Amide group enhanced self-assembly and adsorption of dicarboxylic amino acid surfactants on a rhodochrosite surface through intermolecular weak interaction

Chen Y., Zhang P., Jiao L., Chen G., Yang Y., Chong H., Lin M.

• BCN was functionalized by Phenanthroline diamide with high density. • Functionalized BCN exhibited ultrahigh adsorption capacity for U(VI). • Functionalized BCN showed excellent selectivity for U(VI) from lanthanides. • Adsorption mechanism was explored by combining two-site model and DFT calculations. Separating and recovering uranium (U(VI)) efficiently from lanthanides is crucial for mitigating the radioactive hazard generated by hydrometallurgical residual solutions of lanthanide minerals and ensuring the long-term sustainability of uranium resources. The present work exploited phenanthroline diamide functionalized porous carbon doped boron nitride (BCN-DAPhen) as an adsorbent, which displayed outstanding adsorption performance for the separation of U(VI) from lanthanides. The results of batch adsorption tests indicated that BCN-DAPhen exhibited rapid adsorption kinetics and the adsorption process achieved equilibrium within 10 min. BCN-DAPhen also performed ultra-high maximum adsorption capacity that was calculated to be 2050.8 mg g −1 by fitting with the two-site Langmuir model. Theoretical calculation and experimental results of adsorption were combined to illustrate the adsorption mechanism as well, the results showed that two structures of DAPhen groups on BCN performed discrepant adsorption properties for U(VI). BCN-DAPhen retained excellent adsorption ability owing to the strong affinity of DAPhen groups with U(VI) even in the solution with high concentration of salt and acid. The selectivity coefficients of U(VI) toward various lanthanides were beyond 192.5 at a high nitric acid concentration of 5 mol L −1 . This study suggested a general technique for the functionalization of porous BCN, which is expected to be useful in the treatment of residual solution in lanthanides hydrometallurgy.

Wang D., Wang D., Deng C., Wang K., Tan X., Liu Q.

• Tannic acid-PEO associative complexes controlled the PEO flocculation of quartz. • Tannic acid changed the optimum quartz flocculation pH from acidic to alkaline by PEO. • Tannic acid significantly increased the quartz floc strength induced by PEO. • Tannic acid allowed broken PEO-quartz flocs to re-flocculate under cycled shear conditions. • Complexation between tannic acid and PEO was pH-dependent based on hydrogen bonding. The flocculation behaviors of quartz using a dual polymer system containing tannic acid (TAN) and poly(ethylene oxide) (PEO) were investigated in this study, with dynamic floc size monitoring by the in-situ focused beam reflectance measurement technique. Variables of concern and their influence on the flocculation process were investigated from both physicochemical and hydrodynamic aspects, including solution pH, TAN/PEO ratio, and shear intensity. Floc structure was characterized using confocal scanning microscopy in suspension as well as freeze-drying-SEM imaging method. It was found that prior addition of TAN significantly increased the flocculation efficiency of quartz by PEO at neutral and alkaline pH, but not in acidic solutions despite that PEO induced the largest floc size at pH 3.1 when used alone. An optimal TAN/PEO ratio of 2 was observed for the best flocculation of quartz under the experimental conditions. Additionally, tannic acid could increase the strength of flocs formed by PEO, and the shear resistance of the flocs increased with increasing TAN/PEO ratio. The dual polymer system also contributed to the re-flocculation of quartz under cycled shear conditions, a phenomenon that was not observed when PEO was used alone. Zeta potential and adsorption density measurements confirmed that the pathway of the dual polymer flocculation was via the initial formation of TAN-PEO associative complexes in solution and then bridging of quartz by the associative complexes. The TAN-PEO associative complexes showed different structures and configurations at different pH, in line with a change in hydrogen bonding, which in turn affected floc structures and properties under turbulent conditions. This study helps to understand the improved flocculation, shear resistance and re-flocculation of fine particles induced by dual polymer system.

Li Y., Cheng G., Zhang M., Cao Y., Von Lau E.

Pyrite is separated from other minerals mainly by flotation. However, the hydrophilicity of pyrite is affected by many factors, causing it to easily enter the concentrate and consequently reduce the quality of concentrate. Highly efficient pyrite depressants can be selectively adsorbed on the surface of pyrite to improve its hydrophilicity, thereby increasing the flotation separation efficiency. Understanding the fundamental inhibition mechanism of depressants on pyrite is a prerequisite to improve the flotation desulfurization efficiency. The inhibition ability and mechanism of different types of pyrite depressants are reviewed in this manuscript. In recent years, molecular simulation has increasingly become a powerful tool to study the interaction between reagents and minerals, shedding new light on the adsorption mechanisms of reagents on mineral surfaces at the atomic and electronic levels. The properties of sulfide mineral and flotation reagents as well as the microscopic adsorption mechanistic studies of reagents on mineral surfaces based on quantum chemistry and molecular simulation are also reviewed.

