Preparation and stability enhancement of anchor bonded 3D-network extracting membrane for nickel extraction

Abstract

A novel and efficiently anchored 3-dimensional network extracting membrane (3D-NEM) with a thin functional surface layer comprising extraction carrier Bis(2-ethylhexyl) phosphate (D2EHPA) for nickel extraction was designed and studied in this paper. The active sites on the supporting Polytetrafluoroethylene (PTFE) hydrophilic ultrafiltration membrane were introduced by treating PTFE surface with potassium permanganate. Polydimethylsiloxane (PDMS) and Polymethylhydrosiloxane (PMHS) were applied to prepare a 3D network layer which is tightly anchored to the PTFE surface by introducing a crosslinking agent vinyltriethoxysilane (VTES). The prepared 3D-NEM was characterized by SEM, EDS, ATR-IR, XPS and etc. The influence of preparation parameters of 3D-NEM was studied and compared systematically. The optimum preparation conditions of 3D-NEM were based on a PDMS/PMHS/VTES ratio of 2:1:0.1 and a total polysiloxane concentration of 8 wt%. The operation stability test confirmed the average flux of the 3D-NEM in 72h reached 1871.16 mg·m-2·h-1, and only 14.42% flux declined at the end of operation. The proposed designed 3D network structure produced a 5.5 μm-functional extracting layer which has benefits in both effective fixing of D2EHPA and tight anchor to the supporting surface. This work has dual advantages in improving flux and reducing extractant loss compared to supported liquid membrane (SLM) and polymer inclusion membrane (PIM) processes.