Bed Depth Research Articles

Chromium Removal Using a Basalt Rock Adsorbent in a Packed Bed Column for Efficient Environmental Protection.

The discharge of chromium(VI) into the environment is becoming a significant global concern. Despite the existence of numerous techniques for chromium(VI) removal, substantial challenges persist in effectively mitigating this issue. Therefore, this study investigates the feasibility of using low-cost basalt rock as an adsorbent for chromium(VI) removal. The adsorbent was prepared through size reduction and activation and subsequently characterized by using X-ray diffraction and Fourier transform infrared procedures. The characterization revealed that the adsorbent predominantly consists of SiO2 and Al2O3 and contains functional groups that facilitate the adsorption mechanism. The adsorption potential of the basalt rock was initially evaluated in a batch adsorption procedure, which yielded an adsorption capacity of 14 mg/g. The batch adsorption results were best fitted by the Langmuir adsorption isotherm, with an R 2 > 0.9, indicating monolayer adsorption. Subsequently, continuous adsorption was conducted using a fixed-bed column to assess the influence of operational parameters and evaluate the desorption behavior of the adsorbent by using fixed-bed models. Breakthrough curves were utilized to assess the fixed bed performance, revealing that increased column depth and decreased flow rate extend the saturation time of the bed. The experimental data from the fixed-bed column fit the bed depth service time and Yoon-Nelson models well. The adsorbent demonstrated successful reuse across four consecutive cycles, with the regenerated basalt rock adsorbent exhibiting a chromium(VI) adsorption capacity of 2 mg/g in the fourth cycle, retaining approximately 23% of its initial adsorption capacity. The findings of this research indicate that the basalt rock-based adsorbent possesses significant potential for removing chromium(VI) from aqueous solutions in a continuous adsorption bed column.

Continuous packed bed column removal of Cr6+, Cd2+, and Pb2+ ions from synthetic wastewater using polymeric ultra‐permeable and biodegradable ferromagnetic nanocomposite membrane

AbstractWater purification techniques, including membrane technologies, ion exchange and adsorption, chemical/biochemical reduction, and electrochemical processes, have been developed to remove/recover metal ions species from polluted wastewater. This work assessed the efficiency of polymeric, biodegradable, ultra‐permeable and magnetic nanocomposite membrane (CNCs/N6@Fe3O4‐CT) in a continuous packed bed column for the removal of Cd(II), Cr(VI), and Pb(II) metal ions from synthetic wastewaters. The eco‐compatibility of CNCs/N6@Fe3O4‐CT was increased using chitosan biopolymer. Fe3O4 nanoparticles increased the surface area and improved the separation process. CNCs and N6 polymeric materials enhanced their strength, porosity, and additional binding sites. The CNCs/N6@Fe3O4‐CT nanocomposite membrane was employed as packing material in a fixed‐bed lab‐scale column (height 30 cm, diameter 1.5 cm) to constantly remove Cd(II), Cr(VI), and Pb(II) metal ions from synthetic wastewaters and actual hexavalent chromium tannery effluent. The studies were carried out with different initial metal ion concentrations (10, 20, and 30 mg/L), input flow rates (2, 4, and 6 mL/min), and solution pH values (2.0, 5.0, and 8.0). The obtained experimental data from the breakthrough curves was fitted to the traditional dynamic Thomas model, Yoon‐Nelson, and Bed Depth Service Time (BDST) model.

New Wine in Old Bottles: The Sustainable Application of Slow Sand Filters for the Removal of Emerging Contaminants, a Critical Literature Review

The current treatment of wastewater has unintended negative environmental impacts. Conventional methods frequently involve the use of harmful chemicals, generate disinfectant by-products, consume significant amounts of energy, and produce wastes requiring additional efforts for safe disposal. Water stress exacerbated by contaminants of emerging concern (CECs) and climate change, is further straining aging treatment systems. A slow sand filter (SSF), with ligno-cellulosic layers, offers a novel, promising, and economic alternative for wastewater reclamation. This review examines the key SSF characteristics, obtained from recent studies, and explores the use of sustainable materials such as ligno-cellulose, as a treatment companion. The optimal SSF design includes a bed depth of >0.6 m, particle effective size (D10) between 0.15 mm and 0.40 mm, and a uniformity coefficient (CU grain size ratio) of ≤2.0. It is established that SSF’s characteristic biolayer of microorganisms enhances contaminant removal via biodegradation. While biofilm-based removal of micropollutants is a proven mechanism, further research is needed to address CEC challenges. For example, the inclusion of sawdust in SSF filter layers can reduce energy consumption compared to conventional methods and can be recycled through thermal conversion, aligning with circular economy principles. This approach has the potential to improve wastewater treatment in emerging economies, contributing to the achievement of the UN Sustainability Goals.

