Chelation-Assisted Ion-Exchange Leaching of Rare Earths from Clay Minerals

Abstract

The effect of biodegradable chelating agents on the recovery of rare earth elements (REE) from clay minerals via ion-exchange leaching was investigated, with the aim of proposing a cost-effective, enhanced procedure that is environmentally benign and allows high REE recovery while reducing/eliminating ammonium sulfate usage. A processing route employing a lixiviant system consisting of simulated sea water (equivalent to about 0.5 mol/L NaCl) in conjunction with chelating agents was also explored, in order to offer a process alternative for situations with restricted access to fresh water (either due to remote location or to lower the operating costs). Screening criteria for the selection of chelating agents were established and experiments were conducted to assess the efficiency of selected reagents in terms of REE recovery. The results were compared to extraction levels obtained during conventional ion-exchange leaching procedures with ammonium sulfate and simulated sea water only. It was found that stoichiometric addition of N,N′-ethylenediaminedisuccinic acid (EDDS) and nitrilotriacetic acid-trisodium form (NTA-Na3) resulted in 10–20% increased REE extraction when compared to lixiviant only, while achieving moderate Al co-desorption and maintaining neutral pH values in the final solution.

On membrane-based approaches for rare earths separation and extraction – Recent developments

“…As a consequence of dynamic scientific and technological progress during WWII, the primary efficient REE separation was accomplished with the implementation of ion exchange chromatography. The principle of the separation was the diversification in the stability of rare-earth citrate chelates [70][71][72]. Later on, around 1954, liquid−liquid extraction was developed and effectively applied in the commercial production [73].…”

Recovery and Recycling of Valuable Metals

“…Seventeen articles have been published in this Special Issue of Metals, encompassing the fields of mineral processing and extractive metallurgy [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. These articles cover a wide range of topics in the field and provide some ideas for active researchers who are working on the production of valuable metals from primary and secondary resources.…”

Cetylpyridinium Bromide/Polyvinyl Chloride for Substantially Efficient Capture of Rare Earth Elements from Chloride Solution

“…The second process implicates attaching the chelating complex to a support material. For individual REE extraction, various solid-extraction approaches have been conceived using solid supports of distinct types such as activated carbon, clays, SiO 2 , polymeric resins, titanium oxide, and naphthalene [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. The extraction of lanthanides from positively acidic wastes has been proposed using a resin, which was developed by a dihexyl succinamic/chloromethylated polymer [ 22 ].…”