Fixed-bed Column Research Articles

Porous sodium alginate/cellulose nanofiber composite hydrogel microspheres for heavy metal removal in wastewater

High adsorption capacity, high adsorption rate and reusable adsorbents are urgent needed for removing heavy metals from wastewater. In this study, porous sodium alginate/cellulose nanofiber (SA/CNF) composite hydrogel microspheres were prepared by combining sodium alginate with cellulose nanofibers by microfluidics technology and adding polyethylene glycol (PEG) as pore making agent. The SA/CNF composite hydrogel microspheres could efficiently adsorb heavy metals (Pb2+, Cu2+ and Cd2+) in wastewater. The influencing factors of adsorption process, including pH, temperature, initial concentration, coexisting ions and aquatic environments, were systematically discussed. The adsorption process was more consistent with Langmuir isotherm model and pseudo-second-order model in batch system, indicating the adsorption process was mainly chemical adsorption. The adsorption capacity to Pb2+ obtained by Langmuir model was as high as 544.66 mg/g at 20 °C. Fixed-bed column adsorption experiments demonstrated the excellent performance of the as-prepared SA/CNF microspheres for treatment of the flowing wastewater in a column system. Overall, a highly practical adsorption process based on hydrogel adsorbents was developed for the removal of heavy metals from actual wastewater.

Adsorptive removal of a nitrate ion from the aqueous solution of sodium nitrate by application of double fixed-bed column

This study focuses on the removal of nitrate ions from aqueous solutions using rice husk activated carbon (RHAC). The RHAC was subjected to characterization via Fourier transform infrared (FTIR), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and X-ray florescence (XRF) to ascertain its functional groups, surface morphology, and oxide/elemental composition, respectively. Batch experiments were conducted to assess the impact of nitrate concentration, bed height, and number of packing layers on removal efficiency. FTIR spectra revealed favorable sorption-related functional groups within RHAC, while SEM analysis indicated the presence of effective sorption sites on its surface. EDS analysis of the rice husk adsorbent before adsorption (RHBS) demonstrated a significant composition of Si (42.20%), O (35.30%), and Ca (12.33%). The batch study unveiled a concentration-dependent decrease in nitrate removal efficiency, alongside the enhanced performance with increased bed height and number of packing layers. Kinetic data fitting favored the Yoon–Nelson and Adams–Bohart models. Overall, RHAC exhibited efficient nitrate ion removal, with column performance notably improved by utilizing multiple packing layers. These results will enhance our understanding of the mechanisms involved in removing nitrate ions and highlight the potential effectiveness of RHAC, especially when utilized with multiple packing arrangements in column setups.

Carbonization of golden shower pods to high surface area biochar for decontamination of cationic dyes and regeneration study by gamma radiations

Detoxification of water resources is the need of the hour and a number of environment friendly materials are proposed by scientist to deal with water pollution issues. The present study deals with preparation and characterization of porous activated carbon from golden shower pods, a waste ligno-cellulosic biomass, for the removal of dye contaminants from aqueous solution. The synthesized material, golden shower biochar (GSBC) was characterized using various analytical techniques to confirm the presence of active sites. The BET analysis of GSBC revealed high surface area of 1120 m2/g with total pore volume of 1.099 cm3/g and average pore radius 19.618 Å. Operational parameters were optimized using batch studies by taking GSBC dose of 50 mg which showed complete removal of target dyes with an initial dye concentration of 200 mg/L with just 60 min interaction time; based on these results, a fixed bed column of GSBC was designed and column studies were performed. Adsorption isotherm studies were carried out using Langmuir and Freundlich models, of which Langmuir model was found to be best-fit with maximum adsorption capacities of 208.86 mg/g, 284.35 mg/g and 327.56 mg/g for Crystal violet, Brilliant green and Methylene blue dyes respectively. Analysis of kinetics and thermodynamics revealed that the best-fit model was pseudo second-order with spontaneous reaction course and exothermic nature. Regeneration was carried out using gamma irradiation of dye loaded GSBC, followed by leaching in alcohol. It was observed that a 30 KGy dose was just sufficient to completely degrade the dye on the adsorbent surface. GSBC has shown immense potential for eradication of dyes from water effluents and it is easily recovered with negligible loss in efficacy.

