DLVO Research Articles

Perfluorobutanoic acid weakens the heterogeneous aggregation of microplastics and microalgae: Perspective from physicochemical properties, extracellular polymeric substances secretion and DLVO theory

Microplastics (MPs) and per- and poly-fluoroalkyl substances extensively coexist in aquatic environments and potentially endanger organisms. Microalgae may decrease the effective concentration of pollutants via hetero-aggregation with MPs and adsorption of emerging contaminants. However, the potential influence of coexistent pollutants on hetero-aggregation of MPs and microalgae remains unknown. This study investigated the hetero-aggregation process involving different sizes of polystyrene (PS, 3.0 and 50.0 μm) with Chlorella sorokiniana (C. sorokiniana) in the presence or absence of perfluorobutanoic acid (PFBA) along settling experiments, scanning electron microscope, and Derjaguin-Landau-Verwey-Overbeek (DLVO) model. We found that the hetero-aggregation between C. sorokiniana and 3 μm PS was more pronounced than with 50 μm PS, while PFBA inhibited this process. ΔOD1 values (reflected hetero-aggregation level) for 3PS-cells and 50PS-cells were 0.189 and 0.087, respectively, and PFBA decreased these values to 0.134 and 0.033. Furthermore, extracellular polymeric substances, known as inducer of hetero-aggregation, increased by 14.33% when exposed to 3 μm PS alone, whereas the co-exposure group showed a decrease of 4.52% compared to 3PS-cells group. PFBA also significantly decreased the protein/polysaccharide ratios in both MPs sizes, reducing hetero-aggregation. DLVO theory revealed that microalgae lowered the energy barrier significantly, while PFBA elevated it, indicating that hetero-aggregation was inhibited by PFBA. This study provides new perspectives for pollutant removal and toxicity variation in aquatic environments.

Influence of Particle Size on Flotation Separation of Ilmenite and Forsterite

In addition to bubble–particle interaction, particle–particle interaction also has a significant influence on mineral flotation. Fine particles that coat the mineral surface prevent direct contact with collectors and/or air bubbles, thereby lowering flotation recovery. Calculating the particle interaction energy can help in evaluating the interaction behavior of particles. In this study, the floatability of coarse ilmenite (−151 + 74 μm) and different particle sizes (−45 + 25, −25 + 19, −19 μm) of forsterite with NaOL as a collector was investigated. The results showed that forsterite sizes of −45 + 25 and −25 + 19 μm had no effect on the ilmenite floatability, whereas −19 μm forsterite significantly reduced ilmenite floatability. A particle size analysis of artificially mixed minerals and a scanning electron microscopy (SEM) analysis of the flotation products showed that heterogeneous aggregation occurred between ilmenite and −19 μm forsterite particles. The extended DLVO (Derjaguin–Landau–Verwey–Overbeek) theory was applied to calculate the interaction energy between mineral particles using data from zeta potential and contact angle measurements. The results showed that the interaction barriers between ilmenite (−151 + 74 μm) and forsterite (−45 + 25, −25 + 19, and −19 μm) were 11.94 × 103 kT, 8.23 × 103 kT and 4.09 × 103 kT, respectively. Additionally, the interaction barrier between forsterite particles smaller than 19 μm was 0.51 × 103 kT. The strength of the barrier decreased as the size of the forsterite decreased. Therefore, fine forsterite particles and aggregated forsterite can easily overcome the energy barrier, coating the ilmenite particle surface. This explains the effect of different forsterite sizes on the floatability of ilmenite and the underlying mechanism of particle interaction.

