Column Breakthrough Curves Research Articles

Purification of acidic wastewater containing Cd(II) using a red mud-loess mixture: Column test, breakthrough curve, and speciation of Cd.

In this study, the safety of a red mud-loess mixture (RM-L) for the remediation of groundwater polluted by acid mine drainage (AMD) containing Cd(II) in mining areas was systematically analyzed and clarified. The effects of the initial concentration, flow rate, and packing height on the breakthrough performance and longevity of RM-L as a permeable reactive barrier (PRB) packing material were explored by column tests. The results show that the breakthrough time, saturation time, and adsorption capacity of Cd(II) in RM-L increased with decreasing initial concentration and flow rate, as well as increasing packing height. Moreover, RM-L had a long-term effective acid buffering capacity for acidic wastewater containing Cd(II). An increase in the packing height led to a longer longevity of the PRB than the theoretical value. In addition, the speciation of Cd on RM-L was dominated by carbonate form and iron-manganese oxide form. The surface of the RM-L particles evolved from a dense lamellar structure to small globular clusters after purifying the acidic wastewater containing Cd(II), due to the corrosion of H+ and the reoccupation and coverage by increasingly enriched adsorbates and precipitates of heavy metal ions.

Successful removal of fluoride from aqueous environment using Al(OH)3@AC: column studies and breakthrough curve modeling.

In this study, we discuss the removal of fluoride from water through column adsorption methods using Al(OH)3@AC as a functional granular activated carbon. The height of the bed, fluoride concentration, and flow rate are the experimental factors used to obtain the breakthrough curves. As the flow rate increased, the breakthrough and saturation times decreased. The analysis of simplified column models, such as the Adams-Bohart, Thomas, and Yoon-Nelson models, revealed that the Clark model best described the adsorption process when fitting the experimental data. The obtained breakthrough curves agreed with the corresponding experimental data. The highest capacity for adsorption obtained during the column procedure was found to be 41.84 mg g-1 with a bed height of 3 cm, an initial fluoride concentration of 10 mg L-1 and a flow rate of 7.5 mL min-1.

A novel machine learning framework for predicting biogas desulfurization breakthrough curves in a fixed bed adsorption column

The corrosive and toxic hydrogen sulfide (H2S) in biogas is a pressing concern for researchers, spurring the development of predictive models for breakthrough curves in fixed-bed adsorption columns. This study utilizes Machine Learning (ML) to predict biochar H2S adsorption model parameters and establishes novel connections between contributing features and these parameters. The ML models could predict the process BC with an R2 score higher than 0.8 in 75 % of cases in the testing sets. A comprehensive features importance analysis reveals that Biochar's pH is the most influential factor, positively correlating with BC parameters and enabling more efficient H2S removal followed by H2S concentration, H/C molar ratio, and particle size. Understanding these relationships offers practical guidance for improving biogas purification, making this study valuable in addressing the H2S challenges and showcasing the potential of ML in predicting BC in fixed bed adsorption columns, providing a foundation for enhancing the adsorption process.

Enhancing biochar structure and removal efficiency of ammonium and microalgae in wastewater treatment through combined biological and thermal treatments

This study explored the efficiency of biological pre-treatment combined with thermal treatment to produce biochars, called E-biochars, for the removal of ammonium and microalgae without using chemical pre-treatment. The aim was to develop an environmentally sustainable approach for large-scale biochar production with high efficiency in wastewater treatment. The biological pre-treatment involved incubating the sawdust with Bacillus subtilis for 14 to 20 days and then subjected to pre-treatment at low temperatures (250-350 °C). This process broke down cellulose and altered its lignocellulosic structure, improving the biochar's morphology by leading to a more anisotropic pore structure. The thermal pre-treatment after that will help to open a broader range of pore sizes, spanning from macropores to micro-pores in the 1 μm to 5 μm dimension range. These alterations facilitated the efficient removal of ammonium and microalgae during adsorption experiments. The findings fit the Langmuir and the Freundlich models, according to the isotherm test of NH4+ and microalgae (R2 = 0.92÷0.99). The E-biochar termed EBH20, composted with Bacillus subtilis for 20 days at 350 °C, performed best, with Qmax equal to 40.2 mg/ g NH4+ under neutral conditions (pH = 7). Interestingly, the co-occurrence of ammonium and microalgae enhanced the removal of these contaminants. The interaction between microalgae cells and ammonium facilitated ammonium adsorption onto biochar and microalgae. The column breakthrough curves under NH4+ and NH4+ mixed microalgae adsorption were predicted using the Thomas model with the high agreement (R2 = 0.91÷0.99) for ammonium but for algae between prediction and running experimental column data.