Engineering CALF-20/graphene oxide nanocomposites for enhancing CO2/N2 capture performance

Ever-increasing atmospheric CO2 concentrations has necessitated the development of novel and cost-effective nanostructured composites with favorable physicochemical properties. Recently, the potential of metal-organic framework (MOF)-based nanocomposites towards boosting CO2 capture capability has become apparent indicating the importance of the relationship between their structure and properties. Herein, a novel nanocomposite of zinc-based CALF-20 MOF hybridized with graphene oxide is successfully fabricated using the solvothermal method. The construction of the well-structured nanocomposite is confirmed by performing PXRD, BET, FTIR, FESEM/EDX, TEM, and TGA characterization analyses. CO2 and N2 adsorption capacities and CO2/N2 separation performance of these nanocomposites are evaluated by experiment and mathematical modeling for the first time. The CALF-20/GO interfacial interaction and CO2 adsorption mechanisms are also discussed. As the best-performing adsorbent, the CALF-20 containing 20 wt% GO indicates a 42.6 % increment in CO2 uptake at 1.6 bar and a 32.7 % enhancement in CO2/N2 selectivity at 1 bar and 298 K and 1.28 times more CO2 retention time in a fixed bed column compared to that of the pristine MOF. The results show that the MOF and GO form chemical bonds at the interface resulting in generating new pore structures and increasing the porosity which are mostly responsible for boosting CO2 capture capacity. Interestingly, no meaningful effect is observed by the variation of the zinc atomic concentration at the surface. The simple synthesis procedure and understanding the interfacial structure of the novel CALF-20/GO composite as a promising adsorbent for CO2 capture applications can provide new insights for future work.

Novel ternary nanocomposite (TiO2@Fe3O4-chitosan) system for nitrate removal from water: an adsorption cum photocatalytic approach.

Nitrate pollution of water emerging from various anthropogenic activities has become a major environmental concern because of its deleterious effects on natural water resources. The present work deals with the synthesis of the ternary nanocomposite based on chitosan, iron oxide (Fe3O4), and titanium dioxide (TiO2) and its application for the removal of nitrates from model-contaminated water. Fe3O4 derived through a coprecipitation method was incorporated into the chitosan matrix which was fabricated in the form of beads. The wet gel beads were then successfully coated with sol-gel-derived silver-doped titanium dioxide sol followed by drying under suitable conditions to get the functional nanocomposite beads. The synthesized functional materials were further characterized for their structural, morphological, and textural features using X-ray diffraction analysis, physical property measurement (PPMS), Fourier transform infrared (FTIR) analysis, UV visible spectroscopy analysis (UV-vis), BET surface area analysis (BET), field emission scanning electron microscopic (FESEM), and transmission electron microscopy (TEM) analysis. The ternary nanocomposites were further used for the removal of nitrates via adsorption cum photocatalytic reduction technique from the model contaminated water when subjected to an adsorption study under dark conditions and photocatalytic study under UV/visible/sunlight for a definite time. Fe3O4 in the nanocomposite provides enhanced adsorption features whereas the functional coating of titanium dioxide aids in the removal of nitrates through the photocatalytic reduction technique. The functional beads containing 3% Fe3O4 in the wet gel form (CTA-F3) have excellent nitrate removal efficiency of ~ 97% via adsorption cum solar photocatalysis towards the removal of nitrate ions from 50ppm nitrate solution, whereas the dried nanocomposite beads have got a nitrate removal efficiency of ~ 68% in 1h from 100ppm nitrate solution. Continuous flow adsorption cum photocatalytic study was performed further using the oven-dried functional beads in which flow rate and bed height were varied while maintaining the concentration of feed solution as constant. A nitrate removal efficiency of 65% and an adsorption capacity of 4.1 mgg-1 were obtained for the CTA-F3 beads in the continuous flow adsorption cum photocatalysis experiment for up to 5h when using an inlet concentration of 100ppm, bed height 12cm, and flow rate 5.0mlmin-1. A representative fixed-bed column adsorption experiment conducted using CTA-F3 beads for the treatment of a real groundwater sample shows reasonable results for nitrate removal (71.7% efficiency) along with a significant removal rate for the other anions as well. Thus, the novel adsorbent/photocatalyst developed is suitable for the removal of nitrates from water due to the synergistic effect between Fe3O4, chitosan, and titanium dioxide.

