Mini-Review on the Use of Liquid Membranes in the Extraction of Platinum Group Metals from Mining and Metal Refinery Wastewaters/Side-Streams

Abstract

The current mini-review focuses on the use of liquid membranes in the platinum group metal (PGM/PGMs) extraction from various types of wastewaters to prevent environmental pollution; and for the metal recovery to address the scarcity of the PGMs in the industrial cycles. The bulk liquid membranes have been used to the extracted PGMs from the (acidic) aqueous media with recoveries of up to 96.3 ± 2.5% of the original PGM amount. The extraction time generally ranges from 2 to 24 hours. The bulk membrane liquid in the PGM extraction will depend on the covalent structure of the extractant, the feed phase PGM concentration and the complex of the PGM in question that is actually extracted from the aqueous environment. The advantages of this type of liquid membrane include its operational simplicity, but the disadvantages include limited possibility to improve the extraction performance of the system. Literature data are encouraging as they indicate that extraction of PGMs from mining and metal-refinery side-streams does not suffer from interference from metal contaminants that are commonly found in the mining and metal refinery side-streams, e.g. iron. Thus further research should focus on the application of ELM to extraction of PGMs from said wastewaters and major research drive should focus on the use of the Taylorvortex column and the non-Newtonian ELMs. With the supported liquid membranes, 78-82% of the original PGM content could be recovered from model side-streams. The selectivity of the extraction for individual PGMs can be controlled by the extractant used.Palladium is the most studied PGM with respect to extraction from wastewater using the LM technology. Extractants that have been used in this regard include di-2-ethylhexyl-thiophosphoric acid [8], 8quinolone derivatives [9] and Cyanex 471 [10]. Various arrangements of the LM have been used, e.g. the ELM with LIX 984N-C as the extractant [11]. The SLMs have been used to extract various PGMs from wastewater using the following extractants: Aliquat 336 for Pt (IV) [12], Pd (II) [13] and Rh (III) [14]; and MSP-8 for Pd(II) [15]. Quantitative extraction is generally achieved within 2 to 24 hours [16].Stripping phases generally contain HCl or HNO 3 and sometimes this is supplemented by thiourea [17]. The current mini-review focuses on the use of LMs in the PGM extraction from various types of wastewaters. The article will cover the metal removal from the mining and metal-refinery side-streams, wastewaters from battery production and other potential sources of environmental pollution; and metal recovery to address the scarcity of the PGMs in the industrial cycles.

Analytical Applications of Transport Through Bulk Liquid Membranes

“…Depending on the possible configurations that liquid membranes can adopt these can be classified in: bulk liquid membranes (BLM), emulsion liquid membranes (ELM) and supported liquid membranes (SLM) (Kislik, 2009;Kamiński and Kwapiński, 2000;San Roman et al, 2010;Moyo and Tandlich, 2014;Belova et al, 2014;Ghoshal and Saha, 2014). The most known type of liquid membranes is the bulk liquid membrane.…”

Application of Taguchi Method for Optimization Cadmium Separation by Emulsion Liquid Membrane

“…Román et al [4] Liquid membrane applications can be implemented using units with different designs of liquid membranes. Therefore, liquid films can be classified according to these designs into Bulk liquid membrane (BLM), supported liquid membrane (SLM), and Emulsion liquid membrane (ELM) Moyo et al [5]. The emulsion liquid membrane (ELM) can achieve much higher mass transfer.…”