Borate Ions Research Articles

Electrolyte sensitivity of TEMPO mediated methanol and glycine electrooxidation

In order to emphasize the importance of electrolyte-tuning in the nitroxyl radicals mediated electrocatalytic reactions, methanol and glycine electrooxidation reactions catalyzed by TEMPO under different properties (pH, identity, concentration) of buffer solutions were investigated by cyclic voltammetry. It was discovered that in both carbonate buffer solutions and borate buffer solutions, catalytic abilities increase with the rising of pH for both glycine electrooxidation and methanol electrooxidation. The electrocatalytic performance is also affected by the identity of buffer, for both cases of glycine and methanol, the electrooxidation activities in borate buffer solutions are apparently higher than those in carbonate buffer solutions. For both glycine and methanol electrooxidation, relationships between concentrations of carbonate ions and relative catalytic current densities were observed to be volcano-shaped, while electrocatalytic abilities increase with the increasing of concentrations of borate ions within the studied concentration range. These findings suggest that the electrolyte should be treated as important as the catalyst in the designing of nitroxyl radicals mediated electrocatalytic systems.

Researching the complexing conditions of residual boron in produced water from oil & gas fields

Abstract Large volumes of fracturing flowback fluids are generated as produced water (PW) during oil & gas extraction. There is a method that uses such produced water as a suitable source of fracturing water, recycling it into subsequent fracturing gels. Not only does it reduce processing costs and environmental pollution, but it also effectively alleviates the problem of oilfield water shortage. However, the existence of residual boron in PW is a crucial obstacle to reutilization because it prematurely crosslinks hydroxypropyl guar (HPG) that affects pumping and fracking. So it is necessary to eliminate the adverse effect of residual boron in terms of recycling PW. Fortunately, boric acid easily reacts with polyols by bonding with other active cis-hydroxyl groups to form complexes, preventing residual boron from prematurely crosslinking with HPG. This study demonstrated the feasibility of shielding residual boron crosslinker in PW by a series of simulated crosslink systems. Results indicate that mannitol has a high complexation capacity for boron since it forms stable 5-member ring complexes by bonding with borate ion. When the mole ratio of ligand to boric acid exceeds 2.5 and the pH value is around 10.5, the shielding efficiency of mannitol to boron reaches 95%. The excessive amounts of ligands completely shield the boron and prevent its continuous crosslinking with HPG. The fracturing gels prepared by PW no longer show the premature crosslinking phenomenon after the shielding agent is added, and its rheological properties loading the new crosslinker are similar to the system which is prepared with deionized water. These results indicate that mannitol can effectively shield the residual boron crosslinker, removing the adverse effects of premature crosslinking with HPG base fluid. This has formed stable complexes, which still exist in the HPG base fluid system and do not affect the rheological properties of the subsequent fracturing gels. Compared with conventional boron treatment technologies, this treatment system also directly prepares the subsequent fracturing gels without the additional steps of filtering boron-complexes. Therefore, there are many significant advantages in these operational steps over traditional boron removal methods from the perspective of efficiency and cost-effectiveness.

Layered double hydroxides: matrices for storage and source of boron for plant growth

ABSTRACTThe increase of the absorption efficiency of boron (B) by plants is essential for increasing crop productivity. The intercalation of B in MgAl layered double hydroxides (LDHs) is an alternative to evaluating how these materials can provide B to plants. In this work, a MgAl LDH intercalated with borate ions (Mg2Al-B-LDH) was synthesized by the constant pH coprecipitation method, and the material produced was evaluated as a matrix for storage and as a source of B for plants. The Mg2Al-B-LDH was characterized by XRD, ATR-FTIR, TGA-DTA, specific surface area, pore size and volume, and SEM. A bioassay was performed to verify the supply of B to plants from the two sources in the forms of H3BO3 and of Mg2Al-B-LDH to sunflower plants grown in pots. The LDH basal spacing value of 12.0 Å is characteristic of intercalation of tetraborate octahydrate ions [B4O5(OH)42−]·8H2O between the layers. There was an increase in the dry matter (DM) and B content of the plants relative to those treatments where no B was added. The lack of statistical difference for plant yield between the two sources of B suggests a lack of stability of the Mg2Al-B-LDH structure under the acidic condition of the soil.

