Breakthrough Capacity Research Articles

Purification of 89Sr from FBTR irradiated Yttria target by extraction chromatography using HDEHP impregnated XAD-7 resin

Abstract 89Sr is used in bone pain palliative care of cancer patients and the same is being produced presently via the 89Y(n, p)89Sr reaction by irradiating yttria target in Fast Breeder Test Reactor (FBTR). An efficient separation method was standardized for the removal of bulk yttrium target by extraction chromatography using di(2-ethylhexyl) phosphoric acid (HDEHP) impregnated on XAD-7 resin. In the present paper, the extraction behavior of Sr(II) and Y(III) was studied as a function of the concentration of nitric acid in the aqueous phase and concentration of HDEHP in the resin phase. The separation of Sr(II) and Y(III) was standardized using the above resins and the method was subsequently applied satisfactorily for the removal of yttrium from the dissolver solution of FBTR irradiated yttria pellet towards the purification of 89Sr. A baseline separation of 89Sr and Y was achieved. Leaching and breakthrough capacity studies were evaluated for the resins and it was established that the stability and capacity of the resins were satisfactory. The breakthrough capacity was found to be 12 mg Y(III) per gram of the HDHEP resin whereas the leaching studies established that the resins are stable for multiple cycle of operations.

Kinetics and adsorption equilibrium of some radionuclides on polyaniline/SiO2 composite

Abstract The sorption kinetics and equilibrium isotherms of zirconium, uranium, and molybdenum ions onto synthetic polyaniline/SiO2 composite (PAn/SiO2) have been studied using batch-sorption techniques. This study was carried out to examine the sorption behavior of the PAn/SiO2 for the removal of Zr(IV), U(VI), and Mo(VI) ions from an aqueous solution. The influence of some parameters on the sorption process was also studied. The maximum sorption for Zr(IV), U(VI), and Mo(VI) ions was achieved at 60 min shaking time. Langmuir isotherm model is the most representative for discussing the sorption process with a maximum sorption capacity of 24.26, 21.82, and 13.01 mg/g for Zr(IV), U(VI), and Mo(VI) ions, respectively. Kinetic modeling revealed that the sorption of all ions follows the pseudo-second-order kinetic model. The results demonstrated that both the external and intra-particular diffusion are taken into account in determining the sorption rate. Thermodynamic parameters like ΔG°, ΔH°, and ΔS° for the sorption process were evaluated. The synthetic composite has been successfully applied for the removal and recovery of U(VI) ions from real solution (monazite leachate) using a chromatographic column packed with PAn/SiO2 composite with a breakthrough capacity equal to 239.70 mg/g.

CoFe-based layered double hydroxide for high removal capacity of hydrogen sulfide under high humid gas stream

Although the adsorption method was considered as the most realistic way in the removal of gaseous hydrogen sulfide (H2S), finding an efficient sorbent at low temperature with the high humid condition is still desired. A layered double hydroxide (LDH) of CoFe bimetal was prepared by co-precipitation of bivalent cobalt and trivalent iron and applied to H2S gas stream treatment. CoFe-LDH was optimally synthesized under 3:1 of Co/Fe molar ratio, pH 10 of a mixing solution of precipitating reagents, and 60 °C of aging temperature, which allowed high breakthrough capacity (0.209 g H2S/g) in H2S removal. XPS and spectral analyses on spent CoFe-LDH proved that the H2S removal proceeded through two reaction processes: formed intermediate HS− from dissociated H2S which finally replaced with the hydroxide on the metal surface; and formed HS− through carbonate counter ion at interlayer. This resulted in the formation of CO2 as a gaseous product with CoFeS2 and CoFeSO4 as solid products after the treatment of H2S. Environmental application evidenced the prepared CoFe-LDH more efficient in high humid (90% relative humidity (RH) at room temperature) condition and even at high concentrated H2S source (3333 ppm).

H2S Scavenging Capacity and Rheological Properties of Water-Based Drilling Muds.

