Fixed-bed Studies Research Articles

Fixed-bed column dynamic studies and breakthrough curve analysis of Eu(III) ion adsorption onto chemically modified SBA-15 silica materials

ABSTRACTA continuous fixed bed study was carried out by using two SBA-15 mesoporous silica materials decorated with Schiff base ligands for the removal of Eu(III) from aqueous solutions. The impact of flow rates of the sample and eluent, column bed height, sample, and eluent volumes was investigated. The analysis of the breakthrough investigations showed the exhaustion time, exhaustion volume, and metal uptake capacities accrued with a decrease in the flow rate and with an increase in the bed height. Thomas and Yan models were fitted to the experimental data to work out the characteristic parameters of the column for process design.

Cow bones char as a green sorbent for fluorides removal from aqueous solutions: batch and fixed-bed studies.

Cow bone char was investigated as sorbent for the defluoridation of aqueous solutions. The cow bone char was characterized in terms of its morphology, chemical composition, and functional groups present on the bone char surface using different analytical techniques: SEM, EDS, N2-BET method, and FTIR. Batch equilibrium studies were performed for the bone chars prepared using different procedures. The highest sorption capacities for fluoride were obtained for the acid washed (q=6.2±0.5mg/g) and Al-doped (q=6.4±0.3mg/g) bone chars. Langmuir and Freundlich models fitted well the equilibrium sorption data. Fluoride removal rate in batch system is fast in the first 5h, decreasing after this time until achieving equilibrium due to pore diffusion. The presence of carbonate and bicarbonate ions in the aqueous solution contributes to a decrease of the fluoride sorption capacity of the bone char by 79 and 31%, respectively. Regeneration of the F-loaded bone char using 0.5M NaOH solution leads to a sorption capacity for fluoride of 3.1mg/g in the second loading cycle. Fluoride breakthrough curve obtained in a fixed-bed column presents an asymmetrical S-shaped form, with a slow approach of C/C 0→1.0 due to pore diffusion phenomena. Considering the guideline value for drinking water of 1.5mgF-/L, as recommended by World Health Organization, the service cycle for fluoride removal was of 71.0h ([F-]feed∼9mg/L; flow rate=1mL/min; m sorbent=12.6g). A mass transfer model considering the pore diffusion was able to satisfactorily describe the experimental data obtained in batch and continuous systems.

Removal of Multi-active-blue Dye from Aqueous Phase using Magnetic Poly-pyrrole Nano-composites: Fixed-bed Adsorption Studies

Removal of Multi-active-blue Dye from Aqueous Phase using Magnetic Poly-pyrrole Nano-composites: Fixed-bed Adsorption Studies

Thermodynamics and kinetics study of defluoridation using Ca-SiO2-TiO2 as adsorbent: Column studies and statistical approach

Fluoride contamination of water is a potential health and environmental hazard worldwide. This study focuses on defluoridation efficiency in aqueous system by novel adsorbents, i.e., calcium impregnated silica (Ca-SiO2) and calcium impregnated silica combined with titanium dioxide (Ca-SiO2-TiO2). Comparative batch study was carried out using both adsorbents Ca-SiO2 and Ca-SiO2-TiO2 for fluoride removal efficiency in different experimental conditions where it was observed that chemically modified Ca-SiO2-TiO2 acted as a better adsorbent for defluoridation than Ca-SiO2. Thus, further batch isotherm and kinetics studies were performed using Ca-SiO2-TiO2. The phenomenon of fluoride ion uptake is realized by Langmuir and Freundlich isotherm model. Langmuir isotherm shows satisfactory fit to the experimental data. The rate of adsorption shows that the pseudo-second-order rate fitted the adsorption kinetics better than the pseudo-first-order rate equation. The mechanism of adsorption process was illustrated by calculating Gibbs free energy, enthalpy and entropy from thermodynamic studies. To further confirm the applicability of the adsorbent, a fixed bed study was carried out in column mode. Thomas and bed-depth-service-time (BDST) model were well-fitted to the experimental results. The optimal operating conditions of defluoridation were found by using response surface methodology (RSM) with the help of Design Expert Software. The maximum percentage of fluoride removal was 92.41% in case of calcium impregnated silica combined with titanium dioxide (Ca-SiO2-TiO2). Thus, it may be concluded that chemically synthesized Ca-SiO2-TiO2 could be used as an environmentally and economically safe adsorbent for defluoridation of waste water.

