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The tanning industry is among the most environmentally harmful activities globally due to the pollution of lakes and rivers from its effluents. Hexavalent chromium, a metal in tannery effluents, has adverse effects on human health and ecosystems, requiring the development of removal techniques. This study assessed the efficacy of organobentonite/alginate hydrogel beads in removing Cr(VI) from a fixed-bed adsorption column system. The synthesized organobentonite (OBent) was encapsulated in alginate, utilizing calcium chloride as a crosslinking agent to generate hydrogel beads. The effects of the volumetric flow rate, bed height, and initial Cr(VI) concentration on a synthetic sample were analyzed in the experiments in fixed-bed columns. The fractal-like modified Thomas model showed a good fit to the experimental data for the asymmetric breakthrough curves, confirmed by the high R2 correlation coefficients and low χ2 values. The application of organoclay/alginate hydrogel beads was confirmed with a wastewater sample from an artisanal tannery industry in Belén (Nariño, Colombia), in which a Cr(VI) removal greater than 99.81% was achieved. Organobentonite/alginate hydrogels offer the additional advantage of being composed of a biodegradable polymer (sodium alginate) and a natural material (bentonite-type clay), resulting in promising adsorbents for the removal of Cr(VI) from aqueous solutions in both synthetic and real water samples. [ABSTRACT FROM AUTHOR]

Treatment of dye polluted water using sustainable and efficient approaches is essential to mitigate the detrimental effects of dyes. The present work reports on the adsorption effectiveness of a graphene-based adsorbent configured into a practical engineering structure, namely three-dimensional graphene oxide integrated with chitosan biopolymer (3D-GCB). This unique graphene configuration enabled its application in continuous fixed-bed adsorption of Metanil Yellow (MY) and Remazol Black B (RBB) dyes from polluted water for the first time. The breakthrough attributes of the fixed-bed of 3D-GCB were established in terms of bed depth (3 – 5 cm), influent concentration (100 – 200 mg/L for MY and 100 – 300 mg/L for RBB) and feed flowrate (2 – 4 mL/min). The greatest bed adsorption capacities attained were 157.06 and 247.96 mg/g for MY and RBB, respectively. The column parameters for obtaining these results were 5 cm bed depth, 2 mL/min feed flowrate, and 150 and 200 mg/L influent concentrations respectively for MY and RBB. The fixed-bed performance of the 3D-GCB was well correlated to the Thomas and Yoon-Nelson models, and the corresponding kinetic properties were determined. Furthermore, the higher affinity of the 3D-GCB for RBB as compared to MY was elucidated based on the ionic strengths of the dye molecule. The utilisation of sustainable and renewable raw materials, such as graphite and chitosan, have resulted in a 3D-GCB production cost of approximately RM 10.72 per gram. This work revealed the suitability of 3D-GCB as the state-of-the-art graphene composite for continuous adsorption of anionic dyes, specifically MY and RBB.

The tanning industry is among the most environmentally harmful activities globally due to the pollution of lakes and rivers from its effluents. Hexavalent chromium, a metal in tannery effluents, has adverse effects on human health and ecosystems, requiring the development of removal techniques. This study assessed the efficacy of organobentonite/alginate hydrogel beads in removing Cr(VI) from a fixed-bed adsorption column system. The synthesized organobentonite (OBent) was encapsulated in alginate, utilizing calcium chloride as a crosslinking agent to generate hydrogel beads. The effects of the volumetric flow rate, bed height, and initial Cr(VI) concentration on a synthetic sample were analyzed in the experiments in fixed-bed columns. The fractal-like modified Thomas model showed a good fit to the experimental data for the asymmetric breakthrough curves, confirmed by the high R2 correlation coefficients and low χ2 values. The application of organoclay/alginate hydrogel beads was confirmed with a wastewater sample from an artisanal tannery industry in Belén (Nariño, Colombia), in which a Cr(VI) removal greater than 99.81% was achieved. Organobentonite/alginate hydrogels offer the additional advantage of being composed of a biodegradable polymer (sodium alginate) and a natural material (bentonite-type clay), resulting in promising adsorbents for the removal of Cr(VI) from aqueous solutions in both synthetic and real water samples.

Microporous and mesoporous activated carbon produced from longan-seed biomass were impregnated with NaOH and used to capture CO2 from a simulated flue gas in a fixed-bed column. The process variables that were studied included types of activated carbon as characterized by the volume ratio of micropores and mesopores (Vmic/Vmes), adsorption temperature, NaOH loading, gas feed rate and the adsorbent amount. All five process variables affected the two important breakthrough parameters, namely the breakthrough time (tB) and CO2 adsorption capacity at breakthrough time (qB), with different trends and degrees. However, it was only the NaOH loading that showed a characteristic of an optimum loading that provided the maximum of the breakthrough parameters. It was found that an approximate 45% increase in the adsorbed amount of CO2 could be achieved with the activated carbon impregnated with around 1 weight % NaOH solution as compared to the case of the non-impregnated carbon. The response surface methodology (RSM) was applied to develop the correlations for both tB and qB and the maximum predicted qB of 33.58 mg/g was derived at the NaOH loading of 76.5 mg/g carbon, Vmic/Vmes of 2.83, adsorption temperature of 20°C, gas feed rate of 156 kg/m2-h and adsorbent amount of 51 kg/m2 of column cross-section area. The Klinkenberg's breakthrough model was able to describe the CO2 breakthrough curves reasonably well for all the tested conditions. The analysis of the two model parameters, the affinity constant (K) and the effective pore diffusivity (De), revealed that the optimum Vmic/Vmes that provided the maximum K value was around 2.90, corresponding to the activated carbon that contains 74% and 26% by volume of micropores and mesopores, respectively. The proper volume ratio of micropores and mesopores along with alkali addition into activated carbon can be effectively used for maximizing CO2 adsorption in a fixed-bed adsorption system. [ABSTRACT FROM AUTHOR]

Featured Application: This study aimed to synthesize a novel biomass-based, chemically activated carbon from Pinus radiata sawdust and to investigate its effectiveness in the removal of wood dyes from aqueous solutions in a fixed-bed column. In this paper, an activated carbon obtained from Pinus radiata sawdust is applied to remove blue, red, and black wood dyes from aqueous solutions in a fixed-bed column. The flow rate (7.7–30.8 mL min−1), initial dye concentration (25–500 mg L−1), and bed height (2–4 cm) highly influence the breakthrough-curves' features. The results indicate that the adsorption capacity increased by decreasing the flow rate and increasing the initial dye concentration, except for the black dye, and increasing bed height, except for the red dye. In addition, the breakthrough time changed by modifying the studied variables. The curves became steeper as the flow rate increased and as the bed height decreased. Also, by increasing the inlet dye concentration, the breakthrough time decreased significantly, and sharper breakthrough curves were obtained. The activated carbon with a surface area of 2826 m2 g−1 led to high values of the adsorption capacity between 150 and 1300 mg g−1. The Yoon–Nelson and Thomas models were the ones that best described the adsorption data. The activated carbon saturated with black dye could be used in three successive cycles after regeneration with H2O2. [ABSTRACT FROM AUTHOR]