A cationic polyelectrolyte for enhancing dewatering of montmorillonite-containing coal slime: adsorption and modification mechanism

ABSTRACT In this study, a cationic polyelectrolyte (Poly dimethyl diallyl ammonium chloride, PDADMAC) was introduced as a filter aid to enhance the dewatering effect of montmorillonite (MT)-containing coal slime, and compared with cationic polyacrylamide (CPAM). The dewatering performance of PDADMAC and CPAM was evaluated based on vacuum filtration experiments. The modification mechanism of PDADMAC on Mt particle surface was revealed by filter cake pore distribution, zeta potential, contact angle and Atomic Force Microscopy (AFM). The adsorption difference between PDADMAC and CPAM on Mt surface was studied by Density Functional Theory (DFT). In addition, DLVO theory further explains the mechanism of PDADMAC enhancing dewatering from the perspective of interaction force. The optimal dosage of PDADMAC was 125 g/t, and the filter cake moisture content was reduced by 3%. Compared to CPAM, PDADMAC achieves efficient dewatering at a lower dosage. PDADMAC has a more prominent ability to neutralize charge, and its effect on interparticle interactions was a potential mechanism to promote dehydration.

Boron Removal in Aqueous Solutions Using Adsorption with Sugarcane Bagasse Biochar and Ammonia Nanobubbles.

Boron is a naturally occurring trace chemical element. High concentrations of boron in nature can adversely affect biological systems and cause severe pollution to the ecological environment. We examined a method to effectively remove boron ions from water systems using sugarcane bagasse biochar from agricultural waste with NH3 nanobubbles (10% NH3 and 90% N2). We studied the effects of the boron solution concentration, pH, and adsorption time on the adsorption of boron by the modified biochar. At the same time, the possibility of using magnesium chloride and NH3 nanobubbles to enhance the adsorption capacity of the biochar was explored. The carbonization temperature of sugarcane bagasse was investigated using thermogravimetric analysis. It was characterized using XRD, SEM, and BET analysis. The boron adsorption results showed that, under alkaline conditions above pH 9, the adsorption capacity of the positively charged modified biochar was improved under the double-layer effect of magnesium ions and NH3 nanobubbles, because the boron existed in the form of negatively charged borate B(OH)4- anion groups. Moreover, cations on the NH3 nanobubble could adsorb the boron. When the NH3 nanobubbles with boron and the modified biochar with boron could coagulate each other, the boron was removed to a significant extent. Extended DLVO theory was adopted to model the interaction between the NH3 nanobubble and modified biochar. The boron adsorption capacity was 36 mg/g at room temperature according to a Langmuir adsorption isotherm. The adsorbed boron was investigated using FT-IR and XPS analysis. The ammonia could be removed using zeolite molecular sieves and heating. Boron in an aqueous solution can be removed via adsorption with modified biochar with NH3 nanobubbles and MgCl2 addition.

Effect of particle size on the transport of polystyrene micro- and nanoplastic particles through quartz sand under unsaturated conditions

Micro- and nanoplastics (MNPs) are contaminants of emerging concern recently found in soil ecosystems. Their presence in terrestrial environments and their migration to aquatic environments may become a risk for the health of ecosystems and, through them, of humans. Understanding the interaction between particle properties and physicochemical and hydrodynamic factors is crucial to evaluate their fate and their potential infiltration towards groundwater. This study investigates the impact of particle size on MNPs transport through sand under unsaturated conditions. Infiltration column experiments with polystyrene MNPs ranging from 120 to 10,000 nm were conducted and supported by numerical modelling to derive reactive transport parameters. Results show a significant effect of particle size on the transport of MNPs, with higher recovery values observed for smaller particles (120 nm; 95.11%) compared to larger particles (1,000 nm; 71.44%). No breakthrough was observed for 10,000 nm particles, indicating a complete retention within the quartz sand matrix. DLVO theory confirmed the dominance of electrostatic repulsive forces between MNPs and sand grains, suggesting an unfavourable environment for MNPs to adhere to quartz sand. Consequently, particle retention in the sand matrix occurs predominantly by physical processes. Equilibrium sorption modelling reveals that larger particles (1,000 nm) tend to be immobilized in small pores throats due to straining, resulting in lower recoveries. When they are not trapped, particles tend to travel faster through preferential flows due to a size exclusion effect, evidenced by shorter arrival times at the column outlet compared to tracers. These findings highlight the influence of particle size on the transport and retention of MNPs in quartz sand under unsaturated conditions and contribute to a better understanding of their transport dynamics and environmental fate.

