Bed Depth Service Time Research Articles

Use of response surface methodology to optimize triclosan adsorption on alumina pillared clays in a fixed-bed column for applications in solid-phase extraction

Fixed-bed column studies are generally conducted to consider possible applications in water-purification processes. In this work, three synthetic alumina pillared interlayered clays (Al-PILC) were analyzed in fixed-bed column studies for use as sorbents for solid-phase extraction (SPE) for the first time. Adsorption processes were studied for triclosan (TCS), which is an emerging pollutant (EP) that has been shown to have several health effects. Breakthrough curves were investigated by varying process parameters such as bed height (0.25–0.75 cm), inlet TCS concentration (20–60 mg/cm3), and flow rate (0.5–3 cm3/min). Bohart-Adams, Bed Depth Service Time (BDST), and Thomas models were satisfactory applied to the results obtained for fixed-bed columns. The adsorption of TCS was successfully optimized for use in SPE for the three adsorbents studied using response surface methodology with a Box–Behnken design (RSM-BBD). The models developed were adequate for the experimental data (95% significance level), with high regression parameters (98.9–99.1). The optimum values for TCS adsorption on the fixed-bed column were 378.04, 367.78, and 378.93 mg (amount of adsorbent packed into the column), 0.5 cm3/min (flow rate), 4.24, 3.96, and 3.85 (pH), and 2.56, 1.93, and 1.13 mg/dm3 (inlet TCS concentration) for Al-PILCAE, Al-PILCBE, and Al-PILCCM, respectively. From these results synthetic Al-PILC are effective and promising sorbents that can be used for analytical purposes in SPE, and that RSM-BDD is an effective and reliable tool for evaluating and optimizing the adsorption conditions for emerging contaminants in a fixed-bed column system.

Bench-scale integrated bone and biochar bed treatment of geogenic fluoride contaminated groundwater from Bongo in Ghana

The article explores the adsorption of fluoride in groundwater and the synergistic properties of a mixture of bone char and biochar. The bone char and biochar were produced using cattle bones and coconut husks, bamboo, neem tree and palm kernel in a locally constructed double-barrel retort with particle size ranging from 0.05 to 0.315 mm. The morphology of the char was examined using a scanning electron microscope and energy dispersive spectroscopy for elements. The surface functional groups were assessed by Fourier-transform infrared spectroscopy. Almost all the fluoride was removed from the groundwater within 15–27 min of column treatment. Cattle bone char standalone treatment was the most effective adsorbent, with a removal rate of 91.4%, which is almost identical to the integrated removal rate of 91.1% for bone char and coconut husk biochar. The presence of the hydroxyapatite groups in the bone char together with the high surface areas of the chars increased the integrated bed's effectiveness in lowering fluoride concentrations in contaminated groundwater from 3.6 mg/L to 1.5 mg/L with an adsorption capacity of 0.084 mg/g. The breakthrough curves were predicted with the bed depth service time model under the same operational conditions. The integrated bed showed almost 100% efficacy in removing fluoride from contaminated groundwater with a 3.6 mg/L fluoride concentration within a breakthrough time of 15–27 min. This was due to the interplay between the chars' high surface areas and the hydroxyapatite groups in the bone char, which enhance adsorption and the synergistic effect of the integrated char.

Microporous melamine-formaldehyde networks loaded on rice husks for dynamic removal of organic micropollutants

The alteration of agricultural wastes into novel adsorbents can stimulate their scalability in realistic application, showing great economic and environmental advantages. Here, we proposed a strategy to engineer rice husk (RH) with microporous melamine-formaldehyde networks (MFNs) resins and the utilization for dynamic removal of organic micropollutants rapidly and efficiently. was pre-treated to acquire attractive surface and unique hierarchical porosity, endowing with surface functionalization and essential filtering properties. MFNs can be uniformly generated in-situ on the fully exposed cellulose backbones of the pre-treated RH. MFNs granules functionalized RH (RH@MFNs) exhibited high removal efficiencies over 90% within 30 min for the adsorption of hazardous organic compounds (e.g., phenolic and antibiotic micropollutants) in static tests. Experiment results and density functional theory (DFT) simulation revealed that the synergy of hydrogen bonding, π-πinteraction, and micropore preservation dominates the adsorption. Further dynamic adsorption experiments showed that the removal efficiency and equilibrium removal capacity towards bisphenol A by RH@MFNs packed bed up-flow column were 2.6 and 67 times higher than that of raw RH, respectively. The column adsorption fits well with the Thomas model and bed depth service time (BDST) kinetic model. The inherent macropores inside RH and the roughness caused by the spiky structures and mesopores outside RH, as well as the accumulated MFNs granules, can lead to local turbulence of water flow around RH@MFNs, enabling fast and efficient adsorption. This sustainable and cost-effective preparation of RH-based adsorbents sheds light on the rational design of biomass waste adsorbents for realistic wastewater.

