Modified Dose Response Model Research Articles

Exploring shared adsorption capacity and thermodynamics for simultaneous removal of microcystin and phosphorus via green sorption media in eutrophic water

The recurrent events of harmful algal blooms due to an increase of nutrients in eutrophic water bodies have augmented concerns over the presence of cyanobacterial toxins, especially Microcystin. Microcystin-LR (MC-LR) is the most common cyanobacteria toxin, gaining focus in the literature for its effect on human health. The aim of this study is to investigate the simultaneous removal of MC-LR and phosphate via four green sorption media is the presence or absence of phosphorus or calcium ions and their shared adsorption capacity and thermodynamics to mimic eutrophic water condition in a karst environment (South Florida). The four green sorption media are known as: (1) CPS (clay, perlite, and sand), (2) ZIPGEM (Zero-valent-Iron and Perlite-Based Green Environmental Media), (3) BIPGEM-1 (Biochar-Zero-valent-Iron and Perlite-Based Green Environmental Media-1), and (4) BIPGEM-2 (Biochar-Zero-valent-Iron and Perlite-Based Green Environmental Media-2). Based on the MC-LR removal efficiency, BIPGEM-2 has the best performance, followed by BIPGEM-1, ZIPGEM, and CPS. In terms of simultaneous removal of phosphate ions and MC-LR, ZIPGEM achieves higher removals, ranging from 55 to 60%, followed by BIPGEM-2, BIPGEM-1, and CPS. The MC-LR adsorption capacity of BIPGEM-2 ranges from 16.9 to 29.49 μg·g−1 based on the Langmuir isotherm model under different influent conditions, whereas the MC-LR adsorption capacity of BIPGEM-1 in a dynamic environment is 1.19 μg·g−1 based on the Modified Dose Response model. The decrease in the adsorption capacity of BIPGEM-1 in a dynamic environment can be attributed to the presence of dissolved organic matter and inorganic ions, present in the influent water matrix. The influence of the water matrix is also observed in the isotherm studies because the presence of PO43− negatively impacts the removal efficiencies of MC-LR, whereas Ca2+ positively impacts the removal efficiencies of MC-LR. Similarly, the presence of MC-LR affects the PO43− adsorption capacity of the sorption media.

Gold recovery from synthetic mine tailings leachate using chelating ion exchange resins with thiosulfate-thiourea lixiviant

Recovery of gold from mining tailings is important economically and environmentally in the mining industry. With a limited amount of mineable gold remaining, the process of recovering gold from mine tailings needs development. This paper will specifically investigate the recovery of gold using ion-exchange resins in a thiosulfate-thiourea lixiviant solution. A range of resins of different functionalities: Purolite® A200 (Type II quaternary ammonium), Lewatit® MonoPlus TP 214 and Puromet® MTS9140 (thiourea), Dowex™ M-4195 (bis-picolylamine) and Lewatit® VPOC 1026 (di(2-ethylhexyl)phosphate- D2EHPA) were assessed for their gold uptake capabilities via dynamic column experiments. A mixed-metal solution was used to accurately simulate the spent lixiviant from thiosulfate/thiourea leaching of mine tailings. All resins showed selectivity towards gold over the numerous other metals in solution, which was believed to be due to the stability of aqueous gold thiourea complexes. Puromet® MTS9140 had the highest gold capacity, with a calculated uptake capacity of 41.6 mg/L. Modified-Dose Response (MDR), Bohart-Adams and Yoon-Nelson models were used to describe the data; the MDR model being the most successful.

Chemically activated carbon nanofibers for adsorptive removal of bisphenol-A: Batch adsorption and breakthrough curve study

Activated carbon nanofibers (ACNFs) with small diameter can significantly increase the accessibility of intra pores and accelerate adsorption of molecules from water. In this study, ACNFs were made by blending K2CO3 or ZnCl2 as the activating agent into the polyacrylonitrile (PAN) in dimethylformamide solution for electrospinning prior to pyrolysis. Bisphenol-A (BPA), an endocrine disruption pollutant, is widely applied in the production of polycarbonate plastics and epoxy resins. Accordingly, BPA is often used as a model contaminant commonly removed via adsorption. Batch adsorption studies were used to evaluate the kinetics and adsorption capacity of the ACNFs. Redlich–Peterson (R–P) and Langmuir models were found to fit the isotherm of BPA adsorption better than Freundlich model, showing the homogeneous nature of the PAN originated ACNFs. The adsorption kinetics was better described by the pseudo second-order model than that by the pseudo first-order model. The fitting by intraparticle diffusion model indicates the adsorption of BPA onto ACNFs is mainly controlled by pore diffusion. High pH value and ionic strength reduced BPA adsorption from aqueous solution. The breakthrough curves studied in two different fixed bed systems (cross flow bed system and packed flow bed system) confirmed the scalability of BPA removal by ACNFs in dynamic adsorption processes. The modified dose–response model predicted well the fixed-bed outlet concentration profiles.

