Increase In Ion Concentration Research Articles

Effects of saline water with different concentrations of calcium and magnesium ions on emitter clogging in drip irrigation integrated water–fertilizer system

AbstractThe application of saline water in drip irrigation is severely constrained due to its high salt content, which causes precipitation and emitter clogging. Therefore, the effects of calcium and magnesium ions at 100, 150 and 200 mg/L in saline water coupled with humic acid nitrogen fertilizer on emitter clogging were studied. Compared with ground saline water, all treatments significantly increased the emitter clogging risk. In the calcium and magnesium ion treatment groups, clogging fouling increased by 23.94–58.35 and 14.55–51.21 mg/cm2, the discharge variation ratio (Dra) decreased by 22%–59% and 14%–49%, and the Christiansen coefficient of uniformity (CU) decreased by 29%–79% and 15%–74%, respectively. Higher ion concentrations caused more clogging. Saline water with a high calcium content caused more clogging. Under similar concentration conditions, the Dra and CU in high magnesium saline water were 9%–32% and 8%–51% higher, respectively. In addition, the increase in magnesium ion concentration changed the crystal form of carbonate, slowed the formation rate of precipitated dirt and significantly reduced the carbonate content by 19%–40%. Our results provide support for the popularization of saline water drip irrigation systems.

Energy transfer mechanisms and non-radiative losses in Nd3+ doped phosphate laser glass: Dopant concentration effect study

The aim of the present work is to show a simple quantitative theoretical study on the relaxation mechanisms of the 4F3/2 levels of the Nd3+ ions in the widely used meta-phosphate laser glass system (P2O5–Al2O3–BaO–K2O) for the studied concentration range of the Nd3+ ions from 0.10 × 1020 to 8.15 × 1020 ions/cm3. Auzel's diffusion-limited model for energy transfer has been adopted in the present study for estimating zero concentration level lifetime, τ0 of 4F3/2 levels in the Nd3+ ions present in the studied glass matrix. Primarily, the relaxation mechanisms are dominated by radiative decay (krad) and energy transfer to hydroxyl groups (kOH) present in the glass network structure up to the dopant, Nd3+ concentration 0.78 × 1020 ions/cm3. Later on, with increasing dopant ion concentration, fluorescence from trivalent Nd3+ ions is unfortunately quenched by the interaction between Nd3+ ions, also known as concentration quenching. The concentration quenching of the fluorescence lifetime has been analysed using proposed Inokuti-Hirayama (I–H), Yokota-Tanimoto (Y-T) and Brushtein (B) models and found to be migration-assisted cross-relaxation mechanisms at or beyond 1.47 × 1020 ions/cm3 dopant concentration. The diffusion coefficient, D derived from the Y-T model and the energy migration rate, Wm attained from the B model has demonstrated diffusion-based energy migration initially at about >1.47 × 1020 ions/cm3 Nd3+ concentration and after that, it has switched to a hopping mechanism with further increasing ion concentration, >2.97 × 1020 ions/cm3. Critical quenching concentration, Q and critical radius, R0 for the studied glass composition have also been determined and correlated to the experimental results. No evidence for ion clustering has been found within the studied dopant ion concentration range (0.10 × 1020 - 8.15 × 1020) ions/cm3 with respect to the estimated R0. Finally, the contribution of the individual relaxation process to the experimentally recorded emission spectra and measured lifetime, τexp has been investigated in order to identify the most suitable Nd3+ ion concentration for developing large-aperture high-energy/high-peak-power lasers and optical amplifiers. Therefore, the present work is expected to be significant in aiding to formulate an effective glass composition for construction of compact high-power lasers and optical amplifiers.