MCM-41, a mesoporous silica with a high surface area and hexagonal structure, was synthesized, and commercial nano-silicon dioxide (SiO2) was used as a solid adsorbed in post-combustion CO2 capture. The CO2 adsorption experiments were conducted in a fixed-bed adsorption system using 5–15 vol.% CO2/N2 at a flow rate of 100 mL/min at varying temperatures (20–80 °C) and atmospheric pressure. Analyses (X-ray diffraction, nitrogen adsorption-desorption isotherms, Fourier-transform infrared spectroscopy, and transmission electron microscopy (TEM)) revealed that the synthesized MCM-41 has mesoporous characteristics: a high surface area and large pore volumes. The CO2 adsorption capacity of MCM-41 and commercial nano-SiO2 increased considerably with increasing CO2 concentration and temperature, peaking at 60 °C. Below 60 °C, dynamics rather than thermodynamics governed the adsorption. Increasing the temperature from 60 to 80 °C decreased the adsorption capacity, and the reaction became thermodynamically dominant. Additionally, compared with commercial nano-SiO2, the MCM-41 sorbent demonstrated superior regenerability and thermal stability. [ABSTRACT FROM AUTHOR]

This research evaluates the use of organoclay/alginate hydrogels in removing Acid Yellow 23 in a fixed-bed column and contributes to the application of these composites in the context of the adsorption of anionic dyes that are present in wastewater. An organobentonite (OBent) was synthesized and encapsulated in an alginate matrix, using Ca2+ ions as a crosslinking agent. Experiments in fixed-bed columns showed that breakthrough and exhaustion times were longer with increasing bed height, which decreased with increases in flow rate and initial dye concentration. The Thomas, Yoon–Nelson, and Adams–Bohart models were well fitted to the experimental data for the breakthrough curves with high Adj. R2 correlation coefficients and low values of χ2. The theoretical adsorption capacity of the organobentonite/alginate hydrogel calculated from the Thomas model was 0.50 ± 0.01 mg/g (equivalent to 30.97 mg/g OBent), and this was obtained by using a 15 cm (10.10 g) bed height, 1 mL/min flow rate, and a 45 mg/L input dye concentration. The bed was regenerated with a 0.5 M NaOH solution, and the reuse of the saturated column bed was studied for two adsorption–desorption cycles. The results obtained in this study suggest the potential use of an organoclay/alginate hydrogel for the adsorption of pollutants in continuous systems. [ABSTRACT FROM AUTHOR]

• PMBC was prepared from phosphogypsum and biomass for antibiotics removal. • PMBC produced from 70 wt% phosphogypsum and wood chips showed the best performance. • Acidic conditions facilitated the adsorption of SD and SMT by PMBC. • PMBC showed good removal efficiency for SD and SMT in a fixed bed column. • Hydrogen bonding, π-π, hydrophobic, and electrostatic interaction contributed to adsorption. Antibiotic pollution has become a global eco-environmental issue. To reduce sulfonamide antibiotics in water and improve resource utilization of solid wastes, phosphogypsum modified biochar composite (PMBC) was prepared via facile one-step from distillers grains, wood chips, and phosphogypsum. The physicochemical properties of PMBC were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), Zeta potential, X-ray diffraction (XRD), etc. The influencing factors, adsorption behaviors, and mechanisms of sulfadiazine (SD) and sulfamethazine (SMT) onto PMBC were studied by batch and fixed bed column adsorption experiments. The results showed that the removal rates of SD and SMT increased with the increase of phosphogypsum proportion, while decreased with the increase of solution pH. The maximum adsorption capacities of modified distillers grain and wood chips biochars for SD were 2.98 and 4.18 mg/g, and for SMT were 4.40 and 8.91 mg/g, respectively, which was 9.0–22.3 times that of pristine biochar. Fixed bed column results demonstrated that PMBC had good adsorption capacities for SD and SMT. When the solution flow rate was 2.0 mL/min and the dosage of PMBC was 5.0 g, the removal rates of SD and SMT by modified wood chips biochar were both higher than 50% in 4 hr. The main mechanisms of SD and SMT removal by PMBC are hydrogen bonding, π-π donor-acceptor, electrostatic interaction, and hydrophobic interaction. This study provides an effective method for the removal of antibiotics in water and the resource utilization of phosphogypsum. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, an activated carbon obtained from Pinus radiata sawdust is applied to remove blue, red, and black wood dyes from aqueous solutions in a fixed-bed column. The flow rate (7.7–30.8 mL min−1), initial dye concentration (25–500 mg L−1), and bed height (2–4 cm) highly influence the breakthrough-curves’ features. The results indicate that the adsorption capacity increased by decreasing the flow rate and increasing the initial dye concentration, except for the black dye, and increasing bed height, except for the red dye. In addition, the breakthrough time changed by modifying the studied variables. The curves became steeper as the flow rate increased and as the bed height decreased. Also, by increasing the inlet dye concentration, the breakthrough time decreased significantly, and sharper breakthrough curves were obtained. The activated carbon with a surface area of 2826 m2 g−1 led to high values of the adsorption capacity between 150 and 1300 mg g−1. The Yoon–Nelson and Thomas models were the ones that best described the adsorption data. The activated carbon saturated with black dye could be used in three successive cycles after regeneration with H2O2.

