Bed Depth Service Time Research Articles

Carbon Black: A Good Adsorbent for Triclosan Removal from Water

Industrial grade carbon black was pretreated and used for adsorption of triclosan (TCS) in water, and its adsorption performance was investigated by static adsorption experiments and fixed bed adsorption experiments. The effects of pH and temperature on the adsorption capacity were investigated and the adsorption performance of carbon black and activated carbon on TCS was compared. As the pH or temperature decreased, the adsorption of TCS by carbon black increased. Carbon black had a maximum adsorption capacity of 18.62 mg/g on TCS, which was somewhat lower than the activated carbon. Furthermore, the breakthrough time increased with increasing bed height, decreasing flow rate and decreasing initial TCS concentration in the fixed bed adsorption studies. The breakthrough time was 14.33 days at a bed depth of 4.2 mm, a flow rate of 2 mL/min, and an initial TCS concentration of 0.5 mg/L TCS. The model from The Bed Depth Service Time (BDST) was well-fitting.

Iron oxide coated sand (IOS): Scale-up analysis and full-scale application for phosphorus removal from goat farm wastewater

Effective eutrophication control, especially for decentralized wastewater treatment, has received increasing attention in recent years. In view of this, iron oxide coated sand (IOS) granules, a recycled waste product from the drinking water industry, was investigated for phosphorus removal from goat farm wastewater, both at laboratory-scale and at full-scale. Brunauer-Emmett-Teller adsorption revealed a high specific surface area (249 m2/g) of the IOS. Fourier Transform Infrared Spectroscopy and X-ray Diffraction demonstrated that Fe(III) compounds are the main functional component and Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy showed that Fe and O elements covered more than 84% of the surface of the IOS. The IOS granules showed good phosphorus adsorption capacity over a wide pH range during laboratory-scale batch tests. Moreover, the phosphorus adsorption was very fast and the residual phosphorus concentration dropped below 0.02 mg/L within an hour at a dosage of 20 g/L. After adsorption, the exhausted IOS could be regenerated by using 0.5 M KOH, and more than 80% adsorption capacity remained. Laboratory-scale column tests with real wastewater originating from a goat farm were run and Bed Depth Service Time and Bohart–Adams models were applied in view of scale-up. Based on this, a full-scale IOS based fixed bed reactor was designed, built and tested at a goat farm. A TP removal efficiency of 99% with a 0.87 m3 IOS fixed bed reactor (fed at 2.2 m3/d) was obtained. The TP concentration in the effluent remained below 0.3 mg/L for nearly 400 days, achieving long term TP removal. This study demonstrates that IOS based treatment is an ecological and environmentally friendly method, suitable for full-scale (decentralized) wastewater treatment.

Continuous fixed-bed column study and adsorption modeling removal of Ni2+, Cu2+, Zn2+ and Cd2+ ions from synthetic acid mine drainage by nanocomposite cellulose hydrogel

Heavy metal ions are widely recognized for their harmful effects on human health and the environment. Heavy metal ions removal using nanocomposite hydrogel is a promising method for industrial applications and process development owing to their utilization in both kinematic and dynamic adsorption process. There is a need to develop simple, low-cost water purification techniques that use biodegradable bio-based natural polymers like cellulose nanocrystal that have been modified with nanomaterials. These innovative functional cellulose nanocrystals-based nanomaterials have been shown to successfully remove a variety of contaminants from wastewater to acceptable levels. Due to their capacity to hold water in their porous structures, hydrogels are the most commonly used 3D polymer mesh materials for environmental remediation. The application of potential hydrogel for the absorption of Cu2+, Ni2+, Zn2+ and Cd2+ ions from an aqueous solution in a packed bed adsorption column was studied in this work. The adsorbent was studied using FTIR, SEM, XRD and TGA. The influence of breakthrough factors such as bed height (10, 17 and 25 cm) influent concentration (10, 20 and 50 mg/L) and the feed flow rate (10, 20 and 30 mL/min) was assessed. Bed Depth Service Time, Thomas and Yoon–Nelson models were used to fit the experimental data. With an increase in bed height, breakthrough and exhaustion time, the removal efficiency rose to 99.42 ± 0.12 for Cu2+, 99.23 ± 1.16 for Ni2+, 99.36 ± 0.89 for Cd2+ and 98.94 ± 0.48 for Zn2+, but declined with increased flow rate and influent concentration. Better performance was observed at a bed height of 25 cm, an influent metal ion concentration of 10 mg/L and a flow velocity of 10 mL/min. The BDST and Yoon–Nelson models were both successfully used to predict the breakthrough curves of heavy metal ions removal.

