Role of urea in the retention of DON in soil by clay minerals: Analysis based upon molecular weight.

As a widely used fertilizer, urea significantly promotes the leaching of dissolved organic nitrogen (DON) in soils and aggravates nitrogen contamination in groundwater. Clay minerals are considered the most important factor in retaining DON. However, the effect of urea on the retention of DON with different molecular weights by clay minerals is unknown. In this study, the retention of both low-molecular weight DON (LMWD) and high-molecular weight DON (HMWD) by clay minerals in the presence of urea was investigated. For this purpose, batch adsorption and soil column leaching experiments, characterization analysis (Fourier transform infrared spectroscopy X-ray diffraction, and X-ray photoelectron spectroscopy), and molecular dynamics simulations were carried out. Urea had a positive effect on the adsorption of LMWD, whereas a competitive effect existed for the adsorption of HMWD. The dominant interactions among DON, urea, and clay minerals included H-bonding, ligand exchange, and cation exchange. The urea was preferentially adsorbed on clay minerals and formed a complex, which provided more adsorption sites to LMWD and only a few to HMWD. The presence of urea increased the retention of LMWD and decreased the retention of HMWD in clay minerals. The retention capacity of LMWD increased by 6.9%-12.8%, while that of HMWD decreased by 6.7%-53.1%. These findings suggest that LMWD tended to be trapped in soils, while HMWD was prone to be leached into groundwater, which can be used to evaluate the leaching of DON from soil to groundwater.

Simple preparation of nitenpyram-intercalated clay nanosheets with reduced leaching risk and improved safety to insect pollinators.

Neonicotinoids, highly toxic to insects, are among the world's most used insecticides. However, their harmful effects on pollinators like honeybees and potential to contaminate water bodies have drawn significant criticism. Herein, a nanopesticide, NTP@LDH, was developed by intercalating the model neonicotinoid insecticide nitenpyram (NTP) within layered double hydroxide (LDH) materials using a simple one-pot method. The NTP@LDH showed a nano-sized sheet structure, with an average particle size of 206.2 nm and a loading capacity of 14.6 %. The release rate of NTP@LDH under acidic conditions was higher than that under alkaline or neutral conditions. The photodegradation capacity and insecticidal activity of NTP were unaffected by intercalation in LDH. Importantly, NTP@LDH could significantly enhance the foliar adhesive properties of NTP, retard its leaching through the soil, and improve its safety for honeybees. Moreover, LDH was safe for crops and can improve their growth. This work provides a promising strategy with a simple procedure that could reduce leaching risks of neonicotinoids while concurrently enhancing their safety to pollinating creatures.

Specific ion effects on the soil shear strength and clay surface properties of collapsing wall in Benggang.

Benggangs are a special type of soil erosion in the hilly granite regions of the tropical and subtropical areas of Southern China. They cause severe soil and water loss, which can severely deteriorate soil quality and threat to the local ecological environment. Soils (red soil, sandy soil and detritus soil) were collected from collapsing wall of a typical Benggang in Changting County of Fujian Province, and their physicochemical and mineralogical properties were analyzed. Five different monovalent cations were used to saturate the soil samples to examine the specific ion effects on the shear strength and clay surface properties. Red soil had a higher clay content, plastic limit, liquid limit and shear strength than sandy soil and detritus soil. The studied soils mainly consisted of kaolinite, hydroxy-interlayer vermiculite, illite and gibbsite clay minerals. The soils saturated with K+, NH4 +and Cs+ had greater cohesion than the Li+- and Na+-saturated soils, e.g., the cohesion of the red soil saturated with Li+, K+, NH4 + and Cs+ cations were 1.05, 1.23, 1.45 and 1.20 times larger than that of the Na+-saturated soil, respectively. While the internal friction angle was slightly different, which indicated that different monovalent cations affected the shear strength differently. K+-, NH4 +- and Cs+-saturated clay particles had higher zeta potentials and thinner shear plane thicknesses than Li+- and Na+-saturated clay particles and showed strong specific ion effects on the clay surface properties. The changes in clay surface properties strongly affected the soil mechanical properties. Soils saturated with K+, NH4 + and Cs+ could increase the shear strength, and then increase the stability of the collapsing wall, thus might decrease the erosion intensity of Benggang. The results provide a scientific basis for the interpretation of and practical treatment of Benggang.

