Bed Depth Service Time Model Research Articles

Batch and fixed-bed column study for p-nitrophenol, methylene blue, and U(VI) removal by polyvinyl alcohol-graphene oxide macroporous hydrogel bead.

There is an increasing need to explore effective and clean approaches for hazardous contamination removal from wastewaters. In this work, a novel bead adsorbent, polyvinyl alcohol-graphene oxide (PVA-GO) macroporous hydrogel bead was prepared as filter media for p-nitrophenol (PNP), dye methylene blue (MB), and heavy metal U(VI) removal from aqueous solution. Batch and fixed-bed column experiments were carried out to evaluate the adsorption capacities of PNP, MB, and U(VI) on this bead. From batch experiments, the maximum adsorption capacities of PNP, MB, and U(VI) reached 347.87, 422.90, and 327.55 mg/g. From the fixed-bed column experiments, the adsorption capacities of PNP, MB, and U(VI) decreased with initial concentration increasing from 100 to 400 mg/L. The adsorption capacities of PNP, MB, and U(VI) decreased with increasing flow rate. Also, the maximum adsorption capacity of PNP decreased as pH increased from 3 to 9, while MB and U(VI) presented opposite tendencies. Furthermore, the bed depth service Time (BDST) model showed good linear relationships for the three ions' adsorption processes in this fixed-bed column, which indicated that the BDST model effectively evaluated and optimized the adsorption process of PVA-GO macroporous hydrogel bead in fixed-bed columns for hazardous contaminant removal from wastewaters.

Adsorption dynamics of isopropanol in structured fixed bed with microfibrous ZSM-5 zeolite structured composite

Abstract The micro-fibrous ZSM-5 zeolite structured composite (ZSM-5/PSSF), prepared by combining wet lay-up paper-making with sintering technique followed by secondary growth process, was applied in isopropanol (IPA) adsorption dynamics in structured fixed bed. ZSM/PSSF was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) as well as N2 adsorption–desorption isotherm. Adsorption dynamics of isopropanol in structured fixed bed indicated a significant mass transfer enhancement. Bed pressure drop of structured packed bed decreased drastically attributed to excellent permeation nature of 3D network structure in paper-like stainless steel fiber (PSSF). Length of unused bed (LUB) reduced when ZSM-5/PSSF was packed in proper proportions. Breakthrough curves could be well fitted by both Yoon–Nelson and Bed depth service time (BDST) models, rate constant k′ and ka also confirmed enhancement of mass transfer. In conclusion, excellent mass transfer, low bed pressure drop and high utilization of bed made great contributions in improving adsorption performance of IPA in structured fixed bed.

Application of chitosan in removal of molybdate ions from contaminated water and groundwater

Water pollution by heavy metals represents a serious problem around the world. Among various treatment techniques for water remediation, adsorption is an effective and versatile method due to the low cost, effectiveness and simplicity. Chitosan is a cationic polysaccharide with an excellent adsorption capacity of heavy metal ions. Chitosan has a high molybdate adsorption capacity (265±1mgg−1) at 20°C and pH 2.7. Participation of hydroxyl groups in the adsorption of molybdate anions was confirmed by FT-IR analysis. SEM images showed that morphological surface changes happen after MoVI adsorption. Continuous adsorption data were best fitted by Modified Dose- Response model. Scale-up of continuous processes was achieved applying bed depth service time (BDST) model. Application of chitosan in molybdate removal from real groundwater samples suggest that this polysaccharide is a good option to be used for household purposes.

