Colloidal Aggregates Research Articles

Preparation of a Stable Indomethacin Supersaturated Solution Using Hydrophobically Modified Hydroxypropylmethylcellulose and α-Cyclodextrin.

In the present study, the stability of a supersaturated solution of indomethacin (IM) was evaluated in hydrophobically modified hydroxypropylmethylcellulose (HM-HPMC) solutions, with and without parent cyclodextrins (CDs). A highly supersaturated state of IM was maintained in the HM-HPMC solution and was further stabilized by the addition of α-CD and β-CD. Notably, the highest level of supersaturation was achieved in HM-HPMC/α-CD solution, which maintained a high concentration of IM for up to 120 h. IM concentrations in these solutions exceeded the amorphous solubility, indicating that phase separation had occurred. To explore this phase separation, Nile Red, a fluorescent probe sensitive to hydrophobic environments, was added to the supersaturated solutions. A higher fluorescence intensity was observed in the HM-HPMC/α-CD solution compared with the HM-HPMC solution, indicating a significant formation of colloidal amorphous aggregates in the supersaturated solution. Cryogenic transmission electron microscopy (Cryo TEM) analysis confirmed the presence of these aggregates, which appeared irregularly shaped. These findings suggest that the combination of HM-HPMC and α-CD effectively stabilized the colloidal amorphous aggregates in the IM supersaturated solution. The addition of α-CD facilitated the dissociation of HM-HPMC into smaller particles, increasing the number of hydrophobic stearyl moieties available for interactions with amorphous IM aggregates, thereby enhancing the stability of the supersaturated state. The combination of HM-HPMC and α-CD offers a promising approach to improving the oral bioavailability of drugs with poor water solubility.

Colloid aggregation simulation in a Poiseuille flow using SRD-MD simulations

Colloid aggregation simulation in a Poiseuille flow using SRD-MD simulations

In Vitro Biological Target Screening and Colloidal Aggregation of Minor Cannabinoids.

There is limited information on interactions between cannabinoids and many pharmacologically and toxicologically relevant targets in humans (e.g., receptors, ion channels, enzymes, and transporters). To address this data gap, seven cannabinoids were screened against a panel of 44 safety-related biological targets in competitive ligand binding or enzymatic activity assays. Diverse binding profiles were observed among the cannabinoids; however, colloidal aggregates were detected by dynamic light scattering and a detergent-sensitive enzyme inhibition assay. These aggregates may nonspecifically inhibit targets, yielding false positives. Although screening identified aggregates, additional testing is required to confirm cannabinoid aggregation in individual in vitro assays.

Colloids control the mobilization of released zinc- and cadmium- species in calcite-rich soils

Cadmium (Cd)-bearing sphalerite (SP, ZnS) and smithsonite (SM, ZnCO3) particulate matter (PM) is deposited on soils near carbonate-hosted Zn ore deposits. Whether and how carbonate rocks such as limestone influence the mobility of Cd and Zn in soils is largely unknown. For this reason, we conducted a soil incubation experiment to investigate the chemical and mineralogical changes in soil–soil solution samples, including the occurrence of Cd- and Zn-bearing colloids and nanoparticles. Here the addition of calcite to SP- and SM-spiked soils promoted the formation of Cd- and Zn- bearing nanoparticles and colloids and thus significantly decreased the concentrations of Cd and Zn in soil solutions. Transmission electron microscope and extended X-ray absorption fluorescence spectroscopy showed that the addition of calcite resulted in the formation of Fe-OM-Ca colloids (OM = organic matter), sequestrating Cd and Zn. Furthermore, the release of Ca2+ during the dissolution of calcite promoted the aggregation of colloids and thus decreased the mobility of Cd- and Zn-bearing colloids in the soil column. The addition of calcite also decreased the amount of Cd and Zn released from the dissolution of SP and SM through the formation of calcite nano-layers armoring particles of the SP and SM phases. This study provides new insights into the environmental fate of particulate Cd and Zn in soils around carbonate-hosted Pb-Zn ore deposits. Specifically, it shows that the formation and aggregation of Cd- and Zn-bearing colloids decrease the mobility and bioavailability of both elements.