Fixed bed column experiments using cotton gin waste and walnut shells-derived biochar as low-cost solutions to removing pharmaceuticals from aqueous solutions

Acetaminophen (ACT), sulfapyridine (SPY), ibuprofen (IBP) and docusate (DCT) are pharmaceuticals with widespread usage that experience incomplete removal in wastewater treatment systems. While further removal of these pharmaceuticals from wastewater effluent is desired prior to beneficial reuse, additional treatment technologies are often expensive and energy intensive. This study evaluated the ability of biochar produced from cotton gin waste (CG700) and walnut shells (WS800) to remove four pharmaceuticals (ACT, SPY, IBP, and DCT) from aqueous solution. Physico-chemical properties of the biochars were characterized by Brunauer-Emmett-Teller (BET) analysis, scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and zeta potential. The increased pyrolysis temperature during the production of WS800 led to an increase in the specific surface area and increased dehydration of the biochar represented by the loss of the OH-group. Fixed-bed column experiments were performed to determine the difference in removal efficiency between the biochars and elucidate the effects of biochar properties on the adsorption capacity for the pharmaceuticals of interest. Results showed that CG700 had a greater affinity for removing DCT (99%) and IBP (50%), while WS800 removed 72% of SPY and 68% of ACT after 24 h. Adsorption was influenced by the solution pH, surface area, net charge, and functional groups of the biochars. The mechanisms for removal included pore filling and diffusion, hydrophobic interactions, hydrogen bonding, and π-π electron donor acceptor interactions. To conduct predictive modeling of the column breakthrough curves, the Thomas, Adams-Bohart, and Yoon-Nelson models were applied to the experimental data. Results demonstrated that these models generally provided a poor fit for the description of asymmetrical breakthrough curves. Overall, the results demonstrate that biochars from cotton gin waste and walnut shells could be used as cost-effective, environmentally friendly alternatives to activated carbon for the removal of pharmaceuticals from aqueous solutions.

Phosphorus removal from wastewater using Ca-modified attapulgite: Fixed-bed column performance and breakthrough curves analysis

The adsorbent calcium-modified attapulgite (Ca-GAT) prepared by calcium chloride modification and high temperature treatment (700 °C) has proved to remove phosphorus in low-concentration phosphorus wastewater in batch adsorption experiments. Dynamic adsorption performance and industrial application potential still need further determination. This study explored the effects of various parameters on the dynamic phosphorus adsorption, including initial phosphate concentration (2–10 mg/L), flow rate (1–3 mL/min) and adsorption bed height (2–6 cm). Phosphorus adsorption ability improved and the breakthrough time increased with the increase of bed height, flow rate, and a decrease in initial phosphorus concentration. Breakthrough curves fitted four models, the Adams-Bohart, Thomas, Yoon-Nelson and Bed depth service time (BDST). The maximum adsorption amount determined by the Thomas model obtained 13.477 mg/g. The saturated fixed-bed column were regenerated with NaOH, NaOH + NaCl and HCl, among which 0.5 mol/L NaOH had the best regeneration effect. During the utilization of a large fixed-bed to treat the actual membrane bioreactor (MBR) effluent, the breakthrough point (0.5 mg/L) was obtained after 177 h. These results implied that Ca-GAT had an application potential for the treatment of low-concentration phosphorus wastewater (2 mg/L).

