Droplet Impact on the Superhydrophobic Surface with Singularities.

Reducing the contact time of an impacting droplet is highly desirable in various industrial fields including anti-icing. With the straightforward upscaling advantage, singularities on superhydrophobic surfaces can induce an annular rebound with a limited reduction in contact time. To break this limitation and further reduce contact time, this study focuses on optimizing the singularity number and arrangement. The effects of the singularity number and dimensionless spacing (l* scaled by the droplet diameter) on the dynamic and contact time characteristics of a droplet impacting the superhydrophobic surface are experimentally studied under varying Weber numbers (We). The experimental results indicate that in comparison to the single singularity, two singularities with l* < 1.0 can generate two liquid rings with four lateral liquid subunits due to the impalement at the high We region. Owing to the reduced equivalent diameter of the subunit, increasing We results in a gradually decreased contact time and accordingly breaks the limitation. However, the liquid film cannot be pierced at l* > 1.0 with a limited reduction. Considering the further reducing potential at l* < 1.0, four singularities are explored without a further reduced contact time due to the formed central liquid film. Using an additional central singularity, the central liquid film is pierced promoting its annular rebound. In consequence, five singularities significantly break the limitation in contact time, particularly a 61.7% reduction to the superhydrophobic flat surface at l* < 1.0.

Coalescence-Induced Jumping of Nanodroplets in a Perpendicular Electric Field: A Molecular Dynamics Study.

Coalescence-induced jumping has promised a substantial reduction in the droplet detachment size and consequently shows great potential for heat-transfer enhancement in dropwise condensation. In this work, using molecular dynamics simulations, the evolution dynamics of the liquid bridge and the jumping velocity during coalescence-induced nanodroplet jumping under a perpendicular electric field are studied for the first time to further promote jumping. It is found that using a constant electric field, the jumping performance at the small intensity is weakened owing to the continuously decreased interfacial tension. There is a critical intensity above which the electric field can considerably enhance the stretching effect with a stronger liquid-bridge impact and, hence, improve the jumping performance. For canceling the inhibition effect of the interfacial tension under the condition of the weak electric field, a square-pulsed electric field with a paused electrical effect at the expansion stage of the liquid bridge is proposed and presents an efficient nanodroplet jumping even using the weak electric field.

Vapor Nucleation on Hybrid-Wetting Nanoconvex Surfaces: The Competition between Intrinsic Wettability and Topography.

Hybrid-wetting surfaces with hydrophilic spots reduced from the micrometer to nanometer scale have been confirmed to enhance vapor nucleation while simultaneously minimizing droplet pinning. Given that surface topography also plays a critical role in influencing nucleation characteristics, the effect of competition between intrinsic wettability and topography on nucleation remains unclear when both surface topography and hydrophilic regions approach the critical nucleation size. This work investigated vapor nucleation on two types of hybrid-wetting nanoconvex surfaces. On random hybrid-wetting convex surfaces, the most negative potential energy sites were located at the sides of the convex structures, leading vapor to preferentially nucleate at these locations, consistent with observations on homogeneous surfaces. Despite similar average potential energy values across the surface, wettability variations in hydrophilic and hydrophobic atoms significantly alter the surface energy distribution. As the wettability difference between hydrophilic and hydrophobic atoms increases, stronger hydrophilic atoms generate relatively higher local energy regions, promoting vapor rapid nucleation. The edge effect still exists at a hydrophilic atom ratio of 10%, and competition among hydrophilic spots impedes vapor nucleation and growth. However, when the ratio increases to 40%, the increased surface average potential energy promotes the probability of vapor contacting the surface, leading to rapid vapor nucleation on the sides of the convex structures. In addition, surface potential energy analysis and the Monte Carlo method revealed that nucleation locations on nanoconvex surfaces are governed by the competition between intrinsic wettability and topography. When the magnitude of the potential energy generated by the hydrophilic atoms exceeds that from the topography, stronger solid-liquid interactions at the top of the convex structure increase the likelihood of vapor contacting the surface, resulting in nucleation at the top. Conversely, when the magnitude of the potential energy generated by hydrophilic atoms is lower than that from topography, nucleation preferentially still occurs on the sides.

Enzymolysis kinetics of corn straw by impeded Michaelis model and Box-Behnken design.

