Sorption Of Borate Research Articles

The Boron Budget in Waters of the Mono Basin, California

Mono Lake in eastern California has the highest natural boron concentrations measured in a natural water body. Inputs to Mono Lake are from creeks that drain from the Sierra Nevada, accounting for over 80% of the total water input, and springs account for most of the rest of the water budget. We measured boron concentrations and isotope compositions of water sources in the lake and lake water collected over several seasons. The δ11B offset of at least +2.5‰ between Mono Lake water compared to its inputs suggests that, like seawater, the boron isotopic composition of the lake is influenced by the removal of light boron by coprecipitation and/or sorption of borate. Given the alkalinity of the lake, boron fractionation likely occurs before or as the water sources enter the lake. The famous tufa towers around the lake are a physical representation of a ‘chemical delta’ that alters the boron isotopic composition of the source fluids as they enter the lake. Based on different combinations of the measured end members, the residence time of boron in Mono Lake is estimated to be within the range of 5~80 ka.

Double-Edged Effect of Humic Acid on Multiple Sorption Modes of Calcined Layered Double Hydroxides: Inhibition and Promotion.

Layered double hydroxides (LDHs) are a typical class of anionic clay minerals whose structural memory effect has been widely used in pollutant adsorption. However, the influencing mechanism of humic acid (HA) on the structural memory effect in adsorption is not clear. In this study, HA was extracted from black soil and sediments, and its effect on the structural memory effect of LDHs with different divalent metals was evaluated in adsorption. Borate complexed with HAs and HAs promoted the dissolution of magnesium-calcined LDHs (Mg-CLDH), which enhanced their adsorption rate by Mg-CLDH. However, the adsorbed HA caused a decline in the crystallinity of the regenerated Mg-LDH and an incomplete structural transformation, thereby resulting in decreased adsorption capacity. After the complexation of HAs with borate, the resulting compound was adsorbed on the surface of Zn-CLDH. The adsorption rate of borate was effectively improved in the initial stage, but at the same time slowed down the hydration and structural regeneration of Zn-CLDH. Meanwhile, the surface-adsorbed HAs also prevented borate from entering the newly formed layer inside the particles and led to a significant decrease in adsorption performance. When Ca-CLDH was used to adsorb borate, the process mainly occurred through the formation of ettringite. However, the presence of HAs enhanced the stability of the restructured LDHs and hindered the dissolution of Ca-CLDH and the reaction with B(OH)4- to form ettringite during the regeneration process, which severely inhibited the sorption of borate.

Removal of borate by layered double hydroxides prepared through microwave-hydrothermal method

Layered double hydroxide (LDH) is considered effective in borate removal from water solutions. In this work, LDHs were prepared by microwave-hydrothermal method, characterized by X-Ray diffraction (XRD) and transmission electron microscopy (TEM), and applied for borate removal from a water solution. The results suggested that the LDHs prepared by microwave-hydrothermal method had the smallest particles size compared with other LDHs synthesized by urea and traditional hydrothermal method. Due to size reduction, the LDHs prepared by microwave-hydrothermal method had a higher borate sorption capacity. Based on the results of the XRD pattern and 11B-NMR, the sorption mechanism of M-LDH is discussed in the paper. Ion-exchange was the predominant mechanism of borate removal, but surface sorption likely accompanied this process. In addition, the data obtained for the sorption of the three types of LDHs fitted well with the pseudo-second-order kinetic model and Langmuir sorption isotherm with a high correlation coefficient. The sorption amount of borate by M-LDH was 2.16mmol/g, which is higher than that absorbed by U-LDH and H-LDH. Furthermore, the co-existing anion, especially carbonate, plays a role in hindering the sorption.

