Boron removal by means of adsorption processes with magnesium oxide — Modelization and mechanism

The boron adsorption process, in borate ion form, onto magnesium oxide was described in terms of mathematical equations and, taking into account the knowledge acquired by means of experimental data, the most probable mechanism of boron removal process was proposed. The modelization has been carried out by establishing Langmuir adsorption isotherms and kinetic law. Upward convex curves are observed indicating that the process is advantageous towards boron adsorption. Moreover, the adjustment of experimental data to their corresponding functions leads to highly satisfactory correlations for all the studied conditions and pseudo-second-order kinetic model was observed. As for the mechanism of the adsorption process, a superficial process of chemosorption comprising three stages or reactions is proposed: 1) the hydration reaction of magnesium oxide as it is in contact with the aqueous solution to yield a magnesium hydroxide gel over the surface of which the active points for adsorption are located, 2) the alkalisation reaction of the solution due to the acid-base reaction between magnesium oxide and water and 3) the stereospecific chemical reaction between borate ions and active centres. This mechanism develops with time to reach stabilisation and leads to the formation of an adsorption monomolecular layer that is typical in chemosorption processes, as well as in systems following Langmuir adsorption isotherms and pseudo-second-order kinetics.     

Fixed‐Bed Adsorption Study for Fumaric Acid Removal from Aqueous Solutions by Amberlite IRA‐400 Resin

A fixed‐bed adsorption study was carried out by using a strong base anion‐exchange resin (Amberlite IRA‐400) for the removal of fumaric acid from aqueous solutions. The breakthrough curves were obtained as a function of flow rate, temperature, feed pH, and inlet fumaric acid concentration. The total adsorption capacity and the percent fumaric acid removal of the resin were calculated. The Yoon‐Nelson model was applied to the experimental data to predict the breakthrough curves and to determine the characteristic column parameters required for process design. The breakthrough curves fit the model predictions well.     

Monodisperse‐porous N‐methyl‐D‐glucamine functionalized poly(vinylbenzyl chloride‐co‐divinylbenzene) beads as boron selective sorbent

To generate a new sorbent with high boron adsorption capacity, we synthesized monodisperse‐porous poly(vinylbenzyl chloride‐co‐divinylbenzene), poly(VBC‐co‐DVB), beads 8.5 μm in size by a new “modified seeded polymerization” technique. By using their chloromethyl functionality, the beads were derivatized by a simple, direct reaction with a boron‐selective ligand, N‐methyl‐D ‐glucamine (NMDG). The selection of poly(VBC‐co‐DVB) beads as a starting material allowed to obtain high boron sensitive‐ligand density on the beads depending on their high chloromethyl content. In the batch adsorption runs performed using NMDG‐attached poly(VBC‐co‐DVB) beads as sorbent, boron removal was efficiently performed in a wide pH range between 4 and 11. Quantitative boron removal was observed with the sorbent concentration of 4 g/L. In the same runs, plateau value of equilibrium adsorption isotherm was obtained as 14 mg boron/g beads. Relatively higher boron adsorption was explained by high ligand density and high specific surface area of the sorbent. Boron adsorption isotherms were analyzed using Langmuir and Freundlich models. In the kinetic runs performed for boron removal, the equilibrium was attained within 10 min at a value of 98%. The fast kinetic behavior was explained by the smaller particle size and enhanced porosity of the new sorbent. Infinite solution volume model and unreacted core model were used to evaluate boron adsorption onto the NMDG‐attached poly(VBC‐co‐DVB) beads. The results indicated that the adsorption process is controlled by the particle‐diffusion step. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Electrochemical removal of boron from water: Adsorption and thermodynamic studies

The present work provides an electrochemical removal of boron from water and its kinetics, thermodynamics, isotherm using mild steel and stainless steel as anode and cathode respectively. The various operating parameters on the removal efficiency of boron were investigated, such as initial boron ion concentration, initial pH, current density and temperature. The results showed that the optimum removal efficiency of 93.2% was achieved at a current density of 0.2 A dm^?2 at pH of 7.0. First‐, second‐order rate equations, Elovich and Intraparticle models were applied to study adsorption kinetics. Adsorption isotherms of boron on Fe(OH)₃ were determined and correlated with isotherm equations such as Langmuir, Freundlich and D‐R models. Thermodynamic parameters, such as standard Gibb's free energy (ΔG°), standard enthalpy (ΔH°) and standard entropy (ΔS°), were also evaluated by Van't Hoff equation. The adsorption process follows second‐order kinetics. The adsorption of boron preferably fits with Langmuir adsorption isotherm suggesting monolayer coverage of adsorbed molecules. The adsorption of boron onto Fe(OH)₃ was found to be spontaneous and endothermic. © 2011 Canadian Society for Chemical Engineering     

