High-flux affinity membranes based on cellulose nanocomposites for removal of heavy metal ions from industrial effluents

Abstract

Fully biobased affinity membranes based on cellulose nanocrystal functional layer for removal of heavy metal ions from industry effluents were successfully demonstrated.

Abstract

Fully biobased affinity membrane processing and its application in the removal of heavy metal ions from mirror industry effluents were successfully demonstrated; indicating the potential use of these membranes in point-of-use or point-of-entry water cleaning products that are cheap, environmentally friendly and efficient. Layered cellulose nanocomposite membranes were fabricated using cellulose microfiber sludge as a support layer and cellulose nanocrystals (CNC _SL, CNC _BE or PCNC _SL) in a gelatin matrix as the functional layer. Scanning electron microscopy (SEM) studies revealed the bi-layered morphology of the membrane and well-individualized nanocelluloses in the functional layer. Bubble point measurements confirmed the membrane pore structure in the microfiltration range (5.0–6.1 μm), which provided very high water permeability (900–4000 L h ⁻¹ m ⁻²) at <1.5 bars. A tensile strength of 16 MPa in dry conditions and a wet strength of 0.2 MPa, was considered sufficient for use of these membranes in spiral wound modules. Mirror industry effluent laden with metal ions (Ag ⁺ and Cu ²⁺/Fe ³⁺/Fe ²⁺) when treated with cellulose nanocomposite membranes, showed high ion removal capacity, being 100% for PCNC _SL followed by CNC _BE than CNC _SL. The removal of metal ions was expected to be driven by interactions between negatively charged nanocellulose and the positively charged metal ions.