Increasing Bed Height Research Articles

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

Abstract The present research article explored the potential of activated carbon prepared from Limonia acidissima shell to adsorb total Fe ions from aqueous solution in a packed bed up-flow column. The effect of essential factors such as bed height (3–5 cm), initial concentration (30–50 mg/L), and flow rate (3.32–5.4 mL/min) on the performance of the column bed was investigated. The adsorption capacity augmented with an increase in bed height and initial adsorbate concentration but declined with an increase in flow rate. The maximum uptake capacity of 209.6 mg/g was achieved at 5 cm bed height, 3.32 mL/min, and 50 mg/L initial concentration. The bed depth service time (BDST) model was used to analyze the experimental data and determine the characteristic parameters of the packed bed reactor suitable for designing large-scale column studies. The Adams–Bohart, Thomas, and Yoon–Nelson models were applied to the experimental data to predict breakthrough curves using non-linear regression. The artificial neural network (ANN) based model was able to efficaciously predict the column performance using the Levenberg–Marquardt (LM) algorithm. A comparison between the experimental data and model results contributed to a high degree of correlation, specifying that the preliminary information was in good agreement with the ANN predicted data.

Segregation and mixing behavior of geldart D binary particles in pulsed gas-solid fluidized bed

Gas-solid fluidized bed is an effective dry method for beneficiation of −6mm fine coal, belonging to Geldart D particle. Due to the density difference of concentrates and gangue in the raw coal, the bed can remove gangue through segregation of binary particles. The core problem is how to reduce the bubble coalescence and improve segregation degree in the bed. In this study, glass beads and plastic beads were selected to simulate high-density and low-density particles in pulsed gas-solid bed (PGFB). And different pulsation frequencies (f = 0–7 Hz) and gas velocities (N = 1.1–1.7) were selected in this work. The results showed that gas velocity and pulsation frequency played important role on particle segregation and mixing behavior. The segregation index reached the maximum value at pulsation frequency f = 3.49 Hz and gas velocity N = 1.3 when h = 80 mm, indicating pulsed gas-solid fluidized bed can effectively separate particles of different densities. With the increase of bed height, the standard deviation of separation index decreases, and the optimal frequency moves to the low frequency region. This work provides guidance for the study of segregation and mixing behavior of Geldart D binary particles in pulsed fluidized bed.

Adsorption of Sb(III) from Aqueous Solution by nZVI/AC: A Magnetic Fixed-Bed Column Study.

The effectiveness of nanoscale zero-valent iron(nZVI) immobilized on activated carbon (nZVI/AC) in removing antimonite (Sb(III)) from simulated contaminated water was investigated with and without a magnetic fix-bed column reactor. The experiments were all conducted in fixed-bed columns. A weak magnetic field (WMF) was proposed to increase the exclusion of paramagnetic Sb(III) ions by nZVI/AC. The Sb(III) adsorption to the nZVI and AC surfaces, as well as the transformation of Sb(III) to Sb(V) by them, were both increased by using a WMF in nZVI/AC. The increased sequestration of Sb(III) by nZVI/AC in the presence of WMF was followed by faster nZVI corrosion and dissolution. Experiments were conducted as a function of the pH of the feed solution (pH 5.0–9.0), liquid flow rate (5–15 mL·min−1), starting Sb(III) concentration (0.5–1.5 mg·L−1), bed height nZVI/AC (10–40 cm), and starting Sb(III) concentration (0.5–1.5 mg·L−1). By analyzing the breakthrough curves generated by different flow rates, different pH values, different inlet Sb(III) concentrations, and different bed heights, the adsorbed amounts, equilibrium nZVI uptakes, and total Sb(III) removal percentage were calculated in relation to effluent volumes. At pH 5.0, the longest nZVI breakthrough time and maximal Sb(III) adsorption were achieved. The findings revealed that the column performed effectively at the lowest flow rate. With increasing bed height, column bed capacity and exhaustion time increased as well. Increasing the Sb(III) initial concentration from 0.5 to 1.5 mg·L−1 resulted in the rise of adsorption bed capacity from 3.45 to 6.33 mg·g−1.

Fixed-bed column dynamics of ultrasound and Na-functionalized diatomite to remove phosphate from water.