Mathematical modelling of Pb2+, Cu2+, Ni2+, Zn2+, Cr6+ and Cd2+ ions adsorption from a synthetic acid mine drainage onto chitosan derivative in a packed bed column

ABSTRACTStudies on the adsorption of toxic metal ions in batch mode using modified chitosan beads have been reported by several authors in literature; for large-scale operations, packed bed column studies are performed to generate data that are directly applicable in real wastewater treatment. In this work, the application potential of chitosan derivative for the uptake of Pb2+, Cu2+, Ni2+, Zn2+, Cr6+, and Cd2+ ions from aqueous solution in a packed bed adsorption column was investigated. On this note, the adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Scanning electron microscope (SEM); the effect of breakthrough parameters such as influent concentration, bed height, and feed flow rate was determined. The experimental data were fitted to mathematical column models, namely Bed Depth Service Time (BDST), Yoon-Nelson and Thomas model. The removal efficiency, breakthrough and exhaustion time increased with an increase in bed height but decreased with an increase in the flow rate and influent concentration. The mathematical models applied in this study were successful in describing experimental data. Desorption studies were performed with no loss in the mass of the beads, and the breakthrough and exhaustion time were found to be the same on reusing the beads.Abbreviations: Ch-b: chitosan coated bentonite; GXXB: grafted cross-linked chitosan beads; MMBB: multi metal binding biosorbent; PFOLG: panosized ferric oxide loaded glycidyl; MPSD: Marquardt’s percent standard deviation

Removal of Cr(VI) and Pb(II) from Wastewater by ZeoliteNaX in Fixed Bed Column

The ability of synthetic zeoliteNaX to remove Cr(VI) and Pb(II) from aqueous solutions was studied in fixed bed column. The effect of bed height (4, 6, 8 in.) and flow rate (0.825, 1.6, 2.14, 4.0, 5.0 L/h) was studied. The uptake and percentage removal of Cr(VI) Pb(II) and on zeoliteNaX for 4-in. column were found to be 5.66 and 8.896 mg/g and 84.99 and 89%, respectively. The bed depth service time (BDST) and Thomas model were used for the analysis of the column. The column experiments showed that the breakthrough time and the exhaustion time are found to increase with increase in bed height. Favorable results were obtained with the BDST model, which describe the experimental data well.

Modeling and analysis of a packed-bed column for the effective removal of zinc from aqueous solution using dual surface-modified biomass

ABSTRACTIn this research, ultrasonic-assisted fishtail palm Caryota urens seeds (UACUS) have been prepared for the effective removal of Zn(II) ions from aqueous solution in packed-bed column studies. The effect of various operating parameters such as bed depth, initial Zn(II) ions concentration and flow rate on breakthrough curves has been investigated. The dynamic response for the adsorption of Zn(II) ions onto UACUS was described in terms of the breakthrough curves. The results demonstrated that the maximum removal of Zn(II) ions was attained at a low flow rate, influent concentration and high bed depth. The results showed that breakthrough time and exhaustion time were increased with increase of bed height and decreased with increase of flow rate and initial Zn(II) ion concentration. The experimental column data were fitted with different mathematical models, namely Adams–Bohart, Yoon–Nelson and bed depth service time (BDST) models. Amongst the models, the BDST model agreed well with the experimental data. The adsorbent was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Environmental Scanning Electron Microscopy (ESEM), Energy Dispersive X-Ray Spectroscopy (EDX), and Thermogravimetric Analysis (TGA). The experimental results concluded that the prepared UACUS can be utilized as a potential and low-cost adsorbent for the removal of Zn(II) ions from the contaminated liquid.

Breakthrough curve modeling of graphene oxide aerogel packed fixed bed column for the removal of Cr(VI) from water

The extensive investigation was conducted on the performance of the laboratory-scale fixed-bed column containing graphene/polylysine aerogel as an adsorbent for the removal of Cr(VI). The effect of important column design parameters on the performance of the column bed was investigated. High bed height, low influent flow rate, and high influent Cr(VI) concentration were found to be the better condition for the adsorption of Cr(VI). The effect of column bed height on the breakthrough was analyzed using bed depth service time (BDST) model and predicted the critical bed height 0.37 and 1.0cm at flow rates 1.66 and 3.32mL/min respectively for the Cr(VI). The Thomas and Yoon-Nelson model were found suitable for describing the breakthrough behavior of the column. The regeneration of exhausted column bed was studied for three cycles of adsorption-desorption. The calculation of life factor suggested that the column bed can avoid the breakthrough time at t=0 for 7.5 cycles whereas, the uptake capacity would be zero after 9.12 cycles of adsorption-desorption.