STUDY OF BINARY AND SINGLE BIOSORPTION BY THE FLOATING AQUATIC MACROPHYTE Salvinia natans

Abstract The performance of Salvinia natans macrophyte to recover lead and chromium from single and bicomponent solutions in batch and fixed bed systems was investigated. Equilibrium data were obtained through isotherms and fitted to Langmuir, Freundlich and D-R models for a single component system. In the fixed bed study the breakthrough curves were carried out at three different ratios of concentrations for the bicomponent study and at the concentration of 1 mmol.L-1 for the single system. In order to know the biosorption mechanism, FT-IR analyses were performed for S. natans before and after the uptake of metal ions. The results showed different functional groups in the biomass and the ability of these groups to bind Cr+3 and Pb2+. Studies of the binary system of Cr3+/Pb2+ are not common in the literature, which makes the experimental data obtained in this work very important for providing information that could be used in adsorption processes.

Enhanced removal of sulfonamide antibiotics by KOH-activated anthracite coal: Batch and fixed-bed studies

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 m2/g), high pore volume (1.23 cm3/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.

Adsorptive removal of As(III) ions from water using spent grain modified by polyacrylamide

In order to enhance the removal efficiency of As(III), a pre-oxidation process is generally applied first to convert As(III) to As(V), which may cause unwanted new contaminants. To overcome this problem, efforts were made to develop an effective way to remove As(III) directly without an oxidation step. The effect of polyacrylamide polymers (PAMs) such as anionic PAM, cationic PAM and nonionic PAM, on As(III) ion adsorption by spent grain (SG) was investigated. The physico-chemical properties of the three PAM-polymerized SGs (APSG (anionic PAM-polymerized modified spent grain), CPSG (cationic PAM-polymerized spent grain) and NPSG (nonionic PAM-polymerized spent grain)) were analyzed using Fourier transform infrared (FT-IR), scanning electron microscope (SEM) and zeta potential. Batch experimental data showed that the sequence of preferential adsorption for As(III) was APSG>CPSG>NPSG. Active functional groups such as amino group (NH2), carbonyl group (CO), C–N bond of the amide group (CONH2), and hydroxyl group (O–H) were responsible for As(III) adsorption. Many tubular structures occurring on the surface of APSG possibly increase the specific surface areas and favor the adsorption of As(III) ions. A fixed-bed study was carried out by using APSG as an adsorbent for As(III) from water. Three factors such as bed height, initial concentration and flow rate were studied, and breakthrough curves of As(III) were obtained. The Adams–Bohart model was used to analyze the experimental data and the model parameters were evaluated.

Adsorption of vanillin and syringaldehyde onto a macroporous polymeric resin

Pulp and paper mill and biorefinery side-streams are rich in lignin which can be partially converted to vanillin and syringaldehyde through an oxidation process. These value-added compounds can be recovered with an integrated separation process encompassing an adsorption step. In this work the potential of a macroporous polymeric resin, Sepabeads SP700, was assessed.The resin was characterized regarding particle size, solid density, apparent density and particle porosity by means of laser dispersion, helium pycnometry and mercury intrusion porosimetry, respectively. Values within the ranges given by supplier were achieved: solid density, apparent density, particle size and particle porosity were 1294gL−1, 1012gL−1, 483μm and 0.73mLporesmL−1particle, respectively.Batch equilibrium isotherms for three different temperatures 283/288, 298 and 333K were found for vanillin and syringaldehyde in aqueous solutions. Experimental results were fitted to Langmuir and Freundlich isotherm models. Equilibrium isotherms were validated by fixed bed studies at different temperatures and feed concentrations. A mathematical model comprising the equilibrium isotherms, linear driving force approximation, and intraparticle mass transfer resistances was used to describe the adsorption/desorption histories of concentration at the outlet of the fixed bed experiments. Although Langmuir model reasonably fit to the experimental results, the empirical Freundlich model was best to describe the experimental results for equilibrium concentrations bellow 1gL−1.

