Nelson Model Research Articles

Treatment of fluoride-contaminated water in a prototype adsorption unit using zirconium-activated carbon nanocomposites

ABSTRACT Zirconium-activated carbon nanocomposites (ZANC) are found to have high fluoride removal capacity and thus used as an adsorbent to perform column studies. The adsorbent was characterised using SEM-EDS and FTIR before and after the adsorption of fluoride. A packed bed adsorber prototype of 1 m length was fabricated to carry out defluoridation studies. The effect of varying initial fluoride concentration (2.5–10 ppm) and bed height (6–14 cm) was studied. The maximum fluoride removal was found to be 29.4% and uptake capacity was 4.72 mg/g at an initial fluoride concentration of 10 ppm, flow rate of 2 LPM, and bed height of 14 cm for synthetic samples. The Thomas, Yoon–Nelson and Bed Depth Service Time (BDST) models were employed and their results confirmed the experimental findings. The maximum fluoride adsorption capacities obtained from the Thomas model are 1.9 mg/g and from the BDST model, the N value was 20.979 mg/cm3. Regeneration studies were performed and found that the adsorbent can be regenerated for three cycles. Column studies were also performed using real-field groundwater samples collected from Pavagada of Tumakuru district. All the tested parameters of the treated water were found to be within the permissible limit.

Kinetics and Mechanism Study of Different Types of Surface‐Imprinted Polymers for CO2 Adsorption

ABSTRACTThe increased level of CO2 in the atmosphere has led to global warming and climate change. To mitigate these problems, solid adsorbents have become attractive materials for capturing excess CO2 in the post‐combustion method. Molecularly imprinted polymer (MIP) can be applied to prepare highly selective adsorbents that could capture CO2 molecules. The MIP was prepared using the surface imprinted polymer technique in this preliminary work. Only two types of support materials were used (graphite and silica gel) to screen the best support material that could enhance the CO2 adsorption capacity of the resulting adsorbent, which was analyzed using a fixed‐bed column reactor. Graphite‐imprinted polymer (GMIP) was found to be a good potential for CO2 adsorption. The Avrami model best described the adsorption system, while the fixed‐bed curve data fit the Yoon–Nelson model well. The semi‐empirical method was used to assess the interaction mechanism of the molecularly imprinted polymer with CO2 during adsorption. This investigation involved testing four different ratios of the template complex to functional monomers. The ratio of 1:4 (CO2:Allylthiourea) demonstrated the highest binding energy, with a higher formation of hydrogen bonds. Film diffusion and intraparticle diffusion were the main rate‐limiting steps that played vital roles at different stages of CO2 adsorption. This preliminary work has enhanced the development of MIP for CO2 adsorption and showcased the integration of computational approaches in tailoring specific MIPs.

Dead Fuel Moisture Content Reanalysis Dataset for California (2000–2020)

This study presents a novel reanalysis dataset of dead fuel moisture content (DFMC) across California from 2000 to 2020 at a 2 km resolution. Utilizing a data assimilation system that integrates a simplified time-lag fuel moisture model with 10-h fuel moisture observations from remote automated weather stations (RAWS) allowed predictions of 10-h fuel moisture content by our method with a mean absolute error of 0.03 g/g compared to the widely used Nelson model, with a mean absolute error prediction of 0.05 g/g. For context, the values of DFMC in California are commonly between 0.05 g/g and 0.30 g/g. The presented product provides gridded hourly moisture estimates for 1-h, 10-h, 100-h, and 1000-h fuels, essential for analyzing historical fire activity and understanding climatological trends. The methodology presented here demonstrates significant advancements in the accuracy and robustness of fuel moisture estimates, which are critical for fire forecasting and management.