Breakthrough modeling and experimental design for o-xylene dynamic adsorption onto clay material.

The adsorption of o-xylene onto raw clay material in a fixed bed using a thermal conductivity detector gas chromatography was investigated. Experimental and theoretical studies were established to evaluate the removal efficiency of o-xylene by adsorption on clay materials and to predict kinetic parameters. Column data were describing at different conditions using Bohart-Adams, Wolborska, Thomas, Yoon and Nelson, dose-response, and bed depth service time models. All used models were satisfactory to predict the breakthrough curves. A suitable advection-dispersion-sorption (ADS) model has been also developed to simulate the measured data, based on the nature of the various equilibrium relationships of solid-gas and diverse descriptions of the mass transfer processes within of the adsorbent particle. The experiments can be fitted with high correlated coefficient R 2=0.996.

Study of transient behaviour of modified Soxhlet apparatus for extraction of a bio-fuel oil from Crotalaria juncea seed

ABSTRACTExtraction of Crotalaria juncea (Sunn hemp) oil from its seeds is important to study because of its proven promising clean fuel characteristics. Soxhlet-based solvent extraction with some modification has been tried to extract the oil. In a fluid-solid mass transfer system, where, solids are present as packed bed, dynamic behavior of bed can be described in terms of concentration of solute in solids/solvent-time profile. Some of the well-known semi-empirical models of adsorption dynamics are modified and applied since leaching of oil is just the reverse of the phenomenon of adsorption in porous media. Modified Bohart-Adams model (non-linear), modified Bed Depth Service Time (BDST) (linear), and modified Thomas model (non-linear forms) are applied. It is found that these models fit to the experimental result reasonably well. Results suggest that higher bed height, with proper shape (annular) of the bed, having a higher solvent velocity will work best. Comparing the error values (SSE, SAE, and ARE) in the four cases, it is very clear that the modified BDST model is the most suitable. In the light of transient study it is established that the modified Soxhlet apparatus with cylindrical and annular beds, performs best while leaching Crotalaria juncea oil from their seeds.

Synthesis of nano-γ-Al2O3/chitosan beads (AlCBs) and continuous heavy metals removal from liquid solution

In this work, synthesis of chitosan beads impregnated with nano-γ-Al2O3 (AlCB) was carried out. The characteristics of the synthesized adsorbent were obtained by using Brunauer Emmett and Teller technique and Scanning Electron Microscopy method. The use of AlCB in continuous removal of chromium, lead, nickel and cadmium ions from liquid solution was studied using fixed-bed column system. Bed depths and flow rate effects on breakthrough and uptake capacity of the adsorbent in column were also examined. Dynamic parameters of the adsorption were calculated by using bed depth service time (BDST) and Thomas models. In both models, the data were analyzed by error analyzing and combining the values of determined coefficient (R 2) from regression analysis. The adsorption capacities of AlCB in breakthrough were 158.33, 183.33, 63.33 and 31.67 mg/g for chromium, lead, nickel and cadmium, respectively. In addition, BDST model was found to be an acceptable kinetic model to describe the experimental data.

Batch versus column modes for the adsorption of radioactive metal onto rice husk waste: conditions optimization through response surface methodology.

Batch and column adsorption modes were compared for the adsorption of U(VI) ions using rice husk waste biomass (RHWB). Response surface methodology was employed for the optimization of process variables, i.e., (pH (A), adsorbent dose (B), initial ion concentration (C)) in batch mode. The B, C and C2 affected the U(VI) adsorption significantly in batch mode. The developed quadratic model was found to be validated on the basis of regression coefficient as well as analysis of variance. The predicted and actual values were found to be correlated well, with negligible residual value, and B, C and C2 were significant terms. The column study was performed considering bed height, flow rate and initial metal ion concentration, and adsorption efficiency was evaluated through breakthrough curves and bed depth service time and Thomas models. Adsorption was found to be dependent on bed height and initial U(VI) ion concentration, and flow rate decreased the adsorption capacity. Thomas models fitted well to the U(VI) adsorption onto RHWB. Results revealed that RHWB has potential to remove U(VI) ions and batch adsorption was found to be efficient versus column mode.