Enzymatic hydrolysis is an essential step in the lignocellulosic biorefining process. In this paper, Box-Behnken was used to optimize the enzymatic hydrolysis process of corn stalk, and the promotion effect of three typical surfactants on the enzymatic hydrolysis process was investigated. The experimental results showed that the total reducing sugar yield reached 67.6% under the best-predicted conditions. When the concentration of Tween 80 is 0.1%, it could be increased to 80.2%. In addition, the Impeded Michaels Model (IMM) is introduced in this study to describe the enzymatic hydrolysis process of corn stalks. Finally, the initial contact coefficient between the enzyme and cellulose (Kobs,0) and the gradual loss coefficient of enzyme activity (ki) caused by reaction obstruction were obtained by fitting data, which successfully verified the rationality of the model.

Genome and metabolome analysis of Bacillus sp. Hex-HIT36: A newly screened functional microorganism for the degradation of 1-hexadecene in industrial wastewater.

1-Hexadecene has been detected at a level of mg/L in both influent and effluent of wastewater treatment plants situated in chemical/pharmaceutical industrial parks, which poses a potential threat to the environment. However, few reports are available on aerobic metabolic pathways and microorganisms involved in 1-Hexadecene degradation. In this study, a new strain of 1-Hexadecene-degrading bacteria, Bacillus sp. Hex-HIT36 (HIT36), was isolated from the activated sludge of a wastewater treatment plants located in an industrial park. The physicochemical properties and degradation efficacy of HIT36 were investigated. HIT36 was cultured on a medium containing 1-Hexadecene as a sole carbon source; it was found to remove ∼67% of total organic carbon as confirmed by mass spectrometric analysis of intermediate metabolites. Metabolomic and genomic analysis showed that HIT36 possesses various enzymes, namely, pyruvate dehydrogenase, dihydropolyhydroxyl dehydrogenase, and 2-oxoglutarate-2-oxoiron oxidoreductase (subunit alpha), which assist in the metabolization of readily available carbon source or long chain hydrocarbons present in the growth medium/vicinity. This suggests that HIT36 has efficient long-chain alkane degradation efficacy, and understanding the alkane degradation mechanism of this strain can help in developing technologies for the degradation of long-chain alkanes present in wastewater, thereby assisting in the bioremediation of environment.

The generation and transformation mechanisms of reactive oxygen species in the environment and their implications for pollution control processes: A review.

Reactive oxygen species (ROS), substances with strong activity generated by oxygen during electron transfer, play a significant role in the decomposition of organic matter in various environmental settings, including soil, water and atmosphere. Although ROS has a short lifespan (ranging from a few nanoseconds to a few days), it continuously generated during the interaction between microorganisms and their environment, especially in environments characterized by strong ultraviolet radiation, fluctuating oxygen concentration or redox conditions, and the abundance of metal minerals. A comprehensive understanding of the fate of ROS in nature can provide new ideas for pollutant degradation and is of great significance for the development of green degradation technologies for organic pollutants. At present, the review of ROS generally revolves around various advanced oxidation processes, but lacks a description and summary of the fate of ROS in nature, this article starts with the definition of reactive oxidants species and reviews the production, migration, and transformation mechanisms of ROS in soil, water and atmospheric environments, focusing on recent developments. In addition, the stimulating effects of ROS on organisms were reviewed. Conclusively, the article summarizes the classic processes, possible improvements, and future directions for ROS-mediated degradation of pollutants. This review offers suggestions for future research directions in this field and provides the possible ROS technology application in pollutants treatment.

Enterobacter sp. HIT-SHJ4 isolated from wetland with carbon, nitrogen and sulfur co-metabolism and its implication for bioremediation.