Novel utilization exploration for the dephosphorization waste of Ca–modified biochar: enhanced removal of heavy metal ions from water

Phosphorus-modified biochar has been proven to enhance the precipitation and complexation of heavy metal ions from wastewater. However, the current modification methods require large amounts of exogenous P and have high energy consumption. Hence, this study proposes and analyzes a strategy integrating biochar production, phosphorus wastewater treatment, dephosphorization waste recovery, and heavy metal removal. “BC-Ca-P” was derived from Ca-modified biochar after phosphorus wastewater treatment. The adsorption of Pb(II) by BC-Ca-P followed the Langmuir isotherm and pseudo–second–order kinetic models. The maximum adsorption capability of 361.20 mg·g−1 at pH 5.0 for 2 h was markedly greater than that of external phosphorous-modified biochar. The adsorption mechanisms were dominated by chemical precipitation and complexation. Furthermore, density functional theory calculations indicated that oxygen-containing functional groups (P-O and C-O) contributed the most to the efficient adsorption of Pb(II) onto BC-Ca-P. To explore its practical feasibility, the adsorption performance of BC-Ca-P recovered from an actual environment was evaluated. The continuous-flow adsorption behavior was investigated and well-fitted utilizing the Thomas and Yoon–Nelson models. There was a negligible P leakage risk of BC-Ca-P during heavy metal treatment. This study describes a novel and sustainable method to utilize dephosphorization waste for heavy metal removal.Graphical

Oily Wastewater Treatment by Using Fe3O4/Bentonite in Fixed-Bed Adsorption Column

Oily wastewater is a major environmental issue resulting from different industrial and manufacturing activities. Contaminated water with oil represents a significant environmental hazard that can harm numerous life forms. Several methodologies have been tested for the removal of oily wastewater from aqueous solutions, and adsorption in a flow-through reactor is an effective mechanism to reduce these effluents. This study focuses on evaluating the ability of Fe3O4/Bent material to adsorb gasoline emulsion from a solution using a fixed-bed column, and it involves analyzing the resulting breakthrough curves. The FT-IR, SEM, EDX, and XRD techniques were used to characterize Fe3O4/Bent. Various ranges of variables were examined, including bed height (2–4 cm), flow rate (3–3.8 mL/min), and initial concentration (200–1000 mg/L), to determine their impacts on the mass transfer zone (MTZ) length and the adsorption capacity (qe). It was shown that a higher bed height and a lower flow rate contributed to a longer time of breakthrough and exhaustion. At the same time, it was noted that under high initial gasoline concentrations, the fixed-bed system rapidly reached breakthrough and exhaustion. Models like the Yoon–Nelson and Thomas kinetic column models were employed to predict the breakthrough curves. Thomas and Yoon–Nelson’s breakthrough models provided a good fit for the breakthrough curves with a correlation coefficient of R2 > 0.95. Furthermore, with a fixed-bed system, the Thomas and Yoon–Nelson models best describe the breakthrough curves for gasoline removal.

Cadmium sequestration with MgCuAl-layered double hydroxide@montmorillonite nanocomposite in batch and circulated fluidized bed column experiments

In this study, montmorillonite cationic clay coated with MgCuAl-Layered double hydroxide nanoparticles was investigated for its capacity to adsorb cadmium ion (Cd2+) from aqueous solutions. Montmorillonite, MgCuAl−LDH, and a novel MgCuAl-Layered double hydroxide@montmorillonite nanocomposite (MCA−LDH@MMt) were characterized using various mechanisms including BET surface areas, XRD, TEM, FTIR, and SEM/EDS analysis. The adsorption behaviour of MCA−LDH@MMt towards Cd2+ ion was studied using batch and continuous flow systems. pH, contact time, initial Cd2+concentration, MCA−LDH@MMt dose and particle size, agitation speed, and temperature were examined in the batch system. The higher removal efficiency of Cd2+was reported at pH 5 at 70 mg/l initial concentration and 0.2 g/100 ml best adsorbent dose with 150 rpm. The adsorption of Cd2+ on MCA−LDH@MMt followed Langmuir model and yielded a maximum adsorption capacity of 129.82 mg/g. While the pseudo-second-order model better simulates the cadmium kinetics data, and adsorption rate parameters values showing that the adsorption process was chemisorption and the rate-determining step of controlling cadmium adsorption onto MCA−LDH@MMt not intra-particle diffusion. A three-phase, commonly known as gas-liquid-solid circulated fluidized bed column was used to continuously eliminate Cd2+. Four influencing parameters were studied: liquid and air flow rate, bed height, and initial Cd2+concentration. The adsorption efficiency of Cd2+in a continuous system increased when the liquid flow rate decreased and the bed height increased. The time required for MCA−LDH@MMt to reach saturation increases as the bed height and the air flow rate increase. Column data were described using Bohart-Adams, Thomas, and Yoon and Nelson models of adsorption for given experimental conditions. The Bohart-Adams could represent the initial regime of the breakthrough curves, while the Thomas model was better at describing the whole curve of metal ion adsorption for a given experimental condition.