Removal of carbendazim by sorption onto a continuous fixed bed hybrid filter of calcined clay and waste derived biochar

This study focused on enhanced Carbendazim (CBZ) removal by using dual filter media of calcined clay (CC) and biochar (WB-BC) in a continuous fixed-bed column. The experiments were carried out using synthetic and real water. In the continuous system with an initial CBZ concentration of 0.2 mmol L−1, a flow rate of 4 mL min−1, a bed depth of biochar 1 cm and a pH of 6.8, the optimal values for the mass transfer zone (0.64 cm) and adsorption capacity (0.38mmolg−1) were observed. Furthermore it was observed that the dual filter media of WB-BC and CC effectively adsorbs CBZ from real water matrix, with an average adsorption capacity of 0.33mmolg−1. Significant reduction in the concentrations of chlorides, sulfates, nitrates, Ca2+, and Mg2+ were also observed in real water samples along with CBZ removal. Analysis using mass-transfer models showed that BDST model effectively described the breakthrough curve data. Density Functional Theory (DFT) calculations revealed that WB-BC exhibits a stronger interaction and higher adsorption capacity for CBZ compared to CC as evidenced by a shorter vertical distance (2.711 Å) and higher adsorption energy value (−42.95kJmol−1) in case of WB-BC-CBZ complex. Additionally, the larger band gap (ΔE) value (2.881 eV) for WB-BC-CBZ complex indicates superior structural stability and chemical hardness.

Penetration of jet piles on submerged granular beds

The study examines the dynamics of jet pile penetration into submerged granular beds through laboratory experiments with the jet pile positioned atop the granular bed. It examines how varying water jet velocities affect penetration depth across different pile diameters and granular media sizes. Results show that high-velocity water jets locally fluidize particles around the pile, reducing inter-particle resistance within the bed, which, in turn, cannot support the self-weight of the pile, allowing smoother penetration. The onset of fluidization and pile penetration, marked by a critical jet velocity, increases with bed depth. Jet pile penetration is governed by a balance of forces: water jet force (FJet), pile self-weight (Fsw), buoyancy (FB), and resistance from the granular bed (FR). A power law relationship is proposed to predict penetration depth across different grain and pile sizes, providing a predictive model for jet pile penetration depth. This scaling law, validated with another experimental study, demonstrates consistent accuracy.

Efficient in situ synthetic routes of the polymeric composite containing clinoptilolite using ultrasonic assistance for sorption of some lanthanides

The ultrasound assistance synthesis strategy of the polymeric composite is based on free radical polymerization of polyallylamine hydrochloride (PAH) cationic polyelectrolyte, with vinyl sulfonic acid (VSA) anionic monomer with microporous crystalline alumino silicate clinoptilolite clay. The P(AH-co-VSA)/clinoptilolite polymeric composite was fully characterized by fourier transform infrared spectroscopy, energy dispersive X-ray, thermogravimetric analysis, and scanning electron microscope. FTIR demonstrated the presence of PAH and VSA, confirming the composition of the prepared composite. It was also used to map the energy-dispersive X-ray to affirm the interdependence of the clinoptilolite into the polymeric matrix. Consequently, the physicochemical characteristics of this copolymer may be adjusted using VSA and PAH suitable combinations. Batch experiments were applied and maximal sorption capacities for studied ions Nd3+, Ce3+, Y3+, Gd3+, and Eu3+ were 36.6, 50.2, 55.9, 57.2, and 57.7 mg/g, respectively. Sorption kinetics and equilibrium isotherm were conducted. Experimental isotherms of studied ions were successfully fit to pseudo-second-order model, langmuir isotherm model. The Dubinin–Radushkevich (D–R) isotherm was found to be applicable and suggesting that, the sorption occurs via a ion exchange reaction. The breakthrough data were measured in a fixed bed column, and variable process factors were examined, including bed depth, flow velocity, and initial metal ion concentration. The experimental work was then focused, for continuous investigations, on Ce3+, Eu3+, and Y3+ to represent light, intermediate, and heavy lanthanides respectively. The overall bed capacity and total metal ion adsorption increased when the flow rate increased. They reduced with rising initial metal ion concentration and bed depth, and reached 22.8, 31.4, and 28.5 mg/g for Ce3+, Eu3+, and Y3+ metal ions, respectively.