Both autotrophic and heterotrophic denitrification are known as important bioprocesses of microbe-mediated nitrogen cycle in natural ecosystems. Actually, mixotrophic denitrification co-driven by organic matter and reduced sulfur substances are also common, especially in hypoxic environments such as estuarine sediments. However, carbon, nitrogen and sulfur co-metabolism during mixotrophic denitrification in natural water ecosystems has rarely been reported in detail. Therefore, this study investigated the co-metabolism of carbon, nitrogen and sulfur using samples collected from four distinct natural water ecosystems. Results demonstrated that samples from various sources all exhibited the ability for co-metabolism of carbon, nitrogen and sulfur. Microbial community analysis showed that Pseudomonas and Paracoccus were dominant bacteria ranging from 65.6% to 75.5% in mixotrophic environment. Enterobacter sp. HIT-SHJ4, a mixotrophic denitrifying strain which owned the capacity for co-metabolism of carbon, nitrogen and sulfur, was isolated and reported here for the first time. The strain preferred methanol as its carbon source and demonstrated remarkable efficiency for removing sulfide and nitrate with below 100 mg/L sulfide. Under weak acid conditions (pH 6.5-7.0), it exhibited enhanced capability in converting sulfide to elemental sulfur. Its bioactivity was evident within a temperature from 25 °C to 40 °C and C/N ratios from 0.75 to 3. This study confirmed the widespread presence of microbial-mediated synergistic carbon, nitrogen and sulfur metabolism in natural aquatic ecosystems. HIT-SHJ4 emerges as a novel strain, shedding light on carbon, nitrogen and sulfur co-metabolism in natural water bodies. Furthermore, it also serves as a promising candidate microorganism for in-situ ecological remediation, particularly in dealing with contamination posed by nitrate, sulfide, and organic matter.

Biodiversity-safeguarding threshold for urea-fertilizer application on paddy fields: Protozoa-based toxicity tests.

Urea is a widely applied fertilizer to enhance crop yields. Ecological risks associated with the excessive application of urea fertilizer threaten the paddy fields' sustainable agriculture and biodiversity preservation. There are no practical thresholds based on proven data on microbial communities. Protozoa are nitrogen-sensitive organisms. For the first time, this study conducted acute and chronic urea toxicity tests on eight species of organisms. The results indicate that Blepharisma sp. is the most sensitive species to urea exposure and is a suitable indicator for determining the safe threshold of urea. This study estimated the predicted no-effect concentration using species sensitivity distribution curves. Subsequently, it established the threshold for urea application in rice fields based on the fields' area and the surface water's height. The short-term safety threshold for urea in the studied paddy field with black soil is 87.7 mg/L, equivalent to 43.85 kg of urea per hectare for a single nitrogen fertilizer application. The long-term safety threshold is 5.02 mg/L, representing the concentration for re-applicating urea. The biodiversity-safeguarding application threshold provides the basis for developing a urea fertilizer reduction protocol to safeguard the paddy fields' biodiversity.

High-Temperature Wetting and Dewetting Dynamics of Silver Droplets on Molybdenum Surfaces.

The wetting and dewetting behaviors of Ag droplets on Mo(100), Mo(110), and Mo(111) surfaces were investigated over 1200-2000 K via molecular dynamics simulations. We used the diffusion energy barriers of Ag droplets on the three surfaces to analyze the phenomenon of different precursor films and adsorption layers on the different surfaces. Alloying enabled the Mo(111) surface better wettability in both Mo(110) and Mo(111) surfaces, where there were significant precursor films. We observed that the dewetting rate was the fastest on the surface with the densest adsorption layer. Simulations proved that the same molecular kinetic theory model was applicable to not only the wetting process but also the dewetting process on the same surface. We also provided evidence to support the fact that an increased temperature could reduce the time to reach equilibrium for the wetting and dewetting processes.

What Controls the Hole Formation of Nanodroplets: Hydrodynamic or Thermodynamic Instability?

Using molecular dynamics simulations, we investigate the air hole formation of water nanodroplets impacting hydrophilic to hydrophobic surfaces in the range of static contact angles from 30° to 140° with different initial surface temperatures ranging from 300 to 1000 K. We show that the hole dynamics of nanodroplets are different from those observed in millimeter-sized droplets. The hole formation can be observed on smooth surfaces for nanodroplets; however, it only occurs on nonsmooth surfaces for millimeter-sized droplets. We clarify that the hole formation of nanodroplets is triggered by a nucleated vapor bubble due to thermodynamic instability, whereas it is initiated by air bubble entrapment during impact due to hydrodynamic instability for millimeter-sized droplets. The hole formation of nanodroplets relies heavily on the surface temperature and surface wettability, because the nucleated vapor bubble more easily occurs and grows on the surface with high initial temperatures and hydrophobic surfaces. Based on the thermal stability analysis, a criterion is developed to predict the hole formation of nanodroplets, which verifies the dependence of hole formation on the surface temperature and wettability. Furthermore, we show that the ring-bouncing of nanodroplets is triggered by the nucleated vapor bubble. We clarify the reasons for the reduced contact time of nanodroplets caused by the ring-bouncing.

