Book review: Rheology of emulsions - electrohydrodynamics principles by Aleksandar M. Spasic

This interesting book covers both, research and development (R&D) and fundamental research of the selected finely dispersed systems, that is emulsions and double emulsions. In general, an interdisciplinary and/or multidisciplinary approach has been applied to the phenomena occurring at developed liquid-liquid interfaces during their formation, duration, and destruction processes

Leaching mechanism of polymetallic pb-zn-cu concentrates using sulphuric acid in the presence of selected oxidant

Iscrpljivanje bogatih i pojava nestandardnih rudnih rezervi sulfidnih mineralnih sirovina nalaže potrebu za pronalaženje odgovarajućih mogućnosti prerade do danas nedovoljno iskorišćenih resursa i njihovu eksploataciju. Jedan deo ovih ruda predstavljaju polimetalične rude i kolektivni koncentrati iz kojih često nije moguće konvencionalnim postupcima prerade valorizovati obojene metale sa zadovoljavajućim stepenom iskoričćenja. Izučavanje postupaka za valorizovanje obojenih metala iz ovakvih sirovina vezano je za poznavanje oblika pojavljivanja obojenih metala u sulfidnim sirovinama, strukturno-morfoloških osobina minerala nosioca i fizičko-hemijskih mogućnosti za procesno tretiranje u cilju dobijanja metala uz zadovoljavajuće iskorišćenje. Nakon detaljnog uvida u procesne mogućnosti prerade ovakvih ruda i koncentrata, za analizu mogućnosti primene odabran je postupak luženja sulfidnih koncentrata rastvorom sumporne kiseline u prisustvu oksidansa pri normalnom pritisku. Za ispitivanja su korišćena dva polimetalična koncentrata: u prvom je bakar bio zastupljeniji u odnosu na cink i olovo (halkopiritni koncentrat), dok su u drugom sva tri minerala bila ravnomerno zastupljena (polimetalični koncentrat). Na osnovu literaturnih podataka izvršen je izbor oksidanasa i tokom eksperimentalnih istraživanja dokazano da je primena natrijum(I)-nitrata i vodonik-peroksida opravdana i adekvatna kod luženja polimetaličnih koncentrata sa različitim sadržajem halkopirita u rastvorima sumporne kiseline pri standardnom pritisku. Termodinamička analiza procesa luženja je obuhvatila proračun promene Gibsove energije hemijskih reakcija luženja i konstukciju E-pH dijagrama stabilnosti bakra, cinka, olova i železa u ispitivanim sistemima. Ispitivanjem uticaja kinetičkih parametara procesa (temperature, vreme, granulometrijski sastav, brzina mešanja, koncentracija H2SO4, koncentracija NaNO3 (H2O2)) halkopiritnog koncentrata na izluženje bakra određeni su optimalni parametri procesa luženja u sistemima H2SO4-NaNO3-H2O i H2SO4-H2O2-H2O. Dobijeni rezultati su iskoričćeni za određivanje kinetičkih zakonitosti, energija aktivacije i mehanizma odvijanja procesa. Ispitivanje uticaja temperature i vremena luženja polimetaličnog koncentrata na izluženje bakra, cinka i železa, poslužilo je za analizu uticaja sastava polimetaličnih sirovina na luženje bakra pri istim uslovima i ocenu stabilnosti sulfidnih minerala prisutnih u koncentratu. Proučavanjem mikrostrukture, strukturno-teksturnih i morfoloških karakteristika sulfidnih koncentrata i čvrstih ostataka nakon luženja doneti su pouzdani zaključci o uslovima i mogućnostima luženja bakra, cinka i železa, osnovnim hemijskim reakcijama i mehanizmu procesa luženja.Depletion of reach ore deposits of sulphide mineral raw materials as well as occurrence of nonstandard ore reserves indicated the necessity to investigate the treatment possibilities of resources that were inadequately exploited up-to –date. Polymetallic ores and bulk concentrates out of which is hard or impossible to valorize non-ferrous metals with satisfying recovery degree, using conventional treatment procedures, present a part of such ores. Non-ferrous metals valorization procedures investigation is associated with knowledge about the form of appearance of non-ferrous metals in sulphide raw materials, structural and morphological properties of the bearing mineral and physico-chemical possibilities of treatment process for the sake of metal obtaining with satisfying recovery degree. For analysis of application possibilities, after detailed insight into treatment process possibilities of such ores and ore concentrates, the leaching procedure of sulphide concentrates with sulphuric acid solution in the presence of oxidant, at standard pressure, was chosen. Two polymetallic concentrates are used for investigations: the first with higher copper content comparing to zinc and lead content chalcopyrite concentrate), and the second with even content of each of the three minerals (polymetallic concentrate). The oxidant was chosen based on literature data, and during experimental investigations it is proven that the application of sodium (I)-nitrate and hydrogen- peroxide was reasonable and adequate for polymetallic concentrates with different chalcopyrite content leaching in the slphuric acid solutions, at standard pressure. Thermodynamic analysis of leaching process encompassed the calculation of the Gibbs energy changes for chemical reactions of leaching, as well as E-pH diagrams construction for stability of copper, zinc, lead and iron at investigated systems. Optimal parameters of leaching process in the following systems: H2SO4-NaNO3-H2O i H2SO4-H2O2-H2O, are determined through examination the kinetic parameters (temperature, time, grain size distribution, agitation speed, sulphuric acid concentration, sodium (I)-nitrate and/or hydrogen-peroxide concentration) influence on the copper recovery degree during chalcopyrite concentrate leaching. Obtained results are used for determination the kinetic principles, activation energies and process mechanisms. Investigation the temperature and leaching time of polymetallic concentrate influence on copper, zinc and iron recovery degree, was used for analysis of polymetallic raw materials composition influence on the copper leaching at the same conditions, and for estimation the stability of the sulphide minerals assembled in concentrate. Microstructure, structure-textural and morphological characteristics examination of sulphide concentrates and leaching solid residues, contributed the reliable conclusions providing, concerning the conditions and possibilities of copper, zinc and iron leaching, fundamental chemical reactions and leaching process mechanism

