Effects of Simulated Rare Earth Recycling Wastewaters on Biological Nitrification

Abstract

Increasing rare earth element (REE) supplies by recycling and expanded ore processing will result in generation of new wastewaters. In some cases disposal to a sewage treatment plant may be favored but plant performance must be maintained. To assess the potential effects of such wastewaters on biological treatment, model nitrifying organisms Nitrosomonas europaea and Nitrobacter winogradskyi were exposed to simulated wastewaters containing varying levels of yttrium or europium (10, 50 and 100 ppm), and the extractant tributyl phosphate (TBP, at 0.1 g/L). Y and Eu additions at 50 and 100 ppm inhibited N. europaea, even when virtually all of the REE was insoluble. Provision of TBP with Eu increased N. europaea inhibition, although TBP alone did not substantially alter activity. For N. winogradskyi cultures Eu or Y additions at all tested levels induced significant inhibition, and nitrification shut down completely with TBP addition. REE solubility was calculated using the previously developed MSE (Mixed-Solvent Electrolyte) thermodynamic model. The model calculations reveal a strong pH dependence of solubility, typically controlled by the precipitation of REE hydroxides but also likely affected by the formation of unknown phosphate phases, which determined aqueous concentrations experienced by the microorganisms.

Indicator species drive the key ecological functions of microbiota in a river impacted by acid mine drainage generated by rare earth elements mining in South China

“…However, the ecotoxicological effects of anthropogenic REEs on aquatic microbiome are complex and have so far not been deeply explored. Here, diversity analyses found that the alpha diversity initially increased and then declined with increasing concentrations of REEs, revealing that REEs selection pressure might result from their dual roles in living microorganisms through (i) the toxicity and biological inertness of REEs (Chen et al ., 2012; Fujita et al ., 2015; Wang et al ., 2017) and (ii) REEs possibly being essential for some functional groups (Lyu et al ., 2014; Chistoserdova, 2016). For negative effects, REEs damage the outer membrane and thus significantly change cell permeability (Chen et al ., 2012).…”

“…For negative effects, REEs damage the outer membrane and thus significantly change cell permeability (Chen et al ., 2012). Previous studies also demonstrated that REEs could inhibit the growth of soil fungi (d'Aquino et al ., 2009) and decrease nitrifying bacterial activity (Fujita et al ., 2015) by competitively replacing metals in several key enzymes. However, compared to the extensive description of the negative effect of REEs in these studies, the potential physiological effect of REEs on the microbiota (positive effect) is not well documented.…”

Effective removal of calcium and magnesium sulfates from wastewater in the rare earth industry

“…3 However, it is not widely known that mining RE elements discharges considerable amounts of wastewater with high hardness. 4 The generation of wastewater containing Ca and Mg during the RE production process is illustrated in the ESI (Fig. S1 †).…”

“…The reported oral lowest published lethal dose (LDLO) of oxalic acid was 600 mg kg À1 . 17 The precipitation reactions of Ca and Mg with oxalates are presented in eqn 3and (4).…”

Synthesis of hybrid bionanocomposites and their application for the removal of rare-earth elements from synthetic wastewater

“…In another report published in 2012, only 1% of REEs was estimated to be recycled (Sadovsky, Brenner, Astrachan, Asaf, & Gonen, 2016). Thus, in 2013 the Critical Materials Institute launched by U.S. Department of Energy, to find alternatives for REEs or recycling of REEs from waste (Fujita et al, 2015) due to dependence of many technologies on REEs. Moreover, there is a necessity to recover REEs in eco-friendly way since they are toxic for living organisms if accumulated in food chain ( Adsorption is one of the most cost efficient, eco-friendly and economical method for the treatment and recovery of REEs compared to the conventional methods, which are costly, environmentally hazardous and inefficient at low concentration of REEs (Kim et al, 2015).…”