Insights into the differential removal of various red tide organisms using modified clay: Influence of biocellular properties and mechanical interactions.

In recent years, red tides have increased worldwide in frequency, intensity, involving a higher number of causative species during the events. As the most commonly used method for control of red tides, modified clay (MC) was found to have differential ability to remove various red tide species. However, the underlying mechanisms have not yet been completely elucidated. In this study, the use of MC to remove three typical disaster-causing species, Aureococcus anophagefferens, Prorocentrum donghaiense and Heterosigma akashiwo, was investigated, and differential removal of these species was probed with insights into their biocellular properties and mechanical interactions. The results showed that removal efficiencies of the three species by MC decreased in the order P. donghaiense > A. anophagefferens > H. akashiwo, while the sedimentation rates decreased in the order H. akashiwo > P. donghaiense > A. anophagefferens. Analyses of the cell surface properties and redundancy analysis (RDA) revealed that the highest surface zeta potential of -5.32±0.39 mV made P. donghaiense the most easily removed species; the smallest cell size of 3.30±0.03 µm facilitated the removal of A. anophagefferens; and the highest hydrophobicity with a H2O surface contact angle of 98.50±4.31° made the removal of H. akashiwo difficult. X-ray photoelectron spectroscopy (XPS) data indicated that the electronegativity of P. donghaiense was caused by carboxyl groups and phosphodiester groups, and the hydrophobicity of H. akashiwo was associated with a high C-(C, H) content on the cell surface. According to the extended Derjaguin, Landau, Verwey, and Overbeek (ex-DLVO) theory calculation, differences in the interaction energies between MC and the three red tide species effectively explained their different sedimentation rates. In addition, the degree of oxidative damage caused by MC to the three red tide species differed, which also affected the removal of red tide organisms.

Halloysite functionalized with dendritic moiety containing vitamin B1 hydrochloride as a bio-based catalyst for the synthesis of 5-hydroxymthylfurfural.

Using halloysite clay and vitamin B1 hydrochloride, a novel acidic halloysite-dendrimer catalytic composite has been developed for conversion of fructose to 5-hydroxymthylfurfural. To grow the dendritic moiety on halloysite, it was first functionalized and then reacted with melamine, epichlorohydrin and vitamin B1 hydrochloride respectively. Then, the resulting composite was treated with ZnCl2 to furnish Lewis acid sites. Use of vitamin B1 as the cationic moiety of ionic liquid obviated use of toxic chemicals and resulted in more environmentally friendly composite. Similarly, dendritic moiety of generation 2 was also grafted on halloysite and the activity of both catalysts for conversion of fructose to 5-hydroxymthylfurfural was investigated to disclose the role of dendrimer generation. For the best catalytic composite, the reaction variables were optimized via RSM and it was revealed that use of 0.035 g catalyst per 0.1 g fructose at 95 °C furnished HMF in 96% yield in 105 min. Turnover numbers (TONs) and frequencies (TOFs) were estimated to be 10,130 and 5788 h-1, respectively. Kinetic studies also underlined that Ea was 22.85 kJ/mol. The thermodynamic parameters of Δ H ≠ , Δ S ≠ and Δ G ≠ , were calculated to be 23 kJ/mol, - 129.2 J/mol and 72.14 kJ/mol, respectively. Notably, the catalyst exhibited good recyclability and hot filtration approved heterogeneous nature of catalysis.

Adsorption and ion exchange of toxic metals by Brazilian clays: clay selection and studies of equilibrium, thermodynamics, and binary ion exchange modeling.

