Preparation of Polyvinyl Alcohol (PVA)-Based Composite Membranes Using Carboxyl-Type Boronic Acid Copolymers for Alkaline Diffusion Dialysis

Abstract

Carboxyl-type boronic acid copolymers (CBACs) were synthesized by a radical polymerization method and used for the preparation of polyvinyl alcohol (PVA)-based composite membranes via a solution mixture method. The as-prepared composite membranes exhibited a water uptake (WR) of 122.6–150.0%, an ion exchange capacity (IEC) of 0.0147–0.0518 mmol g−1, and excellent mechanical (elongation at break (Eb) of 103.8–148.4%, tensile strength (TS) of 38.7–58.6 MPa) and thermal stability. The alkali resistances of the as-prepared membranes were tested by immersing the samples into 2 mol L−1 NaOH solutions at 25 °C for 60 h, and the results were encouraging: the mass loss and swelling degree of the as-prepared membranes were in the ranges of 1.9–5.9% and 222.6–241.9%, respectively. The separation performances of the as-prepared membranes were evaluated by the diffusion dialysis (DD) process with an NaOH/Na2WO4 mixture at room temperature. The results demonstrated that the dialysis coefficients of hydroxide (UOH) were in the range of 0.0147–0.0347 m h−1, and the separation factors (S) were in the range of 29.5–62.6. The introduced carboxyl groups from CBACs and the –OH groups from PVA were both deemed to play significant roles in the promotion of ion transport: the –COO− groups formed negatively charged transport channels for Na+ by electrostatic attraction, and the –OH groups promoted the transport of OH− via hydrogen bonding.

Anion Exchange Membrane Based on BPPO/PECH with Net Structure for Acid Recovery via Diffusion Dialysis

“…The microstructure of the membrane was one of the important factors affecting the performance of the membrane. From Figure 2, it can be seen that membranes 1-5 experienced slight phase separation, which allowed more ions to pass through membrane; thus, the efficiency of the acid recovery was enhanced [36,37]. At the same time, the Fe 2+ ion transportation rate was also increased [36].…”

Preparation of a Cation Exchange Membrane by a Sol-Gel Method-Based Polyvinyl Alcohol to Improve Alkali Recovery via Diffusion Dialysis in the Textile Industry

“…From the collected data, U OH − value was increased from 0.012 mm/h to 0.023 mm/h with the increase in SAGS content. That was mainly due to the fact that -SO 3 H groups carried the negative charge, so OH − and WO 4 2− groups which carried the same charge were hardly able to pass through the cation exchange membranes [52]. On the contrary, those cations in the feed solution can be easily transported to the side.…”