Fixed-bed Column System Research Articles

Screening of metal-modified biochars for practical phosphorus recovery

The utilization of metal-modified biochars (MBCs) for practical phosphorus recovery has attracted significant research interest recently. However, the optimal choice of metals and modification methods for MBCs remains unclear. This study addresses this gap by comparing the phosphate adsorption capabilities of various MBCs using real municipal wastewater. The results show that zinc-modified biochar exhibits superior phosphate adsorption compared to biochars modified with calcium, magnesium, aluminum, and iron. Specifically, zinc-modified biochar prepared through metal-mediated biomass pyrolysis with alkaline soaking (ZnBC-OH) demonstrates the highest adsorption capacity, achieving 36.6 mg P/g in wastewater with a phosphate concentration of 5 mg P/L. This performance surpasses that of previously reported non-lanthanide modified biochars and is comparable to lanthanide-modified biochars. Mechanistic investigations reveal that the exceptional performance of ZnBC-OH is due to the presence of highly dispersed ZnO sites, which facilitate the formation of Zn3(PO4)2·4H2O precipitation, effectively retaining phosphate. Furthermore, a techno-economic analysis indicates that using ZnBC-OH in a fixed-bed column system can reduce phosphate levels from 6 mg L−1 to below 0.5 mg L−1 at a cost of 1.834 USD per ton of secondary treated wastewater, underscoring its promising application potential.

Citric acid functionalized chitosan hydrogel beads for enhanced Cr(VI) removal: Experimental assessment and COMSOL modelling of adsorption in a fixed-bed system

Chitosan hydrogel beads (CHB) and cross-linked CHB functionalized with tricarboxylic citric acid (CA-GLA-CHB) were synthesized and used for the removal of Cr(VI) from aqueous solutions in batch and dynamic adsorption systems. Applicability of COMSOL Multiphysics software as a tool for predictive modelling of column dynamics using a minimum set of experimental parameters was tested and compared with experimental results. Batch experiments demonstrated that CA-GLA-CHB showed almost 20% higher adsorption capacity and wider operational pH range compared to non-functionalized CHB. In a dynamic system, CA-GLA-CHB was used as column packing material and the column dynamics was investigated at different conditions. The breakthrough and exhaustion time of the column increased with an increase in bed height and a decrease in feed flow rate and initial Cr(VI) concentration. Computational modeling by COMSOL software with implemented Advection-Dispersion-Reaction (ADR) equation was used to simulate breakthrough curves for the applied dynamic system in order to validate the possibility of its application for process design in the scaled-up fixed-bed column systems for wastewater treatment. The simulated breakthrough curves of Cr(VI) adsorption matched well with the experimental, thus proving that COMSOL Multiphysics software can be used for scaling-up fixed-bed column systems packed with low-cost and effective CA-GLA-CHB bioadsorbent.

Equilibrium adsorption, kinetic, thermodynamic, and breakthrough curves modelling of acetaminophen on Elaeagnus Angustifolia L. seeds-based granular activated carbon

ABSTRACT The widespread presence of pharmaceutical compounds as emerging environmental contaminants in aquatic environments has become a significant concern in recent years. In this study, synthesised granular activated carbon (GAC) derived from Elaeagnus Angustifolia L. seeds was utilised as an adsorbent to remove an emerging contaminant, acetaminophen (commercially known as paracetamol). The operating conditions for the chemical synthesis of the GAC, utilising ZnCl2 as an activating agent, included an impregnation ratio of 1:1, carbonisation at 500°C for 1 hour, and a heating rate of 5 °C/min. The efficacy of this adsorbent was assessed through both batch and fixed-bed column adsorption experiments under various operational parameters, including adsorbent mass (1–6 g/L), contact time, pH (2–10), temperature (20–60°C), inlet acetaminophen concentration (20–150 mg/L), and flow rate (0.5–1.5 mL/min). The results indicate that acetaminophen was better adsorbed in its neutral form rather than in its dissociated state. The findings also revealed that both the Langmuir (two-parameter) and Sips (three-parameter) models provided the best fit for the static adsorption equilibrium data. Furthermore, kinetic analysis indicated that the experimental data were best modelled by the Elovich model and governed by both external diffusion and intraparticle diffusion mechanisms. Therefore, the Yan-Viraraghavan model provided a good fit for the experimental breakthrough curves under various operating conditions. However, the adsorbed amounts of acetaminophen obtained from the column experiment indicated that the high-adsorbed amount of 204.11 mg/g was achieved with an inlet acetaminophen concentration of 150 mg/L, a bed depth of 6 cm, and a flow rate of 0.5 mL/min. These results highlight the potential of the synthesised GAC as a promising adsorbent for pharmaceutical wastewater treatment using fixed-bed column systems.