Tang X., Chen Y.

Pyrrhotite is an associated mineral that exists widely in sulfide ore. The presence of pyrrhotite will affect the recovery of platinum group minerals. Therefore, researchers have paid increasing attention to the flotation separation of pyrrhotite. Pyrrhotite superstructures owning different Fe/S ratios results in various crystal structures, corresponding to different physical, chemical and electronic properties, and consequently different flotation behavior. In the present paper, a comprehensive review is conducted to discuss the influence of crystal structures on the natural floatability, mineral-reagent interaction, surface oxidation and flotation electrochemistry of pyrrhotite. The selective flotation process of pyrrhotite from its associated minerals is also reviewed in this paper. It is hoped that this review can summarize the newly published research results combined with some representative results from the past, to provide a theoretical basis for the study of the flotation mechanism of pyrrhotite and provide a new direction for future research on pyrrhotite.

Sun H., Wang S., Fei L., Cao Z., Zhong H., Ma X.

• DPA is a promising selective flotation collector for rhodochrosite . • DPA can separate rhodochrosite from quartz and calcite without depressant. • DPA owns high selectivity because it has multiple active sites on mineral surfaces. • DPA can chemically adsorb on rhodochrosite surface. • DPA molecules formed two distinct adsorption geometries on rhodochrosite surfaces. Rhodochrosite is often associated with calcium- and silicon-bearing minerals, resulting in a low grade, and it is difficult to achieve efficient flotation separation with conventional collectors. A novel collector, 2-decanoylamino-pentanedioic acid (DPA), was synthesized by constructing an amide group and double-branched carboxylic acid molecular structure to selectively separate rhodochrosite against quartz and calcite. The flotation results demonstrated that, compared with sodium oleate, DPA exhibited superior collecting performance and enabled the separation of rhodochrosite from quartz and calcite under neutral pH, with no addition of a foaming agent or activator; thus, DPA is regarded as an appropriate flotation collector for rhodochrosite. Analysis of the contact angles, Fourier transform infrared spectroscopy (FTIR), zeta potential and X-ray photoelectron spectroscopy (XPS) results showed that DPA chemically adsorbed on the surface of rhodochrosite, forming 8-membered ring or two 4-membered ring structures. However, no significant interaction was detected on the surface of quartz and calcite, providing evidence for the flotation separation of rhodochrosite from calcite and quartz. This research provides a potential collector for efficient utilization of rhodochrosite.

Hassanzadeh A., Safari M., Hoang D.H., Khoshdast H., Albijanic B., Kowalczuk P.B.

• Froth flotation of fine and coarse particles is studied, focusing on cell designs. • Generating micro-bubbles, intensive turbulence, and high gas hold-up are advantages of intensified cells. • Scaling up/down procedures for the intensified cells are found unclear. • Positioning the optimum location of discussed cells in flotation circuits is found challenging. After more than a century applying flotation to the mining industry, two completely different strategies have been introduced for processing purposes. One is the classical approach viz. grinding ores to a certain extent (fine particles) and floating them via conventional mechanical and pneumatic cells i.e., Jameson, Imhoflot™ and Reflux™. This strategy continues because mines face declining cut-off grades, complex and poly-mineralized ores, and they are required to achieve an acceptable degree of mineral liberation. The other school of thought deals with coarse particle processes mainly owing to the low energy requirements, that includes SkimAir® flash, fluidized bed and HydroFloat™ cells. There is no study in the literature to comparatively present the recent developments of flotation apparatuses versus the conventional mechanical cells. To cover this knowledge gap in the literature, the present paper endeavors to critically evaluate these concepts from several points of view, including existing technological advancements, water and energy usage, kinetics, and circuit design. A brief introduction of advanced technologies, along with their applications is presented. The data from literature and case studies showed that the Jameson, Imhoflot™ and recently developed Reflux™ flotation cells can be very effective for recovering fine particles owing to their specific hydrodynamic designs, intensive energy dissipation rate and generation of micron-sized bubbles (100–700 µm). Very low (less than a few minutes) mean particle residence time, high gas-hold up (ca. 50–70 %), no agitation and high efficiency of particle-bubble collision were identified as their main advantages compared to traditional mechanical flotation cells. In addition to their common applications in cleaner stage, these cells were used in pre-flotation and scalping (producing final concentrate from the rougher feed) duties. Their main challenges were recognized as relatively unclear procedure on their scale up/down, optimization and simulation. The HydroFloat™ cell was indicated as a promising technology for recovering coarse particle fraction sizes by taking advantage of the fluidized-bed concept with plug-flow dispersion regime, high particle residence time, and limited cell turbulence. We finally concluded that fine particle flotation may remain as the main focus of re-processing tailings dams, while coarse particle treatment should be the focus of this century to reduce total energy consumptions.