Modeling of continuous adsorption of greywater pollutants onto sawdust activated carbon bed integrated with sand column

The real greywater samples collected from the IIT Roorkee hostel have been treated using waste biomass-derived activated carbon in continuous operation. The synthesized ZnCl2 impregnated sawdust activated carbon (SAC) has been used to remove the COD, BOD, and TDS concentration from the greywater. The SAC characterization through FESEM-EDX, BET, and FTIR has been performed. The initial concentration of COD, BOD, and TDS in greywater was 670, 275, and 1819.52 mg/L, respectively. The sand column was used to retain the larger suspended solids and dissolved organic matter up to a certain concentration. Sand column effluent with the concentration of 412, 180, and 1116.8 mg/L for COD, BOD, and TDS respectively, was drawn to the adsorption column for studying the influence of flow rate (5, 10, and 15 mL/min) at 15 cm of bed height and the effect of bed height (10 and 20 cm) at 10 mL/min of flow rate. At optimum condition of 10 mL/min flow rate and 10 cm of bed height, the observed adsorption capacities are 3904.62, 1967.3, and 14,936.92 mg/g for the removal of COD, BOD, and TDS, respectively. Further, to comprehend the behavior of the breakthrough curves eight mathematical models, namely, Bohart-Adams, Thomas, Wolborska, Yoon-Nelson, Log Gompertz, Gompertz, Dose-Response, and Bed Depth Service Time (BDST), have been tested.

Continuous Fixed-Bed Column Studies of Textile Effluent Treatment using Multi-Walled Carbon Nanotubes Originated from Rosmarinus officinalis Oil

A continuous adsorption study in a fixed-bed column was carried out using Multi-walled Carbon Nanotubes derived from Rosmarinus officinalis oil as an adsorbent for removing the textile dye Acid blue 40 from an aqueous solution. The adsorbent, MWNTs were prepared from Rosmarinus officinalis oil as a precursor to Fe/Mo catalyst supported on silica at 650 ºC under N2 atmosphere by spray pyrolysis process characterized by scanning electron microscopy, Transmission Electron microscopy, and Raman spectroscopy. The effects of adsorbent bed height (2–6 cm), initial ion concentration (20– 60 mg/L), and flow rate (10–30 mL/min) on the column performance were analyzed. The breakthrough curve was analyzed using the mathematical models of Thomas, Yoon-Nelson, and bed depth service time. The Thomas model at different conditions defined the behaviors of the breakthrough curves. The bed depth service time model showed good agreement with the experimental data. The high values of correlation coefficients (R2 0.9875) obtained indicate the validity of the bed depth service time model for the present column system.

Sorptive elimination of fluoride from contaminated groundwater in a fixed bed column: A kinetic model validation based study