Contact Time of Droplet Impact on Superhydrophobic Cylindrical Surfaces with a Ridge.

This study investigates whether adding ridges to a superhydrophobic cylindrical surface can reduce contact times compared to those of ridged flat or cylindrical surfaces, inspired by the shortened contact time achieved by adding ridges to flat surfaces. The study focuses on studying azimuthal ridges on the cylinder through experimentation, emphasizing the impact dynamics and contact time characteristics under varying We (Weber number) and D* (dimensionless droplet diameter). Within the ultralow Weber number range (ULWR), low Weber number range (LWR), and medium Weber number range (MWR), the contact time is longer than on ridged flat surfaces. In the high Weber number range (HWR), the opposite is observed: increased inertial forces lead to the rupture of the liquid film above the ridges due to Rayleigh-Plateau instability. As a result, the primary droplet splits into two sections with curvature effects promoting its recoiling and rebounding. This study introduces a criterion, defined as C = We/D*, and finds that when C exceeds 2.42, not only is the contact time shorter than on ridged flat or cylindrical surfaces, but it also further decreases with an increase in We or a decrease in D*. The contact time characteristics observed in the HWR offer potential applications in areas such as anti-icing.

Theoretical and Three-Dimensional Molecular Dynamics Study of Droplet Wettability and Mobility on Lubricant-Infused Porous Surfaces.

Profiting from their slippery nature, lubricant-infused porous surfaces endow with droplets excellent mobility and consequently promise remarkable heat transfer improvement for dropwise condensation. To be a four-phase wetting system, the droplet wettability configurations and the corresponding dynamic characteristics on lubricant-infused porous surfaces are closely related to many factors, such as multiple interfacial interactions, surface features, and lubricant thickness, which keeps a long-standing challenge to promulgate the underlying physics. In this work, thermodynamically theoretical analysis and three-dimensional molecular dynamics simulations with the coarse-grained water and hexane models are carried out to explore droplet wettability and mobility on lubricant-infused porous surfaces. Combined with accessible theoretical criteria, phase diagrams of droplet configurations are constructed with a comprehensive consideration of interfacial interactions, surface structures, and lubricant thickness. Subsequently, droplet sliding and coalescence dynamics are quantitatively defined under different configurations. Finally, in terms of the promotion of dropwise condensation, a non-cloaking configuration with the encapsulated state underneath the droplet is recommended to achieve high droplet mobility owing to the low viscous drag of the lubricant and the eliminated pinning effect of the contact line. On the basis of the low oil-water and water-solid interactions, a stable lubricant layer with a relatively low thickness is suggested to construct slippery surfaces.

Contact Time of a Droplet Off-Centered Impacting a Superhydrophobic Cylinder.

Extensive research has shown that a superhydrophobic cylindrical substrate could lead to a noncircumferential symmetry of an impacting droplet, reducing the contact time accordingly. It is of practical significance in applications, such as anti-icing, anticorrosion, and antifogging. However, few accounts have adequately addressed the off-centered impact of the droplet, despite it being more common in practice. This work investigates the dynamic behavior of a droplet off-centered impacting a superhydrophobic cylinder via the lattice Boltzmann method. The effect of the off-centered distance is primarily discussed for droplets taking various Weber numbers and cylinder sizes. The results show that the imposition of an off-center distance can further disrupt the droplet symmetry during the impact. As the off-center distance increases, the droplet movement is gradually tilted toward the offset side until it tangentially passes the cylinder side, resulting in a direct dripping mode. The dynamic features, focusing mainly on maximum spreading in the axial direction and contact time, are specifically explored. A quantitative model of the maximum spreading factor is proposed based on the equivalent transformation from the off-center impact into oblique hitting, considering the full range of off-centered distance. A preliminary contact time model is established for droplet off-centered impacting superhydrophobic cylinders by substituting the maximum spreading and the effective velocity of the liquid moving. This work aims to make an original contribution to the fundamental knowledge of droplet impact and could be of value for related applications.

Electrically Manipulated Vapor Condensation on the Dimpled Surface: Insights from Molecular Dynamics Simulations.

