Effect of Fe2O3 Content and Acid on the Leaching Behavior of Phosphorus from Dephosphorization Slag

Dephosphorization slag contains considerable quantities of valuable components, such as P2O5 and FeOx. To recover P from dephosphorization slag, selective leaching has been adopted to separate the P-concentrating mineral phase. In this study, the effect of Fe2O3 content in slag and acid on the leaching behavior of P from dephosphorization slag was investigated. It was found that a higher Fe2O3 content in slag resulted in a higher P2O5 content in the C2S–C3P solid solution. Increasing the Fe2O3 content in slag promoted the dissolution of P and simultaneously suppressed the dissolution of other elements, facilitating the selective leaching of P. In the hydrochloric acid solution, more than 81% of P could be dissolved from dephosphorization slag at pH 4, and the dissolution ratio of Fe was nearly zero, achieving excellent selective leaching. Although better selective leaching was also realized in the citric acid solution at pH 5, hydrochloric acid was considered the appropriate leaching agent from the perspective of leaching cost. Through selective leaching, almost all the C2S–C3P solid solution was dissolved from dephosphorization slag, and the Fe-bearing matrix phase and magnesioferrite remained in the residue. The residue with low P2O5 content can be reutilized in ironmaking or steelmaking processes.

Leaching of Phosphorus from Quenched Steelmaking Slags with Different Composition

Separating P2O5 from steelmaking slag is the key to achieving optimum resource utilization of slag. If the P-concentrating 2CaO∙SiO2–3CaO∙P2O5 solid solution was effectively separated, it can be a potential phosphate resource and the remaining slag rich in Fe2O3 and CaO can be reutilized as a flux in steelmaking process. In this study, a low-cost method of selective leaching was adopted, and hydrochloric acid was selected as leaching agent. The dissolution behavior of quenched steelmaking slags with different composition in the acidic solution was investigated and the dissolution mechanism was clarified. It was found that the P dissolution ratio from each slag was higher than those of other elements, achieving an effective separation of P and Fe. The dissolution ratios of P, Ca, and Si decreased as the P2O5 content in slag increased. A higher Fe2O3 content in slag led to a lower P dissolution ratio. Increasing slag basicity facilitated the dissolution of P from slag. The residue mainly composed of matrix phase and the P2O5 content decreased significantly through selective leaching. The P dissolution ratio from slag was primarily determined by the P distribution ratio in the 2CaO∙SiO2–3CaO∙P2O5 solid solution and the precipitation of ferric phosphate in the leachate. The P-concentrating solid solution was effectively separated from quenched steelmaking slag, even though hydrochloric acid was used as leaching agent.

Dissolution Mass Transfer of Trapped Phase in Porous Media

Dissolution mass transfer of trapped phase (TP) to flowing phase (FP) in porous media plays significant roles in hydrogeology, e.g., groundwater contamination by non-aqueous phase liquids, groundwater in-situ bioremediation, and geological carbon sequestration. In this chapter, this phenomenon is described. First, the physical and mathematical models are given. Afterwards, various conditions affecting this process, i.e., porous media characteristics, capillary trapping characteristics, flow bypassing, TP characteristics, and FP velocity, are discussed. These various conditions are described based on three parameters affecting the dissolution mass transfer: TP interfacial area ( A ), TP dissolution ratio ( ξ ), and mass transfer coefficient ( k ). Eventually, models to predict the mass transfer are formulated based on non-dimensional model. All of the data in this chapter are based on the experiments obtained by using micro-tomography and a series of image processing techniques from our latest works.

Dissolution mechanism of various elements from steelmaking slag into citric acid solution

To recycle valuable elements from steelmaking slag, their dissolution mechanism into citric acid solution has been investigated. First, the relationship between dissolution ratio of each element and initial concentration of citric acid (ci) was studied. Then, the concentrations of each species in solution were calculated through mass balance. Based on these results, it can been seen that whenci = 0.00104 mol/L, Ca2+, CaCit−, MgCit−, FeH2PO42+and CaHPO4are the predominant species in solution, and Ca5(PO4)3(OH)(s) precipitate can form easily, which may suppress the dissolution of elements. Whenciincreases to 0.0104 mol/L, dissolution ratio of each element increases significantly, except for iron. And the predominant species correspondingly change to Ca2+, Mg2+, CaCit−, MgCit−, H2Cit−, H3Cit and FeH2PO42+.

