A novel layer-by-layer heterogeneous cation exchange membrane for heavy metal ions removal from water.

A novel layer-by-layer (LbL) cation exchange membrane was prepared for heavy metal ions removal from water via electrodialysis. LBL membranes fabricated by coating of [chitosan-co-activated carbon nanoparticles] layer on polyvinyl chloride-based heterogeneous cation exchange membrane. Betterment in adherence of layers was achieved through glutaraldehyde cross linking. FTIR, FESEM, 3D-surface images and BET analysis were used for LBL membrane characterization. Membrane surface hydrophilicity, flux, membrane potential, transport number, and their permselectivity were studied. FTIR spectra confirm LbL formation decisively. FESEM images and BET analysis demonstrated that coating of second layer on PVC membrane led to a compact structure. LbL membrane showed smoother and more hydrophilic surface compared to pristine membrane. The transport number and permselectivity increased by deposition of second layer whereas sodium flux showed up-down trend. ED experiment showed good ability in heavy metal ions removal for LBL membrane that follows (Cu2+> Ni2+> Pb2+) sequence. EDX analysis showed a competitive adsorption for heavy metal ions on LBL membrane as (Pb2+> Cu2+≥Ni2+). The effect of ultrasonic waves on regeneration of fouled membranes by heavy metals was investigated. The results showed improved performance for the regenerated membrane. Mechanical resistance also improved by utilizing of ACNs in chitosan layer.

Tailoring the electrochemical properties of ED ion exchange membranes based on the synergism of TiO2 nanoparticles-co-GO nanoplates.

In this paper, the synergetic influence of various weight ratios of TiO2 nanoparticles (NPs)/graphene oxide nanoplates (GONs) in the matrix of ion exchange membranes was examined in order to adapt their electrokinetic properties based on the combination of the high specific surface area of GONs and the antifouling ability of TiO2 nanoparticles. The morphology, physico-chemical features and ionic transport behavior of prepared membranes was studied. Scanning optical microscopy (SOM) and scanning electron microscopy (SEM) images showed a uniform surface for the lab-made membranes relatively. It was found that surface hydrophilicity of the membrane was increased in the presence of GONs and TiO2 NPs. All modified membranes showed a higher water uptake than unmodified membranes. Furthermore, a higher ion exchange capacity, fixed ionic concentration, ionic permeability and flux were observed for all modified membranes in comparison with unmodified membranes. The membrane potential, transport number and selectivity improved in NaCl solutions by using GONs and TiO2 nanoparticles. Furthermore, the membrane ionic conductivity showed an increasing trend by utilizing TiO2-co-GONs NPs. As an overall conclusion, the modified membrane containing 3wt% GONs and 1wt% TiO2 NPs with superior transport number and permselectivity (∼99%), highest current density and cation flux and the lowest areal electrical resistance (∼4-5Ωcm2) showed the best performance.