterwards, the judicious choice of a surfactant enables stabilization of palladium during back extraction cycles, and the direct preparation of an aqueous micellar solution, which can be employed in a model Suzuki-Miyaura cross-coupling reaction. Clean phase separation is observed, and distribution of all components between organic and aqueous phases is mastered. The proposed process avoids several waste generating steps dedicated to palladium isolation and ultimate purification, as well as the preparation of palladium pre-catalyst. This novel approach enables a better use of both natural resources and industrial wastes, through new cycles in circular economy.

Recycling drinking water treatment sludge into eco-concrete blocks with CO2 curing: Durability and leachability

Drinking water treatment sludge (DWTS) can be recycled into low-strength concrete blocks for construction use. The sodium sulfate resistance and leaching behaviours of the DWTS-derived blocks are investigated in this study. The experimental results show that the addition of DWTS degrades the sodium sulfate resistance of the concrete blocks, however CO2 curing compensates for such property, especially in the case of blocks incorporating 30% DWTS. The improvement can be attributed to the formation of crystalline CaCO3 during CO2 curing for microstructure refinement evidenced by X-ray Computed Tomography and Scanning Electron Microscopy. Leaching analyses show that Cu and Al concentrations increased with increasing DWTS content, and CO2 curing adversely increased the leachability of metals due to the decrease of pH, especially at early leaching stage. Nevertheless, the total leaching concentrations of Cu and Al after 60-day test is far below the prescribed limitations, regardless of samples subject to air curing or CO2 curing. In summary, sludge-derived blocks exposed to CO2 curing are safe and behave well in aggressive environments. Therefore, this study showcases a green technology that successfully recycling DWTS into value-added and durable concrete blocks with low environmental impacts.

The Effect of Energy Impacts on the Acid Leaching of Eudialyte Concentrate

ABSTRACT Using a combination of energy – dispersive X-ray spectroscopy, X-ray diffraction, X-ray fluorescence, Infrared and X-ray photoelectron spectroscopies, the effect of acids (sulfuric, hydrochloric, and nitric) and energy impacts (electrochemical, mechanochemical, high power electromagnetic pulses, ultrasound) on the leaching parameters of eudialyte concentrate was studied. Zr and Σ REE recovery after a single stage when using sulfuric acid was 91.5% and 82.4%, when using hydrochloric acid – 83.9% and 83.6%, when using nitric acid – 76.9% and 79.6%, respectively. Using sulfuric acid leads to the formation of the maximum amount of silicate gel and high loss of valuable components, while hydrochloric acid is highly aggressive to the process equipment. The possibility of nitric acid leaching intensifying by applying ultrasonic impacts was determined which disperse colloidal silicate gel, prevents the formation and precipitation of the gel on the mineral surface, provides the formation of numerous defects and microcracks on the eudialyte grains surface, including breakage thereof. Three stages of nitric acid leaching of eudialyte concentrate with an ultrasonic treatment in the first stage provide the highest recovery of zirconium (97.1%) and rare earth elements (94.5%) at a minimal loss of valuable components with silica gel. The process is recommended for commercialization.

Kinetic model of chromium release from argon oxygen decarburisation (AOD) slag in a neutral leachate

Valorisation of argon oxygen decarburisation (AOD) slag, a suitable recycling resource, is limited by the release of a notable amount of heavy metals, such as chromium. The mineralogical component of AOD slag was characterised by X-ray diffraction and scanning electron microscopy-energy-dispersive X-ray spectrometry. To explore the release kinetics of chromium from AOD slag, neutral leaching tests were performed at various temperatures. The results indicated the existence of two leaching stages: quick and slow leaching stages. In 2 h, the chromium release fraction increased sharply as the leaching time increased. As the leaching time increased, the chromium release rate gradually decreased. Based on the shrinking core model, chromium release kinetic models for the quick and slow leaching stages from the AOD slag were independently determined. The chromium release was controlled by solid product diffusion during the quick leaching stage and a complicated process in the slow leaching stage. The activation energy of chromium leaching was calculated based on the Arrhenius equation. Solid product diffusion was the velocity-determining step during the 2 h leaching process. In the slow leaching stage, chromium release was controlled by complicated hybrid control dominated by solid product diffusion.

