Evolution of Environmentally Friendly Strategies for Metal Extraction

Abstract

The demand for the recovery of valuable metals and the need to understand the impact of heavy metals in the environment on human and aquatic life has led to the development of new methods for the extraction, recovery, and analysis of metal ions. With special emphasis on environmentally friendly approaches, efforts have been made to consider strategies that minimize the use of organic solvents, apply micromethodology, limit waste, reduce costs, are safe, and utilize benign or reusable materials. This review discusses recent developments in liquid- and solid-phase extraction techniques. Liquid-based methods include advances in the application of aqueous two- and three-phase systems, liquid membranes, and cloud point extraction. Recent progress in exploiting new sorbent materials for solid-phase extraction (SPE), solid-phase microextraction (SPME), and bulk extractions will also be discussed.

A perspective on developing solid-phase extraction technologies for industrial-scale critical materials recovery

“…Solid-phase extraction systems can be quite cost effective, in some cases because the sorbents themselves can be cheap to produce or acquire, but also because the solid materials tend to be highly reusable. 31 Although some sorbents are highly engineered substances synthesized in a laboratory at relatively high expense, others already exist in large quantities and need only be diverted for SPE use. Waste products from the agriculture ( e.g.…”

“…Many solid-phase extractants, as an additional advantage, can retain their function over multiple adsorption/desorption cycles. 31 The repeated process of CM retention as the sorbent is exposed to the feedstock followed by the elution and recovery of the CM, in many cases, has only a minor effect on the surface chemistry and physical structure of the extractant. 31 Even extractants with a relatively low recovery capacity could therefore potentially process a large amount of a given CM over time without needing to be replaced.…”

“… 31 The repeated process of CM retention as the sorbent is exposed to the feedstock followed by the elution and recovery of the CM, in many cases, has only a minor effect on the surface chemistry and physical structure of the extractant. 31 Even extractants with a relatively low recovery capacity could therefore potentially process a large amount of a given CM over time without needing to be replaced. This combination of inexpensive materials and reusability makes SPE a long-term, more sustainable solution for CM recovery while also limiting materials costs.…”

“…2 ). 31 In many cases, with proper process design, an SPE system can exploit the sorptive characteristics of even simple, abundantly occurring functional groups, like silanols 32 and carboxyls, 21 to achieve good separation performance. However, it may often be desirable to improve the surface functionality of a sorbent in order to increase adsorption capacity and selectivity, and these targeted adjustments are readily achievable with SPE materials.…”

Development of Alternative Green Sample Preparation Techniques

“…Extraction of metal analysis is a topic rarely discussed in terms of microextraction techniques and green sampling procedures. The review article thus offers readers a clearly defined viewpoint on various extraction strategies that minimize the use of organic solvents, such as the application of micro-methodology to minimize waste with reduced costs, improved safety, and the utilization of benign or reusable materials for extraction of metal ions from environmental samples by solvent-and sorbent-based extraction techniques [13].…”