Carboxymethylagarose-based multifunctional hydrogel with super stretchable, self-healable having film and fiber forming properties

In this work, we repot a super stretchable and quick self-healable composite hydrogels with film and fiber forming properties through introducing hydrogen and covalent bonding. Herein, carboxymethylagarose (CMA) and polyvinyl alcohol (PVA) acts as physical crosslinkers. Boric acid (BA) prompt the formation of crosslinking through hydrogen bonding with blend polymers followed by strong ionic bonding between hydroxyl (OH) groups of PVA and borate ions of BA. Hydrogel obtained under optimum conditions shows excellent stretching (>100 times), quick self-healing (<1 s), notches insensitive stretching, fiber and film forming ability. Such integrated properties for a hydrogel system have been achieved using seaweed derived polymer for the first time. In summary, this study opens up a new possibility to design and assemble multifunctional hydrogels using abundant seaweed derived polysaccharides with outstanding stretching, healing plus other properties by simple crosslinking chemistry.

Application of guar gum in brine clarification and oily water treatment

The increasing amount of oil wastewater is causing serious damage to the environment. Oily water is a worrisome by-product of the oil industry due to its growing volume in mature basins and complex chemical composition. Low-cost polymers are being used as alternative materials to treat oily waters after treatment by conventional methods, oil and grease (O&G) concentration being the primary parameter for final disposal. In this respect, guar gum can be used to treat petroleum-contaminated waters, with the advantage of being a low-cost, highly-hydrophilic natural polymer. In this study, guar gum, under specific conditions, shapes itself into three-dimensional structures with interesting physicochemical properties. The salting out effect occurs with reticulation of the polymeric chains by borate ions and in the presence of electrolytes, reducing the solubility of the polymeric network in the solution and leading to an electrolyte- and polymer-rich phase. When the guar gum gel was prepared in situ in the produced water, after the salting out effect, the oil was imprisoned in the interstices of the collapsed gel. The gelling guar gum was highly efficient in synthetic oily waters. In the case of initial O&G above 100ppm, the oil removal percentage was above 90%.

Rheological properties of tough hydrogels based on an associating polymer with permanent and transient crosslinks: Effects of crosslinking density

We studied the rheological and mechanical properties of a series of poly(vinyl alcohol) dual crosslink hydrogels, permanently crosslinked by glutaraldehyde and transiently crosslinked by borate ions, at various crosslinking densities. The contribution of the chemical and physical crosslinks to the dynamic moduli was first determined with linear oscillatory tests, and the additivity of the two contributions was validated. The single relaxation time of the system was interpreted as the physical bond breaking time which can be slowed down by reassociation of the open physical bonds before full relaxation. By comparing the Rouse relaxation time of the strand between two adjacent crosslinks with the healing time of the physical bonds, an increase in the relaxation time with decreasing density of physical crosslinks was explained. In all cases, the extensibility and stress at break of the gels were found to increase with the addition of physical crosslinks, but the extensibility increased the most for the smallest amount of chemical and physical crosslink densities while the stress at break increased the most for the most physically crosslinked system with a low chemical crosslink density. This strongly suggests that the toughening mechanism due to the presence of transient bonds can only be active on a network with a low density of chemical crosslinks. In large strain experiments, the tensile stress could be separated into a strain-dependent and a time-dependent term for all the crosslinking densities studied, and master curves of the reduced stress as a function of time were obtained. This showed that the chemical and physical crosslinks independently and additively contribute to the viscoelasticity of the dual crosslink gel.

Theoretical isotopic fractionation between structural boron in carbonates and aqueous boric acid and borate ion