The origin of interparticle aggregation: Probing the long-range hydrophobic forces between particles induced by nanobubbles in aqueous solutions

The processes of particle–particle collision, adhesion, and detachment are omnipresent in the solid particle separation and purification processes. Nanobubbles, serving as a critical medium for interactions between particles, play a pivotal role in numerous fields of separation and purification such as mineral flotation, hydrometallurgy, chemical engineering, materials, and more. The elucidation of the principles governing nanobubbles’ involvement in interparticle interactions holds significant implications for enhancing and controlling separation and purification processes. The impact of nanobubbles on interparticle interactions between calcite particles was investigated in this study by measuring the forces between particles with and without nanobubbles and analysing them using DLVO and EDLVO theories. The experimental results demonstrate the occurrence of long-range attractive forces and significant adhesion between particles in the presence of nanobubbles under natural pH and ultrapure water conditions, phenomena that cannot be explained by classical DLVO theory. The generation of long-range hydrophobic attraction at the particle interface due to nanobubbles was confirmed through further EDLVO calculations and modifications, enhancing the stability of particle flocculation. Additionally, for the first time, the entire process from contact to detachment between the “particle-nanobubble” system in atomic force microscopy (AFM) simulations was described by combining experimental force curves with stepwise graphical interpretation. This approach provides valuable guidance for the analysis of bubble and soft matter interactions under AFM. The results of this study indicate that nanobubbles can indirectly alter the hydrophilicity and hydrophobicity of particles, increasing the probability of particle adhesion and reducing the probability of desorption, thereby enhancing the stability of particle flocculation.

Controlled Sol-Gel Transitions of Metal-Organic Membrane-Enveloped Cellulose Nanofibrils via Metal Coordination in Aqueous Media.

We report a metal coordination-driven sol-gel transition system where cellulose nanofibrils are enveloped by a rationally designed metal-organic membrane (MOM) in an aqueous medium. Specifically, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized bacterial cellulose (TOBC) is encapsulated within an MOM comprising Zn2+ and the chelator phytic acid (PA), denoted TOBCMOM. Using the DLVO theory, we elucidate how tuning the metal ion valence in TOBCMOM modulates the sol-gel transition by controlling interfibrillar attractive forces. Notably, TOBCMOM fluids exhibit relaxation times consistent with the Kohlrausch-Williams-Watts (KWW) function. Significantly, we demonstrate reversible, sustainable sol-gel transitions in TOBCMOM under stepwise mechanical strain. This facile approach enables rheological tailoring of aqueous media, promising for the development of advanced stimuli-responsive smart fluids for applications in cosmetics, food science, and pharmaceutical formulations.

Real-time two-dimensional visualization reveals the transport mechanisms of biochar colloids in the presence of DOM in porous media

Biochar colloids (BCs) have attracted much attention globally, and their fate and transport in the subsurface are significantly influenced by soil-dissolved organic matter (DOM) in soil. This study utilized a real-time and non-invasive visualization system to reveal the transport and retention behavior of BCs in the presence of DOM in two-dimensional porous media. Results indicated that the presence of DOM enhanced the transport of BCs, due to its increased negative charge density and increased repulsion between BCs. The change in the particle size of the porous medium was also shown to affect the BCs transport in the porous media. Additionally, the negative charge of BCs shielded by high IS, the mobility of BCs decreased by 30.37 % from 1 mM to 50 mM. When the pH was increased from 5 to 9, the oxygen-containing functional groups of BCs and DOM were dissociated, and the mobility of BCs increased by 32.41 %. Through a simplified Double-Monod model, we fitted the breakthrough curves for BCs transport in porous media (R2 > 0.94). Moreover, the mechanism of different conditions on colloid clogging behavior was further elucidated through the DLVO theory. These findings extend the understanding of the environmental behavior of BCs in the presence of DOM derived from soil, enabling us to assess better and predict their environmental risks.