Shen Z., Zhang Q.

Efficient separation of fine-disseminated rhodochrosite is a challenge in the purification of manganese carbonate ore and a key to reduce the discharge of electrolytic manganese slag. The agglomeration behavior of the fine particles is of importance for flotation separation. In this study, we investigated the agglomeration behavior and aggregate properties of rhodochrosite fines co-induced by oleic acid (OA) and shearing using particle size and structure analysis, surface properties measurement, extended DLVO (EDLVO) theoretical calculation and shear fracture model analysis. The results showed that rhodochrosite fines agglomerates obviously with the increasing OA concentration and pH value, and the average particle size reaches the maximum at the initial OA concentration of 1 × 10-3 mol/L and pH of 6. The monolayer physical and chemical saturation adsorption of OA cause stronger hydrophobicity of rhodochrosite. Meanwhile, the hydrophobic attractive force between particles is stronger than electrostatic repulsive force, resulting in hydrophobic agglomeration. The moderate stirring rate is conducive to forming larger-sized and denser agglomerates with the critical rate of 500 rpm. However, intensive shearing will cause significant damage to the formed agglomerates. Besides, the volume concentrations of 10–30 μm and 30–45 μm particles increased with the increase of stirring rate after breakage and with a lower value of γ’ than 0.5, suggesting that the agglomerates breakage is mainly controlled by large-scale fragmentation mechanism. Interestingly, as recovering shearing from the higher rate to the initial rate, a secondary agglomeration is achieved by the regrowth of core (30–45 μm particles) and attach of branches and coatings (some

Zhou L., Han Y., Li W., Zhu Y.

• Quantitatively characterization and regulatory of ultrafine specular hematite floc structure by image analysis. • Polymer-bridging flocculation performance of the ultrafine specular hematite. • High gradient magnetic separation behavior of ultrafine specular hematite flocs. • Interaction energy calculation between mineral particles based on EDLVO theory. • Interaction mechanism between starches and minerals in specular hematite ore. Flocculation magnetic separation process is one of the efficient and economical methods to recover fine weakly magnetic iron ore. It is well known that the structural characteristics of mineral flocculants have a significant effect on the flocculation magnetic separation process. Therefore, it is of great practical significance to adjust the structural characteristics and particle size of iron flocs to suit the high-gradient magnetic separation process. In this study, the effect of molecular structure and dosage of the reagents, pulp pH and stirring intensity on the flocculation performance and magnetic separation behavior of ultrafine specular hematite ore were studied by optical microscope observations along with image analysis and floc-magnetic separation experiments, respectively. Besides, the relationship among agglomeration factors, flocculation structure and separation index was established. The interaction mechanism between different starches and minerals was studied by electron scanning microscope (SEM) observation, particle interaction energy calculation, Zeta potential and infrared spectrometric measurements. The results showed that the flocs size gradually increased with the increase of molecular weight, amylopectin content and dosage of the reagent. An appropriate agitation intensity will be helpful to the aggregation of mineral particles, and the new flocculation will be destroyed as the stirring intensity is excessive. Compared with no additives in the separation process, the flocculation-magnetic separation process could increase the recovery rate by 1.5–2.0 percentage points on average when the flocs size was about 23 μm. With the increase of amylopectin content and molecular weight, the separation index increased gradually. Compared with tapioca starch, using carboxymethyl tapioca starch as flocculent, the iron grade of concentrate was increased by 1–2 percentage points. The microscopic morphology of the mineral particles showed that the agglomeration of ultrafine specular hematite particles was formed by the polymer bridging of starch in the pulp. The calculation results of interaction energy between particles showed that there was repulsive force between specular hematite and quartz particles due to the existence of repulsive energy of hydration, so the specular hematite and quartz particles were dispersed in the pulp. Zeta potential and FTIR test results showed that these starches can be selectively adsorbed on the specular hematite surface through electrostatic interaction and hydrogen bonding, while there was no obvious adsorption existed between starches and quartz.

Chen Y., Zhang W., Liang C., Zheng D., Wang Y., Li X., Shi Y., Wang F., Dong W., Yang Z.