Modeling Date Palm Trunk Fibers (DPTF) Packed Bed Adsorption Performances for Cadmium Removal from Aqueous Wastewater

In this study, the potential of a low-cost bio-adsorbent, taken directly from Date Palm Trunk Fibers (DPTF) agricultural wastes, for cadmium ions removal from wastewaters is examined. The performances of this adsorbent are evaluated by building breakthrough curves at different bed heights and flow rates while keeping other parameters, such as the initial feed concentration, pH, and particle size, constant. The results indicate that the maximum cadmium adsorption capacity of DTPF can be obtained from the Thomas model as 51.5 mg/g with the most extended mass transfer zone of 83 min at the lowest flow rate at 5 ml/min. The saturation concentrations (NO) and the rate constant (kab) obtained from the BDST (bed depth service time) model are 7022.16 mg/l and 0.0536 l/mg.min, respectively. Using the Yon-Nelsen Model, it is found that operating at a lower flow rate leads to a larger value of the elapsed needed time to reach a 50% breakthrough. The Wolborska model indicates that the bed capacity increases with decreasing the flow rate, and the adsorbent can achieve a greater external mass transfer kinetic coefficient (2.271/min) at a higher flow rate.

Dynamic Study and Modelling of Arsenic Removal from Groundwater Using Ferromagnetic Carbon as Fixed Bed Adsorbent in Column

This study investigated the performance of Ferromagnetic Carbon (FC) as an effective natural adsorbent for arsenic removal from groundwater in Dong Thap Province (Vietnam). To do this, leaching fixed-bed column experiments have been carried out. The influence of operating variables affecting the process was studied, under varying operating conditions and experimental data were modelled using bed depth service time (BDST) and mass transfer approaches. Speciation studies showed that the groundwater contained 48.5% of particulate arsenic and 51.5% of soluble arsenic. Indeed, As (III) and As (V) forms represented respectively 41.9% and 58.1% in the dissolved arsenic. As removal was parametric depending such as pH, flow rate, initial As and adsorbent mass, requiring an optimization for optimum conditions When the pH increased from 3 to 11, removal of As(V) decreased from 96.5% to 5% while As(III) removal increased from 40% to 69%. The increase of initial arsenic has caused an increase in removal efficiency of different forms of arsenic. The easy regeneration of FC using a molar sodium hydroxide solution suggests that is an efficient and low-cost material to reduce the contamination of arsenic in drinking groundwater.

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).

On the development of a consistent mathematical model for adsorption in a packed column (and why standard models fail)

In this paper we investigate the standard one-dimensional model for adsorption of a contaminant in a packed column. Initially we focus on two mass sink models: a full nonlinear Langmuir equation, including adsorption and desorption and the linearised version which neglects the local concentration. Travelling wave solutions are developed for both cases, providing exact analytical formulae for the concentration and adsorbed fraction throughout the column. Comparison is made with experimental data for the adsorption of toluene on activated carbon (dominated by physical adsorption) and Cr(III) on zeolite NaX (dominated by ion exchange). For toluene the nonlinear model provides good agreement but it is less accurate for Cr(III). The linear model apparently works well for Cr(III) but only at the expense of violating the model assumptions. This motivates extending the travelling wave solution to a Sips sink model, which has a power law dependence on local concentration. Comparison with data provides excellent agreement in all cases and also indicates why the previous models fail. Following from the investigation of the linear sink model, we prove that previously accepted results frequently fail due to a violation of assumptions made in their derivation. Specifically we challenge the belief that widely used models such as Bohart–Adams, Yoon–Nelson, Bed Depth Service Time, etc can accurately predict breakthrough data. Their success instead may be attributed to: at times, having a similar shape to the breakthrough curve rather than being the correct solution; treating measurable quantities as fitting parameters and a willingness to accept that constant parameters vary. In contrast to these previous models, the travelling wave solution of the present paper, based on a Sips sink, provides analytical solutions consistent with the model assumptions for a wide range of experimental data.