Drilling hydrocarbon formations where hydrogen sulfide (H2S) is present could lead to the carryover of H2S with the drilling mud (i.e., drilling fluid) to the surface, exposing working personnel to this lethal gas. Additionally, H2S is very corrosive, causing severe corrosion of metal parts of the drilling equipment, which in turn results in serious operational problems. The addition of an effective H2S scavenger(s) in the drilling mud formulations will overcome these health, safety, and operational issues. In this work, zinc oxide (ZnO), which is a common H2S scavenger, has been incorporated into water-based drilling mud. The H2S scavenging performance of this ZnO-containing drilling mud has been assessed. Additionally, drilling mud formulations containing either copper nitrate (Cu(NO3)2·3H2O) or potassium permanganate (KMnO4) have been prepared, and their H2S scavenging performances have been studied and compared to that of the ZnO-containing drilling mud. It has been observed that the scavenging performance (in terms of the H2S amounts scavenged up to the breakthrough time and at the saturation condition) of the ZnO-containing drilling mud is very poor compared to those of the copper nitrate-containing and KMnO4-containing drilling muds. For instance, the amounts of H2S scavenged up to the breakthrough time by ZnO-containing, copper nitrate-containing, and KMnO4-containing drilling muds were 5.5, 15.8, and 125.3 mg/g, respectively. Furthermore, the amounts of H2S scavenged at the saturation condition by these drilling muds were, respectively, 35.1, 146.8, and 307.5 mg/g, demonstrating the superiority of the KMnO4-containing drilling mud. Besides its attractive H2S scavenging performance, the KMnO4-containing drilling mud possessed more favorable rheological properties [i.e., plastic viscosity (PV), yield point (YP), carrying capacity of the drill cuttings, and gelling characteristics] relative to the base and the ZnO-containing and copper nitrate-containing drilling muds. The addition of KMnO4 to the base drilling mud increased its apparent viscosity, PV, and YP by 20, 33, and 10%, respectively. Additionally, all tested drilling muds possessed acceptable fluid loss characteristics. To the best of our knowledge, there are so far no published studies concurrently tackling the H2S scavenging (i.e., breakthrough time, breakthrough capacity, saturation time, saturation capacity, and scavenger utilization) and the rheological properties of water-based drilling muds, as demonstrated in the current study, highlighting the novelty of this work.

Highly selective removal of 2,4-dinitrotoluene for industrial wastewater treatment through hyper-cross-linked resins

Here a strategy by designing a series of hyper-cross-linked polystyrene resins (HCLRs) with highly selective adsorption ability toward hazardous 2,4-dinitrotoluene from nitrophenol sodium salt-rich real industrial wastewater was reported. Macroporous cross-linked chloromethylated polystyrene was self-crosslinked or crosslinked with ligands, i.e. toluene, aniline, and phenol to produce 2,4-dinitrotoluene affinitic HCLR-0, HCLR-T, HCLR-A and HCLR-P, respectively. The ultrahigh affinity through the like dissolves like mechanism toward 2,4-dinitrotoluene was validated by adsorption experiments, i.e. isotherm, kinetics, thermodynamics, effect of pH & 2-nitrophenol sodium salt and dynamic column adsorption-desorption investigations. They showed ultrahigh adsorption capacities toward 2,4-dinitrotoluene, reaching 628.9, 621.1, 657.9 and 641.0 mg/g for HCLR-0, HCLR-T, HCLR-A and HCLR-P at 303 K, outperforming their matrix cross-linked chloromethylated polystyrene of 79.2 mg/g and XAD-4 of 286 mg/g very much. This advantage was also reflected in the dynamic adsorption study with promising breakthrough and saturated capacities of 195.8 and 334.4 mg/mL wet HCLR-As, respectively. The HCLRs also featured interesting impurity affectless properties, in which 2-nitrophenol sodium salt showed no influence on the 2,4-dinitrotoluene capture even in high concentration. With the interesting properties shown above, the HCLR-A column worked very well in the large-scale real industrial wastewater, and could also be fully recycling used through simple low-cost treatment.