Optimization of a compact on-site stormwater runoff treatment system: Process performance and reactor design

Stormwater runoff has become a major anthropogenic urban pollution source that threatens water quality. In this study, coagulation-sedimentation, and ammonium ion exchange and regeneration (AIR) modules were coupled as a CAIR system to efficiently treat stormwater runoff. In the coagulation module, 99.3%, 91.7%, and 97.0% of turbidity, total phosphorus, and chemical oxygen demand could be removed at an optimized poly-aluminum ferric chloride dosage of 30 mg/L, and the continuous experiment confirmed that the full load mode was more suitable for its rapid start-up. In the AIR module, dynamic ammonium removal indicated that the breakthrough time decreased with the rising initial concentration and superficial velocity. The Modified Dose Response (MDR) model described the ammonium exchange behavior better than the Thomas and the Bohart-Adams models. Then, a design flow of the ion exchange reactor was constructed by correlating constants in the MDR model with engineering parameters, and the ion exchange reactor was designed for continuous operation of the CAIR system. The average concentrations of chemical oxygen demand, total phosphorus, ammonium nitrogen, and total nitrogen in the effluent of the CAIR system were 7.22 ± 2.26, 0.17 ± 0.05, 1.49 ± 0.01, and 1.62 ± 0.02 mg/L, respectively. The almost unchanged exchange capacity and physicochemical properties after the multicycle operation confirmed the durability of zeolite for ion exchange. Techno-economic analysis suggested that the CAIR system is practically promising for stormwater management with efficient pollutants removal, small footprint, and acceptable operating cost.

Green sorption media for the removal of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) from water

This study investigated the removal of selected per- and polyfluoroalkyl substances (PFAS) from water via two green sorption media (IFGEM-7 and AGEM-2). Both selected green sorption media recipes contain sand (85–91%) and clay (3–4%), in addition to recycled iron (Fe) (5–7.5%) or aluminum (Al) (4.5% in AGEM-2 only). Batch and column studies were integrated and performed using the prescribed green sorption media recipes to determine their efficiencies in removing two most targeted PFAS, including perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). In the batch test, while the removal efficiencies of PFOS ranged from 27 to 46% and 23 to 42%, those for PFOA ranged from 6 to 16% and 5 to 18% when using IFGEM-7 and AGEM-2, respectively. The higher removal of PFOS than PFOA observed in both IFGEM-7 and AGEM-2 batch tests could be attributed to higher media affinity for sulfonate groups of PFOS when compared to the carboxylate groups of PFOA. In the column study, the initial removal (within 1 h) by IFGEM-7 was greater than 99% for PFOS and 28% for PFOA. When comparing different dynamic adsorption models, it appears that the non-linear equations could better describe the trend of experimental data compared to the linear forms of the Modified Dose Response model. Life expectancy calculations, performed for demonstration purposes of field applications, suggested that if IFGEM-7 were to be applied in a downflow filter box to treat a hypothetical volume of 60,000 L of water during an emergency response, and it may last for 1506 h (62.8 d) and 4.2 h for a target removal of 80% of PFOS and PFOA, respectively.

Deeper Insights into the Bohart-Adams Model in a Fixed-Bed Column.

The Bohart-Adams model was one of the most widely used breakthrough models in column experiments. However, it usually provided a poor fit for the modeling of an asymmetric breakthrough curve. This work proposed the n-order Bohart-Adams and fractal-like Bohart-Adams models. The former indicated a nonlinear decay process of the concentration of the adsorbate or residual capacity of the adsorbent, while the latter reflected a diffusion-limited process on the heterogeneous surfaces. The Bohart-Adams and modified Bohart-Adams models were mathematically equivalent. The applicability of the n-order Bohart-Adams and fractal-like Bohart-Adams models was validated by norfloxacin and Cu(II) adsorption in a fixed-bed column. Compared with the Bohart-Adams model, the two new models had better fitting performance with higher R2 and lower χ2 values, and all of the residuals were randomly distributed. The fractal-like Bohart-Adams and modified dose-response models provided the best fitting quality for the adsorption of Cu(II) (R2 = 0.9956 and χ2 = 7.56 × 10-4) and norfloxacin (R2 = 0.9991 and χ2 = 1.37 × 10-4), respectively. This work may provide a practical method for the modeling of the asymmetric breakthrough curves.