Preparation, characterization and mechanism of SiO2@SiO2 core-shell microspheres through polymerization-induced colloid aggregation for fast separation using ultra performance liquid chromatography

The polymerization-induced colloid aggregation (PICA) method is commonly used to create SiO2@SiO2 core–shell silica microspheres (CSSMs), but it often encounters challenges such as incomplete shell coating and poor reproducibility. In this paper, the formation mechanism of the silica shell layer during the preparation of SiO2@SiO2 CSSMs using the PICA method was investigated. It was found that ureido modification can reduce the Zeta potential of the silica core surface, facilitating the deposition of coacervates formed by urea-formaldehyde resin (UF) and silica nanoparticles on the silica core surface to form the SiO2 shell layer when the Zeta potential of the surface is in the range of −20.1 mV to −4.8 mV. By controlling the interfacial state and surface potential of the SiO2 core, the issue of inconsistent reproducibility in preparing SiO2@SiO2 CSSMs can be overcome. Furthermore, optimization of experimental parameters such as pH, reaction temperature, water content, and reaction time can enhance the formation process. The thickness of the shell and pore size of CSSMs can be successfully adjusted by varying the reaction time and the particle size of colloidal silica sol, respectively. With optimal conditions, the semi-scale production yield of SiO2@SiO2 CSSMs can be increased to 50 g. The SiO2@SiO2 CSSMs were modified with octadecyltrichlorosilane (ODS) to be used as stationary phases in reversed phase liquid chromatography (RPLC) for fast separation of small solutes, peptides, and proteins. The superior separation efficiency indicates that the improved PICA method has the potential to be utilized as an alternative to the layer-by-layer method for large-scale production of SiO2@SiO2 CSSMs.

Predicting a Wide Range of Fractal Dimensions of Salt-Induced Aggregates in Water Using a Random Forest Model.

Salt-induced colloidal aggregates can significantly influence contaminant fate and transport in natural and engineered systems. These aggregates' fractal dimensions (df), ranging from 1.4 to 2.2, depend on various system variables. However, the quantitative relationship between these variables and df of aggregates has not been fully explored, especially in predicting a wide range of df. Here, we developed a random forest model capable of predicting the complete range of aggregate df using just four simple physical and chemical parameters of the aggregating system as inputs. The model accurately predicts the df of aggregates formed by colloids of different sizes, ranging from nano to micro sizes, after being trained and tested on appropriate data sets. Ionic strength (IS) has the most significant influence on the df of aggregates formed by microsized particles followed by the relative hydrodynamic radius of aggregates (Rh/Rp), particle concentration (Cp), and primary particle radius (Rp). For aggregates formed by both nano- and microsized particles, IS still has a strong influence on the df, with the significance of Rp increasing. All four inputs are negatively correlated with predicting the df of aggregates. The predictions align well with the physical interpretations.

Across‐Interface Effect of Alkylamine Salt on the Formation of Intermediate Phase and Defect Passivation in High‐Performance of Perovskite Solar Cells

AbstractHigh‐quality and low‐defect perovskite active layer (PVK) and electron transport layer (ETL) are essential for high‐performance perovskite solar cells (PSCs). Herein, an alkylamine salt, cyclohexylmethylammonium chloride (CMACl) is introduced into tin oxide (SnO2) ETL. CMACl, possessing protonated −NH3+ group and Cl− ions, not only effectively inhibits the aggregation of SnO2 colloids and enhances the quality of the ETLs, but also reduces and passivates the defects on ETLs. On the other hand, via the across‐interface effect of alkylamine salt by thermal diffusion, the CMACl‐PbI2 intermediate phase is formed and leads to the high quality of PVK, meanwhile, the defect on the buried interfaces and in the bulk of PVK are passivated by CMA+ and Cl− ions. Consequently, the CMACl‐modified PSC achieves a preeminent power conversion efficiency of 25.47% and excellent stability. This work demonstrates a facile and effective approach for synchronous optimization of ETL and PVK for high‐performance PSCs by across‐interface effect.

Structural analysis of superparamagnetic colloid aggregates confined in spherical cavities under external magnetic field

In this study, we investigated the behaviour of aggregates composed of superparamagnetic colloids under the influence of an external magnetic field, confined within several spherical cavities. The study included systems of two and three cavities in contact, as well as two cavities separated by a distance d along the direction of the external field. Monte Carlo computer simulations employing a model of hard spheres with central dipoles were realised to explore the behaviour of the magnetic particles, constrained to move within pairs (and trios) of spherical cavities. The primary focus of this investigation was to elucidate the structures formed by magnetic particles within systems presented here. Chains or ribbons primarily form within the central region of the spherical cavities. The aggregates within each cavity are drawn towards one another until they make contact at the closest points of the cavities. This behaviour is replicated when there is a separation distance between the spherical cavities, including cases where three cavities are in contact. This phenomenon may explain the observed attraction between magnetoliposomes as reported in the literature [García-Jimeno et al. Nanoscale. 9 (39), 15131–15143 (2017)].

