Innovative Application of Microwave Treatment for Recovering of Rare Earth Elements from Phosphogypsum

Abstract

Some rare earth elements (REEs) are classified as strategic materials because of their increasingly high demand, supply uncertainty, and near zero recycling. For tackling the sustainability challenges associated with REEs, their technospheric mining, i.e., recovery from secondary sources, is imperative. Characterization results indicate that phosphogypsum, a byproduct of the fertilizer industry, contains about 0.03− 0.4 wt % REEs. Here, a novel process was developed that utilizes microwave irradiation to enhance the leaching efficiency of REEs from phosphogypsum. Optimal REE leaching was achieved by either microwaving at low power (600 W) and short duration (5 min) or at high power (1200 W) and long duration (15 min). The former creates cracks and pores in the particles, enhancing the infiltration of lixiviant, with minimal conversion of gypsum into less soluble crystals. The latter results in thermal degradation of the PG particles and the release of REEs at the cost of changing the PG crystal structure to less soluble phases. In all cases microwave pretreatment had a positive effect (more than 20% increase) on REE leaching efficiency. At the optimum microwaving conditions [15 min irradiation (2.45 GHz) at 1200 W], 80% Nd, 99% Y, and 99% Dy leaching efficiency was achieved.

Rare Earths’ Recovery from Phosphogypsum: An Overview on Direct and Indirect Leaching Techniques

“…Therefore, the loss of REEs during the beneficiation process mainly resulted from that portion remaining in the gypsum. Microwave radiation has also been used by Reid et al [49] and Lambert et al [50] for enrichment of PG prior to REE leaching. It was found that microwaving PG resulted in dielectric heating of water molecules present in PG crystals causing the formation of pores in the PG matrix as the water vapour escaped.…”

Bibliometric analysis of phosphogypsum research from 1990 to 2020 based on literatures and patents

“…Other countries, such as Spain, India, Brazil, and the United States, have signi cant performance in indicators that re ect the quality of papers. These countries have made many contributions to the research on the properties and utilization of PG (Campos et al, 2017;Lambert et al, 2018;Luis Guerrero et al, 2020;Nayak et al, 2018). Generally speaking, the regions where PG academic papers are produced are distributed all over the world.…”

Rapid Zeolization of Potassic Rocks by Means of a Microwave‐Assisted Hydrothermal Method

“…q e ¼A þ Blnc e (9) where A and B are constants related to adsorption potential and adsorption heat, respectively. Figure 6 shows the adsorption isotherms of zeolite CAN following the Langmuir, Freundlich and Temkin adsorption models, respectively, and Table 3 lists the isotherm parameters obtained by the three adsorption models.…”

“…Microwave has been found as a rapid, highly selective and thermally efficient heating technique, where the heat comes from the frictional loss caused by the rotation of polarized molecules in the oscillating electromagnetic field. [9] According to the previous literature reports, the microwave heating technique was mainly employed to intensify the hydrothermal process of synthesizing zeolites from activated natural minerals. [10] However, the effect of the microwave-assisted hydrothermal (MH) technique on the activation process of nature minerals is rarely reported.…”