The 11B/10B ratio in calcite and aragonite is an important proxy of oceanic water pH. However, the physico-chemical mechanisms underpinning this approach are still poorly known. In the present study, we theoretically determine the equilibrium isotopic fractionation properties of structural boron species in calcium carbonates, BO33−, BO2(OH)2− and B(OH)4− anions substituted for carbonate groups, as well as those of B(OH)4− and B(OH)3 species in vacuum. Significant variability of equilibrium isotopic fractionation properties is observed among these structural species which is related to their contrasted coordination state, BO bond lengths and atomic-scale environment. The isotopic composition of structural boron does not only depend on its coordination number but also on its medium range environment, i.e. farther than its first coordination shell. The isotopic fractionation between aqueous species and their counterparts in vacuum are assessed using previous investigations based on similar quantum-mechanical modeling approaches. At 300 K, the equilibrium isotope composition of structural trigonal species is 7–15‰ lighter than that of aqueous boric acid molecules, whereas substituted tetrahedral borate ions are heavier than their aqueous counterparts by 10–13‰. Although significant uncertainties are known to affect the theoretical prediction of fractionation factors between solids and solutions, the usually assumed lack of isotopic fractionation during borate incorporation in carbonates is challenged by these theoretical results. The present theoretical equilibrium fractionation factors between structural boron and aqueous species differ from those inferred from experiments which may indicate that isotopic equilibrium, unlike chemical equilibrium, was not reached in most experiments. Further research into the isotopic fractionation processes at the interface between calcium carbonates and aqueous solution as well as long duration experiments aimed at investigating the kinetics of equilibration of boron environment and isotopic composition are therefore required to refine our understanding of boron coprecipitation in carbonates and thus the theory behind the use of boron isotopes as an ocean pH proxy.

Removal of high level boron in aqueous solutions using continuous electrodeionization (CEDI)

Abstract The high levels of boron in nuclear power plant wastewater require removal before discharge, particularly for inland plants. Continuous electrodeionization (CEDI) is very effective at treating wastewater with low conductivity and was investigated for use in removing high levels of boric acid. Solutions containing high levels (60–400 mg/L) of boric acid were treated with a small-scale CEDI stack in a constant current mode. The removal efficiency of boron using CEDI increased from 15% to 23% as current increased from 0.5 A to 2.0 A. Boron removal ratios decreased from 45% to 16% when boron concentration in the feed solutions increased from 60 to 400 mg/L. Decreasing the feed flow rate into the diluting compartment promoted boron removal. Optimal pH was found to be at 10, at which 26% of boron was removed. The three main factors influencing boron removal of boron were as follows: borate ion speed upon entering the resin, borate ion transport rate, and ion exchange inhibition by OH − . Our results indicate that CEDI can be used to remove high levels of boron, but future modifications will be needed to enhance removal efficiency.

Polymer-Enhanced Capillary Transient Isotachophoresis with Boronic Acid-Functionalized Squarylium Dyes for the Fluorescent Determination of Digoxin and Digoxigenin

ABSTRACTHere is reported a new application of polymer-enhanced capillary transient isotachophoresis for the separation and quantification of the drug digoxin and its primary metabolite digoxigenin coupled with laser-induced fluorescence (LIF) detection facilitated by labeling with two boronic acid-functionalized squarylium dyes of different alkyl side chain lengths, SQ-BA1 and SQ-BA2. The conditions for drug–dye complex formation were optimized, as determined by absorbance and fluorescence spectra, according to solution pH and buffer composition. As digoxin has a digitoxose sugar moiety in its structure, it was shown to exhibit better enhancement in the fluorescence intensity of both dyes than digoxigenin, which lacks this moiety, presumably through the formation of a cyclic boronate ester complex. A comparison of analyte labeling in pre-column and on-column modes was conducted in subsequent capillary electrophoresis-LIF studies, with the latter labeling mode yielding superior sensitivity. However, to achieve the complete resolution of labeled digoxin and digoxigenin analytes, it was necessary to use the modified isotachophoresis method, with added borate ions that may differentially interact with the drug and its metabolite, hence affecting their mobilities. Limits of quantification of the method for the determination of digoxin with SQ-BA1 and SQ-BA2 were 2.61 × 10−3 and 2.82 × 10−3 M and limits of detection were 7.83 × 10−4 and 8.47 × 10−4 M while sensitivities were as great as 5.06 × 109 and 2.89 × 109 M−1, respectively, indicating that the method is suitable for practical analysis.

Mimicking mechanical response of natural tissues. Strain hardening induced by transient reticulation in lactose-modified chitosan (chitlac)

The effect of transient cross-links has been explored on a lactose-modified chitosan, which previously had shown interesting biological features. The presence of galactose side chains and of the polyol spacer resulted particularly appealing for the reticulation by borate ions. The interaction between chitlac and borax was investigated by means of 11B NMR while rheology pointed to a marked non-linear behavior depending on the amount of borax added to the system. The presence of limited amount of cross-linking ion led to dilatant behavior when the steady flow curve was measured. In addition, strain stiffening was noticed on elastic response upon exceeding a critical stress, indicating a transient nature in the formation of the cross-links. The non-linear response of chitlac in the presence of borax compared surprisingly well with the one showed by proteins composing the natural ECM pointing at a possible role of mechanotransduction in the biological significance of the modified chitosan.