Kinetic separation of C4 olefins using Y-fum-fcu-MOF with ultra-fine-tuned aperture size

The separation of C4 olefin mixtures into pure components is one of the most challenging processes in chemical industries. Adsorption-based separation, using ultra-microporous materials, is considered as a viable alternative to reduce the operating cost of the currently employed but energy intensive distillation technique. The understanding of structural properties-relationships for C4 olefins separation using solid state materials is still lacking particularly for microporous materials with purely cage-based structures. Herein, the adsorptive separation of C4 olefins (butene isomers and 1,3-butadiene) by the microporous MOF, Y-fum-fcu-MOF, containing octahedral and tetrahedral cages with triangular pore aperture size (≈4.7 Å), is studied. The adsorption capacities of the MOF for C4 olefins were assessed by measuring the single component adsorption isotherms at 30 °C which led to very similar equilibrium adsorption uptakes at saturation for the components (excluding isobutylene). However, adsorption breakthrough curves collected at 25 °C and Pulse Gas Chromatography experiments, conducted to define the guest–host affinity at very low concentration (Henry’s region), evidenced kinetically driven separation of C4 olefins by Y-fum-fcu-MOF. In fact, a strong relation between pores window size, kinetic diameter of the components and their adsorption behavior was observed. The breakthrough capacity decreases at increasing molecular size, allowing the separation of cis- and trans-2-butene despite the quite similar adsorption enthalpies for these components (42.0 and 37.7 kJ/mol, respectively).

Ba–Al-decorated iron ore as bifunctional oxygen carrier and HCl sorbent for chemical looping combustion of syngas

Abstract The simultaneous high-temperature HCl removal and chemical looping combustion (CLC) of syngas over barium-decorated oxygen carriers (OCs) was investigated. An iron ore was coated with a layer of sorbent (5 wt%) containing Ba and Al compounds (molar ratios Al:Ba = 0.5, 2.0, 4.5, 8.0, 12) and used for model syngas combustion at 800 °C. It was found that the synthesized materials can effectively remove HCl from the syngas. The HCl removal capacity increased with the Ba loading, and the HCl breakthrough capacity can reach 0.0345 mmol/g for the OC with Al:Ba = 0.5, resulting in the formation of BaCl2. The conversion of Ba species into BaCl2 was 17.3%. Besides the HCl sorption, the coating with Ba and Al compounds enhanced the activity of lattice oxygen and improved the reducibility of OCs during CLC due to the Ba–Fe composite formed on the OCs surface. Compared to the iron ore, the combustion efficiencies of the coated OC with Al:Ba = 4.5 for CO and H2 increased from 62.2% and 87.2% to 99.6% and 95.9%, respectively. Through fluidized bed experiments and thermodynamic calculations, the feasibility of sorbent regeneration was demonstrated by treating OCs with a mixture of CO2 and H2O at 800–1000 °C. The HCl desorption rate increased with temperature and nearly complete sorbent regeneration (99.6%) could be achieved at 1000 °C. These findings demonstrate that Ba–Al-decorated iron ore can be used as bifunctional material in CLC process since it enables simultaneous high-temperature HCl removal and syngas combustion.

Hydrogen sulfide removal from biogas using ion-exchanged nanostructured NaA zeolite for fueling solid oxide fuel cells

Hydrogen sulfide is the most abundant sulfur compound in the biogas, and in order to use for fueling the solid oxide fuel cells, its content should be less than 1 ppm. In this work, NaA nano zeolite is synthesized hydrothermally and modified by Ag+ ions, and its breakthrough capacity for hydrogen sulfide adsorption was measured using dynamic lab-scale adsorption tests on the experimental set-up for the first time. The results are compared to those of unmodified NaA nano zeolite and micron-sized commercial 4A zeolite. AgNaA nano zeolite showed the highest adsorption capacity (33.24 mg H2S/g of Sorbent) and the longest breakthrough time (310 min). The regeneration performance of AgNaA nano zeolite and its structural stability are also investigated after five cycles. The results revealed that the AgNaA nano zeolite could be used promisingly for removing hydrogen sulfide from biogas for cleaner energy production.

High throughput screening setup of a scale-down device for membrane chromatography-aggregate removal of monoclonal antibodies.

