Recovery of Trace Rare Earths from High-Level Fe³⁺and Al³⁺Waste of Oil Shale Ash (Fe−Al−OSA)

Abstract

An experimental investigation was undertaken to study the high-efficient and clean enrichment of trace rare earths from high-level Fe 3+ and Al 3+ waste of oil shale ash (Fe-Al-OSA). The optimum leaching temperature, ratio of solid to liquid, acidity, and reaction time for Fe-Al-OSA were 30°C, 1:7, 50% (v/v), and 1 h by the Taguchi method, respectively, and the leaching rate of rare earths has been reached up to 96.24%. The optimal extraction conditions for removing Fe 3+ from leaching liquor of Fe-Al-OSA were as follows: the organic phase was 30% N235 + 10% isooctyl alcohol (ROH) + 60% n-heptane, acidity of aqueous phase was about 3.00 mol/L, and phase ratio (V o :V w ) was 8:5. More than 92.09% of Fe 3+ was recovered by using countercurrent extraction process with 4-5 stages. The 99.76% of high pure Fe byproduct was obtained by stripping the loaded N235 organic phase, and it can be used as chemistry pure reagent directly. After adjusting the pH of the raffinate to 6.00 with MgO and saturated Na 2 CO 3 solution, all of the Al 3+ and rare earths were transformed to hydroxide precipitation and separated from the solution, together with other small amounts of coexisting metal ions such as Ca 2+ and Mg 2+ . Then, the precipitation was washed, collected, and dissolved by HNO 3 . Rare earths can be separated from the solution by solvent extraction with 30% tributyl phosphate (TBP) +70% n-heptane at the phase ratio (V o :V w ) 3:2. The recovery rate of rare earths from Fe-Al-OSA has reached 86.30% in the whole separation process. The residual Al 3+ in solution was recycled. This work shows that such a treatment route is one kind of highly efficient and clean method for separating Fe 3+ and Al 3+ , and concentrating rare earths from Fe-Al-OSA. The solid waste (Fe-Al-OSA) from the refinery can also be utilized effectively to solve the ecological and environmental problems caused by the waste heap.

Recovery of Gallium from Corundum Flue Dust by Two-Stage Alkali Leaching, Carbonation, Acid Leaching and Solvent Extraction Process

“…In addition, the extraction and stripping efficiencies of iron were about 99% and 96%, respectively. In the process of solvent extraction, tertiary amine only extracted Ga 3+ and Fe 3+ in leachate, while Al 3+ remained in the raffinate [22,28]. As a result, major elements in the strip solution were gallium and iron, and the concentrations of Ga and Fe in this solution were about 2 g/L and 1 g/L, respectively.…”

Recovery of the Rare Metals from Various Waste Ashes with the Aid of Temperature and Ultrasound Irradiation Using Chelants

“…Leaching via acidic and alkaline treatments, followed by a subsequent step of metal recovery from leachates involving either solvent extraction, selective precipitation, or solid-phase separation (Tsuboi et al 1991, Vitolo et al 2000, Font et al 2007, Navarro et al 2007, Yang et al 2010, and vapor phase extraction (Murase et al 1998) is attempted to reclaim rare metals from the waste ashes.…”

Integrated Process To Recover NiMH Battery Anode Alloy with Selective Leaching and Multistage Extraction

“…In the Taguchi method, the productivity can be improved at low cost by arranging factors into an orthogonal array. 26 An orthogonal array of L 9 (3 4 ), which denotes four parameters (temperature, ratio of solid to liquid, acid concentration, and reaction time) all with three levels, was chosen and is represented in Supporting Information Table S1. Under these conditions, the leaching experiment was carried out in a round-bottom flask fitted with a condenser.…”