The current investigation involves a continuous adsorption experiment in a packed bed column for the sorptive elucidation of fluoride from contaminated groundwater using an activated soil-clay mixture. Through the combination of naturally accessible laterite soil with silica enriched clay (3:1 ratio), a low-cost Al–Si heterogeneous material has been developed. Following detailed characterization, the developed materials were employed in a long-time column process to achieve a high degree of fluoride separation from real-world groundwater. In a packed bed column investigation, the effect of bed height, initial fluoride concentration, and flow rate on the breakthrough properties of the adsorption system were investigated. By using a non-linear regression equation, three model kinetics, such as the Thomas Model, Adams-Bohart Model, and Yoon-Nelson Model, were fitted to validate the column-based experimental data, by analysing the breakthrough curves profiles, and distinct kinetic parameters. The Bed Depth Service Time Analysis (BDST) model was tested to express the effect of bed height on breakthrough curves, as well as to predict the time for breakthrough, and material depletion under optimal conditions. The Thomas and Yoon-Nelson models were identified to be the most appropriate ones for describing the entire breakthrough curve, whereas the Adams-Bohart model was only utilised to predict the first half of the dynamic process. With correlation coefficients (R2) 0.96, the experimental results were well suited to Thomas, Yoon-Nelson, and Adams-Bohart models. Finally, regeneration assessment was carried out where even after four cycles of operation, regenerated adsorbent showed a rejection efficacy of 78% to fluoride that proves the viability of the material and methodology.

Enhancement effect on adsorbent utilization rate based on Twin–Bed tandem adsorption

The actual adsorption loading of the adsorbent is usually less than the equilibrium capacity in the abatement of volatile organic compounds (VOCs) with industrial fixed-bed adsorption. In this study, the twin-bed tandem adsorption (TBTA) cycle was proposed. Adequate time was ensured for the upstream bed to adsorb and reach saturation via the take-up and protection of the downstream bed, thus utilizing the full capacity of the adsorbent. A mathematical model and an extended bed depth service time (BDST) model were developed to describe the characteristics of the TBTA. Then, fixed-bed adsorption experiments were performed to validate the accuracy of the aforementioned two models. Results of the parametric analysis showed that the best enhancement effect could be achieved at low packing height, low feed concentration and high superficial velocity conditions. By defining the unit energy consumption (UEC) as the fan power consumption for the recovery of contaminants per unit amount, suggestions for adsorption parameters were provided. Tracking the UEC at each concentration point on the breakthrough curve, the relative concentration of 70% to 80% was found to be the cost-efficient switch point for TBTA. This study demonstrated the operational dynamics of the TBTA and parametric effects on adsorption performance. Our findings can help to improve the adsorbent utilization rate in fixed-bed systems.

Continuous biosorption of acid red 27 azo dye by Eichhornia crassipes leaves in a packed-bed column

In this work, the biosorption behavior of acid red 27 (AR27) dye using Eichhornia crassipes leaves (LECs) in a packed-bed column was investigated by varying relevant operational parameters and assessment of mathematical models. Results showed that the zero-charge point of LECs was 2.37 and that optima pH and volumetric flux of the influent solution for AR27 biosorption were 2.0 and 56.5 hbox {L}/hbox {m}^{2}cdot hbox {h}, respectively. The maximum specific and volumetric biosorption capacities were observed at influent AR27 concentrations and with LEC bed heights ranging between 50 and 400 mg/L and 2 and 8 cm, respectively. It was also found that if LEC bed height was increased and volumetric flux and AR27 concentration of the influent solution decreased, service and saturation time increased. Modeling results revealed that the Thomas, bed depth service time, Yoon–Nelson, dose-response, and logistic models accurately described the dynamic performance of the packed-bed column in terms of pH, AR27 concentration, and volumetric flux of influent AR27 solution, as well as that of LEC bed height. The findings revealed that LECs exhibited remarkable potential for the biosorption of AR27 from aqueous solutions in a packed-bed column and could potentially be useful for the treatment of AR27-laden wastewater.

Composite of polypyrrole with sugarcane bagasse cellulosic biomass and adsorption efficiency for 2,4-dicholrophonxy acetic acid in column mode

The 2,4-Dicholorophenoxyacetic acid (2,4-D) is a herbicide used against broad leave herbs and it is carcinogenic and mutagenic in nature, which need to be remediated to avoid negative impact on the living organisms. In view of promising adsorption efficiency of composite materials, the present investigation is focused on the preparation of polypyrrole (PPY) and sugarcane bagasse (SB) based composites. The composites were characterized for surface properties and thermal stability. The prepared composite was utilized for the sequestration of 2,4-D from aqueous solution in column mode as function of bed height, flow rate and 2,4-D concentration. Thomas model was applied to the rate of adsorption at different 2,4-D concentrations, flow rates and bed heights to predict the breakthrough curves. The BDST (bed depth service time) model was also applied to predict the breakthrough curves as function of bed heights. The biosorption capacities of SB and PPY/SB were 6.1 and 8.63 (mg/g), respectively. The results indicated that sugarcane bagasse composite with PPY is efficient adsorbent for the remediation of 2,4-D and could have potential for the removal of herbicides from effluents.