Nickel removal by biogenic selenium nanoparticles (SeNPs): Characterization and simulation of non-symmetric breakthrough curves in continuous-flow packed-bed columns

Nanoparticles offer an alternative mean for heavy metals removal from aquatic environment. In this work we study the sequestering of nickel by biogenic selenium nanoparticles (SeNPs) both in native and in immobilized form in alginate matrix (alginate-SeNPs). The apparent sorption like process is attributed to the coordination chemistry of Ni with the functional groups of the extracellular polymeric substances (EPS) covering the SeNPs. The kinetics and the equilibrium of the process are presented, while the morphology and the properties of the adsorption beads are studied by SEM, FTIR and rheological analysis. Langmuir isotherm describes the adsorption equilibrium with maximum loading Q0 29.411 mg Ni/g SeNPs and 0.651 mg Ni/g alginate-SeNPs. The adsorption of nickel is fast and equilibrium is attained within one hour. Continuous flow experiments in packed beds reveal early elution patterns and non-symmetric sigmoidal profiles due to the reduced adsorption capacity of the immobilized SeNPs, the short depth of the beds and the apparent non-uniform flow pattern. The Bohart-Adams equation fits adequately the main sigmoidal part of the breakthrough curves, however fails to predict the early breakthrough data. By using the advection–dispersion-reaction equation (ADR) under two novel aspects: (a) the rapid equilibrium model with the introduction of an efficiency coefficient accounting for all the kinetic and sorption limitations and (b) the split flow model accounting for any non-uniform flow conditions in the column, the model accuracy is significantly improved. Repeated sorption–desorption experiments show that alginate-SeNPs retain 59% of the original adsorption capacity even after eight cycles.

Simultaneous removal of Pb and MTBE by mixed zeolites in fixed-bed column tests

The co-contamination of metals and organic pollutants, such as Pb and methyl tert-butyl ether (MTBE), in groundwater, has become a common and major phenomenon in many contaminated sites. This study evaluated the feasibility of their simultaneous removal with permeable reactive barrier (PRB) packed with mixed zeolites (clinoptilolite and ZSM-5) using fixed-bed column tests and breakthrough curve modeling. The effect of grain size on the permeability of PRB and removal efficacy was also assessed by granular and power clinoptilolite. The replacement of granular clinoptilolite by powder clinoptilolite largely reduced the breakthrough time but increased the saturation time nearly fourfold. The column adsorption capacity of clinoptilolite powders almost tripled that of clinoptilolite granules (130.6 mg/g versus 45.3 mg/g) due to higher specific surface areas. The minimum thickness and corresponding longevity of PRB were calculated as 7.12 cm and 321.5 min when 5% of granular clinoptilolite was mixed with 5% ZSM-5 and 90% sand as mixed PRB reactive media compared with 10.86 cm and 1230.2 min for the application of powder clinoptilolite. This study is expected to provide theoretical support and guidance for the practical application of mixed adsorbents in PRBs.

A new approach for scaling up fixed-bed adsorption columns for aqueous systems: A case of antibiotic removal on natural adsorbent

The scaling up of adsorption columns is a crucial step toward the removal of emerging pollutants from domestic and industrial wastewaters. In this study, a fixed-bed column to remove sulfamethoxazole packed with sugarcane bagasse was scaled up from laboratory (DL = 2.2 cm) to pilot unit (DP = 4.4 cm) using a scaling factor (K = 2). In addition to the basic similarity rules for scaling, three new criteria were proposed for the mass adsorbent, flow rate, and bed volume. Then, three lab-scale tests at flow rate of 5 mL/min and bed heights of 15, 25, and 35 cm were transferred to the pilot-scale column at flow rate of 20 mL/min and bed heights of 30, 50, and 70 cm, respectively. The breakthrough curves and the fixed-bed parameters (residence time tR, saturation time ts, adsorption capacity qe, volume of solution treated Vef, and removal percentage %R) obtained in both scales were compared to define their effect with the increase of scale. Finally, a mechanistic model was proposed to predict the breakthrough curves in both columns. The results exhibited that the breakthrough curves in the pilot-scale prolonged in time with higher breakthrough and saturation times than the laboratory breakthrough data. Additionally, tR, ts, and Vef changed in function of the K value used: ts and tR doubled their value in the pilot column or tRP=KtRL; Vef was eight times higher in the pilot column than the lab-column or VefP=K3VefL; qe and %R remained constant in both scales; these results were corroborated with the predicted breakthrough curves. Besides, the mechanistic model predicted with great precision the breakthrough data in both scales (R2>0.9), which means that the model can be used confidently for scaling up purposes. This study demonstrated new criteria which can be easily applied to scale up adsorption columns whit results that showed a correlation between both scales.