In this work, the optimization of temperature, argon gas flow rate, acetylene gas flow rate and time effect on the yield of as-synthesized multi-wall carbon nanotubes (AS-MWCNTs) using a novel iron-nickel/biochar catalyst was investigated. Subsequently, the AS-MWCNTs were functionalized to obtain oxidized multi-wall carbon nanotubes (OX-MWCNTs). The nanoadsorbents were applied for Cu(II) and Zn(II) ions adsorption from wastewater in a batch and fixed-bed process. Remarkably, the results revealed optimum AS-MWCNTs yield (280%) at the following experimental conditions; temperature (725 °C), argon gas flow rate (250 mL/min), acetylene gas flow rate (180 mL/min) and time (75 min). OX-MWCNTs demonstrated higher surface area of 1210 m 2/g compared to AS-MWCNTs (1140 m 2/g). The optimum removal of Cu(II) and Zn(II) ions were obtained at pH (6), contact time (30 min), adsorbent dosage (20 mg/L), initial metal concentration (Cu(II) (75 mg/L) and Zn(II) (80 mg/L)) and temperature (45 oC). Maximum adsorption capacities for Cu(II) and Zn(II) ions removal by AS-MWCNTs were obtained as 364.66 and 347.01 mg/g, while OX-MWCNTs produced higher maximum adsorption capacities of 416.47 and 411.88 mg/g. The experimental data were better fitted by Langmuir isotherm and pseudo-second order kinetics, while thermodynamic investigation revealed a favorable and spontaneous chemisorption controlled adsorption of metal ions. Furthermore, the breakthrough curves of Cu(II) and Zn(II) ions was suitably modelled by Thomas kinetic model. Accordingly, AS-MWCNTs and OX-MWCNTs indicate a promising choice to eliminate Cu(II) and Zn(II) ions in wastewater due to its stability, high efficiency, environmental friendliness and excellent recyclability capacity.

• Enhanced adsorption with bare commercial NaY through ion-exchange. • Improved dynamic adsorption of FAU zeolites with binder-free technology. • CO 2 loading at low pressure: Ca(71)Y < Ca(56)Y < NaY < K(23)Y < K(58)Y < K(95)Y. • Binder-free K(23)Y achieves 3.53 mol/kg CO 2 , selectivity 101 over N 2. • Top performer under post-combustion CO 2 capture conditions: Binder-free K(23)Y. Ion-exchange on bare commercial zeolites can offer improved adsorption processes. In the context of CO 2 /N 2 separation for post-combustion CO 2 capture (PCC), here, we report, the effect of ion-exchange on commercial binder-free NaY zeolite with alkali (K+) and alkaline earth (Ca2+) metal cations, achieving exchange levels of 23 %, 58 %, and 95 % for K+ and 56 % and 71 % for Ca2+. Adsorption isotherms of CO 2 and N 2 were measured over a temperature range of 306–344 K and pressures up to 350 kPa. At low pressures, the CO 2 adsorption capacity increases as Na+ ions are exchanged to a higher level of K+, while a reverse trend is observed for Ca2+ exchange. At 25 kPa and 306 K, the CO 2 loading (mol∙kg−1) follows the order 2.01-Ca(71)Y < 2.63-Ca(56)Y < 4.05-NaY < 4.29-K(23)Y < 4.59-K(58)Y < 4.72-K(95)Y. The selectivities of CO 2 (15 %)/N 2 (85 %) at 306 K and 101.3 kPa range from 52 for Ca(71)Y to 101 for K(23)Y, compared to 89 in the bare NaY zeolite. The working capacities for the most promising exchanged sample (K(23)Y) exhibit superior values of 4.51, 2.98, and 2.41 mol∙kg−1 considering regeneration pressures of 3, 10, and 15 kPa, relative to a feed pressure of 101.3 kPa, respectively. Dynamic simulations were conducted using the Aspen Adsorption package to accurately predict both single- and binary-component breakthrough curves. [ABSTRACT FROM AUTHOR]

Caffeine in water resources has been reported, indicating the need for alternative treatments. Activated carbons (ACs) are efficient adsorbents; however, they present issues that immobilization in chitosan hydrogel (CH) can overcome. Despite the importance of both aspects, adsorption in continuous systems and different aqueous matrices are understudied. The present study developed and characterized chitosan/AC composites to improve the adsorbent properties and fill the research gap presented. The adsorbent was applied to adsorb caffeine in batch and fixed-bed experiments, using distilled and tap water and synthetic hospital wastewater. Chicha-do-cerrado shells were used to develop two different ACs (KAC and CAC) and composite beads (CH-KAC and CH-CAC). KAC and CH-KAC showed high surface area (1082 and 240 m² g−1), and FTIR indicated that CH assigned new functional groups to the composites. Batch studies revealed a maximum adsorption capacity of 391.00, 139.61, 121.90, and 39.53 mg g−1 for KAC, CAC, CH-KAC, and CH-CAC, respectively. The ions effect in tap water did not occur for the composites due to the bridging phenomenon. In treating the synthetic hospital wastewater, the addition of AC increased the removal efficiency. The fixed-bed maximum adsorption capacity was 83.88 mg g−1 for CH-KAC, and the column was reused three times. The importance of both CH and ACs has been successfully proven. • The addition of chitosan to the activated carbon enriched the adsorbent's structure • KOH activated carbon/chitosan composite obtained a high surface area (240 m² g−1). • The adsorption of caffeine in tap water was evaluated. • The ions effect did not occur in tap water due to the bridging phenomenon. • The adsorbents treated a synthetic hospital wastewater. [ABSTRACT FROM AUTHOR]

This paper reports a continuous adsorption study by means of a fixed-bed packed column using zeolite/Fe3O4 nanocomposite for the removal of Ca, K, Mg, Mn, Co, and Zn from synthetic brine solution and seawater samples. The surface, morphological and crystalline properties of the adsorbent were investigated using scanning electron microscopy, x-ray diffraction, and Brunauer Emmett & Teller. These results obtained confirmed that zeolite was successfully modified with magnetic nanoparticles (Fe3O4). The effects of adsorption process parameters were optimized using response surface methodology based on central composite design. The optimum conditions were used to study the breakthrough curve on the fixed-bed adsorption of major and trace metals by zeolite/Fe3O4 nanocomposite. The effects of bed mass, initial concentration, and flow rate were evaluated on synthetic water. The breakthrough time of the zeolite/Fe3O4 on Ca, Co, K, and Mg were achieved at 830, 290, 315, and 105 min, respectively. The volumes (in L) that were treated at a breakthrough point on Ca, Co, K, and Mg were 1.66, 0.58, 0.63, and 0.21 L. Adsorption data were correlated using the Thomas and Yoon–Nelson breakthrough models and the results agreed with experimental values. The zeolite/Fe3O4 nanocomposite material was used on seawater treatment and the material proved to be an efficient adsorbent for treatment of Ca, K, Mg, Al, and Pb with percentage removal ranging from 83 to 99.9%. [ABSTRACT FROM AUTHOR]