Fixed-bed adsorption of bisphenol A onto organoclay: Characterisation, mathematical modelling and theoretical calculation of DFT-based chemical descriptors

Bisphenol A (BPA) is a noteworthy and ubiquitous chemical of concern. Up to this day, several methods of water remediation have already been tested, however, few studies have addressed the fixed-bed adsorption of this contaminant. In this regard, this work aimed to evaluate the continuous adsorption of BPA using an organoclay (Spectrogel® type-C) as an adsorbent. The material passed through a series of characterisation techniques to elucidate the impact of the contaminant uptake onto the organoclay. The effect of the operation conditions on the adsorption behaviour was evaluated through breakthrough curves and the calculation of mass transfer and efficiency parameters The system conducted at 0.6 mLmin−1 and 0.2 mmolL−1 obtained the highest removal (95%) until breakthrough point (19.29 h), as well as greater breakthrough and exhaustion adsorption capacities (0.0424 and 0.2151 mmolg−1, respectively). The breakthrough curves were correlated by five distinctive models and the modified dose response model showed the finest fitting to the data (R2 >0.97). Furthermore, the regeneration potential of the spent adsorbent was investigated. It was observed that NaOH solution was a satisfactory eluent. Moreover, density functional theory (DFT) calculations were studied to give further insights regarding BPA adsorption.

Comparison of hemagglutination inhibition and hemagglutinin pseudovirus neutralization titres in relation to protection against influenza in a mouse model.

The hemagglutination inhibition (HI) test has long been used as a standard measure of antibody response for inactivated influenza vaccines. However, the HI test has limitations, such as insensitivity when using some H3N2 virus strains and failure to detect neutralizing antibodies that target regions distant from the receptor binding site. We therefore examined a hemagglutinin pseudovirus neutralization (PVN) test as a possible supplement or alternative to the HI test. We evaluated the association of HI or PVN titres with protection against influenza infection in mice based on morbidity (where the illness was defined as 25% body weight loss). We assessed this relationship using dose-response models incorporating HI or PVN titres as a variable. The morbidity was correlated with the pre-exposure titres, and such a correlation was well described by a modified dose-response model. The mathematical modelling suggests that PVN titres consistently show a stronger association with invivo protection as compared to HI titres in mice. Given our findings, the PVN test warrants further investigation as a tool for evaluating antibody responses to influenza vaccines containing hemagglutinin. The resulting models may also be useful for analyzing human clinical data to identify potentially protective antibody titres against influenza illness.

A New Alternative and Efficient Low-Cost Process for the Removal of Reactive Dyes in Textile Wastewater by Using Soybean Hull as Adsorbent

The main objective of this work is to use soybean hull (SBH) waste as an adsorbent for the removal of two industrial textile dyes: Reactive Blue 21 (RB21) and Reactive Yellow 145 (RY145). Physical characterization of SBH and kinetic and equilibrium experiments were performed to determine the adsorption conditions. The best adsorption condition was pH 2.0 because the zero electrical charge of soybean hulls (pHZ = 0) is 5.27; thus, in an acidic pH, the adsorbent is positively charged, and the dyes keep their anionic charges due to the –SO3− and –OSO3− groups. Kinetic data were better represented by the Elovich kinetic model, evidencing two well-differentiated mass transfer regions, which agrees with a pseudo-second-order kinetic mechanism. The experimental data showed that RB21 and RY145 were fitted with Hill and Redlich–Peterson isotherm models, respectively. Consequently, the maximum adsorption capacities of SBH for RB21 and RY145 dyes were 149 mg/g and 87 mg/g, respectively. Dye adsorption in packed bed column was also assayed at different bed heights, flow rates, and inlet concentration of dyes. The Thomas, Yoon–Nelson, and modified dose-response (MDR) models fitted well to the breakthrough curves, the MDR model being the one with the highest correlation coefficients, with 96.5% and 94.4% removal of RY145 and RB21 dyes, respectively.

