Study on Extraction Separation of Thioarsenite Acid in Alkaline Solution by -Type Tri-n-Octylmethyl-Ammonium Chloride.

Kang Yan,Hongxing Zhao,Lei Tian,Zhifeng Xu,Liping Liu,Ruixiang Wang

doi:10.3389/fchem.2020.592837

Abstract

To overcome the problem of arsenic separation and enrichment from an alkaline leaching solution in arsenic-containing dust, a -type tri-n-octylmethyl-ammonium chloride (TOMAC) method for extracting thioarsenite is proposed in this paper. Considering an alkaline leaching solution as the research object, after vulcanization pretreatment, TOMAC transformation and organic phase saturated extraction capacity were measured, and the extraction mechanism was preliminarily studied. First, Cl−-type quaternary ammonium salt was effectively transformed to -type by treating organic phase with saturated NaHCO3five times. TOMAC was effectively transformed from to type by alkaline washing with 1.0 mol/l NaOH solution; this washing was repeated thrice. Thereafter, the effects of organic phase composition, phase ratio, extraction time, and temperature on the extraction and separation of arsenic were investigated. The results show that under the conditions of 30% -type TOMAC + 15% sec-octanol + 55% sulfonated kerosene, VO/VA = 1/1, and 5 min extraction at room temperature, the single-stage extraction rate of AsIII is 85.2%. The AsIII concentration in raffinate can be reduced to less than 1.33 × 10−3 mol/l by four-stage countercurrent extraction, and the extraction rate of AsIII can exceed 98.4%.

Highlights

Where C1 and C2 are the concentrations of OH− and CO23−, respectively, V5 and V6 are the volumes of HCl consumed by the first and second titrations, respectively, V7 is the volume of the aqueous phase, c is the concentration of the HCl standard solution, and M3 and M4 are the molar mass of OH− (17.01 g/mol) and 1/2 CO23− (30.01 g/mol), respectively
CO23- Transformation Mechanism of tri-n-octylmethyl-ammonium chloride (TOMAC) According to the literature (Wu et al, 2017; Buev et al, 2018), the more lipophilic anions are more likely to react with the quaternary ammonium cations and enter the organic phase
The association ability of Cl− to quaternary ammonium salt cation is relatively strong, whereas that of arsenic anion is relatively weak, which is the main reason for the inhibition of arsenic extraction

Summary

INTRODUCTION

At a liquid-to-solid ratio (ml/g) of 5:1, a leaching temperature of 453 K, a retention time of 2 h, an initial sulfuric acid concentration of 0.74 mol/l, an oxygen partial pressure of 0.7 MPa, and an agitation speed of 500 r/min, 95% of copper, 99% of zinc, and only 6% of iron in the dust were leached, whereas ∼20% of arsenic was leached. Extraction of Thioarsenious Acid With CO23−-Type TOMAC CO23−-type TOMAC and thioarsenious acid solutions were mixed in a pear-shaped separating funnel according to a certain ratio of O/A for a certain period of time in an air bath constant temperature oscillator at a set temperature and settled for phase separation; the concentration of AsIII in the liquid after exchange was analyzed. The AsIII concentration in the solution after conversion was analyzed to obtain its stripping rate in the loaded organic phase

Analysis Method and Data Processing

RESULTS AND DISCUSSION

CONCLUSIONS

DATA AVAILABILITY STATEMENT