A continuous fixed-bed column study was used to evaluate phosphate adsorption performance of U-D-Na which was functionalized by the cheap NaCl reagent after simple ultrasonic purification of diatomite. In this work, various effect factors, including flow rate, initial phosphate concentration, and the bed height, on breakthrough performance of fixed column were investigated. Experimental results demonstrated that the breakthrough time declined with the increase of inlet phosphate concentration and feed rate, whereas the increase of bed height turned out to significantly extend the breakthrough time. The dynamic adsorption process could be well fitted by the Thomas model, with a correlation coefficient R2 > 0.9000 under main operating conditions. A thrice loop of effective regeneration was achieved with 0.1 M hydrochloric acid eluent and deionized water. The maximum removal rate for phosphate was more than 95% in the column adsorption process. The results proved that U-D-Na could be used as a better alternative phosphate adsorbent for wastewater in a continuous column sorption process.

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

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

Continuous fixed-bed column study for removal of Congo red dye from aqueous solutions using Nelumbo nucifera leaf adsorbent

ABSTRACT The adsorption of Congo red (CR) dye from aqueous solutions is conducted in a continuous fixed-bed column by using agricultural biomass of Nelumbo nucifera leaf adsorbent. The column performance is evaluated by varying the adsorbent bed height (2.5‒5 cm), influent dye concentrations (10–50 mg L−1), and inlet flow rate (1‒5 mL min−1). Column experimental data confirmed that the breakthrough characteristics of the adsorption system are dependent on bed height, flow rate, and initial adsorbate concentration. The results show that the decolourisation efficiency and equilibrium uptake (qe) of CR decreases with increasing flow rate and increases with increasing bed height and influent adsorbate concentration. The maximum absorption efficiency (83.12%) was obtained using 5 cm bed height, 15 mg L−1 inlet adsorbate concentration, and 1 mL min−1 flow rate. The increased flow rate and initial adsorbate concentration lead to a shorter column exhaustion time. The length of mass transfer zone increased with increasing bed height. Various mathematical models are applied to column experimental data to predict the breakthrough curve and to evaluate the column capacity and kinetic constants of the models. The correlation between the experimental and theoretical data is quantified by calculating the regression coefficients for the Thomas and Yoon–Nelson models, an R 2 ≥ 0.954 at various operating conditions was obtained, which shows that the trend of experimental data fits well and the overall system kinetics are limited by solid-liquid interphase mass transfer. The N. nucifera leaf fine powder adsorbent is proven to be capable of removing CR efficiently from aqueous solutions in continuous fixed-bed systems at low flow rate and higher bed depth and it can be used effectively in wastewater treatment.

Removal of Cr (VI) from aqueous solution by activated charcoal derived from Sapindus trifoliate L fruit biomass using continuous fixed bed column studies.

In this study, the removal of hexavalent chromium from aqueous solution were examined using activated charcoal derived from Sapindus trifoliate L fruit biomass in continuous fixed-bed column studies. The activated S. trifoliate L fruit charcoal was prepared by treating the fruit powder using concentrated nitric acid solution. Experiments were performed to investigate the effect of bed height and initial concentration on the breakthrough and saturation times. The breakthrough and saturation time increases with increase in bed height and initial concentration of chromium solutions. The maximum adsorption capacity of S. trifoliate L charcoal for hexavalent chromium was found to be 1.719 mg/g in the bed height 15 cm and initial concentration 10 mg/L, respectively. Column data required at various conditions were explained using Bohart-Adams and Thomas model. Two models were found to be suitable to describe the definite part of the dynamic behaviour of the column with regard to bed-height and initial concentration of hexavalent chromium. On comparison of Adjusted R2 and estimated standard error, the Thomas model was found to best-fitted model and can be used to predict the adsorption of the hexavalent chromium in fixed-bed column studies. Activated S. trifoliate L fruit charcoal was characterised by SEM-EDX and FTIR analysis.

Batch and Continuous Chromate and Zinc Sorption from Electroplating Effluents Using Biogenic Iron Precipitates

Nanoparticles of iron precipitates produced by a microbial consortium are a suitable adsorbent for metal removal from electroplating industry wastewaters. Biogenic iron precipitates were utilized as adsorbents for chromate and zinc in batch conditions. Furthermore, the iron precipitates were embedded in alginate beads for metal removal in fixed-bed columns, and their performance was evaluated in a continuous system by varying different operational parameters such as flow rate, bed height, and feeding system (down- and up-flows). The influence of different adsorption variables in the saturation time, the amount of adsorbed potentially toxic metals, and the column performance was investigated, and the shape of the breakthrough curves was analyzed. The optimal column performance was achieved by increasing bed height and by decreasing feed flow rate and inlet metal concentration. The up-flow system significantly improved the metal uptake, avoiding the preferential flow channels.

