Fabrication Of Chitosan And Lignosulfonate Membranes By Electro-assembly And Its Application

In recent years, the layer-by-layer self-assembly (LBLSA) method has attracted muchattention due to its availability on producing nanomaterials. However the driving force of LBLSAis weakly to influence the mechanical property and practicability of fabricated multilayer samples.To assemble polyelectrolyte multilayers with the assistance of electric field has been recentlyreported elsewhere, however, it is truly that all reported cases using very lower voltages. Chitosan(CS) and ligninsulfonate (LGS) are natural polyelectrolytes with opposite charges, e.g. the formerin positive and the latter in negative. These natural polymer polyelectrolytes are cheap, easy toproduce and non-toxic thus widely applied in the fields of biological, medicine, environmentalprotection, chemical industry and others. This work developed a novel layer-by-layerelectro-assembly (LBLEA) method by applying an electrostatic generator to provide variablevoltages and applied to fabricate independent CS or LGS films, then the (CS/LGS)nfilms withalternative outermost. During this LBLEA process, the electrostatic forces were enhanced orreduced by taking two opposite electrodes alternatively linking to CS or LGS solution. In thiswork, we applied surface tension measurement, water contact angle measurement, infraredspectroscopy (IR), atomic force microcope (AFM), scanning electron microscope (SEM), X-raydiffraction (XRD) to charaterize those samples. Additionally, the CS and LGS films were alsostudied of thie possible applications, i.e. the former was applied to separate oil/water solution, andthe latter was applied to adsorb copper(II) ions. In terms of analysis, the advantages anddisadvatanges of those samples formed by LBLEA were evaluated as below.(1) The surface tension of CS and LGS solution was found to reduce with the voltageincrease suggesting the LBLEA was performed with low surface tension solution as compared tothe normal LBLSA.(2) Water contact angle on LBLEA formed independent CS and LGS film surface was reduced with the voltage reduce to lead the CS surface to enhance its hydrophilicity, and for LGSsurface to turn its hydrophilicity to superhydrophilicity (3.91°). On (CS/LGS)nfilm surface, theLBLEA formed samples presented enhanced hydrophobicity, especially for CS outermost becauseit was turned from hydrophilic to hydrophobic (103.9°).(3) ATR-FTIR spectra analysis found that the LBLEA process caused the CS and LGS filmsurface to reveal the hydrophilic groups. For (CS/LGS)nfilms, the applied voltages also inducetheir structure change indeed.(4) AFM and SEM images showed that the applied LBLEA method caused the surface ofthose films to change the roughness/smooth and the thickness.(5) XRD results showed that the LBLEA process improved the crystallinity of the CS andLGS films.(6) The LBLEA formed CS film showed better separation possibility than that of the LBLSAformed sample (0V), and the LBLEA formed LGS film showed better copper(II) ions adsorptionability than that of the LBLSA formed sample (0V).