This study investigated the removal efficiency and pathways of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) at environmentally relevant concentrations by marine diatom Chaetoceros calcitrans MZB-1, with a particular emphasis on kinetic analysis and optimization of environmental factors. In presence of alga MZB-1, the removal efficiencies of PFOA and PFOS at an initial concentration of 100 μg/L were 24.65 % and 29.35 %, respectively, within 15 d. The removal kinetics followed first-order models, with removal rate constants (k) of 0.014-0.019 d-1 for PFOA and 0.023-0.042 d-1 for PFOS, corresponding to the half-lives (t1/2) of 36.48-49.51 d and 16.50-30.14 d, respectively. By moderately increasing the microalgal inoculation density, the removal efficiencies of PFOA and PFOS could be improved, and the optimal initial inoculation density was 105 cells/mL. They were mainly removed through biodegradation processes, followed by biosorption and bioaccumulation. Single-factor experiments showed that the optimal growth conditions for the alga were temperature 25 °C, salinity 15 psμ, pH 8, and light intensity 60 μmol/(m2·s), while the maximum removal of PFOA and PFOS occurred at 25 °C, salinity 30 psμ, pH 8, and light intensity 200 μmol/(m2·s). The findings contributed to understanding the removal ability and pathways of marine microalgae towards per- and polyfluoroalkyl substances (PFASs), providing support for the application of microalgae in the bioremediation of PFASs-contaminated seawater.
Co-smouldering is a promising way to improve the value of products and smouldering performance, while the detailed synergistic effects between various feedstocks are still unknown. This study provides novel insights into the synergistic effects on reaction characteristics and gas production during the co-smouldering of food waste and gasification slag, which have contrasting volatile and fixed carbon contents. The results demonstrated that blending 30 % gasification slag with food waste increased the maximum allowable moisture content to 75 %. For feedstocks with comparable low heating value (6.67-6.85 MJ/kg), high fixed carbon to volatile matter ratio significantly elevated the average peak temperature from 691.0 °C to 992.6 °C and increased the CO yield from 1.00 % to 6.87 %. Volatile-derived radicals from food waste promoted the formation of disordered carbon structures and C-O functional groups on the surface of gasification slag, leading to the enhancement formation of CO and the reduction of heavy condensable components (e.g., heterocyclic compounds). Additionally, catalytically active calcium species from food waste formed oxygen-containing complexes (e.g., C-O-M) with the gasification slag char matrix, which facilitated the gasification reactions (e.g., the Boudouard reaction) and increased smouldering velocity by 24.46 %-64.23 % compared to gasification slag alone. These findings provide valuable insights for developing efficient waste-to-energy strategies, highlighting the potential of co-smouldering for fuel gas production.

