Metals smelting-collection method for recycling of platinum group metals from waste catalysts: A mini review

Abstract

Platinum group metals (PGMs) are widely applied in the field of catalysts due to their excellent catalyst activity and high-temperature stability. The rapid generation of the waste catalyst has become the significant characteristic of PGMs with the accelerating consumption of limited PGMs nature resources. It is necessary to recover/recycle PGMs from a waste catalyst for both economic and environmental benefits. This paper reviews the PGMs recovery from waste catalysts using a metals smelting-collection process, which belongs to the main pyrometallurgical process, in the presence of various metal collectors, such as lead, copper, iron, matte, print circuit board (PCB) or reactive metals of calcium and magnesium. The current status of recovery of PGMs from waste catalysts through the addition of various metals as the collector is discussed and existing advantages and challenges are highlighted in this paper. Meanwhile, in the view of the promising processes of PGMs recovery, the influencing factors such as the economic, environmentally friendly, sustainable recycling, commercial scale, and low-grade materials are considered.

Liquid‐ and Solid‐based Separations Employing Ionic Liquids for the Recovery of Platinum Group Metals Typically Encountered in Catalytic Converters: A Review

“…Additionally, if the car catalyst material is pretreated for the removal of contaminants, the energy consumption and environmental impact of the process can be significantly reduced [55] . Despite the many advantages Cu collection offers, the subsequent PGM purification is a complex process, which produces large volumes of waste water, thus generating a secondary environmental impact [53] . It should be noted that Cu is a rather expensive collector metal [72] .…”

“…[71] PGMs are recovered from the support material slag in the form of particulate matter, [68] with the aid of collector metals, such as Cu, Fe, Ni, or Pb, which are characterized by good affinity for PGMs, and then subjected to further wetchemical processing. [53,67] This process, which allows the preconcentration of the precious metals and their separation from the slag phase, is called smelting. [53] Electrorefining of the PGM-containing Cu generates a slag with 20-25 % PGMs while Cu is recovered with high purity (99.99 %).…”

“…In addition to smelting, which is the most commonly employed pyrometallurgical approach, volatilization and sintering are also used. In gas‐phase volatilization, PGMs are brought to the gas phase by selective chlorination and subsequently separated based on the different vapor pressures that the metal chlorides possess [53] . Volatilization is not industrially favorable due to the use of toxic gases (CO and Cl 2 ), which pose health and environmental hazards.…”

“…However, since higher temperatures are employed, there is the possibility of SiO 2 reduction to Si and subsequent formation of ferrosilicon alloys, which impede PGM recovery, since these alloys are not susceptible to acid dissolution. Besides, hazardous compounds are produced in the process, meaning the generated waste has to be treated prior to release to the environment [53] . Smelting with Pb collector is one of the oldest PGM recovery methods.…”

“…A detailed discussion of pyrometallurgical approaches is beyond the scope of the present review. Readers can get a very good insight on the topic by referring to relevant comprehensive reviews by Liu et al, [53] Peng et al, [55] and Dong et al [2] In addition to smelting, which is the most commonly employed pyrometallurgical approach, volatilization and sintering are also used. In gas-phase volatilization, PGMs are brought to the gas phase by selective chlorination and subsequently separated based on the different vapor pressures that the metal chlorides possess.…”