紫外光谱法研究黄药在黄铜矿表面的吸附热力学与动力学

doi:10.3964/j.issn.1000-0593(2019)10-3172-07

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Abstract Spectrum scanning was conducted to characterize xanthate solution by Ultraviolet spectrophotometry. Two strong absorption peaks at the wavelength of 226.5 and 300 nm could be observed, respectively. And the absorption peak at 300 nm was stronger than that at 226.5 nm. Then, the standard curve method was used to measure concentration of the standard samples with different concentrations, and the data set was fitted linearly. It was shown that linear correlation was good at both wavelengths of 226.5 and 300 nm, and better correlation could be found at 300 nm. Therefore, high concentration xanthate solution could be measured at 226.5 nm, whereas low concentration xanthate solution could be measured at 300 nm. Afterwards, quantitative analysis of xanthate solution at different concentrations was carried out at 300 nm. The results showed that either absorbance was at maximum of 1.672 or minimum of 0.032, the linear correlation of standard curve of xanthate solution still remained good. Correlation coefficient decreased as absorbance increased continuously. It should be noted that concentration of xanthate needed to be limited less than 20 mg·L^-1 while conducting quantitative analysis. In addition, concentration of xanthate solution was measured at 300 nm under different PH of xanthate solution. It was found that at pH 3, absorbance decreased and xanthate began to decompose. When pH reached 2, absorbance became 0 and xanthate completely finished decomposition. High adsorption performance of xanthate by chalcopyrite could be explored at pH range of 5~10, and highest performance occurred at pH 9. Furthermore, adsorption capacity of xanthate by chalcopyrite surface was also measured at 300 nm. The experimental data were respectively fitted by different equation models, i. e., Freundlich and Langmuir isothermal adsorption equation model, pseudo-first-order and pseudo-second-order kinetic equation model. Sequentially, adsorption kinetics and thermodynamics of xanthate by chalcopyrite surface were studied. The results indicated that in the range of 288 to 303 K, temperature change exerted little effect on the adsorption capacity. The adsorption isotherm of xanthate by chalcopyrite surface was more consistent with Langmuir isothermal model. The actual equilibrium adsorption capacity of xanthate on chalcopyrite Q_e was less than or close to theoretical monolayer saturated adsorption capacity, and Q_m values were very close to the experimental values, indicating that adsorption of xanthate by chalcopyrite surface was dominated by monolayer chemical adsorption. With the increase of temperature, the adsorption capacity increased, meaning that temperature increment was beneficial to promote adsorption. The adsorption of xanthate on chalcopyrite was predicted to be exothermic but only small increasing extent of adsorption capacity could be observed. Thus, it would be reflected that the adsorption of xanthate on chalcopyrite is less affected by temperature. The adsorption process was spontaneous, with entropy increase and heat adsorption. The thermodynamic parameters could be calculated by Van’t Hoff equation, namely, adsorption enthalpy change ΔH=48.703 41 kJ·mol^-1, entropy change ΔS=219.403 88 J·(mol·K)^-1, and the adsorption free energy change ΔG=-16.054 93 kJ·mol^-1. Therefore, the adsorption process could be defined as chemical adsorption. Adsorption of xanthate on chalcopyrite was more consistent with pseudo-second-order kinetic equation model. Q_t value increased with temperature elevation, and the change range was very small. Consequently, it revealed that adsorption process of xanthate by chalcopyrite surface was endothermic, however, it was affected by temperature to a small extent. This was in agreement with the conclusion of thermodynamic analysis, and the value of Q_e obtained by fitting was very close to experimental value.

Key words：Adsorption; Thermodynamics; Kinetics; Xanthate; Chalcopyrite; Ultraviolet-Visible absorption spectroscopy

Received: 2018-08-16 Accepted: 2019-01-05

ZTFLH:

TD913

Corresponding Authors: HE Ting-shu E-mail: hetingshu@xauat.edu.cn

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2019)10-3172-07 OR https://www.gpxygpfx.com/EN/Y2019/V39/I10/3172

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