Intercalation of thiacalix[4]arene anion via calcined/restored reaction into LDH and efficient heavy metal capture

- TCAS-LDH composites with different TCAS arrangement were synthesized via calcined-restored method.
- The obtained composites are highly selective and efficient for Pb2 + and Cu2 +.
- Adsorption of Pb2 + and Cu2 + is probably due to the bridging S atoms.
- The adsorption kinetics and isotherm were discussed.

The main objective of this work is to synthesize TCAS-LDHs composites with different TCAS arrangement in LDH interlayer and investigate the adsorption properties of TCAS-LDHs composites for toxic heavy metal ions. The Mg2Al-TCAS-LDH and Zn2Al-TCAS-LDH composites were synthesized via calcined-restored method. The XRD patterns showed that TCAS had introduced into the interlayer, with alternating “up-down” antiparallel arrangements for Mg2Al-LDH, while bilayered arrangements for Zn2Al-LDH. Results showed that the obtained TCAS-LDH composites were highly selective and efficient for the removal of Cu2 + and Pb2 +. The adsorption of Pb2 + and Cu2 + reached equilibrium quickly at about 120 min and followed the pseudo-second-order model. The equilibrium adsorption isotherm data well fitted the Langmuir model. With the increasing concentration for Pb2 + or Cu2 + from 5 ppm to 200 ppm, the maximum absorption capacity of Mg2Al-TCAS-LDH and Zn2Al-TCAS-LDH composite toward Pb2 + are ∼ 205 mg/g and 188.1 mg/g, and that toward Cu2 + are ∼ 125 mg/g and 103.8 mg/g, respectively. The TCAS-LDHs composites are potential remedy for Cu2 + or Pb2 + in contaminated water.