• The secondary structure of peptide can be fine tuned by methods for self-assembly. • The nanomedicine substantially improves the binding affinity to NRP-1 protein. • The optimized nanomedicine shows good anti-angiogenesis and anti-tumor effects. Currently, combination therapy has become a popular research topic in cancer therapy. However, the outcome of the current combination therapy strategy does not satisfy the demand for clinical applications because of factors such as their overlapping toxicities, poor drug payload, and inevitable therapy resistance. Supramolecular self-assembly of peptides holds great potential for solving relevant problems and achieving superior therapeutic effects. In this study, we aimed to propose supramolecular self-assemblies based on a combination therapy strategy, consisting of a heptapeptide A7R for the inhibition of angiogenesis, the chemotherapeutic drug HCPT for treating numerous tumors with high efficacy, and an efficient self-assembling molecular FFY to improve drug loading and cell permeability. We regulated the secondary structure of nanomaterials by optimizing the pathways of self-assembly and significantly improved the affinity of A7R peptide to NRP-1. Endothelial tube formation in Matrigel and a tumor mouse model ( in vivo ) were then performed to demonstrate the superior antitumor effects of our supramolecular self-assemblies both in vitro and in vivo . In summary, this work not only provides a promising platform for the development of effective combination therapy, but also offers a useful strategy to prepare self-assembled nanomaterials with optimized performance.

Wang Z., Liu N., Zou D.

• Fine pyrite (−26 μm) flotation was improved by combined use of two reagents. • Particle size of fine pyrite was flocculated to a value suitable for flotation. • Amidation of two reagents caused hydrophobic and flocculation of fine pyrite. • Reticulated polymeric hydrophobic product may generate on the surface. Hydrophobic flocculation is one of the effective method to solve the fine flotation. In this paper the hydrophobization and flotation performance of coco-alcyl-amine-acetate (C-1) on fine pyrite (−26 μm) was improved by ethylenediamine-N, N'-bis (2-hydroxyphenyl) acetic acid (C-2) and the corresponding interaction mechanism was discussed. Turbidity and microscope measurements show that fine pyrite can be better flocculated to an easily floated size using mixed C-1/C-2 (1:1) reagent scheme pH 8.5. Surface micropolarity results display that the flocculation of fine pyrite using mixed C-1/C-2 is mainly through the hydrophobization of it by reagent adsorption. C-2 and C-1 promoting the adsorption of each other could be implied by the significantly change in the surface roughness of pyrite. FTIR results show the amidation between the –NH– in pre-adsorbed C-1 with the –COO – of C-2. Hydrophobic and bridging flocculation are the primary and secondary factors of the bigger floc size. Considering the possibility of the amidation between –NH– in C-2 and -COS - in C-1 and thus the formation of reticulated polymer, the importance of the bridging flocculation may go up, which needs further study. The better flotation recovery of fine pyrite with mixed C-1/C-2 is consistent with the detection results and deductions.

Zou S., Ma X., Wang S., Zhong H., Qin W.

In this study, the flotation of rhodochrosite fines induced by octyl hydroxamic acid (OHA) as hydrophobic agglomerates was investigated through the measurements of micro-flotation, laser diffraction, microscopy observations and zeta potential. The experimental results showed that the apparent particle size and morphology of rhodochrosite agglomerates were greatly affected by OHA concentration and stirring speed. Bigger agglomeration particle size and more regular agglomerates could be obtained at the OHA concentration of 60 mg/L, and appropriate stirring speed was required to form an optimum particle size of agglomerates for micro-flotation. The increased apparent particle size of rhodochrosite was favorable for micro-flotation recovery even though the particles were negatively charged in the presence of OHA. It's considered that OHA adsorbed on the surface of rhodochrosite through zeta potential results as well as the species distribution analysis of OHA and rhodochrosite. • Rhodochrosite agglomeration induced by OHA was investigated. • Agglomerates size was closely related to mechanical agitation. • Correlation of rhodochrosite aggregation with flotability was presented. • OHA could be well adsorbed on the surface of rhodochrosite.

Cui W., Chen J.

Flotation is a complex process that occurs in solid–liquid-gas multiphase systems, and its main factors include the minerals, separation medium, as well as various flotation reagents. The study of mineral properties and interactions with other components such as reagents and water lays the basic theoretical foundation for flotation. Density functional theory (DFT) calculations can qualitatively evaluate the exchange of matter and energy between the mineral system and the surroundings and quantitatively characterize these behaviors, which greatly expands the breadth and depth of flotation studies. This review systematically summarizes the advances of flotation research based on DFT studies, including the study of mineral crystal chemistry represented by the theory of lattice defects, mineral surface hydration such as hydrophilicity and hydrophobicity, surface regulation mechanism, and collecting mechanism based on surface adsorption theory. More significantly, it systematically elaborates different types of collectors according to their characteristics and emphatically explains the mechanism of some typical collectors in detail.