Ultrathin Mg-Al layered double hydroxide prepared by ionothermal synthesis in a deep eutectic solvent for highly effective boron removal

Ultra-thin layered double hydroxides (LDHs) with small particle sizes were synthesized using a deep eutectic solvent (DES). Products were characterized and applied towards boron removal. The results showed that the LDHs were successfully prepared in a DES (I-LDH) with a narrow diameter distribution (10–40nm) and a monolayer of around 0.7nm. Due to the reduced size, the interaction between the carbonate and metal layers was weak; therefore, I-LDH was found to have a higher sorption capacity to boron than that of LDH prepared through the urea method. The calcinated products (I-CLDH) also exhibited excellent sorption efficiency. The sorption mechanisms of I-LDH, I-CLDH, and U-CLDH were studied. Ion exchange was found to be the predominant mechanism of boron removal by I-LDH. However, for samples after calcination, two stages were present; the first stage included surface complexation and electrostatic attraction, and the second stage included immobilizing boric acid into Mg(OH)2 and attracting borate as an interlayer anionic species into the newly formed LDHs. In addition, pH was found to have a slight influence on sorption performance, although co-existing anions, especially carbonates, played a role in hindering sorption. Base on the Langmuir sorption isotherm, the sorption density of I-CLDH showed a good capacity for removing borate due to the ultrathin structure and high surface area. In addition, the influence of temperature, shaking speed, and dosage on borate sorption by I-CLDH has been studied. I-CLDH was also tested for borate removal from actual wastewater.

Mechanism of boron uptake by hydrocalumite calcined at different temperatures

Hydrocalumite (Ca-Al-layered double hydroxide (LDH)) was prepared and applied for the removal of borate. The properties of Ca-Al-LDH calcined at different temperatures were diverse, which affected the sorption density and mechanism of boron species. The sorption density increased with increase in calcined temperature and the sample calcined at 900°C (Ca-Al-LDH-900) showed the maximum sorption density in this work. The solid residues after sorption were characterized by 11B NMR, 27Al NMR, SEM, and XRD to investigate the sorption mechanism. Dissolution–reprecipitation was the main mechanism for sorption of borate in Ca-Al-LDH. For Ca-Al-LDH calcined at 300 and 500°C, regeneration occurred in a short time and the newly forming LDHs were decomposed to release Ca2+ ions and formed ettringite with borate. Two stages occurred in the sorption of boron by Ca-Al-LDH calcined at 900°C. In the first stage, boron species adsorbed on the alumina gel resulting from the hydration of calcined products. In this stage, borate was included as an interlayer anion into the newly forming LDHs in the following stage, and then immobilized as HBO32− into the interlayer, most the LDHs.

Fixed-bed column sorption of borate onto pomegranate seed powder-PVA beads: a response surface methodology approach

Pomegranate seed powder (PS) was functionalized with polyvinyl alcohol (PVA) and utilized for boron removal from the aqueous system. Results of Brunauer--Emmett--Teller (BET) surface area analysis and Boehm titration indicated notable decrease in total surface area and increase in acidic surface functional groups of PS after PVA modification. Enhanced sorption is indicative of complex formation between diol groups of the pomegranate seed powder--polyvinyl alcohol (PS–PVA) and borate ions. Under column test, the saturated sorption capacity of boron was noted to be dependent on flow rate and bed height. The developed central composite design (CCD) was adequate to elucidate the sorption mechanism. Mathematical modeling of the column data was conducted, and a modified-dose-response model was the most suitable to describe the breakthrough curve and observed to be consistent with CCD analysis. This is further supported by extensive error analyses conducted between the model predicted and experimental data.

One-step synthesis of layered double hydroxide-intercalated gluconate for removal of borate

The sorption of borate by ion exchange using a traditional layered double hydroxide (LDH) is affected by external conditions such as coexisting anions. Hydrotalcite intercalated with d-gluconate (G–LDH) was synthesized through a one-step microwave-assisted treatment and characterized by XRD, TEM, FTIR, TG/DTA and two-dimensional 11B NMR. Several factors that influence sorption of borate were investigated: gluconate content in the LDH, G–LDH dosage, coexisting anions, initial pH of borate solution and sorption temperature. The synthesized adsorbent exhibited a greater borate sorption rate than the traditional hydrotalcite (NO3–LDH) or a boron-specific resin. The maximum sorption capacity was 1.27mmol/g (obtained by fitting to the Langmuir model). The G–LDH sorption density increased with increasing initial borate concentration and adsorbent dosage. In the presence of 50mM sulfate, sorption of borate by NO3–LDH significantly decreased and no obvious sorption could be observed, whereas the sorption of borate by G–LDH was maintained at ∼0.57mmol/g. 11B NMR indicated that the sorption mechanism of borate by G–LDH is mainly through bischelate and monodentate types of complexation with borate. This mechanism is similar to that of CRB05, and fundamentally different from that of NO3–LDH.