Investigation on the adsorption of phosphorus by Fe-loaded ceramic adsorbent

This aim of this study was to remove phosphorus from aqueous solution using a Fe-loaded ceramic (Fe-LC) adsorbent prepared by mixing dolomite, montmorillonite, FeSO4·7H2O and starch. Simplex-centroid mixture design method was used to determine the optimum mixture proportions by evaluating both phosphorus adsorption efficiency and adsorbent hardness. The study found that the optimum adsorption capacity and the strength can be achieved with the composition of 3.87g dolomite, 3.00g starch, 2.13g montmorillonite and 1.00g FeSO4·7H2O (10g in total). The optimized Fe-LC was evaluated in the batch and the fixed bed experiments. The point of zero charge, pHpzc was found to be 6.0. The adsorption kinetic and isotherm data well agreed with the pseudo-second-order kinetic and the Langmuir isotherm models, respectively. The breakthrough time increased with increasing in the bed depth, whereas inverse relationship was observed with the initial phosphorus concentration in the fixed bed studies. The co-existing anions (SO42−, NO3− and Cl−) had negligible influence on phosphorus removal. The BDST and Thomas model explained the breakthrough behavior for phosphorus removal with a high degree of correlation.

Multiwalled carbon nanotube–polyurethane (MWCNT/PU) composite adsorbent for safranin T and Pb(II) removal from aqueous solution: Batch and fixed-bed studies

Multiwalled carbon nanotube–polyurethane (MWCNT/PU) composite was synthesized and used as a novel adsorbent for safranin T and Pb(II) removal from aqueous solution. The experimental data conformed to Langmuir isotherm suggesting monolayer adsorption of both dye/metal. The adsorbent proved to be highly efficient with high BET surface area (491m2/g) and high monolayer adsorption capacity (qm) of 500mg/g (safranin T) and 270.27mg/g [Pb(II)]. Column studies gave a breakthrough capacity of 425.25mg/g (safranin T) and 239.05mg/g [Pb(II)]. The data followed pseudo-second order kinetics, with both liquid-film and intra-particle diffusion controlling the overall mechanism. The adsorption process was spontaneous and endothermic. The efficiency of the adsorbent for treatment of real wastewater samples under optimized conditions was evaluated.

Continuous fixed bed removal of Novacron Orange P-2R using sugarcane bagasse: prediction of breakthrough curves

A continuous fixed-bed study was carried out using polyethylenimine (PEI)-modified sugarcane bagasse as low-cost biosorbent for the removal of Novacron Orange P-2R reactive dye. The effect of different process parameters viz. bed height (1–3) cm, flow rate (3.6–7.2) mL/min, and initial dye concentration (25–75) mg/L on the biosorption capacity of PEI-modified sugarcane bagasse was investigated. The optimum bed height, flow rate, and initial dye concentration were found to be 3 cm, 3.6 mL/min, and 75 mg/L, respectively. The optimum biosorption capacities were observed to be 20.25 and 23.62 mg/g. The results suggested that the biosorption capacity and breakthrough curves were depended on process parameters. Data obtained from dynamic study were evaluated using the Thomas and Bed Depth Service Time models. Both of these models showed the good fitness and close agreement with experimental results at all experimental conditions, which indicated that both were well fitted for PEI-modified sugarcane bagasse. The results showed that the PEI-modified sugarcane bagasse could be used as a low-cost and efficient fixed-bed biosorbent for the elimination of the reactive dye from aqueous solution in column mode. The novelty of this work is the good efficiency of this PEI-treated agro waste for removal of this widely used reactive dye in continuous mode.