Mahmoudi Alemi F., Mohammadi S., Mousavi Dehghani S.A., Rashidi A., Hosseinpour N., Seif A.

• CNPs were synthesized for controlling asphaltene precipitation and aggregation. • FESEM and FTIR demonstrate uniform adsorption of asphaltene on surface of CNPs. • DFT modeling proves the strong hydrogen interaction between CNPs and asphaltenes. • CNPs represent biocompatible and affordable asphaltene inhibitor-dispersant. In this study, a new class of carbon nanoparticles (CNPs) is synthesized for inhibition/dispersion of asphaltene precipitation and aggregation in unstable crude oil. The microscopy and asphaltene dispersant experiments are carried out to assess the effects of CNPs on asphaltene precipitation and aggregation. Also, density functional theory is applied to describe the mechanisms of asphaltene adsorption onto the CNPs surfaces. Experimental results demonstrate postponement of asphaltene onset of precipitation from 26 to 37 vol% n-C 7 in the presence of 400 ppm of the CNPs which is ascribed to the extra high specific surface area of the CNPs. DLS analysis shows the average size of asphaltene aggregates adsorbed onto the CNPs reduces from 1730 nm in the blank oil to 255 nm in treated oil with CNPs. The results of DFT modeling demonstrate the strong hydrogen interaction between functional groups of the CNPs and active sites of asphaltene. Also, π–π interactions occur between electron cloud of aromatic rings of asphaltene and CNPs with minimum equilibrium distance of 2.94 Å. The adsorption energy for the most stable complex of asphaltene and CNPs in the gas and solvent phases are −91.22 and −107.64 kJ/mol, respectively, confirming the strong chemisorption of asphaltene over the CNPs. This research reveals that synthesized CNPs with specific features such as high surface area, potential of covering the external shell with a wide variety of functional groups, low toxicity and cost, and environment-friendly can be successfully implemented as an efficient inhibitor and/or dispersant for asphaltene handling strategies.

Liu S., Xie L., Liu G., Zhong H., Zeng H.

The two-step hetero-aggregation among chalcopyrite and malachite particles sequentially-induced by HABTC’s nonpolar and bipolar groups. • A bifunctional surfactant HABTC aggregated chalcopyrite and malachite particles. • HABTC’s hydrophobic force notably increased the “jump in” attachment distance. • To bond different minerals via HABTC’s bifunctional groups improved adhesion forces. • Hetero-aggregation was sequentially induced by HABTC’s nonpolar and bipolar groups. • Hetero-aggregation realized the carrier flotation of malachite by chalcopyrite. To promote the separation and enrichment efficiency of oxide minerals from the sulfide-oxide ores through froth flotation has become a challenging issue. In this paper, the driving role of S -[(2-hydroxyamino)-2-oxoethyl]- N,N -dibutyl-dithiocarbamate (HABTC) in facilitating the aggregation of copper sulfide and oxide minerals particles was explored through atomic force microscope (AFM) force measurements and the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory calculation. AFM imaging, contact angle measurement and surface energy computation showed that the self-assembly of HABTC on chalcopyrite and malachite improved the hydrophobicity of their surfaces and reduced their interaction free energies. AFM force measurements observed that the “jump in” attachment occurred at 8.6 ~ 12.5 nm during the approaching chalcopyrite towards malachite in HABTC solution, which was mainly attributed to the hydrophobic interaction between them. And the adhesion force between them in HABTC solution was much larger than that in OHA solution, being contributed to HABTC’s bridging role driven by its uncoordinated dithiocarbamate or hydroxamate groups to bond with the surface copper atoms of different minerals. The two-step hetero-aggregation among chalcopyrite and malachite particles sequentially-induced by HABTC’s nonpolar and bipolar groups built a carrier flotation platform where the floatability of malachite particles was significantly promoted by chalcopyrite particles with a superior hydrophobicity, resulting in an improved flotation recovery of malachite.

Zhang G., Wang H., Deng X., Yang Y., Zhang T., Wang J., Zeng H., Wang C., Deng Y.