Parthenium hysterophorus invasive weed valorization into biochar for removal of pharmaceuticals and personal care products: Competitive adsorption analysis via batch and fixed–bed column systems

The proliferation of invasive weeds and emergence of new contaminants have become significant global concern, threatening human–health and environment. This investigation assesses performance of Parthenium hysterophorus weed–derived biochar (HPC and KPC) for removing acetaminophen (ACT) and metronidazole (MET) in single (ACT/MET) and multi–component (ACT + MET) systems in batch and column modes. Synthesized HPC and KPC were characterized through SEM, EDX, XRD, porosimetry, TGA and FTIR analyses. HPC displayed micropores, featuring surface area of 166.62 m2/g, while KPC exhibited mesopores with 146.16 m2/g surface area. The investigation in batch study includes exploring operating conditions like contact time (0–180 min), concentration (0.5–20 mg/L), biochar dose (0.25–4 g/L) and pH (2–12). At optimal conditions (1 h, pH 6.5 and 1 g/L dose), HPC achieved maximum sorption capacity 48.72 mg/g for MET and 32.10 mg/g for ACT, and KPC exhibited 18.41 mg/g for MET and 16.54 mg/g for ACT in batch mode. According to findings, pseudo–second–order and Langmuir models provided accurate–fit for batch experimental data. Furthermore, study also investigated influence of column operating conditions such as bed depth (3–9 cm), flow rate (0.25–1.00 L/h) and concentration (5–20 mg/L). In column, HPC outperformed KPC in removing ACT and MET, with breakthrough data fitting Thomas model. Both systems exhibit synergistic effect in simultaneously removing ACT and MET from multi–pollutant mixture. In summary, converting invasive weeds into biochar and employing it to remove emerging contaminants provides sustainable approach to protecting aquatic environment and invasive weeds management.

Two-way coupling between ice flow and channelized subglacial drainage enhances modeled marine-ice-sheet retreat

Abstract. Ice-sheet models used to predict sea-level rise often neglect subglacial hydrology. However, theory and observations suggest that ice flow and subglacial water flow are bidirectionally coupled: ice geometry affects hydraulic potential, hydraulic potential modulates basal shear stress via the basal water pressure, and ice flow advects the subglacial drainage system. This coupling could impact rates of ice mass change but remains poorly understood. We develop a coupled ice–subglacial-hydrology model to investigate the effects of coupling on the long-term evolution of marine-terminating ice sheets. We combine a one-dimensional channelized subglacial hydrology model with a depth-integrated marine-ice-sheet model, incorporating each component of the coupling listed above, yielding a set of differential equations that we solve using a finite-difference, implicit time-stepping approach. We conduct a series of experiments with this model, using either bidirectional or unidirectional coupling. These experiments generate profiles of channel cross-sectional area, channel flow rate, channel effective pressure, ice thickness, and ice velocity. We discuss how the profiles shape one another, resulting in the effective pressure reaching a local maximum in a region near the grounding line. We also describe the impact of bidirectional coupling on the transient retreat of ice sheets through a comparison of our coupled model with ice-flow models that have imposed static basal conditions. We find that including coupled subglacial hydrology leads to grounding-line retreat that is virtually absent when static basal conditions are assumed. This work highlights the role time-evolving subglacial drainage may have in ice-sheet change and informs efforts to include it in ice-sheet models. This work also supplies a physical basis for a commonly used parameterization which assumes that the subglacial water pressure is set by the bed's depth beneath the sea surface.

Defluoridation of Groundwater Using Low-cost Adsorbents

Excessive fluoride in groundwater poses significant health risks to millions of people worldwide, necessitating effective and accessible defluoridation methods. This study investigates the use of column filtration for removing fluoride from groundwater. The study employs a systematic approach to evaluate the performance of different adsorbent materials in a fixed-bed column setup. Various materials were tested as adsorbents in column, including Brick powder, Neem leaf powder, Lime, Sawdust, and Vetiver. The research examines the effects of key operational parameters such as bed depth, flow rate, and initial fluoride concentration on the overall removal efficiency. Experiments were conducted using groundwater to assess the method's effectiveness. Results indicated that column filtration can effectively reduce fluoride concentrations to below the World Health Organization's recommended limit of 1.5 mg/L. This report contributes to the development of efficient, cost-effective, and sustainable solutions for groundwater defluoridation. All adsorbents used were inexpensive materials, available easily in nature and locally at village or rural level. Some of the adsorbents were very effective in removal of fluoride ion and can be used as defluoridating agents but they impart color and turbidity to the groundwater. Among all the adsorbents used, Vetiver demonstrated higher removal efficiency of 78% followed up by limestone 77% removal but hindered by its precipitation. Sawdust and brick powder were also efficient up to a certain extent of 72% and 69% respectively in adsorbing fluoride ions. Neem leaves powder was found to be least effective in adsorbing showing about 50% removal efficiency.