In this study, four Brazilian clays (Bofe, Verde-lodo, commercial Fluidgel, and expanded commercial vermiculite) were evaluated for their adsorptive capacity and removal percentage in relation to different toxic metals (Ni2+, Cd2+, Zn2+, and Cu2+). The best results were obtained by expanded vermiculite, with cadmium removal reaching values of 95%. The most promising clay was modified by the sodification process, and the metal cadmium was used to evaluate the ion exchange process. The clays expanded vermiculite (EV) and VNa-sodified vermiculite were evaluated by equilibrium study at 25, 35, and 45 °C. At 25 °C, EV obtained a maximum adsorption capacity of 0.368 mmol/g and sodified vermiculite 0.480 mmol/g, which represents an improvement of 30.4% in modified clay capacity. At 45 °C, the sodified vermiculite reached 0.970 mmol/g adsorption capacity. The Langmuir, Redlich-Peterson Freundlich, and Dubinin-Raduskevich models were adjusted to the results. Langmuir provided the best fit among the models. The thermodynamic quantities (ΔS, ΔH, and ΔG) demonstrated that the process is spontaneous and endothermic and the metal is captured by physisorption and chemisorption in the studied temperature range. For the ion exchange equilibrium, the binary Langmuir and binary Langmuir-Freundlich models were adjusted to the expanded vermiculite and sodified vermiculite isotherms, respectively. Both models were predictive. Thermal analysis indicated good heat resistance even after material modification. The apparent and real densities demonstrated that after each treatment or contamination, the clayey material undergoes contraction in its structure. An improved efficiency of the adsorbent was found after sodification.

Deciphering geochemical fingerprints and health implications of groundwater fluoride contamination in mica mining regions using machine learning tactics.

The contribution of mica mining activities to fluoride (F-) contamination in groundwater has been chased in this study. For the purpose, groundwater samples (n = 40, replicated thrice) were collected during the post-monsoons (September-October) from a mica mining area in the Tisri block of Giridih district, Jharkhand. The study has employed a synergy of classical aquifer chemistry, statistical approaches, different indices, Self-Organising Maps (SOM), and Sobol sensitivity index (SSI) to unveil the underlying aquifer chemistry, identify the impacts of mining activities on groundwater quality and its associated health hazard. Fluoride levels varied from 0.34 to 2.8 ppm, with 40% of samples exceeding the World Health Organization's permissible limit (1.5 ppm). Physicochemical analysis revealed significant differences in electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH) and major ion concentrations (Na+, HCO3-, Ca2+) between fluoride-contaminated (FC) and fluoride-uncontaminated (FU) groups. Higher Na+ and HCO3- associated with F- contaminated samples, were indicative of silicate weathering and carbonate dissolution as primary geogenic sources for this ion. Health risk assessment (HRA) revealed hazard quotient (HQ) values exceeding unity, indicating non-carcinogenic risks, particularly for children in most samples from group FC. The mean Water Quality Index (WQI) of FC group (156.76 ± 7.30) was significantly higher (p < 0.05) than group FU indicating of its unsuitability. SOM could accurately (80%) predict presence of fluoride in water samples based on other major ions. Sobol sensitivity analysis successfully identified fluoride concentration and body weight as most impactful parameters affecting human health. The integration of advanced modelling techniques and geospatial analysis as Inverse Distance Weightage (IDW) maps has provided a robust framework for ongoing groundwater quality monitoring in mining-affected regions and can help proactive intervention in risk-prone areas. Overall, this comprehensive study takes us a step ahead towards ensuring safe drinking water access for the global community.

Modification of polymethylmethacrylate bone cement with halloysite clay nanotubes.

BACKGROUND: Polymethylmethacrylate (PMMA) bone cement is used in orthopedics and dentistry to get primary fixation to bone but doesn't provide a mechanically and biologically stable bone interface. Therefore, there was a great demand to improve the properties of the PMMA bone cement to reduce its clinical usage limitations and enhance its success rate. Recent studies demonstrated that the addition of halloysite nanotubes (HNTs) to a polymeric-based material can improve its mechanical and thermal characteristics. OBJECTIVES: The purpose of the study is to assess the compressive strength, flexural strength, maximum temperature, and setting time of traditional PMMA bone cements that have been manually blended with 7 wt% HNT fillers. METHODS: PMMA powder and monomer liquid were combined to create the control group, the reinforced group was made by mixing the PMMA powder with 7 wt% HNT fillers before liquid mixing. Chemical characterization of the HNT fillers was employed by X-ray fluorescence (XRF). The morphological examination of the cements was done using a scanning electron microscope (SEM). Analytical measurements were made for the compressive strength, flexural strength, maximum temperature, and setting time. Utilizing independent sample t-tests, the data was statistically assessed to compare mean values (p < 0.05). RESULTS: The findings demonstrated that the novel reinforced PMMA-based bone cement with 7 wt% HNT fillers showed higher mean compressive strength values (93 MPa) and higher flexural strength (72 MPa). and lower maximum temperature values (34.8 °C) than the conventional PMMA bone cement control group, which was (76 MPa), (51 MPa), and (40 °C), respectively (P < 0.05). While there was no significant difference in the setting time between the control and the modified groups. CONCLUSION: The novel PMMA-based bone cement with the addition of 7 wt% HNTs can effectively be used in orthopedic and dental applications, as they have the potential to enhance the compressive and flexural strength and reduce the maximum temperatures.