Computational Insights into Biomimetic CO2 Hydration Activities of (Poly)borate Ions

Borate-based compounds have been observed to be CO2 capture agents in natural and synthetic setups. Carbon capture in such systems has been proposed to take place via hydration of CO2 resulting in bicarbonate ion formation. Several experimental studies have reported borate-based catalysts for CO2 hydration reaction, and the mechanism of the reaction has been proposed to follow the enzymatic carbonic anhydrase action. In view of the absence of detailed physical insights into the mechanistic aspects of borate-catalyzed CO2 hydration, computational investigations were carried out in this study under the density functional theory framework to explain the mechanism of the reaction over borate-based systems. Three borate-based systems, namely, borate ions, triborate ions, and tetraborate ions, were tested as the catalysts for the aqueous phase carbon capture reaction. Free energy landscapes provided the details of the elementary steps of the reaction, concluding the mechanism of the reaction to be indeed biomim...

Theoretical Analysis of Critical Flowable Physical Gel Cross-Linked by Metal Ions and Polyacrylamide-Derivative Associating Polymers Containing Imidazole Groups.

When the polymer chains are cross-linked by physical bonds having a finite lifetime, the relaxation time and viscosity do not diverge at the gel point though percolation occurs. These undivergent quantities are related to the finite-sized “largest relaxed cluster,” which can relax before it breaks. Its size is the key rheological parameter characterizing of the critical physical gels. In order to evaluate this characteristic size, we propose here a generalized phenomenological model for the viscoelasticity of critical physical gels. We apply the theory to the previously reported experimental result for the physical gel consisting of polyacrylamide-derivative associating polymers containing imidazole groups cross-linked by coordination bonds with Ni ions. We successfully estimate the size of the largest relaxed cluster and the fractal dimension. The size is in good agreement with that estimated from the mean-square displacement of probe particles at the gel point by microrheological measurement. We also compare this system with the poly(vinyl alcohol) hydrogel cross-linked by borate ions, and show that the difference in the cluster structures is originating from the differences of precursor chain properties such as overlap concentration and radius of gyration and of the cross-linking states in these systems.

Combined effects of lithium and borate ions on the hydration of calcium sulfoaluminate cement

This work investigates the combined influence of borate and lithium ions on the hydration of two calcium sulfoaluminate (CSA) cements containing 0 or 10wt% gypsum. On the one hand, borates are known to retard CSA cement hydration due to the rapid precipitation of ulexite. On the other hand, lithium ions accelerate CSA cement hydration thanks to the fast precipitation of Li-containing aluminum hydroxide. When borates and lithium are present simultaneously, these two mechanisms are superimposed. With a gypsum-free cement, a third process is additionally observed: lithium promotes the initial precipitation of a borated AFm phase which is later converted into a borated AFt phase when hydration accelerates. Lithium salts can counteract the retardation by sodium borate. However, their influence is limited once a sufficient amount of Li-containing Al(OH)3 seeds is formed. For the CSA cements under investigation, the threshold lithium concentration is close to 0.03mmol/g of cement and similar with or without borate.

First-principles calculations and re-analysis of optical spectra and electron paramagnetic resonance parameters for Yb3+ in YAl3(BO3)4 crystal

In this paper, the energy levels of Yb3+ ions in yttrium aluminum borate (YAB) crystal were calculated from a first-principles approach with an optimized defect structure obtained from the WIEN2k package and a traditional fitting method using a more reliable computer package. The calculated results were then compared with those obtained from a re-calculation using the values of parameters given by some previous researchers. Three types of likely mistakes in the previous researcher's paper, namely over fitting, incorrect use of irreducible representation, and errors in the calculations for the EPR parameters were clearly identified and effectively rectified in this paper. The electron paramagnetic resonance (EPR) parameters, which included g factors like g// and g⊥ and hyperfine structure constants A// and A⊥, were also calculated through the perturbation method and compared with some observed values available in literature. There was reasonable agreement found with the experimental values which lay between the values obtained from the first-principles calculation (g//=4.000 and g⊥=1.391; A//=1032 and A⊥=360 in 10−4 cm−1 for 171Yb3+) and those from the fitting approach (g//=3.612 and g⊥=1.702; A//=867 and A⊥=470 in 10−4 cm−1 for 171Yb3+).