Nickel Adsorption by Biogenic Selenium Nanoparticles (Senps): Characterization and Simulation of Non-Symmetric Breakthrough Curves in Continuous-Flow Packed-Bed Columns

Nickel Adsorption by Biogenic Selenium Nanoparticles (Senps): Characterization and Simulation of Non-Symmetric Breakthrough Curves in Continuous-Flow Packed-Bed Columns

Evaluation of fluoride adsorption in solution by synthetic Al2 O3 /CeO2 : A fixed-bed column study.

A highly efficient fluoride adsorbent Al2 O3 /CeO2 was synthesized in this work and used it to fluoride removal in the fixed-bed adsorption through changing the different experimental conditions (influent F- concentration, flow velocity, and bed heights). The adsorption capacity was 9.72 mg/g. In addition, the Adams-Bohart and Thomas models were used to fit and evaluate the column breakthrough curve of fluoride removal process by Al2 O3 /CeO2 , and the correlation coefficients (R2 ) of the Thomas model were close to 1 under all experimental conditions. The structure of Al2 O3 /CeO2 and the adsorption mechanism were confirmed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), N2 adsorption and desorption isotherm, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Moreover, the adsorption of fluoride (F- ) was mainly through metal binding (MF) and hydroxyl binding (AlOH⋯F) on the surface of the Al2 O3 /CeO2 . Furthermore, the regeneration and coexisting anions studies of Al2 O3 /CeO2 were carried out, and the efficiency of adsorption was still above 70% after five cycles. PRACTITIONER POINTS: Removal of fluoride was studied by fixed-bed experiment, and the adsorption capacity of composite Al2 O3 /CeO2 was 9.72 mg/g. The metal complex played important role in fluoride removal and reusability makes a long-term application for fluoride adsorption. Fluoride wastewater is pumped to the fixed-bed column, and fluoride ions are absorbed by Al2 O3 /CeO2 through fluoride metal complex and aluminum hydrofluoride.

Application of raw peach stones for hexavalent chromium removal from aqueous solution using column system

Raw biosorbent waste is a cheap and environmentally friendly material that provides good cost-benefit for the industries that use it. The objective of this study is to improve the feasibility of raw local peach stones (RPS) waste for the removal of hexavalent chromium from aqueous solution using column system. The characterization of the adsorbent (RPS) was done by using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The impact of various parameters such as flow rate (1.5,3 and 5 ml/min) and height bed (1,2 and 3 cm) on Cr(VI) adsorption onto RPS were investigated. Two models were proposed to illustrate column breakthrough curve obtained at different flow rates and bed heights. The obtained experimental results showed a better adsorption efficiency at a low flow rate (1.5 ml/min) and a bed height of 3cm. Thus this work provides the high potential of raw peach stones (RPS) for the removal of Cr(VI) ions from aqueous solution.

Nickel Adsorption by Biogenic Selenium Nanoparticles (Senps): Characterization and Simulation of Non-Symmetric Breakthrough Curves in Continuous-Flow Packed-Bed Columns

Nickel Adsorption by Biogenic Selenium Nanoparticles (Senps): Characterization and Simulation of Non-Symmetric Breakthrough Curves in Continuous-Flow Packed-Bed Columns

Relationship between HETP measurements and breakthrough curves in short chromatography columns.

An analysis of the relationship between the number of plates measured with a small molecule tracer and the breakthrough curve of a strongly bound protein in short laboratory chromatography columns (1-5 cm) considering flow nonuniformity is presented. For practical conditions, while axial dispersion has only a small impact on the breakthrough curve, radial flow nonuniformity has a profound effect. Radial parabolic velocity profiles lead to tailing tracer peaks and broader breakthrough curves. Profiles where the velocity varies radially only in a thin region near the column wall lead to fronting tracer peaks and early breakthrough when the velocity at the wall is higher than the average and to tailing peaks and tailing breakthrough curves when the velocity at the wall is lower than the average. Experiments conducted in laboratory minicolumns (0.5-1 cm diameter, 0.5-1 ml volume) show tracer peaks and protein breakthrough curves that are consistent with higher velocities at the wall. The model presented in this work provides a tool to model experimental breakthrough data and to assess the degree of flow uniformity required to obtain meaningful dynamic binding capacity measurements using minicolumns in a high-throughput lab setting.