Soy glycinin-carboxymethyl cellulose “chain bead-like” nanocomplexes: Focus on formation mechanism, functional characteristics and stability properties

In this study, the aim was to solve the problem of poor functional characteristics and stability of soy glycinin (11S). 11S and carboxymethyl cellulose (CMC) nanocomplexes (SCs) were prepared by pH-driven method. They were further analyzed for the effects on the SCs formation mechanism, function and stability properties of CMC concentration (0.05%, 0.1%, 0.5%, 1%, w/v) and degree of substitution (DS, 0.7, 0.9, 1.2). The particle size and zeta potential indicated that the SCs were small in size, uniformly distributed, and high in potential. Classical DLVO theory calculation, FTIR, 3D fluorescence spectroscopy, and UV spectroscopy revealed that 11S and CMC interact mainly through electrostatic forces and hydrogen bonding, and the secondary and tertiary structures of the protein were altered. SEM, AFM and TEM showed that 11S formed “protein nanobeads” and engulfed the “chain” of CMC, generating “chain bead-like” SCs. With the increase in CMC concentration and DS, the hydrophobicity decreased and the molecular flexibility increased of SCs. The solubility, turbidity, emulsifying and foaming properties showed the tendency to enhance and then decrease as the CMC concentration increased; these properties improved better when the DS was stronger. The optimum functional characteristics of the formed SCs were obtained when the concentration and DS of CMC were 0.5% and 1.2, respectively. Furthermore, the addition of CMC significantly improved the pH, ionic stability and thermal stability of the nanocomplexes. This study will provide a theoretical basis for deeper understanding of the mechanism of pH-driven protein-polysaccharide interactions and applications in functional foods.

Impact of temperature and salinity on fines detachment: AFM measurements and XDLVO theory

Fine particle detachment and subsequent migration can lead to severe pore plugging and consequent permeability decline. Therefore, it is crucial to quantify the critical condition when fine particle detachment occurs. The frequently observed deviations or even contradictions between experimental results and theoretical predictions of fines detachment arise from an insufficient understanding of adhesion force that can be highly influenced by salinity and temperature. To clarify the intrinsic influence of salinity and temperature on fines detachment, adhesion forces between carboxyl microspheres and hydrophilic silica substrates in an aqueous medium were measured at various salinities and temperatures using atomic force microscopy (AFM). The AFM-measured adhesion force decreases with increasing salinity or temperature. Trends of mean measured adhesion forces with temperature and salinity were compared with the DLVO and XDLVO theories. DLVO theory captured the trend with temperature via the impact of temperature on electric double layer interactions, whereas XDLVO theory captured the observed trend with salinity via the impact of salinity on the repulsive hydration force. Our results highlight the significance of hydration force in accurately predicting the fate of fines in porous media.

Binding and unbinding of flexible surfactant bilayers

We have probed the influence of salt and temperature on the spatial periodicity (d) of the fluid lamellar (Lα) phase formed by two ionic amphiphiles, whose bilayer bending rigidity moduli are widely different. In the case of rigid 1,2-dimyristoyl-3-trimethylammonium-propane (chloride salt) (DMTAP) bilayers, d is found to decrease with increasing salt concentration (Cs) in the solution, in qualitative agreement with the DLVO theory. d depends only very weakly on temperature in this system. On the other hand, in the Lα phase formed by highly flexible didodecyldimethylammonium chloride (DDAC) bilayers, d is not set by the minimum of the DLVO potential over a wide range of Cs, due to inter-bilayer repulsion arising from thermal undulations of the bilayers. An abrupt transformation of this undulation stabilized swollen Lα phase into a collapsed Lα phase, where d is comparable to the bilayer thickness, is observed above a threshold value of Cs. At higher Cs an unbinding transition of the bilayers is observed on heating, where the collapsed Lα phase transforms into a dispersion of spatially uncorrelated bilayers. Our observations are consistent with this transition being first-order.