Glass transition temperature of styrene‐based ionomer controlled over a very wide temperature range by nonpolar plasticizer content and ion content

AbstractThe plasticization effect by the addition of nonpolar bis(2‐ethylhexyl) phthalate (dioctyl phthalate) (DOP) on the glass transition temperatures (Tgs) of poly(styrene‐Na methacrylate) (PSMANa) ionomers was investigated. The matrix Tg (Tg,m) and cluster Tg (Tg,c) of the ionomers dropped linearly as the DOP content in the PSMANa ionomers enhanced, only when the phase separation of DOP did not occur. Since the Tg,m and Tg,c of the ionomer increased somewhat linearly with increasing ion content of the ionomer, simple equations were obtained to express the Tgs of the ionomers using the ion contents (x mol%) and the DOP contents (y wt%) of the ionomers; Tg,m (°C) = 121 + 3.0x + 2.8y and Tg,c (°C) = 171 + 6.3x + 2.6y. According to the x‐ray scattering results, for the ionomer containing 6.4 mol% of ions, the distance between scattering centers increased from 21 to 22 Å when ca. 40 wt% of DOP was added. This suggested that the DOP promoted the mobility of the styrene chains, enhancing the formation of multiplets. On the other hand, for the ionomer containing 22.4 mol% of ions, when ca. 40 wt% was added, the distance between multiplets widened from 18 to 21 Å.

Prediction of interference current of buried pipeline and study on corrosion of Q235A steel

Interference current will cause severe electrochemical corrosion to buried pipes. However, the interference current flowing into the buried pipeline cannot be directly measured, and the influence of interference current on the corrosion of the buried pipeline cannot be directly observed. In this paper, the combined analysis methods of finite element analysis, partial least square method and electrochemical measurement technique are used to predict the interference current of buried pipeline and to study the effect of dynamic interference current and chloride ion concentration on the corrosion of Q235A steel. The prediction results show that increasing the input variables of the prediction model and changing the position of the input variables can effectively improve the accuracy of the model. Electrochemical measurements show that an increase in chloride ion concentration increases the corrosion current density in the polarization curve of Q235A steel and decreases the capacitive reactance arc radius in the electrochemical impedance spectroscopy. In addition, on the basis of the rail-to-ground potential monitoring points in the actual project, the number of rail-to-ground potential monitoring points was increased to improve the prediction accuracy of the buried pipeline interference currents, which indicates that the analysis method is an effective way to monitor and evaluate the influence of stray currents on the corrosion of buried pipelines.

Salinization and sedimentation drive contrasting assembly mechanisms of planktonic and sediment-bound bacterial communities in agricultural streams.

Agriculture is the most dominant land use globally and is projected to increase in the future to support a growing human population but also threatens ecosystem structure and services. Bacteria mediate numerous biogeochemical pathways within ecosystems. Therefore, identifying linkages between stressors associated with agricultural land use and responses of bacterial diversity is an important step in understanding and improving resource management. Here, we use the Mississippi Alluvial Plain (MAP) ecoregion, a highly modified agroecosystem, as a case study to better understand agriculturally associated drivers of stream bacterial diversity and assembly mechanisms. In the MAP, we found that planktonic bacterial communities were strongly influenced by salinity. Tolerant taxa increased with increasing ion concentrations, likely driving homogenous selection which accounted for ~90% of assembly processes. Sediment bacterial phylogenetic diversity increased with increasing agricultural land use and was influenced by sediment particle size, with assembly mechanisms shifting from homogenous to variable selection as differences in median particle size increased. Within individual streams, sediment heterogeneity was correlated with bacterial diversity and a subsidy-stress relationship along the particle size gradient was observed. Planktonic and sediment communities within the same stream also diverged as sediment particle size decreased. Nutrients including carbon, nitrogen, and phosphorus, which tend to be elevated in agroecosystems, were also associated with detectable shifts in bacterial community structure. Collectively, our results establish that two understudied variables, salinity and sediment texture, are the primary drivers of bacterial diversity within the studied agroecosystem, whereas nutrients are secondary drivers. Although numerous macrobiological communities respond negatively, we observed increasing bacterial diversity in response to agricultural stressors including salinization and sedimentation. Elevated taxonomic and phylogenetic bacterial diversity likely increases the probability of detecting community responses to stressors. Thus, bacteria community responses may be more reliable for establishing water quality goals within highly modified agroecosystems that have experienced shifting baselines.

Orange-red luminescence of samarium-doped bismuth-germanium-borate glass for light-emitting devices.