Novel combinatorial extensions to breakthrough curve modeling of an adsorption column — Depth filtration hybrid process

This work introduces novel scenarios for the breakthrough curve modeling of an adsorption column/depth filtration hybrid system. Four well-known theoretical breakthrough models including Thomas, Adams–Bohart, Yoon–Nelson, and BDST were employed to describe the normalized concentration profiles. In the first approach, the theoretical models were combined for better estimation of the breakthrough curves and the Thomas/Yoon–Nelson and Thomas/BDST combinations were obtained as the best extensions. In the second approach, an adsorption-transport model was developed for the depth filter to obtain the transient concentration gradient across the filter medium thickness. The model was then combined with the theoretical breakthrough models to predict the adsorption column breakthrough curves. Results revealed that a decrease in the feed flowrate and filter pore size could intensify the concentration polarization on the filter surface. Both model extensions could successfully approximate the breakthrough curves of the hybrid system with more than 99% agreement with the experimental data, while the prediction accuracy of the original breakthrough models seldom exceeds 93%.

Achieving low-cost, highly selective nitrate removal with standard anion exchange resin by tuning recycled brine composition

This study demonstrated the presence of a critical equivalent ratio of the competing anion (i.e., sulfate and bicarbonate) to chloride ion in recycled brine to achieve highly-selective nitrate removal from nitrate-rich groundwater in the standard-anion exchange resin (AER) (i.e., with trimethylamine functional groups) column process. With increasing bicarbonate (or sulfate):chloride equivalent ratio in brine used to circularly activate/regenerate the standard-AER column, considerable bicarbonate (sulfate) removal and dumping were observed. The critical bicarbonate (sulfate):chloride equivalent ratio of 2:5 (8:1) in brine effectively achieved zero net bicarbonate (sulfate) removal (<5%) from feedwater during long-term exhaustion–regeneration cyclic operation. The feed rate (6–18 BV/h) played a key role in determining the critical sulfate:chloride equivalent ratio in brine, while the feed sulfate concentration (145–345 mg/L) slightly changed the critical sulfate:chloride equivalent ratio. The use of optimized ternary brine (with a sulfate:chloride:bicarbonate equivalent ratio of 42:5:2) stably achieved long-term highly-selective nitrate removal from groundwater in the standard-AER column process with brine electrochemical treatment. The possible mechanism for nitrate selectivity included the modification of the sulfate: and bicarbonate:chloride equivalent ratios in the standard-AER column by the optimized brine in circular activation/regeneration mode; this changed the column elution and breakthrough curves, inhibited the competition of sulfate and bicarbonate for ion exchange sites during exhaustion according to the separation factor, and finally achieved selective nitrate removal from feedwater.

Design of adsorption column for reclamation of methyldiethanolamine using homogeneous surface diffusion model

A predictive simulation model was applied to design a fixed-bed adsorber for studying the removal of Total Organic Acid (TOA) anions from lean Methyldiethanolamine (MDEA) solution using Calcium Alginate Bentonite (CAB) clay hybrid composite adsorbent. Unlike other conventional techniques typically used for packed bed design, the predictive Homogeneous Surface Diffusion Model (HSDM) does not require any test column breakthrough curves a priori. Mass transfer coefficients and isotherm model parameters are provided as input data to HSDM for simulating column breakthrough curves. Various isotherm models were fitted to batch equilibrium data for TOA adsorption on CAB composite adsorbent. Based on Akaike Information Criterion (AIC), Freundlich isotherm was selected and the model parameters were obtained by non-linear regression. Film transfer coefficients and surface diffusivities were determined using appropriate empirical correlations available in the literature. HSDM predictions were first validated using lab-scale column adsorption data generated at lower residence times. The effects of dimensionless numbers (Biot and Stanton) on breakthrough times were investigated using the dimensionless HSDM system and a suitable scale-up regime (Bi&amp; ~&amp; 1 and St&amp; &gt;&amp; 10) was established wherein the sensitivity of mass transfer parameters would be minimal. Using similitude rules on key design parameters, a pilot-scale adsorption column was designed and breakthrough curves were generated using the validated HSDM. The appropriateness of the design technique was verified by comparing the estimated breakthrough data and column design parameters with conventional scale-up and kinetic approaches.