Highly efficient recovery of phosphate and fluoride from phosphogypsum leachate: Selective precipitation and adsorption

Phosphogypsum, a typical by-product in the phosphorus chemical industry, could generate a large amount of leachate containing phosphate and fluoride in the process of rainfall and long-term stacking, which not only causes serious environmental pollution, but also leads to a waste of resources. In this study, a united treatment of calcium hydroxide precipitation and lanthanum zeolite (La-ZFA) adsorption was proposed to achieve the recovery of phosphate and fluoride from phosphogypsum leachate. In phosphogypsum, most phosphorus could be leached except P in the residual occurrence form, while for fluoride, only water-soluble F could be effectively leached. The optimum leaching amounts of phosphate and fluoride were 22.59 and 4.64 mg/g, respectively, at liquid-solid ratio of 400:1, leaching time of 120 min, pH of 6.0, particle size of >200 mesh (<0.075 mm), and leaching temperature of 25°C. Using Ca(OH)2 as the precipitant, the phosphate could be precipitated selectively from phosphogypsum leachate by controlling pH and time, and the concentrations of it decreased significantly to 0.29 mg/L at pH 10.0, with a removal efficiency of 99.48%. XRD, SEM and Visual MINTEQ software analysis proved that the main component of the precipitate was hydroxyapatite (Ca5(PO4)3(OH)). After P precipitation, a series of sorbents for fluoride were investigated, and La-ZFA sorbent was chosen and utilized to recover the fluoride from the leachate through a cyclic fixed-bed column. The efficiency of La-ZFA was basically not affected by the high concentration sulfate, and it can selectively adsorb fluoride from phosphogypsum leachate, leading to a final fluoride concentration of 0.29 mg/L in the effluent. The characterization demonstrated that fluoride might be adsorbed onto the La-ZFA via ligand exchange with hydroxy groups. The proposed method in this study is expected to sequentially recover phosphate and fluorine from the leachate of phosphogypsum, and it has great guiding significance for resource utilization and management of phosphogypsum.

Response surface modelling and optimization for copper removal from acid mine drainage using oxidized Himalayan pine needle biochar

ABSTRACT This study aims to investigate and compare the adsorption behaviour of pine needle biochar (PNB) and H2O2-oxidized PNB (OPNB) in eliminating Cu(II) from acid mine drainage. The PNB and OPNB adsorbents undergo comprehensive characterization through various techniques (BET, FTIR, SEM, and pHPZC). A central composite design was employed for designing experiments and optimizing the impact of process factors (metal concentration, adsorbent doses, contact time, and pH) on adsorption capacity. Pseudo-first-order, pseudo-second-order, and intra-particle diffusion kinetics models as well as Langmuir, Freundlich, and Temkin isotherm models were used to analyze the experimental data. Langmuir isotherm best fit (R2 &amp;gt; 0.99) the experimental data and adsorption capacities of 29.49 and 102.04 mg/g, were determined for PNB and OPNB, respectively. Under optimized experimental conditions, desorption studies revealed the reusability of OPNB about 80% even after four cycles. Fixed-bed column experiments were conducted at ambient temperature with an initial Cu(II) concentration of 125 mg/L and 5.0 g of adsorbent, utilizing a flow rate of 1 mL/min for both PNB and OPNB. These results indicate that oxidized biochar, synthesized for Cu(II) remediation, not only addresses Himalayan pine needle concerns sustainably but also exhibits potential applicability for removing other metal ions from aqueous environments.

Development of biochar using herbal industry waste for removal of hexavalent chromium from aqueous solution: Column study

Biochar is an rich source of carbon formed through biomas’s thermal decomposition. There is a lot of scope of interest in developing biochar derived from biomass in various disciplines to address the most significant ecological challenges. In the present study herbal waste collected from herbal processing industry (Bangalore, India). So, this biomass will be no use after the extraction process. Hence, present work mainly concentrates the conversion this herbal waste to biochar (BC). Research highlights the BC was prepared from herbal industry waste using pyrolysis method. The obtained BC used as adsorbent for adsorption of Cr (VI) from aqueous solution. A characterization of BC was performed using XRD, SEM-EDS and FT-IR which confirms the material. The adsorption experiments were carried out using batch and fixed bed column. The experimental studies were carried out at room temperature with initial Cr (VI) concentrations (IC) of 10–120 ppm using an adsorbent dosage (AD) of 0.05–0.55 g, agitation speed of 150 rpm for contact time (CT) 15–165 min and temperature (20–40 °C). Then various parameters for column study like bed height, flow rate and IC were also studied. The maximum removal of Cr (VI) was 88 % found at a pH 2, AD 0.55g, CT 90 min, and IC 100 ppm at 30 °C. For column study: higher removal of Cr (VI) achieved by bed height (BH) of 6 cm and at lower flow rate (FR), of 3 mL/min.