Modeling of hexavalent chromium removal onto natural zeolite from air stream in a fixed bed column

The increasing use of hexavalent chromium (Cr(VI)) has exposed large populations to this environmental and occupational carcinogenic agent. Therefore, researchers have been interested in removing this substance through adsorbents. This study aimed to investigate the efficiency of natural zeolite in the direct adsorption of Cr(VI) from airflow and its adsorption modeling. In this study, a nebulizer device produced the Cr(VI) mist. The efficiency of natural zeolite in Cr(VI) adsorption from airflow, modeling of fixed column adsorption, and the effective parameters on adsorption efficiency including the initial concentration of chromium, airflow rate, and adsorption bed depth were studied. To facilitate the prediction of the performance of natural zeolite’s adsorption column, Yoon–Nelson, Thomas, BDST, and Buhart–Adams models were used. The results showed that the adsorption capacity diminished with increased airflow rate and initial concentration, while it increased with elevated height of the adsorption bed. Yoon–Nelson, Thomas, and BDST models corresponded to experimental data with a correlation coefficient of 0.9933, but the information of the Buhart–Adams model had a lower correlation coefficient (around 0.6677). In conclusion, natural zeolite can be used as an efficient low-cost adsorbent for directly Cr(VI) removing from the airflow in a fixed bed column.

Fixed-bed adsorption of methylene blue using granular NaX zeolite/attapulgite composite: efficiency, mechanism and reusability of saturated G-NaX/A

A novel granular NaX zeolite/attapulgite (G-NaX/A) composite was developed to address the challenges of high pressure drop in fixed beds with powder synthetic zeolite and low adsorption capacity of natural zeolite. The synthesized G-NaX/A retains the micropores of NaX and the mesoporous of attapulgite. The BET specific surface area reached 481.17 m2/g, and the total pore volume was 0.3549 cm3/g. The G-NaX/A maximum methylene blue (MB) adsorption capacity was 1.56 times that of commercial granular activated carbon (7.41 mg/g). The breakthrough time and adsorption capacity improved with lower influent flow rate and MB concentration and higher pH. Under optimal conditions (flow rate: 150 mL/min, MB concentration: 25 mg/L, pH = 8), it achieved a maximum adsorption capacity of 11.51 mg/g and a breakthrough time of 2.54 h. The adsorption behavior of G-NaX/A was well-fitted by the Yoon–Nelson and Thomas models at different operating conditions. The mechanism studies revealed that MB (cation: C16H18SN3+) removal by G-NaX/A occurred through electrostatic attraction, ion exchange with Na+/Mg2+, surface coordination with ≡Al/SiOH, and surface physical adsorption. The regeneration studies confirmed the reusability potential of G-NaX/A by calcining at 500 °C for 2 h, and significantly improved adsorption capacity reaching about 14.39 mg/g, 16.31 mg/g and 14.07 mg/g across the three adsorption-regeneration cycles respectively. The findings support G-NaX/A technical feasibility, high adsorption capacity and potential for further scaling in fixed bed adsorption studies.

Th(IV) adsorption by heulandite–high-temperature activated sodium zirconium phosphate from aqueous solution

