The beneficial properties of bioactive compounds of cannabis has renewed the scientific interest in their recovery. This review presents the available extraction techniques for these valuable compounds, along with a discussion on reporting practices.

The recovery of platinum group metals (PGMs) from secondary raw materials has become a topic of critical importance mainly due to the gradual depletion of their natural resources and their continuously increasing demand. However, the insufficient recovery of PGMs coupled with the negative environmental impact of the state-of-the-art recycling procedures mandate the investigation and development of alternative recovery processes that will assist in minimizing or even eliminating these drawbacks. Herein, we present a process for the extraction of platinum group metals from spent car catalysts relying on benign deep eutectic solvents (DESs). It is demonstrated that with addition of small amounts of an oxidizing agent, deep eutectic solvents can act as excellent leaching media for the quantitative extraction of platinum group metals. Despite its inertness towards acidic and oxidizing agents, Rh can be leached in a considerable amount which can be further increased by physical pre-treatment of the spent car catalyst material. GRAPHICAL ABSTRACT

The wide application range and ascending demand for platinum group metals combined with the progressive depletion of their natural resources renders their efficient recycling a very important and pressing matter. Primarily environmental considerations associated with state‐of‐the‐art recovery processes have shifted the focus of the scientific community toward the investigation of alternative recycling approaches. Within this context, ionic liquids have gained considerable attention in the last two decades chiefly sparked by properties such as tunabilty, low‐volatility, and relatively easy recyclability. In this review an understanding of the state‐of‐the‐art processes, including their drawbacks and limitations, is provided. The core of the discussion is focused on platinum group metal recovery with ionic liquid‐based systems. A brief insight in some environmental considerations related to ionic liquids is also provided while some discussion on research gaps, common misconceptions related to ionic liquids and outlook on unresolved issues could not be absent from this review.

Recovery of platinum group metals from spent materials is becoming increasingly relevant due to the high value of these metals and their progressive depletion. In recent years, there is an increased interest in developing alternative and more environmentally benign processes for the recovery of platinum group metals, in line with the increased focus on a sustainable future. To this end, ionic liquids are increasingly investigated as promising candidates that can replace state-of-the-art approaches. Specifically, phosphonium-based ionic liquids have been extensively investigated for the extraction and separation of platinum group metals. In this paper, we present the extraction capacity of several phosphonium-based ionic liquids for platinum group metals from model deep eutectic solvent-based acidic solutions. The most promising candidates, P₆₆₆₁₄Cl and P₆₆₆₁₄B2EHP, which exhibited the ability to extract Pt, Pd, and Rh quantitively from a mixed model solution, were additionally evaluated for their capacity to recover these metals from a spent car catalyst previously leached into a choline-based deep eutectic solvent. Specifically, P₆₆₆₁₄Cl afforded extraction of the three target precious metals from the leachate, while their partial separation from the interfering Al was also achieved since a significant amount (approx. 80%) remained in the leachate.