Xanthium Strumarium based activated carbon as low cost bioadsorbent for efficient removal of antidepressant drug Imipramine

Abstract Although, the pharmaceutical industries have contributed to improve the quality of human lifestyle. However, due to the extensive growth in living standards of modern society is one of the reasons that reinforce to millions of peoples to follow unhealthy lifestyle that leads to several health issues (like mental illness, disability and several metabolic problems etc.) it reinforces the over-dependency on pharmaceutical drugs. Among various pharmaceuticals, the tricyclic antidepressants (TCAs) have consumed significantly for the treatment of psychiatric disorders. The drug Imipramine (IMP) is one of the potential candidates among these TCAs, which is frequently used drug across the globe. That is why these TCAs are frequently detected pharmaceuticals in environment and negatively affect living organism. The levels of contamination of these TCAs in the environment have increased due to COVID-19 pandemic which consequently increased psychiatric disorders such as anxiety and depression in a significant population. The Imipramine contamination has harmful impact on human such as hypotension, cardiac arrhythmias, convulsions and hypothermia. The present study witnessed an effective removal of the Imipramine contamination from aqueous effluent using Xanthium Strumarium based low cost bio-adsorbent. The thermal activation was done to produce powdered bioadsorbent (XPT1) for Imipramine removal from its aqueous phase. The batch experiments were performed to access adsorption parameters like contact time (2 hours), maximum adsorption capacity (3.74 mg/g), optimum pH (less than 5 and more than 9) and adsorption capacity dependence on concentration and temperature of produced bioadsorbents. The fixed-bed column experiment was carried out to attain saturation time (626 minutes), adsorption capacity (64.9 mg.g−1) with 90.08 % of total removal percent of Imipramine. The adsorption isotherm data were best fitted to Freundlich model at low temperature 303 K, while at higher temperature the Imipramine adsorption is well fitted with both Langmuir and Freundlich models.

Direct filtration of low-turbidity water by fixed-bed ion exchange treatment

In drinking water treatment, low-turbidity water (e.g., < 5 NTU) is often purified by direct filtration comprising coagulation, flocculation, and rapid sand filtration. This study assessed the potential of replacing the rapid sand filter with a fixed-bed ion exchange column. Two types of anion exchange resins, polyacrylic (Purolite A860) and polystyrene (Purolite A502PS), were used in fixed-bed columns without preceding coagulation and flocculation. After the first use of the new resins (14-h operation), the A860 column showed more significant head loss buildup than the A502PS column (151 and 101 cm, respectively). This can be attributed to the effective size of A860 resins (0.38 mm), which was smaller than that of A502PS resins (0.52 mm). A860 resins were superior to A502PS resins in filtrate quality. The A860 resins achieved filtrate turbidity (0.16–0.26 NTU) lower than the A502PS resins (0.19–0.35 NTU). Similarly, dissolved organic carbon removal by A860 resins (25–37 %) was higher than that by A502PS resin (15–25 %) due to the low hydrophobicity of the feed water. Air scouring and water backwashing were ineffective in regenerating A860 resins. In contrast, cleaning with a NaCl solution (pH = 12) partially recovered the capacity of A860 resins for turbidity removal.

