A novel surfactant, N,N-diethyl-N′-cyclohexylthiourea: Synthesis, flotation and adsorption on chalcopyrite

In this paper, a novel surfactant, N,N-diethyl-N′-cyclohexylthiourea (DECHTU) was synthesized and first introduced as a collector for chalcopyrite flotation. The micro-flotation results demonstrated chalcopyrite with adsorbed DECHTU exhibited good hydrophobicity and was effectively concentrated by nitrogen bubbles under pH 4–8. The adsorption of DECHTU onto chalcopyrite surfaces was fitted well by the pseudo-second-order model and Langmuir isotherm, and was a spontaneously exothermic chemisorption process. The adsorption enthalpy change, entropy change and free energy change were ΔH = −31.10 kJ mol−1, ΔS = −6.32 J mol−1 and ΔG (298 K) = −29.41 kJ mol−1, respectively. The activation energy of the adsorption process was 17.39 kJ mol−1. The zeta potential results implied that DECHTU adsorbed onto chalcopyrite surfaces as its anionic species with the release of H+ ion of NH–C(S)–N group into aqueous solutions. The XPS spectra confirmed that there existed Cu(I)–DECHTU surface complexes on chalcopyrite surface by bonding of copper atom with the sulfur atom of DECHTU, accompanying with the reduction of cupric to cuprous.