In biopharmaceutical process development, resin-based high throughput screening (HTS) is well known for overcoming experimental limitations by permitting automated parallel processing at miniaturized scale, which results in fast data generation and reduced feed consumption. For membrane adsorber (MA), HTS solutions have so far only been available to a partial extent. Three case studies were performed with the aim of aligning HTS applications for MAs with those established for column chromatography: Process parameter range determination, mechanistic modeling (MM), and scalability. In order to exploit the MA typically features, such as high mass transfer and easy scalability, for scalable high throughput process development, a scale-down device (SDD) for MA was developed. Its applicability is confirmed for a monoclonal antibody aggregate removal step. The first case study explores the experimental application of the SDD developed. It uses bind and elute mode and variations of pH and salt concentration to obtain process operation windows for ion-exchange MAs Sartobind® S and Q. In the second case study, we successfully developed a mechanistic model based on parameters obtained from the SDD-HTS setup. The results proved to validate the use of the SDD developed for parameter estimation and thus model-based process development. The third case study shows the transferability and scalability of data from the SDD-HTS setup using both a direct scale factor and MM. Both approaches show good applicability with a deviation below 20% in the prediction of 10% dynamic breakthrough capacity and reliable scale-up from 0.42 to 800 ml.

Versatile Platform of Ion Conducting 2D Anionic Germanate Covalent Organic Frameworks with Potential for Capturing Toxic Acidic Gases

Anionic covalent organic framework is an emerging class of functional materials in which included ionic species of the opposite charges play an important role in the ion conduction and selective gas adsorption. Herein, we reported a facile method to construct a series of germanate-based anionic COFs (Ge-COFs) by reticulating dianionic hexa-coordinated GeO6 nodes with anthracene building blocks adopting a hcb topology in an extended 2D framework. A systematic change of pore properties in Ge-COFs was observed through the incorporation of three different alkali metal cations: Li+, Na+, and K+. The intrinsically negatively charged backbone provides a host matrix with a homogeneous distribution of counter cations and poses variable and exciting features for gas adsorption and ionic conduction. Among the series, K+-based Ge-COF-K with a surface area of 1252 m2/g and pore volume of 0.84 cm3/g shows a maximum CO2 uptake of 126 cm3/g (247.4 mg/g) at 273 K and 1 bar, an IAST selectivity of 140 over N2. Ge-COF-K also exhibits a high SO2 kinetic breakthrough capacity of 154 mg/g at low ppm of SO2 concentration under ambient conditions among recently reported porous materials. Moreover, reasonably high lithium, sodium, and potassium ionic conductivities were observed with the values of 1.2 × 10-4, 3.4 × 10-5, and 2.2 × 10-5 S/cm for propylene carbonate infiltrated Ge-COF-Li, Ge-COF-Na, and Ge-COF-K at 100 °C, respectively.

Comparison of MIL-101(Cr) metal-organic framework and 13X zeolite monoliths for CO2 capture

Abstract A comparative study was conducted to determine the pore properties and adsorptive performance of monoliths containing either the MIL-101(Cr) metal-organic framework or 13X zeolite for carbon dioxide (CO2) capture. Although there have been a great deal of previous work on CO2 adsorption onto zeolites and MOFs, there has been far fewer studies on structured adsorbents such as monoliths. The results indicate that MIL-101(Cr) monoliths have 1.3 times higher porosity than 13X zeolite monoliths. Increasing CO2 partial pressure in the gas mixture shortens breakthrough and equilibrium times and increases the breakthrough and equilibrium adsorption capacities of CO2. MIL-101(Cr) monoliths show better mass transfer of CO2 in the adsorbent bed with shorter breakthrough and equilibrium times of about 20% and 35%, respectively, than 13X zeolite monoliths. The adsorption capacity of CO2 on MIL-101(Cr) monoliths is higher by about 37% (based on weight in mmol/g) at breakthrough and slightly lower by about 7% at equilibrium when compared to 13X zeolite monoliths. MIL-101(Cr) monoliths were found to be 1.5 times more efficient for CO2 adsorption than 13X zeolite monoliths. The effects of regeneration temperature after CO2 adsorption on MIL-101(Cr) and 13X zeolite monoliths were studied and results showed an increase in CO2 adsorption capacity as the regeneration temperature was increased. In summary, the study showed MIL-101(Cr) monoliths have better CO2 adsorption properties than 13X zeolite monoliths.