Utilization of Fly Ash Palm Oil Mill Waste as an Adsorbent of Methylene Blue in a Fixed Bed Column System by Using Response Surface Methodology

Palm kernel shell combustion waste in boiler units called fly ash (FA) is a low-cost alternative material as an adsorbent. FA contains high levels of silica (SiO2) and aluminium oxide (Al2O3). The content of both compounds is an important component as an adsorbent. FA was used to absorb methylene blue (MB) continuously from synthetic dye wastewater. The study was conducted by continuous system process optimization using Response Surface Methodology (RSM) Box-Behnken design. MB was flowed on a set of fixed-bed adsorption columns with independent variables in this study are X1 (bed height; 8, 12, 16 cm), X2 (contact time; 90, 120, 150 min) and X3 (flow rate; 2, 4, 6L/min). The dependent variables were Y1 (removal efficiency) and Y2 (adsorption capacity) with matrix design by Box-Behnken. Optimisation of MB removal in this study was obtained at X1 = 16 cm, X2 = 150 min and X3 = 2 L/min with removal efficiency of 98.45% and adsorption capacity of 0.115 mg/g. FA pores according to SEM analysis were obtained at 1-2 µm. Likewise, the results of EDX analysis showed that there were N and Cl atoms in FA after the adsorption process. This shows that FA is able to adsorb MB.

A novel lignin-steel sludge composite for dyes adsorption from water: Surface functionalities and structural alteration mechanisms

The study focuses on fabricating and utilizing a lignin-steel sludge magnetic carbon composite (SLNa) to efficiently remove two dyes from an aqueous medium. The SLNa composite was fabricated through a simple two-step strategy involving the activation and thermal treatment of lignin and steel sludge. The SLNa possessed lignin and steel sludge starring properties, viz. abundant surface functionalities, graphitic carbon matrix, and magnetic characteristics. The synergistic combination of lignin and steel sludge resulted in composite's high adsorption potential for Methylene Blue (MB; 153.92 mg/g) and Acid Orange 7 (AO7; 64.84 mg/g) in batch mode. Additionally, the rapid adsorption kinetics and effective dye removal for MB (> 99 %) and AO7 (72 %) from simulated effluent revealed the potential of fabricated adsorbent for water remediation. Furthermore, the composite's applicability for continuous adsorption was also evaluated through a series of dynamic flow experiments using fixed-bed column systems. The demonstrated efficacy of SLNa, viz., 48.18 and 15.00 mg/g for MB and AO7, respectively, at high adsorbent loading and lower dye concentrations, highlights its potential for scalable water treatment applications. Thus, the versatility and effectiveness of the novel composite underscore its potential for practical application in both batch and continuous water remediation processes.