Enhanced performance of aerobic granular sludge-membrane system through the utilization of different iron-based nano-metal oxides for mitigating membrane fouling

Fe3O4, γ-Fe2O3, and α-Fe2O3 nanoparticles play a crucial role in influencing the adsorption capacity and pretreatment efficacy as iron-based nano-metal oxides due to their distinct structural and physicochemical properties. However, the impact of these adsorbents on membrane filtration efficiency remains unexplored. This study aimed to investigate the influence of these three adsorbents on membrane fouling in an aerobic granular sludge–membrane system (AGSMS) used for municipal wastewater reuse treatment. The results demonstrated that under optimal conditions, γ-Fe2O3 exhibited superior effectiveness in removing low and medium molecular weight contaminants from wastewater, resulting in a higher normalized flux (0.59) and reduced total fouling resistance (2.66 × 1011 m−1). It also showed the highest removal rate for organic matter and suspended solids, making it particularly effective in mitigating AGSMS membrane fouling. However, excessive addition (2 g/L) of Fe3O4, γ-Fe2O3, and α-Fe2O3 could potentially hinder the proper operation of the AGSMS. Pre-adsorption facilitated the formation of a porous cake layer while inhibiting standard blocking behavior. Additionally, the extended Derjaguin–Landau–Verwey–Overbeek theory analysis revealed a substantial energy barrier between membrane-foulant interactions (125.65 kT) as well as foulant-foulant interactions (62.06 kT) within the γ-Fe2O3 system, confirming its exceptional antifouling characteristics. This study offers valuable insights into the selection of iron oxide adsorbents for membrane fouling mitigation and wastewater reuse.

Utilization of Lead Nitrate to Enhance the Impact of Hydroxamic Acids on the Hydrophobic Aggregation and Flotation Behavior of Cassiterite.

Lead nitrate (LN) is frequently employed as an activator in the flotation of cassiterite using hydroxamic acids as the collectors. This study investigated the effect of LN on the hydrophobic aggregation of cassiterite when benzohydroxamic acid (BHA), hexyl hydroxamate (HHA), and octyl hydroxamate (OHA) were used as the collectors through micro-flotation, focused beam reflectance measurement (FBRM) and a particle video microscope (PVM), zeta potential, and the extended DLVO theory. Micro-flotation tests confirmed that LN activated the flotation of cassiterite using the hydroxamic acids as collectors. Focused beam reflectance measurement (FBRM) and a particle video microscope (PVM) were used to capture in situ data on the changes in size distribution and morphology of cassiterite aggregates during stirring. The FBRM and PVM image results indicated that the addition of LN could promote the formation of hydrophobic aggregates of fine cassiterite, when BHA or HHA was used as the collector, and reduce the dosage of OHA needed to induce the formation of hydrophobic aggregates of cassiterite. The extended DLVO theory interaction energies indicated that the presence of LN could decrease the electrostatic interaction energies (Vedl) and increase the hydrophobic interaction energies (Vhy) between cassiterite particles, resulting in the disappearance of the high energy barriers that existed between the particles in the absence of LN. Thus, cassiterite particles could aggregate in the presence of LN when BHA, HHA, or a low concentration of OHA was used as the collector.

Efficient Li+/Mg2+ separation nanofiltration membranes modified by amine-functionalized TiO2 nanoparticles

Positively charged nanofiltration (NF) membranes are widely used to separate Li+ and Mg2+, which play an important role in extracting lithium from salt lakes. Despite its widespread use, the polyethyleneimine-trimesoyl chloride (PEI-TMC) membrane has attracted attention due to its limited permeance and separation efficiency. To address these challenges, we introduced amine-functionalized titanium dioxide (TiO2-NH2) nanoparticles into the interfacial polymerization (IP) reaction. The introduction of TiO2-NH2 reduced the diffusion rate of PEI and formed nanoscale water channels in the polyamide (PA) layer. This modification effectively modulated the structure of the NF membrane. The NF membrane exhibited high water permeance (9.65 L·m−2·h−1·bar−1) and Li+/Mg2+ selectivity (SLi, Mg = 16.31) when 0.03 wt% TiO2-NH2 was used. The DLVO theory and transition state theory showed that the introduction of TiO2-NH2 improved the rejection of Li+ and Mg2+ by the membrane. Furthermore, the optimized NF membranes demonstrated excellent stability during long-term filtration and in the mixed salt solutions with varying Mg2+/Li+ mass ratios. This work is of great significance for designing and advancing membrane materials that facilitate the efficient separation of lithium from salt lakes with high Mg2+/Li+ mass ratios.