Review of the past, present, and future of the hydrometallurgical production of nickel and cobalt from lateritic ores

Laterite ores are becoming the most important global source of nickel and cobalt. Pyrometallurgical processing of the laterites is still a dominant technology, but the share of nickel and cobalt produced by the application of various hydrometallurgical technologies is increasing. Hydrometallurgy is a less energy-demanding process, resulting in lower operational costs and environmental impacts. This review covers past technologies for hydrometallurgical processing of nickel and cobalt (Caron), current technologies (high-pressure acid leaching, atmospheric leaching, heap leaching), developing technologies (Direct nickel, Neomet) as well as prospective biotechnologies (Ferredox process)

Chalcopyrite leaching in acid media: a review

In the modern practice of copper production, more and more attention is paid to the possibility of treating low-percentage sulfide ores that cannot be treated with conventional procedures (crushing, grinding, flotation). In addition to this, the processes of obtaining copper from complex sulfide concentrates, which cannot undergo pyrometallurgical processing, are increasingly being investigated. Extraction of copper from such raw materials is in most cases achieved by applying leaching procedures. Since chalcopyrite (CuFeS2) is by far the most abundant copper sulfide mineral, a large portion of the research is focused on studying the behavior of chalcopyrite in the leaching process, because processes of copper extraction from increasingly poor raw materials may be created using results of these studies. In addition, the main objective of this research is examining the kinetics and mechanism of chalcopyrite oxidation under the influence of various oxidants (O2, Fe3 +, H2O2, chlorate ions, etc.) and at the same time obtaining data necessary for the development of copper production process that could satisfy increasingly stringent technological, economic and environmental criteria. The paper presents the existing knowledge of the chalcopyrite leaching procedure and phenomena that accompany chalcopyrite oxidation in acidic sulfate and chloride solutions

Reaction mechanism and kinetics of sulfide copper concentrate oxidation at elevated temperatures

Sulfide copper concentrate from domestic ore deposit (Bor, Serbia) was subjected to oxidation in the air atmosphere due to a better understanding of reaction mechanism and oxidation of various sulfides present in the copper concentrate at elevated temperatures. Results of the initial sample characterization showed that concentrate is chalcopyrite–enargite-tennantite type, with an increased arsenic content. Characterization of the oxidation products showed the presence of sulfates, oxysulfates, and oxides. Based on predominance area diagrams for Me-S-O systems (Me = Cu, Fe, As) combined with thermal analysis results, the reaction mechanism of the oxidation process was proposed. The reactions which occur in the temperature range 25 – 1000 °C indicate that sulfides are unstable in the oxidative conditions. Sulfides from the initial sample decomposed into binary copper and iron sulfides and volatile arsenic oxides at lower temperatures. Further heating led to oxidation of sulfides into iron oxides and copper sulfates and oxysulfates. At higher temperatures sulfates and oxysulfates decomposed into oxides. Kinetic analysis of the oxidation process was done using Ozawa’s method in the non-isothermal conditions. The values for activation energies showed that the reactions are chemically controlled and the temperature is the most influential parameter on the reaction rates