Samarium (Sm3+ )-doped glass has sparked a rising interest in demonstrating a noticeable emission in the range of 400-700, which is advantageous in solid-state lasers in the visible region, colour displays, undersea communication, and optical memory devices. This study reports the fabrication of Sm3+ -doped bismuth-germanium-borate glasses were established using a standard melt-quenching technique and inspection by absorption, steady-state luminescence, and transient studies. The typical peaks of Sm3+ ions were detected in the visible range under 403 nm excitation. A strong emission band was detected at 599 nm that resembles the 4 G5/2 →6 H7/2 transition of Sm3+ ions for BGBiNYSm0.5 glass. Furthermore, a reddish-orange (coral) luminescence at 646 nm that resembles the 4 G5/2 →6 H9/2 transition was also perceived. The stimulated emission cross-section of 4 G5/2 level for BGBiNYSm0.5 glass was 0.39 × 10-22 cm2 . Lifetime of the 4 G5/2 level was enhanced for the BGBiNYSm0.5 glass and decreased with an increase in active ion concentrations. The lifetime quenching of ions at the metastable state was because of energy transfer among Sm3+ ions by cross-relaxation channels. Commission Internationale de l'Éclairage (CIE) coordinates were evaluated from the emission spectra. Moreover, all the findings recommend these glass as light-emitting materials in the coral region at 599 nm for solid-state lighting applications.

The effect of addition of K2ZrF6 on the structures and properties of AZ31 magnesium alloy MAO coating

It is a challenge to improve the corrosion rate and blood compatibility of biomedical magnesium alloy implants in human body. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD) were used to study the Properties of K2ZrF6 modified AZ31 magnesium alloy composite coating. The corrosion behavior of the sample in simulated body fluid (SBF) was evaluated by hydrogen evolution corrosion, potentiodynamic polarization cur ve and electrochemical impedance spectroscopy. The results show that the corrosion resistance of magnesium alloy is significantly improved by composite coating. The wettability test shows that K2ZrF6 greatly improves the biocompatibility of MAO coating on magnesium alloy. The hemolysis test shows that the composite coating makes magnesium alloy have low hemolysis rate. The increase of PH value and magnesium ion concentration in solution caused by corrosion of magnesium alloy can be adjusted by adding K2ZrF6. The corrosion resistance mechanism of MAO coating on K2ZrF6 modified magnesium alloy was discussed. In this experiment, the optimum amount of K2ZrF6 is 4 g/L.

The Corrosion Properties of Bronze Alloys in NaCl Solutions.

Chloride ions play an important role in the corrosion of bronze through their active reactivity to copper alloys. The corrosion behavior of bronze alloys in NaCl solution was investigated by using X-ray diffraction (XRD), a scanning electron microscope (SEM), and electrochemical tests, with a special emphasis on the corrosion resistance of the α and δ phases in Cu-20 wt%Sn bronze alloys. The experimental results show that the corrosion current density of Cu-20 wt%Sn bronze alloys increases from 1.1 × 10-7 A/cm2 to 2.7 × 10-6 A/cm2 with the increase in the chloride ion concentration from 10-3 mol/L to 1 mol/L. After a soaking duration of 30 days, the matrix corrosion depth reaches 50 μm. The α phase of the alloys is easily corroded in NaCl solution, while the δ phase with high Sn content has strong corrosion resistance. This study provides relevant data for the analysis and protection of ancient bronze alloys.

The diagnostic power of salivary electrolytes for Sjögren's disease: a systematic literature review and meta-analysis.