Chromium is a toxic metal widely used in several industrial activities, being frequently found in industrial effluents. The presence of chromium in its soluble ionic form Cr(III) is related to health risks, damage to living beings and to the environment. In this work, the capture of Cr(III) using alginate extraction residue (RES) from the Sargassum filipendula algae was evaluated to investigate the adsorption properties of this waste material. The study steps included batch and continuous adsorption assays, characterizations, and desorption evaluation. The adsorbent residue was not submitted to pre-treatment steps. The investigation of chromium adsorption and the fluid dynamic study are presented in this work. The equilibrium and thermodynamic studies indicated that the uptake of Cr(III) by the RES occurred spontaneously, endothermic, and energetically favorable on a heterogeneous surface with energetically distinct sites, mainly by chemisorption. The Freundlich and Dubinin-Radushkevich, and pseudo-second order models showed better fit to the equilibrium and kinetic experimental data, respectively. In the continuous fixed-bed system, the breakthrough curves showed a smaller mass transfer zone under flow rate and Cr(III) inlet concentration conditions of 0.5 mL/min and 1.0 mmol/L, respectively. The low desorption percentages corroborate the chemical nature of the bonds involved in adsorption. The best result of 67.5% was obtained with the combined eluent of HCl and CaCl2, both at 1 mol/L. SEM and EDX analyzes showed that ion exchange is involved in the adsorptive process with a reduction in the amount of light ions (Na, Ca, Mg, and K) on the RES surface. The characterization analyzes indicated that hydroxyls are the main group involved in the adsorption of metal that occurred on the surface of the RES.

The occurrence of acetaminophen in surface water has been reported worldwide, indicating the need of alternative wastewater treatments. Activated hydrochar (AHC) is efficient for pharmaceuticals removal. Powdered AHC presents challenges that hamper its expansion. However, these issues can be overcome by adding polymers, such as alginate, in composite beads. Therefore, the present study aimed to develop and characterize alginate/brewer's spent grain AHC beads, applying them to acetaminophen adsorption in batch and fixed-bed experiments. The adsorbent presented a high surface area (533.42 m2 g–1) and Fourier-transform infrared spectroscopy (FTIR) showed that alginate assigned new functional groups to the composite. Batch studies revealed an endothermic behavior and maximum adsorption capacity of 165.94 mg g−1, with an equilibrium time of 240 min. The fixed-bed maximum adsorption capacity was 127.01 mg g−1, with a mass transfer zone of 5.89 cm. The importance of alginate for the adsorbent development has been successfully proven. [Display omitted] [ABSTRACT FROM AUTHOR]

Background. Lead (Pb(II)) exposure from drinking water consumption is a serious concern due to its negative health effect on human physiology. A commercially available filter uses the adsorption potential of activated carbon for removing heavy metals like Pb(II). However, it has some constraints since it uses only surface area for the adsorption of these contaminants. Biochar produced via slow pyrolysis of biomass shows the presence of oxygen-containing functional groups on its surface that take part in the adsorption process, with higher removal potential compared to activated carbon. Objectives. The current study examined the adsorption kinetics and mechanisms of Pb(II) removing potential of biochar from water using a fixed-bed continuous flow adsorption system. Methods. The effect of initial Pb(II) concentration, mass of adsorbent (bed depth), and flow rate on adsorption potential were evaluated. The Adams-Bohart model, Thomas model, and Yoon-Nelson model were applied to the adsorption data. Results. The maximum removal efficiency of Pb(II) was 88.86 mg/g. The result illustrated that the Yoon-Nelson model is the best fit to analyze the adsorption phenomena of Pb(II) in a fixed-bed biochar column. Conclusions. The breakthrough data obtained from this study can be utilized to design a point of use filter that would be able to effectively remove Pb(II) from drinking water. Competing Interests. The authors declare no competing financial interests.

The present research article explored the potential of activated carbon prepared from Limonia acidissima shell to adsorb total Fe ions from aqueous solution in a packed bed up-flow column. The effect of essential factors such as bed height (3–5 cm), initial concentration (30–50 mg/L), and flow rate (3.32–5.4 mL/min) on the performance of the column bed was investigated. The adsorption capacity augmented with an increase in bed height and initial adsorbate concentration but declined with an increase in flow rate. The maximum uptake capacity of 209.6 mg/g was achieved at 5 cm bed height, 3.32 mL/min, and 50 mg/L initial concentration. The bed depth service time (BDST) model was used to analyze the experimental data and determine the characteristic parameters of the packed bed reactor suitable for designing large-scale column studies. The Adams–Bohart, Thomas, and Yoon–Nelson models were applied to the experimental data to predict breakthrough curves using non-linear regression. The artificial neural network (ANN) based model was able to efficaciously predict the column performance using the Levenberg–Marquardt (LM) algorithm. A comparison between the experimental data and model results contributed to a high degree of correlation, specifying that the preliminary information was in good agreement with the ANN predicted data. [ABSTRACT FROM AUTHOR]

Pyrochar–AgBr (DCG–AgBr) produced from discarded chewing gum for the decontamination of trichlorophenol (2,4,5-TCP) is reported. The DCG–AgBr specific surface area (249.5 m2/g), the pore volume of 0.998 cm3/g, surface functional groups and thermal analysis were established. The 2,4,5-TCP removal efficiency at 10 mg/L was estimated to be ∼96% and the dynamic behavior was successfully described by the Thomas and Yoon–Nelson models. Based on the economic analysis, the total cost for treatment of 2,4,5-TCP simulated wastewater was 14.39 US$/m3. For the first time, commonly discarded chewing gum was employed as a precursor for fabrication of adsorbents for wastewater treatment. [ABSTRACT FROM AUTHOR]

In the present study, the glucose-based carbonaceous adsorbent was prepared from glucose, melamine and urea by using ZnCl 2 activation and heated at 550°C under N 2 flow. The sample was treated for the 1st, 2nd and 3rd activation process, and they were characterized by N 2 adsorption and desorption isotherms, elemental analysis and X-ray photoelectron spectroscopy (XPS). The results showed that the content of nitrogen increased and that of oxygen decreased with the increasing of the number of activation process. The adsorbent obtained after the 2nd activation showed the best adsorption properties and was used in batch and fixed-bed column adsorption studies. In batch adsorption experiments, we investigated the factors affecting nitrate adsorption such as initial concentration, solution pH, adsorption isotherms and adsorption kinetics. The isotherm data and kinetic data were fitted well to the Langmuir isotherm model and pseudo-second-order model, respectively, and the maximum adsorption capacity calculated by Langmuir model was 1.58 mmol/g at pH 3. The adsorption performance of the adsorbent in industrial application mode was also investigated by fixed-bed column experiments. The breakthrough time of the packed column was 160 min for the initial nitrate concentration of 200 mg/L at pH 3. The saturated column could be regenerated by 1 mol/L HCl and reused for at least 5 adsorption-desorption cycles. The column showed good adsorption performance in both coexisting ions solution and real contamination water. [Display omitted] [ABSTRACT FROM AUTHOR]

