Wyniki wyszukiwania - BazTech

1

Effect of particle size on chalcocite dissolution kinetics in column leaching under controlled Eh and its implications

Phyo Htet Aung, Jia Yan, Tan Qiaoyi, Zhao Shenggui, Liang Xinxing, Ruan Renman, Niu Xiaopeng

Physicochemical Problems of Mineral Processing

|

2020

|

Vol. 56, iss. 4

676--692

EN

Natural high grade chalcocite samples were leached in column under controlled Eh, constant temperature and solution pH to investigate the effect of particle size on dissolution kinetics. Moreover, low grade ores of larger size fractions were leached in column using raffinate from the industrial heap as an irrigation solution to simulate the real heap conditions. The leaching rate of large particle sizes (31-200 mm) were very slow without inflection point which are normally present in the leaching of small particle sizes (0.054-31 mm). The effect of particle size was more remarkable in the dissolution of large particles than that of small particles during the first stage (<45% dissolution). However, the dissolution rate of the second stages (>45% dissolution) were not noticeably affected by the particle size. Results of kinetics analysis of leaching of small particles using shrinking core model indicated that the first stage was controlled by fluid diffusion and confirmed by the low activation energies (20.98 kJ/mol). The kinetics of second stage was controlled by chemical reaction and product layer diffusion and the later control became prominent with increasing particle size. Similarly, product layer diffusion was the rate-controlling step for the first and second stages of leaching of large particles. X-ray CT and SEMEDS studies observed the increasing numbers of cracks and porosity and the formation of sulfur layer on the surface of the residue samples. The findings in this study provided some useful implications to optimize the heap performance and understand the leaching behavior of large particles.

2

A comparison of uranium recovery from low-grade ore by bioleaching and acid leaching

Szolucha M. M., Chmielewski A. G.

Physicochemical Problems of Mineral Processing

|

2017

|

Vol. 53, iss. 1

136--149

EN

The objective of this work was to compare the bioleaching with the acid leaching of uranium under similar process conditions within 65 days. The low-grade uranium ore used in the experiments was collected from Radoniow’s ‘small’ dump, Poland. Bioleaching and acid leaching studies were carried out in identical columns. The isolated bacterial consortium from the Radoniow’s mine was used for the bioleaching process. A solution of sulphuric acid and H2O2 as oxidizing agent was used for the acid leaching. The extraction of uranium under acid leaching conditions reached maximum of 64±13 % w/w after 31 days. The bioleaching of uranium achieved a maximum extraction of 75±15 % w/w after 55 days. In this study an attempt was made to demonstrate the relationship between the shrinking-core model and the experimental data by plotting the fractional conversion of uranium against time.

3

A study on heavy metals mobility from zinc plant residues in Iran

Moradkhani D., Eskandari S., Sedaghat B., Najafabadi M. R.

Physicochemical Problems of Mineral Processing

|

2013

|

Vol. 49, iss. 2

567--574

EN

The transport of heavy metals from mining disposal site to groundwater and surface water is one of the most serious environmental problems in the world. The transport of heavy metals such as Zn, Cd and Mn from leaching filter cake in RECo, Zanjan, Iran was examined by using column leaching. Parameters studied included: flow rate, pH of input solution and leaching time. In this study, the maximum dissolution percents of Zn, Cd and Mn in input solution pH of 5 were 45.50 %, 53.97% and 19.94%, respectively. To statistically analysis the experimental results, SPSS14 software was employed. The results of SPSS 14 indicated that for the Zn, Cd and Mn dissolution, time and flow rate were found respectively, the effective parameters for the pollution in zinc leach residues.