Herein, heulandite–high-temperature activated sodium zirconium phosphate (HEU–HTA-Na-ZrP) composites were first synthesised for adsorbing tetravalent thorium (Th(IV)) from aqueous solution. Furthermore, the HEU–HTA-Na-ZrP pellets (HEU–HTA-Na-ZrP-P) were fabricated for dynamic adsorption. Compared to Na-ZrP, the BET surface area of HEU–HTA-Na-ZrP increased of ∼ 189 m2⋅g−1. In batch adsorption, Th(IV) adsorption increased with increasing pH, C0 values (initial concentrations) and temperature. The equilibrium Th(IV) adsorption capacities were 314.17 ± 11.27 mg⋅g−1 and 358.89 ± 3.47 mg⋅g−1 for Na-ZrP and HEU–HTA-Na-ZrP, respectively. Thermodynamics, isotherms and kinetics suggested an endothermic, spontaneous, homogeneous and chemisorption process. Characterization verified the adsorption capacities of Th(IV), and the main possible Th(IV) adsorption mechanisms were associated with ion exchange and –OH, Zr–O coordination. Notably, the reusability study indicated that the samples treated with 0.1 mol⋅L−1 H3PO4 solution exhibited excellent reusability. Dynamic adsorption results indicated the structural stability of the composite pellets. 50% Th(IV) breakthrough time (τ (min)) increased with increasing mass and then decreased, and τ (min) decreased with increasing pH. Both Thomas and Yoon–Nelson models could better describe the Th(IV) dynamic adsorption behaviour. Moreover, HEU–HTA-Na-ZrP-P could separate Th(IV) from simulated and real nuclear wastewater. This work demonstrates that HEU–HTA-Na-ZrP can be applied as an efficient adsorbent for the removal of Th(IV) from Th-containing solutions.

Behavioral aspects of auditor's professional judgment and professional skepticism

The paper examines the behavioral aspects of auditing in the context of auditor’s independence, auditor’s professional judgment, and professional skepticism. Over the past 50 years, in the researches of foreign scientists, the issues of accounting and auditing have been considered through the theory of behavioral accounting. On the other hand, in the studies of Ukrainian scientists, behavioral accounting in accounting and auditing was almost not considered. The main meaning of the theory of behavioral accounting is not to consider accounting and auditing exclusively in numbers, but to consider that accountants and auditors are people with a specific profession who behave according to their feelings and thoughts. It is customary to consider the concept of behavioral accounting according to the following topics: the influence of accounting information on behavior, management control, audit, ethics. Behavioral aspects of the auditor's independence, which are influenced by an auditor's personal prejudices and the auditor-client relationship, are studied. Auditor’s independence is considered in two dimensions - organizational independence and operational independence. E.g., independent auditors may face the problem of conflicting interests of the public and clients. Behavioral aspects of negotiations between the auditor and the client are also considered. The negotiation tactics used by the participants matter. It can be a yielding tactic, or a tactic of disputes. In particular, in the study of accommodating tactics, it was found that both auditors and clients reciprocated the accommodating negotiation tactics. There are many models of professional skepticism that have been summarized. Nelson and Hurtt's models are considered, the two fundamental components of which are professional skeptical judgment and professional skeptical action. Auditors should exercise professional skepticism, making judgments based on audit evidence without being influenced by clients.

Adsorption studies on synthetic lentil-like mordenite for column and batch removal of cadmium and lead ions: investigating isotherms and kinetics

ABSTRACT The mordenite zeolite adsorbent, with a lentil-like structure, was synthesised using a one-step green hydrothermal method. Its textural, structural, and morphological properties were characterised through X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, and the Brunauer-Emmet-Teller (BET) method. The prepared adsorbent was employed in both continuous and batch adsorption processes to remove toxic Cd(II) and Pb(II) metal ions from aqueous solutions. Operational parameters such as flow rate, initial concentration, and bed height were varied to understand breakthrough time, mass transfer zone, adsorption capacity, and exhaustion time during continuous adsorption, which were investigated and optimised. Additionally, the study explored the influence of solid/liquid ratio, pH, assay time, and initial concentration on batch adsorption. The maximum adsorption capacities of the lentil-like mordenite zeolite in fixed-bed breakthrough experiments were determined to be 78.22 mg/g for Cd (II) ions and 80.82 mg/g for Pb (II) ions. In batch experiments, the capacities were 133.64 mg/g for Cd (II) ions and 239.57 mg/g for Pb (II) ions. Dynamic continuous adsorption isotherms exhibited an excellent fit with the Thomas and Yoon – Nelson models, while batch adsorption isotherms conformed well to the Langmuir model. This study presents a new approach for synthesising high surface area, engineered morphology, reusable, and stable zeolite for effectively adsorbing hard metal ions from wastewaters, contributing to environmental remediation.

