Qiaoling Xie,Tao Lin,Fuming Chen,Dandan Wang,Bo Yang
Sulphur-containing chitosan, a water-soluble derivative of chitosan, was synthesized by using chitosan and other reagents. This sulphur-containing chitosan was combined with chitosan to recover ultra-trace palladium in HCl medium. The effects of the chelating dosages, pH, chelating precipitation rate, initial Pd concentration and coexisting cations were systematically investigated via chelating precipitation experiments. Under the optimized conditions, greater than 95% of palladium was recovered from the HCl medium, with pH ranging from 2 to 5.5 and proper dosages of chitosan and sulphur-containing chitosan, which were related to the concentration of Pd(II) ions. In addition, the presence of coexisting cations (Cu 2+ , Ni 2+ , Fe 2+ , and Sn 2+ ) had no effect on the recovery rate of palladium. The recovery mechanism of palladium by chitosan and sulphur-containing chitosan was studied via molecular weight analyses, elemental analyses, FT-IR analyses and XPS analyses. The proposed chelating precipitation method was successfully applied to the recovery of ultra-trace palladium in HCl medium.
The inhibition effect of 2-(2-Hydroxyphenyl)benzothiazole (HBT), a newly synthesized benzothiazole derivative, on mild steel in 1 M HCl medium has been investigated by utilizing weight loss measurements, electrochemical methods and morphology characterization. The results indicate that HBT exhibited a superior corrosion inhibition efficiency, which reached approximately 95% with the addition of 0.07 mM HBT. Electrochemical tests illustrate that HBT is a mixed-type inhibitor. According to the Langmuir adsorption isotherm, the thermodynamic and kinetic parameters of the adsorption process complied with a physical-adsorption mechanism. Furthermore, computational calculations based on density functional theory reveal the relation between the electronic properties and the inhibition efficiency. In combination with the value of pKa , the protonic form of HBT in corrosive medium was predicted.
Yangyang Wang,Xiaoxia Liu,Annie Yang,Ping Lv,Lixin Zhang,Yongnian Li,Yanzhao Yang
Selective recovery of gold and platinum from secondary resources is of great significance under the crisis of resource shortage. Hence, the optimal extractant 1-(2-(dimethylamino) ethyl)-4-methyl-piperazin bis(trifluoromethylsulfonyl)imide ([C 6 -Et-TMEDA-PIP][Tf 2 N] 2 ) was synthesized and screened out from five piperazine-based ionic liquids (ILs) to construct an IL-water system for Au(III) and Pt(IV) extraction. ILs have high hydrophobicity and low viscosity at room temperature, which can be used as both extractant and hydrophobic phase. The effects of IL dosage, metal concentration and acidity on the extraction efficiency were investigated. Under the optimal conditions, the extraction efficiency of 98.5% (Au(III)) and 97.5% (Pt(IV)) can be achieved. The anion exchange mechanism was verified through the combination of Ultraviolet visible spectroscopy (UV–vis), Nuclear magnetic spectra (NMR) and quantum chemical calculations. Besides that, the two-factor optimization of the extractant dosage and HCl concentration was carried out by Response surface methodology (RSM), and the effective separation of Au(III) and Pt(IV) was successfully achieved. Au(III)/ Pt(IV) was extracted into the IL phase as [Et-TMEDA-PIP + ][AuCl 4 - ] and can easily be stripped by reduction to Au(0)/Pt(Ⅱ) with H 2 C 2 O 4 /CS(NH 2 ) 2 -HCl, and each extraction ability maintained after 5 turns of extraction cycle experiments. Since the excellent behaviors showed in the multi-metal selective extraction and cycle experiments, the [C 6 -Et-TMEDA-PIP][Tf 2 N] 2 was regarded as the most potential system for Au(III) and Pt(IV) recovery from HCI medium.
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