Removal of Ni (II) and Cr (III) by complexation-ultrafiltration using rotating disk membrane and the selective separation by shear induced dissociation

• Published in: Chemical engineering and processing 2019-01, Vol.135, p.236-244
• Main Authors: Zhang, Qiang, Gao, Jing, Qiu, Yun-Ren
• Format: Article
• Language: English
• Subjects: Complexation-ultrafiltration; Critical shear rate; Selective separation; Shear induced dissociation; Shear stability
• ISSN: 0255-2701; 1873-3204
• DOI: 10.1016/j.cep.2018.12.005

[Display omitted] •Distribution of shear rate on the membrane surface was calculated.•Critical shear radii at different rotating speeds were calculated.•Critical shear rates of the complexes at different pH values were obtained.•Shear stability of PAA-Cr complex was higher than that of PAA-Ni complex.•Selective separation of Cr and Ni was achieved by shear induced dissociation. Removal of Ni (II) and Cr (III) from aqueous solutions by complexation-ultrafiltration and the selective separation by shear induced dissociation were investigated using rotating disk membrane (RDM). Experiments were carried out as a function of pH and mass ratio of PAAS to metal (P/M) for the removal of Ni (II) and Cr (III) by polyacrylate sodium (PAAS) as complexing agent and the results revealed that the optimum conditions were pH 7.0 and P/M 25. Effect of rotating speed (n) on the rejection of complexes of PAAS with nickel (PAA-Ni) and chromium (PAA-Cr) at different pHs were studied and the results proved that both PAA-Ni and PAA-Cr complex would dissociate when n exceeded a certain value. The critical shear rates, at which PAA-Ni or PAA-Cr complex began to dissociate, were calculated at different pH values, and the critical shear rate of PAA-Cr complex was greater than that of PAA-Ni complex at the same pH, which indicated that the stability of PAA-Cr complex was stronger than that of PAA-Ni complex. Furthermore, the influences of operation parameters on selective separation coefficient (βNi/Cr) were investigated and the results showed that the rotating speed and pH significantly affected βNi/Cr. Finally, shear induced dissociation was used to effectively separate Ni(II) and Cr(III) and regenerate PAAS at 1800 and 2500 rpm, respectively.