To perform a systematic review and meta-analysis to determine the power of salivary electrolytes for the diagnosis of Sjögren's disease (SjD). A literature search was conducted (last search March 2023) using PubMed and Web of Science and completed with a manual search. Articles were screened for reports of human salivary ion concentrations, comparing SjD patients with healthy controls and/or sicca patients. Articles not using the SjD classification criteria or performing the classification as part of the experimental design were excluded. Forest plots were used to present the meta-analyses results for each ion, distinguishing between salivary type (unstimulated and stimulated whole saliva, submandibular/sublingual and parotid saliva). A total of 21 out of 722 articles were eligible for inclusion. For SjD patients a significant increase in salivary ion concentration was observed for sodium, chloride and calcium when comparing to healthy controls. Significant differences between SjD and sicca patients were noted for sodium, chloride, phosphate, calcium, phosphate, nitrite and nitrate. Stimulated whole saliva showed larger variability in results between studies in comparison to other types of saliva (unstimulated whole saliva, submandibular/sublingual saliva and parotid saliva). Despite differences in saliva type, salivary ion levels could be utilised for the screening for SjD. Making use of chloride in combination with sodium would be most promising for distinguishing SjD patients from healthy controls and adding phosphate to potentially make a distinguishment with sicca patients. Unstimulated whole saliva should be the first choice when testing salivary ion concentrations.

Nanopore based electrokinetic purification of oil-in-water emulsion with thermal and pH modulation

Abstract Efficient purification of oil-in-water emulsion is significant for protecting global water resource. Nevertheless, the traditional passive technologies for handling oil-in-water emulsion suffer from the drawback of low cost-effectiveness for using robust filtration membranes. In our previous research, an active electrokinetic based oil droplet filtration technique is firstly developed relying on a negative dielectrophoretic phenomenon induced by the huge difference between dielectric properties of oil and water. However, the effects of temperature and pH value of wastewater on the electrokinetic filtration efficiency of oil droplet have never been clarified. In the current work, a multi-physical theoretical model of electrokinetic purification of oil-in-water emulsion with thermal and pH modulation is constructed. The dimensionless ratio of dielectrophoretic force over hydrodynamic force on oil droplet is an essential criterion for its dynamic behavior, and it exhibits a positive correlation with purification effectiveness of oil-in-water emulsion. From numerical modelling, the magnitude of dielectrophoretic force to hydrodynamic force ratio on oil droplet is enhanced with a decreasing temperature, increasing ion concentration, and neutralized (pH=7.0) property of oily wastewater. Then, the critical direct current voltage for realizing successful oil droplet filtration through insulated nanopore under electrokinetics is analyzed under different parametric conditions, which indicates that the energy consumption of oil-in-water emulsion purification can be reduced by cooling down temperature and neutralizing pH value of aqueous solution. The current work offers a theoretical understanding of electrokinetic purification of oil-in-water emulsion, contributing to its development towards industrial applications.

Crystal structure, piezoelectric and magnetic properties of solid solutions BiMn1-xFexO3 (x ≤ 0.4)

Сrystal structure, piezoelectric and magnetic properties of solid solutions BiMn1-xFexO3 (x ≤ 0.4) prepared by solid-phase reactions from a stoichiometric mixture of simple oxides at high pressures and temperatures have been studied. The structure of the compounds is characterized by the concentration driven phase transition from the monoclinic structure to the orthorhombic structure at x ≈ 0.2; wherein the ordering dz2 of the orbitals of Mn3+ ions is destroyed, and the inhomogeneous magnetic state is stabilized. Solid solutions with 0.2 ≤ x ≤ 0.4 are characterized by a nonzero piezoelectric response, wherein both ferroelectric and magnetic domain structures exist, the ferroelectric switching voltage decreases with an increase of iron ions concentration, while the residual magnetization value decreases. The maximum value of the piezoresponse signal is observed in the compound BiMn0.7Fe0.3O3. The work clarifies the relationship between the chemical composition, the crystal structure, piezoelectric and magnetic properties of solid solutions BiMn1-xFexO3. The presence of both magnetic and electric dipole ordering indicates the perspectives for the practical usage of such materials.