An experimental investigation into the characteristics of ammonia dissociation in a Bubbling Fluidised Bed

Ammonia (NH3) dissociation is of an initial and very important step during its combustion process. This study therefore systematically investigates the effect of reaction temperature (650–950 °C), fluidisation number (0.83–2.50) and static bed depth (0–25 mm) on NH3 dissociation in a laboratory-scale Bubbling Fluidised Bed (BFB). By analysing the concentrations of H2 and N2 in the effluent using gas chromatography, results show that the conversion ratio of NH3 in BFB was merely 0.26%–0.29% at 650 °C but increased significantly to 18.1%–25.3% at 950 °C. This highlights the importance of temperature in promoting NH3 dissociation. However, as fluidisation number increased from 1.0 to 2.5, attributing to a decrease in gas – solid contact time, the conversion ratio of NH3 decreased correspondingly from the highest 20.7%–5.7%. Moreover, as static bed depth increased from 15 mm to 25 mm, the conversion ratio of NH3 increased slightly from 21.5% to 26.8%, both of which were found to be higher than that without bed particles. Clearly, NH3 dissociation is enhanced by the bed material depth but is also dependent on the gas – solid contact time. In addition, by measuring the temperature distribution in the BFB reactor, a temperature drop of ca. 20 °C near the distributor was confirmed, showing a strong effect of endothermicity during NH3 dissociation. These would provide an improved comprehension on the mechanisms of NH3 dissociation and offer theoretical guidance for optimising the combustion processes in BFB burning NH3.

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.

Bio-Adsorbent for Elimination of Reactive Dye from Aqueous Solution: Kinetic and Statistical Modelling Study

Introduction/Background: The use of various dyes to colour products is a general practice in various industries. The occurrence of these dyes in water, even at small concentrations, is highly noticeable and aesthetically objectionable. In the present study, the applicability of inexpensive and eco-friendly bio-adsorbent has been tested as an alternative substitution of the commercially available activated carbon for the removal of reactive dye from the aqueous solution. Materials and Methods: Bio-adsorbent prepared from pomegranate peel was successfully used to remove the reactive dye (Reactive Black 5) from the aqueous solution. The effects of major parameters such as pH, adsorbent dosage, and contact time on dye removal efficiency were studied. Statistical models were articulated based on selected variables to optimize the decolourisation efficiency of the adsorption process using a full factorial central composite design. Results: Dye removal efficiency of close to 100% was observed at a pH 12 using 1 g adsorbent/ 200 mL dye solution within a contact time of 60 min., yielding a virtually colourless solution. A fixed-bed column study with an initial dye concentration of 100 mg/L at bed depths of 4 cm, 8 cm, and 12 cm yielded a breakthrough time of 300 min, 570 min, and 780 min, respectively. Discussion: Langmuir, Freundlich, and Temkin isotherm models were applied to analyze the sorption equilibrium parameters. The experimental results of the analysis revealed that the Langmuir isotherm fits better than the other isotherms with a linear regression coefficient (R2) of 0.99. The high correlation coefficient (R² > 0.95) and low p-values (< 0.0001) indicate that the model and its terms are significant, making it effective for optimizing operational parameters and accurately predicting the response. Conclusion: The breakthrough curve serves as a tool to evaluate the effectiveness of the prepared adsorbent in real-world applications. The present work not only provides an alternative to commercially available activated carbon for dye wastewater colour removal but also emphasizes the importance of repurposing fruit residues, which could otherwise become environmental pollutants if improperly disposed of.