The rising pursuit for green rechargeable energy storage devices desires novel electrode materials with cost-effective, environmental-friendly properties besides high electrochemical performance, boosting the rapid development of organic electrodes. However, the organic electrode materials in most reports can hardly be used in the real applications due to relatively poor electrochemical performance. Herein, by utilizing a smart supramolecular self-assembly between metal ions and ligands, we facilely chelate the rhodizonic acid disodium salt (RA) using ferric ions and generate a novel organic anode material (RAFe) for the first time. The strong chelation interaction between ferric ions and rhodizonic acid changes its initial structure and characteristics, enabling the obtained organic RAFe compound with outstanding electrochemical performance as anode for lithium ion batteries (LIB), which includes high reversible capacity (1283 mAh/g at 0.1A/g), excellent rate capability, long cycling stability (0.5 A/g over 300 cycles with a capacity retention of 90.76%, i.e. 0.03% decay per cycle). Even at a high mass loading of 4.0 mg/cm2, this organic anode can still deliver a capacity over 1000 mAh/g with the specific area capacity of 4.09 mAh/cm2 at 0.2 A/g, and maintains it over 92.4% after 100 cycles. Apart from offering a promising organic anode material, this work also broadens the application of metal chelation interaction based supramolecular self-assembly in energy storage territory which will inspire the preparation of other high-performance organic materials for advanced LIBs.

Holmberg K., Bilén F., Bordes R.

Huang Z., Cheng Y., Xu J., Lei C., Zhang Y., Wang B., Yuan Y., Wang W., Liu Y.

• Four crystal structures of polycyclic heterocyclic quinone are obtained. • "Hydrogen atom substitution" (HAS) method is the first method proposed to divide total weak interaction. • HAS method is successful if the substituted group has no strong electronic effect. • The energies of many weak interactions are calculated in this study. In this work, we synthesized six polycyclic heterocyclic quinones (PHQs) and one unexpected product (compound 6 ). We verified all of their structures by 1 HNMR, 13 CNMR, and HRMS and obtained four crystal structures of the seven products. At first, we compared the crystal structures with crystal structures similar to those reported in the literature and explained their differences by conjugative effect, hyperconjugative effect, and electrostatic effect. Then, we compared the crystal structure of compound 6 with the calculated structure of compound 6 . The natural bond orbital analysis showed that the calculated structure formed intramolecular hydrogen bonds, whereas the crystal structure formed intermolecular hydrogen bonds but not intramolecular hydrogen bonds. The main reason for this difference was not due to the atomic charge or the interatomic distance, but rather the energy levels of the orbitals of the lone-pair electrons. In crystal structures, the intermolecular interactions contained many weak interactions, and we used the hydrogen atom substitution (HAS) method to divide the total intermolecular interactions as several independent weak interactions and to calculate their energies. The HAS method was often successful if the substituted group did not have a strong effect on the electronic structure of the entire molecule, and we found examples in the calculations of energies of weak interactions of crystal structure of compound 6 and compound 3a . An unsuccessful example of the HAS method was the substitution of C = O group with CH 2 group to eliminate the O … H-N hydrogen bond interaction from the total interaction. According to the HAS method, our calculations showed that the strength order of the weak interactions was as follows: π-π stacking > hydrogen bond > n -π stacking > σ-π stacking. For the hydrogen bond, the strength order was as follows: C = O … H-N > C Cl … H-N > C-F … H-N. For n- π stacking interaction, the strength order was as follows: Cl-π > N -π > F -π. Finally, we selected five synthesized PHQs to test anticancer activities and some of them showed better anticancer activities than the positive control drugs.

Sun H., Wang Z., Su J., Zhang Y., Wang C., Wang H., Jiang H.

Wu X., Zhang Z., Lin H., Feng Q., Xue B., Li M., Chen Z., Lv J., Li L.

Xie Y., Ban X., Yin W., Song N., Yao J.

Wu C., Chen J., Long Q., Sun D., Qi X., Yang J., Wang Y.

Dengying O.L.

Lu Y., Huang L., Chen W.

Fatty acid surfactants, known for their cost-effectiveness and efficacy, are commonly used in the flotation process of hematite. An in-depth understanding of the role of hydrophobic groups on the performance of fatty acid surfactants can enhance and guide the utilization of surfactants for hematite flotation. Herein, four representative fatty acid surfactants with heterogeneous hydrophobic groups were selected and the influences of the hydrophobic group configuration on the adsorption behavior and flotation performance were systematically investigated by density functional theory (DFT) calculations, quantitative structure–activity relationship (QSAR) analyses, surface tension measurements, wettability tests and molecular simulations. The results of the DFT calculation and QSAR analysis reveal that logP is the primary parameter in determining the collective power of fatty acid surfactants for hematite. The results of the steric hindrance study suggest that the fatty acid with a cyclic hydrocarbon structure forms an L-shaped arrangement on mineral surface. This arrangement increases the intermolecular steric hindrance effects and reduces the coverage density. Compared to the l-shaped arrangement of fatty acids with straight hydrocarbon chains, the L-shaped arrangement possesses better selectivity towards hematite. The results of the flotation tests indicate that fatty acids with straight hydrocarbon chains possess a strong collection ability to hematite, while fatty acids with circular structures exhibit enhanced selectivity, providing experimental support for the adsorption model. This work provides a scientific approach to better understand the structure–activity relationship of surfactants in flotation, with implications for the development of effective surfactants for hematite.

