Leaching and solvent extraction purification of zinc from Mehdiabad complex oxide ore

An integrated hydrometallurgical process was used for the zinc leaching and purification from a zinc ore containing 9.75 wt% zinc. The zinc minerals in the ore were hemimorphite, willemite, and calcophanite. Main gangue minerals were quartz, goethite, hematite, and calcite. Central composite design (CCD) method was used to design leaching experiments and the optimum conditions were found as follows: 30% of solid fraction, 22.05% sulphuric acid concentration, and the leaching temperature of 45 °C. The PLS containing 35.07 g/L zinc, 3.16 g/L iron, and 4.58 g/L manganese impurities was produced. A special purification process including Fe precipitation and Zn solvent extraction was implemented. The results showed that after precipitation of iron, Zn extraction of 88.5% was obtained with the 2 stages extraction system composed of 30 vol% D2EHPA as extractant. The overall Zn recovery from the ore was 71.44%. Therefore, an appropriate solution containing 16.6 g/L Zn, 0.05 g/L Fe, and 0.11 g/L Mn was prepared for the electro-winning unit without using the roasting and calcination steps (conventional method), which result in environmental pollution.

Sources and sinks driving sulphuric acid concentrations in contrasting environments: implications on proxy calculations

Sulphuric acid has been shown to be a key driver for new particle formation and subsequent growth in various environments mainly due to its low volatility. However, direct measurements of gas-phase sulphuric acid are oftentimes not available, and the current sulphuric acid proxies cannot predict for example its nighttime concentrations or result in significant discrepancies with measured values. Here, we define the sources and sinks of sulphuric acid in different environments and derive a new physical proxy for sulphuric acid to be utilized in locations and during periods when it is not measured. We used H2SO4 measurements from four different locations: Hyytiälä, Finland; Agia Marina, Cyprus; Budapest, Hungary; and Beijing, China, representing semi-pristine boreal forest, rural environment in the Mediterranean area, urban environment and heavily polluted megacity, respectively. The new proxy takes into account the formation of sulphuric acid from SO2 via OH oxidation and other oxidation pathways, specifically that via stabilized Criegee Intermediates. The sulphuric acid sinks included in the proxy are its condensation sink (CS) and atmospheric clustering starting from H2SO4 dimer formation. Indeed, we found that the observed sulphuric acid concentration can be explained by the proposed sources and sinks with similar coefficients in the four contrasting environments where we have tested it. Thus, the new proxy is a more flexible and an important improvement of previous proxies. Following the recommendations in the manuscript, a proxy for a specific location can be derived.

REDUCTIVE LEACHING OF LOW GRADE MANGANESE ORE (LGMO) USING GLUCOSE IN SULPHURIC ACID: OPTIMIZATION CONDITION USING RESPONSE SURFACE METHODOLOGY

Manganese (Mn) is an important metal in producing a good quality steel, that the total Mn consumption in this industry reaches 85 to 90%. Despite of this huge demand, Mn faces a shortage supply due to depletion of high grade Mn ore. As an alternative, low grade manganese ore (LGMO) can be utilized to fulfill the industry demand. The aim of this work is to determine the optimum condition of the reductive leaching process of LGMO using Response Surface Methodology (RSM). The design of experiment (DOE) was made using RSM by Central Composite Design (CCD) with 22 and 3 central points. In this work, the effect of variables such as sulphuric acid concentration (X1) and weight of glucose (X2) were examined. The experimental data obtained from Analysis of Variance (ANOVA) were analyzed. Subsequently, the most significant variable was identified and fitted into a quadratic model. It is found that the interaction between sulphuric acid concentration and amount of glucose (X1X2) is the most important factor in manganese (Mn) extraction. The optimum leaching condition is obtained at 2.5 M sulphuric acid concentration and 2 g weight of glucose at 60 minutes leaching time. Within this experimental condition, a high level of Mn extraction ratio at 88.97% is achieved.