The presence of emerging water pollutants such as endocrine-disrupting compounds (EDCs), including 17-ethynylestradiol (EE2), bisphenol A (BPA), and perfluorooctanoic acid (PFOA), in contaminated water sources poses significant environmental and health challenges. This study aims to address this issue by investigating the efficiency of novel calcium-based metal-organic frameworks, known as mixed-linker calcium-based metal-organic frameworks (Ca-MIX), in adsorbing these endocrine-disrupting compounds. This study analyzed the influence of influent concentration, bed height, and flow rate on pollutant removal, with bed height emerging as a crucial factor. From the breakthrough curves, it was determined that the column maximum adsorption capacities followed the order of 17-ethynylestradiol (101.52 μg/g; 40%) > bisphenol A (99.07 μg/g; 39%) > perfluorooctanoic acid (81.28 μg/g; 32%). Three models were used to predict the adsorption process, with the Yan model outperforming the other models. This suggests the potential of mixed-linker calcium-based metal-organic frameworks for removing endocrine-disrupting compounds from water, using the Yan model as an effective predictor. Overall, this study provides valuable insights for the development of effective water treatment methods using mixed-linker calcium-based metal-organic frameworks to remove endocrine-disrupting compounds from contaminated water sources. [Display omitted] • Novel calcium-based metal-organic framework (Ca-MIX) were synthesized. • Several endocrine-disrupting compounds (EDCs) removed via column adsorption method. • Effects of various column adsorption conditions on EDCs removal were thoroughly studied. • The mathematical column adsorption models for EDCs adsorption were thoroughly evaluated. [ABSTRACT FROM AUTHOR]

BACKGROUND: Epichlorohydrin/thiourea modified alginate (ETA) microspheres prepared by an emulsion method were used as stationary phase in a fixed‐bed column to selectively adsorb Pd (II) from bi‐metallic solutions. The transport‐dispersive model with a linear driving force kinetics equation and a pH‐dependent competitive Langmuir isotherm was employed to predict the breakthrough curves of the metal ions from the fixed bed. RESULTS: Good agreement between the model predictions and the experimental results under different operating conditions confirms the validity and accuracy of the mathematical model and the derived model parameters. Metal ions elute faster from the column with steeper breakthrough curves at higher flow rates and relatively higher feed concentrations. The pH value significantly affects the competitive adsorption isotherm as well as the breakthrough curves. The fully loaded packed bed can be regenerated completely by dilute thiourea solution. CONCLUSION: The tailor‐made ETA microspheres can be successfully packed in a fixed‐bed column to selectively adsorb Pd (II) from bimetallic solutions. The transport‐dispersive model is capable of predicting the adsorption performances over a wide range of operating conditions. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Fixed-bed adsorption is widely used in industrial gas separation and is the primary method for atmosphere revitalization in space. This paper analyzes the uncertainty of a one-dimensional, fixed-bed adsorption model due to uncertainty in several model inputs, namely, the linear-driving-force (LDF) mass transfer coefficient, axial dispersion, heat transfer coefficients, and adsorbent properties. The input parameter uncertainties are determined from a comprehensive survey of experimental data in the literature. The model is first calibrated against experimental data from intra-bed centerline concentration measurements to find the LDF coefficient. We then use this LDF coefficient to extract axial dispersion coefficients from mixed, downstream concentration measurements for both a small-diameter bed (dominated by wall-channeling) and a large-diameter bed (dominated by pellet-driven dispersion). The predicted effluent concentration and temperature profiles are most strongly affected by uncertainty in LDF coefficient, adsorbent density, and void fraction. The uncertainty analysis further reveals that ignoring the effect of wall-channeling on apparent axial dispersion can cause significant error in the predicted breakthrough times of small-diameter beds. [ABSTRACT FROM AUTHOR]

Graphical abstract A new type of highly recyclable cellulose aerogels with ultrahigh selective and efficient adsorption capacity for anionic dyes has been facilely synthesized for the decontamination in both batch and continuous fixed-bed systems. Abstract A new type of polyethylenimine modified cellulose (PMC) aerogels were synthesized through a chemical cross-linking process, by which plenty of amine groups were introduced to the surface of cellulose aerogels. FT-IR, SEM, EDS, BET and XPS were used to characterize the physicochemical properties of this novel composite. The prepared aerogels were used to remove anionic dyes from effluents and it exhibited excellent adsorption performance in batch and fixed-bed experiments. Adsorption results indicated that PMC could efficiently, selectively separate anionic dyes from dye mixtures and maintain the maximum absorption capacity even after ten regeneration cycles, exhibiting superior selectivity and desirable recyclability. The maximum adsorption capacities of PMC for rose bengal and methyl blue were 1310.21 and 1333.04 mg/g, respectively, which were much higher than those of previously reported results. The Kinetics and isothermal adsorption data were well described by pseudo-second-order kinetic model and Langmuir model. The breakthrough curves obtained from fixed-bed systems were well fitted by Thomas model. Most importantly, anionic dyes could be efficiently removed even with high concentrations of coexisting anions. All these results manifested that PMC could be a promising candidate for sewage treatment, profiting from the fascinating merits of easy separation, low-cost, high adsorption capacity, strong anti-environment disturbance, superior reusability and selectivity. [ABSTRACT FROM AUTHOR]

To guide the practical application of fibrous materials in wastewater treatment, this study explored the engineering design of fixed bed adsorption technique by using carboxyl-modified jute fiber (CMJF) for copper ion (Cu(II)) removal from aqueous solution. The study, conducted by means of adsorption experiments in a column with a fixed bed of sorbent, investigated the effects of the CMJF sorbent dosage, the flow rate and the initial Cu(II) concentration on the corresponding breakthrough curves and compared the dynamic adsorption performance of raw and modified jute in the same process conditions. Compared with the fixed bed of raw jute fiber, the CMJF sorbent exhibited a breakthrough time about 3.2 times longer and a dynamic adsorption capacity roughly 4.2 times higher at the optimal conditions (packing height of 8 cm, flow rate of 17.45 cm/min and initial concentration of 100 mg/L). The dynamic adsorption capacity, 50% breakthrough time and 10% breakthrough time could be well predicted by Thomas, Yoon–Nelson and Bed Depth Service Time (BDST) models, respectively. Besides, these dynamic models well described the fixed bed adsorption behavior, and the CMJF exhibited better fixed bed adsorption performance than raw jute. [ABSTRACT FROM AUTHOR]