Modelling of fixed bed column containing graphene oxide decorated by MgO nanocubes as adsorbent for Lead(II) removal from water

This study deals with the removal of Pb(II) ion from the aqueous solution using graphene oxide decorated by MgO nanocubes (GOMO) as an adsorbent. The nanohybrid was prepared by simple precipitation method and characterized by FTIR, XPS, XRD SEM and EDX analysis. A continuous up flow fixed-bed column study was performed utilizing the GOMO nanohybrid for field applicability by varying the column parameter such as bed height, flow rate and initial metal ion concentration. The maximum adsorption capacity of the GOMO nanohybrid was 187.9mg/g at an initial lead concentration of 80mg/L, bed height of 7.5cm, and flow rate of 1.66mL/min at pH 6.5. The breakthrough curves obtained were analyzed with different models i.e. Bed Depth Service Time (BDST), Thomas and Yoon–Nelson. The high R2 values obtained for the BDST model revealed its applicability for this system. Desorption of Pb2+ ions on GOMO was performed with 0.1M HCl solution, and the adsorbent found to retain its high adsorption up to three cycles. Life factor calculation indicated that adsorbent bed would have sufficient capacity to avoid breakthrough at time t=0 up to 6.7 cycles and the bed would be completely exhausted after 17.3 cycles.

Evaluation of kinetic and statistical models for predicting breakthrough curves of phosphate removal using dolochar-packed columns

The sustainability in utilizing dolochar packed columns under dynamic conditions for phosphate removal from aqueous solutions, has been carried out in this study. The assessment of efficacy of the bed under varying experimental conditions of bed depth, flow rate and influent phosphate concentration revealed that, an increase in bed depth and initial phosphate concentration or a decrease in flow rate resulted in increased breakthrough and exhaustion time. Thomas, modified dose response (MDR) and Clark models were applied to simulate the experimental breakthrough curves following nonlinear regression analysis. Also bed depth service time (BDST) model was engaged to scale up the adsorption process by means of linear regression approach. All the models with a very high coefficient of correlation (R2>0.93) predicted the breakthrough curves equally well. Good consistency was observed among experimental bed adsorption capacity (8.56mgg−1) and those predicted by Thomas (9.21mgg−1) and MDR models (8.81mgg−1). Statistical modeling proposed quadratic models for breakthrough and exhaustion time, with R2 values of 0.99 in both the cases. Soil column analytical test confirms slow release of phosphate from spent dolochar. The results confirm the sustainable application of dolochar packed columns for phosphate abatement in large scale accompanied by the utilization of spent dolochar as a source of phosphate.

Removal of Organic Pollutants from Industrial Cleaning Wastewaters Using a Combined Sedimentation and Packed-bed Column Treatment

In the present study, organic removal from five industrial cleaning wastewaters generated at a wood-laminate floor industry in Sweden was evaluated using a combined treatment process including sedimentation and a packed-bed column of commercial wood-based activated carbon (WAC). The supernatant obtained from the sedimentation was diluted with tap water until the COD concentration was reached 5 000 mg/L and it was continuously fed through the column by up-flow mode at a constant flow rate of 6 mL/min. The WAC performance at different bed height of 19, 38 and 57 cm was studied. The results showed that the sedimentation process removed about 20%, 24% and 24% of COD, TOC and BOD, respectively and the WAC column was effective in removing COD from the water phase. The treated wastewater volume and service time increased with the bed height increase. The column could treat 19 L of wastewater with the service time of 63.3 h and 30% breakthrough point. The experimental data fitted well with the bed depth-service time (BDTS) model. The increase of wastewater load on solid phase from 20%, 30%, 40% and 50% showed an increase of sorption capacity (No) and decrease of the rate constant (k).

