Recovery of copper from a wastewater for preparation of Cu@C nanoparticles

Copper in the chemical mechanical polishing (CMP) wastewater has been effectively chelated with starch at the atomic ratios of carbon (in starch) to Cu (in wastewater) of 3-42. By carbonization of the Cu²⁺-starch complexes at 623 K for 30 min, nanosize-controllable metallic copper (Cu) embedded in the carbon shells (thickness = 3-5 nm) (Cu@C) can be formed. The carbon shells consisted of mainly diamond and graphite observed by Raman can prevent the nanosize core Cu from being oxidized and aggregated. Notably, by manipulating the C/Cu ratios, nanosize Cu ranging from 6 to 40 nm can be obtained.