Adsorption of Safranin dye, an emerging contaminant from wastewater by modified bamboo (Bambusa Tulda): Characterization and column model analysis

AbstractA fixed‐bed column study was studied to assess the performance of sodium bicarbonate modified Bambusa Tulda to remove Safranin from wastewater. Fourier Transform Infrared Spectroscopy analysis shows the existence of carboxyl as well as hydroxyl bonding and grouping. Scanning Electron Microscope analysis shows the enhanced structure of Bambusa Tulda before and after chemical modification, and Energy dispersive X‐ray analysis shows the existence of Na, O after chemical modification with sodium bicarbonate. The maximum removal was found at higher bed depth and low flow rate. The breakthrough analysis time and exhaust time increase with an increase in bed height. At 5 ml/min flow rate, with initial concentration of 50 mg/L and bed height of 15 cm of adsorbent, shows best removal rate of safranin dye in column analysis. The Bed Depth Service Time (BDST) model and Thomas model analysis remained similar with experiment results, which indicates that they are suitable for the design of column study. It is being concluded that sodium bicarbonate modified Bambusa Tulda is an effective, low cost and readily available adsorbent for the adsorption of Safranin from wastewater.

Investigation and Modeling of Fluoride Ion Adsorption on an Azospirillum Biofertilizer

AbstractThe process of fluoride removal from water using an Azospirillum biofertilizer as adsorbent was modeled. Experiments were performed in a column with varying flow rates and bed depths, at constant initial fluoride concentration. The experimental data obtained from the column studies were correlated employing different models: Thomas, Yoon‐Nelson, Adams‐Bohart, Clark, and BDST (bed depth service time). The Thomas and Yoon‐Nelson models were found most suitable for describing the dynamic adsorption process with respect to key operating variables. Breakthrough curves were obtained from the modeled equations. The calculated and modeled breakthrough curves were in agreement with each other.

Modeling of the As (III) adsorption using Fe impregnated polyethylene terephthalate char matrix: A statistical approach.

The present research aimed to analyse the impact of economical Fe impregnated polyethylene terephthalate (PET) char (PETC-Fe) for adsorption of As (III) through series of column experiments. For an inlet arsenite concentration of 1,000 μg/L, PETC-Fe exhibits excellent uptake capacity of 1,892 μg/g. Central composite design (CCD) in response surface methodology (RSM) was used to evaluate the influence of various process variables on the response function (breakthrough time) for optimization and assessment of interaction effects. The breakthrough time is more responsive to influent As (III) concentration and bed height than inlet flow rate, according to the perturbation plot. Adams-Bohart, Bed Depth Service Time (BDST) model, and Thomas models were used to model the dynamics of the adsorption system. The BDST model suited the experimental data well in the early part of the breakthrough curve, but there were minor variations over the breakpoints. Despite the fact that the experimental values and the data sets estimated using the Adams-Bohart model followed a similar pattern, they differed slightly. The PETC-Fe was found to be a sustainable and highly economical adsorbent, with a desorption performance of more than 97%, indicating the adsorbent's reusability. This adsorbent's excellent As (III) uptake capacity and regeneration performance imply that it might be used in industrial/domestic applications, and the information obtained could aid in future scaling up of the adsorption system.

Experimental and modeling of fixed-bed column study for phenolic compounds removal by graphite oxide

Removal of phenol and bisphenol A by cost-effective graphite oxide was investigated in continuous column experiments. The parameters of the column process were investigated at different bed heights (0.50, 1.50, and 4.50 cm) and different flow rates (1.06, 0.50, and 0.25 mL min−1). The initial concentration was fixed at 4.70 mg L−1. The phenolic-compounds removal was optimized in the column with a high bed height and a low flow rate. The experimental data under various conditions were well fitted to the Thomas and El Naas kinetic models. The experimental fixed-bed capacities were better fitted by the nonlinear fixed-bed capacities than the linear values, validating the nonlinear Thomas model. Furthermore, the El Naas method determined the 50 % breakthrough time of the phenolic compounds with a very low percentage error. The bed-depth service time (BDST) models of phenol and bisphenol A removal were successfully scaled up to continuous experiments with no need for further experimental data and analysis.