Sorption of borate onto layered double hydroxides assembled on filter paper through in situ hydrothermal crystallization

Boric acid is known to be difficult to immobilize because it has a pKa of 9.23, which means it is present in a molecular form in most aqueous environments and can be changed in the structure and nature with the change of the environmental conditions. Layered double hydroxides (LDHs) are potential sorbents for borate. However, the drawbacks of using LDHs for borate removal are that they are affected by the presence of other anions and are difficult to separate from water. In the present work, novel composites of Mg–Al type of LDH, synthesized onto filter papers and then intercalated with gluconate (F-LDH-G) were prepared. LDH with interlayer of carbonate form was first immobilized onto the surface of filter paper (F-LDH-CO3) by in situ hydrothermal crystallization, and then ion-exchanged sequentially with chloride (F-LDH-Cl) followed by gluconate. The influence of the molar ratio of gluconate/LDH and reaction time on F-LDH-G synthesis was explored. Products were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and nuclear magnetic resonance as well as measurements of borate sorption. The optimal molar ratio of gluconate/LDH and reaction time for preparing F-LDH-G from F-LDH-Cl were 40 and 24h (F-LDH-G-40–24h), respectively. F-LDH-G-40–24h had higher sorption density and greater stability than both the original filter paper and the filter papers containing other LDHs, even in the presence of other anions. 11B NMR and XRD results indicate that the principal mechanism for borate immobilization on F-LDH-G-40–24h is complexation of gluconate with borate in both bischelate and monodentate forms. The novel composite is boron-specific and facilitates solid/liquid separation.

Effect of calcination temperature for magnesite on interaction of MgO-rich phases with boric acid

Abstract Magnesia (MgO), which can be obtained by calcination of natural magnesite, is one of the most effective known sorbents for borate in aqueous solutions. Here we examine the effect of calcination temperature on sorption of borate for MgO-rich phases produced by calcination of magnesite at 873–1373 K. Calcination at or above 1273 K produced a single magnesium oxide phase, whereas basic magnesium carbonates ( m MgCO 3 · n Mg(OH) 2 · x H 2 O) formed in association with magnesium oxide at or below 1073 K. Calcination temperature directly affected the efficiency of decarbonation of magnesium carbonate, and the solubility and basicity of magnesium oxide in the resultant calcined products. These factors (along with the boron concentration) essentially control the immobilization mechanism of borate on the calcined MgO-rich phases. After sorption of borate on products calcined at lower temperatures, different types of basic magnesium carbonates were formed that are less effective at immobilizing borate. At low borate concentrations, under saturation for magnesium borate hydrate (Mg 7 B 4 O 13 ·7H 2 O), co-precipitation of borate with Mg(OH) 2 predominates. However, as magnesium borate hydrate becomes supersaturated, both precipitation of Mg 7 B 4 O 13 ·7H 2 O and co-precipitation with Mg(OH) 2 contribute significantly to borate immobilization. Calcination temperature is a key practical factor affecting the borate sorption efficiency by changing the immobilization mechanism.

Temperature effect on the sorption of borate by a layered double hydroxide prepared using dolomite as a magnesium source

A hydrotalcite-like compound prepared through chemical deposition using calcined dolomite as the magnesium source (D-LDH) was applied to remove borate. D-LDH calcined at different temperatures was characterized by specific surface area measurements, scanning electron microscope images, X-ray diffraction (XRD) patterns, and Fourier transform infrared (FTIR) spectra to optimize the calcination temperature and maximize the sorption capacity of borate. Greater sorption density of borate was observed at higher calcination temperature, and the sample calcined at 700°C showed the maximum sorption density. In addition, the sorption density of borate by D-LDH calcined at 700°C decreased with increasing initial pH. The solid residues after the sorption of borate were characterized by FTIR, 11B NMR (11Boron nuclear magnetic resonance), and XRD to explore the sorption mechanism of the calcined product at 700°C.