Solution Chemistry for Actinide Borate Species to High Ionic Strengths: Equilibrium Constants for AmHB4O72+ And AmB9O13(OH)4(cr) and Their Importance to Nuclear Waste Management

ABSTRACTBorate is present in natural groundwaters and borate is also released into groundwaters when borosilicate glass, waste form for high level nuclear waste, is corroded. Borate can form an aqueous complex, AmHB4O72+, with actinides in +III oxidation state. In this work, we present our evaluation of the equilibrium constant for formation of AmHB4O72+ and the associated Pitzer interaction parameters at 25°C.Using Nd(III) as an analog to Am(III), solubility data of Nd(OH)3(s) in NaCl solutions in the presence of borate ion from the literature, is used to determine Am(III) interactions with borate. The log10K for the formation reaction is 37.34. This evaluation is in accordance with the Waste Isolation Pilot Plant (WIPP) thermodynamic model in which the borate species include B(OH)3(aq), B(OH)4–, B3O3(OH)4–, B4O5(OH)42–, and NaB(OH)4(aq). The WIPP thermodynamic database uses the Pitzer model to calculate activity coefficients of aqueous species.In addition, the equilibrium constant for dissolution of AmB9O13(OH)4(cr) at 25oC is evaluated from the solubility data on NdB9O13(OH)4(cr) in NaCl solutions, again using Nd(III) as an analog to Am(III). The log10K for the dissolution reaction is –79.30. In the evaluation for log10K for the dissolution reaction, AmHB4O72+ is also considered.The equilibrium constant and Pitzer parameters evaluated by this study will be important to describe the chemical behavior of Am(III) in the presence of borate in geological repositories.

PEO Film Formation Behavior of Al1050 Alloy Under Direct Current in an Alkaline Electrolyte

This work demonstrates arc generation and anodic film formation behaviors on Al1050 alloy during PEO (plasma electrolytic oxidation) treatment under a constant direct current in an alkaline electrolyte containing silicate, carbonate and borate ions. Only one big arc more than 2 mm diameter was generated first at the edges and it was moving on the fresh surface or staying occasionally at the edges, resulting in the local burning due to generation of an extremely big orange colored arc at the edges. Central region of the flat surface was not fully covered with PEO films even after sufficiently long treatment time because of the local burning problem. The anodic oxides formed on the flat surface by arcing once were found to consist of a number of small oxide nodules with spherical shape of <TEX>$3{\sim}6{\mu}m$</TEX> size and irregular shapes of about <TEX>$5{\sim}10{\mu}m$</TEX> width and <TEX>$10{\sim}20{\mu}m$</TEX> length. The anodic oxide nodules showed uniform thickness of about <TEX>$3{\mu}m$</TEX> and rounded edges. These experimental results suggest that one big arc observed on the specimen surface under the application of a constant direct current is composed of a number of small micro-arcs less than <TEX>$20{\mu}m$</TEX> size.

B(OH)4- hydration and association in sodium metaborate solutions by X-ray diffraction and empirical potential structure refinement.

X-ray diffraction is used to study the structure of aqueous sodium metaborate solutions at salt concentrations of 1, 3, and 5 (oversaturated) mol dm-3. The X-ray structure factors are subjected to empirical potential structure refinement (EPSR) modelling to extract the individual site-site pair correlation functions, the coordination numbers, and the spatial density functions (three-dimensional structure) of ion hydration and association as well as solvent water in the borate solutions. The sodium ion is surrounded on average by (5.4 ± 0.7), (4.6 ± 1.0), and (3.7 ± 1.2) water molecules at 1, 3, and 5 mol dm-3, respectively, with the Na-O (H2O) distance of 2.34 Å. The decrease in hydration number of the sodium ion is compensated by direct binding of the oxygen atom of the borate ion, B(OH)4-, with the average coordination number of (0.2 ± 0.5), (1.0 ± 0.8), and (2.1 ± 1.3) at the Na-O(B) distance of 2.34 Å to keep the octahedral hydration shell of the sodium ion. The average number of water molecules around the borate ion is (13.9 ± 1.8), (14.2 ± 1.8), and (16.1 ± 2.4) per borate ion with increasing salt concentration with the B-O(H2O) distance of 3.72 Å. The number of nearest-neighbour water molecules around a central water molecule in a solvent decreases as (4.8 ± 1.2), (3.8 ± 1.1), and (2.8 ± 1.1) with an increase in salt concentration with the O(H2O)-O(H2O) distance of 2.79 Å. The Na+-B(OH)4- ion association is characterized by the Na-O(B) and Na-B pair correlation functions. The Na-B interactions are observed at 3.00 Å as a shoulder and 3.57 Å as a main peak in the site-site pair correlation function, suggesting two occupancy sites of Na+ with one for the edge-shared bidentate bonding and the other for the corner-shared monodentate bonding. The total number of Na-B interactions at 3.00 and 3.57 Å is consistent with that of the Na-O(B) interactions. The detailed three-dimensional structure of the ion hydration and association is visualized as a function of salt concentration. The structure and stability of [NaB(OH)4(H2O)6]0 clusters are further investigated by DFT calculations, and the most likely structure is proposed and cross-checked.

