Strength Of Solution Research Articles

Cotransport of titanium dioxide nanoparticles and formaldehyde in saturated and unsaturated columns packed with quartz sand

AbstractLaboratory‐scale experiments were conducted to investigate the simultaneous transport of titanium dioxide (TiO2) nanoparticles and formaldehyde (FA) in columns packed with quartz sand under water saturated and unsaturated flow conditions. The effects of interstitial velocity and solution ionic strength on the TiO2 and FA cotransport were examined. The experimental results indicated that substantial retention of TiO2 nanoparticles occurs in both saturated and unsaturated porous media. The solution ionic strength was found to have a noticeable effect on the retention of TiO2 nanoparticles in the packed columns. Moreover, the results from the TiO2 nanoparticle transport experiments in water‐saturated packed columns suggested that the TiO2 nanoparticle mass recoveries increased with increasing flow rate. The results from the TiO2 nanoparticles and FA cotransport experiments in both water saturated and unsaturated packed columns did not reveal a distinct relationship between mass recoveries and flow rate. The transport of FA in both saturated and unsaturated packed columns was hindered in the presence of TiO2 nanoparticles, especially at high ionic strength. This work provides useful insights into fate and transport of TiO2 nanoparticles and FA in saturated and unsaturated porous media.

Generic Rules for Distinguishing Autophoretic Colloidal Motors.

Distinguishing the operating mechanisms of nano- and micromotors powered by chemical gradients, i.e. "autophoresis", holds the key for fundamental and applied reasons. In this article, we propose and experimentally confirm that the speeds of a self-diffusiophoretic colloidal motor scale inversely to its population density but not for self-electrophoretic motors, because the former is an ion source and thus increases the solution ionic strength over time while the latter does not. They also form clusters in visually distinguishable and quantifiable ways. This pair of rules is simple, powerful, and insensitive to the specific material composition, shape or size of a colloidal motor, and does not require any measurement beyond typical microscopy. These rules are not only useful in clarifying the operating mechanisms of typical autophoretic micromotors, but also in predicting the dynamics of unconventional ones that are yet to be experimentally realized, even those involving enzymes.

Thermodynamic evaluation of the uranyl peroxide synthetic route on morphology

Understanding the mechanisms controlling the morphology of uranium ore concentrates (UOCs) is impactful for both the nuclear forensics and nuclear fuels communities. In forensics, this understanding enables predicting the morphology of materials to help determine provenance and processing history. In fuels, this understanding aids in optimizing the morphology for higher fuel efficiency. To elucidate the influence of thermodynamics on the morphology of UOCs, uranyl peroxide, specifically metastudtite (UO2O2·2H2O), was precipitated from solutions of varying complexing strength to the uranyl ion. Specifically, metastudtite was precipitated from solutions of equal ionic strength of uranyl nitrate and uranyl chloride, where the nitrate ion has greater complexing strength with the uranyl ion. Following precipitation, the metastudtite was calcined to U3O8, and the phase purity of each sample was confirmed by powder X-ray diffraction (p-XRD). The surface features were characterized using scanning electron microscopy (SEM), and the morphology was quantified using the Morphological Analysis for Materials (MAMA) software. Nanoparticles of metastudtite precipitated from uranyl nitrate, which has the higher complexing strength, were larger, more angular, and more elongated than nanoparticles produced by precipitation from uranyl chloride. Overall, a more rigid morphology was produced when replacing the nitrate with the peroxide while more rounded particles were produced when replacing a chloride with the peroxide. Even after sintering at high temperatures, differences in morphology between the two routes were still present in the U3O8.

Photodegradation actuated shape‐changing hydrogels

AbstractHydrogels are attractive materials for generating 4D shapes due to their ability to undergo pronounced volume changes in response to several stimuli, including light. We previously reported shape‐changing hydrogels actuated by long‐wave UV and visible light in the presence of live cells using poly(ethylene glycol) macromers incorporating different photodegradable ortho‐nitrobenzyl (o‐NB) groups. In this comprehensive study, we determine the effect of chemical structure of different o‐NB macromers (which influences molar absorptivity and rate constant of degradation), composition (macromer weight percent), fabrication design (initial gel thickness) and environment (ionic strength of solution) on light‐induced hydrogel folding. We demonstrate successful photopolymerization and subsequent photodegradation of hydrogels, multistep folding, and live‐cell encapsulation. This hydrogel system may be useful as new tool in stem cell differentiation and developmental biology research, facilitating the in vitro investigation of processes that are sensitive to both physical and temporal stimuli.