Performance evaluation of calcined eggshell waste (Sorbent) for biogas upgrading: Adsorption isotherms, adsorption kinetics, and fixed bed studies

The use of non-renewable energy resources such as fossil fuels accelerates climate change and environmental degradation necessitating a shift to renewable energy sources. Biogas is a renewable energy resource with great potential. However, its application is limited by the presence of contaminants such as carbon dioxide, which reduces its energy value, and density. Upgrading biogas using locally available materials solves waste management and energy sustainability challenges. In the present study, calcined eggshell waste was employed as an adsorbent for carbon dioxide. The effect of calcination temperature, adsorbent mass and adsorbent particle size was evaluated. The experimental data was fitted to adsorption isotherms, adsorption kinetic models, and breakthrough curves. Eggshells with a particle size of 280 μm, calcined at 850 °C, and mass of 75 g showed the best performance in removing carbon dioxide from biogas. It was noted that data from the experiment fitted Langmuir isotherm with RL 0.00216 while its R2 was 0.97 and Freundlich n = 0.6 while R2 = 0.97. Regarding adsorption kinetics, the intra-particle diffusion model shows good conformity with kid of 34, C of 98, and R2 of 0.977. Breakthrough analysis proved that Yoon Nelson's Model fitted well with the experimental data with an R2 of 0.989. Thus, calcined eggshell waste is a good sorbent for biogas upgrading that can solve the twin challenges of waste disposal and management and energy sustainability.

Spectral properties and non-Hermitian skin effect in the Hatano–Nelson model

At present, non-Hermitian topological systems continue to be actively studed. In a rigorous approach, we study one of the key non-Hermitian systems — the Hatano–Nelson model $H$. We find the Green function for this Hamiltonian. Using the Green function, we analytically obtain the eigenvalues and eigenfunctions of $H$ for finite and semi-infinite chains, as well as for an infinite chain with a local potential. We discuss the non-Hermitian skin effect for the models mentioned above. We also describe the boundary between localized and resonant eigenfunctions (for the zero spectral parameter, this is the boundary between non-Hermitian topological phases).

Fixed Bed Column Adsorption System for the Removal of 2,4-Dichlorophenoxyacetic Acid Herbicide from an Aqueous Solution

The intensive use of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide has resulted in the presence of its residues in the environment, which leads to contamination of surface and groundwater. In this study, a fixed-bed column experiment was conducted for the removal of 2,4-D from an aqueous solution using termite mound soil (TMS). Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), atomic absorption spectrometry (AAS), and Brunauer–Emmett–Teller (BET) techniques were used to characterize the adsorbent. The effect of significant variables, such as the initial 2,4-D concentration (50 mg/L and 75 mg/L), flow rate (2.5 ml/min and 5 ml/min), solution pH (2, 4, and 6), and bed height (3, 6, and 9 cm), on the breakthrough characteristics of the adsorption system was assessed. In addition, the Thomas and Yoon–Nelson models were applied to predict the breakthrough curves and to determine the characteristic parameters of the column that are useful for process design. The findings showed that at a lower pH (2), a lower flow rate (2.5 ml/min), a lower 2,4-D concentration (50 mg/L), a higher bed depth (9 cm), and 840 min breakthrough time, a higher removal percentage (80.2%) of 2,4-D was achieved. The experimental data were in good agreement with the Thomas and Yoon–Nelson models. For the Yoon–Nelson model, the rate constant increased with an increase in the flow rate, initial ion concentration, and bed height. The time required for a 50% breakthrough decreased with an increase in the flow rate, bed height, and initial ion concentration. For the Thomas model, the rate constant increased with an increase in the flow rate but decreased with an increase in bed height and initial concentration. Overall, the study showed that termite mound soil in a fixed-bed column adsorption system presents an excellent potential for removing 2,4-D from aqueous solutions.