Biochar application in organics and ultra-violet quenching substances removal from sludge dewatering leachate for algae production

Algae production in nutrient rich sludge dewatering leachate after biogas production is a promising option for wastewater treatment plants. However, the ultra-violet (UV) absorbing characteristic of UV-quenching substances (UVQS) existing in these waters can notably reduce the light transmission within the liquid body. The present work demonstrates a comparative adsorptive removal of UVQS, and other organic substances (expressed as COD and TOC) onto the “acid catalyst” functionalised adsorbent (PPhA) and commercial activated carbon (CAC) from leachate originating from leftover sludge dewatering after biogas production. Laboratory scale column studies were performed to investigate the adsorption performance of selected parameters. The PPhA increased the UV transmittance of leachate more than 4 times and outperformed CAC. Bed Depth Service Time and Yan models were used on the experimental data in order to estimate the maximum adsorption capacity and evaluate the characteristics of the fixed-bed. The PPhA equilibrium uptake of COD and TOC amounted to 5.7 mg/g and 0.9 mg/g, respectively. The postulated removal mechanism in environmentally relevant conditions (e.g., pH neutral) suggested a complex interaction between the biochar and organic macromolecules. Diluted phosphoric acid solution (0.01 mol/L) was successfully used for the column regeneration. Beside the UVQS, PPhA showed affinity towards toxic heavy metals (e.g., Pb, Ni, Co) pointing out the rich surface chemistry of the PPhA. Based on the obtained results and successfully implemented scale-up methodology, the low-cost PPhA adsorbent might effectively compete with the CAC as a highly efficient platform in wastewaters leachate processing.

Synthesis of Glue-Free NaA Zeolite Granules from Natural Kaolin for the Adsorption of Pb(II) Ions in Aqueous Solution Using a Fixed-Bed Column Study.

NaA zeolite-coated metakaolin granules (MKG@NaA) were successfully synthesized from kaolin mineral by primary growth in the hydrothermal reaction without using glue or a seed crystal. The XRD and SEM analysis results revealed that a layer of NaA zeolite with a typical cubic shape and high crystallinity formed on the surface of kaolin granules. The obtained material was used as an adsorbent for lead metal ion Pb(II) adsorption studies in a fixed-bed column configuration. The operation factors such as the solution inflow rate, Pb(II) concentration, and column height were investigated. The results showed that the adsorption capacity of the material increased with increasing column height and initial concentration of the influent and decreased with increasing flow rate. With the test parameters at the Pb(II) concentration of 100 mg·L–1, the adsorbent bed height of 8.1 cm, and the inflow rate of 2.5 mL·min–1, the lead ion adsorption capacity was 118.5 mg·g–1. The Thomas, Yoon–Nelson, and bed depth service time models were applied to describe the breakthrough curves for Pb(II) ion removal by a fix-bed column using the MKG@NaA absorbent and to predict the column performance under different experimental conditions with good linearity (R2 > 0.95).