Experimental investigation of spout incoherence in a spouted bed

Spout incoherence is a typical instability phenomenon in spouted beds, in which the particles in the spout region move upward as groups, leading to poor spouting stability and efficiency. In this paper, the moving particle blockage in the spout region is measured to quantify the spout incoherence for the first time, by means of depicting the regularity, frequency and particle blockage length of the spout incoherence phenomenon. Specifically, the particle blockage is quantified using the particle concentration obtained by image processing method based on intensity differences between gas and solid phase in the spout centreline. The centreline of the spout channel is located by the particle velocity vector field. The method is validated by visual observation and frequency analysis. Then, the effects of static bed height and spouting velocity on the spout incoherence are investigated, respectively. The results show that the main features of spout incoherence, including frequency, regularity and particle blockage length, remain constant with varying spouting velocity in the investigated range. The results reveal that the static bed height has significant effects on the spout incoherence, and the increasing bed height reduces the frequency and particle blockage length of spout incoherence. This work quantifies the spout incoherence and unveil many interesting mysteries of the spout incoherence in spouted beds.

An Eco-friendly and Economical Approach for Removal of Remazol Blue, Malachite Green and Rhodamine B Dyes from Wastewater using Bio-char Derived from Chlorella Vulgaris Biomass

Background::Rapid urbanization and industrialization has led to depletion of water resource and generation of enormous amount of wastewater. One among them is textile industry which discharge huge amount of dye wastewater into aquatic environment.Methods::This study deals with adsorption of Remazol blue, Malachite green and Rhodamine B dyes into bio-char derived from Chlorella vulgaris biomass cultivated from municipal wastewater. Column studies were performed to depict the industrial usage of bio-char for treatment of large quantity of wastewater. Effect of temperature, time, pH, dye concentration and adsorbent dosage on dye removal was studied in batch process.Results::The best batch adsorption conditions are temperature (25⁰C), time (60min), pH (7), dye concentration (100ppm) and adsorbent dosage (1g) with ± 5% for all three dyes. Dye removal percentage of bio-char increased with increased in adsorbent dosage to 94.5%, 88.2% and 90.1% for Remazol blue, Malachite green and Rhodamine B dyes at 1g/L adsorbent dosage. Freundlich isotherm exhibited correlation coefficient (R2) values of 0.99, 0.98 and 0.99 for Remazol blue, Malachite green and Rhodamine B dyes respectively. Kinetic studies revealed that all three dyes followed pseudo first order model. Increase in column bed height resulted in increased dye removal percentage since increase in bed height resulted in increase in bio-char quantity with more number of surface area.Conclusion::From the study, it can be concluded that Bio-char was the economical and eco-friendly alternative adsorbent for wastewater treatment process. Bio-char reusability study revealed that it could be used for 3-4 consecutive cycles.

Fixed-bed column adsorption performance for ammonia removal using adsorbent from zeolite

A study on the performance of fixed-bed column adsorption using natural zeolite Sarulla for ammonia removal has been carried out. The effect of important parameters namely bed height on the breakthrough curve and adsorption performance has been investigated in laboratory scale experiments. The study results show that the adsorption efficiency increases with increasing bed height. These results reveal that the throughput volume of aqueous solution increases with increasing bed height, due to the availability of more adsorption sites and a longer time to reach saturation. Adsorption kinetics were analyzed using the Thomas and Yoon and Nelson kinetics models. The kinetics data can be described well using these two models. The maximum adsorption capacity (qo) was determined using the Thomas kinetics model, the ammonia value was 279.3589 mg / g. However, the study results show that the value of qo decreases with increasing ammonia bed height. For Yoon and Nelson’s models, the rate constant decreases with increasing bed height. The length of time required for 50% of the breakthrough increases with increasing bed height. The kinetics data can be correlated well using both models.

