In this work the preparation of alumina from kaolinite by leaching with hydrochloric acid is studied. Crude kaolin was calcined at 850?C and then leached with 6 M hydrochloric acid at 90?C. Aluminum ...hydroxide was precipitated by adding 6 M HCl solution to the leaching water. Finally, the precipitated aluminum hydroxide was heated at 1100?C and converted to aluminum oxide. The materials were identified by XRF, XRD and SEM-EDX techniques. The percentage of alumina recovery was determined at different kaolin particle sizes (?200 to ?400 standard Tyler sieve), different times (1, 2, 3 and 4 h), different leaching temperatures (80, 90, 100 and 104?C) and different concentrations of hydrochloric acid (20, 25, 30 and 37%). The phase changes of alumina were also investigated at two calcination temperatures (1100 and 1200?C). The purity of aluminum oxide obtained by this method is about 97% and the percentage of recovery is about 98%. It was observed that the kaolin granulation with dimensions smaller than 75 ?m had no significant effect on the percentage of alumina recovery. It was also found that the percentage of alumina recovery increased with increasing leaching temperature.
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Sulfuric acid dissolution of rare earth elements from bastnasite ore was studied after reductive smelting with carbon as a reducing agent at 1600°C. The two-step strategy: 1.carbothermic reduction, ...and 2.dissolution with sulfuric acid at 70°C was applied under atmospheric pressure aiming at an increased selective extraction of rare earth elements from slag containing rare earth elements. / При исследовании процесса выщелачивания редкоземельных рудных пород, содержащих фторкарбонат, применялся метод восстановительного плавления в углеродной среде при температуре 1600° C, состоящий из двух этапов: 1) карботермическое восстановление и 2) растворение в серной кислоте при атмосферном давлении, с целью увеличения селективного извлечения редкоземельных элементов из шлака, содержащего редкоземельные элементы. / Rastvaranje elemenata retkih zemalja iz bastnezitne rude (rude koja sadrži fluorokarbonatni mineral) proučavano je posle reduktivnog topljenja ugljenikom na 1600°C. Strategija u dva koraka: 1. redukcija ugljenikom, i 2. rastvaranje pomoću sumporne kiseline primenjeno je na atmosferskom pritisku sa ciljem da se poveća ekstrakcija elemenata retkih zemalja iz šljake koja sadrži elemente retkih zemalja.
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This article deals with hydrometallurgical treatment with the subsequent precipitation of zinc from hazardous waste Sal- Ammoniac Skimming produced in wet hot-dip galvanizing process. Chemical ...analysis showed that skimming contained 46.64% Zn. X-ray diffraction analysis identified the Zn(OH)Cl phase (96.36%) and NH4Cl (3.64%) in Sal-Ammoniac Skimming. The skimming was first subjected to leaching in order to extract zinc into the solution containing HCl, followed by precipitation of the zinc. The experiments were performed in a medium of HCl at concentrations of 0.25, 0.5, 1 and 2M. Complete dissolution of zinc was achieved in 0.5M HCl solution, at 40?C, L:S=20, max. 30 min. The apparent activation energy of leaching reaction by hydrochloric acid solution was Ea=5.543 kJ mol-1. Zn precipitation was carried out using Na2CO3 and NaOH. Zinc oxide with a purity of about 99% was obtained directly from the solution of 6M NaOH at a temperature of 60?C ? 80?Cat pH 8.8.
nema
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