Nonlinear charge regulation for the deposition of silica nanoparticles on polystyrene spherical surfaces

HypothesisWe describe the deposition behavior of monodispersed silica nanoparticles on polystyrene spherical particles by using modified pairwise DLVO (Derjaguin-Landau-Verwey-Overbeek) interaction force profiles at pH values between two and twelve. Our modified model contains a new nonlinear charge regulation parameter that considers redistribution of ions, which allows us to realistically express the electrical double layer (EDL) interaction forces. ExperimentsSilanol-terminated silica nanoparticles (7.6 ± 0.4 nm), l-lysine-covered silica nanoparticles (7.8 ± 0.4 nm), and polyallylamine hydrochloride-covered polystyrene (PAH/PS) particles (348 ± 1 nm) were synthesized. Then, each type of silica nanoparticle was deposited on the PAH/PS particles at a range of pH values. FindingsOur new regulation parameter describes the realistic redistribution of charges governed by pH, total salt concentration, ionic strength of solution, and separation distance of particles. We find that this regulation parameter can be roughly approximated from the absolute values of theoretically calculated surface charge density and potential distributions, as well as experimentally measured ζ-potentials. Morphological analysis using electron microscopy of the experimental systems shows that the modified pairwise DLVO interaction forces exceptionally describe the deposition behavior of the silica nanoparticles physically adsorbed on the PAH/PS particle substrates.

Frother Characterization Using a Novel Bubble Size Measurement Technique

Bubble size measurement is a vital part of flotation system analysis and diagnostics. This work evaluates a commercial camera probe as a novel method for in situ bubble size measurement. This device is compared to the conventional Anglo Platinum Bubble Sizer (Stone ThreeTM). It was found that, in laboratory applications, the in situ bubble size analysis technology appears to be a more user-friendly and reliable option for determining bubble size in flotation, whereas the Anglo Platinum Bubble Sizer is more applicable for full scale industrial work. This probe was then used to conduct a rigorous comparison of the behavior of different frother chemistries at a variety of background solution ionic strength conditions. The critical coalescence concentrations and the minimum Sauter mean bubble diameters were determined. Five frothers were compared in terms of their ability to reduce bubble size and sensitivity to salinity. In order to adjust plant recipe and control strategy accordingly, it is recommended that the plant would need to use less frother during periods of the high salinity of process water to achieve the minimum Sauter mean bubble size.

Quantitative effects of surface oxidation on biochar derived from long-root Eichhornia Crassipes plants as Cd2+ adsorbent

Quantitative effects of surface oxidation on Cd2+ adsorption performance of biochar derived from long-root Eichhornia Crassipes plants were systematically investigated. It was revealed that oxidation degree was positively related with the intensity of surface functional groups and harmless for the structural stability, while biochar yield would decline sharply resulting from for over-oxidization. Correspondingly, the Cd2+ adsorption capacity exhibited an uptrend with the increasing oxidation on account of the abundant adsorption sites. Moreover, Cd2+ adsorption on the biochar with different oxidation degrees were also investigated comprehensively, indicating adsorption performances in a similar trend highly sensitive to solution pH and ionic strength. In addition, the adsorption isotherms were found to manifest the saturated adsorption capacity for Cd2+ increased from 0.333 mol/g to 0.487 mmol/g at 30 °C by strengthening oxidation. All synthesized biochar could keep consistent adsorption performance in multiple adsorption-desorption cycles.

Impact of heavy metal cations on deposition and release of clay colloids in saturated porous media

AbstractWhile the facilitated transport of heavy metals by colloids such as clay particles has been widely recognized, the influence of heavy metals on transport of the colloids has received much less attention. This study conducted saturated column experiments to systematically examine influence of multivalent heavy metal cations on transport of natural clay colloids and fullerene nC60 nanoparticles in glass bead porous media. Results showed that the presence of Cd2+ in the solution can cause more deposition of clay colloids in glass beads compared to Ca2+ at a given ionic strength (IS), and the subsequent release by IS reduction was less, demonstrating that the presence of Cd2+ increased the irreversibility of attachment. When the glass beads were initially adsorbed with Ca2+ and Cd2+, the release of clay colloids was significantly reduced due to strong cation bridge between the clay colloids and collector surfaces via the heavy metal cations. The release of clay colloids was significantly increased upon reduction of solution IS if the Na+ was used to exchange for the Ca2+ or Cd2+ before the IS reduction. Additional experiments showed that the nC60 nanoparticles that were deposited in the presence of Fe3+ and Cu2+ cannot be released by reduction of solution IS. However, the nanoparticle release occurred when the Ca2+ was used to exchange for the Fe3+ and Cu2+. Our work was the first to reveal the influence of heavy metal cations on the irreversibility of colloid attachment, and the findings have important implication to fabrication of functional nanomaterials for stabilization of heavy metals in soil and development of mathematic models for accurate prediction of cotransport of heavy metals and colloids in subsurface environments.