Svanedal I., Eivazi A., Norgren M., Edlund H.

Chelating surfactants are amphiphilic molecules capable of forming coordination complexes with metal ions and self-assembling into organized structures. These compounds have gained significant attention in recent years due to their multifaceted applications in environmental remediation, industrial processes, and material sciences. This review provides an overview of the characterization techniques and recent advancements in the applications of chelating surfactants over the past few years. The review begins by elucidating the characterization methods employed to understand the physicochemical properties of chelating surfactants and gain insight into their complex behavior and interactions in various systems. The applications of chelating surfactants in remediation of wastewater and soil, flotation of minerals, oil recovery processes, and corrosion inhibition in metallic structures are explored. Through examination of recent fundamental research activities, innovative approaches, mechanisms of action, and advancements in the different application domains are highlighted. Lastly, some recent progress in the related field of metallosurfactants is explored, even though not all metallosurfactants are chelating.

Xie Y., Yin W., Yao J., Xue F., Liu J., Ban X.

Chlorite is often associated with hematite and tends to form microfine particles during grinding, making it challenging to recover and separate from hematite through flotation. This study innovatively applies an ester-based cationic polyacrylamide (CPAM) as a flocculant in a reverse flotation system using dodecylamine (DDA) as a collector, to flocculate and recover microfine-grained chlorite. The method achieves efficient separation between microfine chlorite and hematite. Laser particle size testing and optical microscopy show that CPAM significantly increases the apparent particle size of microfine chlorite, causing it to aggregate into flocs, while having a extremely weak effect on hematite flocculation. Further analysis using techniques like Zeta potential, contact angle measurement, Fourier-transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) reveals CPAM's stronger adsorption affinity for chlorite compared to hematite. The ester groups in CPAM selectively form hydrogen bonds with chlorite's surface H atoms, enhancing its hydrophobicity. Particle-bubble attachment angle testing confirms that the flocculated chlorite flocs exhibit better floatability and higher efficiency in collision and adhesion with bubbles. Thus, CPAM serves as an efficient flocculant for reverse flotation separation of microfine chlorite and hematite.

Zhang S., Zhang L., Zhang Y., Ren X., Sun Q., Wennersten R., Cao F., Liu Y., Hao M., Yu H.

The main aim of this study is to investigate the mechanism of the effect of the nitrogen-containing functional group of activated coke on SO2 adsorption through experiments and simulations. In this work, active coke with rich pyrrole and pyridine groups was prepared by ammonia modification. It has been found that the presence of pyrrole and pyridine groups, which can increase the surface polarity of active coke and the strength of non-covalent interactions, favors SO2 adsorption. Simulations show that the adsorption energy and non-covalent interaction strength of SO2, H2O and O2 on the surface and edge of active coke models with pyrrole group are greater than those with pyridine group, except for the adsorption of H2O on the edge of active coke. The presence of H2O reduces the adsorption capacity of SO2, mainly due to the competitive adsorption between H2O and SO2. Experimental research shows that the presence of H2O increases the content of S element on the active coke surface after adsorption. So, H2O not only promotes the adsorption of SO2, but also competes with it. Compared to O2, H2O forms stronger hydrogen bonds and dipole–dipole interactions with SO2, which can promote the adsorption of SO2.

Liu D., Wu M., Li X.

Shale gas fracturing flowback fluid (FFF) is characterized by complex composition, high generation volume, viscosity, chemical oxygen demand, and suspended solids content, which is harmful to the environment and needs to be reused after treatment. In the previous work, microbubble-enhanced flocculation can effectively treat the microfine particles in FFF by the trapping and bridging functions of microbubbles. The formation of stable bubble-particle adhesion throughout the microbubble-enhanced flocculation process is the key step to achieve efficient solid-liquid separation. In this work, the influence of particle surface interface properties, including surface hydrophobicity and roughness, on the stable adhesion was investigated. The results show that the more hydrophobic and rougher the particle surface is, the lower the three-phase contact (TPC) formation time (from 581 ms to 128 ms) and the number of collisions (from 10 to 4). The shorter TPC formation time and fewer collisions mean the faster the bubble forms a stable adhesion with the particle. The main reasons are the increase of hydrophobic gravitational force and the existence of "pinch" effect. In addition, the addition of surfactant can enhance the stability of the liquid film and weaken the deformation of the bubble, which increases the formation time of TPC. The above results provide a theoretical basis for the treatment of FFF by microbubbles-enhanced flocculation.