Boron removal by means of chemical precipitation with calcium hydroxide and calcium borate formation

Boron removal was investigated by chemical precipitation from aqueous solutions containing boron using calcium hydroxide. pH, initial boron concentration, amount of Ca(OH)₂, stirring speed and solution temperature were selected as operational parameters in a batch system. The highest boron removal efficiency was reached at pH 1.0. Increasing initial boron concentration and amount of calcium hydroxide raised to boron removal efficiency. Boron removal efficiency was highest at a stirring speed of 150 rpm. The most important parameter affecting boron removal efficiency was solution temperature. Increasing solution temperature increased importantly boron removal. XRD analysis showed that CaB₃O₃(OH)₅·4H₂O, which is a borate mineral called inyoite, occurred between Ca(OH)₂ and borate ions. As a result of the obtained experimental data, when the optimum operational conditions were selected, over 96% of boron removal efficiency was reached by this method.     

Efficient separation of (R)‐(‐)‐mandelic acid biosynthesized from (R,S)‐mandelonitrile by nitrilase using ion‐exchange process

BACKGROUND: (R)‐(‐)‐Mandelic acid (R‐MA) is an important intermediate and chiral regent with broad uses. An efficient method for the separation of R‐MA from the bioreaction mixture with high yield is of great importance, thus, the main objective of this work is to investigate the recovery of R‐MA using an ion‐exchange process. RESULTS: The equilibrium isotherms for the separation of R‐MA by resin HZ202 were obtained in the pH range 5.0–9.0 and temperature range 25–35 °C. The equilibrium data are well fitted by the Langmuir isotherm. Batch kinetic experiments showed that the mobility of R‐MA^? in solution was rapid and the R‐MA^?/OH^? ion‐exchange process reached equilibrium after about 60 min. Adsorption kinetics were analyzed by a linear driving force mass‐transfer model, yielding good prediction of the kinetic behavior. In fixed bed column experiments, the breakthrough curves of R‐MA from the solution on resin HZ202 were determined at different flow rates and R‐MA was eluted with different concentrations of HCl. A favorable breakthrough curve and optimal eluant concentration were obtained. The results were used for the separation of R‐MA biosynthesized from (R,S)‐mandelonitrile with nitrilase, and separation was successfully achieved with above 90% recovery yield. CONCLUSION: Resin HZ202 presents favorable behavior for the recovery of R‐MA, in terms of capacity, kinetics, affinity, and susceptibility to regeneration. The results of this study provide an efficient method for R‐MA recovery from bioreaction mixture and could potentially be used in industry. Copyright © 2010 Society of Chemical Industry     

Separation of gibberellic acid (GA3) by macroporous adsorption resins

Adsorption rates of gibberellic acid (GA3) on S‐8 and X‐5 resins were measured with the results indicating that the adsorption attained equilibrium for adsorption times longer than 4 h. The adsorption isotherms of GA3 on AB‐8, X‐5, S‐8, D4020, D3520, D4006 and NKA‐9 were determined at 20 °C. S‐8 resin had the largest solid/liquid distribution coefficient of 10.5 and was selected as the adsorbent for separation of GA3 from the aqueous solution. The breakthrough curves of GA3 from the aqueous solution on S‐8 resin were determined at different flow rates. The dynamic adsorption capacity of GA3 was measured as 4.56 mgg⁻¹ wet resin at a flow rate of 0.5 cm³min⁻¹. GA3 adsorbed on S‐8 resin was eluted with several eluents with 80% (v%) acetone aqueous solution having the best desorption performance. When GA3 was adsorbed by S‐8 resin from the fermentation liquor, the dynamic adsorption capacity of GA3 was increased to 12.02 mgg⁻¹ wet resin in virtue of the salting‐out effect of the ammonium sulfate in the fermentation liquor. The yield of GA3 was above 90% after GA3 was adsorbed by S‐8 resin from the fermentation liquor at pH 2 and eluted by 80% (v%) acetone aqueous solution. The GA3 concentration was increased seven‐fold from the fermentation liquor after an adsorption and desorption cycle. © 2000 Society of Chemical Industry     