Research on the expansion, shrinkage properties and fracture evolution of red clay stabilised with phosphogypsum under dry-wet cycles.

In view of the special engineering properties of red clay and the waste of phosphogypsum resources, the expansion and contraction deformation and fissure evolution of phosphogypsum stabilized red clay under different conditions were investigated by laboratory tests and image processing system. The research results show that: (1) the absolute expansion and absolute shrinkage of phosphogypsum stabilized red clay are positively correlated with the compaction degree, the number of dry and wet cycles and the cement dosage, and negatively correlated with the initial water content and the phosphogypsum dosage; (2) the fissure rate increases with the increase of the number of dry and wet cycles, and decreases with the increase of the initial water content, the compaction degree, the cement, and the phosphogypsum dosage; (3) The relationship among absolute expansion rate (absolute shrinkage), degree of compaction and fracture rate can be fitted by the equation f(x,y) = ax+by+cx2+dy2+e; (4) Phosphogypsum has an obvious inhibiting effect on the expansion, shrinkage and cracking of the mix. It is recommended that the cement mixing amount of 6% and phosphogypsum: red clay = 1:1~1:2 as roadbed filler.

Molecular Insights into Adhesion at Interface of Geopolymer Binder and Cement Mortar.

The degradation of concrete and reinforced concrete structures is a significant technical and economic challenge, requiring continuous repair and rehabilitation throughout their service life. Geopolymers (GPs), known for their high mechanical strength, low shrinkage, and durability, are being increasingly considered as alternatives to traditional repair materials. However, there is currently a lack of understanding regarding the interface bond properties between new geopolymer layers and old concrete substrates. In this paper, using advanced computational techniques, including quantum mechanical calculations and stochastic modeling, we explored the adsorption behavior and interaction mechanism of aluminosilicate oligomers with different Si/Al ratios forming the geopolymer gel structure and calcium silicate hydrate as the substrate at the interface bond region. We analyzed the electron density distributions of the highest occupied and lowest unoccupied molecular orbitals, examined the reactivity indices based on electron density functional theory, performed Mulliken charge population analysis, and evaluated global reactivity descriptors for the considered oligomers. The results elucidate the mechanisms of local and global reactivity of the oligomers, the equilibrium low-energy configurations of the oligomer structures adsorbed on the surface of C-(A)-S-H(I) (100), and their adsorption energies. These findings contribute to a better understanding of the adhesion properties of geopolymers and their potential as effective repair materials.

A combination of physiology, metabolomics, and genetics reveals the two-component system ResS/ResR-mediated Fe and Al release from biotite by Pseudomonas pergaminensis F77.