Adsorptive removal of reactive green 5 (RG-5) and direct yellow 50 (DY-50) from simulated wastewater by Mangifera indica seed shell and its magnetic composite: Batch and Column study

Removal of reactive green (RG-5) and direct yellow (DY-50) dyes was carried out by native Mangifera indica (mango) seed shell biomass and its magnetic composites. After synthesis of adsorbents, surface properties of mango seed shell biomass (BN) and magnetic composites (BMc) were determined by TGA, FTIR and SEM In batch experimentation mode optimum conditions for RG-5 and DY-50 uptake were found as: contact time, 120 min and temperature 35°C, pH 7 and 2, for DY-50 uptake with both adsorbents BN and BMc respectively, in case of RG-5 the optimum temperatures were 60 and 25°C for BN and BMc respectively, optimum pH and contact time were same as DY-50. Effects of surfactants, metals and salts concentration on the biosorption capacity were also investigated. Kinetic studies showed the best fitness of pseudo-second-order kinetic model on experimental data. Langmuir showed best fitness for BMc as well as BN (RG-5) and BM for DY-50, while Temkin isotherm best fitted on BN data for DR-50, conversely Freundlich only supports the adsorption mechanism for RG-5 with BN. Thermodynamic study for RG and DY revealed the endothermic and stable biosorption onto BN and BMc. Column study parameters such as effect of bed height and concentration were investigated at constant flow rate. Kinetic models BDST (bed depth service time) and Thomas were applied on column experimental data. Outcome of this research work showed that the magnetic bio-composites prepared by mango seed shell biomass has a great potential to remove RG and DY dyes from wastewater.

Artificial neural network (ANN) approach for prediction and modeling of breakthrough curve analysis of fixed-bed adsorption of iron ions from aqueous solution by activated carbon from Limonia acidissima shell

Abstract 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.

Study on Reactive Blue Adsorption on Raw and Modified Wheat Straw Using Fixed-Bed Column

The intention of this study was to explore the efficiency and feasibility of adsorption of Reactive Blue dye (H3R) used in textile industries using Raw wheat straw (RWS) and Modified wheat straw (MWS) as a low-cost adsorbent. Wheat straw was modified using cationic surfactant (CTAB) to study the improvement of dye removal. The properties of Raw and Modified wheat straw are studied by means of Fourier transform infrared (FTIR) and scanning electron microscope (SEM) analyses to determine the functional groups and the nature of their surface. Continuous experiments were done by fixed-bed column to study the characteristics of the breakthrough curve using different bed heights and flow rates. Results showed that the breakthrough time increases with increasing bed height and decreasing flow rate, in turn results into higher removal capacity. Results also showed a higher flow rate lead a lower adsorption capacity due to insufficient residence time. Bed depth service time model (BDST), Adam-Bohart and Thomas models were used to predict the breakthrough curves and to determine the adsorption capacity of the column. The highest bed capacity of 12.95 and 32.2 mg/g for MWS was obtained using 10 mg/L, 10 cm bed height at 10 mL/min and 30 mL/min respectively.

Removal of hexavalent chromium by encapsulated chitosan-modified magnetic carbon nanotubes: Fixed-bed column study and modelling

A new type of composite adsorbent, encapsulated chitosan-modified magnetic carbon nanotubes (CS/MWCNTs/Fe) beads were used to remove hexavalent chromium (Cr(VI)) from aqueous solutions in a fixed-bed column. Among the various combination of operating parameters, we obtain a maximum volume of treated effluent (210 mL) under the following conditions: flow rate, 1 mL min−1; bed height, 8 cm; feed Cr(VI) concentration, 30 mg L−1; and solution pH, 4.0 ± 0.2. The corresponding adsorption capacity was 1.54 mg g-1 and the overall Cr(VI) removal efficiency was 54 %. In characterizing the dynamics of the adsorption process and breakthrough profiles, we found that the Thomas model and the Yoon-Nelson model both accurately described the breakthrough curves under all experimental conditions, while the Adams-Bohart model was applicable only for an early phase of dynamic behavior CtC0≤0.5 of the CS/MWCNTs/Fe beads column. Columns with shorter bed heights favored the global mass transfer rate, especially during the early breakthrough periods. Moreover, the bed depth service time (BDST) model was validated experimentally, enabling the prediction of service time of the adsorption bed at different outlet concentrations using hypothetical flow rates and inlet concentrations. Scaled-up study was performed to observe the column performance at higher throughputs. The high selectivity of Cr(VI) adsorption in the simulated wastewater in the presence of other heavy metals (copper and cadmium) and background anion (phosphate) suggests the applicability of CS/MWCNTs/Fe beads for Cr(VI) removal from industrial effluents.