Adsorptive Entfernung von Schwefelverbindungen aus Erdgas

Prior to the technical use of natural gas, toxic and corrosive components need to be removed. This work provides results from dynamic fixed‐bed experiments for the adsorption of sulfurous compounds, CO₂ and H₂O from carrier gas (CH₄ or N₂) on two adsorbents (zeolite 5A, silica‐alumina‐gel) used in industrial applications. The breakthrough curves were measured at ambient conditions (298 K, 1.3 bar) in a trace level concentration range up to 2000 mol‐ppm. Adsorption isotherms were derived using mass balances and a simple linear driving force model was fitted to the curves. Good agreement of experimental data and model calculation was obtained.     

AMINE REMOVAL FROM WASTE WATER BY LIGAND EXCHANGE

Ligand exchange is a process in which a substance is removed from solution by complexing with a metal ion held on an ion exchange resin. This paper presents basic data on separation of ethanolamine and butyl amine from dilute aqueous solution by complexing with copper(II) ion held on a carboxylic acid type resin. Experimental equilibrium curves and ligand exchange breakthrough curves are presented for the two amines. The equilibrium curves are satisfactorily represented by an empirical Langmuir isotherm. The breakthrough curves are successfully modelled by the Thomas mathematical formulation using a mass transfer controlled rate mechanism. The ligand exchange process may be useful commercially for removal of amines from aqueous waste streams.     

AMINE REMOVAL FROM WASTE WATER BY LIGAND EXCHANGE

Ligand exchange is a process in which a substance is removed from solution by complexing with a metal ion held on an ion exchange resin. This paper presents basic data on separation of ethanolamine and butyl amine from dilute aqueous solution by complexing with copper(II) ion held on a carboxylic acid type resin. Experimental equilibrium curves and ligand exchange breakthrough curves are presented for the two amines. The equilibrium curves are satisfactorily represented by an empirical Langmuir isotherm. The breakthrough curves are successfully modelled by the Thomas mathematical formulation using a mass transfer controlled rate mechanism. The ligand exchange process may be useful commercially for removal of amines from aqueous waste streams.     

Boron Isotope Fractionation in Liquid Chromatography with Boron-Specific Resins as Column Packing Material

Abstract

Boron-specific resins with n-methyl glucamine as the functional group were used as column packing material of liquid chromatography for boron isotope separation. The shapes of chromatograms in reverse breakthrough experiments were heavily dependent on the pH of the eluents, and there existed a pH value at which a chromatogram of the displacement type was realized nearly ideally. The value of the single-stage separation factor for the boron isotopes varied between 1.010 and 1.022, depending on the temperature and the form of the resins. The existence of the three-coordinate boron species in addition to the four-coordinate species in the resin phase is suggested.     

Adsorption Equilibrium and Kinetics of the Parex' Feed and Desorbent Streams from Batch Experiments

The adsorption of the main components of the Parex process, i.e., p‐xylene, m‐xylene, o‐xylene, ethylbenzene, p‐diethylbenzene, and toluene, was studied in a batch adsorber operating under the conditions of an industrial unit (177 °C, 9 bar). Prior to each experiment, the faujasitic‐type adsorbent was pretreated under helium flow to control the hydration level of the adsorbent. The experimental uptake curves were used to determine adsorption equilibrium data, which were fitted with Langmuir‐type isotherms. A mathematical model in which the macropore diffusion is the rate‐controlling mechanism, satisfactorily describes the experimental uptake curves.     

Preparation of metal ions impregnated polystyrene resins for adsorption of antibiotics contaminants in aquatic environment

In this study, the strong‐acid polystyrene resin D001 was modified by impregnation with metal ions Fe³⁺, Cu²⁺, and Zn²⁺ to prepare new kinds of sorbents. The modified D001 was characterized by N₂ sorption–desorption isotherms, X‐ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The sorption performance of the metal modified resins for removal of antibiotics tetracycline (TC) and doxycycline (DC) from aquatic environment was investigated and excellent sorption capability with more than 98% removal ratio was observed for these resins after modification. Although these modified resins also presented pH‐dependent sorption, they showed much better flexibility with pH fluctuation than those of the unmodified original D001, and extremely strong sorption capability was exhibited in a wide range of pH 2–8 for both TC and DC. Pseudo‐second‐order kinetic equation described the sorption process more reasonably than pseudo‐first‐order equation. Langmuir isotherm model provided the best match to the equilibrium data with monolayer maximum sorption capacity of 417–625 mg g^?1 under 288–318 K. The sorption capacity decreased with the increase of ionic strength of NaCl. The main sorption mechanism was proposed to be surface complexation, cation bridge interaction and electrostatic attraction/competition between antibiotics and metal modified resins. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41803.     

