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Reverse flotation of collophanite at natural pH using isooctyl polyoxyethylene ether phosphate as a collector

Li Hongqiang, Zhang Wen, Chen Qian, Huang Peng, Kasomo Richard M., Zou Ze, Weng Xiaoqing, He Dongsheng, Yang Siyuan, Song Shaoxian

Physicochemical Problems of Mineral Processing

2021

Vol. 57, iss. 4

78--86

Reverse flotation of collophanite at natural pH could significantly decrease the cost of pH regulators. In this study, isooctyl polyoxyethylene ether phosphate (AEP) was tested as a new surfactant in the reverse flotation of collophanite. Micro-flotation tests were conducted, and the adsorption mechanism of the new collector was analysed using X-ray photoelectron spectroscopy (XPS) and zeta potential analyses. The results of the flotation tests demonstrated that AEP could enable dolomite to float under natural pH (pH=7.2) and showed profound selectivity towards dolomite as opposed to fluorapatite. Based on the zeta potential and XPS results, the adsorption phenomena are mainly attributed to calcium active sites on both mineral surfaces. Dolomite possesses more magnesium active sites than fluorapatite, which tend to reinforce the interaction effect between AEP and dolomite. Furthermore, when compared to CO32- ions on the dolomite surface, PO43- ions on the fluorapatite surface tend to exhibit a stronger hindrance to the adsorption of AEP on the fluorapatite surface. This is attributed to their larger volumes and more charges on their surfaces, thereby causing a floatability difference between the two minerals.

EEG with a reduced number of electrodes: Where to detect and how to improve visually, auditory and somatosensory evoked potentials

Stehlin S. A. F., Nguyen X. P., Niemz M. H.

Biocybernetics and Biomedical Engineering

2018

Vol. 38, no. 3

700--707

The measurement of evoked potentials has become a standard tool to test new hardware and software for electroencephalography (EEG). In this study, we investigate where to detect and how to improve visually, auditory and somatosensory evoked potentials with a reduced number of electrodes. We measured a total of 50 evoked potentials in healthy subjects, and we were able to detect visually, auditory and somatosensory evoked potentials with just three electrodes. We also investigated where to measure a combination of visually, auditory and somatosensory evoked potentials and found the best positions to be Oz, O1, O2, TP9 and TP10. In the second part of this study, we analyzed how the evoked potentials depend on the segmentation frequency selected to superpose EEG responses. We found that the detection of visually evoked potentials requires the segmentation frequency to match the stimulus frequency with an accuracy of at least 99.92 percent. The detection of auditory evoked potentials and somatosensory evoked potentials requires a matching of at least 99.95 percent. Therefore, a correct matching of the segmentation frequency with the stimulation frequency is the primary key to improving the quality of evoked potentials.