Total sulphate vs. sulphuric acid monomer in nucleation studies

Sulphuric acid is known to be a key component for atmospheric nucleation. Precise determination of sulphuric acid concentration is crucial factor for prediction of nucleation rates and subsequent growth. In our study, we have noticed a substantial discrepancy between sulphuric acid monomer and total sulphate concentrations measured from the same source of sulphuric acid vapour. The discrepancy of about one to two orders of magnitude was found with similar formation rates. To investigate this discrepancy and its effect on nucleation, a method of thermally controlled saturator filled with pure sulphuric acid (97% wt.) for production of sulphuric acid vapour is introduced and tested. Sulphuric acid-water nucleation experiment was done using a laminar flow tube. Two independent methods of mass spectrometry and online ion chromatography were used for detecting sulphuric acid concentrations. The results are compared to our previous results, where a method of furnace was used to produce sulphuric acid vapour (Brus et al., 2010, 2011). Measured sulphuric acid concentrations are compared to theoretical prediction calculated using vapour pressure and a mixing law. The calculated prediction of sulphuric acid concentrations agrees very well with the measured values when total sulphate is considered. Sulphuric acid monomer concentration was found to be about two orders of magnitude lower than the prediction, but with similar temperature dependency as the prediction and the results obtained with ion chromatograph method. Formation rates agree well when compared to our previous results with both sulphuric acid detection and sulphuric acid production methods separately.

Effect of ions on the measurement of sulphuric acid in the CLOUD experiment at CERN

Ternary aerosol nucleation experiments were conducted in the CLOUD chamber at CERN in order to investigate the influence of ions on new particle formation. Neutral and ion-induced nucleation experiments, i.e., with and without the presence of ions, were carried out under precisely controlled conditions. The sulphuric acid concentration was measured with a Chemical Ionization Mass Spectrometer (CIMS) during the new particle formation experiments. The added ternary trace gases were ammonia (NH3), dimethylamine (DMA, C2H7N) or oxidised products of pinanediol (PD, C10H18O2). When pinanediol was introduced into the chamber, an increase in the mass spectrometric signal used to determine the sulphuric acid concentration (m/z 97, i.e., HSO4−) was observed due to ions from the CLOUD chamber. The enhancement was only observed during ion-induced nucleation measurements by using either galactic cosmic rays (GCR) or the proton synchrotron (PS) pion beam for the ion generation, respectively. The ion effect typically involved an increase in the apparent sulphuric acid concentration by a factor of ~2 to 3 and was qualitatively verified by the ion measurements by an Atmospheric Pressure interface-Time Of Flight (APi-TOF) mass spectrometer. By applying a high voltage (HV) clearing field inside the CLOUD chamber the ion effect on the CIMS measurement was completely eliminated since, under these conditions, small ions are swept from the chamber in about one second. In order to exclude the ion effect and to provide corrected sulphuric acid concentrations during the GCR and PS beam nucleation experiments, a parameterisation was derived that utilizes the trace gas concentrations and the UV light intensity as input parameters. Atmospheric sulphuric acid measurements with a CIMS showed an insignificant ion effect.

Optimization of Chemical Environment Condition towards Corrosion Rate of Sulfuric Acid Resistant Alloy Metal (Saramet) Using Response Surface Methodology

This study investigates the variation of sulphuric acid concentration, temperature, and time towards the corrosion rate of saramet using response surfacemethod. Method used in this study istrue experimental research.Sarametis material which is included into type of austenitic stainless steel which contains high amount of silicon. Starting at these past 2 years, the material has been widely used.This research usedweight loss method.It has been found that minimum corrosion rate is achieved at concentration combination of 89.49% in 3.682 hoursandat temperature of 106,8 °C. From the variation combination, it is seen that the low concentration will decrease ion mobility corrossive ion from saramet.The long period of exposure supports the forming of passive layer which prevent the corrosive ions gets into the steel surface. As a result, corrosion rate decreases. At high temperature, steel which has high silicon content will be stable in terms of its atomic bound which therefore makes it posses high corrosion resistance.