Potentiometric Determination of Moxifloxacin by ZnO Nanorodes Modified ion Selective Electrode

Potentiometric determination of moxifloxacin (Moxi) by ion selective electrode based on ZnO nanorods incorporation with HPβ-CD as sensing ionophore and (KTFPB) potassium tetrakis- (3,5(triflouromethyl) phenyl borate ion as anionic site (additive) in polyvinyl chloride (PVC) membrane, without inner reference solution was developed. The sensor shows nearly nernstian response over a concentration range ( 5 × 10-8 M to 1 × 10-2 M) with a slope of 21.9 ± 0.16 mv decade-1 of concentration with a limit of detection (LOD) 0.127 μM. The electrode exhibits a fast dynamic response of 2 s for a period of 6 months without significant change in its characteristics with excellent stability and sensitivity toward inorganic species. The method is accurate and precise as indicated by the mean recoveries 99.5% with RSD less than 2%. The proposed method was successfully applied for the determination of Moxi in pure form and its pharmaceutical formulations.

Microwave-induced production of boron-doped HAp (B-HAp) and B-HAp coated composite scaffolds

The aim of the present study is to produce boron (B) doped hydroxyapatite (B-HAp), which has an osteoinductive property, and investigate in-vitro osteogenesis potential of B-HAp coated chitosan (B-HAp/Ch) scaffolds. At first, B-HAp was produced by the interaction of ions within the concentrated synthetic body fluid containing boron (B-SBF) with microwave energy. Boron incorporation into HAp structure was performed by the substitution of borate ions with phosphate and hydroxyl ions. Experiments were carried out with different microwave powers and exposure times, and optimum conditions for the production of B-HAp were determined. B-HAp precipitated from B-SBF by 600W microwave power has 1.15±0.11% (w/w) B, 1.40 (w/w) Ca/P ratio, 4.30±0.07% (w/w) carbonate content, 30±4nm rod-like morphology and bone-like amorphous structure. Then, chitosan scaffolds that were prepared by freeze-drying were coated with B-HAp by performing microwave-assisted precipitation in the presence of scaffolds to improve their bioactivities and mechanical properties. The formation of apatite layer and the penetration of apatites into the pores were observed by scanning electron microscopy (SEM). Fourier Transform Infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD) analysis also confirmed the presence of B-HAp layer. As control, hydroxyapatite coated chitosan scaffolds (HAp/Ch) produced at the same conditions were used. The results of cell culture studies indicated that B releasing from scaffolds enhances proliferation and osteoblastic differentiation of MC3T3-E1 cells. This work emphasized the importance of the use of B within the scaffolds for enhancing in-vitro bone tissue engineering applications.

Phase transitions and exchange interactions in the SmCr3(BO3)4crystal

Spectroscopic investigation and specific heat and magnetic susceptibility measurements of SmCr 3 (BO 3 ) 4 crystals were performed. The spectra of the Sm 3+ and Cr 3+ ions in samarium chromium borate were calculated and parameters of the exchange interactions between the nearest chromium ions, chromium and samarium ions were determined. Three phase transitions were observed at the temperatures T 1 = 7.8 ± 0.5 К, T 2 = 6.7 ± 0.5 К, and T 3 = 4.3 ± 0.2 К, their nature is discussed. The crystal structures with different space symmetry groups R 32 and C 2/ c were found to coexist in a SmCr 3 (BO 3 ) 4 single crystal.