Adsorptive removal of uranium from water by sulfonated phenol–formaldehyde resin

Adsorption characteristics of a sulfonated phenol‐formaldehyde resin (SPR) have been studied for U removal from aqueous solution by means of batch method. Adsorption experiments have been carried out as a function of contact time, solution/adsorbent ratio, particle size and pH. Adsorption isotherm has been evaluated by changing adsorbent dosage in the range of 0.04–80 g/L at an initial uranyl nitrate concentration of 0.05 mol/L. The enormous adsorption capacity of 0.29 mol/g estimated from the plateau region of the S shaped isotherm is well comparable the Langmuir capacity of 0.31 mol/g. Equilibrium data are also adequately well described by the Freundlich and the Dubinin‐Radushkevich (D‐R) isotherm equations. The parameters of the isotherms and pH dependency of distribution coefficients (K_D) indicate that polymeric uranyl chains form on bidentate surface complex as a result of solute–solute interactions on the adsorbent surface. Both desorption and elution studies show that uranyl chains are irreversibly bounded on the SPR. Kinetic curves having a fast initial part followed by a slower process well fit both McKay model based on two‐resistance diffusion and Nernst‐Plank model with single diffusion coefficient. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

An empirical model for kinetics of boron removal from boron-containing wastewaters by ion exchange in a batch reactor

In this study, it was investigated boron removal from boron containing wastewaters prepared synthetically. The experiments in which Amberlite IRA 743, boron specific resin was used was carried out in a batch reactor. The ratio of resin/boron solution, boron concentration, stirring speed and temperature were selected as experimental parameters. The obtained experimental results showed that percent of boron removal increased with increasing ratio of resin/boron solution and with decreasing boron concentration in the solution. Stirring speed and temperature had not significant effects on the percent of total boron removal, but they increased the starting boron removal rate. As a result, it was seen that about 99 % of boron in the wastewater could be removed at optimum conditions. On the other hand, the process kinetics were predicted by using heterogeneous fluid-solid reaction models. It was seen statistically that the kinetics of this process agreed the pseudo- second order model, as follows: X_Bl(1−X_B) = 11,241.5[OH][C]^−1.76[S/L]^2.17exp(−19,57l.2/RT)t^1.24     

Propylen/Propan‐Trennung im Festbettadsorber und durch Membranpermeation

The metal‐organic framework Mg₂(dhtp) with the linker dihydroxyterephthalate is known as MOF‐74 or CPO‐27. Mg₂(dhtp) has been synthesized as powder to measure breakthrough curves in a fixed‐bed adsorber and adsorption isotherms, and as a supported thin membrane layer for permeation studies. The measurement of the breakthrough curves of the binary propylene/propane mixture shows that separation with the fixed bed adsorber is possible. Propylene shows a higher affinity to Mg₂(dhtp). Although the single gas propane flux is slightly higher than the one of propylene, the binary propane/propylene mixture is not separated.     

Batch and fixed‐bed column adsorption of Cu(II), Pb(II) and Cd(II) from aqueous solution onto functionalised SBA‐15 mesoporous silica

Functionalised SBA‐15 mesoporous silica with polyamidoamine groups (PAMAM‐SBA‐15) was successfully prepared with the structure characterised by X‐ray diffraction, nitrogen adsorption–desorption, Fourier transform infrared spectra and thermogravimetric analysis. PAMAM‐SBA‐15 was applied as adsorbent for Cu(II), Pb(II) and Cd(II) ions removal from aqueous solution. The effects of the solution pH, adsorbent dosage and metal ion concentration were studied under the batch mode. The Langmuir model was fitted favourably to the experimental data. The maximum sorptive capacities were determined to be 1.74 mmol g^?1 for Cu(II), 1.16 mmol g^?1 for Pb(II) and 0.97 mmol g^?1 for Cd(II). The overall sorption process was fast and its kinetics was fitted well to a pseudo‐first‐order kinetic model. The mean free energy of sorption, calculated from the Dubinin–Radushkevich isotherm, indicated that the sorption of lead and copper, with E > 16 kJ mol^?1, followed the sorption mechanism by particle diffusion. The adsorbent could be regenerated three times without significant varying its sorption capacity. A series of column tests were performed to determine the breakthrough curves with varying bed heights and flow rates. The breakthrough data gave a good fit to the Thomas model. Maximum sorption capacity of 1.6, 1.3 and 1.0 mmol g^?1 were found for Cu(II), Pb(II) and Cd(II), respectively, at flow rate of 0.4 mL min^?1 and bed height of 8 cm, which corresponds to 83%, 75% and 73% of metallic ion removal, respectively, which very close to the value determined in the batch process. Bed depth service time model could describe the breakthrough data from the column experiments properly. © 2012 Canadian Society for Chemical Engineering     

