Application of Poly(caffeic acid) for the Extraction of Critical Rare Earth Elements

Abstract

Poly(caffeic acid) was synthesized and utilized for the extraction and determination of rare earth elements (REEs), thorium, and uranium. Oxidative polymerization of caffeic acid, a low-cost plant-based material, in the presence of ethylenediamine produced a granular, air-stable, and cross-linked polymer. The polymer is highly oxygenated and together with the amino group from ethylenediamine efficiently coordinates and preconcentrates these critical elements from aqueous media. Extraction was dependent on solution pH, amount of sorbent, and extraction time, while the concentration and flow rate of the desorption solution governed the recovery efficiency. Removal and recovery efficiencies greater than 98 and 90%, respectively, and low levels of detection ranging from 0.1 to 2.9 ng/L were achieved. Determination of these strategic elements in the presence of potentially interfering ions as well as in complex matrices such as well water and produced water samples also was demonstrated. The capacity of poly(caffeic acid) was determined with lanthanum as a representative REE to be 161.7 mg/g, establishing the promise of poly(caffeic acid) for larger-scale extractions in addition to the ability to screen sources for the presence of REEs.

Bioderived Pickering Emulsion Based on Chitosan/Trialkyl Phosphine Oxides Applied to Selective Recovery of Rare Earth Elements

“…In addition, various green materials based on an ion imprinted technique such as La(III)IP-CS/PVP 10 and straw-supported ion imprinted polymer 11 have been tested with good performance for La selective removal, and materials applied to solid phase extraction (SPE) developed to enrich the concentration of REE prior its quantitative analysis. For example, poly(pyrrole-1-carboxylic acid), 12 poly(caffeic acid), 13 or oxidized graphene oxide 14 demonstrated excellent selectivity toward REE but limited sorption capacity under 12 mg/g. Therefore, further research on green approaches to extract REE is required for avoiding the use of harsh chemicals and reducing EM and energy consumption.…”

Evolution of Green Sample Preparation: Fostering a Sustainable Tomorrow in Analytical Sciences

“…91,92,94 Regarding inorganic ion extraction, it is worth mentioning the contribution from Adhikari and co-workers in 2023. 119 They have applied poly(caffeic acid) granular sorbent in (d)-SPE for isolating rare earth metals, thorium, and uranium in well water and produced water samples. The key factor of this work is based on the oxidative polymerization of caffeic acid (low-cost catechol compound) in the presence of ethylenediamine to produce air-stable and cross-linked polymer.…”

“…For example, they usually have low selectivity and possess low loading capacities, which can be resolved by their hybridization with other green materials . Some of the most used natural-based sorbents are biopolymers namely cellulose, chitosan, lignin, and others. , In this scenario, a cellulosic paper device coated with different polymers (Nylon or polyamide) has been reported for the modulation of its surface polarity and, hence, modulating its selectivity toward target drugs of abuse, antibiotics, or UV filters in biological and environmental samples. Detailed information about the procedures can be found in the corresponding references. ,, …”

“…Regarding inorganic ion extraction, it is worth mentioning the contribution from Adhikari and co-workers in 2023 . They have applied poly­(caffeic acid) granular sorbent in (d)-SPE for isolating rare earth metals, thorium, and uranium in well water and produced water samples.…”