Quantifying the effect of polynuclear hydroxocomplex adsorption on the charge reversals at solid surfaces

The adsorption of heavy metal ions onto negatively charged oxide (quartz) surface in environmental settings produces three surface charge reversals (CRs) described as CR1 at low pH, CR2 at middle pH, and CR3 at high pH. The available physical quantitative approaches cannot predict all these CRs and are not applicable for low salt concentrations (< 1 mM). In this study, a new model was presented to describe the CRs of the Pb(II)-quartz system by combining the ion distribution as the inner- and outer-sphere complexes within the compact (Stern) layer of the electrical double layer theory and the adsorption of Pb(II) hydroxocomplexes by the surface complexation and precipitation. The results indicated that the model agreed with the measured surface (zeta) potential values and the observed CRs for quartz particles in Pb(II) solutions over a wide range of Pb(II) concentrations, pH, and solution ionic strength. The model showed the pivotal role of Pb(II) polynuclear hydroxocomplexes (PNHCs) such as Pb3OH42+ in the appearance of the CR2. The predicted surface binding constants for PNHCs were lower than their corresponding hydrolysis constants which implied an earlier formation of those species at the interface than in the bulk solution. Increasing the solution ionic strength reduced the magnitude of surface potential and shifted the CR2 to higher pH values. The model was also validated with the literature data. With better understanding the role of PNHCs sorption and CR mechanisms, this model may also be adapted to other systems containing multivalent ions that are relevant to environmental applications.

Determination of specific and non-specific protein-protein interactions for beta-lactoglobulin by analytical ultracentrifugation and membrane osmometry experiments.

Protein-protein interactions are essential for the understanding of biological processes. Specific protein aggregation is an important aspect for many biological systems. In particular, electrostatic interactions play the key role for protein-protein interactions, as many amino acids have pH-dependent charge states. Moreover, protein dissociation is directly related to the solution pH, ionic strength, temperature and protein concentration. The subtle interplay between different specific and non-specific interactions is demonstrated for beta-lactoglobulin (BLG) with a focus on low salt concentrations, thus mimicking technically relevant processing conditions. BLG is a well-characterized model system, proven to attain its monomer-dimer equilibrium strongly dependent upon the pH of the solution. In this manuscript, we present a unique combination of analytical ultracentrifugation and membrane osmometry experiments, which quantifies specific and non-specific interactions, i.e. in terms of the dimer dissociation constants and the second osmotic virial coefficient, at pH 3 and 7 and sodium chloride concentrations of 10 mM and 100 mM. This provides direct insight to protein-protein interactions for a system with a concentration-dependent monomer-dimer equilibrium. Moreover, using a coarse-grained extended DLVO model in combination with molecular dynamics simulations, we quantify non-specific monomer-monomer, monomer-dimer and dimer-dimer interactions as well as the binding free energy of BLG dimerization from theoretical calculations. The experimentally determined interactions are shown to be mainly governed by electrostatic interactions and further agree with free energy calculations. Our experimental protocol aims to determine non-specific and specific interactions for a dynamically interacting system and provides an understanding of protein-protein interactions for BLG at low salt concentrations.

Type and screen method and Coombs crossmatch method for pretransfusion testing: A prospective comparative study in a tertiary care hospital in Delhi.