Comparative modelling analysis of boron dynamic adsorption on fibrous adsorbent prepared using radiation grafting versus granular resin

A comparative study was carried to investigate the selective removal of boron from aqueous solutions over fibrous adsorbent and Diaion CRB03 granular resin in a fixed-bed dynamic column. The fibrous adsorbent was prepared by radiation induced grafting of vinylbenzyl chloride (VBC) onto nylon-6 fibres followed by treatment with N-methyl-D-glucamine (NMDG). The effect of variation of the space velocity (SV) on the breakthrough curves was investigated. The experimental boron adsorption data over both fibrous adsorbent and granular resin were analysed with various mathematical models such as Bohart-Adams, Thomas, Yoon-Nelson, Clark, and modified dose response (MDR) models using non-linear regression. The experimental adsorption data of both fibrous adsorbent and resin were found to best fit MDR model allowing the establishment of breakthrough curves. The fibrous adsorbent showed higher adsorption capacity values than granular resin at all space velocities (SV). This was accompanied by an increase in the adsorption capacity with the increase in SV from 20 to 100 h−1 unlike granular resin, which showed an opposite trend. The adsorbed boron was eluted using 0.1 M HCl and the regenerated adsorbent remained stable after adsorption/desorption 10 cycles. The results of this study suggest that the fibrous adsorbent prepared in this study outperformed the Diaion CRB03 granular resin reflecting its great potential for boron removal from aqueous solutions at pilot and industrial scaled applications.

Kinetic Studies of Cs+ and Sr2+ Ion Exchange Using Clinoptilolite in Static Columns and an Agitated Tubular Reactor (ATR)

Natural clinoptilolite was studied to assess its performance in removing caesium and strontium ions, using both static columns and an agitated tube reactor (ATR) for process intensification. Kinetic breakthrough curves were fitted using the Thomas and Modified Dose Response (MDR) models. In the static columns, the clinoptilolite adsorption capacity (qe) for 200 ppm ion concentrations was found to be ~171 and 16 mg/g for caesium and strontium, respectively, highlighting the poor material ability to exchange strontium. Reducing the concentration of strontium to 100 ppm, however, led to a higher strontium qe of ~48 mg/g (close to the maximum adsorption capacity). Conversely, halving the column residence time to 15 min decreased the qe for 100 ppm strontium solutions to 13–14 mg/g. All the kinetic breakthrough data correlated well with the maximum adsorption capacities found in previous batch studies, where, in particular, the influence of concentration on the slow uptake kinetics of strontium was evidenced. For the ATR studies, two column lengths were investigated (of 25 and 34 cm) with the clinoptilolite embedded directly into the agitator bar. The 34 cm-length system significantly outperformed the static vertical columns, where the adsorption capacity and breakthrough time were enhanced by ~30%, which was assumed to be due to the heightened kinetics from shear mixing. Critically, the increase in performance was achieved with a relative process flow rate over twice that of the static columns.

Simultaneous recovery of Pd(II), Ir(III) and Rh(III) from aqueous solutions by spent brewer’s yeast-functionalised zeolite using flow-through column mode

Economies of many countries around the world have been improved by the mining of precious elements such as gold and platinum group elements (PGEs). As such, the demand for these elements has increased over the years, which led to increased rate of mining. However, the resources and reserves of these elements have been reduced as a result. The alarming rate of mining indicates a need for secondary sources for precious elements. This study was aimed at using a cheap and efficient spent brewer’s yeast-functionalised zeolite to recover Pd(II), Ir(III) and Rh(III) from aqueous solutions. The solutions represent industrial wastewaters which normally contain PGEs which were lost during processing. The adsorbent bed height, solution pH, initial concentration and flow rate were optimised to obtain the best working conditions of the adsorbent. The bed depth service time, Adams-Bohart, Thomas, Yoon-Nelson, Clark column, Wolborska and modified dose response models were used to evaluate the dynamic behaviour of the column. The maximum recovery was achieved at longer bed height, low concentration (2 mg L−1) and low flow rate (2 mL min−1). The speciation of the elements at different conditions motivated the recovery outcome. For example, the dominant species Pd(II) and Ir(III) were negatively charged at highly acidic pH hence, their uptake was favoured by the positively charged surface but, the uptake of Rh(III) was not favoured at these conditions since, [RhCl(H2O)5]2+ and [RhCl2(H2O)4]+ were dominant and thus, repelled by the adsorbent. The success of the recovery of Pd(II), Ir(III) and Rh(III) from aqueous solutions makes the adsorbent a potential recovery agent in the PGEs mining industrial wastewater.