Plasmonic Ag Nanoparticles: Correlating Nanofabrication and Aggregation for SERS Detection of Thiabendazole Pesticide.

The level of aggregation and aggregate morphology of metallic nanoparticles are factors that influence the SERS signal (surface-enhanced Raman scattering), affecting reproducibility and sensitivity. This study presents a systematic evaluation of the colloidal aggregation on the SERS signal by combining transmission electron microscopy and UV-vis extinction spectroscopy. It focuses on the effect of two methods of sample preparation ("external standard method-ESM" and "standard addition method-SAM") on the SERS signal using the fungicide thiabendazole (TBZ) in Ag colloid as a probe molecule. The TBZ critical concentration (concentration for which SERS reaches the maximum intensity) was 6.0 × 10-6 mol/L for ESM and 1.5 × 10-6 mol/L for SAM. Besides, TBZ exhibited a sigmoid-type isotherm for ESM, indicating formation of a TBZ first layer on Ag nanoparticles at lower concentrations (Ag aggregates more compact; size <500 nm) and TBZ multilayers at higher concentrations (Ag aggregates more branched; >2 μm). For SAM, the TBZ first layer formation was also observed at lower concentrations (Ag aggregates more branched; <2 μm). However, at higher concentrations, the Ag colloid degradation/precipitation was observed (Ag aggregates more compact; >2 μm). The Ag aggregation mechanisms align with reaction-limited colloidal aggregation at lower concentrations and diffusion-limited colloidal aggregation at higher concentrations. We believe these results contribute to the SERS research field despite all of the work already done over its 50-year history.

Ionizable Drugs Enable Intracellular Delivery of Co-Formulated siRNA.

Targeting complementary pathways in diseases such as cancer can be achieved with co-delivery of small interfering ribonucleic acid (siRNA) and small molecule drugs; however, current formulation strategies are typically limited to one, but not both. Here, ionizable small molecule drugs and siRNA are co-formulatedin drug-rich nanoparticles. Ionizable analogs of the selective estrogen receptor degrader fulvestrant self-assemble into colloidal drug aggregates and cause endosomal disruption, allowing co-delivery of siRNA against a non-druggable target. siRNA is encapsulated in lipid-stabilized, drug-rich colloidal nanoparticles where the ionizable lipid used in conventional lipid nanoparticles is replaced with an ionizable fulvestrant analog. The selection of an appropriate phospholipid and formulation buffer enables endocytosis and potent reporter gene knockdown in cancer cells. Importantly, siRNA targeting cyclin E1 is effectively delivered to drug-resistant breast cancer cells, demonstrating the utility of this approach. This strategy opens the possibility of using ionizable drugs to co-deliver RNA and ultimately improve therapeutic outcomes.

Multiscale Modeling Approach to Understand Mechanism of Deposit Control by Sulfonate-Based Lubricant Detergents.

Protecting the material surfaces from deposits and insoluble sludge particles extends the engine life and reduces waste. Lubricant detergents in engine oils are essential additive technologies that prevent deposit formation in internal combustion engines. In this study, the effect of sulfonate detergent on deposit formation in a passenger car engine is investigated with experimental and multiscale molecular modeling methods to present a unified approach. First principles density-functional theory calculations, statistical sampling methods, all-atom molecular dynamics simulations, and coarse-grained simulations are examined to elucidate deposit control mechanism of sulfonate detergents. Analysis of the results reveals that sludge particles in the drain oil are similar in structure to piston deposits, and they might be the precursors of the piston deposits. Main factor for controlling the sludge particle deposition is the prevention of their colloidal aggregation at the microscale in the base oil matrix. Aggregation can be mitigated by the intercalation of detergent polar groups between the particles. This is followed by the extension of hydrophobic tails into the oil phase, which decreases further aggregation via formation of a repulsive layer.