A fixed-bed column study of solid waste-based calcium silicate hydrate for the phosphate removal

Abstract The calcium silicate hydrate (CSH) was synthesized from the solid waste residue (SWR) of the Alum Factory, and was used for phosphate abatement from an aqueous solution. Fixed-bed column adsorption experiments were conducted at different flow rates (5, 7.5, and 10 mL/min) and bed depths (6, 9, and 12 cm) at an initial pH and phosphate concentrations of 5 and 5.5 mg/L, respectively. The breakthrough curve analysis was developed and tabulated for the effects of the flow rate and bed depth. Fixed-bed adsorption models, namely the Thomas model, the Yoon–Nelson model, and Bed Depth Service Time (BDST) model were fitted to the experimental data. The R2 values observed for the Thomas model and the Yoon–Nelson model were 0.96 and 0.98, respectively, at the flow rate of 7.5 mL/min and bed depth of 9 cm with the breakthrough adsorption capacity of 5.67 mg/g. The synthesized CSH was also tested for its phosphate removal efficiency using local wastewater treatment plant effluent. About 1,658 mL of real wastewater was treated for 249 min before the standard threshold limit (1 mg/L) was reached. This study prevails that the synthesized CSH could be applied to remove phosphate from real wastewater under a continuous flow adsorption system.

Fixed Bed Column Adsorption Studies of selected Phenols and Dyes using Low-cost adsorbents. A mini Review

Consumption of water contaminated with dyes and phenolic compounds is detrimental to human and animal wellbeing even at permissible limits. Therefore, their decontamination from water is important for the safety of consumers. Conventional water treatment techniques such as ozonation, ion exchange among others are expensive and ineffective. Adsorption as an emerging technique has gained research interest because of its ease in design, environmentally friendly and availability of materials as adsorbents in large quantities. The application of various adsorbents have extensively been reported for decontamination of dyes and phenolic compounds in wastewater such as 4-chlorophenol, Metanil Yellow (MY) dye, Phenol, Methyl green dye, Bromothymol Blue dye, Crystal violet, Methylene blue and Direct Blue 71. It has also been reported that adsorption by column continuous processes are more efficient than batch as it can be used continuously under high effluent flow rates in many pollution control processes in an industrial set up. The fixed bed column adsorption data is analyzed at different column conditions of bed height, pH, particle size, concentration and flow rate using different kinetic models such as Bohart-Adams, Thomas, Yoon-Nelson, Clark, Bed depth service time and Wolborska models amongst others to determine the column performance. The present paper involves a mini review of dynamics of fixed-bed column studies for removal of selected dyes and phenolics from a synthetic media.

Fixed bed column performance of Al-modified biochar for the removal of sulfamethoxazole and sulfapyridine antibiotics from wastewater

In this study, biochar derived from bamboo pretreated with aluminum salt was synthesized for the removal of two sulfonamide antibiotics, sulfamethoxazole (SMX) and sulfapyridine (SPY), from wastewater. Batch sorption experiments showed that Al-modified bamboo biochar (Al-BB-600) removed both sulfonamides effectively with the maximum sorption capacity of 1200–2200 mg/kg. The sorption mechanism was mainly controlled by hydrophobic, π-π, and electrostatic interactions. Fixed bed column experiments with Al-modified biochar packed in different dosages (250, 500 and 1000 mg) and flow rates (1, 2 and 4 mL/min) showed the dosage of 1000 mg and flow rate of 1 mL/min performed the best for the removal of both SMX and SPY from wastewater. Among the breakthrough (BT) models used to evaluate the fixed bed filtration performance of Al-BB-600, the Yan model best described the BT behavior of the two sulfonamides, suggesting that the adsorption process involved multiple rate-liming factors such as mass transfer at the solid surface and diffusion Additionally, the Bed Depth Service Time (BDST) model results indicated that Al-BB-600 can be efficiently used in fixed bed column for the removal of both SMX and SPY in scaled-up continuous wastewater flow operations. Therefore, Al-modified biochar can be considered a reliable sorbent in real-world application for the removal of SMX and SPY from wastewater.

Continuous silicic acid removal in a fixed-bed column using a modified resin: Experiment investigation and artificial neural network modeling

In this study, the suitability of a novel modified resin (gallic acid modified resin: GA-type resin) for silicic acid removal was investigated using fixed-bed column adsorption. Laboratory dynamic experiments were conducted at different flow rates, bed heights and influent concentrations. With rising flow rate, the breakthrough time, exhaust time and absorption capacity of the column bed decreased while increasing with column bed height. With the increasing influent concentration from 20 mg/L to 60 mg/L, decrease in both breakthrough time and exhaust time, but an increase in adsorption capacity from 3.73 mg/g to 4.20 mg/g. To simulate the experimental breakthrough curves (BTCs) and predict the column dynamics, basic and empirical models (Bed Depth-Service Time (BDST), Thomas, and Yoon-Nelson models) as well as an artificial intelligence approach (Artificial Neural Network (ANN) model) were applied. All three conventional models were able to reflect well the behavior for silicic acid continuous adsorption with GA-type resin and estimated the characteristic model parameters for removal. ANN model had a higher accuracy (R2 = 0.9997) in predicting BTCs and predicting breakthrough times. Analyzing the parameters obtained from the simulation of the ANN model, the initial concentration was found to have the highest relative importance of 32.94 %, and the specific order of relative importance was as follows: initial concentration > column height > flow rate > total running time. Furthermore, due to its certain regeneration potential, GA-type resin can be recycled, making it a promising material for removing silicic acid from water.