Zhao X., Wang Z., Liu Y., Yuan B., Song L., Penfold J., Li P., Yan Z.

Amino acid surfactants play a crucial role in many personal care products and pharmaceuticals. Their significance arises from their unique characteristics, including diverse molecular structures, low skin irritation, and excellent biodegradability. The structure of amino acid surfactants, particularly the structure of their hydrophobic chains, plays a pivotal role in determining their interfacial properties. It is proposed that the steric hindrance effect stemming from the presence of branched hydrophobic chains can exhibit a profound influence on both the interfacial adsorption behavior and the overall performance of amino acid surfactants. We synthesized a range of novel amino acid surfactants featuring varying lengths of branched chains, derived from natural terpenoid alcohols. Several characterization techniques, including surface tension measurements, dynamic light scattering, foam volume assessments, demulsification time evaluations, and contact angle measurements were used to reveal the substantial influence of branched chains and the chain length on the surfactant performance. The investigation shows how the presence of branched chains influences their interfacial properties, their propensity to form larger aggregates above the critical micelle concentration and the impact of pH on the surfactants performance. Within the examined pH range, surfactants featuring natural branched farnesol chains exhibit critical micelle concentration ranging from approximately 0.8 to 3.8 mM. Those values are significantly lower when compared to surfactants possessing similar length of linear chains. Simultaneously, the conversion of linear hydrophobic chains into branched chains enhances the foam stability promoted by the surfactants by approximately 10 %. These findings emphasize the collective impact of hydrophobic interactions and steric hindrance of the hydrophobic chains on surfactant surface packing. The distinctive interfacial behavior exhibited by branched surfactants shows great potential in establishing a theoretical foundation for formulation research in the development of highly efficient detergents and premium cosmetics.

Ouyang L., Huang Z., Wang H., He G., Yu X., Burov V.E., Poilov V.Z., Li F., Liu R., Li W., Shuai S., Zhang S., Cheng C., Fu W.

Rhodochrosite and calcite have similar physicochemical characteristics and floatability, making it difficult for conventional flotation collectors to effectively separate the two minerals. In this paper, a novel 3-tetradecylamine propyl amidoxime (TPA) collector with selective and excellent collection capability for rhodochrosite has been investigated. The micro-flotation experiments showed that the flotation performance of TPA is superior to that of the commonly used sodium oleate (NaOL) collector, and the separation of rhodochrosite and calcite can be achieved under neutral conditions. At a slurry pH of 7 and a dosage of 2.0 × 10−4 mol/L, TPA provided a recovery of 88.5% for rhodochrosite and only 15.0% for calcite. The mechanism of interaction between TPA and minerals was examined by contact angle, Zeta potential tests and Fourier transform infrared (FTIR) analysis, which indicated that TPA selectively adsorbed on the surface of rhodochrosite rather than calcite. Finally, the adsorption behavior of TPA molecules on the surface of rhodochrosite was confirmed by Density functional theory (DFT) calculation to be through electrostatic interaction. This paper provides a novel collector for the flotation separation of rhodochrosite from calcite with excellent collecting ability and selectivity, which is significant for the efficient utilization of manganese ore resources.

Fei L., Sun Q., Wang S., Cao Z., Sun H., Zhong H., Ma X.

Flotation recovery of micro-fine minerals has been constrained by low flotation efficiency due to the large surface area and small quality of fines, causing a huge waste of valuable resources. Herein, we developed a novel hydroxamate-modified N-acyl amino acid surfactant, 2-decanoylamino-4-hydroxycarbamoyl-butyric acid (DHBA), which can self-assemble via synergism among amide, carboxyl, and hydroxamate functional groups for achieving the efficient flocculation and recovery of fine rhodochrosite. The theoretical calculations and interface analyses revealed from microscopic perspective that the intramolecular synergistic chelation effect between carboxyl and hydroxamate groups conferred strong adsorption affinity of DHBA on rhodochrosite. On the other hand, the intermolecular H-bonds not only promote the tight arrangement of collectors on particle surface to enhance hydrophobic association effect, but also induce the agglomeration of collectors into net-like “macromolecules” clusters to produce adsorption bridging for fines. Eventually, the flocculation and flotation tests confirmed that DHBA exhibits a superior flocculation and collecting performance of fine rhodochrosite than very common collector octanoylhydroxamate acid (OHA) (the recovery reached 95.2 % for 1 × 10−4 mol·L−1 DHBA while 66.8 % for OHA). This research provides a feasible surfactant development strategy for flocculation-flotation.