Humic acid enhances the co-transport of colloids and phosphorus in saturated porous media

Phosphorus (P) has been widely recognized as a substance that is difficult to transport due to its tendency to become easily fixed in the soil. However, many reports demonstrate that groundwater P pollution is rising in humus-rich areas. Research is urgently needed to confirm (or reject) the hypothesis that increased P pollution is related to humus, as there is currently limited quantitative research on this topic. In this study, we conducted a series of batch equilibrium adsorption-desorption experiments and column experiments to quantify the effects of montmorillonite colloids (MCs) and humic acids (HCs, the main components of humus) on the P transport behavior. The results indicate that P's adsorption and desorption behavior on MCs can be well simulated using the Langmuir and Temkin models (R2 > 0.91). Compared to the non-HC treatments, HCs significantly increased MCs' P adsorption and desorption capacity 5.18 and 7.21 times, respectively. Moreover, HCs facilitated the transport ability of the MC-P mixture through the saturated quartz sand column. In a 0.1 M NaCl solution, the MC-P mixture is nearly completely adsorbed on the surface of quartz sand, with a penetration rate of only 0.5%. In contrast, the HC-MC-P mixture can evidently penetrate further at a rate of 26.1%. The transport parameters fitted using HYDRUS-1D further indicated that the presence of humic acids significantly decreased the deposition coefficients of colloids, thereby enhancing the co-transport of colloids and P through the quartz sand porous medium. The potential mechanism of P pollution in humus-rich areas is likely enhanced by the formation of an HC-colloid-P mixture, which greatly increases the adsorption amount of P on colloids and enhances the electrostatic and spatial repulsion between colloids as well as between colloids and quartz sand. It reduces the aggregation and adsorption of colloids, ultimately transferring P into groundwater through colloid-facilitated co-transport. The findings of this study clarified the relationship between the transport of P, colloids, and HCs, which provides a theoretical basis for explaining the P pollution mechanism in humus-rich areas.

Spontaneous Photonic Jammed Packing of Core-Shell Colloids in Conductive Aqueous Inks for Non-Iridescent Structural Coloration.

Integrating structural colors and conductivity into aqueous inks has the potential to revolutionize wearable electronics, providing flexibility, sustainability, and artistic appeal to electronic components. This study aims to introduce bioinspired color engineering to conductive aqueous inks. Our self-assembly approach involves mixing poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with sulfonic acid-modified polystyrene (sPS) colloids to generate non-iridescent structural colors in the inks. This spontaneous structural coloration occurs because PEDOT:PSS and sPS colloids can self-assemble into core-shell structures and reversibly cluster into photonic aggregates of maximally random jammed packing within the aqueous environment, as demonstrated by small-angle X-ray scattering. Dissipative particle dynamics simulation confirms that the self-assembly aggregation of PEDOT:PSS chains and sPS colloids can be manipulated by the polymer-colloid interactions. Utilizing the finite-difference time-domain method, we demonstrate that the photonic aggregates of the core-shell colloids achieve close to maximum jammed packing, making them suitable for producing vivid structural colors. These versatile conductive inks offer adjustable color saturation and conductivity, with conductivity levels reaching 36 S cm-1 through the addition of polyethylene glycol oligomer, while enhanced water resistance and mechanical stability are achieved by doping with a cross-linker, poly(ethylene glycol) diglycidyl ether. With these unique features, the inks can create flexible, patterned circuits through processes like coating, writing, and dyeing on large areas, providing eco-friendly, visually appealing colors for customizable, stylish, comfortable, and wearable electronic devices.

Ni-Pt nanoparticle decorated, C, N-doped titania microparticles with low band gap energy as an efficient catalyst for hydrogen generation from hydrous hydrazine