Observation of structural, optical, electrical and magnetic properties of ternary copper-doped CeO2/GO/SrTiO3 nanocomposites

A ternary system involving copper-substituted ceria (Cu:CeO2)0.95−y(GO)y(SrTiO3)0.05 nanocomposite where the GO concentration (y) is varied between 0.15 and 0.30. The innovation of this work lies in the purposeful assembly of the nanocomposite using a grinding method, which was optimized through the individual fabrication of Cu-doped CeO2 with different CuO concentrations. In the first, Cu-doped CeO2 with various CuO concentrations (x = 0.0, 0.05, 0.1, 0.2, and 0.3) was first individually fabricated based on a sol–gel auto-combustion strategy to optimize the best ratio. The XRD profiles confirm the successful fabrication of cubic cerium (IV) oxide CeO2 using glycine as a fuel at an annealing temperature of 400 °C for 2 h. AC conductivity was investigated for both Cu-doped CeO2 and the ternary nanocomposite over a wide frequency range (10–1 to 107 Hz) at room temperature. The conductivity showed lower values for CeO2 doped with 0.05, 0.2, and 0.3 wt% CuO, whereas it showed its maximum values upon doping with 0.1 wt% CuO. Interestingly, the conductivity of graphene oxide–doped CeO2 was 103 times higher than that of pure CeO2, i.e., it increased from 1.7 × 10–6 to 2 × 10–3 S/cm. The magnetic-field dependence of MS of the ternary Cu-doped CeO2/GO/SrTiO3 nanocomposites showed a systematic increase in MS as the Cu2+ ion content increased. This strengthens the ferromagnetism in our samples as Cu2+ ion content increases.

Investigation of structural, elastic and magnetic properties of Cu2+ ions substituted cobalt nano ferrites

In the present work, we synthesized the Cu-doped CoFe2O4 (Co1-xCuxFe2O4) nanoparticles with × = 0.0, 0.2, 0.4 and 0.6, by employing the citrate precursor method. The X-ray Diffraction (XRD) pattern confirmed the pure cubic structure formation with the Fd-3m space group. To know the structural purity of each sample as well as the distribution of cations, Rietveld refinement was carried out. The crystallite size increases from 39.55 nm to 41.80 nm upto x = 0.2 and with further doping of Cu2+ ions it decreases to 36.27 nm. Similar variation is observed in the lattice parameter where the value of ‘a’ first increases from 8.378 Å to 8.381 Å and then decreases to 8.377 Å. The development of a non-uniform grain is seen using scanning electron microscope (SEM), which reveals the reduction in grain size. Fourier Transform Infrared Spectroscopy (FTIR) showed the two peaks v1 and v2 for all the samples around 541 cm−1 and 408 cm−1, respectively, which further decreases to 532.5 cm−1 and 402.5 cm−1 as the dopant ion concentration increases. The Stiffness constant, and Elastic modulus decrease with doping whereas, the Poisson’s ratio and Pugh’s ratio show a constant value of around 0.249 and 1.660, respectively. Vibrating Sample Magnetometer (VSM) analysis shows a decrease in saturation magnetization (σs) value from 76.85 emu/g to 43.62 emu/g. The net magnetic moment (nB) decreases from 3.29 μB to 1.85 μB and the effective anisotropy constant value decreases from 10.672erg/g to 4.461erg/g. Thus, the prepared nanoparticles provide a way forward for their industrial applications.

Hydrochemical Response of Karst Groundwater to Rapid Urbanization in Xingtai, North China

Karst groundwater is the main water source for domestic, industrial, and agricultural needs in Xingtai City, North China. The objective of this study was to comprehensively access changes in the hydrochemical characteristics and evolution of karst groundwater in response to rapid urbanization. Water samples from the late 2010s and the 1970s were compared utilizing statistical analysis, hydrochemical diagrams, and inverse simulation technology. The total dissolved solids (TDS), total hardness (TH), NO3−, and Fe contents were significantly higher in the more recently obtained karst groundwater samples. Further, the dominance of HCO3-Ca-type water decreased, with new types emerging, relative to 1970s karst groundwater. Abnormal TDS, TH, SO42−, NO3−, and Cl− concentrations can be attributed to sewage discharge and fertilizer. Two groundwater discharge areas around the center of Xingtai City and Yangfan Town in the south of the study area were the most significantly affected by human activities. However, inverse modeling indicated that the dissolution of gypsum and halite, as well as cation-exchange processes, occurred in the groundwater paths during both periods. Recent increases in ion concentrations of karst groundwater in the study area have caused carbonate minerals to dissolve, resulting in a further increase of ion concentrations. The hydrochemical response and evolution of karst groundwater requires further study.