Experimental study and modelling of an azo colourant dynamic adsorption onto functional cross-linked chitosan/ceramic particles in a fixed bed column

The use of azo dyes in industrial activities generates a large volume of contaminated wastewater; these pollutants in water bodies affect aquatic biota and human health. A functional biocomposite sorbent material was synthesized using cross-linked chitosan with oxalic acid that forms a coating on alumina ceramic particles (AOCh). The removal of Reactive Red 195, a reactive azo dye, using a fixed-bed adsorption column filled with this material was tested. AOCh was physico-chemically characterized by Fourier transform infrared spectroscopy–total attenuated reflection (FTIR-ATR), scanning electron microscopy–energy dispersion spectrometry X-ray (SEM-EDS), X-ray diffraction (XDR), thermo-gravimetric analysis (TGA), and Z-potential. The dynamic adsorption performance was analyzed from experimental breakthrough curves obtained in fixed-bed columns by modifying different operating conditions (bed depth, volumetric flow rate, and dye inlet concentration). Equilibrium adsorption isotherms were determined under dynamic conditions and compared with batch results. The maximum adsorption capacity of the dynamic equilibrium isotherm obtained from the continuous assays was 331 mg/g; this value was the highest in comparison to other tested materials reported in the literature. Different dynamic adsorption models were applied to fit experimental data, including Thomas, Bohart–Admas, Yoon–Nelson, logistic general model, bed depth surface time (BDST), and modified dose response (Yan) models. A critical analysis of these equations was presented, showing the equivalences and the relationship among the coefficients. The Yan model achieved the highest level of agreement between the experimental and predicted values of the breakthrough curves. The use of this model enables scaling-up the industrial process for dye removal. The present work proposed a novel biosorbent material and contributes to the analysis of industrial dye removal under dynamic conditions.     

A Convenient Approach Toward Fluoride Sorption by Calix[4]arene Based Sorbent

The present study describes the sorption of fluoride on a potential and newly synthesized p-tetraaminocalix[4]arene based resin (p-TAC4 resin). The p-TAC4 resin was synthesized via immobilization of p-tetranitrocalix[4]arene (p-TNC4) onto the Merrifield resin followed by catalytic reduction with SnCl₂/EtOH/HCl. The p-TNC4 and p-TAC4 resins were characterized using FT-IR, elemental analysis, and scanning electron microscopy (SEM). Fluoride removal capability from the aqueous media of the p-TAC4 resin has been evaluated through batch sorption study. The effect of pH, sorbate concentration, sorbent dosage, and contact time on fluoride removal was evaluated. The Langmuir (L), Freundlich (F), and Dubinin–Radushkevich (D-R) isotherms revealed that the fluoride on p-TAC4 resin follows physiosorption mechanism. All the results support and emphasize that the p-TAC4 resin is an effective sorbent for the removal of fluoride from the aqueous environment at a wide range of pH. The study may confer its impact on human health, reinstate polluted sites and other fields such as analytical, clinical, as well as material sciences.     

Separation of Boron from Geothermal Water Using a Boron Selective Macroporous Weak Base Anion Exchange Resin

In this study, batch and column mode tests were performed to evaluate the efficiency of boron removal from geothermal water containing 10-11 mg B/L using Lewatit MK 51 which is a macroporous weak base anion exchange resin with polyhydroxyl groups showing a very high selectivity and capacity for boron. The optimum resin amount for boron removal from geothermal water was determined as 4.0 g resin/L-geothermal water. It was found that the sorption kinetics was influenced by particle size of the resin and temperature. The stirring rate had almost no effect on kinetic performance of the resin. According to the results of column-mode study performed, breakthrough and total capacities of the resin were obtained as 2.75 and 4.98 mg/mL-resin, respectively.