Dynamic adsorption models and artificial neural network prediction of mercury adsorption by a dendrimer-grafted polyacrylonitrile fiber in fixed-bed column

In this paper, a dendrimer-grafted polyacrylonitrile fiber (PANF-TU) was successfully synthesized and characterized by scanning electron microscope with energy dispersive spectroscopy for removal of mercury. Adsorption feasibility was thoroughly studied during batch and dynamic tests. Adsorption kinetics, isotherms and effects of pH and coexisting substances were performed with the maximum adsorption capacity of 227 mg g−1. The better fitting characteristics of pseudo-second-order and Langmuir models revealed the dominant role of monolayer chemisorption during the adsorption process. Various variables in dynamic adsorption process were investigated and the results revealed the tendency of adsorption capacity increased with the decrease of inflow rate and the increase of bed depth and initial concentration, and reached a higher adsorption capacity under appropriate environmental conditions. Thomas, Bohart-Adams, Yoon-Nelson and bed depth service time models were applied to predict experimental data, exhibiting satisfactory fitting results. According to artificial neural network simulation, the relative importance of operation parameters was in the sequence of inflow duration > bed depth > flow rate > influent pH > initial concentration > influent temperature. Furthermore, the adsorption performance of PANF-TU kept well during five times regeneration, which indicated the adsorbent might be a promising material for remediation of Hg2+ polluted aqueous systems.

Study of the dynamic adsorption and the effect of the presence of different cations and anions on the adsorption of As(V) on GUT‐3

This study is aimed at understanding the dynamic adsorption and the effect of the presence of different cations and anions on the adsorption of As(V) on GUT‐3 (a new metal–organic framework). The study showed that Zn2+, Ni2+, Cu2+, CO32−, and NO3− promoted the adsorption of As(V) on GUT‐3 at all concentrations and Fe3+ and Cr3+ promoted the adsorption only at 0.5 and 2 mmol/L, respectively, and PO43− and SO42− at 0.5 mmol/L. Fe3+, Cr3+, PO43−, and SO42− inhibited the adsorption at other concentrations. And Zn2+, Ni2+, Cu2+, CO32−, and NO3 promote the adsorption of As(V) on GUT‐3. Fe3+ and Cr3+ at 0.5, 2 mmol/L promote the adsorption of As(V) on GUT‐3. PO43− and SO42− at 0.5 mmol/L promoted the adsorption of As(V) on GUT‐3, whereas PO43− and SO42− at other concentrations inhibited the adsorption of As(V) on GUT‐3. However, K+, irrespective of the concentration, was seen to inhibit the adsorption of As(V) on GUT‐3. The dynamic adsorption study showed that the penetration process of As(V) on GUT‐3 was more in line with the bed depth service time (BDST) model. Dynamic adsorption was mainly chemical in nature and was observed to occur on the surface of the adsorbent.

2-Mercaptobenzimidazole-functionalized chitosan for enhanced removal of methylene blue: Batch and column studies

Chitosan functionalized with 2-mercaptobenzimidazole (2-MBI) (i.e. 2-MBI@Chit) shows high sorption capacity (i.e., 1.28 mmol MB g−1) for methylene blue (MB) (at pH close to 9.3). Sorption is weakly decreased (by less than 25%) by high NaCl concentration (up to 45 g L−1). The sorption (slightly endothermic) is fitted by the Langmuir equation. The kinetic profile is fitted by the pseudo-first order rate equation (PFORE): equilibrium reached within 90 min of contact. The resistance to film diffusion is minimized when setting agitation speed at 200 rpm. Dye desorption is successfully achieved (up to 94.5%) using 0.8 M HCl; desorption kinetics is little slower than the sorption step. The loss in sorption capacity at the fifth sorption/desorption cycle does not exceed 5%. Yoon–Nelson, Bohart–Adams, and bed-depth service time equations are used for analyzing the breakthrough in fixed-bed columns. At the exhaustion of the column, the sorption capacity approaches the maximum sorption capacity in batch: all the reactive groups remain accessible in dynamic sorption mode. The dye is efficiently recovered from spiked seawater and the sorption performance is depreciated by less than 16% while comparing tap water and seawater under selected experimental conditions.

