Physical and Electrical Properties of Polylactic Acid-Based Adsorbents for the Malachite Green Dye Removal with Potential Sensoric Application

Abstract New adsorbent films for the biosorption of malachite green (MG) dye from water were prepared using polylactic acid (PLA) as a renewable, degradable and thermoplastic polymer matrix, instead of widely used crosslinked systems. Polyaniline (PANI) and carbon fibers (CFs) were added to PLA through vigorous sonication followed by a casting technique to create electrically conductive PLA-based adsorbent films with enhanced functionality and adsorption properties. The composite films were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, and BET-surface area measurements to identify their functionality as adsorbents for removing MG dye from water. The produced PLA/PANI/CFs composite films exhibited higher electrical conductivity and surface area compared to PLA and PLA/PANI films. The effects of adsorbent film composition, contact time, pH, and dye concentration on adsorption efficiency were assessed. The adsorption test confirmed effective removal of MG dye with maximum adsorption capacities of up to 60.1 mg/g. The isotherm data fitted the Langmuir model with an R 2 value of 0.99, implying a chemisorption process. The fabricated biosorbents disclosed the first-order kinetic model with high R 2 values and an exothermic reaction with the MG dye, as the process is stimulated by a decrease in temperature. Adsorbent regeneration and the significant effect of various MG concentrations on electric conductivity, which changed by two orders of magnitude, demonstrated the applicability of PLA/PANI/CFs composite films as potential MG dye sensors.