Understanding of the mechanisms on bacteria-regulated mineral dissolution functions is important for further insight into mineral-microbe interactions. The functions of the two-component system have been studied. However, the molecular mechanisms involved in bacterial two-component system-mediated mineral dissolution are poorly understood. Here, the two-component regulatory system ResS/ResR in the mineral-solubilizing bacterium Pseudomonas pergaminensis F77 was characterized for its involvement in biotite dissolution. Strain F77 and the F77ΔresS, F77ΔresR, and F77ΔresS/R mutants were constructed and compared for the ResS/ResR system-mediated Fe and Al release from biotite in the medium and the mechanisms involved. After 3 days of incubation, the F77ΔresS, F77ΔresR, and F77ΔresS/R mutants significantly decreased the Fe and Al concentrations in the medium compared with F77. The F77ΔresS/R mutant had a greater impact on Fe and Al release from biotite than did the F77ΔresS or F77ΔresR mutant. The F77∆resS/R mutant exhibited significantly reduced Fe and Al concentrations by 21-61 % between 12 h and 48 h of incubation compared with F77. Significantly increased pH values and decreased cell counts on the mineral surfaces were found in the presence of the F77∆resS/R mutant compared with those in the presence of F77 between 12 h and 48 h of incubation. Metabolomic analysis revealed that the extracellular metabolites associated with biotite dissolution were downregulated in the F77ΔresS/R mutant. These downregulated metabolites included GDP-fucose, 20-carboxyleukotriene B4, PGP (16:1(9Z)/16:0), 3',5'-cyclic AMP, and a variety of acidic metabolites involved in carbohydrate, amino acid, and lipid metabolisms, glycan biosynthesis, and cellular community function. Furthermore, the expression levels of the genes involved in the production of these metabolites were downregulated in the F77ΔresS/R mutant compared with those in F77. Our findings suggested that the ResS/ResR system in F77 contributed to mineral dissolution by mediating the production of mineral-solubilizing related extracellular metabolites and bacterial adsorption on mineral surface.

Real-time single-molecule observation of incipient collagen fibrillogenesis and remodeling.

The hierarchic assembly of fibrillar collagen into an extensive and ordered supramolecular protein fibril is critical for extracellular matrix function and tissue mechanics. Despite decades of study, we still know very little about the complex process of fibrillogenesis, particularly at the earliest stages where observation of rapidly forming, nanoscale intermediates challenges the spatial and temporal resolution of most existing microscopy methods. Using video rate scanning atomic force microscopy (VRS-AFM), we can observe details of the first few minutes of collagen fibril formation and growth on a mica surface in solution. A defining feature of fibrillar collagens is a 67-nm periodic banding along the fibril driven by the organized assembly of individual monomers over multiple length scales. VRS-AFM videos show the concurrent growth and maturation of small fibrils from an initial uniform height to structures that display the canonical banding within seconds. Fibrils grow in a primarily unidirectional manner, with frayed ends of the growing tip latching onto adjacent fibrils. We find that, even at extremely early time points, remodeling of growing fibrils proceeds through bird-caging intermediates and propose that these dynamics may provide a pathway to mature hierarchic assembly. VRS-AFM provides a unique glimpse into the early emergence of banding and pathways for remodeling of the supramolecular assembly of collagen during the inception of fibrillogenesis.

Intermolecular Electrostatic Interactions in Cytochrome c Protein Monolayer on Montmorillonite Alumosilicate Surface: A Positive Cooperative Effect.

Montmorillonite (MM) crystal nanoplates acquire anticancer properties when coated with the mitochondrial protein cytochrome c (cytC) due to the cancer cells' capability to phagocytize cytC-MM colloid particles. The introduced exogenous cytC initiates apoptosis: an irreversible cascade of biochemical reactions leading to cell death. In the present research, we investigate the organization of the cytC layer on the MM surface by employing physicochemical and computer methods-microelectrophoresis, static, and electric light scattering-to study cytC adsorption on the MM surface, and protein electrostatics and docking to calculate the local electric potential and Gibbs free energy of interacting protein globules. The found protein concentration dependence of the adsorbed cytC quantity is nonlinear, manifesting a positive cooperative effect that emerges when the adsorbed cytC globules occupy more than one-third of the MM surface. Computer analysis reveals that the cooperative effect is caused by the formation of protein associates in which the cytC globules are oriented with oppositely charged surfaces. The formation of dimers and trimers is accompanied by a strong reduction in the electrostatic component of the Gibbs free energy of protein association, while the van der Waals component plays a secondary role.

Feasibility of composted green waste amended by vermiculite and earthworm casts as the growth media for three common ornamental plants.