Random vapor nucleation leads to flooding condensation with degraded heat-transfer efficiency. Since an external electric field has a significant effect on manipulating droplets' motion, it is possible to be one of the effective methods to hinder flooding phenomena and improve the heat-transfer rate by applying the external electric field during condensation. However, the motion of nanodroplets is more sensitive to the electric field owing to the scale effect on the nanoscale. The effect of the electric field on growth has not explicitly been comprehended. This work studied the condensation processes on a nanodimpled surface under an electric field with various strengths and directions. The results showed that condensed droplets' growth under the electric field depends on the competition between the electric field force and solid-liquid interactions. Increased vertical electric field strength, the higher torsion by the electric field hindered the motion of vapor, decreased the collision frequency for water molecules with the cooled surface, and elongated the cluster when the electric field force dominates, thus deteriorating the condensation performance. While applying the horizontal electric field, the greater electric field strength leads to better condensation performance by the larger contacting area for heat exchange. A wetting transition induced by the electric field was observed when the electric field strength increased to a certain extent (E > 5.2 × 108 V/m in this study). When the V-shaped surface replaced the dimpled surface as the condensed substrate, the same wetting transition phenomena occurred under a more significant horizontal electric field strength, showing that this method is universal. Besides, different electric field frequencies influenced both the growth and the nucleation, thus exhibiting various condensation performances.

Effect of Asymmetry on the Contact Time of Droplet Impact on Superhydrophobic Cylindrical Surfaces.

Reducing the contact time during the droplet impact on the surface is crucial for anti-icing, self-cleaning, and heat transfer optimization applications. This study aims to minimize the contact time by modifying the surface curvature to create an asymmetric impact process. Our experiments showed that the increase in Weber numbers (We) and the decrease in the ratio of surface diameter to droplet diameter (D*) intensify the asymmetry of the impact process, yielding four distinct rebound modes. Low asymmetry observes the liquid retract toward the central point (Rebound Modes 1 and 2), whereas high asymmetry yields a wing-like rebound (Rebound Modes 3 and 4). In Rebound Mode 1, increased asymmetry would lead to more extended contact due to the prolonged waiting period. Conversely, the reduction in contact time in Rebound Mode 2 occurs due to increased asymmetry with no waiting period. For Rebound Modes 3 and 4, the retraction time could be divided into three stages, generated by two liquid detachment modes from the surface. Analysis reveals that an increased asymmetry would reduce the retraction time during the first stage but prolong it during the third stage, with no significant effects on the second. Four correlations, each pertaining to a distinct impact mode, are proposed based on these analyses to describe the contact time concerning We and D* for droplets impacting a superhydrophobic cylindrical surface.

Photoreactive Mercury-Containing Metallosupramolecular Nanoparticles with Tailorable Properties That Promote Enhanced Cellular Uptake for Effective Cancer Chemotherapy.

A new potential route to enhance the efficiency of supramolecular polymers for cancer chemotherapy was successfully demonstrated by employing a photosensitive metallosupramolecular polymer (Hg-BU-PPG) containing an oligomeric poly(propylene glycol) backbone and highly sensitive pH-responsive uracil-mercury-uracil (U-Hg-U) bridges. This route holds great promise as a multifunctional bioactive nano-object for development of more efficient and safer cancer chemotherapy. Owing to the formation of uracil photodimers induced by ultraviolet irradiation, Hg-BU-PPG can form a photo-cross-linked structure and spontaneously forms spherical nanoparticles in aqueous solution. The irradiated nanoparticles possess many unique characteristics, such as unique fluorescence behavior, highly sensitive pH-responsiveness, and intriguing phase transition behavior in aqueous solution as well as high structural stability and antihemolytic activity in biological media. More importantly, a series of cellular studies clearly confirmed that the U-Hg-U photo-cross-links in the irradiated nanoparticles substantially enhance their selective cellular uptake by cancer cells via macropinocytosis and the mercury-loaded nanoparticles subsequently induce higher levels of cytotoxicity in cancer cells (compared to non-irradiated nanoparticles), without harming normal cells. These results are mainly attributed to cancer cell microenvironment-triggered release of mercury ions from disassembled nanoparticles, which rapidly induce massive levels of apoptosis in cancer cells. Overall, the pH-sensitive U-Hg-U photo-cross-links within this newly discovered supramolecular system are an indispensable factor that offers a potential path to remarkably enhance the selective therapeutic effects of functional nanoparticles toward cancer cells.

Sodium ions removal by sulfuric acid-modified biochars.

