Hierarchical pore carbon-calcium nanocages for highly effective removal of ammonium-nitrogen and phosphorus

• Published in: Fuel processing technology 2023-08, Vol.247, p.107804, Article 107804
• Main Authors: Zhu, Yixin, Shan, Shaoyun, Hu, Tianding, He, Liang, Zhou, Huajing
• Format: Article
• Language: English
• Subjects: Crystal deposition; Paper mill sludge; Pyrolysis; Slightly-alkaline microenvironment; Specific cage structure
• ISSN: 0378-3820; 1873-7188
• DOI: 10.1016/j.fuproc.2023.107804

Reconstructing industrial waste slags as adsorbents to purify ammonium‐nitrogen and phosphorus wastewater is a promising method. However, owing to the tight structure, most slags only have a few exposed strong metal adsorption sites for limited treatment. Thus in this paper, paper mill sludge rich in both CaCO3 and organic carbon was selected to construct a highly-active multi-porous carbon‑calcium nanocages adsorbent (Ca-pPSC750). Activation test reflected that KOH intervention not only made sludge organic matter into multistage-pore carbon, but also facilitated the uniform distribution of active CaCO3 nanoparticles. Adsorption results showed that the maximum removal capacity of Ca-pPSC750 for NH4+-N and PO43−-P was up to 248.9 and 104.1 mg g−1, more than 10 times that of the same kind of adsorbents. The whole adsorption process is not limited by the initial pH and coexisting ions of water. This work not only experimentally verifies the existence of a slightly-alkaline microenvironment on the surface of hierarchical pore carbon‑calcium nanocages adsorbents for the first time, but also eliminates the pH limitation of the adsorption reaction for pollutant remediation, thereby expanding the applicability of papermaking sludge adsorption technology. It provides a solution for the efficient purification of high concentration NH4+-N and PO43−P wastewater. [Display omitted] •Synthesized a carbon‑calcium nanocage-type adsorbent from paper mill sludge.•A slightly-alkaline environment on the surface of hierarchical pore carbon‑calcium nanocages adsorbents.•The adsorption of NH4+-N is mainly through electrostatic attraction and ion exchange.•NH4+-N and PO43−-P was removed in the form of crystal deposition.