Thermally activated serpentine leaching under flue gas conditions in a bubble column reactor operated at ambient pressure and temperature

Mineral carbonation of serpentine in the aqueous phase traditionally required high temperatures and pressures or additives to dissolve the mineral. This was accompanied by significant costs and important environmental burdens. This paper aims to demonstrate the feasibility of thermally activated serpentine leaching under ambient temperature and pressure. A simulated cement flue gas effluent with a CO2 content of 18.2% on a volume basis was used. The reaction was performed in a bubble column operated under a homogeneous regime. Agitation was required to improve solution mixing and CO2 diffusion.Results showed that the extent of Mg leaching was limited by the low solubility of silica in the aqueous solution. Once the solution was saturated with silica, CO2 dissolution acted only to cause precipitation of magnesium carbonate. Successive leaching with fresh water partially limited the problem as serpentine leaching declined with time. A total of 32% of the serpentine magnesium content was recovered from the solution after six successive leaching stages. For comparison, 33% of the content of the same material was dissolved when the reaction was performed in a batch reactor operated under 11.5 bar total pressure. In addition to costs and environmental improvements, these results have positive consequences on reducing complexity and retrofit issues for the application of mineral carbonation with serpentine.It was also shown that improving CO2 mass transfer through increasing agitation or superficial gas velocity accelerated serpentine leaching, highlighting the synergistic effect between the two reactions.

Characterization and A Preliminary Study of TiO&lt;sub&gt;2&lt;/sub&gt; Synthesis from Lampung Iron Sand

The purpose of this study is to characterize Lampung iron sand and to conduct preliminary experiments on the TiO2 synthesis which can be used for the manufacturing of functional food packaging. The iron sand from South Lampung Regency, Lampung Province that will be utilized as raw material. The experiment was initiated by sieving the iron sand on 80, 100, 150, 200 and 325 mesh sieves. Analysis using X-Ray Fluorescence (XRF) to determine the element content and X-Ray Diffraction (XRD) to observe the mineralization of the iron sand was conducted. The experiment was carried out through the stages of leaching, precipitation, and calcination. Roasting was applied firstly by putting the iron sand into the muffle furnace for 5 hours at a temperature of 700°C. Followed by leaching using HCl for 48 hours and heated at 105°C with a stirring speed of 300 rpm. The leaching solution was filtered with filtrate and solid residue as products. The solid residue was then leached using 10% H2O2 solution. The leached filtrate was heated at 105°C for 40 minutes resulting TiO2 precipitates (powder). Further, the powder was calcined and characterized. Characterization of raw material using XRF shows the major elements of Fe, Ti, Mg, Si, Al and Ca. The highest Ti content is found in mesh 200 with 9.6%, while iron content is about 80.7%. While from the XRD analysis, it shows five mineral types namely magnetite (Fe3O4), Rhodonite (Mn, Fe, Mg, Ca) SiO3, Quart (SiO2), Ilmenite (FeOTiO2) and Rutile (TiO2). The preliminary experiment showed that the Ti content in the synthesized TiO2 powder is 21.2%. The purity of TiO2 is low due to the presence of Fe metal which is dissolved during leaching, so that prior to precipitation purification is needed to remove impurities such as iron and other metals.

Leaching Kinetics of Rare Earth Elements from Fire Clay Seam Coal

Recovery of rare earth elements (REEs) from coal samples collected from the Fire Clay coal seam using diluted mineral acid solutions was investigated. The initial processing step was coal recovery using conventional froth flotation which concentrated the REEs in tailing material resulting in an upgrade to values around 700 ppm on a dry whole mass basis. Leaching experiments were performed on the flotation tailings material using a 1.2 M sulfuric acid solution adjusted to a temperature of 75 °C to study the extractability of REEs from coal material. The effect of particle size, leaching time, leaching temperature, and solid concentration on REE leaching recovery were evaluated. The kinetic data obtained from leaching over a range of temperatures suggested that the leaching process follows the shrinking core model with possibly a mixed control mechanism that may be a result of several heterogenous materials leaching simultaneously. Leaching recovery increased rapidly at the beginning of the reaction then slowed as the system reached equilibrium. The apparent activation energy determined from test data obtained over a range of temperatures using 1 M sulfuric acid was 36 kJ/mol for the first 20 min of reaction time and 27 kJ/mol for the leaching period between 20 and 120 min. The leaching of light REEs during the initial stage was determined to be driven by a chemical reaction, followed by the formation of a product layer, which required lower activation energy in the later stage of leaching. In regards to the heavy REEs, the major mechanism for leaching is desorption and the product layer formation does not affect the heavy REEs significantly.