Cost-effective composite prepared from sewage sludge waste and cement kiln dust as permeable reactive barrier to remediate simulated groundwater polluted with tetracycline

Use of sewage sludge (SS) and cement kiln dust (CKD) to prepare hydroxyapatite nanoparticles through a chemical reaction between phosphate and calcium ions extracted respectively, from these wastes represents the novelty of this work. The nanoparticles were deposited on the filter cake (FC) remaining after extraction to produce “Hydroxyapatite Coated Filter Cake (HAP-CFC)”. The removal efficiency of tetracycline onto HAP-CFC was surpassed 90% at best conditions of time (2 h), pH 5, and dosage (0.4 g/50 mL) respectively, for 50 mg/L initial concentration of tetracycline at a speed of 200 rpm. The pseudo-second-order model described well the kinetic measurements and, accordingly, depicts that chemisorption will predominate the adsorption process. Also, the Langmuir model was an ideal relationship for describing the adsorption data. The maximum adsorption capacity for tetracycline onto HAP-CFC was 43.5 mg/g and this value had decreased to 41.5 mg/g for mixture of 10% sand and 90% HAP-CFC applied in the column tests. The X-ray diffraction (XRD) analysis proved the precipitation of nano-hydroxyapatite onto FC due to the appearance of new peaks at the 2 θ values of 21.21, 29.76 and 48.86. Also, all characterization tests showed that the electrostatic attraction, intra-particle diffusion and surface complexation are predominant mechanisms for removal of tetracycline onto HAP-CFC. Theoretical predictions of effluent normalized concentrations with measurements for packed bed revealed a propagation delay of plume front, resulting from the reduction of flow rate and inlet concentration with increase of bed height.

Packed bed column adsorption of phenol onto corn cob activated carbon: linear and nonlinear kinetics modeling

In the present study, linear and nonlinear regression analysis for packed bed column adsorption of phenol onto corn cob activated carbon was investigated. The activation of the corn cob provided the activated carbon with enhanced surface area and micropore volume of 903.7 m2/g and 0.389 cm3/g respectively. The analysis of the physical properties of the corn cob activated carbon (CCAC) revealed that it contained 33.47% of fixed carbon, 5.82% of ash content, 18.01% of volatile matter, 0.63 g/mL of bulk density, 5.50% of moisture content, and a pH of 6.30. SEM images indicated the presence of interspatial pores within the matrix of the adsorbent, while the FTIR analysis revealed that the major functional groups in CCAC were alkanol, alkanes, alkyls, carboxylic acids, ethers, esters, and nitro compounds. The effect of the process parameters influencing the dynamic adsorption process was investigated at flow rates (9–18 mg/min), initial phenol concentration (100-300 mg/L), bed height (5–10 cm), and particle size (300-800 µm). The breakthrough time and adsorption capacity increased with an increase in bed height but decreased with an increase in flow rate, initial phenol concentration, and particle size. At optimum conditions of bed height 10 cm, initial phenol concentration, 100 mg/L, flow rate, 9 mL/min, and particle size 300 µm, the adsorption capacity at breakthrough (qb), adsorption capacity at saturation (qs), volume of effluent treated at saturation (Veff,s), length of mass transfer zone (MTZ), adsorbent exhaustion rate (AER), fractional bed utilization (FBU) factor, Reynolds number (Re), Sherwood number (Sh), and the percentage phenol removal (Ys) were 2.143 mg/g, 8.570 mg/g, 12.96 L, 7.50 cm, 30.86 g/L, 0.25, 17.93, 28.85, and 66.13% respectively. The linear and nonlinear regression analysis of the Thomas, Adams-Bohart, and Wolborska models fitted better with the experimental data than the Yoon–Nelson model. Generally, the nonlinear regression proved to be a better tool for dynamic adsorption model analysis as the model parameters generated by the technique have a better correlation with the experimental data when compared to those obtained via linear regression. Conclusively, this study has shown that CCAC can successfully be used for the removal of phenol from aqueous solutions. It also demonstrated that the modeling approach significantly affects the outcome of the analysis of dynamic adsorption systems.

