Effect of polyurethane structure on arsenic adsorption capacity in nanofibrous polymer/ferrous sulphate-based systems

This study investigates the effect of the nanofibrous polymeric structure of an adsorptive material, modified with an immobilized inorganic sorbent based on ferrous sulphate, on the capacity of the material to remove arsenic from contaminated water. Nanofibrous materials were prepared by electrospinning from polyurethane types selected using a primary adsorption test. The functional groups and chemical composition (FTIR, EDX), morphology (SEM, porometry) and hydrophilicity (contact angles) of the prepared nanostructured materials were determined in order to assess the effect of composition and structure on the removal of arsenic. The process of arsenic removal was monitored by atomic absorption spectroscopy (AAS). It was found that certain samples of polyurethanes, particularly self-synthesized aromatic polyurethane of an ester type, PU918, could remove arsenic by complexation on nitrogen in their polymer chains. The greatest efficiency for arsenic removal was ca. 60% (initial c(As) = 150 mu g L-1). It was also found that adding even a small amount (1 wt%) of an inorganic adsorbent based on ferrous sulphate into the fibre mass of the nanofibrous structure would increase the efficiency up to 90% as a result of a chemical reaction between the additive and arsenic ions. The extent and rate of adsorption were described by kinetic and isotherm models. The adsorption process is well characterized by a pseudo-second-order kinetic model and both Freundlich and Langmuir isotherm models. High adsorption capacity and rate are the basis for the use of nanofibrous material in filters for arsenic separation.