BACKGROUND:The aim of pretransfusion testing (PTT) is to prevent the immune-mediated hemolytic reaction by the transfusion of incompatible donor red cells. The methods of PTT have evolved over the years and a new method of type and screen (T and S) was introduced, in which only ABO grouping, Rh typing, and antibody screening would be carried out with omission of routine Coombs crossmatch. Although T and S is an accepted method for PTT in developed countries, only a few studies in literature have evaluated its efficacy in India.AIM AND OBJECTIVE:The aim of the study was to compare T and S method with conventional Coombs crossmatch method for PTT.MATERIALS AND METHODS:Two thousand and fifty samples were randomly selected from the samples received in blood bank for requisition of blood transfusion after taking informed consent. ABO blood grouping and Rh typing were performed for each recipient's sample. “T and S” and “Coombs crossmatch” were done simultaneously by two different persons without knowing the result of each test. A commercially available three cell panel was used for antibody screening, in which the recipient's plasma was reacted with red cells in the low ionic strength solution Coombs Gel card at 37°C by column agglutination technology.RESULTS:Antibody screening was positive in 29 (1.41%) patients and negative in 2021 (98.59%) patients. Out of 29 patients, 27 had alloantibodies and 2 had autoantibody. Most common alloantibody found in our study was anti-D. Other antibodies found were anti-K, anti-C + D, anti-E, anti-C, anti-c, anti-Jka, and anti-Mi (a). Crossmatch on first attempt was compatible in 2028 (98.93%) patients and incompatible in 22 (1.07%) patients. Out of 29 patients who were positive for antibody screening, crossmatch was incompatible in nine patients. Crossmatch was compatible in twenty patients, who had positive antibody screen. However, crossmatch compatibility in these patients, reflect either absence of corresponding antigen or antigen present in low dose (heterozygous) in donor blood. On the other hand, out of 22 patients incompatible on first crossmatch, antibody screening was negative in 13 patients and was positive in only nine patients. Hence, 13 patients with antibody would have been missed by antibody screen alone. Kappa statistics was used to compare the efficacy of “type and screening” and “Coombs crossmatch.” It showed κ =0.445 (P < 0.001) implying moderate agreement between the two variables of “T and S” and “Coombs crossmatch.”CONCLUSION:T and S is a scientifically better method but needs to be implemented with caution. We need to develop our own cell panels having adequate representation of indigenous antigen (including In, Mi (a), etc.,). Large-scale studies need to be done in India with indigenous screening cells to evaluate efficacy and safety of T and S method.

Removal of methylene blue using balanites aegyptiaca bark powder as low-cost and eco-friendly biosorbent

PurposeThis paper aims to investigate the potential application of Balanites aegyptiaca bark powder (BABP) for removing a basic textile dye, methylene blue (MB), from aqueous solutions.Design/methodology/approachThe biosorbent (BABP) was characterized using Fourier transform infrared spectroscopy (FTIR) and point of zero charge (pHPZC). Batch mode was selected to study the biosorption of MB onto BABP surface at different experimental conditions (shaking speed, contact time, initial solution pH, ionic strength, solution temperature, biosorbent dosage and initial dye concentration). Besides, the reusability of BABP for MB biosorption was also examined.FindingsThe biosorption results revealed that approximately 96% of MB was removed successfully at the optimized operational conditions. Pseudo-second-order and Langmuir models, respectively, better described the adsorption kinetics and isotherms. The monolayer biosorption capacity (qmax) for MB was about 97.09 mg/g. According to thermodynamics findings, the MB biosorption onto BABP is an exothermic and spontaneous process. The results demonstrate that BABP can be considered as potential eco-friendly, readily available and low-cost biosorbent for hazardous textile dyes removal from water bodies and also provides a promising method for minimization of agricultural solid wastes (e.g. plant barks).Originality/valueThe utilization of Balanites aegyptiaca bark powder (BABP), solid waste material, as low-cost and eco-friendly biosorbent for the removal of hazardous basic textile dye (methylene blue) from the aquatic environment.

Selective Adsorption of Metal-Organic Framework toward Methylene Blue: Behavior and Mechanism.

In this study, Cu-BTC, a kind of metal–organic framework, was used as an adsorbent to selectively adsorb methylene blue (abbreviated as MB) from dye mixed wastewater. The synthesized Cu-BTC was characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results indicated that the synthesized Cu-BTC have an octahedral structure, with its specific surface area at 45.16 m2/g and the pore sizes at 35–40 nm. The influence of various parameters including the initial solution pH, temperature, ionic strength, initial concentration, and contact time on MB adsorption by Cu-BTC was investigated in detail. The adsorption capacity of Cu-BTC toward MB was optimized at the pH value of 8, with a lower temperature and a higher ionic strength. The adsorption isotherm was found to fit well with the Langmuir model, and the kinetic curve was found to be in good agreement with the pseudo-second-order kinetic model. The adsorption mechanism was revealed to be the combined effects of hydrophobicity and electrostatic adsorption. The synthesized Cu-BTC adsorption material showed great potential for recovering MB from dye-mixed wastewater.

