Using density functional methods,some properties were studied such as the energies and compositions of frontier molecular orbitals and the atomic charges,which are related to the reactive behavior of thioureas containing different N-substituent groupings.The calculation results indicate that the N-substituent groupings have significant effect on the flotation performance of thiourea collectors.The order of electron-donating ability is N-propyl-N'-benzyl-thiourea(PBZYTU)>N-propyl-N'-ethyl-thiourea (PETU)>N-propyl-N'-allyl-thiourea(PALTU)>>N-propyl-N'-acetyl-thiourea(PACTU)>N-propyl-N'-ethoxycarbonyl-thiourea (PECTU)>N-propyl-N'-benzoyl-thiourea(PBZOYTU),and the order of feedback-electron-accepting ability is PBZOYTU> PACTU>PECTU>>PALTU>PETU>PBZYTU.This implies that PBZOYTU,PACTU or PECTU can react with copper atoms having(t2g) 6 (eg) 3Cu(II)or t 6e 4Cu(I)configuration on the surfaces of copper sulfide minerals through normal covalent bond and back donation covalent bond,and exhibit excellently collecting performance for copper sulfide minerals.These are consistent with the experimental data reported in the literatures.
A novel alkoxycarbonyl thiourea resin(ATR)was synthesized by monomer polymerization of oxydiethane-2,1-diyl dicarbonisothiocyanatidate and polyethylene polyamine,and characterized by FT-IR.The adsorption properties of ATR were investigated by batch test.The adsorption capacities for Au(Ⅲ),Ag(Ⅰ),Cu(Ⅱ),Zn(Ⅱ),Fe(Ⅲ),Ca(Ⅱ)and Mg(Ⅱ)are 4.65,4.40,0.40,0.90,0.86,0.0080 and 0.016 mmol/g,respectively,when the adsorption condition is as follows:contact time 24 h,temperature 30℃,initial concentration of Au(Ⅲ)5.08 mmol/L and that of other metals 0.10 mol/L,and concentration of acid 1.0 mol/L.The adsorption capacity for Au(Ⅲ)increases with the increase of contact time,temperature and initial concentration of Au(Ⅲ).The capacity after five adsorption-desorption cycles remains 90%that of the first time,and the separation factors of ATR for binary metal ion solutions are larger than 995,indicating that ATR is of good regeneration property and selectivity.XPS results show that the functional atoms of ATR supply electrons for Au and coordinate with Au during the adsorption.
Several 1,4-benzenedicarbonyl thiourea resins (BTR) were synthesized through interfacial polymerization between 1,4-benzenedicarbonyl diisothiocyanate and polyamine. Their structures were confirmed by FT-IR. The adsorption properties (including the effect of adsorption time,pH,initial concentrations and temperature) of BTR-1,BTR-2 and BTR-3 for Ag(I) were investigated by batch tests. The results show that the adsorption equilibria of BTR-1,BTR-2,BTR-3 for Ag(I) are achieved after about 10 h. Their equilibrium adsorption capacities are 7.11,6.75 and 6.23,respectively,and the adsorption process accords with G. E. Boyd equation and Langmuir adsorption isotherm as well. The adsorption capacities increase with the increase of pH (the highest uptake values are observed at pH being about 6-7). The thermodynamic parameters of BTR-1 were calculated. The results show that-HΘ and-SΘ are 6 958.8 J/mol and 64.28 J/(mol-K),respectively,and-GΘ at 20,30,40 and 50 °C are-11.79,-12.52,-13.16 and-13.8 kJ/mol,respectively. The silver-loaded resins can be quantitatively eluted by a solution containing 6% thiourea in 1 mol/L HNO3.
