Preparation of printing and dyeing sludge biochar/macromolecule polymer microsphere as a non-sacrificial persulfate activator with excellent reusability and reduced heavy metals leaching

Biochar-based environmental functional materials offer a promising approach for the resourceful utilization of printing and dyeing sludge (PADS). However, pollutant desorption and heavy metal leaching pose potential environmental risks. In this study, we developed a novel PADS biochar (PADSBC) macromolecule polymer microsphere with outstanding reusability and stability. This microsphere effectively activated peroxymonosulfate (PMS) for the degradation of sulfadiazine (SDZ) while significantly reducing heavy metal leaching compared with PADSBC. The SDZ removal efficiency was not influenced by the type of macromolecule polymers (calcium alginate (CA), cellulose nanofibers (CNF), and polyvinyl alcohol (PVA)) incorporated into PADSBC. In the CA-PADSBC800 microspheres/PMS system, 97% of SDZ was removed within 40 min, primarily through 1 O 2 -induced oxidative degradation (62%) and adsorption by CA-PADSBC800 (29%). Additionally, CA-PADSBC800 prevented SDZ desorption for over five consecutive cycles, while PADSBC800 exhibited 25% desorption. The presence of H C O 3 - and humic acids slightly delayed SDZ removal, while C l - slightly accelerated it. Doping CA, CNF, and CA+CNF into PADSBC800 reduced the leaching of Cu and Cr by over 90%, and Ni by over 80%, under both experimental conditions and simulated surface water and landfill leachate situations. The excellent performance of the PADSBC-macromolecule polymer microspheres was attributed to the presence of carboxyl, hydroxyl, and C=O functional groups.