Mesopore Catalytic Activated‐Carbon to Reduce Harmful Gases Indoors: Adsorption, Catalytic Oxidation, and Prediction Mechanism

ABSTRACTModification of local bamboo‐based catalytic activated carbon with metallic Ag can produce mesopore and micropore types, with a mesopore content of 86%. One of the best ways to reduce formaldehyde concentrations is through catalytic adsorption. In combination with Ag nanoparticle catalyst, formaldehyde adsorption capacity is improved. Adsorption and oxidation reaction experiments are performed in a fixed bed column (di = 10 mm, length = 90 mm). The increase in formaldehyde adsorption associated with the reaction rate of formaldehyde oxidation by metallic Ag is 51 g/mmol. The oxidation reaction of Ag nanoparticles is a bimolecular reaction based on the Langmuir–Hinshelwood mechanism. Formaldehyde can be reduced by 59% and 41% through the role of adsorption and support of catalytic oxidation, respectively. Additionally, harmless gases such as CO2 and H2O are produced within the column.

Fixed bed column adsorption systems to remove 2,4-Dichlorophenoxyacetic acid herbicide from aqueous solutions using magnetic activated carbon

The widespread use of 2,4-Dichlorophenoxyacetic acid (2,4-D) as a weedkiller has resulted in its persistence in the environment, leading to surface and groundwater pollution. In this study, the fixed bed column experiments were performed to remove 2,4-D from aqueous solutions using magnetic activated carbon derived from Peltophorum pterocarpum tree pods. The evaluation was done on effects of operating parameters such as bed depth (2–4 cm), influent flow rate (4.6–11.4 mL/min), and 2,4-D concentration (25–100 mg/L) on the breakthrough curves. The data fit well with the Yoon-Nelson and Thomas models, exhibiting high R2 values. Results indicated that lower flow rates, lower 2,4-D concentrations, and greater bed depths enhanced adsorption capacity, achieving up to 196.31 mg/g. Reusability studies demonstrated the material's potential for repeated use, while toxicity studies with Vigna radiata seeds confirmed the effectiveness of Fe3O4-CPAC in removing 2,4-D. This investigation highlights the promising application of Fe3O4-CPAC in fixed bed adsorption systems for efficient 2,4-D removal.

Remediation of lead toxicity with waste-bio materials from aqueous solutions in fixed-bed column using response surface methodology

Heavy metal ions pose significant risks to human health, pelagic, and several other life forms due to perniciousness, tendency to accumulate, and resistance to biodegradation. Waste bio-materials extend a budding alternative as low-cost adsorbent to address the removal of noxious pollutants from wastewater on account of being cost-effective and exhibiting exceptional adsorption capacities. The current exploration was accomplished to gauge the performance of raw and modified human hair concerning lead scavenging in a down-flow fixed bed column. The appraisal of column performance under varying operational parameters encompassing bed height (15–45 cm), influent metal ion concentration (60–140 mg L−1), and a solution flow rate (20–40 mL min−1) was performed by breakthrough curve analysis. The consequences acquired were evaluated using the Yoon Nelson, Thomas, Adam-Bohart, and Bed Depth Service Time (BDST) model. Among these employed models, Bed Depth Service Time (BDST) and Thomas models exhibited the highest R-squared value compared to the Yoon Nelson and Adam-Bohart's model for most cases. In addition, the optimization of lead adsorption was followed using the Box-Behnken design of response surface methodology (RSM). The optimal conditions (desirability-1.00) for achieving a goal of maximum percent removal of lead ions were marked to be a bed height of 42.79 cm, solution flow rate of 20.92 mL min−1, and an initial metal concentration of 139.51 mg L−1. Under these optimized conditions, the percent amputation of lead in a fixed bed was observed to be 82.31 %, while the results of the experiment performed approximately under these optimized conditions revealed a percent removal of 85.05 %, reflecting a reasonable conformity with values acquired through Box-Behnken design.

Consolidation and cytotoxicity analysis of a purification strategy for biotechnological xylitol production using fixed bed column adsorption and nanofiltration membranes