On the impact of copper local environment on hydrogen sulfide adsorption within microporous AlPO4-5

This work aims at elucidating the most active modes of copper incorporation towards H2S adsorption. Various synthesis methodologies were followed, notably, incorporation via isomorphic substitution, liquid ion exchange (LIE), vapor phase ion exchange (VIE), and nanoparticles inclusion during hydrothermal synthesis, for the introduction of copper into AlPO4-5 and SAPO-5. Techniques such as XRD and SEM/EDX, TEM, FT-IR and N2 adsorption-desorption were employed to characterize the synthesized materials. The Cu- containing materials were examined as sorbents for H2S removal via breakthrough experiments at 150 °C. The highest sulfur removal capacity was attained over the CuO nanoparticles supported in AlPO4-5 (10 % CuO/AlPO4-5), followed by a copper-based material prepared by VIE (Cu-VIE-0.2), accounting for H2S breakthrough capacities of 0.31 and 0.17 mmol ∙ g−1, respectively. The superior performance of these two materials could be ascribed to the relatively higher copper loading in the form of CuO as confirmed by XRD. Comparing the capacity per gram of active site, it was revealed that positioning Cu ions in extra-framework sites leads to an order of magnitude enhancement. This can be attributed to the possibility of a Cu ion to interact with more than one H2S molecule simultaneously unlike the other incorporation modes examined. Furthermore, copper ions incorporated into the crystal framework were found to be inactive towards H2S adsorption.

Electrospun PU nanofiber composites based on carbon nanotubes decorated with nickel-zinc ferrite particles as an adsorbent for removal of hydrogen sulfide from air.

This study focuses on the synthesis of carbon nanotubes decorated with nickel-zinc ferrites and fabrication of polyurethane (PU) nanofiber containing CNT-ferrite composites as highly efficient adsorbents for removal of hydrogen sulfide. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FTIR) spectroscopy, and powder X-ray diffraction (PXRD) are used to perform microstructural and morphological characterization of the electrospun nanofibrous composites. To show the efficiency of the composite as an adsorbent, a breakthrough test is carried out. It is shown that the PU-CNT-ferrite composites are fabricated almost uniformly with an average fiber diameter of 320nm and exhibit significant H2S breakthrough capacity (498mgH2S/g) compared to both the pristine PU and PU-CNT nanofibers. These electrospun nanofibers based on CNT-ferrite composites, already studied for H2S adsorption with promising results, open up new and interesting perspective into the design and fabrication of highly efficient membrane for practical application in the processes of air purification.

Chemically treated Lawsonia inermis seeds powder (CTLISP): An eco-friendly adsorbent for the removal of brilliant green dye from aqueous solution

The present paper deals with the preparation of a novel low-cost and eco-friendly chemically treated lawsonia inermis seed powder (CTLISP) as adsorbent and was further explored for the removal of brilliant green (BG) dye (93%) from aqueous solution. The adsorbent was characterized by various techniques such as FTIR, EDX, SEM and TEM. Effects of various parameters such as concentration, pH, doses, contact time was carried out. The maximum adsorption capacity 34.96 mgg−1 was found to be at 50 °C. The equilibrium was attained in 180 mints and the experimental data were elucidated for isotherms and kinetic studies. The results exhibited that the data is best fitted for the Langmuir isotherm with maximum (R2) value of 0.990 and pseudo-second order kinetics with maximum (R2) value of 0.998. The thermodynamic parameters such as ΔH0, ΔG0 and ΔS0 were also evaluated and the results showed the process to be endothermic, spontaneous in nature. The desorption study showed that 84% of the adsorbed BG could be desorbed by using 1 M oxalic acid as eluting agent. The breakthrough and exhaustive capacities were found to be 12.5 and 45.0 mg g−1, respectively. In order to make the process more economical and feasible the regeneration studies were also carried out and the adsorbent can be reused up to fifth cycle successfully. Therefore, the present low-cost adsorbent (CTLISP) has excellent regenerative capability and gives high monolayer adsorption capacity as compared to others various adsorbent reported in literature. Moreover, the material has been proved to be a promising adsorbent for treatment of BG dye from aqueous solution.

