Search Results (649)

Melanin-based biosorbents (MiCS), derived from chestnut shells, were encapsulated in sodium alginate to obtain MiCS@Alg, useful in a column adsorption study. MiCS contains various acidic surface groups able to participate in the removal of cationic pollutants from aqueous solutions. The MiCS and MiCS@Alg were characterized by Fourier-transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Dynamic Light Scattering (DLS), while zeta potential and particle size analyses were performed to gain deeper insight into surface charge behavior. Batch adsorption experiments were carried out at three different temperatures, demonstrating that the adsorption kinetics followed a pseudo-second-order (PSO) model and that the Freundlich model best described the equilibrium data. The process was found to be endothermic and spontaneous, with maximum adsorption capacities of 300.2 mg g⁻¹ (BR2), 201.5 mg g⁻¹ (BY28) and 73.08 mg g⁻¹ (NH₃) on MiCS, and 189.3 mg g⁻¹ (BR2), 117.1 mg g⁻¹ (BY28) and 50.06 mg g⁻¹ (NH₃) on MiCS@Alg at 45 °C and compared with the unmodified chestnut shell. The MiCS and MiCS@Alg exhibited good adsorption performance, improved environmental compatibility, and greater reusability. Overall, these results highlight MiCS@Alg as a cost-effective, sustainable, and highly promising novel biosorbent for the removal of cationic pollutants (BR2, BY28, and NH₃) from water. Full article

During rapid social and economic growth, large amounts of organic matter, nitrogen, and phosphorus are released into the environment with wastewater, and constructed wetlands (CWs) play a key role in water pollution prevention and control. This study employed six test columns to evaluate the pollutant removal performance of various filter media combinations in CWs when treating synthetic sewage under different pollution and hydraulic loads. The results showed that all columns containing bio-ceramsite exhibited superior pollutant removal performance, especially for organics and phosphorus. A synergistic effect was observed between bio-ceramsite and volcanic rock in enhancing pollutant removal, with average removal rates of 88.02%, 69.69%, 62.96%, and 88.22% for COD, NH₄⁺, TN, and TP, respectively, under the nine experimental conditions. Scanning Electron Microscopy (SEM), BET surface area testing, and microbial community structure analysis were conducted to investigate the reasons for the differences in pollutant removal efficiency among the columns. The results showed that bio-ceramsite exhibits a highly microporous structure and a large surface area of 1.3816 m²/g, which provides abundant adsorption sites for microorganisms and pollutant molecules. The microbial community structure on bio-ceramsite remained highly consistent across all column tests, with dominant microbial species playing a key role in enhancing pollutant removal efficiency. The conclusions of this study indicate the potential application of some filter media combinations in CW design for environmental conservation. Full article

Metal contamination poses serious environmental and human health risks, which results in the need for low-cost remediation approaches. The utilization of agricultural byproducts for the removal of metal contaminants is considered cost-effective and environmentally sustainable. Garlic byproducts are rich in sulfur-containing compounds, and various functional groups contribute to metal binding. This study aimed to evaluate the potential of garlic stem and peel for the removal of cadmium (Cd), lead (Pb), and arsenic (As) from aqueous solutions and for their immobilization in contaminated soils. Batch sorption experiments conducted at pH 7 for 24 h showed that garlic stem removed 71.5% of Cd and 70.8% of Pb, while garlic peel achieved 65.4% and 79.4% removal, respectively. The higher Pb removal by garlic peel might be attributed to its higher sulfur content. However, both byproducts were less effective in removing As(III) and showed negligible removal of As(V), as these species predominantly occur in neutral or negatively charged species at neutral pH, resulting in weak interactions with negatively charged surface functional groups. Soil incubation experiments were conducted using 1% and 5% amendments of garlic stem and peel in Pb- and As-contaminated soils. Extractable Pb concentrations significantly increased in soils treated with 1% garlic peel because of the formation of labile complexes of Pb with dissolved organic carbon. However, a column experiment to evaluate the impact on Pb mobility under saturated and unsaturated conditions showed that Pb concentration in soil pore water decreased with garlic stem. Pb concentration was lower under saturated conditions, possibly due to the precipitation of Pb as PbS. Although the short-term application of raw agricultural byproducts increased extractable metal concentrations, long-term incubation reduced Pb levels in pore water. These findings suggest that unmodified garlic stem is a promising, cost-effective amendment for Pb immobilization in soil. Nevertheless, caution is needed in its application to prevent unintended metal mobilization in soil. Full article