In the second part of this series of studies, the monocomponent adsorption of Cu 2+ , Co 2+ and Ni 2+ onto STA adsorbent in a fixed-bed column was investigated and optimized using a 2 2 central composite design. The process variables studied were: initial metal ion concentration and spatial time, and the optimized responses were: adsorption capacity of the bed ( Q max ), efficiency of the adsorption process ( EAP ), and effective use of the bed ( H ). The higher Q max for Cu 2+ , Co 2+ and Ni 2+ were 1.060, 0.800 and 1.029 mmol/g, respectively. The breakthrough curves were modeled by the original Thomas and Bohart-Adams models. The changes in enthalpy (Δ ads H °) of adsorption of the metal ions onto STA were determined by isothermal titration calorimetry (ITC). The values of Δ ads H ° were in the range of 3.0–6.8 kJ/mol, suggesting that the adsorption process involved physisorption. Desorption ( E des ) and re-adsorption ( E re-ads ) of metal ions from the STA adsorbent were also investigated in batch mode, and the optimum conditions were applied for three cycles of adsorption/desorption in a fixed bed column. For these cycles, the lowest values of E des and E re-ads were 95 and 92.3%, respectively, showing that STA is a promising candidate for real applications on a large scale. [ABSTRACT FROM AUTHOR]

The chemical and mineral compositions, particle size, hydrothermal dissolubility of four silica sands with different origins, including two sands from crushed quartz stones, one from a desert and one from a sea bed deposit, and their availability to synthesize nanoporous silica have been carefully analyzed and compared. The results indicate that irrespective of the chemical composition and crystallinity, the four sands show similar dissolution trends in alkaline solutions under hydrothermal conditions, that is, the dissolubilities of the sands increase with treatment temperature, time and the alkaline concentration. The main difference in the dissolubilities of the four sands is correlated with the differences in the sand particle size. The larger the size, the smaller the dissolubility. The dissolved silica solutions were successfully used as silica source to prepare mesoporous/microporous silicas without significant difference. The yield of the synthesized silicas decreases sharply when the pH of the dissolved silica sand solution was adjusted to be higher than 9.5. The meso- and micro-silicas prepared at pH of 9.5 and 11 using the cheaper sand from a desert were evaluated in the fixed-bed adsorption of methylene blue (MB) from aqueous solution. It is found that both silicas have good fixed-bed performance toward MB. And the adsorption well fits the Thomas model. The column packed with the microporous silica has longer breakthrough and exhaustion times than with the mesoporous one. [ABSTRACT FROM AUTHOR]

[Display omitted] • First adsorption study of adsorption of 2-hydroxyethylammonium acetate [Mea][Ac] and 2-hydroxyethylammonium hexanoate [Mea][Hex] • Recovery of Protic Ionic liquids mixture [Mea][Ac]/Mea][Hex] from liquor by fixed-bed adsorption with AC was evaluated. • Superficial velocity is key factor regarding the recovery of [Mea][Ac]/[Mea][Hex]. • Fixed-bed adsorption with AC was found as a possibility for [Mea][Ac]/[Mea][Hex] recovery from the lignocellulosic pretreatment liquor. Integrated strategies using fixed bed columns can facilitate the recovery of protic ionic liquids (PILs) used in the pretreatment of lignocellulosic biomass. In this study, we investigated the adsorption of 2-hydroxyethylammonium acetate [Mea][Ac] and 2-hydroxyethylammonium hexanoate [Mea][Hex] on activated carbon in a fixed bed column for recovering the PILs mixture present in the liquor of the pretreatment. Breakthrough curves were determined experimentally. Breakthrough time (t b), exhaustion time (t e), difference between t b and t e , adsorption efficiency (ϕ ads), column efficiency (ϕ col) and q e equilibrium capacity were evaluated as a function of simultaneous variations in superficial velocity (v s) and temperature (T) using a central composite rotatable design. The optimum conditions for PIL purification were v s = 1.66 cm/min (Q = 1.3 mL/min) and T = 20 °C. After selection of optimum operating conditions, PILs separation was evaluated in a model solution and sugarcane pretreatment liquor, with similar intervals for recover of PILs. This is the first study to develop a successful proof of concept of mixture PILs [Mea][Ac]/[Mea][Hex] recovery from sugarcane straw pretreatment liquor in a fixed-bed column of activated carbon. The results indicate that the method has great potential for industrial application. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zinc and iron modified biochar (ZnFeBC) exhibits high specific surface area. • ZnFeBC is effective for treatment of selenium. • ZnFeBC demonstrates a promising potential to treat real water matrices. • Mass transfer modeling is beneficial for scaling up fixed-bed reactors. Biochar composites have been gaining attention in recent years as a promising and cost-effective material for wastewater treatment. In the present study, a novel procedure was developed to create a biochar (BC) composite impregnated with binary zinc (Zn) and iron (Fe) oxides (denoted as ZnFeBC). The procedure was optimized to enhance selenite, Se(IV), adsorption performance of the ZnFeBC composite. The modified biochar composite had excellent pore characteristics with a specific surface area of 854 m2/g. The maximum Se(IV) adsorption capacity of an unary Zn-loaded biochar composite was 520 µg/g, which significantly increased to 4,100 µg/g after the iron oxide impregnation. Isotherm experiments suggested that the adsorption process was likely through homogeneous monolayer adsorption. The ZnFeBC composite exhibited excellent performance over a broad range of pH values, with the highest Se(IV) adsorption capacities observed at lower pH values (maximums at pH 3). X-ray absorption near edge structure spectroscopy (XANES) indicated that the redox reaction of Se oxyanions did not occur during the adsorption process. ZnFeBC was successfully used to remove Se(IV) from a mining lake water matrix in a fixed-bed adsorption system. Additionally, a mass transfer model optimizing effective diffusion and external mass transfer coefficients was developed to comprehensively assess the adsorption system. Overall, ZnFeBC exhibited great potential as an adsorbent for treating Se(IV) contaminated waters and the developed mass transfer model is useful for scaling up fixed-bed adsorption systems. [ABSTRACT FROM AUTHOR]