Separating closely resembling steroids with ionic liquids in liquid–liquid extraction systems

Separation of steroids by liquid–liquid extraction with ionic liquids (ILs) as solvent was studied both experimentally and by simulation using a model mixture of progesterone and pregnenolone. The studies involved a solvent screening using COSMO-RS software for estimation of progesterone solubility. An experimental compatibility study of several solvents with reasonable progesterone solubility with several ILs. The results showed tert-butyl methyl ether (TBME)–butyl methyl imidazolium tetrafluoroborate (BMIM BF4) as the most promising solvent combination. Next, equilibrium partitioning of both progesterone and pregnenolone in this solvent combination was determined experimentally. Fixed bed studies using solvent impregnated resin (SIR) obtained by impregnation of BMIM BF4 in silica showed that it is feasible to obtain highly pure progesterone in such a process. However, the yield was far from quantitative and thus a fractional extraction process was studied by simulation of a counter current extraction process. The simulation study showed that with fractional extraction highly pure progesterone (excess >0.99) can be obtained at a yield of >0.95 when a minimum of 24 equilibrium stages are applied.

Continuous adsorption study of congo red using tea waste in a fixed-bed column

In this paper, continuous fixed-bed studies were carried out to investigate the feasibility of using tea waste (TW) as a low-cost adsorbent for the removal of Congo red (CR) from aqueous solution. Effects of various parameters, such as mass of the adsorbent, flow rate, influent dye concentration, and initial pH were investigated. It was found that the amount of the column adsorption capacity was at about 3 mg/g. Three commonest models, namely Adams–Bohart, Thomas, and Yoon–Nelson models have been employed to predict the adsorption breakthrough curves of CR onto TW. The Adams–Bohart model satisfactorily predicts the initial parts of the adsorption process with the correlation coefficient at about 0.9. The Thomas and Yoon–Nelson models were found to be in reasonable agreement with the experimental data. In addition, the bed depth service time (BDST) model was applied at different bed depths. The results revealed that the experimental data greatly described using BDST model. It was concluded that the fixed-bed adsorption column with TW adsorbent can be used as a wastewater treatment for the removal of CR.

Development of Novel Iron Crosslinked CMC Nanoadsorbents for the Remediation of Arsenic Ions

Iron crosslinked carboxy methyl cellulose (CMC) nanoparticles prepared by the process of emulsion crosslinking were studied for the removal of arsenic(V) ions from aqueous solution. Batch and column studies were conducted in order to investigate the efficiency of nanoparticles towards arsenic remediation. The Langmuir and Freundlich equations were applied to describe the biosorption isotherm. The results obtained from fixed bed studies showed that the column demonstrates fairly well at lowest flow rate and also, bed exhaustion time was found to increase with increasing bed height. The bed depth service time (BDST) model was used to analyze the experimental data and the model parameters were evaluated. Antibacterial studies were also conducted which confirms that Fe-CMC nanoparticles are efficient towards the removal of bacteriological contamination also.

Fixed-bed study and modeling of selective phenanthrene removal from surfactant solutions