Combined ozonation-biological activated carbon process for antibiotic resistance control in treated effluent from wastewater treatment plant

Biological activated carbon (BAC) treatment plays a crucial role in wastewater treatment plants due to its economic and effective promotion of organic matter degradation or mineralization. However, whether the changes in antibiotic resistance (AR) resulting from BAC or O3-BAC treatment are related to environmental factors remains unclear, as previous studies have primarily focused on isolated aspects, or have combined these aspects without systematically comparing the BAC and O3-BAC treatment processes or analyzing their interrelationships. In this study, to gain a clearer understanding of the factors related to AR during the BAC treatment, the treatment process of BAC and O3-BAC were comprehensively compared, including antibiotics removal, wastewater matrix changes, antibiotic resistant bacteria (ARB), antibiotic resistance genes (ARGs), and bacterial community characteristics. The roles of O3 pretreatment and the bed depth of BAC were also clarified. ARGs were found to be not as sensitive to ozone as ARB. In addition, further strengthening of control measures should be needed for trimethoprim and tetracycline, due to their low removal efficiencies by ozone pretreatment, and their close relationship with the increased AR. Besides, 2 mg/L ozonation pretreatment could significantly influence the microbial community composition of wastewater and biofilm samples, while 1 mg/L ozonation could not. Finally, the correlation of environmental factors, bacterial communities, and ARGs revealed that to reduce the AR risks of O3-BAC treatment, antibiotics in wastewater should be strictly controlled, since they were positively correlated with the accumulation of ARGs and Pseudomonadota, Actinomycetota, and Bacteroidota, which were responsible for carrying and disseminating ARGs. The results showed that higher dose ozonation pre-treatment and longer bed depth of BAC process could help control the AR of BAC.

Removal of sulfamethoxazole using Fe-Mn biochar filtration columns: Influence of co-existing polystyrene microplastics

Emerging contaminants, particularly antibiotics and microplastics (MPs), present significant challenges in wastewater treatment and pose large ecological risks. This study investigates the removal efficiency of sulfamethoxazole (SMX) using Fe-Mn modified biochar (BFM) in fixed bed filtration columns, emphasizing the effect of the presence of polystyrene microplastics (PS-MPs) on SMX behavior in both water (pH ≈ 5.6) and selected wastewater (pH ≈ 8) systems. Batch sorption results show that 10 mg/L SMX in 50 mL water can be completely removed by 100 mg BFM sorbent. The Bed Depth Service Time model indicated the BFM column is feasible for SMX removal in scaled-up continuous wastewater flow operations, while the Yan model best elucidates SMX filtration behavior and suggests the dominant adsorption mechanisms include external mass transfer and intraparticle diffusion. The present of both 20 mg/L and 100 mg/L PS-MPs (pH ≈ 5.6) significantly reduced SMX retention due to competitive sorption. However, at pH 3.2, competitive sorption became negligible due to electrostatic interactions driving the PS-MPs sorption, while neutral charged SMX bound through hydrogen-bonds or π-π EDA interactions. Elevated pH shifted both PS-MPs and SMX sorption to non-electrostatic thus intensifying sorption competition, highlighting the influence of pH on their interaction dynamics. In wastewater, SMX filtration was slightly inhibited by 100 mg/L PS-MPs in BFM columns, whereas PS-MPs removal remained unaffected due to the high ionic strength and alkaline pH. These findings highlight the impact of MPs on pollution removal efficiency in filtration system, essential for enhancing biochar-based wastewater treatment strategies.

Batch and continuous adsorptive removal of brilliant green dye using modified jamun seed powder: RSM based optimization

Indian jamun seeds (JSs) were surface-modified with sulfuric acid in a 1:1 ratio of acid to adsorbent. The modified JS (MJS) was characterized using Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDX) techniques. Response surface methodology (RSM) via central composite design (CCD) was utilized to investigate critical parameters like pH, contact time, and initial concentrations. At the optimal condition, the MJS exhibited a maximum adsorption capacity of 123.5 mg g−1 for brilliant green (BG). The adsorption process followed Langmuir and Freundlich models, supported by the correlation coefficients. Kinetic studies suggest that the pseudo-second-order model better explains the experimental data compared to the first-order kinetic equation, indicating that intraparticle diffusion is not the sole rate-limiting step. Thermodynamically, the process was found to be spontaneous, exothermic, and with increased entropy. Regeneration studies revealed that the MJSs can be reused for three cycles without compromising their efficiency. Continuous studies showed that lower flow rates, lower initial concentrations, and higher bed depths resulted in better adsorption efficiency. In essence, this study demonstrates that JS offer a simpler and environmentally friendly approach to remediating wastewater containing BG.