Molecularly imprinted polymers (MIPs) have been widely used in the field of environmental engineering, but the traditional MIPs are still not green because large quantities of organic porogen and hazardous functional monomers are required during the preparation process. To overcome these challenges, the green deep eutectic solvent (DES) and water were separately used as functional monomer and porogen to prepare molecularly imprinted polymer (MIP). Herein, the multiple functional groups on DES can form various forces with the target (bisphenol A, BPA) resisting the interference of water molecules. Characterization showed MIP had rough surface and rich functional groups. Results of batch experiments demonstrated that the MIP had a maximum adsorption capacity of 110.15 mg g−1 toward BPA from water and the Freundlich isotherm and pseudo-second-order kinetic models were suitable for analyzing the BPA adsorption process. Results of fixed-bed column illustrated that the breakthrough time prolonged with the adsorbent mass increasing, while forwarded with the BPA inlet concentration and flow rate increasing. Both Thomas and Yoon Nelson models could effectively describe fixed-bed adsorption. Additionally, the MIP was used as a pretreatment column adsorbent in combination with HPLC for the determination of BPA in eight environmental samples with satisfactory recoveries (91.02–108.20%). And the selective recognition mechanism of MIP for BPA was due to the combination of imprinting effect, hydrogen bonding and π-π stacking. In this work, a promising way has been developed to prepare green MIP for the selective adsorption of BPA in the field of environmental chemical engineering. [Display omitted] • A deep eutectic solvent-molecularly imprinted polymer was prepared in water. • The MIP had excellent adsorption capacity and selectivity for BPA in water. • The fixed-bed column adsorption was evaluated fairly well by the theory models. • The pretreatment column based on MIP can be used for the determination of BPA in environmental samples. [ABSTRACT FROM AUTHOR]

Fixed-bed column studies were performed using magnetized sawdust (Fe3O4–SD) as adsorbent for removal of Cu(II) and Ni(II) ions form aqueous solutions. Breakthrough curves were obtained by performing experiments in order to evaluate the influence of adsorbent bed height (2, 4, 8 cm), metal ion concentration in feed solution (10, 20, 30 mg/L), and feed flow rate (15, 20, 25 mL/min) for adsorption of Cu(II) and Ni(II) ions onto Fe3O4–SD adsorbent. Adsorption kinetics was analyzed using Bohart–Adams, Thomas, and Yoon–Nelson models. Kinetic data correlated well with both Thomas and Yoon–Nelson models, while Bohart–Adams model poorly predicted the model operation. Saturation loading capacity of adsorbent bed decreased with increase in adsorbent bed height, metal concentration in feed, and feed flow rate. Both mass transfer zone (MTZ) height and height of unused bed (HUNB) noticeably increased with increase in the values of the parameter studied. The results showed that reduced MTZ height and lowestHUNBare suitable for operating the column satisfactorily. [ABSTRACT FROM AUTHOR]

The presence of sulfonamide antibiotics in aquatic environments poses potential risks to human health and ecosystems. In the present study, a highly porous activated carbon was prepared by KOH activation of an anthracite coal (Anth-KOH), and its adsorption properties toward two sulfonamides (sulfamethoxazole and sulfapyridine) and three smaller-sized monoaromatics (phenol, 4-nitrophenol and 1,3-dinitrobenzene) were examined in both batch and fixed-bed adsorption experiments to probe the interplay between adsorbate molecular size and adsorbent pore structure. A commercial powder microporous activated carbon (PAC) and a commercial mesoporous carbon (CMK-3) possessing distinct pore properties were included as comparative adsorbents. Among the three adsorbents Anth-KOH exhibited the largest adsorption capacities for all test adsorbates (especially the two sulfonamides) in both batch mode and fixed-bed mode. After being normalized by the adsorbent surface area, the batch adsorption isotherms of sulfonamides on PAC and Anth-KOH were displaced upward relative to the isotherms on CMK-3, likely due to the micropore-filling effect facilitated by the microporosity of adsorbents. In the fixed-bed mode, the surface area-normalized adsorption capacities of Anth-KOH for sulfonamides were close to that of CMK-3, and higher than that of PAC. The irregular, closed micropores of PAC might impede the diffusion of the relatively large-sized sulfonamide molecules and in turn led to lowered fixed-bed adsorption capacities. The overall superior adsorption of sulfonamides on Anth-KOH can be attributed to its large specific surface area (2514 m 2 /g), high pore volume (1.23 cm 3 /g) and large micropore sizes (centered at 2.0 nm). These findings imply that KOH-activated anthracite coal is a promising adsorbent for the removal of sulfonamide antibiotics from aqueous solution. [ABSTRACT FROM AUTHOR]

Lean methane emissions (0.15–0.5% CH 4 ) often contain low concentrations of sulphur compounds (e.g. H 2 S). Regenerative catalytic oxidation is an efficient process for methane removal and upgrading of these streams, but the presence of sulphur compounds deactivates typical combustion catalysts. We propose in this work a new strategy for overcoming this problem, by using a reverse flow reactor provided with integrated adsorption beds. Therefore, it is possible to operate autothermically with low methane concentrations, as well as effectively separate the sulphur compounds before reaching catalytic bed. The working principle of this device has been experimentally demonstrated in a bench-scale reactor working at conditions typical for industrial emissions (GHSV = 1146 h − 1 , 4300 ppm CH 4 , 100–500 ppm H 2 S). It has been found that molecular sieve 5A is a suitable adsorbent for this device. The influence of the main reverse flow reactor variables, switching time (200–400 s) and methane feed concentration (4000–4500 ppm), on the performance of the process has been studied. The integrated adsorption performs better at switching time 400 s, while methane concentration has negligible influence, provided that the reactor is maintained ignited. [ABSTRACT FROM AUTHOR]

Adsorption of ibuprofen and tetracycline onto a commercial granular activated carbon, multi-walled carbon nanotubes, and two low-cost activated carbons synthesized in the laboratory, has been investigated. The kinetic experimental data obtained at 30 °C and 250 r.p.m. were fitted to pseudo-first, pseudo-second and Elovich models, obtaining a high accuracy between the experimental data and the pseudo-second order equation. Therefore, the equilibrium adsorption data were analyzed by using Langmuir, Freundlich, Sips, Guggenheim–Anderson–de Boer, and Tempkin models. The highest ibuprofen adsorption capacity was obtained for AC-RH activated carbon, 239.8 mg g −1 , and in the case of tetracycline removal was of 845.9 mg g −1 onto the peach stones activated carbon. These results are linked to the textural and chemical surface properties of the adsorbents. Fixed-bed experiments allowed obtaining good removal efficiencies at breakthrough time, 97.2% for ibuprofen and 96.1% for tetracycline onto activated carbon from rice husk. Desorption efficiencies were moderate in all systems, being higher by using NaOH solution at high concentration as elution agent. Finally, the important role of the acidic functionalities in the adsorption process was demonstrated by the accomplishment of FTIR studies of the adsorbents before and after the adsorption of both pharmaceutical compounds. [ABSTRACT FROM AUTHOR]