Abstract Recovering and then recycling surfactant solution is required in the surfactant-enhanced remediation (SER) of contaminated sites and groundwater to reduce operating costs and prevent secondary contamination. In this study, fixed-beds with activated carbon were employed to selectively remove phenanthrene from Triton X-100 (TX100) aqueous solution as a potential model system for the recovery of surfactant solution in SER. The effects of various operating conditions such as flow rate, bed height, and influent phenanthrene concentration on the performance of the fixed beds were investigated. The sorption of TX100 in the fixed-bed can rapidly reach saturation, but the effluent concentrations of phenanthrene are much lower than its influent concentrations, even with a great volume of solution flowing through the columns. The total removal percentage of phenanthrene from effluent solution was greater than the sorption loss of TX100 under all experimental conditions. The corresponding selectivity parameters for phenanthrene removal versus surfactant sorption were all greater than 4.0, a selectivity value representing 80% phenanthrene removal and 80% surfactant retention. Moreover, better selectivity was obtained at a higher bed height and lower flow rate, but had little dependence on the influent phenanthrene concentration. The constant-pattern model and the apparent partition coefficient were applied successfully to describe and predict the breakthrough curves of TX100 and phenanthrene in fixed-bed columns. The results suggested that fixed-beds could be effectively used to recover surfactant solutions from the washing effluents in SER.

Adsorption performance of packed bed column for nitrate removal using PAN-oxime-nano Fe2O3.

A continuous fixed bed study was carried out by using PAN-oxime-nano Fe2O3 as a sorbent for the removal of nitrate from aqueous solution. The effect of factors, such as flow rate (2, 5 and 7 mL/min) and bed depth (5, 10 and 15 cm) were studied. Data confirmed that the breakthrough curves were dependent on flow rate and bed depth. The adsoption capacities observed in diffent conditions of flow rates (2,5 and 7 mL/min) were 11.65, 24.38 and 25.89, respectively. Thomas model was applied to experimental data to predict the breakthrough curves using linear regression and to determine the characteristic parameters of the packed bed column. Bed depth/service time analysis (BDST) model was used to investigate the effect of bed depth on breakthrough curves. The results showed that Thomas model was suitable for the normal description of breakthrough curve at the experimental condition. The data were in good agreement with BDST model with R2 > 0.98. Statistical analyses were performed on fluoride removal obtained from different flow rates using SPSS16 software by applying Kruskal- Wallis test. These findings suggested that PAN-oxime-nano Fe2O3 in the column structure presents a great potential in removal of nitrate from aqueous solutions.

Fixed-bed study of ammonia removal from aqueous solutions using natural zeolite

Purpose – The purpose of this paper is to investigate the performance of natural Jordanian zeolite tuff to remove ammonia from aqueous solutions using a laboratory batch method and fixed-bed column apparatus. Equilibrium data were fitted to Langmuir and Freundlich models. Design/methodology/approach – Column experiments were conducted in packed bed column. The used apparatus consisted of a bench-mounted glass column of 2.5 cm inside diameter and 100 cm height (column volume = 490 cm3). The column was packed with a certain amount of zeolite to give the desired bed height. The feeding solution was supplied from a 30 liter plastic container at the beginning of each experiment and fed to the column down-flow through a glass flow meter having a working range of 10-280ml/min. Findings – Ammonium ion exchange by natural Jordanian zeolite data were fitted by Langmuir and Freundlich isotherms. Continuous sorption of ammonium ions by natural Jordanian zeolite tuff has proven to be effective in decreasing concentrations ranging from 15-50 mg NH4-N/L down to levels below 1 mg/l. Breakthrough time increased by increasing the bed depth as well as decreasing zeolite particle size, solution flow-rate, initial NH4+ concentration and pH. Sorption of ammonium by the zeolite under the tested conditions gave the sorption capacity of 28 mg NH4-N/L at 20°C, and 32 mg NH4-N/L at 30°C. Originality/value – This research investigates the performance of natural Jordanian zeolite tuff to remove ammonia from aqueous solutions using a laboratory batch method and fixed-bed column apparatus. The equilibrium data of the sorption of Ammonia were plotted by using the Langmuir and Freundlich isotherms, then the experimental data were compared to the predictions of the above equilibrium isotherm models. It is clear that the NH4+ ion exchange data fitted better with Langmuir isotherm than with Freundlich model and gave an adequate correlation coefficient value.

