Synthesis of Low-Cost Adsorbent Material from Plastic Waste for Efficient Removal of VOCs

Abstract

Pyrolysis of plastic waste, particularly low-density polyethylene (LDPE), offers a sustainable method for producing adsorbents capable of removing volatile organic compounds (VOCs). By converting plastic waste into adsorbents, this approach not only mitigates environmental pollution challenges but also supports resource conservation and circular economy policy. This study-investigated the efficiency of an adsorbent derived from waste milk packets through slow pyrolysis, specifically targeting the removal of toluene, a common VOC. The adsorbent was characterized using Brunauer−Emmett−Teller (BET) surface area analysis, scanning electron microscopy (SEM), attenuated total reflectance (ATR) spectroscopy, and X-ray diffraction (XRD). Preliminary experiments were conducted to assess the operating parameters, which were further used to determine the toluene removal efficiency. The study examined the impact of three process parameters: temperature (°C), heating rate (°C/min), and residence time (min) on the yield of adsorbents. Optimization of the adsorbent yield (%) was performed using the Box−Behnken design of response surface methodology (RSM). The findings indicated that the process reactions are adequately predicted using the specified input parameters. The optimal conditions for maximizing adsorbent yield were identified as temperature of 600 °C, heating rate of 12.5 °C/min, and residence time of 90 min, resulting in an adsorbent yield of 98.06%. Under optimal conditions, the adsorbent demonstrated maximum removal efficiencies of 100, 80, and 95% for inlet toluene concentrations of 10, 50, and 100 ppm, respectively. Adsorption kinetics of toluene on the adsorbent followed a first-order model, indicating a rate dependent on the number of available adsorption sites, while adsorption equilibrium data were best described by the Freundlich isotherm, suggesting multilayer adsorption on a heterogeneous surface.