The Scale of Motivationess: an Empirical Description of the Phenomenon and a Presentation of the Method

The aim of the article consists in establishing empirical descriptors of the state of motivation. Methods. The study was implemented according to the Nelson model, which provides for the possibility of determining the essence of the problem under the existing conditions. The empirical research used such methods as the motivation structure questionnaire, the existential feasibility scale of Lange and Orgler, the Schwartz motivational values questionnaire, the Luthans psychological capital method, the Riff psychological well-being questionnaire, the personality life tasks questionnaire (Laboratory of Social Psychology of the personality of Prof. Tytarenko), the questionnaire of Stepa’s reserve motivation, Stepa’s psychological resourcefulness questionnaire, meaningfulness of life method (an adaptation version of the Krumbo and Maholik questionnaire), Muddy’s hardiness questionnaire. The following methods of mathematical and statistical analysis were applied: multivariate, cluster, correlational, comparative, and classification analysis. Research results. The following indicators of motivationess were determined: confidence in one’s capabilities, realistic goal formulation, a clearly defined sequence of actions, effective self-organization of time, understanding of the ratio of one’s strengths and difficulties, completing a task by applying one’s efforts, interest in the process of completing the task, desire to complete the task, inspiration from one’s own experience of success, the ability to draw analytical conclusions from one’s own experience of failures, resistance to stress during task performance, proactiveness in setting the task, the desire to receive and provide informative feedback during the execution and completion of the task, readiness to learn new knowledge and skills to perform the task, sense vocation for staging and completing the task. Cronbach alpha for statements of the Motivationess scale is within 0.91–0.92. The value of intercorrelations of motivationess indicators is 0.30–0.78 (p < .001). The classification analysis showed that low, medium, and high levels of motivationess were correctly determined by 90%, 100%, and 100%, respectively. The structure of motivationess is two-factor, cumulative multi-factor analysis explained 59% of the variance of the data in the group. A higher level of motivationess is characterized by its procedural, dynamic indicators. The k-means method showed the correctness of distinguishing two types of motivationess - low and high; the type of motivationess is determined by its dynamic indicators. Conclusions. Motivationess is characterized by us as a dynamic motivational state of existential discourse, which is actualized about a certain life task, is manifested in the ability of the individual to correlate his resources with the challenges of life conditions in a dialogic interaction, and is experienced by him as inspiration. The motivation scale received the necessary indicators of its reliability. The text of the Motivationess scale is included in the appendix to the article.

Adsorption equilibrium, kinetics and dynamic process of polyphenols from orange peel extract on mixed‐mode adsorption resin HD‐1

AbstractBACKGROUNDThe extraction and separation of natural polyphenols are attractive. Many researchers used high‐speed counter‐current chromatography to separate and purify polyphenols. However, it requires a long operating time, a large amount of organic solvent consumption, and high operating costs. In this work, the adsorption behaviors of polyphenols from orange peel extract on mixed‐mode resins were studied. The adsorption capacities and selectivities of different resins to the main polyphenols in the extract including gallic acid, p‐coumaric acid and ferulic acid were compared. The adsorption mechanism was analyzed by adsorption equilibrium and kinetics studies as well as molecular docking. The fixed‐bed adsorption was studied experimentally and theoretically.RESULTSHD‐1 resin has excellent adsorption selectivities among the resins. The yield of polyphenols from orange peel by integrated extraction‐adsorption increased by 82.94% compared with that of extraction without adsorption. The adsorption isotherms agreed with the Freundlich model. Dubinin–Radushkevich model results indicated that the adsorption of gallic acid mainly depends on nonelectrostatic interaction. The adsorption of the other two polyphenols involves electrostatic and nonelectrostatic interaction. The adsorption kinetics curves accorded with the pseudo‐second‐order model, and the adsorption rate of gallic acid was the highest among the polyphenols. Adsorption of polyphenols involves both physical and chemical adsorption. The breakthrough curves could be closely simulated by Yoon–Nelson and Thoms models. Significant differences existed in times for 50% breakthrough.CONCLUSIONMixed‐mode chromatography with HD‐1 resin as stationary phase is applicable to the separation of polyphenols. © 2024 Society of Chemical Industry (SCI).