Batch and Fixed-Bed Study for Basic Blue 9 Separations using Synthetic Activated Carbon

A local olive stone is a low cost and promising industrial waste with cellulose-lignin polymeric structure. The stones were dried, crushed, impregnated with phosphoric acid, and carbonized at 673 K for 3 h and used for the removal of basic blue dye (BB9) under different conditions. Equilibrium isotherms and different adsorption models, Langmuir and Freundlich, have been investigated. Different kinetic models have been studied in terms of pseudo first order and pseudo second order rate constants. In addition, the thermodynamic parameters have been calculated. The obtained results showed that the activated carbon has high adsorption capacity of BB9 and the adsorption process was found to increase on increasing temperature and pH. The Langmuir isotherm was better fitted for the experimental data. Moreover, the process involves pseudo second order kinetics and values of the change in entropy and heat of adsorption for BB9 adsorption on activated carbon were positive suggesting the adsorption process to be endothermic. The high negative value of change in Gibbs free energy indicates the feasible and spontaneous adsorption of BB9 dyes. The highest uptake capacity was obtained when a 4 cm bed depth was used at an inlet concentration of 80 mg L −1 and a flow rate of 4 cm 3 min −1 .

Cationic Basic Yellow 2 (BY2) adsorption onto manure ash: surface properties and adsorption mechanism

Adsorption of Basic Yellow 2 (BY2) onto manure ash, a waste substance, was studied in batch and fixed-bed studies. In both systems, experiments were conducted by using the UV–visible spectroscopy and by examining the effect of different parameters. In order to obtain the adsorption mechanism of manure ash, its microstructure information must be studied. Surface area, particle size distribution (PSD), and structure of adsorbent were studied with Fourier transform infrared spectroscopy, transmission electron microscopy, and PSD. The surface measurement such as specific surface area and pore volume was measured and calculated using BET method. Nitrogen sorption measurements were employed to investigate the variation in surface and pores properties before and after dye adsorption. The experimental isotherm data were analyzed using Langmuir, Freundlich, Dubinin–Radushkevich (D–R), Temkin, Harkins–Jura, and Frumkin isotherm equations, but high correlation coefficients (R2) confirmed the validity of Langmuir isotherm, with monolayer adsorption capacity (Q0) equal to 1,666.7 mg/g at 45°C. A full thermodynamic evaluation was carried out, calculating the parameters of enthalpy, free energy, and entropy (∆H°, ∆G°, and ∆S°). The thermodynamics of BY2 onto manure ash system indicates spontaneous and endothermic nature of the process. The kinetic models: Lagergren's pseudo-first order, pseudo-second order, intra-particle diffusion, liquid-film diffusion, Bangham and Avrami kinetic models were applied to the experimental data. It was observed that pseudo-second-order kinetic model described the adsorption process better than any other kinetic models. The Adams–Bohart, Thomas, and Yoon–Nelson models were applied to the adsorption under varying experimental conditions to predict the breakthrough curves and to evaluate the model parameters of the fixed-bed column that are useful for process design.

Adsorption of textile dye Reactive Red 120 by the chitosan–Fe(III)-crosslinked: Batch and fixed-bed studies

This paper presents a study of the use of chitosan–iron(III) crosslinked with glutaraldehyde (Ch-Fe) as an adsorbent for the textile anionic dye Reactive Red 120 (RR120) in batch and fixed-bed systems. The maximum adsorption capacity was calculated from the adsorption isotherms, and well fitted by the Langumir–Freudlich isotherm model. The process followed the kinetic model of pseudo-second-order. In fixed-bed studies, the Thomas, Adams-Bahort and Clark models were applied to the breakthrough curves. The thermodynamic parameters showed that the adsorption process is spontaneous and favorable. The adsorbent can be easily regenerated and reused. The adsorption of the RR120 was optimized using a 33 factorial design, and the initial pH of the dye solution had a significant effect.