Removal of calcium ions from aqueous solution by bovine serum albumin (BSA)-modified nanofiber membrane: Dynamic adsorption performance and breakthrough analysis

The presence of calcium ion (Ca2+) in process streams has always been a challenge because of its impact to the heat transfer efficiency of process equipment. Polyacrylonitrile (PAN) nanofiber membrane was selected as the basic matrix in this study owing to its strong mechanical strength and chemical stability. Cation-exchange nanofiber membranes with different properties, namely weak ion exchanger (P−COOH), strong ion exchanger (P-SO3H) and amphoteric ion exchanger (P−COOH-BSA; coupled with bovine serum albumin) were synthesized via hydrolysis and coupling reactions. The physicochemical characteristics of these nanofiber membranes were investigated by Fourier-transform infrared spectroscopy, scanning electron microscope, and thermogravimetric analysis. Dynamic adsorption performance and breakthrough analysis of these nanofiber membranes were evaluated at different Ca2+ influent concentrations, flow rate, and configuration of membrane stacking. The maximal removal efficiency of Ca2+ (∼62 %, corresponding to dynamic binding capacity = ∼122 mg/g) was achieved by P−COOH-BSA at 500 mg/L of Ca2+ influent concentration, 2 mL/min of flow rate, and one-layer membrane configuration. Two commonly used mathematical models (Thomas and bed depth service time) were applied in the data fitting for the prediction of breakthrough curve and the determination of optimum operating parameters. The results indicate that the removal of Ca2+ by these nanofiber membranes was very effective due to the high interface mass transfer. In this work, Thomas model was found to be more suitable in elucidating the experimental result trends observed from the dynamic adsorption system.

Comprehensive batch and continuous methyl orange removal studies using surfactant modified chitosan-clinoptilolite composite

In the present study, the adsorption of methyl orange (MO) onto surfactant modified chitosan clinoptilolite composite (SMCSCL) from aqueous solution was investigated in batch and continuous adsorption systems. The characterization techniques of FTIR, FE-SEM, XRD, TGA and N2 adsorption–desorption were evaluated to find the functional group, morphology, crystalline structure, thermogravimetry and surface area of SMCSCL. The effect of process parameters including adsorbent dosage, contact time, solution pH and temperature on dye removal were studied in batch operation. Maximum dye adsorption at the optimum conditions was obtained as a loading of 0.22 g/20 mL, solution pH of 3.5, contact time of about 10 min and temperature of 30 °C. Thermodynamic studies showed that the adsorption process of MO onto SMCSCL was spontaneous, physical and unfavorable with the temperature rise. To evaluate kinetic data, the pseudo-second-order model showed a better correlation with the experimental data. The equilibrium data was in better agreement with the Toth isotherm model. Also, the Langmuir monolayer capacity was obtained 14.5 mg/g at the optimized operation parameters. The continuous adsorption experiments were carried out in the fixed-bed column and the operating conditions as influent flow rate (4.5–7.5 mL/min) and the bed depth (1–1.4 cm) on methyl orange adsorption. Maximum adsorption capacity in continuous experiments was obtained 32.09 mg/g at the influent flow rate of 4.5 mL/min and the bed depth of 1.4 cm. Thomas and Yoon-Nelson models provide the best description of the breakthrough curve and fixed-bed column hydrodynamic. Also, the bed depth service time (BDST) model can be practical to the prediction of breakthrough behavior and its scale-up. It was concluded that the adsorption of MO onto SMCSCL from aqueous solution in batch and continuous operation could be used effectively due to their applicability at the low-temperature range.