Potential demonstrations of “hot spots” presence by adsorption-desorption of toluene vapor onto granular activated carbon under microwave radiation

Differences of adsorption-desorption process between microwave irradiation and conductive heating were studied to prove potential possibility of “hot spots” presence. Breakthrough curves of toluene vapor were recorded at different initial conditions. The results show that the time required to reach equilibrium (te) is shortened by 6–15% and adsorption capacity (N(exp)) is reduced by 6–13% at various constant conditions under microwave heating. Yoon-Nelson and Bed Depth Service Time models were applied to analyze adsorption process. Values of kY calculated by Yoon-Nelson model under microwave radiation are larger by 2–36%, while values of N0 determined by BDST model are smaller by 7–12%. Langmuir, Freundlich and Sips models were used to fit equilibrium data and describe adsorption isotherms. Values of qm and qs obtained from Langmuir and Sips models under microwave heating are smaller than that under conductive heating. Moreover, heat of adsorption calculated from Clausius-Clapeyron equation under microwave radiation are also lower. It is found that the desorption rate under microwave radiation is faster and SBET and VT obtained after desorption process are larger. Differences of adsorption-desorption process between microwave and conductive heating can be explained by the presence of the “hot spots” induced by microwave radiation that the temperature of some microstructures of surface regions is much higher than the overall temperature.

Fixed-bed adsorption of Tricaine Methanesulfonate onto pyrolysed paper mill sludge

The removal of Tricaine Methanesulfonate from water in a fixed-bed column packed with pyrolysed paper mill sludge was evaluated for application in Recirculating Aquaculture Systems. Breakthrough adsorption curves were determined for this pharmaceutical, under different operating conditions. In a laboratory-scale approach, with synthetic effluent, a bed adsorption capacity of 125mgg−1 was obtained under a flux of 56Lmin−1m−2, with 400mgL−1 of MS-222 with 4.5cm bed depth. The performance of the continuous adsorption in a column packed with biological paper mill sludge-based carbon, using real aquaculture wastewater as matrix, was not significantly affected. Then, scale-up was carried out and the bed depth service time model was applied and provided good predictions. Finally, the thermal regeneration of the exhausted adsorbent was assessed, which revealed satisfactory results for one cycle reusability after saturation; however, considering the nature of its precursor, the use of new adsorbent could be more profitable than its regeneration, functioning also as an additional option for the management of such wastes.

Study of a fixed-bed column in the adsorption of an azo dye from an aqueous medium using a chitosan–glutaraldehyde biosorbent

A continuous adsorption study in a fixed-bed column was carried out using a chitosan–glutaraldehyde biosorbent for the removal of the textile dye Direct Blue 71 from an aqueous solution. The biosorbent was prepared from shrimp shells and characterized by scanning electron microscopy, X-ray diffraction, and nuclear magnetic resonance spectroscopy. The effects of chitosan–glutaraldehyde bed height (3–12 cm), inlet Direct Blue 71 concentration (15–50 mg l−1), and feed flow rate (1–3 ml min−1) on the column performance were analyzed. The highest bed capacity of 343.59 mg Direct Blue 71 per gram of chitosan–glutaraldehyde adsorbent was obtained using 1 ml min−1 flow rate, 50 mg l−1 inlet Direct Blue 71 concentration, and 3 cm bed height. The breakthrough curve was analyzed using the Adams–Bohart, Thomas, and bed depth service time mathematical models. The behaviors of the breakthrough curves were defined by the Thomas model at different conditions. The bed depth service time model showed good agreement with the experimental data, and the high values of correlation coefficients (R2 ≥ 0.9646) obtained indicate the validity of the bed depth service time model for the present column system.

