Kejia Ning

Low-rank ultrafine flotation clean coal typically yields filter cake moisture above 20% due to abundant oxygen-containing functional groups and strong surface hydrophilicity. Conventional polyacrylamide (PAM) flocculants are hydrophilic and improve dewatering only by altering cake porosity, not by reducing particle surface hydrophilicity, so they remove little adsorbed water. In this study, hydrophobically modified anionic polyacrylamides (HMAPAM) were synthesized by grafting lauryl acrylate onto APAM. FTIR, ¹H NMR, XPS, and SEM confirmed the grafting and progressive enrichment of hydrophobic alkyl chains on the surface. Moderate hydrophobic modification markedly improved solid–liquid separation. HMAPAM-D (APAM/LA = 4.5:0.5) achieved a settling velocity of 0.817 cm/s at 9 mg/L, 50.2% higher than APAM, and reduced filter cake moisture to 16.64% at 1 mg/L under 0.6 MPa versus 19.39% for unmodified APAM. Excessive modification (HMAPAM-E, 4:1) promoted intramolecular self-association, producing heterogeneous flocs and higher filtration resistance that degraded dewatering efficiency. The performance gain stems from hydrophobic association combined with adsorption bridging. These results clarify how hydrophobic group content controls flocculation and dewatering, informing the design of better flocculants for this type of coal slurry.

This systematic study was conducted on the separation of yttrium (Y) and erbium (Er) from a chloride medium using a mixed extractant system composed of [N1444][P507] and TRPO (trialkylphosphine oxide) in kerosene. This investigation focused on the effects of various extractants, extraction systems, the initial acidity of the aqueous phase, and the phase contact time on the extraction efficiencies of Y and Er. This study showed that using the combination of [N1444][P507] and TRPO notably increased the extraction performance and enhanced the separation factor between Y and Er, outperforming the individual use of P507 or [N1444][P507] under identical conditions. The extraction efficiencies for Y and Er reached 88.4% and 93.3%, respectively, with a separation factor (Er/Y) of 1.84, highlighting the system’s effectiveness in selectively isolating rare earth elements. Optimal stripping conditions were obtained using 0.1 mol/L of HCl, resulting in a successful recovery of 93.1% of Y³⁺ and 78.9% of Er³⁺ from the organic phase. The extraction mechanism involved both ion exchange and ion association. The enthalpy changes (ΔH) associated with the extraction of Y³⁺ (−2.5 kJ·mol⁻¹) and Er³⁺ (4.6 KJ·mol⁻¹) demonstrate that the extraction processes are exothermic, reflecting the thermodynamic differences between the two ions.

The evaluation of flotation reagents performs an important role in the selection and green application of reagents. The green indexes and effect indexes of flotation collectors were selected by data literature method, system analysis method, mathematical model method, and qualitative and quantitative analysis method, and the green evaluation system of flotation collectors, flotation effect evaluation system, and comprehensive evaluation system of flotation collectors were established. The normalization method and expert evaluation methods were adopted to obtain the grade classification of quantitative and qualitative indicators, respectively. The analytic hierarchy process (AHP) was used to determine the weight of secondary indicators and tertiary indicators of the evaluation system and the weight of indicators at a lower level. Applying the fuzzy comprehensive evaluation (FCE), the trapezoidal function is selected to determine the index affiliation, the index system score is calculated according to the weighted average principle, and finally, the established evaluation system is applied in an example. The example application shows that the comprehensive evaluation system of flotation collectors can make a comprehensive evaluation of collectors from the aspects of the greenness of reagent, flotation effect, and cost, and it has a strong target and practicality for collectors evaluation. The establishment of the system has a guiding significance for the selection and use of flotation collectors.