Preparation and characterization of novel bi-functionalized xerogel for removal of methylene blue and lead ions from aqueous solution in batch and fixed-bed modes: RSM optimization, kinetic and equilibrium studies

A new bi-functionalized xerogel is fabricated and then was identified by 29Si CP MAS NMR, SEM, FTIR, and nitrogen adsorption–desorption approaches. As-prepared xerogel efficiency for simultaneous uptake of methylene blue (MB) and Pb2+ ions from aqueous solution is investigated. Individual and combination effects of operating variables (xerogel mass, contact time and initial MB and Pb2+ ion concentration) on the retention performance is achieved with central composite design (CCD) and upgraded through response surface method (RSM). Batch equilibrium outcomes uncovered that MB and Pb2+ ions adsorption onto hybrid composite could be all around depicted by Langmuir isotherm model contrasted with Freundlich equation. Howbeit, the column trials reported that the breakthrough capacities of MB and Pb(II) are observed to be 512 mg.g−1 and 400 mg.g−1 respectively. XPS and FTIR investigations uncovered that the main mechanism of lead uptake ought to be credited to the chelation with –NH2 and ion exchange with –SH groups in the xerogel frameworks. While the MB adsorption system is proposed to be electrostatic attractions, π-π stacking interactions and hydrogen bonds. The work undertaken in this research highlights the major role of the as-synthesized xerogel for treatment of industrial wastewater.

Efficiency of bentonite in removing cesium, strontium, cobalt and uranium ions from aqueous solution: encapsulation with alginate for column application

ABSTRACT Raw bentonite was characterised and employed for adsorption of Cs(I), Sr(II), Co(II) and U(VI) from aqueous solution. Batch adsorption methodology was applied to study the factors influencing the adsorption capacity of bentonite. Thermodynamic parameters, ΔH°, ΔS°, and ΔG° were calculated and revealed that the sorption process is spontaneous and has endothermic nature. The isotherm studies revealed that Langmuir is more applicable than Freundlich isotherm. The maximum sorption capacity (Q0) for the studied sorbent towards Cs (I), U(VI), Co(II) and Sr (II) was 50, 33.3, 25 and 14.29 mg/g, respectively. To overcome the aggregation for clay flacks of bentonite in column,- an innovative microcapsule of alginate enclosing with bentonite was developed and characterised for removal of these ions from multi-component solution. The results revealed that bentonite and bentonite-alginate demonstrated high adsorption capacity at the same pH 5.5. The breakthrough curve had S-shaped profile. The breakthrough capacity of Cs(I), U(VI), Sr(II) and Co(II) was found to be 11.75, 11.1, 8.73 and 11 mg/g, respectively. The total capacity and the total removal percent, (R total%), were established to be 42.58 mg/g and 58.4%, respectively. The results showed that there are some great separation done by elution using 4 M NaNO3 and 4 M HNO3.

Low-Temperature Highly Efficient and Selective Removal of H2S over Three-Dimensional Zn-Cu-Based Materials in an Anaerobic Environment.

In this study, novel three-dimensional ribbon-like composite materials have been introduced for selectively capturing H2S in a low-temperature dry anaerobic environment. First, a ribbon-like basic copper carbonate precursor with Zn doping supported on the activated semicoke (ASC) was successfully synthesized in situ by a two-step hydrothermal method for the first time. The porous Zn-Cu materials obtained after calcination were applied as a sorbent to remove H2S under anaerobic conditions at a low temperature. Effects of the heat treatment temperature, Cu loading content, and Zn doping content on the anaerobic desulfurization performance of Zn-doped CuOx/ASC sorbents were investigated. The optimal Zn-doped CuOx/ASC sorbent showed a satisfactory activity and selectivity to capture H2S efficiently with a breakthrough capacity of 126 mg/g. Further mechanism study demonstrates that the super desulfurization performance of this sorbent is mainly attributed to abundant pore distribution, the synergistic effect between copper and zinc, the extensive surface active oxygen, and so forth.

