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1
Content available Insights into the depression effect and adsorption mechanism of HACC on chalcopyrite surface in Cu-Mo flotation separation
100%
Li M. , Zhang P. , Gao X. , Huang L.
Physicochemical Problems of Mineral Processing
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2023
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tom Vol. 59, iss. 6
art. no. 172481
EN
In this study, hydroxypropyltrimethyl ammonium chloride chitosan (HACC) was first introduced as a depressant during separating chalcopyrite from molybdenite (Cu-Mo). The selective effects of HACC on the separation of Cu-Mo were conducted by single-mineral flotation experiments. The findings from this study revealed that HACC helped separate Cu and Mo efficiently at pH 6 with 8 mg/dm3 of HACC, resulting in 76.22% and 5.38% of Mo and Cu flotation recovery, respectively. The adsorption mechanism of HACC was investigated via zeta potential, adsorption density, and contact angle measurement along with FT-IR and XPS analyses. The contact angle and adsorption density measurements offer indisputable proof that HACC can adsorb on the surface of chalcopyrite. Furthermore, FT-IR and XPS analyses confirm that N atoms in quaternary ammonium groups of HACC interact with Cu sites on the surface of chalcopyrite. The findings also suggest that HACC adsorbs on the surface without significantly impacting molybdenite. All these results confirm that HACC can be an effective chalcopyrite depressant.
2
Content available remote Complex-valued distribution entropy and its application for seizure detection
100%
Zhang T. , Chen W. , Li M.
Biocybernetics and Biomedical Engineering
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2020
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tom Vol. 40, no. 1
306--323
EN
Embedding entropies are powerful indicators in quantifying the complexity of signal, but most of them are only applicable for real-valued signal and the phase information is ignored if the analyzed signal is complex-valued. To assess the complexity of complex-valued signal, a new entropy called complex-valued distribution entropy (CVDistEn) was first proposed in this study. Two rules, namely equal width criterion and equal area criterion, were employed to demarcate the complex-valued space and two kinds of CVDistEn, i.e., CVDistEn1 and CVDistEn2 were raised. Furthermore, two novel feature extraction methods: (1) flexible analytic wavelet transform (FAWT)-based CVDistEn1 and logarithmic energy (LE) (FAWTC1L), (2) FAWT-based CVDistEn2 and LE (FAWTC2L) were subsequently put forward to characterize the interictal and ictal EEGs. Fuzzy k-nearest neighbors (FKNN) classifier was finally employed to classify these two types of EEGs automatically. Experiment results show the fusion method of FAWTC1L and FKNN leads to the best accuracies (ACCs)/Matthews correlation coefficients (MCCs) of 99.99%/99.97% and 100%/100% for Bonn and Neurology & Sleep Centre EEG datasets, respectively, while the other fusion scheme of FAWTC2L and FKNN results in the highest ACCs/MCCs of 99.97%/99.93% and 99.94%/99.89% for the same datasets. The proposed methods outperform other entropy-related seizure detection schemes and most of state-of-the-art techniques, they provide another new way for automated seizure detection in EEG.
3
Content available The selective depression effect of sodium hexametaphosphate on the separation of chlorite and specularite
88%
Zhao F. , Yu X. , Gao X. , Li M. , Chen X.
Physicochemical Problems of Mineral Processing
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2023
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tom Vol. 59, iss. 2
art. no. 166495
EN
Flotation is the most known beneficiation method for the separation of complex and refractory iron ores. As a typical iron-containing silicates, it is difficult to separate chlorite from specularite, because of the similar surface physicochemical properties. In this study, the selective depression effect of sodium hexametaphosphate (SHMP) was conducted via the cationic micro-flotation. The surface adsorption mechanism between SHMP and the two mineral surface was explored through surface adsorption amount tests, Zeta-potential measurements, Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses. The micro-flotation results indicated that SHMP could selectively depress around 90% of chlorite, while its effect on the floatability of specularite was negligible (<20% depressing). The surface adsorption amount tests, Zeta-potential measurements analysis demonstrated that SHMP selectively adsorb on chlorite surface while on the surface of specularite is feeble. The further surface adsorption analysis via FT-IR and XPS proved that SHMP selective adsorption occurred on the chlorite surface mainly by chemisorption mainly through the chelation reaction between O in the phosphate groups of SHMP molecular and metal ions on surface of chlorite.
4
Content available Comparison of the depression effect of two thiol depressants on the separation of specularite and aegirite
88%
Li M. , Zhang C. , Gao X. , Xie X. , Tong X.