Removal of heavy metals from acid mine drainage using chicken eggshells in column mode

Chicken eggshells (ES) as alkaline sorbent were immobilized in a fixed bed to remove typical heavy metals from acid mine drainage (AMD). The obtained breakthrough curves showed that the breakthrough time increased with increasing bed height, but decreased with increasing flow rate and increasing particle size. The Thomas model and bed depth service time model could accurately predict the bed dynamic behavior. At a bed height of 10 cm, a flow rate of 10 mL/min, and with ES particle sizes of 0.18–0.425 mm, for a multi-component heavy metal solution containing Cd2+, Pb2+ and Cu2+, the ES capacities were found to be 1.57, 146.44 and 387.51 mg/g, respectively. The acidity of AMD effluent clearly decreased. The ES fixed-bed showed the highest removal efficiency for Pb with a better adsorption potential. Because of the high concentration in AMD and high removal efficiency in ES fixed-bed of iron ions, iron floccules (Fe2(OH)2CO3) formed and obstructed the bed to develop the overall effectiveness. The removal process was dominated by precipitation under the alkaline reaction of ES, and the co-precipitation of heavy metals with iron ions. The findings of this work will aid in guiding and optimizing pilot-scale application of ES to AMD treatment.

ADSORPTION OF FLUORIDE FROM INDUSTRIAL WASTEWATER IN FIXED BED COLUMN USING JAVA PLUM (SYZYGIUM CUMINI)

ABSTRACTObjective: The quality of drinking water is important for public safety and quality of life. Thus, providing every person on earth safe drinking waterseems to be the biggest challenge in front of mankind. For this purpose, here we have investigated the fluoride removal capacity of java plum.Methods: In this study, removal of fluoride from industrial wastewater using fixed-bed reactor adsorption techniques by java plum seed (Syzygiumcumini) was investigated. Fixed-bed column experiments were carried out for different bed depths, influent fluoride concentrations, and various flowrates. The Thomas model and bed depth service time model were applied to the experimental results. Both model predictions verify the experimentaldata for all the process parameters studied, indicating that the models were suitable for java plum (S. cumini) seeds (Biosorbent) fix-bed columndesign.Results: The empty bed residence time (EBRT) model optimizes the EBRT, and the Thomas model showed that the adsorption capacity is stronglydependent on the flow rate, initial fluoride concentration, and bed depth and is greater under conditions of a lower concentration of fluoride, lowerflow rate, and higher bed depth.Conclusion: The experimental results were encouraging and indicate that java plum (S. cumini) seed is a feasible option to use as a biosorbent toremove fluoride in a fixed bed adsorption process.Keywords: Adsorption, Column experiment, Thomas model, Empty bed residence time, Java plum.

Removal of molybdate anions from contaminated waters by brown algae biomass in batch and continuous processes

AbstractBACKGROUNDIn recent years, the discharge of heavy metal ions in natural waters has become a serious problem. Among the various techniques that have been employed for heavy metal removal, adsorption is highly effective and economical because low‐cost adsorbents can be employed. Brown algae are a potential biosorbent because of their high uptake capacities for various heavy metal ions. Petalonia fascia biomass immobilized in an agar matrix was tested as a new removal agent of MoVI from contaminated waters.RESULTSSorption studies were performed in batch and continuous systems. Petalonia fascia has a high adsorption capacity (1376 ± 2 mg g−1) at 20 °C and pH 1.0. Participation of hydroxyl and carboxylate functional groups in the adsorption of molybdate anions was confirmed by FT‐IR analysis. SEM images showed that morphological surface changes happen after MoVI sorption. Mean free energies of sorption and activation parameters demonstrate that the sorption mechanism was chemical sorption. MoVI sorption onto brown seaweed surface was spontaneous and exothermic. Petalonia fascia has an energetically heterogeneous surface. Continuous sorption data were best fitted by a modified dose–response model. Scale‐up of the sorption processes was achieved applying a bed depth service time (BDST) model. The critical bed depth, Z0 was 1.7 cm.CONCLUSIONSPetalonia fascia biomass is a good adsorbent material for MoVI and it can be used in fixed bed columns for the purification of MoVI contaminated effluents. The high value of qmax and the low cost of this seaweed make this biomass a good sorbent for use in continuous treatment of groundwater and effluents contaminated with molybdate anions. © 2016 Society of Chemical Industry