Interaction between Diethyldithiocarbamate and Cu(II) on Gold in Non-Cyanide Wastewater

A surface-enhanced Raman scattering (SERS) detection method for environmental copper ions (Cu²⁺) was developed according to the vibrational spectral change of diethyldithiocarbamate (DDTC) on gold nanoparticles (AuNPs). The ultraviolet-visible (UV-Vis) absorption spectra indicated that DDTC formed a complex with Cu²⁺, showing a prominent peak at ~450 nm. We found Raman spectral changes in DDTC from ~1490 cm^-1 to ~1504 cm^-1 on AuNPs at a high concentration of Cu²⁺ above 1 μM. The other ions of Zn²⁺, Pb²⁺, Ni²⁺, NH₄⁺, Mn²⁺, Mg²⁺, K⁺, Hg²⁺, Fe²⁺, Fe³⁺, Cr³⁺, Co²⁺, Cd²⁺, and Ca²⁺ did not produce such spectral changes, even after they reacted with DDTC. The electroplating industrial wastewater samples were tested under the interference of highly concentrated ions of Fe³⁺, Ni²⁺, and Zn²⁺. The Raman spectroscopy-based quantification of Cu²⁺ ions was able to be achieved for the wastewater after treatment with alkaline chlorination, whereas the cyanide-containing water did not show any spectral changes, due to the complexation of the cyanide with the Cu²⁺ ions. A micromolar range detection limit of Cu²⁺ ions could be achieved by analyzing the Raman spectra of DDTC in the cyanide-removed water.