Modeling and computational fluid dynamic simulation of acetaminophen adsorption using sugarcane bagasse

In this work, the mathematical modeling of acetaminophen (ACT) removal in a fixed-bed adsorption column using sugarcane bagasse (SB) as adsorbent was studied. Experimental data were fitted to six analytical models: Thomas, modified dose-response, Yoon-Nelson, Bohart-Adams, Wang, and Wolborska. Three experimental tests were carried out at 2.5 mL/min of flow rate, 57 mg/L of ACT concentration, and bed heights of 23, 33, and 43 cm. The predicted breakthrough curve by modified dose-response model agreed acceptably (R2 > 0.91) with experimental curves. Besides, a computational fluid dynamic (CFD) model was developed to simulate and analyze the ACT concentration inside of the adsorption column and the wall channeling effect. The simulated breakthrough curve had a good reproducibility with experimental data, the maximum error between experimental and predicted points was 7.03%. In addition, the CFD model shows a high mass transfer zone and a slow adsorption rate in all three tests of ACT adsorption; the mass transfer zone grew as the bed height increased, whereas the wall channeling effects disappeared with increasing bed height. Also, the diffusion resistances and axial dispersion phenomenon were relevant. The results of this research work demonstrate the usefulness of computational fluid dynamics analysis to understand better the adsorption process.

Modelling of a Heated Gas-solid Fluidised Bed using Eulerian Based Models

ABSTRACT An Eulerian-Eulerian granular model was used to simulate the flow and heat transfer through a heatedgassolid fluidised bed. The primary objective of the study was to determine whether the Eulerian-Eulerian granular model adequately predicts the chamber pressure drop, temperature, and bed expansion through the bed. The model predictions were assessed and validated for various flow-regimes, namely the fixed-bed, smooth, bubbling fluidisation, and the maximum fluidisation regimes. This was done on an experimental scale heated gas-solid fluidised bed. However, the results are generalisable for heated gas-solid fluidised beds when the flow is laminar. Numerical models were created using Computational Fluid Dynamics (CFD). The CFD-model predictions were investigated, analysed, and compared to experimental results. Basic experiments were carried out to obtain varying hydrodynamic characteristics. The results showed a slight overprediction of pressure drop and bed expansion, however, the results were still in close agreement with the experiment. In contrast, underprediction of chamber temperatures were obtained. Based on the results of this study, it is recommended that the Eulerian model be used to predict dynamic flow behaviour. Before minimum fluidisation, when in a fixed bed regime, pressure drop in the chamber increases with no increase in bed height. No visible bubbles were present in the fixed bed regime. When fluidisation has been reached, the bed height rises whereas the pressure drop tends to a constant value. Bubble size increases with chamber height and increased superficial velocities. Bubble speed increased with increased chamber height. With increased superficial velocity, the chamber temperatures increase to a maximum temperature of326.65 K with an initial heating element temperature of373.15 K. However, when excessive heat is present in the gas-solid fluidised bed, other methods that sufficiently incorporate particle-particle interactions and bubble-bubble interactions, are recommended. An investigation should be lent to bubble-bubble interactions in the fluidised beds with relation to heat transfer. Additional keywords: Heated fluidised bed, computational fluid dynamics, CFD, Eulerian, granular, fluidisation, gas-solid

Study of the effect of particle diameters on two-phase (air-solid) fluidization bed hydrodynamics

Computational fluid dynamics (CFD) is executed through a model of gas-particle two phase based on fluidized bed. The influences of particle size and inlet velocity on the fluidization process are discussed. The results showed that at the time of the simulation, the height of solid particles inside the pipe increased as the air velocity increased, the pressure drop for the three particle sizes during time is near and constant, Also showed the volume fraction increases as the velocity of the inlet air increases. As with the voidage, it decreases and then increases slightly as the velocity increases, but with a large diameter is the opposite. The volume fraction decreases with increasing bed height. Finally, the model can predict the shape of radial-direction particle patterns.

Continuous adsorptive removal of glimepiride using multi-walled carbon nanotubes in fixed-bed column.

Water pollution by emerging pollutants such as pharmaceutical and personal care products is one of today's biggest challenges. The presence of these emerging contaminants in water has raised increasing concern due to their frequent appearance and persistence in the aquatic ecosystem and threat to health and safety. The antidiabetic drug glimepiride, GPD, is among these compounds, and it possesses adverse effects on human health if not carefully administered. Several conventional processes were proposed for the elimination of these persistent contaminants, and adsorption is among them. Therefore, in this study, the adsorptive removal of GPD from water using multi-walled carbon nanotubes (MWCNT) supported on silica was explored on a fixed-bed column. The effects of bed-height, solution pH, and flow rate on the adsorptive removal of GPD were investigated. The obtained adsorption parameters using Sips, Langmuir, and Freundlich models were used to investigate the continuous adsorption. The results showed that the drug removal is improved with the increasing bed height; however, it decreased with the flow rate. The effect of pH indicated that the adsorption is significantly affected and increased in acidic medium. The convection-dispersion model coupled with Freundlich isotherm was developed and used to describe the adsorption breakthrough curves. The maximum adsorption capacity (qm) was 275.3 mg/g, and the axial dispersion coefficients were ranged between 3.5 and 9.0 × 105 m2/s. The spent adsorbent was successfully regenerated at high pH by flushing with NaOH.