Fixed-Bed Adsorption of Phenol onto Microporous Activated Carbon Set from Rice Husk Using Chemical Activation

In the course of this research, the potential of activated carbon from rice husk was examined as being a phenol removal medium from an aqueous solution in a fixed-bed adsorption column. The activated carbon was characterized through FESEM (Field-Emission Scanning Electron Microscopy) and BET (Brunauer–Emmett–Teller) surface area. According to the FESEM micrograph and BET surface area, RHAC (rice husk activated carbon) had a porous structure with a large surface area of 587 m2·g−1 and mean diameter of pores of 2.06 nm. The concentration effects on the influent phenol (100–2000 mg·L−1), rate of flow (5–10 mL·min−1), and bed depth (8.5–15.3 cm) were examined. It was found that the capacity of bed adsorption increased according to the increase in the influent concentration and bed depth. However, the capacity of bed adsorption decreased according to the increase in the feed flow rate. The regeneration of activated carbon column using 0.1 M sodium hydroxide was found to be effective with a 75% regeneration efficiency after three regeneration cycles. Data on adsorption were observed to be in line with many well-established models (i.e., Yoon–Nelson and Adams–Bohart, as well as bed depth service time models).

Efficient Fluoride Removal by a Fixed-Bed Column of Self-Assembled Zr(IV)-, Fe(III)-, Cu(II)-Complexed Polyvinyl Alcohol Hydrogel Beads.

Fixed-bed column adsorption studies are performed with metal-complexed polyvinyl alcohol (PVA) hydrogel beads to remove fluoride from groundwater. The fixed-bed column (bed height = 8 ± 0.2 cm) of copper–zirconium–PVA (PCZH), zirconium–PVA (PZH), and iron–zirconium–PVA (PFZH) hydrogel beads have equilibrium fluoride removal capacities of 17.26 ± 0.05, 31.67 ± 0.05, and 11.84 ± 0.05 mg g–1 from a 10 ± 0.20 mg L–1 fluoride solution of pH 6.5 maintained at a flow rate of 1 ± 0.01 mL min–1. The breakthrough curves for fluoride adsorption are analyzed by non-linear empirical models of Thomas, Bohart–Adams, Yoon–Nelson, and semi-empirical bed depth service time models. The maximum fluoride adsorption capacities obtained from the Thomas model are 25.66 ± 0.05, 38.17 ± 0.05, and 13.75 ± 0.05 mg g–1 for PCZH, PZH, and PFZH. Moreover, the column of PZH (bed height = 4 ± 0.2 cm) removes about 1.67 ± 0.05 mg g–1 of fluoride from the alkaline groundwater sample with high total dissolved solids containing 2.84 ± 0.20 mg L–1 fluoride maintained at a flow rate of 0.5 ± 0.01 mL min–1. The fluoride removal efficiency decreases marginally (<1 ± 0.02%) in the presence of interfering ions such as chlorides, sulfates, phosphates, bicarbonates, and nitrates. Furthermore, the fixed-bed column (bed height = 4 ± 0.2 cm) of PCZH, PZH, and PFZH remove 7.40 ± 0.05, 14.85 ± 0.05, and 6.53 ± 0.05 mg g–1 fluoride, respectively, even after the third regeneration cycle. Additionally, the hydrogel beads are effective in the removal of arsenate (≤90 ± 0.02%) and chromate ions (≤96 ± 0.02%) from 100 ± 0.20 mg L–1 solution in batch adsorption studies. Therefore, the hydrogel beads could be used as potent filters for the removal of fluoride, chromate, and arsenate ions from water.