Adsorption and desorption behaviors of antibiotic ciprofloxacin on functionalized spherical MCM-41 for water treatment

Extensively used antibiotic ciprofloxacin increases in water environment, which is not efficiently removed by means of conventional adsorbents. MCM-41 has great potential for ciprofloxacin removal. There has been little research on ciprofloxacin removal by MCM-41 and their corresponding adsorption/desorption behaviors. In this study, amorphous SiO2, MCM-41 and diamine-functionalized MCM-41 were used as adsorbents to remove ciprofloxacin. In the adsorption process, their adsorption capacity followed the order of SiO2≪MCM-41< diamine-functionalized MCM-41. Ciprofloxacin adsorption behaviors were revealed through the analysis of adsorption isotherms and kinetics model: i. Adsorption process for MCM-41/diamine-functionalized MCM-41 mainly included three steps; and ii. Diamine-functionalized MCM-41 had higher adsorption capacity because of its more and stronger chemical-monolayer adsorption. In the desorption process, strong acid facilitated desorption by inhibiting the interaction between ciprofloxacin and diamine-functionalized MCM-41, and the mechanism was proposed and then supported by salt elution experiment. Last, the breakthrough bed volume and capacity of these absorbents were tested in column operation. Diamine-functionalized MCM-41 had better performance with 550 bed volume and 18.3 mg/g adsorption capacity in the treatment of 5.0 mg/L ciprofloxacin. Both batch and column results demonstrated that diamine-functionalized MCM-41 was highly efficient for ciprofloxacin removal. This study indicates great application prospect of mesoporous silica materials for ciprofloxacin removal and reveals their adsorption/desorption behaviors, which could provide guidance on adsorbent modification/regeneration for antibiotics removal.

ZnFe2O4/activated carbon as a regenerable adsorbent for catalytic removal of H2S from air at room temperature

A series of ZnFe2O4/activated carbon adsorbents with various ZnFe2O4 loadings was synthesized and used for removing H2S from moist air at a room temperature. The materials were characterized using adsorption of nitrogen, SEM-EDS, ICP-OES, XPS, XRD, FT-IR, TGA, Raman spectroscopy and potentiometric titration. The experimental results showed that the adsorbent with 10 wt% ZnFe2O4 had the highest H2S breakthrough capacity of 122.5 mg/g, ~ twice larger than the capacity calculated assuming the stoichiometric chemical reactivity of the inorganic phase. Moreover, the capacity remained more or less constant after three thermal regeneration cycles. The characterization results indicated that the desulfurization process involved reactive adsorption and catalytic oxidation of H2S. Besides the chemical nature of the active phase, the H2S removal performance was found to be dependent on the textural properties (surface area and pore volume) and surface pH. FeOOH formed as an intermediate during the desulfurization process played also a catalytic role.

Comparative study of nanofiltration and ion exchange for nitrate reduction in the presence of chloride and iron in groundwater

Public concern on the groundwater contamination by nitrate has grown significantly in recent years.The objective of this study was to determine the appropriate treatment to reduce the nitrate content in the presence of other ions from groundwater, for which nanofiltration and ion exchange were evaluated. In nanofiltration, the effects of pressure, feed flow, initial composition, and performance were studied, in ion exchange the flow rate, initial composition, and resin regeneration process.Nanofiltration tests were carried out on four different commercial membranes: NF97, NF99, NF99H, and NF90. Among these, all membranes removed chloride but only NF97 and NF90 were able to remove nitrate in compliance with Chilean drinking water standard, showing rejections of 97% and 87%, respectively, in an optimum pressure range of 12–20 bar in which the NF90 produced 3.5 times more permeated water than NF97.For ion exchange tests, Purolite A520E resin was used, which decreased nitrate content to <1 mg/L. Results leading to the optimal flow within the exchange column indicated that residence time must be at least 2.1 min. The higher nitrate concentration in water did not lead to changes in the maximum resin capacity, 47.1 mg NO3−/g resin, but it did decrease the resin breakthrough capacity when initial concentration increased. Optimal regeneration was assigned to a 3% w/V NaCl solution and up-flow mode.Due to the ability to remove both nitrate and chloride, and being able to remove iron if necessary, nanofiltration was chosen as the appropriate treatment.