This study demonstrated the effects of adding specific proportions of vermiculite (VMT: 0%, 10%, and 20%) and earthworm casts (EWCs: 0%, 10%, and 20%) on the physico-chemical properties of composted green waste (CGW), and the impacts of amended CGW as growth media on the growth of three common ornamental plants (Dahlia pinnata Cav. [dahlia], Centaurea cyanus L. [cornflower], and Consolida ajacis [L.] Schur [delphinium]). Compared with Treatment T1 (CK), the addition of 10% VMT and 20% EWCs greatly (p < 0.05) increased the total porosity, aeration porosity, water-holding porosity, total nitrogen, available phosphorus, available potassium, and organic matter of CGW by 9%, 35%, 4%, 18%, 27%, 13%, and 33%, respectively. In addition, this pattern increased (p < 0.05) the total fresh biomass, total chlorophyll content, and root length of dahlias by 9%, 19%, and 27%, respectively; those of cornflowers by 17%, 30%, and 29%, respectively (p < 0.05); and those of delphiniums by 23%, 14%, and 63%, respectively. Therefore, the amended CGW supplemented with 10% VMT and 20% EWCs was an ideal growth medium for the three plants.

In Situ Evolution of Ionic Sites at Clay Mineral Interfaces Facilitates Fluoride and Phosphorus Mineralization.

Soil minerals influence the biogeochemical cycles of fluoride (F) and phosphorus (P), impacting soil quality and bioavailability to plants. However, the cooperative mechanisms of soil minerals in governing F and P in the soil environment remain a grand challenge. Here, we reveal the essential role of a typical soil mineral, montmorillonite (Mt), in the cycling and fate of F and P. The results show that the enrichment of metal sites on the Mt surface promotes the mineralization of F to the fluorapatite (FAP) phase, thereby remaining stable in the environment, simultaneously promoting P release. This differential behavior leads to a reduction in the level of F pollution and an enhancement of P availability. Moreover, solid-state NMR and HRTEM observations confirm the existence of metastable F-Ca-F intermediates, emphasizing the pivotal role of Mt surface sites in regulating crystallization pathways and crystal growth of FAP. Furthermore, the in situ atomic force microscopy and theoretical calculations reveal molecular fractionation mechanisms and adsorption processes. It is observed that a competitive relationship exists between F and P at the Mt interface, highlighting the thermodynamically advantageous pathway of forming metastable intermediates, thereby governing the activity of F and P in the soil environment at a molecular level. This work paves the way to reveal the important role of clay minerals as a mineralization matrix for soil quality management and offers new strategies for modulating F and P dynamics in soil ecosystems.

Products from Photolysis Reactions of Tetracycline Mediated by Clay and Humic Substance Induce Contrasting Expressions of Target Resistance Genes.

Phototransformation is a key process affecting the fate of many antibiotics in the environment, but little is known about whether their photoproducts exert selective pressure on bacteria by inducing antibiotic resistance genes (ARGs). Here, we examined the expression of tetracycline resistance gene tet(M) of a fluorescent Escherichia coli whole-cell bioreporter influenced by the phototransformation of tetracycline. The presence of suspended smectite clay (montmorillonite or hectorite, 1.75 g/L) or dissolved humic substance (Pahokee Peat humic acid or Pahokee peat fulvic acid, 10 mg C/L) in aqueous solutions markedly facilitated the transformation of tetracycline (initially at 400 µg/L) with half-life shortened by 1.4-2.6 times. Despite the similar phototransformation ratios (80-90%) of the total loaded tetracycline after 60 min irradiation, the decreased ratios of cell fluorescence intensity (which was proportional to the expression amount of ARG tet(M)) were much higher with the two clays (94 and 93%) than with the two humic substances (44 and 69%) when compared to the respective dark controls. As illustrated by mass spectroscopic and chemical analyses, tetracycline was proposed to be mainly transformed to amide (ineffective in inducing ARGs) with the presence of clays by reaction with self-photosensitized singlet oxygen (1O2), while the humic substances might catalyze the production of another two demethylated and/or deaminated compounds (still effective in inducing ARGs) in addition to the amide compound via reaction with triplet excited state dissolved organic matter (3DOM*). As clay minerals and humic substances are important soil constituents and ubiquitously present in surface environments, the observed clay and humic-dependent photooxidation pathways of tetracycline and the differing selective pressures of the associated products highlight the need for monitoring the transformation compounds of antibiotics and provide critical insight into the development of antibiotic treatment protocols.

Adsorption of cadmium (II) on organic xerogel microspheres: effect of adding sepiolite or vermiculite and operating conditions on the adsorption capacity.