Sulfuric acid modifies the biochar derived from corn cobs, stalks, and reeds. Amongst the modified biochar, corn cobs-biochar has the highest BET (101.6 m2 g-1), followed by reeds-biochars (96.1 m2 g-1). The Na+ adsorption capacities for pristine biochars are corn cobs-pristine biochar: 24.2 mg g-1, corn stalks-pristine biochar: 7.6 mg g-1, and reeds-pristine biochar: 6.3 mg g-1, relatively low for field applications. The acid-modified corn cobs biochar has a superior Na+ adsorption capacity of up to 221.1 mg g-1, much higher than literature reports and the other two tested biochars. This corn cobs-modified biochar has also a satisfactory Na+ adsorption capacity (193.1 mg g-1) from actual water collected from a sodium-contaminated city, Daqing, China. The FT-IR spectroscopy and XPS spectrum reveal that the embedded surface -SO3H groups onto the biochar correlate with its superior Na + adsorption, attributable to the ion exchange mechanisms. The biochar surface accessible to sulfonic group grafting can generate a superior Na+ adsorbing surface, which is for the first time reported and has great application potential for the remediation of sodium-contaminated water.

Synthesis of a novel solid mediator Z-scheme heterojunction photocatalysis Fe3O4/C/uio66-nh2: Used for oxidation of Rh6G in water.

A novel mediator Z-scheme photocatalyst, Fe3O4/C/UiO-66-NH2, was designed, synthesized, and characterized using SEM, TEM, FTIR, XRD, EPR, and XPS. Formulas #1 to #7 were examined using dye Rh6G dropwise tests. Carbonization of glucose forms the mediator carbon, which connects two semiconductors, Fe3O4 and UiO-66-NH2, to construct the Z-scheme photocatalyst. Formula #1 generates a composite with photocatalyst activity. The band gap measurements of the constituent semiconductors support the mechanisms for the Rh6G degradation using this novel Z-scheme photocatalyst. The successful synthesis and characterization of the proposed novel Z-scheme confirm the feasibility of the tested design protocol for environmental purposes.

Remediation of the black-odor water body by aquatic plants with plant growth-promoting Rhizobacteria: Lab and pilot tests.

To explore an effective, environmental, rapid operating method to repair black and odor water bodies, water samples and sediment samples collected from a polluted municipal lake in Daqing, China, were directly tested in transparent barrels (10 L). Seven groups of optimizing parameters obtained the optimal operating method, and the max removal rate of COD, NH4+-N, NO3--N, and TP were achieved (89.18%, 59.65%, 69.50%, and 75.61%) by using aquatic plants with plant growth-promoting Rhizobacteria (PGPR). To further verify the method's effectiveness, lager scale tests were conducted based on a water tank (216 L), and similar removal rates were obtained within 48 h. The water quality index and microbial community structure analysis revealed the mechanisms of the interaction among plants, microorganisms, and pollutants and the main biological processes during water body remediation. Finally, the cost of water body remediation by using this method was estimated.

Type-wide biochars loaded with Mg/Al layered double hydroxide as adsorbent for phosphate and mixed heavy metal ions in water.

This study discussed the adsorption of mixed heavy metal ions (Cu2+, Co2+, Pb2+) and phosphate ions by ten pristine biochars and those with precipitated Mg/Al layered double hydroxide (LDH). The pristine biochars have adsorption capacities of 6.9-13.4 mg/g for Cu2+, 1.1-9.7 mg/g for Co2+, 7.8-20.7 mg/g for Pb2+, and 0.8-4.9 mg/g for PO43-. The LDH-biochars have markedly increased adsorption capacities of 20.4-25.8 mg/g for Cu2+, 8.6-15.0 mg/g for Co2+, 26.5-40.4 mg/g for Pb2+ with mixed metal ions, and 13.0-21.8 mg/g for PO43-. Part of the Mg ions but Al ions are released from the LDH-biochars during adsorption, counting less than 7.2% of the adsorbed ions. The pristine biochars have specific adsorption sites for Cu2+ and Co2+, separate Pb2+ sites related to ether groups on biochar, and areal-dependent sites for PO43-. There is no universal adsorption mechanism corresponding to mixed metal ion adsorption for individual pristine biochar involving different contributions of C-O-C, C-O-H, and CO groups and graphitic-N, pyrrolic-N, and pyridine-N groups. The LDH complexes with hydroxyl and carbonyl groups of biochar, and the LDH interacts with biochar's ether groups, which contributes to metal adsorption, against the conception that the biochar is merely a carrier of LDH as adsorbents.