Ammonium molybdophosphate/metal-organic framework composite as an effective adsorbent for capture of Rb+ and Cs+ from aqueous solution

A new composite adsorbent (AMP@MOF-76(Sm)) grafted ammonium molybdophosphate onto MOF-76(Sm) was synthesized via a solvothermal method and well-characterized by SEM-EDS, particle size analysis, N2 adsorption-desorption isotherms, TG, FT-IR, XRD and XPS analysis. The adsorption behaviors of Rb+ and Cs+ on synthesized AMP@MOF-76(Sm) were investigated depending on the parameters of solution pH, ionic strength, contact time, ion concentration and temperature. The adsorbent can adsorb Rb+ and Cs+ from the solution when the solution pH ranged from 4.0 to 10.0 and the coexisted ion (Na+) has little effect on the adsorption amounts of both Rb+ and Cs+. The adsorption kinetic data fitted well with pseudo-second order kinetic models. The adsorption equilibrium of Rb+ and Cs+ on AMP@MOF-76(Sm) is better explained by the Langmuir isotherm model and the maximum adsorption amounts for Rb+ and Cs+ are 0.490 ​mmol ​g−1 and 0.434 ​mmol ​g−1, respectively. Furthermore, the AMP@MOF-76(Sm) could be easily reused at least four times using 3.0 ​mmol ​L−1 ammonia nitrate as the eluent. The mechanism of the adsorption of Rb+ and Cs+ is proposed to be a combination of electrostatic attraction and ion exchange mechanism.

Removal of Nickel Ions from Aqueous Solutions by 2-Hydroxyethyl Acrylate/Itaconic Acid Hydrogels Optimized with Response Surface Methodology.

The adsorption of Ni2+ ions from water solutions by using hydrogels based on 2-hydroxyethyl acrylate (HEA) and itaconic acid (IA) was studied. Hydrogel synthesis was optimized with response surface methodology (RSM). The hydrogel with the best adsorption capacity towards Ni2+ ions was chosen for further experiments. The hydrogel was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis before and after the adsorption of Ni2+ ions. Batch equilibrium experiments were conducted to investigate the influence of solution pH, hydrogel weight, ionic strength, adsorption time, temperature and initial concentration of nickel ions on the adsorption. Time-dependent adsorption fitted the best to the pseudo-second-order kinetic model. A thermodynamic study revealed that the adsorption was an exothermic and non-spontaneous process. Five isotherm models were studied, and the best fit was obtained with the Redlich–Peterson model. Consecutive adsorption/desorption studies indicated that the HEA/IA hydrogel can be efficiently used as a sorbent for the removal of Ni2+ ions from the water solution. This study develops a potential adsorbent for the effective removal of trace nickel ions.

Transport and deposition behaviors of microplastics in porous media: Co-impacts of N fertilizers and humic acid

Due to the interaction of fertilizers with microplastics (MPs) and porous media, fertilization process would influence MPs transport and distributions in soil. The co-impacts of N fertilizers (both inorganic and organic N fertilizers) and humic substance on MPs transport/retention behaviors in porous media were examined in 10 mM KCl solutions at pH 6. NH4Cl and CO(NH2)2 were employed as inorganic and organic N fertilizers, respectively, while humic acid (HA) was used as model humic substance. We found that for all three sized MPs (0.2, 1 and 2 µm) without HA, both types of N fertilizers decreased their transport/increased their retention in porous media (both quartz sand and soil). N fertilizers adsorbed onto surfaces of MPs and sand/soil, lowering the electrostatic repulsion between MPs and porous media, thus contributed to the enhanced MPs deposition. MPs with N fertilizers in solutions more tightly attached onto porous media and thus were more difficult to be re-mobilized by low ionic strength solution elution. Via steric repulsion and increasing electrostatic repulsion between MPs and porous media due to adsorption onto their surfaces, HA could increase MPs transport with N fertilizers in solutions.

Tunable Assembly of Protein Enables Fabrication of Platinum Nanostructures with Different Catalytic Activity.

