Recovery of yttrium from deep-sea mud

Deep-sea mud rich in rare earth yttrium has received lots of attention from the international community as a new resource for Y. A novel process, which mainly includes acid leaching, solvent extraction, and oxalic acid precipitation-roasting, is proposed for recovery of Y from deep-sea mud. A series of experiments were conducted to inspect the impacts of various factors during the process and the optimum conditions were determined. The results show that the Y of deep-sea mud totally exists in apatite minerals which can be decomposed by hydrochloric acid and sulfuric acid solution. The highest leaching efficiency of Y is 94.53% using hydrochloric acid and 84.38% using sulfuric acid under the conditions of H+ concentration 2.0 mol/L, leaching time 60 min, liquid-solid ratio 4:1 and room temperature 25 degrees C (only in case of sulfuric acid, when using hydrochloric acid, the leaching temperature should be 60 degrees C). Because of the much lower leaching temperature, sulfuric acid leaching is preferred. The counter current extraction and stripping tests were simulated by a cascade centrifugal extraction tank device. Using 10 vol% P204, 15 vol% TBP and 75 vol% sulfonated kerosene as extractant, 98.79% Y3+ and 42.60% Fe3+ are extracted from sulfuric acid leaching liquor (adjusted to pH = 2.0) after seven-stage counter current extraction with 0/A ratio of 1:1 at room temperature, while other metals ions such as Al3+, Ca2+, Mg2+ and Mn2+ are almost not extracted. The Y3+ in loaded organic can be selectively stripped using 50 g/L sulfuric acid solution and the stripping efficiency reaches 99.86% after seven-stage counter current stripping with 0/A ratio of 10:1 at room temperature, while only 2.26% co-extracted Fe3+ is stripped. The Y3+ of loaded strip liquor can be precipitated by oxalic acid to further separate Y3+ and Fe-3(+). The precipitation efficiency of Y 3 + in loaded strip liquor can be 98.56% while Fe(3)(+ )is not precipitated under the conditions of oxalic acid solution concentration 200 g/L, quality ratio of oxalic acid to Y of 2, and precipitation time 0.5 h. And the precipitate was roasted at 850 degrees C for 3 h to obtain the oxide of Y in which the purity of Y2O3/REO is 79.02% and the contents of major non-rare earth impurities are less than 0.21%. Over the whole process included acid leaching, solvent extraction, and oxalic acid precipitation-roasting, the yttrium yield is 82.04%. (C) 2018 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.