Effects of microplastics and earthworm burrows on soil macropore water flow within a laboratory soil column setup

AbstractSeveral earlier studies reported that microplastics (MP) accumulated on soil surfaces could be transported into the subsoil and ingested by soil biota, such as earthworms. The present study explores how networks of earthworm burrows and MP (low‐density polyethylene, LDPE) in subsoil affect the soil hydraulic properties and saturated water flow. A repacked and saturated sandy soil column experiment was conducted in an environment‐controlled laboratory with earthworms (anecic, Lumbricus terrestris) inoculated into the soil columns to form networks of macropore. The macropore network parameters (i.e., number, length, volume, diameter, soil saturated conductivity, and tracer breakthrough curves of soil columns) have been determined. The relative arrival times of the tracer mass (i.e. T5%, T25%, and T50%) were determined in order to describe the shapes of the breakthrough curves. The results show that in some breakthrough curves for the treatments with earthworms, there are two peaks. This is an indication that water was flowing faster in the macropores than in the soil matrix. There is a significant correlation between 5% arrival time and the median burrow volume, and the correlation coefficient was .571 (at the level of p &lt; .05). The formation of macropores due to the burrowing activities of earthworms is considered the main cause of nonequilibrium water flow in the present study. The MP did not show any significant effect on the saturated water flow. This may be attribute to the low concentrations of MP used in the present study.

Phosphate recovery with granular acid-activated neutralized red mud: Fixed-bed column performance and breakthrough curve modelling

Granular acid-activated neutralized red mud (AaN-RM) has been successfully prepared with good chemical stability and physical strength. However, its potential for industrial application remains unknown. Therefore, the performance of granular AaN-RM for phosphate recovery in a fixed-bed column was investigated. The results demonstrated that the phosphate adsorption performance of granular AaN-RM in a fixed-bed column was affected by various operational parameters, such as the bed depth, flow rate, initial solution pH and initial phosphate concentration. With the optimal empty-bed contact time (EBCT) of 24.27 min, the number of processed bed volumes and the phosphate adsorption capacity reached 496.95 and 84.80 mg/g, respectively. Then, the saturated fixed-bed column could be effectively regenerated with a 0.5 mol/L HCl solution. The desorption efficiency remained as high as 83.45% with a low weight loss of 3.57% in the fifth regeneration cycle. In addition, breakthrough curve modelling showed that a 5-9-1 feed-forward artificial neural network (ANN) could be effectively applied for the optimization of the fixed-bed adsorption system; the coefficient of determination (R2) and the root mean square error (RMSE) evaluated on the validation-testing data were 0.9987 and 0.0183, respectively. Therefore, granular AaN-RM fixed-bed adsorption exhibits promising potential for phosphate removal and recovery from polluted water.

Optimizing experimental binary adsorption of aniline–nitrobenzene onto granular activated carbon packed bed by Taguchi’s methodology

Herein a new statistical approach based on Taguchi’s methodology was developed for optimizing continuous simultaneous adsorption of aniline (AN) and nitrobenzene (NB) from their binary aqueous solution in a column packed with granular activated carbon (GAC). Effects of column design parameters such as feed flow rate (Q), bed height (Z) and bed diameter (D) were studied for the breakthrough curve performance using Taguchi’s L9 orthogonal array design. The parameters were optimized at three levels with the higher-is-better type response characteristics. Further, the Thomas model was used to predict column breakthrough curve and breakthrough time. Higher sorption affinity of NB over AN towards GAC surface implied favorable attachment of NB molecules. Quicker breakthrough attainment was observed at higher Q, lower Z and lower D owing to faster saturation of sorption sites. Maximum individual equilibrium adsorption uptake for AN and NB was found to be 0.29 mg/g and 3.91 mg/g, respectively, at Q = 0.02 L/min, Z = 60 cm and D = 2.54 cm. The average total equilibrium adsorption uptake (qtot) from the experimental runs was found to be 4.2 mg/g which is closer to the predicted qtot value of 4.17 mg/g.