Dry beneficiation of coal on KAT air table

ABSTRACT Dry gravity-based separation processes such as pneumatic jigs and tables generally use density stratification of feed material with light and dense particles to achieve separation. Therefore, it is necessary to enhance the stratification of the particles in the separation bed. The main purpose of this work was to evaluate the use of an intrinsic autogenous separation medium of feed coal for the dry separation process by increasing the separation bed height in a pneumatic table separator. Tests were conducted and the results showed that increased bed height and an autogenous separation bed resulted in a significant benefit for the separation efficiency. Bituminous coal samples with high-density impurities containing 48.9% feed ash were reduced to 7.7% ash content with a combustible recovery of 89.7%. In the case of higher density anthracite coal, the experimental separator was able to reduce feed ash 50–60% to 26–28% in the product.

Numerical simulation of gas–solid heat transfer characteristics of porous structure composed of high-temperature particles in moving bed

Blast furnace slag is the main by-product of ironmaking, and its waste heat recovery is essential for energy saving. As an excellent gas–solid reactor, moving bed has wide application prospects in waste heat recovery. Nevertheless, most researchers are currently keen on the thermal characteristics of fluidized bed. There is no clear conclusion for gas–solid heat transfer mechanism of moving bed, especially the heat transfer characteristics of particles with multiple particle size distribution. Therefore, in this paper, a CFD-DEM coupling method is used to simulate waste heat recovery process of the blast furnace slag in the moving bed. The gas–solid heat transfer characteristics of a porous structure composed of different particle size distribution systems were studied. The results show that the binary particle size mixing system has the best heat transfer effect. Moreover, the waste heat recovery rate decreases with the increasing initial temperature and mass flow rate of particles, while increases with the increasing bed height and gas flow rate. Based on these results, an empirical correlation of the comprehensive heat transfer coefficient is obtained using the dimensional analysis. The study clarifies multiphase flow and heat transfer characteristics in the moving bed of the porous structure composed of high-temperature slag particles with multiple particle size distribution, and provides a theoretical basis for the next-step development of a high-efficiency gas–solid heat transfer moving bed.

Activated carbon from a specific plant precursor biomass for hazardous Cr(VI) adsorption and recovery studies in batch and column reactors: Isotherm and kinetic modeling

The main aim of this work was the development of the chemical activated carbon (AC) method from specific wood biomass, i.e., Eucalyptus camaldulensis sawdust (ECS), and this AC is proposed as a promising alternative treatment for hazardous Cr(VI) from aqueous solution. ECS waste sawdust was carbonized in two stages, i.e. 170 °C for 60 min, followed by 500 °C for 120 min under the continuous steam of nitrogen gas, and rated as an efficient method with H3PO4 activation (>80% Cr(VI) removal). Finally, activated carbon-Eucalyptus camaldulensis sawdust (AC-ECS) was selected for batch and column reactor studies and different influencing parameters, such as contact time, pH, temperature, initial Cr(VI) metal concentration, particle size, and bed height were optimized. AC-ECS was characterized through analysis by SEM, EDX, FTIR, and BET. Cr(VI) adsorption was found to be highly pH-dependent, i.e., 87% at pH 3.0. AC-ECS adsorption mechanism for Cr(VI) with experimental and maximum predicted adsorption capacities of 104 and 125 mg g−1, respectively, was best described by the Langmuir isotherm (R2 = 0.999) and pseudo-second-order kinetics (R2 = 0.999). The column study showed an improvement in the breakthrough curve time from 5595 to 12,270 min, with the respective increase of bed height from 5 to 15 cm, respectively. Column breakthrough data was found to be well fitted to the bed depth service time model. Current batch and column studies indicate that freshwater contamination with Cr(VI) can be managed by upscaling the AC-ECS as an efficient treatment solution.