Adsorption potentials of iron-based metal–organic framework for methyl orange removal: batch and fixed-bed column studies

In the present work, continuous fixed-bed column and batch studies were undertaken to investigate the efficiency of iron-based metal–organic framework (Fe-BTC) for the removal of methyl orange as a model contaminant from aqueous solutions. The batch experiments were carried out by varying operational parameters such as adsorbent dosage, pH, temperature, and initial contaminant concentration. The results showed that Fe-BTC had a high removal efficiency under a wide pH range. The equilibrium data were best fitted by the Langmuir model with a maximum adsorption capacity of 100.3 mg g−1 at 298 K. In order to assess the industrial feasibility of Fe-BTC, fixed-bed column studies were conducted to obtain breakthrough curves, breakthrough and saturation times, and maximum uptakes at different bed heights. The breakthrough time was 20.0 and 46.2 h at 0.75 and 1.5 cm bed depths, respectively. The bed removal efficiency was 35.2 and 46.7% at 0.75 and 1.5 cm bed depth, respectively. The bed maximum adsorption capacity was 20.2 and 21.6 mg/g at 0.75 and 1.5 cm bed depths, respectively. Moreover, the application of empirical breakthrough curve models showed good agreement with the modified dose response model (R2> 0.99). Also, the analytical solution of the advection–dispersion–adsorption mass transfer equation showed an excellent fit to the experimental breakthrough data (R2> 0.99). Further, the analytical model was utilized to predict the length of the mass transfer zone as a function of the bed depth and to construct a 3D surface plot that can be utilized to predict the breakthrough at different bed depths.

Selective removal of boron from industrial wastewater containing high concentration of ammonia by radiation grafted fibrous adsorbent in fixed bed column

Removal of boron from real industrial wastewater containing high concentration of ammonia was investigated using a fibrous adsorbent bearing glucamine groups obtained by green method. The adsorbent was prepared by radiation induced emulsion grafting (RIEG) of glycidyl methacrylate (GMA) onto nylon-6 fibres and subsequent treatment with N-methyl-D-glucamine (NMDG) under controlled conditions. The performance of the obtained adsorbent was tested for adsorption of boron from a real industrial wastewater containing high concentration of ammonia in comparison with a synthetic aqueous solution using in a fixed bed-column under different feed space velocities (SV). The dynamic adsorption data of the fixed column was tested against three most common mathematical adsorption models: Yoon–Nelson, Thomas and Modified Dose-Response (MDR) models to predict breakthrough curves and determine the column design parameters. The results showed that the experimental breakthrough curves were best fitted by MDR model. The adsorbed boron was eluted with 1 M HCl solution and the adsorbent was regenerated for stability evaluation using 5 adsorption/desorption cycles. The results suggest that the obtained adsorbent has a strong potential for industrial pilot scale boron removal applications.

Continuous dye adsorption and desorption on an invasive macrophyte (Salvinia minima).

The continuous adsorption-desorption of methylene blue (MB) on an invasive macrophyte, Salvinia minima, was investigated in fixed-bed columns. The effects of bed depth (h) (9.30, 18.70, and 28cm), inlet dye concentration (C0) (51 ± 1.20, 154 ± 2.00, and 250 ± 1.50mgL-1), and flow rate (Q) (7 and 14mLmin-1) on dye removal and breakthrough curves were assessed. Thomas, modified dose-response (MDR) and bed depth service time (BDST) models were fitted to the experimental data. Desorption and regeneration studies were also performed. The breakthrough time was affected by h, C0, and Q. The dynamic bed capacity at the breakthrough point (qb) increased with increasing h but decreased with increasing C0 and Q. Dynamic bed capacities (qe) from 318 to 322mgg-1 were achieved at h= 28cm, C0= 154 ± 2.0, or 250 ± 1.50mgL-1, independently of the Q value. High MB removals were also observed (75-78%). FTIR analysis revealed that hydroxyl and carboxyl groups could be involved in dye adsorption. MDR and BDST models were both successfully used to predict the breakthrough curves of MB adsorption onto S. minima. A high regeneration efficiency (> 87%) was obtained after three adsorption-desorption cycles. These results confirm that the use of S. minima biomass could be a very efficient and eco-friendly alternative for MB adsorption in continuous mode.