[Display omitted] • Regeneration of F-loaded HZO@D201 nanocomposite was systematically investigated. • 1% NaOH-2% NaCl binary solution fully refresh F-loaded HZO@D201 within 10 min. • Regeneration was dominated by ligand exchange between fluoride and hydroxide ions. • Desorption reagent was recycled for cyclic runs with constant desorption efficiency. Nano-hydrous zirconium oxide (HZO) was among the most attractive adsorbents for water defluoridation in terms of environmental friendliness, high capacity and water insolubility. However, the systematic investigation on regeneration of the exhausted nano-HZO, which is crucial to the potential application, is rarely reported. Herein, the nanocomposite HZO@D201 containing nano-HZO for inner-sphere complexation with fluoride, and the strongly basic anion exchanger D201 host for electrostatic attraction, was adopted to investigate the regeneration performance and mechanism. The NaOH-NaCl binary solution was employed as the regenerant. In specific, NaOH was responsible for desorbing fluoride from nano-HZO through surface deprotonation reaction, and NaCl for suppressing electrostatic attraction. By utilizing the response surface methodology, the desorption efficiency of the fluoride-loaded HZO@D201 (denoted as F-HZO@D201) exceeded 95% after treatment with 1% NaOH-2% NaCl for 10 min in the batch assay. As a comparison, the treatment with 5% NaOH-5% NaCl for 24 h was adopted as the empirical regeneration condition previously. The desorption efficiency reached ∼100% with 2-bed volume regenerant in the column test. The adsorption isotherm plots of the desorbed F-HZO@D201 overlapped with the pristine HZO@D201, demonstrating that F-HZO@D201 was fully refreshed. Evolution of crystalline structure of HZO, XPS F1s spectra, FT-IR spectra, and concentration of each reagent was monitored, suggesting ligand exchange between fluoride and hydroxide ion as the main desorption mechanism. After adding CaCl 2 and NaOH to remove fluoride and to restore the alkali concentration, respectively, the used regenerant was recycled in a 5-cyclic regeneration run with constant desorption efficiency (>95%). [ABSTRACT FROM AUTHOR]

This work evaluates the feasibility of common adsorbents (carbonaceous materials, zeolites and metal-organic frameworks) for the adsorption and further methane upgrading of the ventilation air methane (VAM) emissions from underground coal mining (0.57% CH 4). Concentration was achieved by adsorption through two different operational procedures based on fixed bed configurations: temperature swing adsorption (TSA) and pressure swing adsorption (PSA). All the combinations have been simulated using a rigorous mathematical model implemented in a commercial simulation package. The main purpose is to evaluate the performance of the different combinations of adsorption technique and adsorbent material, as well as establishing a valid mathematical model able to test a wide range of materials. The comparison has been fulfilled with an economic evaluation of the different combinations. Results show that carbonaceous materials provide the highest concentration factors (C/C 0 = 5), with low total methane recoveries (30%) and the lowest cost per kmol of methane recovered (1.5 €/kmol). MOFs can retain substantial amounts of methane, but with lower CH 4 /N 2 selectivities than carbonaceous materials and lower methane concentration factors (C/C 0 = 2.6). For this type of materials, a high recovery of methane is achieved, but at expense of the highest costs (80 €/kmol). Finally, zeolitic materials present the lowest methane concentration factor (C/C 0 = 2), with intermediate both methane recoveries (58%) and costs (25 €/kmol). Concerning the adsorption technique, TSA has shown higher final methane concentrations for carbonaceous materials and some MOFs, whereas PSA overperforms for zeolitic materials. In addition, TSA is cheaper in all cases than PSA processes. On the other hand, PSA allows higher total methane recoveries and adsorption capacities for all materials, highlighting the high dependence on adsorption pressure, especially in carbonaceous materials (PSA/TSA = 18.3, in the case of Maxsorb). [Display omitted] • Low-grade ventilation air methane (VAM) emissions can be adsorbed and concentrated. • Three different adsorbent materials were studied: carbons, zeolites and MOFs. • Two different adsorption techniques were studied: TSA and PSA. • The performance comparison was completed with an economic balance for each case. • Results show the main important features for improving the methane recovery. [ABSTRACT FROM AUTHOR]

Application of mesoporous activated alumina functionalized with diethanolamine (DAAB) for selective adsorption of carbon dioxide (CO2) from its mixture with nitrogen gas was investigated. Morphological structure, elemental composition and the functional groups present in the DAAB were analyzed using the scanning electron microscopy; energy dispersive X-ray technique and Fourier transform infrared analysis. Investigation of effect of the gas mixture feed flow rate, column adsorption temperature, DAAB bed height and concentration of CO2 in the feed stream revealed that 90 mL/min, 35 °C, 3 g and 10% of CO2, respectively were the optimum operating conditions for the highest adsorption capacity of 55.94 mg/g. The DAAB multi-cycle CO2 adsorption test revealed that it can be reused successfully for about 13 times with high sorption capacity. The DAAB is a promising adsorbent that can be used to capture CO2 pollutant molecules. [ABSTRACT FROM AUTHOR]

A low-cost, non-toxic and effective adsorbent constituted by a montmorillonite coated by iron oxides (montmorillonite-iron oxide composite) was prepared to assess its effectiveness in the removal of Cs and Sr from aqueous solution. Dynamic adsorption experiments were carried out at room temperature under the effect of various operating parameters such as bed depth Z (5-15 cm), initial cation concentration C (2-50 mg L) and volumetric flow rate Q (0.5-8 mL min). Column performance has been modeled with constant-pattern wave approach combined to the Freundlich isotherm model and artificial neural network (ANN) models. The time, initial cation concentration, bed depth and volumetric flow rate were chosen as the input variables whereas, the outlet concentration C was considered as the output variable. The developed network was found to be useful in predicting the breakthrough curves. Experimental data for the used system were well fitted with ANN than the combined constant-pattern wave approach. [ABSTRACT FROM AUTHOR]

Highlights: [•] We develop a novel process for erythromycin A separation from fermentation broth. [•] Pore diffusion limits the rate of fixed-bed adsorption of erythromycin onto resins. [•] Erythromycin recovery efficiency from filtrated broth into butyl acetate is over 96%. [•] Selectivity of Erythromycin A over Erythromycin C is 2.2 in aqueous crystallization. [Copyright &y& Elsevier]