The organic xerogel (OX) was synthesized through sol-gel polymerization of formaldehyde and resorcinol in inverse emulsion using Na2CO3 as a catalyst. Meanwhile, OX containing sepiolite (OX-Sep) and vermiculite (OX-Ver) were prepared similarly to OX but adding clays during synthesis. All materials were mesoporous and presented spherical morphology, and the surface of these materials exhibited an acidic character because the concentration of acidic sites was higher than those of basic sites. Cd(II) adsorption from aqueous solutions onto OX, OX-Sep, and OX-Ver was examined, and the OX-Sep showed the highest adsorption capacity towards Cd(II) of 189.7 mg/g, being 1.5, 2, and 36 times higher than that of OX-Ver, OX, and Sep. The OX-Sep capacity for adsorbing Cd(II) was significantly lessened by decreasing the pH from 7 to 4 and raising the ionic strength from 0.01 N to 0.1 N. This trend was ascribed to electrostatic attraction between the Cd+2 in water and the negatively charged surface of OX-Sep. Besides, desorption studies at pH 4 showed that the average desorption percentage of Cd(II) adsorbed on OX-Sep was 80%. The characterization results and the effect of the operating conditions on the adsorption capacity proved that electrostatic attraction and cation exchange play a crucial role in the adsorption mechanism.

Kinetic and competitive effects of sorption on multi-element migration through crushed granite and biotite gneiss in Ca-HCO3-SO4 type groundwater.

Crystalline rock is used as the host rock for the disposal of high-level radioactive waste. Two cationic elements (Cs(I) and Ni(II)) and three anionic elements (Se(IV/VI), Mo(VI), and U(VI)) were selected to comprehensively evaluate the sorption behaviors of these radionuclides on crystalline granite and biotite gneiss. The anionic elements showed weak sorption (log Kd (L·kg-1) < 1) and little competition effect, while the cationic elements (log Kd (L·kg-1) = 2-3) showed clear competition (18-98% in Kd values) even at low concentrations. Analysis by pseudo-second-order kinetics showed that Cs(I) sorbed at similar rates on both rocks (20% faster on biotite gneiss), but Ni(II) sorbed 190% faster on biotite gneiss than on granite. That is why the retardation factors for Cs(I) and Ni(II) were reversed in the biotite gneiss column compared to their distribution coefficients. Therefore, the sorption kinetics cannot be neglected in groundwater systems with high flow rates. In the desorption column test, the retardation followed the order of the distribution coefficient. The desorption column test revealed that the distribution coefficient determines the strength of sorption on crystalline rocks.

Applications of phase-separating multi-bilayers in protein-membrane domain interactions.

Synthetic model membranes are important tools to elucidate lipid domain and protein interactions due to predefined lipid compositions and characterizable biophysical properties. Here, we introduce a model membrane with multiple lipid bilayers (multi-bilayers) stacked on a mica substrate that is prepared through a spin-coating technique. The spin-coated multi-bilayers are useful in the study of phase separated membranes with a high cholesterol content, mobile lipids, microscopic and reversible phase separation, and easy conjugation with proteins, which make them a good model to study interactions between proteins and membrane domains.

Bottlebrush Polymers for Articular Joint Lubrication: Influence of Anchoring Group Chemistry on Lubrication Properties.

The role of carboxylic, aldehyde, or epoxide groups incorporated into bottlebrush macromolecules as anchoring blocks (or cartilage-binding blocks) is investigated by measuring their lubricating properties and cartilage-binding effectiveness. Mica modified with amine groups is used to mimic the cartilage surface, while bottlebrush polymers functionalized with carboxylic, aldehyde, or epoxide groups played the role of the lubricant interacting with the cartilage surface. We demonstrate that bottlebrushes with anchoring blocks effectively reduce the friction coefficient on modified surfaces by 75-95% compared to unmodified mica. The most efficient polymer appears to be the one with epoxide groups, which can react spontaneously with amines at room temperature. In this case, the value of the friction coefficient is the lowest and equals 0.009 ± 0.001, representing a 95% reduction compared to measurements on nonmodified mica. These results show that the presence of the functional groups within the anchoring blocks has a significant influence on interactions between the bottlebrush polymer and cartilage surface. All synthesized bottlebrush polymers are also used in the preliminary lubrication tests carried out on animal cartilage surfaces. The developed materials are very promising for future in vivo studies to be used in osteoarthritis treatment.