The investigation of pyrolytic char quality from mixed non-recycling plastic waste and its thermal treatment through secondary thermal pyrolytic process to activate as an adsorbent for tetracycline pollutant removal

Pyrolytic char obtained from the pyrolysis of non-recycled plastic waste becomes a problem in the domestic waste management facilities in Indonesia. Most of the char obtained from the local pyrolysis unit is left as a byproduct and considered hazardous waste. In addition, the char is considered a rich-carbon material that could be applied in various applications. However, the reports about the utilization, including the investigation of char quality obtained from a high mixture type of plastic, are never reported. Thus, the present study aims to report the char quality investigation and utilization process of pyrolytic char using secondary thermal pyrolysis at different temperatures as the adsorbent for removing antibiotic pollutants. The result shows that pyrolytic char has a graphite-like crystalline phase in all samples, along with 21 elemental impurities. TiO 2 was revealed as the highest impurity because Food-based plastic waste is dominant, which is reported to contain TiO 2 as filler. The thermal activation temperature differentiates the compositional and impurity levels of char, morphology, surface area, roughness, and adsorption performance. SEM-EDS confirmed TiO 2 as the dominant impurity at char treated at 450 °C and 600 °C, whereas SiO 2 and CaCO 3 were predominant in char treated at 750 °C. The PC activated at 600 °C exhibits the highest adsorption performance over antibiotics with maximum adsorption capacity and BET surface area of 27.393 mg/g and 13.7044 ± 0.0753 m²/g, respectively. The results found that thermal activation process offers a new and effective method for turning pyrolytic char, which is considered a low-value byproduct, into a high-performance adsorbent for contaminant removal in aqueous environments. Through optimized facile thermal pyrolytic treatment, pyrolytic char exhibits enhanced active sites and functionality due to the impurities and morphology transformation, which further provides a higher adsorption capacity.