Aquatic Toxicological Assessment of Solid Pyrolysis Product (SPP) from Synthetic Textile Feedstock Relative to Biochar, Carbon Black, and Activated Carbon.

Pyrolysis as a waste conversion process appears relatively feedstock-agnostic, yielding carbonaceous solid pyrolysis products (SPPs) plus condensable gases. Ground SPPs may substitute for or improve upon other carbon commodity particles, yet the environmental hazards of textile-derived SPPs have not been characterized. Here, we produced SPP particles from textile waste feedstock and from wood (biochar) using a pyrolysis process that could scale to waste management. We used electron microscopy, spectroscopy, gas adsorption, and standardized biochar analyses to characterize the chemical, morphological, and surface functionalization properties of the products. Base food-web aquatic toxicity of particle suspensions, relative to industrial carbon black and powdered activated carbon (AC), was assessed for particle concentrations up to 500 mg L-1, using marine bacterial (Aliivibrio fischeri) bioluminescence, freshwater protozoan (Tetrahymena thermophila) viability, growth and particle uptake, and freshwater microalgal (Raphidocelis subcapitata) growth. Although exposure was confirmed, for example, by protozoan ingestion of SPPs, there were no inhibitory effects of textile SPP on bacterial bioluminescence, protozoal viability or growth, or microalgal growth; textile SPP leachates appeared stimulatory to microalgae. These results suggest that SPPs from synthetic textile feedstocks may be biologically compatible with aquatic ecosystems, whereas AC induced dose-dependent reactive oxygen species (ROS) production in abiotic conditions and inhibited A. fischeri bioluminescence. This study provides critical new data on the aquatic biocompatibility of textile SPPs, supporting the circular economy by exploring the environmental safety of the conversion of mixed, synthetic textile waste.