Recyclable Multifunctional Magnetic Fe3O4@SiO2@Au Core/Shell Nanoparticles for SERS Detection of Hg (II)

Mercury ions can be enriched along the food chain and even low concentrations of mercury ions can seriously affect human health and the environment. Therefore, rapid, sensitive, and highly selective detection of mercury ions is of great significance. In this work, we synthesized Fe3O4@SiO2@Au three-layer core/shell nanoparticles, and then modified 4-MPy (4-mercaptopyridine) to form a SERS sensor. Mercury ions in water can be easily captured by 4-MPy which were used as the reporter molecules, and the concentration of mercury ions can be evaluated based on the spectral changes (intensification and reduction of peaks) from 4-MPy. After the mercury ion was combined with the pyridine ring, the peak intensity at 1093 cm−1 increased with the concentration of mercury ion in the range of 10 ppm–1 ppb, while the Raman intensity ratio I (416 cm−1)/I (436 cm−1) decreased with the increase of mercury ion concentration. This magnetically separatable and recyclable SERS sensor demonstrates good stability, accuracy, and anti-interference ability and shows the potential to detect actual samples. Furthermore, we demonstrate that the probe is applicable for Hg2+ imaging in macrophage cells.

Effect of Na+ and Ca2+ on the texture, structure and microstructure of composite protein gel of mung bean protein and wheat gluten

To investigate the change of ionic strength on the gel characteristics during the processing of mung bean protein-based foods, the effects of NaCl and CaCl2 at different concentrations (0–0.005 g/mL) on the properties of mung bean protein (MBP) and wheat gluten (WG) composite protein gel were studied. The results showed that low concentration (0.001–0.002 g/mL) could significantly improve the water holding capacity (WHC), storage modulus (G') and texture properties of composite protein gel (MBP/WG), while the surface hydrophobicity (H0) and solubility were significantly decreased (P < 0.05). With the increase of ion concentration, the secondary structures of MBP/WG shifted from α-helix to β-sheet, and the fluorescence spectra also showed fluorescence quenching phenomenon. By analyzing the intermolecular forces of MBP/WG, it was found that with the addition of salt ions, the hydrogen bonds was weakened and the electrostatic interactions, hydrophobic interactions and disulfide bonds were enhanced, which in turn the aggregation behavior of MBP/WG composite protein gel was affected and larger aggregates between the proteins were formed. It could be also demonstrated that the gel network was denser due to the addition of these large aggregates, thus the gel properties of MBP/WG was improved. However, too many salt ions could disrupt the stable network structure of protein gel. This study can provide theoretical support to expand the development of new mung bean protein products.

Investigation of phytoextraction and tolerance capacity of Calotropis procera for the detoxification of hexavalent chromium, nickel, and lead

The aim of the present study is to reveal the phytoremediation capability of Calotropis procera in the selected region of Bandhwari landfills. Results affirmed that the excessive deposition of municipal solid waste changes the physico-chemical parameters of the soil, which may cause soil pollution. The pot experiment was set up for heavy metals (Cr, Ni, and Pb) analysis with three different concentrations (50 ppm,100 ppm, and 150 ppm). Samples were analyzed to assess the plant’s capability for phytoremediation after 42 days. In the current investigation, ICP-MS results revealed that chromium, nickel, and lead concentration is higher than the permissible limit as per WHO. Results showed that the bioaccumulation factor follows the order of Cr > Ni > Pb. The bioconcentration factor and translocation factor are 15.63 mg/kg and 11.36 mg/kg respectively for Calotropis procera and the highest among all other metal concentrations. Peroxidase activity increases with an increase in chromium ion concentration whereas comparatively less increase of peroxidases in different concentrations of lead and nickel. Peroxidase enzyme assay and photosynthetic pigment test were carried out for tolerance estimation and uptake mechanism of Calotropis procera. FTIR data revealed significant levels of chromium complexation and binding to Calotropis procera tissue via hydroxyl and carboxyl groups. Therefore, it can be concluded that Calotropis procera has the efficiency to provide an effective way to handle heavy metal pollution problems and act as an important cost-effective tool for sustainability and conservation of the environment.