Elucidating sorptive eradication of ibuprofen using calcium chloride caged bentonite clay and acid activated alginate beads in a fixed bed upward flow column reactor

The sorptive eradication of ibuprofen (IBP), a pharmaceutical micro-pollutant, from aqueous medium in a fixed bed upward flow column reactor was examined using the adsorbent prepared from amalgamation of calcium chloride caged acid activated tamarind seed and bentonite alginate beads [Ca2+(TAABB)Al]. Surface texture and the presence of constituent elements in the contrived sorbent was characterised by scanning electron microscopy and energy dispersive x-ray analysis at pre-sorption and post-sorption phases. Effect of controlling factors viz. bed height of the column (5–25 cm), influent concentration of IBP (10–25 mg/L), and amount of inflow (2–6 mL/min) on efficacious IBP uptake was evaluated. The column experimentation revealed that there would be a rise in height of the breakthrough curve while the column bed height increases. Along with 97.48% IBP elimination, the maximal adsorbent uptake has been determined to be 17.54 mg/g from an optimum height of column bed of 20 cm, concentration of influent ibuprofen 20 mg/L, and amount of inflow 2 mL/min. Efficiency of the sorbent was investigated using the bed depth service time (BDST) model, and it was observed that bed height of the column was the most important aspects in achieving effective IBP adsorption. The investigational results were well supported by the Yoon–Nelson as well as Thomas model. The desorption analysis demonstrated the performance of adsorbent up to 5 cycles for ibuprofen separation with a column regeneration rate of 38.14%. Hence, the novel sorbent Ca2+(TAABB)Al can be effectively used to eradicate IBP from aqueous phase.

Simultaneous nitrate and phosphate abatement using calcium silicate hydrate adsorbent: Fixed bed column adsorption study

Nitrate and phosphate are the main nutrients that cause eutrophication and thus remedial measures have to be taken. In this work, Calcium Silicate Hydrate (CSH) synthesized from Alum Factory solid waste residue was used to simultaneously remove nitrate and phosphate by fixed-bed column adsorption. The effect of fixed-bed column operating parameters, namely flow rate (5, 7.5, and 10 mL/min.) and bed depth (6, 9, and 12 cm) on the breakthrough curves were examined. Fixed-bed column adsorption models namely Thomas, Yoon-Nelson, Adams-Bohart, and bed depth service time (BDST) were fitted to the experimental data. The observed data demonstrated that Thomas and BDST models were fitted well with the experimental data and thus are suitable to predict the breakthrough curve parameters for both nitrate and phosphate. The column adsorption capacity estimated by the Thomas model for binary-component, mono-component, and municipal wastewater were 1.74 mg/g, 2.13 mg/g and 1.63 mg/g for nitrate, and 4.93 mg/g, 5.61 mg/g, and 3.37 mg/g for phosphate, respectively. The high R2 value of 0.973–0.997 for nitrate and 0.917–0.999 for phosphate indicated that the BDST model could be used to estimate the breakthrough time required for selected depth without conducting extra experiments. Moreover, the fractional value of 0.82 and 0.88 for nitrate and phosphate, respectively calculated using (qm binary)/(qm mono) for simultaneous adsorption of nitrate and phosphate indicated the antagonism (competitive) nature of adsorption. The observation of this work concluded that CSH could be used for the simultaneous removal of nitrate and phosphate from an aqueous solution.

Removal of boron by a modified resin in fixed bed column: Breakthrough curve analysis using dynamic adsorption models and artificial neural network model

Continuous removal of toxic element boron from aqueous solution was investigated with new phenolic hydroxyl modified resin (T-resin) using a fixed bed column reactor operated under various flow rates, bed height and influent concentrations. The breakthrough time, exhaustion time and uptake capacity of the column bed increased with increasing column bed height, whereas decreased with increasing influent flow rate. The breakthrough time and exhaustion time decreased, but uptake capacity increased with increasing influent concentration, and actual uptake capacity was obtained as 6.52 mg/g at a concentration of 7.64 mg/L. The three conventional models of bed depth service time (BDST), Thomas and Yoon-Nelson were used to appropriately predict the whole breakthrough behavior of the column and to estimate the characteristic model parameters for boron removal. However, artificial neural network (ANN) model was more accurate than the conventional models with the least relative error and the highest correlation coefficients. By the relative importance of the operational parameters obtained from ANN model, the sequence is as follows: total effluent time > initial concentration > flow rate > column height. The adsorption capacity of boron was changed between 5.24 and 1.74 mg/g during the five time regeneration. From the life factor calculation, it is suggested that the column bed could avoid the breakthrough time of t = 0 for 6.8 cycles, whereas, the uptake capacity would be zero after 7.8 cycles.