Mechanochemical synthesis of oxygenated alkynyl carbon materials with excellent Hg(II) adsorption performance from CaC₂ and carbonates

Adsorptive removal of heavy metal ions from wastewater is very important, and the key is the development of efficient sorbents. In this work, oxygenated alkynyl carbon materials (OACMs) were synthesized via mechanochemical reaction of CaC₂ and a carbonate (CaCO₃, Na₂CO₃, or NaHCO₃) at ambient temperature. The resultant OACMs are micro mesoporous carbon nanomaterials with high specific area (>648 m² g^-1), highly crosslinked texture, and rich alkynyl and oxygenated groups. The OACMs exhibit excellent Hg(II) adsorption due to the soft acid-soft base interaction between alkynyl and Hg(II), and OACM-3 derived from CaC₂ and NaHCO₃ has the saturated Hg(II) adsorbance of 483.9 mg g^-1 along with good selectivity and recyclability. The adsorption is mainly chemisorption following the Langmuir mode. OACM-3 also shows high adsorbance for other heavy metal ions, e.g. 256.6 mg g^-1 for Pb(II), 232.4 mg g^-1 for Zn(II), and 198.7 mg g^-1 for Cu(II). This work expands the mechnochemical reaction of CaC₂ with carbonates and possibly other oxyanionic salts, provides a new synthesis approach for functional alkynyl carbon materials with excellent adsorption performance for heavy metal ions, as well as a feasible approach for CO₂ resource utilization.