Efficiency of Backwashing in Removing Solids from Sand Media Filters for Drip Irrigation Systems

Sand media filters are especially recommended to prevent emitter clogging with loaded irrigation waters, but their performances rely on backwashing. Despite backwashing being a basic procedure needed to restore the initial filtration capacity, there is a lack of information about the solid removal efficiency along the media bed depth. An experimental filter with a 200 mm silica sand bed height was used to assess the effect of two operation velocities (30/45 and 60/75 (filtration/backwashing) m h−1) and two clogging particles (inorganic sand dust and organic from a reclaimed effluent) on the efficiency of backwashing for removing the total suspended solids retained in different media bed slices. The average solid removal backwashing efficiency was greater with organic particles (78%) than with inorganic ones (64%), reaching its maximum at a 5–15 mm bed depth. A higher operation velocity increased the solid removal efficiency by 16%, using organic particles, but no significant differences were observed with inorganic particles. The removal efficiencies across the media bed were more uniform with organic particles (63–89%) than with inorganic (40–85%), which makes it not advisable to reduce the media height when reclaimed effluents are used. This study may contribute to future improvements in sand media filter design and management.

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.

PH-Responsive removal of dyes from wastewater using MXene composited L-Cysteine-grafted HEMA hydrogel: Dynamics, selectivity, regeneration and mechanism

In this work, a MXene composited cysteine-grafted hydroxyethyl methacrylate hydrogel (PHGC/MXene) was successfully synthesized, exhibiting excellent cycle stability and high selectivity toward ionic dyes at different pH. In mixed dyes system, PHGC/MXene exhibited remarkable adsorption selectivity and excellent property of pH-responsivenes for methyl blue (AB93) at pH=2.0 and for methylene blue (MB) at pH=11.0, with maximum adsorption capacity of 207.47 mg/g and 555.56 mg/g, respectively. Even after 12 desorption-regeneration cycles, the removal rates for AB93 and MB remained above 90 %. The study further analyzed the dynamic fixed-bed adsorption behavior of PHGC/MXene for MB, revealing optimal conditions at an inlet concentration of 75 mg/L MB dye and a bed depth of 9 cm. The adsorption mechanism was proposed combined with molecular dynamics simulations. PHGC/MXene emerges as an easily synthesized, highly selective adsorbent with significant potential for the purification of dyes from wastewater in both strongly acidic and strongly alkaline environments.

The Atmospheric water harvesting by using Neodymium Metal Organic Framework (MOF-417)

The capture of tidy water from damp air without having the use of bulky instruments or large amounts of energy, has made appeal as a possible eco-friendly substitute to traditional water collecting methods. Metal-organic frameworks (MOFs) offer prospects for this application due to their structural flexibility, which allows for the straightforward, scalable adjustment of structural and functional elements. Here, we have tried to provide a parameter-based analysis of hydrolytically stable MOFs of varying structures to explore the physical properties to control the speed of water storage in this type of material and to search for its overall adsorbing capacity by weight. Examination of temperature, humidity and powder bed depth to determine ideal parameters for adsorption and desorption was performed. MOF-417 has potential and able to produce 0.5 litre water per kilogram of MOF in a day.

Batch and continuous fixed bed adsorption of copper (II) from acid mine drainage (AMD) using green and recyclable adsorbent from cellulose microcrystals (CMCs)

The CMCs are viable materials for applications in industry and process innovation for removing heavy metal ions since they may be used in static and dynamic adsorption processes. It is necessary to develop simple, low-cost water treatment methods that use organic, biodegradable polymers such as nanomaterial-modified cellulose microcrystals. The column technique was used to investigate the effects of operational parameters such as pH, bed depth, concentration and flow rate. The input concentrations of 20, 40, 80 and 120 mg L−1, feed flow rates of 5, 10, 15 and 20 mL min−1, and bed heights of 5, 7.5, 10 and 12.5 cm. Experimental findings showed that the adsorption capacity decreased with increasing flow rate and increased with bed depth and input concentration, which were among the breakthrough parameters evaluated. The optimum adsorption capacity of 258.09 ± 0.96 mg g−1 was found to be achieved with an ideal pH of 6, an initial concentration of 200 mg L−1, a contact period of 300 min, and a dosage of 5 g/200 mL. The Langmuir model best fits the adsorption of indigo carmine, whereas the pseudo-second-order model, which governs the adsorption mechanism, may be described by physisorption combined with chemisorption. From a thermodynamic perspective, the adsorption was exothermic and spontaneous. In continuous adsorption, the Yoon-Nelson and Thomas models provided a good match for the hole curve, whereas the Bohart-Adams model fitted the breakthrough curve’s initial portion ((Ct/C0) <0.5) perfectly. A three-dimensional adsorbent that has been chemically modified. The chemically modified CMCs adsorbent was characterized using FTIR, SEM and TGA.