Dissolution Kinetics of Chlorine from Iron Ore Sintering Dust

Chlorine is generated during iron ore sintering, mostly in the form of alkali chlorides and primarily accumulates in sintering dust, which must be removed before reusing. In this study, an in-situ monitor leaching system based was designed to detect chloride ion water leaching behaviors in real-time and improve the understanding of chlorine dissolution kinetic behaviors in water. Various parameters, including water leaching temperature, solid/liquid ratio, stirring speed, particle size and surfactant addition have been studied. Meanwhile their chlorine dissolution data exhibited a good fit to Stumm’s kinetic models. The results of kinetics analysis and transition state theory calculation on apparent activation energy demonstrated that the dissolution process was controlled by diffusion at low S/L ratio, while changed to be controlled by surface chemical reaction as the S/L ratio increased. Furthermore, increasing both temperature and stirring speed improved the chlorine removal speed. Moreover, reducing the particle size and adding 0.2% nonionic surfactant Triton X-100 reduced the surface energy and accelerated surface chemical reaction, which were also beneficial for removing chlorine from sintering dust. In addition, the SEM-EDS examination inferred that the existence of laurionite (PbOHCl) limited the chlorine dissolution rate to less than 97%, while beneficiation or hydrometallurgy treatment was needed to further remove chlorine.

Fluoride Leaching of Titanium from Ti-Bearing Electric Furnace Slag in [NH4+]-[F−] Solution

The effects of F− concentration, leaching temperature, and time on the Ti leaching from Ti-bearing electric furnace slag (TEFS) by [NH4+]-[F−] solution leaching process was investigated to reveal the leaching mechanism and kinetics of titanium. The results indicated that the Ti leaching rate obviously increased with the increase of leaching temperature and F− concentration. The kinetic equation of Ti leaching was obtained, and the activation energy was 52.30 kJ/mol. The fitting results of kinetic equations and calculated values of activation energy both indicated that the leaching rate of TEFS was controlled by surface chemical reaction. The semi-empirical kinetics equation was consistent with the real experimental results, with a correlation coefficient (R2) of 0.996. The Ti leaching rate reached 92.83% after leaching at 90 °C for 20 min with F− concentration of 14 mol/L and [NH4+]/[F−] ratio of 0.4. The leaching rates of Si, Fe, V, Mn, and Cr were 94.03%, 7.24%, 5.36%, 4.54%, and 1.73%, respectively. The Ca, Mg, and Al elements were converted to (NH4)3AlF6 and CaMg2Al2F12 in the residue, which can transform into stable oxides and fluorides after pyro-hydrolyzing and calcinating.

Leaching Kinetics of Selenium, Tellurium and Silver from Copper Anode Slime by Sulfuric Acid Leaching in the Presence of Manganese(IV) Oxide and Graphite

Sulfuric acid leaching of copper anode slime (CAS) in the presence of manganese(IV) oxide (MnO2) and graphite was investigated for Se, Te and Ag recovery. The study reveals that the leaching of Se, Te and Ag was facilitated by the galvanic interaction with MnO2, and graphite played the role of a catalyst. The leaching process could yield 81.9% Se, 90.8% Te, and 80.7% Ag leaching efficiency when the conditions were maintained as 500 rpm, 2.0 M H2SO4, 0.8/0.8/1 MnO2/graphite/CAS, and 90 °C temperature. The kinetic study showed that Se leaching followed the surface chemical reaction at all the tested temperature range (25–90 °C) with the activation energy of 27.7 kJ/mol. Te and Ag leaching at temperature 25–50 °C followed the mixed and surface chemical reaction models, respectively, and changed to fit the diffusion and mixed control models, respectively, in the temperature range 60–90 °C with the corresponding activation energy of 17.8 and 12.2 kJ/mol.

Electron-Interfered Field-Effect Transistors as Sensor Platform for Detecting a Delicate Surface Chemical Reaction

We introduce a new electron-interfered field-effect transistor (EIFET) device using a modified organic charge-modulated FET (OCMFET) structure and demonstrate its ability to detect the surface chemical reaction degree (or rate)....

Three-dimensional graphene nanoribbons as a framework for molecular assembly and local probe chemistry

Recent advances in state-of-the-art probe microscopy allow us to conduct single molecular chemistry via tip-induced reactions and direct imaging of the inner structure of the products. Here, we synthesize three-dimensional graphene nanoribbons by on-surface chemical reaction and take advantage of tip-induced assembly to demonstrate their capability as a playground for local probe chemistry. We show that the radical caused by tip-induced debromination can be reversibly terminated by either a bromine atom or a fullerene molecule. The experimental results combined with theoretical calculations pave the way for sequential reactions, particularly addition reactions, by a local probe at the single-molecule level decoupled from the surface.

A Novel Technology for Recovery and Separation of Vanadium and Chromium from Vanadium-Chromium Reducing Residue

This paper was to develop an efficient process for efficient recovery and separation of vanadium and chromium. The vanadium-chromium reducing residue was conducted by oxidation acidic leaching with MnO2, followed by selective adsorption of vanadium and precipitation of chromium, respectively. The results showed that 97.93% vanadium was leached out and then adsorbed by melamine at pH 1.8 at 90 °C for 60 min. Almost all chromium was leached out and efficiently recovered as Cr2O3. The leaching process was mainly controlled by surface chemical reaction, and its kinetic behaviors fitted well with the shrink core model. The apparent activation energy for vanadium and chromium leaching out wascalculated as 19.93 kJ·mol−1 and 21.26 kJ·mol−1, respectively.