Thermotropic liquid crystal doped with silica, silica grafted with aniline (ANI@SiO2) and polyaniline (PANI@SiO2)

ABSTRACT Nanoparticles dispersed in liquid crystals exhibit novel and intriguing properties, which make them suitable materials for displays and photonic applications. This paper reports on the impact of non-modified silica (SiO2), silica grafted with aniline (ANI@SiO2) and silica grafted with polyaniline (PANI@SiO2) nanoparticles on the physical parameters of 7CB liquid crystal. A slight change in the nematic-isotropic phase transition temperature was observed. The results from dielectric experiments revealed an increase in free ion concentration in the doped samples. By fitting a suitable equivalent electric circuit model to the experimental data, we demonstrate changes in the electro-physical parameters of the liquid crystal in the bulk and at the liquid crystal-metal electrode interface. Therefore, we were able to calculate the ion mobility and the diffusion constant. It was also demonstrated that the doping of 7CB with the above-mentioned nanoparticles increases the response time, thresholds, and viscosity.

Damage Time-Dependent Characteristics and Failure Mechanism of Limestone with Different Mineral Compositions Under Acid Hydro-Chemical Solution Erosion

Taking two types of limestone with different mineral compositions as research objects, we conducted experiments on the mass, longitudinal wave velocity, ion concentration of solution, fracture morphology, and micromorphology of two types of limestone specimens eroded by acidic hydro-chemical solution. We investigated specimens’ damage time-dependent physical properties, dissolution, structure, discussing mineral composition effects and destruction. Results show that the mass loss rate of two types of limestone specimens eroded by acidic hydro-chemical solution increases with the increase of immersion time in a power function, and the longitudinal wave velocity decreases and then fluctuates in a small range. The specimen fracture degree increases with the increase of the immersion time, and the rock micro-structure changes from dense and uniform into loose and porous. The mass, the longitudinal wave velocity, the fracturing morphology, and damage to microscopic morphology of specimens increase with the increase of solution ion concentration. The acid rock reaction rate of limestone A is lower than that of limestone B, while the hydrolysis reaction rate is higher. The mass loss rate, the longitudinal wave velocity loss rate, the ion concentration, and the damage degree of the macro-and micro-structure of limestone A are higher than that of limestone B.

Influence of natural organic matters on fate of polystyrene nanoplastics in porous media

Natural organic matters (NOMs) are widely present in aqueous environments. The effect of NOMs on the fate of nanoplastics that are gradually receiving widespread attention in porous media needs to be noticed, but relevant research is lacking. To fill this gap, the present study focused on elucidating the influence of NOMs and metal cations with varying concentrations upon the transport, long-term release, and particle fracture of polystyrene nanoplastics (PS-NPs) in saturated porous media. The adsorption, transport, long-term release, and particle fracture tests were conducted. A mathematical model and the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory were used in this research. NOMs could adsorb onto PS-NPs leading to a reduction in the PS-NPs' zeta potential and an increase in the energy barrier and steric hindrance between PS-NPs and quartz sand, ultimately facilitating the transport of PS-NPs through porous media. On the other hand, an increase in concentration and valence of metal ions enhanced the PS-NPs' zeta potential, resulting in PS-NPs' aggregation and increased size when NOMs were present. This reduced the energy barrier between porous media and PS-NPs, resulting in increased blocking and straining, allowing decreased PS-NPs' transport. Long-term release tests demonstrated release ability and mobilities of PS-NPs decreased as the enhanced NOM concentration, addition of metal cations, and decreased valence of metal ions, in agreement with the transport test findings. In the research about particle fracture, NOMs were found to inhibit the fracture of PS-NPs by adsorbing on their surface to protect them from fracture. Metal cations and increased metal cation valence promoted the fracture of released PS-NPs when NOMs were present by promoting NOM aggregation and thus hindering the protection of NOMs for the nanoplastics.