Electrospun adsorbent membrane of PLA containing chitosan for toxic metal ions removal from aqueous solution: Effect of chitosan incorporation

The scarcity of water resources and their pollution are vital to modern civilization. Thus, adsorptive membranes are promising candidates to be applied in the filtration systems to improve the water quality. In summary, this study investigated the effect of chitosan (CS) in the morphological, chemical, and physical aspects of PLA-based membranes incorporating chitosan obtained by electrospinning process, their adsorption behavior in multielement aqueous systems containing Cr6+, Cu2+, Zn2+, Mn 2+, Ni2+, and Cd2+ in pH 4, and the possible removal mechanism on the composite electrospun membrane's surface. The addition of chitosan within the PLA matrix reduced the diameters and porosity of the fibers and pores, resulting in an improvement in the modulus of elasticity and tensile strength until rupture, reaching values around 346.4 f 61.4 MPa and 4.57 f 0.69 MPa for mechanical tests carried out in the alignment of fibers with the highest percentage of CS. Besides, the contact angle varied between 70 f 5 degrees and 114 f 3 degrees, depending on side of membrane's surface (smoother or rougher). For removal efficiency of six metal ions in multielement aqueous systems, the best results were verified for Cr6+ (40 up to 100 %). The adsorption efficiency did not significantly change when the chitosan content increased, but the value increased for Cr6+ percentage drastically. From SEM-EDS and XPS, indicatives of possible adsorption mechanism showed the contribution of amino groups and oxygen-rich functional groups of chitosan (especially oxyanion chromium); the PLA chain ends (active -COO- sites) for divalent metal ions removal, and the lowest ionic radius of chromium, that facilitate its removal. Thus, PLA membranes containing chitosan are a promising candidate with excellent mechanical and adsorptive properties for environmental remediation.