Study on the adsorption mechanism of fluorescent nano-tracer in sandstone core

Chemical tracer testing technology has increasingly become the preferred method for reservoir monitoring in oil fields due to its low cost and high efficiency. Understanding the migration behavior and adsorption mechanisms of chemical tracers in porous media is crucial for designing tracer injection processes and enhancing the accuracy of tracer test interpretation. This study employs an enhanced Stöber sol-gel method to synthesize fluorescent silica nanoparticles. After surface modification with the silane coupling agent γ-(methacryloyloxy) propyltrimethoxysilane (KH570) and doping with two fluorescent dyes, a multicolor fluorescent nano-tracer (PMFN) was synthesized. This study conducted dynamic and equilibrium adsorption experiments to investigate the adsorption behavior of PMFN on sandstone surfaces. To elucidate the adsorption mechanism of PMFN, we fitted the adsorption equilibrium experimental data using the Langmuir, Freundlich, and Temkin isothermal adsorption models. The adsorption kinetics were studied using the Lagergren, Elovich, and pseudo-first-order kinetic models. Additionally, we assessed the influence of ionic strength and particle size on the adsorption of PMFN by calculating the DLVO interaction forces between PMFN and the sandstone surface. The results showed that PMFN adsorption on sandstone primarily occurs in the pre-contact stage and is characterized by monolayer adsorption. When the ionic strength of the solution is 0.001 mol/L, the maximum repulsive energy barrier between PMFN and the sandstone surface hinders adsorption.

Sustainable control of organic-inorganic combined fouling of electroactive ultrafiltration membrane during electrocatalytic-driven self-cleaning process: Mechanism and implications

Organic-inorganic combined fouling of membrane is a tough problem that restrained its application in water treatment, which was insufficient and non-sustainable to be alleviated by conventional chemical cleaning. Herein, a facile and sustainable control strategy was developed to mitigate biopolymer-Ca2+ combined fouling for an electroactive metal-organic framework ultrafiltration membrane. Bovine serum albumin (BSA) and sodium alginate (SA) were selected as model biopolymer. The results showed BSA and SA fouling both accelerated with increasing Ca2+ concentration (0–1.0 mM) via calcium bridging action and hydraulic cleaning was insufficient to restore flux (flux recovery < 7 %). By comparison, flux can be fully recovered by applying electricity to all combined fouling, suggesting membrane presented outstanding self-cleaning performance. According to the free radical quenching test and physicochemical property of biopolymer, fouling control mechanism was revealed because in-situ electro-generated OH and O2− free radicals caused decomplexation of biopolymer and Ca2+, and then degraded biopolymer into smaller and less hydrophobic fragments that repulsed membrane. Extended Derjaguin–Landau–Verwey–Overbeek theory further unveiled the foulants-membrane interaction shifted from attraction to repulsion after self-cleaning. This strategy has the advantages of low chemical cleaning reagents and energy consumption, which may provide the guidance for sustainable control of organic-inorganic combined membrane fouling.