Kinetics of barite reduction from refractory barite-sulphide ore

Refractory sulphide-barite ore was reduced with carbon in order to release lead, zinc, and copper sulphide from barite-pyrite base. Mineralogical investigations showed that due to the complex structural-textural relationships of lead, copper and zinc minerals with gangue minerals, it is not possible to enrich the ore using the conventional methods of mineral processing. The influence of temperature and time was studied to optimize the conditions, and to determine the kinetics of the barite reduction. The maximum removal of barite from ore was 96.7% at 900oC after 180 min. Chemically controlled kinetic model showed the best compliance with the experimental data. An activation energy of 142 kJ/mol was found

Deashing and desulfurization of subbituminous coal from the East field (Bogovina Basin, Serbia) - insights from chemical leaching

The study is focused on the determination of the most effective chemical leaching process for the simultaneous demineralization/deashing and desulfurization of subbituminous coal from the Bogovina Basin. Coal was treated for 30 min, at different temperatures, using variable concentrations of hydrochloric, nitric, acetic and citric acids; hydrogen peroxide, mixture of hydrogen peroxide and nitric acid (pH 2), as well as by the stepwise leaching process (nitric acid + mixture of hydrogen peroxide and nitric acid, pH 2). The changes in mineral composition, caused by the chemical leaching, are followed using X-ray diffraction, whereas alterations of coal organic matter are tracked by Fourier-transform infrared spectroscopy and the content of fixed carbon. Inorganic acid leaching, regardless of the temperature and acid concentration, enabled the successful deashing of coal, whereas the percent of desulfurization was insufficient. The organic acid leaching was not satisfactory for both, deashing and desulfurization. Leaching by H2O2 and H2O2/HNO3 mixture (pH 2) resulted in moderate desulfurization, but the ash reduction was low. The most suitable method for the simultaneous effective ash (78 wt.%) and the sulfur (66 wt. %) removal from Bogovina coal is the two-step leaching, combining 10 vol. % HNO3 and mixture of 35 vol. % H2O2/10 vol. % HNO3 of pH 2 at 60°C

Investigation of the optimal technology for copper leaching from old flotation tailings of the copper mine bor (Serbia)

This work aimed to investigate optimal leaching technology for copper extraction from old flotation tailings of the Copper Mine Bor. The leaching degree of copper after leaching with sulphuric acid at 80 °C was 50%, the maximal leaching degree was achieved after 30 minutes. Then, old flotation tailings were leached with adapted moderately thermophilic acidophilic bacteria in a bioreactor at 40 °C. Maximal leaching degree of 84% was achieved after nine days of the experiment. The third leaching experiment was conducted with biogenic lixiviant obtained by bacterial oxidation of the ferrous iron (concentration of Fe3+ 1300 mgL-1, pH 2.14). Biogenic lixiviant with ferric sulphate was then used in the leaching experiment at 80 °C. Maximal leaching degree was 78%, and it was achieved after five minutes. Results of the leaching experiments show that the most efficient technology for copper recovery from the old flotation tailings of the Copper Mine Bor was leaching with biogenic lixiviant

Ni-Pd-Al2O3 catalyst supported on reticulated ceramic foam for dry methane reforming

In the present study, Ni-Pd/Al2O3 catalyst supported on α-Al2O3 based foam was prepared and evaluated in the dry methane reforming process. Corresponding metal chlorides were deposited to the foam surface by impregnation of the foam with ultrasonically aerosolized salt solutions at 473 K and drying at that temperature. Calcination step was excluded and the catalyst was reduced at very low temperature - 533 K. The reforming experiment lasted for 3 h, with standing time of 1 h at the following temperatures: 873, 973 and 1023 K. Conclusions on selectivity, catalytic activity and stability were reached on the basis of CO and H2 yields

Predicting Low-Modulus Biocompatible Titanium Alloys Using Machine Learning

Titanium alloys have been present for decades as the main components for the production of various orthopedic and dental elements. However, modern times require titanium alloys with a low Young’s modulus, and without the presence of cytotoxic alloying elements. Machine learning was used with aim to analyze biocompatible titanium alloys and predict the composition of Ti alloys with a low Young’s modulus. A database was created using experimental data for alloy composition, Young’s modulus, and mechanical and thermal properties of biocompatible titanium alloys. The Extra Tree Regression model was built to predict the Young’s modulus of titanium alloys. By processing data of 246 alloys, the specific heat was discovered to be the most influential parameter that contributes to the lowering of the Young’s modulus of titanium alloys. Further, the Monte Carlo method was used to predict the composition of future alloys with the desired properties. Simulation results of ten million samples, with predefined conditions for obtaining titanium alloys with a Young’s modulus lower than 70 GPa, show that it is possible to obtain several multicomponent alloys, consisting of five main elements: titanium, zirconium, tin, manganese and niobium