The recent studies demonstrated superior catalytic activity and higher selectivity of carbon doped defect-rich catalysts in hydrogen production via dehydrogenation of hydrazine hydrate (HH). The synthesis of a new defect-rich catalyst capable of providing high hydrogen evolution rate in either catalytic or photocatalytic dehydrogenation of HH was aimed. For this purpose, “polymerization-induced colloid aggregation” (PICA) was proposed for the synthesis of carbon and nitrogen doped-mesoporous, gravel-like TiO2 microparticles (m-CN/TiO2 MPs) with a reduced band-gap energy of 2.3 eV. The Ti(III) content and oxygen vacancy concentration of pristine m-CN/TiO2 MPs were 6.06 % and 22.57 %, respectively. A defect-rich catalyst with high Ti(III) content (40.25 %) and high oxygen vacancy concentration (39.14 %) was obtained by the decoration of m-CN/TiO2 MPs with nickel-platinum nanoparticles (Ni-Pt NPs) via NaBH4 reduction (Ni-Pt/m-CN/TiO2 MPs) for the first time. The charge unbalance stimulated by Ti(III) species supported the formation of oxygen vacancies on m-CN/TiO2 MPs. The unique approach based on the synthesis of a C, N doped-mesoporous TiO2 based support by PICA and the deposition of Ni-Pt NPs by NaBH4 reduction in the presence of m-CN/TiO2 MPs allowed to obtain a heterogeneous catalyst with a low band energy of 1.7 eV for hydrogen production. The turnover frequency (TOF) values up to 1140.7 h−1 were achieved with 100 % H2 selectivity using the catalyst containing an active metallic site composed of 78.3 % mol Ni and 21.7 % mol Pt on m-CN/TiO2 MPs in the catalytic dehydrogenations performed at 323 K. The TOF values up to 530 h−1 with 100 % H2 selectivity were obtained by using Ni-Pt/m-CN/TiO2 MPs as a photocatalyst in the visible light driven photocatalytic dehydrogenation of HH at room temperature.

Sodium dodecyl benzene sulfonate as a new ligand to enhance the flotation of cassiterite in Pb-BHA system

As high-quality cassiterite resources dwindle, the significance of cassiterite associated with scheelite escalates. In this study, we synthesized a novel lead-group double ligand collector (Pb-BHA-SDBS) by introducing a new ligand, sodium dodecyl benzene sulfonate (SDBS), into the structure of lead complexes of benzohydroxamic acid (Pb-BHA). The flotation performance of Pb-BHA-SDBS was investigated by single-mineral flotation. The structural and chemical properties of Pb-BHA-SDBS were systematically investigated through FTIR, XPS, and quantum chemical calculations. The mechanism of enhancing cassiterite flotation with Pb-BHA-SDBS were investigated through adsorption energy analysis, XPS, AFM and contact angle analysis. The flotation recovery of cassiterite greatly increased from ≤30 % to ≥80 % when the Pb-BHA-SDBS is utilized as the collector. The FTIR and XPS results indicated that both SDBS and BHA form coordination bonds with lead ions, significantly strengthening the adsorption ability on the cassiterite surface. The adsorption of Pb-BHA-SDBS on the surface of cassiterite forms larger colloidal aggregates, further enhancing the roughness and hydrophobicity of the cassiterite surface, thereby strengthening the flotation of cassiterite.

A Chemical Mechanism for the Bistable‐to‐Oscillatory Transition in Colloidal Aggregates of Silver Phosphate

AbstractWe previously reported collective behavior in colloidal aggregates of silver phosphate in H2O2 and under UV light. Diffusiophoretic interactions between aggregates lead to non‐linear behavior such as oscillations and synchronization, in which oscillation frequencies increase with H2O2 concentration. The aggregates transition between schooling and dispersed behaviors with incipient spatiotemporal correlations. We identified a kinetic model that maps the chemical species that are thought to underlie non‐linear phenomena in the colloidal aggregates, i. e. adsorbed oxygen species *OOH− and *O. We investigate the emergent dynamics for the simplest case, the coupling of two otherwise bistable clusters. Two coupling schemes are proposed and we find that – depending on whether the coupling is excitatory or inhibitory – the clusters may oscillate with zero or π phase shift.

Elemental and particle size fractionation during the transport of Eu(III)-silicate colloids in water-saturated porous media

Actinides (An)-bearing colloids could facilitate An migration in the environment. However, little is known about the transport behavior of An(III)-silicate colloids, which are readily formed by the reaction of An3+ with silicic acid under environmental conditions. Column experiments were conducted to investigate the transport of Eu(III)-silicate colloids (chemical analog of An(III)-silicate colloids) in water-saturated porous media as a function of pH, ionic strength (IS) and the presence of fulvic acid (FA). The results showed that colloid transport was more favorable at relatively low IS (≤ 50 mM) and high pH levels (pH ≥ 7). The presence of FA (5−10 mg/L) significantly enhanced the colloid transport. Under high IS (≥ 100 mM), the transport feature of colloids was turned from blocking to ripening due to the on-going aggregation of colloids. Additionally, an interesting elemental fractionation, i.e., a discrepancy in the breakthrough curves (BTCs) with respect to the C/C0 values of Si and Eu, was observed in the IS of 100−500 mM. A detailed investigation indicated that the elemental fractionation could be attributed to the partial Si dissolution of the colloids, the heterogeneity of the colloid size and element composition, and particle size fractionation during colloid transport. Extended Derjaguin-Landau-Verwey-Overbeek interaction energy calculations and convective-dispersive equation modeling were performed to illustrate variations in the colloid transport profiles. These findings illustrate the importance of Si dissolution in the migration of metal-silicate colloids and highlight the significant influence of the heterogeneity of colloid size and composition on the transport/migration behavior of colloids in the environment.