MgO modified sucrose-derived porous carbon composite for fluoride adsorption

Fluorine is an essential trace element for human skeletal and teeth health, while excess intake of fluoride induces many kinds of diseases. The national standard for fluoride concentration in drinking water quality in China is less than 1.0 mg L−1. Developing effective and environmental friendly approach to remove fluoride from water especially with high fluoride concentration in low cost is quite necessary. Herein, fluoride removal by MgO modified sucrose-derived porous carbon composite (MPCC) in batch and fixed-bed column systems was studied. The maximum fluoride adsorption capacity of MPCC was 26.6 mg g−1 at 25 ℃. Common anions Cl-, SO42- and NO3- showed negligible effect on fluoride removal, while a negative impact was observed with co-existence of HCO3-. The fluoride adsorption kinetic was well fitted with Langmuir adsorption model and the adsorption mechanism was ion exchange reaction between -OH and F-. The fluoride concentration can be successfully lowered down to the acceptable level of environmental standard for high concentration influent fluoride. The MPCC composite exhibited excellent regeneration performance, endowing it as promising adsorbent for remediation water with fluoride pollution.

New insights on antimony removal and recovery from water and wastewater using iron-coated cork granulates: Desorption on batch and fixed-bed column systems

This work investigated Sb adsorption–desorption using iron-coated cork granulates (ICG) in both batch and continuous modes to evaluate the materiaĺs adsorption and regeneration performance, as well as the possibility of antimony recovery. A fixed-bed column filled with ICG, demonstrated maximum adsorption capacities of 13 ± 2 mg g−1 and 10 ± 1 mg g−1 for Sb(III) and Sb(V), respectively, at pH 3. ICG was able to remove Sb within the WHO guideline of 20 μg/L at pH 6. Among the different classes of eluents tested for Sb(V) desorption, the acids achieved the highest desorption rates − 81 ± 9 % and 66 ± 8 % for HCl 1 M and ascorbic acid 0.1 M, respectively. The desorption kinetics showed that HCl 1 M reached equilibrium in 4 h, but ascorbic acid 0.1 M took 16 h. This work presents an ecological emerging solution for antimony removal and recovery from water and wastewater.

Fluoride Removal from Aqueous Solution Using Thermally Treated Dolomite Powder as Adsorbent in the Fixed Bed Column

Abstract Aim: The objective of this paper was to investigate the ability of thermally treated dolomite powder (TTDP) to remove fluoride ions from wastewater in a fixed bed column system, and to understand how different operating parameters such as bed height, initial fluoride concentration, and flow rate of influent affected the performance of the system. Materials and Methods: The researchers used several different models to analyze the data collected from the column experiments, and they also characterized the TDP adsorbent using field emission scanning electron microscopy and X-ray diffraction in order to understand its surface morphology. Results: Adsorption capacity increased with the initial fluoride concentration and decreased with bed height. Saturation concentration increases with an initial concentration of fluoride and decreases with bed height and flow rate of influent. Error analysis between experimental results and model results has been done using different predefined error functions. Regeneration of TDP adsorbent is done using a 1N NaOH solution. Conclusions: The breakthrough time increases with a low flow rate of 15 ml/min, low influent concentration of 5 ppm, and higher bed depth of 20 cm. The experimental data from the fixed bed column for fluoride removal are well fitted with all classic models, and the coefficient of regression is close to unity. Regeneration studies have shown that the adsorbent (TTDP) can undergo three cycles of regeneration.

Multiporous ZIF-8 carbon/cellulose composite beads: Highly efficient and scalable adsorbents for water treatment

Metal–organic framework (MOF) particles are one of the most promising adsorbents for removing organic contaminants from wastewater. However, powder-type MOF particles face challenges in terms of utilization and recovery. In this study, a novel bead-type adsorbent was prepared using activated carbon based on the zeolitic imidazolate framework-8 (AC-ZIF-8) and a regenerated cellulose hydrogel for dye removal. AC-ZIF-8 particles with a large surface area were obtained by carbonization and chemical activation with KOH. The AC-ZIF-8 powders were efficiently immobilized in hydrophilic cellulose hydrogel beads via cellulose dissolution/regeneration. The prepared AC-ZIF-8/cellulose hydrogel (AC-ZIF-8/CH) composite beads exhibit a large specific surface area of 1412.8 m2/g and an excellent maximum adsorption capacity of 565.13 mg/g for Rhodamine B (RhB). Moreover, the AC-ZIF-8/CH beads were effective over a wide range of pH, temperatures and for different types of dyes. These composite beads also offer economic benefits through desorption of dyes for recycling. The AC-ZIF-8/CH beads can be produced in substantial amounts and used as fillers in a fixed-bed column system, which can purify the continuous inflow of dye solutions. These findings suggest that our simple approach for preparing high-performance adsorbent beads will broaden the application of dye adsorbents, oil–water separation, and catalysts.

