NdFeB waste serves not only as a crucial resource for the recovery of rare earth elements (REEs) but also as an underutilized source of gallium (Ga). In this work, to simultaneously extract REEs and Ga from NdFeB waste, an efficient and novel method was developed, which involved the process of leaching, reduction, solvent extraction, precipitation, and calcination. Initially, the Pr, Nd, and Ga were co-leached with 5 mol/L HCl and liquid-solid ratio (mL/g) of 5:1 at 90 °C for 150 min, resulting in the leaching rate of Pr, Nd, and Ga were 98 %, 99 %, and 98 %, respectively. Secondly, to mitigate the interference of Fe (III) on the extraction process, Fe (III) was reduced to Fe (II) completely using Fe powder for 10 min, given that the excess iron powder factor was 1.2. Then, the tributyl phosphate (TBP) was chosen as the extractant for Ga due to its high selectivity. Under the optimal conditions, three-stage counter-current extraction achieved an extraction efficiency of 99 % for Ga, with the addition of 10 % isodecanol to eliminate the third phase. The gallium was completely stripped by water at a phase ratio (O/A) of 2:1. Subsequently, di-2-ethylhexylphosphoric acid was selected as the Pr and Nd extractant because of its high separation ability between REEs and Fe (II). The extraction efficiency of Pr and Nd achieved more than 99 % through three-stage counter-current extraction and the entire stripping of Pr and Nd was realized by 1.8 mol/L HCl. Additionally, a significant amount of Fe (II) in the raffinate was treated via adding oxalic acid to obtain FeC 2 O 4 ⋅ 2H 2 O. Finally, the Ga 2 O 3 and Nd 2 O 3 (PrO 2 ) were prepared from the stripping solution. According to the whole process, the yield of Ga, Pr, and Nd was 93.4 %, 97 %, and 98 %, with the purity of Ga 2 O 3 and Nd 2 O 3 (PrO 2 ) being 98.6 % and 98.4 %, respectively. The results suggested that the stepwise recovery of REEs and Ga from NdFeB waste can be achieved.
Qingping Zhang,Yang Xu,Haiqing Hao,Zhongxiang Guan,Meng Wang,Zongyu Feng,Xiaowei Huang,Guang Yang,Chunmei Wang
Conventional advanced oxidation processes (AOPs) face technological bottlenecks in the stepwise treatment of heavy metal complexes (HMCs), and single-step removal strategies have attracted increasing attention. Herein, we pioneered a waste-derived strategy using NdFeB waste (NFBW) to activate H 2 O 2 for establishing a heterogeneous Fenton-like system, achieving concurrent Cu-EDTA decomplexation and Cu capture. Remarkably, 99.10 % Cu-EDTA decomplexation and 96.84 % total Cu capture were synchronously achieved within 30 min. This one-step technology is effective over a wide pH range (2.0–9.5). Notably, this system demonstrated practical efficacy in treating rare-earth purification wastewater, achieving synchronous removal of heavy metals (Cu, Zn) and rare-earth elements (Yb, Ce) as mixed organic complexes with effluent meeting industrial discharge standards. Mechanistic investigations revealed that Cu-EDTA decomplexation originated from Fe(Ⅲ)-induced ligand substitution coupled with reactive oxygen species (·OH and ·O 2 - ) attack. The ≡Fe(Ⅱ)/≡Fe(Ⅲ)-mediated heterogeneous Fenton reaction synergized with homogeneous Fe(Ⅱ)/Fe(Ⅲ) cycling to generate ROSs, where the B-B bonds and Fe 0 in NFBW facilitated electron transfer for enhanced redox cycling. Possible pathways for the decomplexation of Cu-EDTA in this system are proposed. The 90.10 % TOC removal verified EDTA mineralization through stepwise degradation pathways. Liberated Cu(Ⅱ) was captured via multiple routes: surface reduction (Cu 0 ), precipitation (Cu(OH) 2 , Cu 2 (OH) 2 CO 3 ), and Fe(OH) 3 adsorption-flocculation. This work not only opens new avenues for Fenton-like treatment of HMC wastewater through a “waste-treats-waste” strategy but also provides new ideas for synergistic activation of H 2 O 2 by multivalent iron materials.
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