Predictions of Colloidal Molecular Aggregation Using AI/ML Models.

To facilitate the triage of hits from small molecule screens, we have used various AI/ML techniques and experimentally observed data sets to build models aimed at predicting colloidal aggregation of small organic molecules in aqueous solution. We have found that Naïve Bayesian and deep neural networks outperform logistic regression, recursive partitioning tree, support vector machine, and random forest techniques by having the lowest balanced error rate (BER) for the test set. Derived predictive classification models consistently and successfully discriminated aggregator molecules from nonaggregator hits. An analysis of molecular descriptors in favor of colloidal aggregation confirms previous observations (hydrophobicity, molecular weight, and solubility) in addition to undescribed molecular descriptors such as the fraction of sp3 carbon atoms (Fsp3), and electrotopological state of hydroxyl groups (ES_Sum_sOH). Naïve Bayesian modeling and scaffold tree analysis have revealed chemical features/scaffolds contributing the most to colloidal aggregation and nonaggregation, respectively. These results highlight the importance of scaffolds with high Fsp3 values in promoting nonaggregation. Matched molecular pair analysis (MMPA) has also deciphered context-dependent substitutions, which can be used to design nonaggregator molecules. We found that most matched molecular pairs have a neutral effect on aggregation propensity. We have prospectively applied our predictive models to assist in chemical library triage for optimal plate selection diversity and purchase for high throughput screening (HTS) in drug discovery projects.

Colloidal Aggregation Confounds Cell-Based Covid-19 Antiviral Screens.

Colloidal aggregation is one of the largest contributors to false positives in early drug discovery. Here, we consider aggregation's role in cell-based infectivity assays in Covid-19 drug repurposing. We investigated the potential aggregation of 41 drug candidates reported as SARs-CoV-2 entry inhibitors. Of these, 17 formed colloidal particles by dynamic light scattering and exhibited detergent-dependent enzyme inhibition. To evaluate the impact of aggregation on antiviral efficacy in cells, we presaturated the colloidal drug suspensions with BSA or spun them down by centrifugation and measured the effects on spike pseudovirus infectivity. Antiviral potencies diminished by at least 10-fold following both BSA and centrifugation treatments, supporting a colloid-based mechanism. Aggregates induced puncta of the labeled spike protein in fluorescence microscopy, consistent with sequestration of the protein on the colloidal particles. These observations suggest that colloidal aggregation is common among cell-based antiviral drug repurposing and offers rapid counter-screens to detect and eliminate these artifacts.

Adsorption and distribution of heavy metals in aquatic environments: The role of colloids and effects of environmental factors

The study investigated the distributions of heavy metals (Cd, Cr, Cu, Mn, and Pb) between dissolved fraction (<0.7 µm) and particles (>0.7 µm) during the adsorption process. The dissolved fraction was further separated into truly dissolved (<3 kDa) and colloidal (3 kDa-0.7 µm) fractions. Significant metal adsorption occurred on the colloids, resulting in their aggregation into particles, which in turn influenced the particle adsorption kinetics. Colloids could either accelerate or inhibit the transformation of metal ions into particulates, depending on their stability. Competitive metals for colloids (Pb and Cr) were more susceptible to the effects of colloids than other elements. DOM was the predominant environmental factor influencing colloid behavior. The XDLVO theory showed that DOM enhanced the negative charge of colloids and made the colloid surface more hydrophilic, inhibiting the aggregation of colloids. DOM resulted in substantial increases in the concentrations of colloidal Pb and Cr from 0.31 μg/L and 4.58 μg/L to 20.52 μg/L and 43.51 μg/L, respectively, whereas the increment for less competitive metals (Cd and Mn) was smaller. These findings suggest that the distribution of heavy metals is influenced not only by adsorption from particles and ions but also by the complex dynamics of colloids.