Bone Char Adsorption of COD and Colour from Tannery Wastewater: Breakthrough Curve Analysis and Fixed Bed Dynamic Modelling

This study delves into the simultaneous adsorption of chemical oxygen demand (COD) and colour from tannery wastewater using bone char through a fixed bed column. The bone char, which was derived from cattle skulls, was characterised using the Fourier transform infrared spectroscopy, Braeuer–Emmett–Teller surface area analysis, and the scanning electron microscope/energy-dispersive X-ray spectroscopy. The effects of different process conditions, specifically, packed bed height (5, 10, and 15 cm) and flow rate (2, 5, and 8 mL/min), on the adsorption efficiency of the fixed bed column were assessed through breakthrough curve analysis. The results revealed that the efficiency of the column bed enhanced with increasing bed height and declined with increasing wastewater flow rate. The optimal operating conditions for COD and colour removal onto the bone char occurred at 15 cm bed height and 2 mL/min flow rate. The adsorption capacities at these conditions were 227.4 mg/g and 53.03 Pt-Co/g for COD and colour, respectively. The kinetics associated with the fixed bed adsorption of COD and colour onto bone char were elucidated through the fitting of the Thomas, Adams–Bohart, and Yoon–Nelson models to the experimental data. Among the three models, the Yoon–Nelson model gave the best prediction of the experimental data. Maximum adsorption efficiencies of 80.65% and 84% were attained for COD and colour removal, respectively, proving that bone char is a promising and ecologically friendly alternative adsorbent for the treatment of tannery wastewater.

Dynamic Adsorption of a Cationic Dye onto Wool Fibers as Column-Filling Media: Response Surface Optimization and Fixed-Bed Adsorption Modeling.

This study reports a simple and low-cost method for water purification using recyclable natural fibers (coarse wool fibers) as column-filling media for adsorption in the dynamic mode. As an instance of a dissolved organic pollutant, a cationic dye (basic blue 9, BB9) was assayed. According to the Langmuir isotherm (recorded at 300 K), the calculated maximum adsorption capacity of the fibrous material was found to be 24.86 mg/g for the retention of BB9. Response surface methodology (RSM) was employed for the design of experiments and the model-based optimization of the adsorption process performed in the dynamic regime (fixed-bed column). The optimal conditions provided by RSM indicated an adsorbent column height of H = 13.5 cm and a feed flow rate of Fv = 3 mL/min; these operating parameters ensured a color removal efficiency of 92.56% after 240 min of contact time. The recorded breakthrough curve under the optimal conditions was further interpolated using five quantitative mathematical models (Adams-Bohart, Thomas, Yoon-Nelson, Yan, and Clark) to assess the dynamic behaviors in the fixed-bed column. The best goodness-of-fit was achieved for the Thomas and Yoon-Nelson models. Thus, the coarse wool fibers used in a fixed bed demonstrated a relevant efficiency in the removal of cationic organic pollutants from contaminated water.

Continuous Adsorption of Acid Wood Dyes onto an Activated Carbon Prepared from Pine Sawdust

In this paper, an activated carbon obtained from Pinus radiata sawdust is applied to remove blue, red, and black wood dyes from aqueous solutions in a fixed-bed column. The flow rate (7.7–30.8 mL min−1), initial dye concentration (25–500 mg L−1), and bed height (2–4 cm) highly influence the breakthrough-curves’ features. The results indicate that the adsorption capacity increased by decreasing the flow rate and increasing the initial dye concentration, except for the black dye, and increasing bed height, except for the red dye. In addition, the breakthrough time changed by modifying the studied variables. The curves became steeper as the flow rate increased and as the bed height decreased. Also, by increasing the inlet dye concentration, the breakthrough time decreased significantly, and sharper breakthrough curves were obtained. The activated carbon with a surface area of 2826 m2 g−1 led to high values of the adsorption capacity between 150 and 1300 mg g−1. The Yoon–Nelson and Thomas models were the ones that best described the adsorption data. The activated carbon saturated with black dye could be used in three successive cycles after regeneration with H2O2.

Non-Fock ground states in the translation-invariant Nelson model revisited non-perturbatively

The Nelson model, describing a quantum mechanical particle linearly coupled to a bosonic field, exhibits the infrared problem in the sense that no ground state exists at arbitrary total momentum. However, passing to a non-Fock representation, one can prove the existence of so-called dressed one-particle states. In this article, we give a simple non-perturbative proof for the existence of such one-particle states at arbitrary coupling strength and for almost all total momenta in a physically motivated momentum region. Our results hold both for the non- and the semi-relativistic Nelson model.