Experimental and modeling investigation of thorium biosorption by orange peel in a continuous fixed-bed column

In this research work process parameters and breakthrough modeling of thorium biosorption on orange peel in a fixed-bed column has been studied. Some experiments have been done with sorbent diameter, flow rate, bed height and feed inlet concentration. Breakthrough point decreased with decreasing the bed height, increasing feed inlet concentration and increasing flow rate. Meanwhile, sorption capacity increased with decreasing bed height and flow rate. The highest sorption capacity, 87.7 mg/g, occurred in a 0.4–0.8 mm sorbent diameter. The experimental results were fitted by models of Thomas, Yoon–Nelson and Modified Dose–Response (MDR). The MDR model showed better results.

Cu(II) removal using green adsorbents: kinetic modeling and plant scale-up design.

Cu(II) adsorption in continuous column using green adsorbents like peanut and almond shell was investigated. Fourier transform infrared (FTIR) spectroscopy, Brunaer-Emmett-Teller (BET) analysis, scanning electron microscopy (SEM), and Point of Zero charge (pHpzc) determination have been used for characterization of the adsorbents. Experiments were conducted at various operating conditions to calculate the adsorption capacity of the adsorbents. Adsorption studies signify that both the adsorbents have good adsorptive capacity for Cu(II) ion. Equilibrium of adsorption was described using Langmuir isotherm and the highest qmax value for both the adsorbent were obtained at an operating condition of 20ml/min flow rate, 15mg/L influent Cu(II) concentration, and 7cm bed depth. Regeneration of both the adsorbents suggests that these adsorbents can be used several times for Cu(II) removal. Seven different kinetic models were tested among which the modified dose response model was fitted well for peanut shell and the Thomas model was fitted well for almond shell. These fitted models were further used for scale-up design. Regeneration studies show that peanut shell and almond shell are useful up to the fifth adsorption cycle. Application of these adsorbents with industrial effluent was also reported. This study reveals that peanut and almond shells can be used for Cu(II) removal for industrial wastewater.

Assessing the applicability of an agro-industrial waste to Engineered Bio-char as a dynamic adsorbent for Fluoride Sorption

A potential feedstock, de-oiled Pongamia-pinnata seed cake is used to prepare engineered Bio-char (EBC) for the removal of fluoride from ground water. EBC was characterized and batch biosorption studies were conducted at different initial fluoride concentrations, EBC dosages and pH values. A maximum fluoride adsorption occurred at pH-7 with an equilibrium time of 90 min and EBC dosage of 10 mg/L. Different isotherm models were investigated, among which Langmuir was found to best fit with a maximum adsorption capacity of 0.985 ± 0.025 mg/g. The chemisorption was defined by Ritchie-pseudo-second-order kinetics with intra-particle diffusion contributing to the rate determining step. Column studies with variable operating conditions (initial fluoride concentration, bed depth, flow rate) and modeling of the breakthrough curves showed modified dose response model in excellent agreement with a maximum uptake of 1.12 ± 0.025 mg/g. EBC regeneration, comparison with contemporary sorbents and its real time application are also explored in the present study.

Packed bed column dynamic study for boron removal from geothermal brine by a chelating fiber and breakthrough curve analysis by using mathematical models

In this study, the performance of N-methyl-d-glucamine (NMDG) type functional group attached a novel boron selective chelating fiber adsorbent, Chelest Fiber GRY-HW, was investigated for boron removal from geothermal brine containing 10–11 mg B/L through a packed bed column. The effect of feed flow rate (Space Velocity, SV) on breakthrough capacity of Chelest Fiber GRY-HW was studied using various SV values (15, 20 and 30 h−1). The effect of SV on breakthrough capacity was particularly apparent when SV was decreased from 30 to 15 h−1. Yoon–Nelson, Thomas and Modified Dose Response (MDR) models were applied to the experimental data to estimate the breakthrough curves and model parameters such as rate constants and breakthrough times. The obtained results showed that the breakthrough curves were better described by Modified Dose Response (MDR) model than those described by Yoon-Nelson and Thomas models in each case. Also, the model estimations for adsorption capacity obtained by MDR model agreed well with the experimental results.

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.