Agro-industrial waste is increasingly utilized in biotechnological processes to convert lignocellulosic materials into high-value products, such as xylitol. This polyol can be produced using biotechnological methods that mitigate environmental impacts, but it entails high purification costs. The article proposes a comparative study between two sequential strategies for purifying biotechnological xylitol. The first strategy involves membrane filtration followed by column adsorption. While the second strategy only covers column adsorption with twice the adsorbent bed. Additionally, the study includes a cytotoxicity evaluation of various purified xylitol fractions. Column adsorption was conducted at 70 °C with a flow rate of 1.2 mL min−1 using activated carbon as the adsorbent. It proved to be efficient in separating colored compounds, proteins, and ethanol, with retention coefficients of 99.23 %, 84.0 %, and 96.71 %, respectively. The purification factor of xylitol/ethanol was 14.84. Nanofiltration was performed using a poly (piperazine amide) membrane at 40 °C and 30 bar, resulting in a protein retention of 43.55 % and a xylitol purity of 27.73 %. Finally, purified xylitol fractions underwent cytotoxicity analysis using the MTT assay, conducted in intestinal epithelial cells (Caco-2). One of the analyzed fractions did not induce toxicity, demonstrating that activated carbon column adsorption was the most effective strategy for purifying biotechnologically produced xylitol. These findings contribute to enhancing the viability of biotechnological xylitol production from sugarcane bagasse hemicellulosic hydrolysate.

Self-assembled mesoporous silica decorated with biogenic carbon dot nanospheres hybrid nanomaterial for efficient removal of aqueous Methoxy-DDT via a Short-Bed Adsorption column technique

Methoxy-DDT is an organochlorine pesticide extensively used in agricultural practices as a DDT substitute. Methoxy-DDT has been found and quantified in several investigations in groundwater, drinking water, sediment, and various biota. Therefore, designing efficient and cost-effective adsorbents for removing methoxy-DDT is vital. In this work, we embedded Ficus benghalensis L. derived carbon dots (CDs) in mesoporous silica (MS) to fabricate MS-CDs nanohybrid material. MS-CDs nanohybrid exhibited remarkable selectivity and removal efficiency towards methoxy-DDT, outperforming other endocrine disruptors. Parameters for industrial-scale fixed-bed adsorption columns, such as bed capacity, length, and breakthrough times, were analyzed. The kinetic study revealed that pseudo-second-order (PSO) adsorption and isotherm analysis confirmed the Langmuir model as the best fit. Small bed adsorption (SBA) column analysis was carried out using spiked Yamuna river water, and the breakthrough curves were demonstrated by varying MS-CDs bed height. The maximum adsorption capacity obtained for methoxy-DDT was 17.16 mg/g at breakthrough and 49.98 mg/g at exhaustion. The adsorbent showed 86.53% removal efficiency in the 5th cycle, demonstrating good reusability. These results indicate that the developed material MS-CDs-based organic sphere is an effective adsorbent for aqueous methoxy-DDT adsorption and can be applied to wastewater treatment.

Fabrication of granular three-dimensional graphene oxide/UiO-66 adsorbent for high uranium adsorption: Density functional theory and fixed bed column studies

This study presents a thorough investigation of the novel application of graphene oxide (GO) modified with melamine formaldehyde to fabricate granular three-dimensional GO (3D-GO), followed by the introduction of UiO-66 doping (3D-GO/U) for high uranium (U) adsorption. The U(VI) adsorption isotherms revealed that 3D-GO/U-10 with 10 % UiO-66 incorporation exhibited an impressive adsorption capacity of 375.5 mg g–1 and remained high U(VI) sorption performance in wide pH range. The introduction of UiO-66 to 3D-GO (3D-GO/U-10) led to the deagglomeration of the UiO-66 particles. The in situ surface-enhanced-Raman-spectroscopy-analysis and density-functional-theory simulations showed the symmetric metal center site Zr–O2 on UiO-66 was discovered to exhibit the highest adsorption energy (–3.21 eV) for U(VI) species due to the electrons transfer from the oxygen atom to U(VI) drives the covalent bonding between the symmetric metal center sites Zr–O2 and U(VI) on 3D-GO/U-10. The 3D-GO/U-10 was regenerated using a 0.1 M Na2CO3/0.01 M H2O2 solution and achieved up to 89.7 % U(VI) removal in the 5th cycle. The continuous flow column experiments results revealed 3D-GO/U-10 can regenerate and maintain a U(VI) removal capacity of ∼76 % for up to 4 cycles column experiments. Therefore, 3D-GO/U-10 exhibits great potential for removing U(VI) from water bodies.

