A Novel Cellulose Acetate Fouling-Resistant Ultrafiltration Membranes for Heavy Metal Remediation

Water contamination by traces of heavy metals is a global issue causing serious environmental and health concerns and, as a consequence, an increasing of demand for water remediation technologies. Nowadays, membranes, defined as a selective barrier that permit the separation of molecules or ions in a liquid by a combination of sieving and diffusion mechanisms, have more attention due to their several advantages. In particular, ultrafiltration (UF) is a well-established membrane technology for purification of contaminated water bodies enabling an efficient and cost-saving low-pressure filtration. However, UF membranes possesses a pore size ranging from 20 nm to 0.1 µm, ineffective in rejecting small molecules and ions, such as heavy metals. In this work, a new generation of antifouling UF membranes able to heavy metals remediation has been developed [1]. Specifically, poly (acrylic acid) (PAA) as ideal complexing agent for heavy metals, was blended with cellulose acetate (CA), polymer extensively studied in UF membranes preparation. The novel membranes were prepared via non solvent-induced phase separation (NIPS). These new membranes combine the use of carboxyl group of the PAA that allowing one to efficiently adsorb or chelate heavy metal ions with the processability/biocompatibility/hydrophilicity of the CA. The membranes were produced varying the PAA concentration from 0 to 15wt. %. The homogeneity of the blend was evaluated via differential scanning calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FTIR). Mitigation of the fouling phenomena and the improvement of the efficiency of the CA membrane on heavy metal rejection was studied and evaluated. The experiments results revealed the important advantages of the blend, since CA/PAA membranes showed superior performance with respect to the neat CA membrane, in terms of: (i) water permeability (20% higher than the neat CA membrane); (ii) Cd rejection (83% at pH 6.5); and (iii) antifouling resistance to humic acid (HA) (R% of 99.9 and 95.3% of flux recovery ratio FRR).

 

[1] I. Ounifi, Y. Guesmi, C. Ursino, S. Santoro, S. Mahfoudhi, A. Figoli, E. Ferjanie, A. Hafiane, Antifouling Membranes Based on Cellulose Acetate (CA) Blended with Poly(acrylic acid) for Heavy Metal Remediation, Appl. Sci. 2021, 11, 4354. https://doi.org/10.3390/app11104354