Proteins are promising biofunctional units for the construction of nanomaterials (NMs) due to their abundant binding sites, intriguing self-assembly properties, and mild NM synthetic conditions. Tobacco mosaic virus coat protein (TMVCP) is a protein capable of self-assembly into distinct morphologies depending on the solution pH and ionic strength. Herein, we report the use of TMVCP as a building block to organize nanosized platinum into discrete nanorings and isolated nanoparticles by varying the solution pH to modulate the protein assembly state. Compared with a commercial Pt/C catalyst, the TMVCP-templated platinum materials exhibited significant promotion of the catalytic activity and stability toward methanol electrooxidation in both neutral and alkaline conditions. The enhanced catalytic performance is likely facilitated by the protein support. Additionally, Pt nanorings outperformed isolated nanoparticles, although they are both synthesized on TMVCP templates. This could be due to the higher mechanical stability of the protein disk structure and possible cooperative effects between adjacent nanoparticles in the ring with narrow interparticle spacing.

Interplay between epigallocatechin-3-gallate and ionic strength during amyloid aggregation.

The formation and accumulation of protein amyloid aggregates is linked with multiple amyloidoses, including neurodegenerative Alzheimer’s or Parkinson’s disease. The mechanism of such fibril formation is impacted by various environmental conditions, which greatly complicates the search for potential anti-amyloid compounds. One of these factors is solution ionic strength, which varies between different aggregation protocols during in vitro drug screenings. In this work, we examine the interplay between ionic strength and a well-known protein aggregation inhibitor—epigallocatechin-3-gallate. We show that changes in solution ionic strength have a major impact on the compound’s inhibitory effect, reflected in both aggregation times and final fibril structure. We also observe that this effect is unique to different amyloid-forming proteins, such as insulin, alpha-synuclein and amyloid-beta.

On the Determination of Halogen Atom Reduction Potentials with Photoredox Catalysts.

The standard one-electron reduction potentials of halogen atoms, E°'(X•/-), and many other radical or unstable species, are not accessible through standard electrochemical methods. Here, we report the use of two Ir(III) photoredox catalysts to initiate chloride, bromide, and iodide oxidation in organic solvents. The kinetic rate constants were critically analyzed through a derived diffusional model with Marcus theory to estimate E°'(X•/-) in propylene carbonate, acetonitrile, butyronitrile, and dichloromethane. The approximations commonly used to determine diffusional rate constants in water gave rise to serious disagreements with the experiment, particularly in high-ionic-strength dichloromethane solutions, indicating the need to utilize the exact Debye expression. The Fuoss equation was adequate for determining photocatalyst-halide association constants with photocatalysts that possessed +2, +1, and 0 ionic charges. Similarly, the work term contribution in the classical Rehm-Weller expression, necessary for E°'(X•/-) determination, accounted remarkably well for the stabilization of the charged reactants as the solution ionic strength was increased. While a sensitivity analysis indicated that the extracted reduction potentials were all within experimental error the same, use of fixed parameters established for aqueous solution provided the periodic trend expected, E°'(I•/-) <E°'(Br•/-) <E°'(Cl•/-), in all of the organic solvents investigated; however, the potentials were more closely spaced than what would have been predicted based on gas-phase electron affinities or aqueous reduction potentials. The origin(s) of such behavior are discussed that provide new directions for future research.

Hydration Shells of DNA from the Point of View of Terahertz Time-Domain Spectroscopy.

Hydration plays a fundamental role in DNA structure and functioning. However, the hydration shell has been studied only up to the scale of 10–20 water molecules per nucleotide. In the current work, hydration shells of DNA were studied in a solution by terahertz time-domain spectroscopy. The THz spectra of three DNA solutions (in water, 40 mm MgCl2 and 150 mM KCl) were transformed using an effective medium model to obtain dielectric permittivities of the water phase of solutions. Then, the parameters of two relaxation bands related to bound and free water molecules, as well as to intermolecular oscillations, were calculated. The hydration shells of DNA differ from undisturbed water by the presence of strongly bound water molecules, a higher number of free molecules and an increased number of hydrogen bonds. The presence of 40 mM MgCl2 in the solution almost does not alter the hydration shell parameters. At the same time, 150 mM KCl significantly attenuates all the found effects of hydration. Different effects of salts on hydration cannot be explained by the difference in ionic strength of solutions, they should be attributed to the specific action of Mg2+ and K+ ions. The obtained results significantly expand the existing knowledge about DNA hydration and demonstrate a high potential for using the THz time-domain spectroscopy method.