Influence factor of Pr(III) recovery kinetics from rare-earth simulant wastewater by PAN microtubule hyperfiltration reactor

Abstract PAN microtubule hyperfiltration reactor (PMHR) with organic phosphate system containing simulant wastewater section with buffer solution acetic acid and enrichment section with nitric acid solution and organic phosphate C 16 H 35 O 4 P (Di (6-methylheptyl) phosphate) dissolved in benzin, has been studied for the praseodymium (III)[expressed as Pr(III) or Pr 3+ ] recovery in the rare-earth simulant wastewater. Many factors of Pr(III) recovery using PMHR need to explore, including hydrogen ion concentration (or pH), cinit of Pr(III) and different ionic strength of rare-earth simulant mine wastewater, volume ratio of C 16 H 35 O 4 P with benzin and nitric acid solution (O/W), nitric acid concentration, C 16 H 35 O 4 P concentration, different acid solution of enrichment section on Pr(III) recovery with PMHR were investigated. The experimental results show that the best recovery conditions of Pr(III) were obtained as that nitric acid concentration was 4.00 mol/L, C 16 H 35 O 4 P concentration was 0.200 mol/L, and O/W was 0.6 in the enrichment section, and pH value was 4.90 in the wastewater section. Ionic strength of rare-earth simulant mine wastewater had no obvious effect on Pr(III) recovery. When cinit of Pr(III) concentration was 1.67 × 10 −4 mol/L, the recovery percentage of Pr(III) was up to 94.7% in 160 min. The kinetic equations were developed, and diffusion coefficient in the microtubule reactor and thickness of diffusion layer between the wastewater section and the microtubule pipe wall were obtained by linear slope method. They were 4.16 × 10 −6 m 2 /s and 4.65 μm, respectively. PMHR, owing to a large number of C 16 H 35 O 4 P was used in the enrichment section, can renewal the losing carrier of microtubule reactor. As a result, the recovery percentage of Pr(III) was increased, the stability of PMHR system was enhanced, and the life span of the PMHR system was extended.