862
H. Wang et al.
leaching slag is lower than that in the raw materials, which is due to the decrease of
sulfide after leaching. Meanwhile, the elemental sulfur and Pb-jarosite are observed
in the slag sample after leaching. The appearance of elemental sulphur is due to
that the sulphide is leached in the oxygen enriched and pressurized system. The Pbjarosite phase comes from the precipitate formed by the hydrolyzation of iron ions
produced by the leaching process.
Other Recent Relevant Experimental Studies
In the process of pressure leaching, sulfur is recycled in the form of elemental sulfur,
which avoids the problem of SO 2 pollution. However, this process has the disadvantages of large equipment investment and high operational safety requirements.
The oxygen enriched atmospheric direct leaching technology can avoid the aforementioned disadvantages. The Outokumpu smelter in Finland realized the oxygen
enriched atmospheric pressure leaching by increasing the leaching pressure through
increasing the pulp height, which has been gradually industrialized [6, 7]. Although
the oxygen enriched atmospheric pressure direct leaching has certain advantages,
the leaching rate is slow and the process is time-consuming. In order to solve this
problem, Xu et al. [8] used zinc concentrate as the research object and compared
the leaching kinetics of zinc concentrate by combining atmospheric leaching and
pressure leaching. It is pointed out that in the oxygen enriched atmospheric pressure
leaching of zinc sulfide concentrate, the zinc leaching process is controlled by the
interface chemical reaction both in the upper and the bottom of the leaching tank,
and the leaching kinetic equation follows the unreacted shrinkage nucleus model. For
the zinc leaching at the bottom of the leaching tank, the leaching rate is significantly
enhanced due to the large pulp pressure at the bottom of the tank. They also found
that the influence of temperature on the leaching rate is significantly greater than that
of the slurry pressure.
Zhu et al. [9] conducted a series of studies on the dissolution behavior of oxygen
and pointed out that moderately increasing the temperature in the range of 90–
160 °C contributes to the increase of oxygen dissolution rate and the dissolution and
transportation of oxygen in aqueous solution. The extension of the oxygen pipe is
beneficial to the oxygen dissolution rate. In addition, multiple air intake modes are
better than the single air intake mode.
Gu et al. [10] from Northeast University used synthetic sphalerite as the research
object, and carried out kinetic studies. Their study demonstrated that the leaching
process of sphalerite is controlled by surface chemical reaction, of which the kinetics
follows the “unreacted shrinkage nuclear model”.
Xu et al. [11] studied the behaviors of zinc, sulfur, and iron during the low temperature pressure leaching of iron sphalerite. It was pointed out that the main chemical
reaction in the early stage of leaching is the acid dissolution of iron sphalerite. In
the later stage of leaching, dissolution of iron and the hydrolysis and precipitation
H. Wang et al.
leaching slag is lower than that in the raw materials, which is due to the decrease of
sulfide after leaching. Meanwhile, the elemental sulfur and Pb-jarosite are observed
in the slag sample after leaching. The appearance of elemental sulphur is due to
that the sulphide is leached in the oxygen enriched and pressurized system. The Pbjarosite phase comes from the precipitate formed by the hydrolyzation of iron ions
produced by the leaching process.
Other Recent Relevant Experimental Studies
In the process of pressure leaching, sulfur is recycled in the form of elemental sulfur,
which avoids the problem of SO 2 pollution. However, this process has the disadvantages of large equipment investment and high operational safety requirements.
The oxygen enriched atmospheric direct leaching technology can avoid the aforementioned disadvantages. The Outokumpu smelter in Finland realized the oxygen
enriched atmospheric pressure leaching by increasing the leaching pressure through
increasing the pulp height, which has been gradually industrialized [6, 7]. Although
the oxygen enriched atmospheric pressure direct leaching has certain advantages,
the leaching rate is slow and the process is time-consuming. In order to solve this
problem, Xu et al. [8] used zinc concentrate as the research object and compared
the leaching kinetics of zinc concentrate by combining atmospheric leaching and
pressure leaching. It is pointed out that in the oxygen enriched atmospheric pressure
leaching of zinc sulfide concentrate, the zinc leaching process is controlled by the
interface chemical reaction both in the upper and the bottom of the leaching tank,
and the leaching kinetic equation follows the unreacted shrinkage nucleus model. For
the zinc leaching at the bottom of the leaching tank, the leaching rate is significantly
enhanced due to the large pulp pressure at the bottom of the tank. They also found
that the influence of temperature on the leaching rate is significantly greater than that
of the slurry pressure.
Zhu et al. [9] conducted a series of studies on the dissolution behavior of oxygen
and pointed out that moderately increasing the temperature in the range of 90–
160 °C contributes to the increase of oxygen dissolution rate and the dissolution and
transportation of oxygen in aqueous solution. The extension of the oxygen pipe is
beneficial to the oxygen dissolution rate. In addition, multiple air intake modes are
better than the single air intake mode.
Gu et al. [10] from Northeast University used synthetic sphalerite as the research
object, and carried out kinetic studies. Their study demonstrated that the leaching
process of sphalerite is controlled by surface chemical reaction, of which the kinetics
follows the “unreacted shrinkage nuclear model”.
Xu et al. [11] studied the behaviors of zinc, sulfur, and iron during the low temperature pressure leaching of iron sphalerite. It was pointed out that the main chemical
reaction in the early stage of leaching is the acid dissolution of iron sphalerite. In
the later stage of leaching, dissolution of iron and the hydrolysis and precipitation