Removal of tetracycline by natural and iron-modified orange peel from aqueous solutions: processes in batch, column, and mechanism

ABSTRACT Natural (OP) and iron modified orange peel (Fe-OP) were used for the removal of tetracycline from aqueous solutions in batch and fixed bed column systems. The adsorbents were characterized by infrared spectroscopy (IR) and the morphologies of the surfaces before and after tetracycline removal were determined by scanning electron microscope and the elemental analysis was performed by X-ray dispersive spectroscopy (EDS). The kinetic behaviour showed that the equilibrium was reached in 24 and 10 h for OP and Fe-OP respectively, the data were adjusted to both the pseudo second order and intraparticle diffusion models which indicate a chemisorption mechanism and the adsorption process is controlled by the intraparticle diffusion process. The isotherms showed that the adsorption capacity was eight times higher for Fe-OP than OP and the data were best fitted to the Freundlich model indicating that the materials are heterogeneous. The effect of flow rate, influent concentration and adsorbent mass were determined in the column system. The data were adjusted to the Thomas, Adams–Bohart and Yoon-Nelson models, and the best adjustment of data was with the first one. The adsorption capacities in the column system were about half of those obtained in the batch system. These adsorbents show good properties for the removal of tetracycline from water.

Competitive heavy metal adsorption on pinecone shells: Mathematical modelling of fixed-bed column and surface interaction insights

Pinecone shells are assessed as a cost-effective biosorbent for the removal of metal ions Pb(II), Cu(II), Cd(II), Ni(II), and Cr(VI) in a fixed-bed column. Influent concentration, bed height, and flowrate are studied to improve efficiency. The breakthrough data is well fitted by the Sips adsorption model, suggesting a surface complexation mechanism, with maximum adsorption capacities of 11.1 mg/g for Cu(II) and 66 mg/g for Pb(II).In multimetal solutions, the uptake sequence at breakthrough and saturation is Pb(II) > Cu(II) > Cd(II). Characterization via FTIR and XRD reveals carboxyl and hydroxyl functional groups interacting with metal ions. Ca(II) does not compete with Pb(II), Cu(II), and Cd(II) adsorption, highlighting the ability of pinecone to adsorb heavy metals via surface complexation. Its application in the treatment of industrial effluents containing Cu(II), Ni(II), and Cr(VI) is explored.The study investigates bed media regeneration via eluting adsorbed metal ions with hydrochloric acid solutions. The potential of pinecone shells as an efficient biosorbent for removing toxic metal ions from industrial wastewater is emphasized. These findings enhance our understanding of the adsorption mechanism and underscore the fixed-bed column system's applicability in real-world scenarios, addressing environmental concerns related to heavy metal contamination of industrial effluents.

Mass transfer studies on the solvent-free lipase-catalyzed partial hydrolysis of palm oil in packed-bed reactor

Packed-bed reactor (PBR) is widely employed for enzyme-mediated reactions at an industrial scale because the reactor configuration enables reusability of the biocatalyst with ease, thereby reducing the overall operating expenses. However, mass transfer limitation remains a key challenge in fixed-bed column systems, especially at large scale. Therefore, the present study investigated the external mass transfer effects on solvent-free lipase-catalyzed partial hydrolysis reaction and aimed to develop a mass transfer model for the operation. The influence of volumetric flow rate, one of the crucial operating parameters affecting the external mass transfer resistance, was examined. Results demonstrated increasing the flow rate led to an increase in hydrolysis reaction with the highest reaction rate observed at 5 ml min-1 . A dimensionless mathematical mass transfer model of Colburn factor, JD = K(Re)n-1 which is a function of Reynolds and Schmidt numbers, was then proposed to simulate the enzymatic partial hydrolysis reaction of palm oil in PBR. The mass transfer model was analyzed with different n values and results revealed that the mass transfer correlation of JD=0.92(Re)-0.2 was able to predict the experimental data accurately. The model developed could describe the dominance of mass transfer effects besides providing useful information for the scale-up design of industrial reactor.