The kinetics of vanadium extraction from spent hydroprocessing catalyst by leaching with sulfuric acid at atmospheric pressure

The dissolution kinetics of vanadium from spent hydroprocessing catalyst was investigated by leaching with sulfuric acid at atmospheric pressure. The effects of stirring speed (400–800 rpm), initial sulfuric acid concentration (0.60–1.20 mol/l) and reaction temperature (373–423 K) on the vanadium dissolution were studied. The results showed that the vanadium dissolution ratio was practically independent of stirring speed at the investigated range, while increasing with the increases of sulfuric acid concentration and reaction temperature. The experimental data agreed quite well with the shrinking core model, with solid membrane diffusion as the rate controlling step. The apparent activation energy was calculated as 11.44 kJ/mol, and the reaction order with respect to sulfuric acid concentrations was determined to be 1.51. The kinetics equation of the leaching process was established as: 1 − 2x/3 − (1 − x)2/3 = 0.067[H2SO4]1.51exp[ − 11563/RT ]t.

Basicity Characterization of Imidazolyl Ionic Liquids and Their Application for Biomass Dissolution

Alkalinity determination is of crucial significance for the applications of basic ionic liquids with imidazolyl. In this work, the ionization constant pKb value and acid function H- values of ionic liquids synthesized were calculated by pH method and UV spectrum-Hammett method. The dissolution ratio of biomass in these ionic liquids was measured at different temperatures. Finally, the relationship between the alkalinity and structure of these ionic liquids was discussed, and the relationship between the alkalinity of ionic liquid and the dissolution mechanism biomass was also discussed. The results show that the basicity of carboxylate ionic liquids is determined mainly by their anions, whereas cations take some finely tuned roles. Furthermore, cations and anions are equally important and are involved in dissolution mechanisms.

Ultrasonic-Assisted Dissolution of Polystyrene in Decahydronaphthalene for the Preparation of Poly(Cyclohexylethylene)

Dissolution process of polystyrene in decahydronaphthalene solution was conducted and compared under different conditions. The effects of dissolution time and temperature on the dissolution ratio of polystyrene were performed with the assistance of ultrasonic and mechanical agitation, respectively. The dissolution ratio of polystyrene increased with the increment of dissolution time and dissolution temperature, polystyrene dissolved faster under ultrasonic-assisted process. The polystyrene dissolution kinetic model was developed and used to calculate the dissolution rate constant. The kinetic model showed good agreement with the experimental data, and the dissolution rate constant indicated that ultrasonic can obviously enhance the dissolution process of polystyrene in decahydronaphthalene solution.

Numerical Simulation of Coal Oil Water Slurry Gasification Process in New-Type Coal Water Slurry Gasifier

The gasification process of coal oil water (COW) slurry in new-type coal water slurry(CWS) gasification furnace was studied with numerical simulation method. The temperature and concentration fields were obtained for the gasification furnace. The simulated results showed that the gasification effect of the new-type coal water slurry gasification is better than the common coal water slurry gasification. In the new-type gasification furnace, the average temperature is slightly increased and the carbon translative ratio is increased by 1.81%. The effective component (CO+H2) in coal gas at the outlet of the furnace is increased by 10.58%, and the concentration of CO2and H2O is greatly decreased. The H2O dissolution ratio is greatly increased and the gasification effect is obviously better that that of the common coal water slurry.

Dissolution Behavior of Dicalcium Silicate and Tricalcium Phosphate Solid Solution and other Phases of Steelmaking Slag in an Aqueous Solution

Most of the phosphorus in slag forms a solid solution of dicalcium silicate (C2S) and tricalcium phosphate (C3P), and the process used to separate this solid solution from the matrix phase is the same technology used to separate P from other valuable elements such as Mn and Cr containing in the matrix phase. Although it is known that the solubility of C2S in an aqueous solution is much greater than that of C3P, the solubility of the solid solution and that of the matrix phase have yet to be investigated. To clarify the possibility of selectively extracting P from slag through a leaching process, the dissolution behaviors of the solid solution at various compositions and that of the matrix phase were investigated. The following results were obtained: The dissolution ratio of Ca to the aqueous solution at pH = 7 was close to 1.0 in the case of pure C2S and decreased greatly with increasing C3P content. The dissolution ratio of P was about 0.1 and did not change relative to the C3P content. When the ratio of C3P in the solid solution was higher than 0.3, hydroxyapatite (HAP) formation was observed in the residue. The dissolution ratio of P increased for 30 min, and after reaching the maximum value, started to decrease owing to the precipitation of HAP. The dissolution ratio of each element from a glassy slag sample (matrix phase) was lower than that from the solid solution at every pH level.In this study, the possibility to extract a solid solution containing P without dissolving the matrix phase was found through the use of an aqueous solution at pH = 7, although the dissolution ratio of P was not sufficiently high.