A Critical Review on Generation, Characteristics …
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balance with demand. In 2019, the global refined zinc production is forecast to reach
14.95 million tons. And the predicted zinc demand is up to 15.12 million tons [4, 5].
Zinc production process generally can be divided into pyrometallurgical and
hydrometallurgical process. 90% of global zinc is produced by hydrometallurgical process. And 40% of global zinc is produced by high-acid leaching, oxygen
pressure leaching, and oxygen atmospheric leaching [7]. The zinc production lines
using the pyrometallurgical process are mainly in China, which include zinc smelting by horizontal retorting, vertical retorting, electric furnace, and imperial smelting
furnace [8]. Zinc hydrometallurgical process can be divided into two categories. The
traditional hydrometallurgical process consists of the roasting of zinc concentrate,
extraction, purification, and electrowinning. And the other one is composed by the
direct extraction of zinc concentrate, purification, and electrowinning [9].
Zinc Smelting Slag and Zinc Leach Residue
Zinc smelting slag is generated by the zinc pyrometallurgical process. In general,
total contents of zinc and lead of the zinc smelting slag are about 5–15%, while
the contents of rare and noble metals are very low [10]. Therefore, it is not economic for the recovery of valuable metals from the zinc smelting slag by the traditional hydrometallurgical processes (including acid curing and alkali leaching) and
pyrometallurgical processes. Moreover, if the zinc smelting slag is treated using a
traditional hydrometallurgical process, the leaching agent (acid or alkali) will be left
in the residues, and the gangue components in the slag are turned into a secondary
slag without utilization, which results in a secondary pollution [11–13].
Zinc leach residue, generated in the zinc hydrometallurgical process, belongs to
hazardous solid waste [14]. The composition of the leach residue is very complex,
especially the high-temperature and high-acid leach residue, which contains zinc
and other valuable metals (such as lead, copper, indium, and silver) [15, 16]. Using
the traditional pyrometallurgical or hydrometallurgical process, the treatment cost
of zinc leach residue is high. Therefore, how to utilize the leach residue is an urgent
task, including recycling valuable metals and reutilizing the rest slag.
Progress of Zinc Smelting Slag Recovery and Recycling
Traditional progress of zinc smelting slag recovery and recycling focuses on zinc
and lead recovery. Nowadays more and more attention has been paid to the recovery
and recycling of other valuable metals in zinc smelting slag. The hydrometallurgical
technology has been used to recover rare and noble metals. By step-by-step removal
of impurities from the leaching solution of zinc smelting slag, Zinc and cobalt were
extracted [17].
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balance with demand. In 2019, the global refined zinc production is forecast to reach
14.95 million tons. And the predicted zinc demand is up to 15.12 million tons [4, 5].
Zinc production process generally can be divided into pyrometallurgical and
hydrometallurgical process. 90% of global zinc is produced by hydrometallurgical process. And 40% of global zinc is produced by high-acid leaching, oxygen
pressure leaching, and oxygen atmospheric leaching [7]. The zinc production lines
using the pyrometallurgical process are mainly in China, which include zinc smelting by horizontal retorting, vertical retorting, electric furnace, and imperial smelting
furnace [8]. Zinc hydrometallurgical process can be divided into two categories. The
traditional hydrometallurgical process consists of the roasting of zinc concentrate,
extraction, purification, and electrowinning. And the other one is composed by the
direct extraction of zinc concentrate, purification, and electrowinning [9].
Zinc Smelting Slag and Zinc Leach Residue
Zinc smelting slag is generated by the zinc pyrometallurgical process. In general,
total contents of zinc and lead of the zinc smelting slag are about 5–15%, while
the contents of rare and noble metals are very low [10]. Therefore, it is not economic for the recovery of valuable metals from the zinc smelting slag by the traditional hydrometallurgical processes (including acid curing and alkali leaching) and
pyrometallurgical processes. Moreover, if the zinc smelting slag is treated using a
traditional hydrometallurgical process, the leaching agent (acid or alkali) will be left
in the residues, and the gangue components in the slag are turned into a secondary
slag without utilization, which results in a secondary pollution [11–13].
Zinc leach residue, generated in the zinc hydrometallurgical process, belongs to
hazardous solid waste [14]. The composition of the leach residue is very complex,
especially the high-temperature and high-acid leach residue, which contains zinc
and other valuable metals (such as lead, copper, indium, and silver) [15, 16]. Using
the traditional pyrometallurgical or hydrometallurgical process, the treatment cost
of zinc leach residue is high. Therefore, how to utilize the leach residue is an urgent
task, including recycling valuable metals and reutilizing the rest slag.
Progress of Zinc Smelting Slag Recovery and Recycling
Traditional progress of zinc smelting slag recovery and recycling focuses on zinc
and lead recovery. Nowadays more and more attention has been paid to the recovery
and recycling of other valuable metals in zinc smelting slag. The hydrometallurgical
technology has been used to recover rare and noble metals. By step-by-step removal
of impurities from the leaching solution of zinc smelting slag, Zinc and cobalt were
extracted [17].