Physicochemical Problems of Mineral Processing
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2022
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tom Vol. 58, iss. 6
art. no. 152164
EN
In this work, two thiol-type reagents, thioglycolic acid (TGA) and mercaptopropionic acid (MPA), were firstly exploited and compared as aegirite depressants with sodium oleate (NaOl) as the collector to separate specularite from aegirite by flotation. The adsorption performances and mechanisms of TGA and MPA on aegirite surface were investigated via flotation experiments, Zeta potential tests, adsorption measurements, contact angle dimensions, and surface characterizations. The results of flotation indicated that TGA and MPA exhibited a considerable depression impact on the flotation of aegirite but little effect on specularite. TGA depicted more excellent depression performance than MPA, which was confirmed by HLB calculation. The results demonstrated that TGA and MPA favorably adsorbed on aegirite surface instead of specularite, hindering the subsequent adsorption of NaOl on specularite and resulting in the surface being hydrophilic. XPS results revealed that TGA and MPA were significantly adsorbed on the surface of aegirite through an interaction between the carboxyl and thiol groups of the depressants and the Si and Fe on the surface of aegirite.
5
Content available Effective separation of specularite and aegirite using chitosan as a novel depressant
88%
Li M. , Zhang P. , Gao X. , Tong X. , Xie X.
Physicochemical Problems of Mineral Processing
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2022
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tom Vol. 58, iss. 6
art. no. 151692
EN
As a typical iron-bearing silicate gangue, aegirite often associates with specularite. Due to the iron element contained in aegirite, it has similar surface properties to specularite. Flotation is by far one of the most efficient methods of processing this kind of iron ore. But the traditional depressants unable to take action in the separation of specularite and aegirite. Chitosan was used as a novel depressant to attempt to separate specularite from aegirite through microflotation tests, adsorption tests, contact angle measurements, Zeta potential measurements, and XPS analysis. The flotation results indicate that chitosan show more strong depression effect on specularite than aegirite. Zeta potential measurements, contact angle measurements and adsorption tests demonstrate that chitosan is more inclined to adsorb on the specularite surface than aegirite, which hinders the subsequent adsorption of collector sodium oleate and increases difference in hydrophobicity between the two minerals. The XPS results of specularite validate the adsorption of chitosan on specularite, and illustrate that electrons of chitosan were partially transferred to oxygen and iron atoms in specularite during the adsorption process.
6
Content available Structure-activity of chelating depressants for chalcopyrite/pyrite separation: DFT study and flotation experiment
75%
Li M. , Lian D. , Zhao F. , Tong X. , Wu C. , Gao X.
Physicochemical Problems of Mineral Processing
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2021
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tom Vol. 57, iss. 6
102--112
EN
Three types of chelating depressants were studied for chalcopyrite/pyrite separation, including S-S, S-O, and O-O types, via density functional theory calculations and microflotation. The calculation results indicate that the depressant’s chelating atoms have large coefficient and great activity according to the molecular frontier orbital (HOMO and LUMO) and the orbital coefficients. For S-S type of depressant, S atom in both keto or enol forms won’t affect their HOMO and LUMO patterns and the orbital contributions. For S-O type, the presence of N atom in the ring structure of a molecular will increase the reactivity of O-Cu while weak S-Cu. For O-O type, the electron supply capacity of benzene ring is higher than strain chain, and atom N in strain chain increased their electron supply capacity. The microflotation results basically confirmed the prediction based on the calculation. The simulation results demonstrate that the interaction of a depressant with metals and minerals are affected obviously by the spatial structure and electronic structure of an atom in its molecular.
7
Content available Application of dodecyl amine/dodium petroleum sulfonate mixed collector in quartz-feldspar flotation separation
75%
He Y. , Ren Z. , Zhu H. , Zheng R. , Li M. , Song Y. , Chen Z.
Physicochemical Problems of Mineral Processing
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2024
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tom Vol. 60, iss. 1
art. no. 185553
EN
It’s highly challenging to separate feldspar from quartz by flotation owing to their similar crystal structure and physicochemical properties. Using mixed collectors has become a promising method to improve the quartz-feldspar separation. In this study, mixed dodecyl amine (DDA) and sodium petroleum sulfonate (SPS) surfactants were used in the flotation separation of feldspar and quartz, and the adsorption mechanism of mixed collectors and depression mechanisms of two depressants were investigated through zeta potential, contact angle and Fourier transform infrared (FT-IR) spectra. When the pH reached 4.5, the separation of feldspar from quartz was more obvious. In the presence of DDA/SPS collector, the contact angle of feldspar was increased more obviously leading to enhance hydrophobicity. The infrared spectra revealed the interaction of collectors on feldspar surface involved physical and chemical adsorption, whereas the adsorption of collector on quartz was only physical interactions. The use of sodium hexametaphosphate resulted in a significantly enhanced separation performance. The weaker physical adsorption of mixed collector on quartz can be destroyed by sodium hexametaphosphate. This study is beneficial for understanding the collect mechanisms of mixed cationic-anionic surfactants on quartz and feldspar minerals, and promotes the development of advanced feldspar separation techniques.
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