Investigation of the removal of color and heavy metal from wastewater using activated sludge continuous system and application of models

In the continuous system studies, the natural state of the activated sludge was used in the fixed bed column and fluidized bed column, and the studies were carried out with the synthetic solution wastewater similar to the metal coating industry. Experiments at operating conditions of bed heights 20 cm, initial Cu2+, Ni2+, and Methylene Blue concentrations of 100 mg/L, pH 5.0 and flow rates 2 mL/min were performed to study the performance of the fixed bed column and fluidized bed column. It is seen that the removal efficiencies of the fixed bed and fluidized bed column are very close to each other. Thomas, Yoon-Nelson and Bohart-Adams models were applied to the data obtained in the fixed bed column system. It has been observed that there is a good agreement between the experimental breakthrough curves and the model predictions. In addition, regeneration of activated sludge with 0.1 M HCl and a reuse experiments were carried out, and it was observed that the efficiency decreased considerably in the second use. The results are promising and shall serve to design the activated sludge based fixed bed column and fluidized bed column to obtain cleaner and sustainable treatment of industrial wastewaters containing Cu, Ni and Methylene Blue.

High removal performance of reactive blue 5G dye from industrial dyeing wastewater using biochar in a fixed-bed adsorption system: Approaches and insights based on modeling, isotherms, and thermodynamics study

In an eco-friendly context, an adsorption study was performed in a fixed-bed column system to remove organic pollutants from dyeing wastewater, testing preliminary theoretical models and reactive blue 5G (RB5G) dye as a reference pollutant and tilapia bone-based biochar as an alternative adsorbent. Adsorption approaches in removing RB5G dye molecules from synthetic solutions were performed to understand better based on a reliable mathematical representation and provide insights and strategies into treating dyeing wastewater. Initial dye concentration, pH, temperature, and stirring velocity were used as process variables to search for maximal capacity in batch mode. Thermodynamic analysis and a series of phenomenological kinetic models were applied to understand and interpret the mechanisms and develop a predictive model for a fixed-bed column adsorption system, trying to minimize the total organic carbon (TOC) in dyeing wastewater. An intraparticle mass transfer resistance model and the Langmuir-BET isotherm better represented kinetic and equilibrium data, respectively. In the Langmuir-BET model context, the first monolayer has systematically changed its predicted Langmuir adsorption capacity from 18 mg g−1 to 31 mg g−1 being favored by the increase in temperature of 30 to 60 °C, respectively, with the lowest Gibbs free energies for the multilayer formation ruled by weak physical interaction. Theoretical values of the breakpoint, full saturation time, and useful column height were well predicted related to their experimental ones, including the better fitting of all adsorption curve patterns in a fixed-bed adsorption column system with an adsorption capacity of 30.4 mg g−1 (at 50 °C) for an inlet of 200 mg L−1 RB5G solution resembling almost the same value found in batch mode (30.9 mg g−1). After treating the dyeing wastewater characterized by 75 mg L−1 RB5G dye, the adsorption capacity of 23.3 mg g−1 was attained with a 12% loss in comparison with the expected one for a synthetic RB5G solution due to adsorptive competition with other organic pollutants. Finally, a final TOC value near 5.0 mg L−1, the maximum allowed for the Brazilian environmental council, was attained with an almost zero RB5G concentration after a 5-h breakpoint.