Swelling characteristics of montmorillonite mineral particles in Gaomiaozi bentonite

Highly compacted bentonite is an ideal back-filling (buffer) material for the deep geological disposal of high-level radioactive waste. Montmorillonite is the main constituent mineral of it. The nanoscopic swelling characteristic of montmorillonite mineral particles greatly influences the macroscopic buffering performance of highly compacted bentonite blocks. Firstly, the montmorillonite suspension liquid was exfoliated by freeze-thaw cycles, the appropriate mineral particles were selected by atomic force microscope (AFM) for making colloidal probes. Then, the swelling pressure between mineral particles was measured by AFM, investigating the effects of interlayer distance, layer number, temperature, and interlayer cation type on the nanoscale swelling pressure. The experimental results showed that the swelling pressure of montmorillonite mineral particles peaks at about 0.7–0.8 nm interlayer distance. The swelling pressure of mineral particles with more layers is smaller. The higher the ambient temperature, the greater the swelling pressure. The swelling pressure of Ca-montmorillonite is significantly larger than that of Na-montmorillonite. The Laird model has a relatively good applicability with the interlayer distance of 0.6–1.2 nm; the DLVO theory has a good applicability with the interlayer distance greater than 1.5 nm. Finally, a predictive model was developed for the swelling pressure of nanoscopic mineral particles considering the effect of layer number. The research results provide data support and theoretical support for swelling pressure generation and cross-scale transmission mechanism of highly compacted bentonite hydration.

New Insights into the Formation of Aggregates of Bidisperse Nano- and Microplastics in Water Based on the Analysis of In Situ Microscopy and Molecular Simulation.

Microplastics (MPs) and nanoplastics (NPs) in water pose a global threat to human health and the environment. To develop efficient removal strategies, it is crucial to understand how these particles behave as they aggregate. However, our knowledge of the process of aggregate formation from primary particles of different sizes is limited. In this study, we analyzed the growth kinetics and structures of aggregates formed by polystyrene MPs in mono- and bidisperse systems using in situ microscopy and image analysis. Our findings show that the scaling behavior of aggregate growth remains unaffected by the primary particle size distribution, but it does delay the onset of rapid aggregation. We also performed a structural analysis that reveals the power law dependence of aggregate fractal dimension (df) in both mono- and bidisperse systems, with mean df consistent with diffusion-limited cluster aggregation (DLCA) aggregates. Our results also suggest that the df of aggregates is insensitive to the shape anisotropy. We simulated molecular forces driving aggregation of polystyrene NPs of different sizes under high ionic strength conditions. These conditions represent salt concentration in ocean water and wastewater, where the DLVO theory does not apply. Our simulation results show that the aggregation tendency of the NPs increases with the ionic strength. The increase in the aggregation is caused by the depletion of clusters of ions from the NPs surface.

The inhibition mechanism of esterified starch on flotation separation of fluorite and calcite

Herein, the flotation behavior of fluorite and calcite was examined before and after starch esterification through mineral flotation experiments. Moreover, the adsorption action mechanisms on minerals before and after starch esterification were investigated using methods such as solution surface tension measurement, infrared spectroscopy, and extended Derjaguin–Landau–Verwey–Overbeek theory. The results showed that after starch esterification (esterified starch), there was a greater difference in the mineral recovery rate compared to before starch esterification (ordinary starch), with a better inhibition effect on calcite. The interaction between mineral surfaces and ordinary starch was weaker than the interaction between minerals and esterified starch. In particular, after starch esterification, the surface tension increased, two minerals contact angle decreased, the surface potential became more negative, and the difference in the mineral recovery rate was greater than before starch esterification. After the interaction between minerals and esterified starch, calcite particles displayed good dispersibility, while the cohesion between calcite particles and sodium oleate particles decreased; notably, the effect on fluorite was opposite. Calcite and esterified starch exhibited chemical adsorption, impeding the adsorption of sodium oleate onto calcite and resulting in calcite inhibition. The interaction between fluorite surface and esterified starch involved electrostatic adsorption, with sodium oleate chemically adsorbed onto the fluorite surface. Chemical adsorption proved stronger than electrostatic adsorption, enabling sodium oleate to capture fluorite.

On the DLVO Theory: Experimentally Measured Debye–Hückel Length

On the DLVO Theory: Experimentally Measured Debye–Hückel Length