Design parameters for fixed bed column of biosorbent developed from Syagrus romanzoffiana for the removal of mono and multicomponent metallic ions

A biosorbent produced from Jerivá coconut (Syagrus romanzoffiana) was utilized for removal of Cd2+, Cu2+, Ni2+, and Zn2+ ions in both single and multi-component systems. Adsorption equilibrium batch tests indicated that the Langmuir model best represented the adsorption of both mono and multi-component metal ions, with the multi-component adsorption classified as antagonistic. Among the desorbing solvents tested, 0.1 M H₂SO₄ was the most effective, achieving recovery efficiencies of 98.2 % for Cu2+, 77.9 % for Zn2+, 69.9 % for Cd2+, and 29.4 % for Ni2+. Continuous system tests were performed with an initial concentration of 25 mg L−1 for each metal in the single-component setup and a total concentration of 100 mg L−1 in the multi-component mixture. To evaluate the biosorbent's efficiency in adsorbate recovery, 4 cycles of adsorption-desorption were conducted in a fixed-bed column, revealing a gradual decrease in desorption efficiency over successive cycles. The biosorbent desorbed all four metal ions within approximately 40 min. Cu2+ was the most desorbed ion (193.1 mg L−1), followed by Cd2+ (98.6 mg L−1), Zn2+ (66.2 mg L−1), and Ni2+ (51.7 mg L−1). The operational parameters of the fixed-bed column demonstrated good adsorption performance after column regeneration.

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.

Transforming a mixture of real post-consumer plastic waste into activated carbon for biogas upgrading

Plastic waste management is a current environmental issue that demands potential solutions since complete mechanical recycling is limited to the complexity and feasibility regarding the quality and purity of plastic waste. Pyrolysis has emerged as a reasonable solution for the recycling of those fractions that are not further suitable for recycling. Although the implementation of this technology is mature, the generated solid fraction or char has not been completely inserted in the closed loop of plastic recycling. This work explores the possibility of using the carbonaceous char as a precursor for the preparation of porous activated carbons for environmental application as CO2 adsorbent and biogas upgrading. The effect of the pyrolysis temperature (450 or 500 ºC) on the obtained chars has been assessed for the benefits in the second stage of chemical activation, exploring the possibility of the use of diverse chemical agents. The composition, textural, and surface properties of the porous materials were characterized. N2 isotherms showed that the char prepared at 500 ºC provided the best textural properties with a performance of K2CO3 ∼ KOH > Na2CO3 > NaOH > ZnCl2 > FeCl3. Isotherms of CO2 adsorption showed that the activation with K2CO3 displayed the best uptake (130.2 mg g−1 at 273 K), closely followed by KOH (125.0 mg g−1 at 273 K), also confirmed by dynamic tests in a fixed bed column configuration. The uptake was well correlated with the ultramicropore volume and the oxygenated functional groups. The CO2 and CH4 adsorption were studied either in static or dynamic assays. The behavior of the sample activated with K2CO3 was studied in detail in column tests, suggesting that the activated material exhibits promising behavior for biogas upgrading.

Boron adsorption from aqueous solutions through column study: desorption mechanisms, regeneration techniques, and kinetic insights

Recovering boron from aqueous solutions presents a significant opportunity for enhancing sustainable resource management and reducing costs within the oil and gas industry. This research focuses on evaluating newly synthesized adsorbents. Specifically, it investigates the boron adsorption and desorption in fixed bed columns of 25 cm in length and 2.5 cm in diameter, utilizing bed depths at 2.5, 5, 7.5 and 10 cm. Four different flow rates (2, 4, 6, and 8 mL/min) were used, all maintaining constant concentrations of 85 mg/L, which were determined as optimal through prior batch studies. In boron breakthrough, the maximum and minimum points ranged from (60,12) minutes to (280,100) minutes, respectively, across different experimental conditions. The maximum uptake (qe) reaches 22.86 mg/g, and the minimum uptake was 5.85 mg/g with bed heights of 2.5 cm and 10 cm, respectively. The kinetic analysis revealed that the Thomas model provided a strong fit for boron extraction, having R2 ratings between 0.9 and 0.95. The efficiency of boron desorption reached 75 %. Notably, boron extraction using Derived Boron Adsorbent)DBA( 160 mg under conditions of a 10 cm bed depth, 48 cm3 pore volume, and a flow rate of 6 mL/min. The research conclusions show how well DBA works to adsorb boron from aqueous solutions and show significant insights into the adsorption and desorption process. Therefore, DBA was selected as the preferred method for boron adsorption because of its exceptional ability to absorb boron efficiently and its high sorption capacity.