Effect of natural dolomite calcination temperature on sorption of borate onto calcined products

Natural dolomite was calcined at 700–900°C under air and an Ar gas flow atmosphere to characterize its sorbency potential for borate. A sequential decarbonation occurred with increase in calcination temperature, that is, transformation of CaMg(CO3)2 to MgO and CaCO3 up to 700°C and CaCO3 to CaO from 700 to 900°C. The surface molar ratio of Ca/Mg decreased from 1.6 to 0.6 by calcination at more than 700°C, owing to the crystal growth of MgO toward the surfaces. MgO crystal growth is responsible for hydration leading to borate co-precipitation. The sorption density of borate was greater with the calcined products at 700°C than 800–900°C and under an Ar gas flow system rather than for static air at the same temperatures. The surface reactivity of the calcined dolomite with borate in the aqueous phase was affected by CO2 emitted in the decarbonation at higher temperatures.

Sorption of Borate and Fluoride on Bimetallic Mg-Al and Mg-Fe Oxides in Aqueous Solutions

Sorption of Borate and Fluoride on Bimetallic Mg-Al and Mg-Fe Oxides in Aqueous Solutions

Effect of the adsorption of lithium and borate species on the zeta potential of particles of cobalt ferrite, nickel ferrite, and magnetite

Zetametric measurements on suspensions of oxide particles (cobalt ferrite, nickel ferrite, and magnetite) representative of corrosion products from primary circuits of pressurized water reactors were performed at 25 and 70 °C in the presence of lithium and borate species. No effect of lithium ions was observed. Borate species cause a decrease of the isoelectric point (IEP), attributed to the sorption of borate as a negative complex MOB ( OH ) 3 − . A predictive model based on thermodynamic calculations ( 2 -p K and diffuse layer models) of the surface acidity constants from the data of acid–base titrations combined with an empirical relationship between the surface potential Ψ 0 and the ζ potential determined by zetametry was developed. A whole set of parameters valid at 25 °C, in a range of ionic strength between 10 −4 and 10 −2 mol L −1 and in a range of pH between 4 and 8, was determined for this model. Increase of temperature to 70 °C in the presence of borate results in a decrease of IEP for cobalt ferrite and an increase of the IEP for nickel ferrite.

Mössbauer and X-Ray Diffraction Investigations of a Series of B-Doped Ferrihydrites

X-ray diffraction and 57Fe Mossbauer spectroscopy are used to characterize the influence of borate on two-line ferrihydrite’s structure and develop likely models for its attachment. Particle sizes were in the 2–4 nm range, and as borate sorption increased, the ferrihydrite particle size decreased. The d-spacings of two-line ferrihydrite increased with increased borate adsorption. Isomer shift and quadrupole splitting exhibit slight increasing trends as well. Also, the phase transformation temperature of ferrihydrite to hematite is significantly raised due to borate coating of the surface. We suggest borate is sorbed onto the surface by attachment to the oxygen corners of the iron octahedra that are on the surface of the nanoparticles, placing boron in a tetrahedral molecular geometry.

Testing a mechanistic model. X. The effect of pH and electrolyte concentration on borate sorption by a soil

SUMMARYBorate sorption by a soil was measured with 0.01, 0.1, or 1.0 M sodium chloride as background electrolyte and samples of soil with a range of pH values achieved by incubating with either calcium carbonate or hydrochloric acid for 24 h at 60°C.Borate sorption generally increased with increasing pH. The more concentrated the electrolyte, the steeper the increase. At low pH, increasing the salt concentration decreased borate sorption; at high pH, it increased sorption. There was an intermediate pH at which salt had no effect on borate sorption. The point of zero salt effect on borate sorption was at a higher pH than the point of zero salt effect on pH. This result was explained by a mechanism in which borate ions react with variable charge surfaces which are heterogeneous and for which part of the heterogeneity is in the electric potential of the surfaces. It cannot be explained by mechanisms which do not take into account the effects of the electric potential of the reacting surfaces on the reaction with borate ions. Although the behaviour of borate was broadly consistent with that of other anions, it differed in that about half of the heterogeneity had to be allocated to the binding constant for borate ions. It was suggested that this was because reaction with organic matter was more important for borate than for other anions.