Flotation separation of strontium via phosphate precipitation

Abstract

Flotation separation of strontium (Sr) from wastewater via phosphate precipitation was investigated. While 37.33% of Sr precipitated at highly alkaline pH in the absence of PO, it completely precipitated as Sr(PO) at a molar ratio ([PO]:[Sr]) of 0.62 at a lower pH value. The presence of Ca hindered Sr precipitation, yet it could be overcome by increasing the PO dose. Sodium dodecyl sulfate (SDS) was a better collector for dispersed air flotation of Sr(PO) than cetyl trimethyl ammonium bromide, or mixed collector systems of SDS and saponin. The highest separation efficiency of 97.5% was achieved at an SDS dose of 40 mg/L. The main mechanism in the precipitate flotation is adsorption of anionic SDS on the positively charged surface of colloidal Sr(PO) via electrostatic interaction. SDS enhanced the aggregation of Sr(PO) precipitates as the size increased from 1.65 to 28.0 μm, which was beneficial to separation as well.

New Process for the Sulfonation of Algal/PEI Biosorbent for Enhancing Sr(II) Removal from Aqueous Solutions—Application to Seawater

“…Metal removal may involve different techniques; however, sorption and biosorption processes have retained great attention for low-concentration effluents [ 7 , 8 , 9 , 10 ]. Though precipitation and flotation techniques can be used for pre-treating strontium-bearing effluents [ 11 , 12 ], it is generally useful to couple different techniques [ 13 ] for reaching high levels of metal recovery. For the specific treatment of complex solutions (such as brines and seawater), it is thus necessary to design new sorbents having high selectivity against alkaline and alkaline-earth competitor ions.…”

Recycling of High-Purity Strontianite and Hematite from Strontium-Bearing Sludge

“…Fe impurities in the sludge are dissolved by strong acids and decrease to residual concentrations of 5.7−44.7 g/L in the leachate. 16 Second, Sr is separated from Sr-bearing leachate through the following approaches: cationic exchange, 17 chemical precipitation, 18,19 solvent extraction, 20−22 and membrane filtration. 23,24 However, Fe is present in high concentrations in Sr-bearing leachate and shows high affinity with resins, extraction agents, and membranes.…”

“…Fe impurities in the sludge are dissolved by strong acids and decrease to residual concentrations of 5.7–44.7 g/L in the leachate . Second, Sr is separated from Sr-bearing leachate through the following approaches: cationic exchange, chemical precipitation, , solvent extraction, − and membrane filtration. , However, Fe is present in high concentrations in Sr-bearing leachate and shows high affinity with resins, extraction agents, and membranes. , For example, although the use of di- t -butylcyclohexano-18-crown-6 results in efficient Sr extraction from the acidic leaching solution of a radioactive tank sludge, this approach results in Fe extraction and retention at a concentration of 12 mg/L in the extracting solution . Such defects limit the applications of this method for high-purity Sr recovery.…”