Assessment of waste hop (Humulus Lupulus) stems as a biosorbent for the removal of malachite green, methylene blue, and crystal violet from aqueous solution in batch and fixed-bed column systems: Biosorption process and mechanism

The discharge of industrial textile waters into water bodies leads to the accumulation of pollutants which are a serious threat to humans and the environment. The development of an efficient adsorbent for the removal of toxic organic dyes from water is of crucial importance. For that reason, this work aimed to elaborate on the potential application of a biosorbent obtained from waste Humulus lupulus stems (Hlup-BA) for the elimination of malachite green, methylene blue, and crystal violet from aqueous solution in batch and fixed-bed column systems. The Hlup-BA was characterized using chemical composition analysis, by determination of particle size distribution, the point of zero charge (pHpzc), SEM, BET, EDS, XRD, and FTIR. Comprehensive analysis of Hlup-BA adsorption efficiency in a batch study showed that at the optimal conditions (e.g. contact time, 120 min; biosorbent dose, 2 g/L; dye concentration, 100 g/L; pH, 8 and temperature, 298 K), even 98.4 %, 98.8 %, and 98.5 % of MG, MB, and CV were removed, respectively. The results showed that the biosorption process followed pseudo-second-order kinetics. The equilibrium data were modeled using Langmuir, Freundlich, Sips, and Dubinnin-Radushkevich biosorption isotherms. High values of Hlup-BA biosorption capacities obtained from Langmuir isotherm were 398.9 mg g−1, 209.8 mg g−1, and 133.2 mg g−1 for MG, MB, and CV, thus proving Hlup-BA as an excellent biosorbent for removal of the tested dyes. The thermodynamic study indicated that the biosorption of these three dyes on Hlup-BA from aqueous solution is an endothermic, spontaneous, and thermodynamically stable process. The proposed mechanism of the biosorption process covers π-π interactions, electrostatic interactions, and hydrogen bonding. Furthermore, the data obtained by modeling in the fixed-bed column were also successfully correlated with the Thomas, Bohart-Adams, and Yoon–Nelson models. The very good fit of the results obtained in this way will greatly contribute to optimizing the pilot-scale operations for future wastewater treatment. Consequently, Hlup-BA can be an effective, cheap, and environmentally friendly biosorbent to eliminate methylene blue, malachite green, and crystal violet dyes from the aqueous solution in batch and column systems.

Experimental Design and Breakthrough Curve Modeling of Fixed-Bed Columns Utilizing a Novel 3D Coconut-Based Polyurethane-Activated Carbon Composite Adsorbent for Lead Sequestration

This study presents a novel polyurethane-activated carbon composite (PACC) as an effective and sustainable adsorbent for treating lead-ion-contaminated waters. The PACC was characterized using Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDX), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer, Emmett, and Teller (BET) surface area analyzer, X-ray Diffraction (XRD), and Thermogravimetric Analyzer (TGA) to evaluate its physicochemical and thermal properties. Furthermore, the PACC was employed in an experimental column adsorption setup to investigate its adsorption performance and to develop a dynamic method suitable for industrial implementation. Parameters such as bed height (50, 100, 150 mm), flow rate (4, 6, 8 mL min−1), pH (2, 4, 6), and initial metal-ion concentrations (10, 50, 100 mg L−1) were examined. The experimental data exhibited strong agreement with the Thomas and Yoon–Nelson models (R2 ≥ 0.96), indicating efficient adsorption mechanisms. Remarkably, the used adsorbent has the potential for facile regeneration without substantial loss in capacity. The PACC demonstrated excellent adsorption performance for lead ions in aqueous solutions in a fixed-bed column system. Thus, the novel PACC material holds the potential for scalable application in industrial settings to address water pollution challenges, especially in regions with uncontrolled effluent discharge.

A mathematical model for ammonium removal and recovery from real municipal wastewater using a natural zeolite

A study was carried out to remove/recover ammonium (NH4+) from residual effluents in tertiary treatment by sorption/desorption processes onto a natural clinoptilolite zeolite (NZ) in batch and fixed-bed column systems. Batch equilibrium and kinetic experiments were performed at different loading of NZ and contact time intervals, respectively. The results obtained in batch were fitted by the Freundlich and Langmuir isotherms and mass action law model. The Freundlich isotherm showed better agreement with experimental data than the Langmuir model. The isotherm studies revealed a type III with a maximum capacity of 2.8 ± 0.2 mg/g at 40 mgNH4+/L. Moreover, the data from the fixed-bed column studies was well fitted by a mass transfer model, considering the intraparticle diffusion resistance given by the linear driving force model (LDF). Finally, the capacity of NH4+ recovery of activated zeolite was measured experimentally and by a robust dynamic desorption model. The column desorption results demonstrated that higher recoveries (92–99.99%) were observed when increasing the flow rate to 0.12 mL/min. The uniqueness of this study is its capability to simulate both the sorption and desorption processes of the naturally derived sorbent for the effective removal and recovery of NH4+-N from real wastewater stream.

High-performance Cu/Mn modified ceramsite as a persulfate activator to degrade oxytetracycline in batch Erlenmeyer flask and continuous-flow fixed-bed column systems: An exploration of its practicability and non-radical mechanisms

Persulfate non-radical oxidation have excellent catalytic capability for degrading specific contaminants in complicated water environments. Nevertheless, the preparation of high-performance activators and their application in actual water treatment in continuous flow mode are still scarce and unsatisfactory. In this work, copper-, manganese-, and copper/manganese-doped ceramsites (Cu–C, Mn–C and Cu/Mn–C), successfully fabricated through a facile impregnation-calcination approach, were characterized and evaluated for their performance to activate potassium peroxydisulfate (PDS) and degrade oxytetracycline (OTC) under different pH, ceramsite dosages, and PDS dosages. Compared with Cu–C and Mn–C, Cu/Mn–C showed the highest OTC degradation rate (0.0264 min−1) via activating PDS with an OTC removal efficiency of 98.2% in 240 min at an initial OTC concentration of 40 mg/L. The removal efficiency of OTC by Cu/Mn–C only decreased to 92.8% after 5 cycles; the activating ability of the used Cu/Mn–C was almost completely recovered through 2 h of calcination at 500 °C. The results of electron paramagnetic resonance and radical quenching suggest that singlet oxygen (1O2) was unveiled to be the dominant reactive oxygen species (ROS) for contaminant degradation, originating from the regrouping of superoxide ions or reduction of active Cu/Mn sites. Synergies between Cu and Mn species to enhance ROS yield were the primary activating mechanisms. Six possible routes of OTC decomposition were inferred. Additionally, Cu/Mn–C behaved excellently in treating an actual wastewater using a continuous flow fixed-bed reactor. It is believed that this novel Cu/Mn–C/PDS system may create a fresh path to design effective and cheap metal-ceramsite hybrid activators for degrading recalcitrant contaminants in the actual application process.

Dynamic Behavior of Pb(II) and Cr(III) Biosorption onto Dead Anaerobic Biomass in Fixed-Bed Column, Single and Binary Systems

The biosorption of lead (II) and chromium (III) onto dead anaerobic biomass (DAB) in single and binary systems has been studied using fixed bed adsorber. A general rate multi- component model (GRM) has been utilized to predict the fixed bed breakthrough curves for single and dual- component system. This model considers both external and internal mass transfer resistances as well as axial dispersion with non-liner multi-component isotherm (Langmuir model). The effects of important parameters, such as flow rate, initial concentration and bed height on the behavior of breakthrough curves have been studied. The equilibrium isotherm model parameters such as maximum uptake capacities for lead (II) and chromium (III) were found to be 35.12 and 23.84 mg g-1 respectively. While pore diffusion coefficients (Dp) were obtained to be 7.23×10-11 and 3.15×10-11 m2 s-1 for lead (II) and chromium (III) respectively from batch experiments. The results show that the general rate model was found correct for describing the biosorption process of the dynamic behavior of the DAB adsorber column.

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.