Nucleosides are of significant interest to biomedical and pharmaceutical research and have been successfully separated in hydrophilic interaction liquid chromatography (HILIC). However, there have been few studies focusing on the retention mechanisms, and detailed retention mechanisms are not clearly understood. The quantitative assessment methodology based on the linear relationship between the observed retention factors and the phase ratio has been shown to be a new tool to investigate the retention mechanisms of polar compounds in HILIC. This study evaluated the retention mechanisms of 16 nucleosides on a bare silica column. The retention contributions by partitioning, adsorption, and electrostatic attractions are quantitatively determined, and the main retention mechanism can be unambiguously identified for each nucleoside. The study results indicate that the main retention mechanism can shift with the salt concentration in the mobile phase, but partitioning seems to dominate at higher salt concentrations. In addition, the partitioning coefficients are measured using the quantitative assessment methodology and have a relatively strong correlation with the log P values of the nucleosides. Considering large errors in the log P values for these very polar compounds, the partitioning coefficients measured experimentally in the HILIC system may provide a more accurate measure for polarity assessment. Full article

Rice is one of the world’s most consumed foods, and the cereal that most efficiently uptakes and accumulates As, contributing to human health risk. Flooded rice fields alter Eh-pH conditions and, consequently, the proportion of As(III)/As(V), favoring their accumulation in the crop. The use of algae in paddy soils can improve fertility and C-stock and affect chemical conditions and As availability. This study aimed to evaluate the effect of algae application on: As adsorption capacity in paddy soils from Sado, Portugal, changes in pH-Eh conditions in the soil–water environment, and consequent As speciation. Batch-based As adsorption assays were performed with different solid–solution ratios and Chlorella minutissima algae application, and fitted to the Freundlich and Langmuir linear models. In semi-continuous column assays, simulating rice field conditions, the effect of algae on the pH-Eh of soil pore water was evaluated. The soil quality assessment showed pseudo-total contents of As and other elements higher than Portuguese agriculture limits (11 mg As kg⁻¹), but their availability was low, posing no environmental risk. The studied soils had great As adsorption, which increased with algae application (1.07 mg g⁻¹). Algae application favored oxygenation, increasing Eh values, and maintaining As(V) species. This indicated a potential approach to reducing As(III) mobility. Full article

The presence of impurities Fe and trace radioactive U in rare earth elements (REEs) may lead to a significant decline in the performance of high-purity rare earth products. For deep removal from REEs in a green and efficient way, an amine-functionalized silica-based adsorbent, TNDA/SiO₂-P, was prepared by a simple vacuum impregnation method, which had a high organic loading rate of 31.2 wt.%. The experimental results showed that it exhibited good adsorption selectivity for uranium and iron, with separation factors SF_U/REE = 20147 and SF_Fe/REE = 88128 in 5 M HCl. The adsorption kinetics was fast, with equilibrium obtained in 120 min. The 0.1 M HCl can desorb U and Fe efficiently. The deep removal of U and Fe from REEs including Sc can be achieved through chromatographic column separation with high enrichment. FT-IR, XPS and DFT calculations mutually confirmed that protonated TNDA/SiO₂-P exhibited a selective mechanism for uranium and iron in complex anion species in the hydrochloric acid system. This demonstrates its potential for efficiently removing trace impurities U and Fe from REEs. Full article

According to the international standard ISO 14687:2019 for hydrogen fuel quality, the maximum allowable concentration of water in hydrogen for use in refueling stations and storage systems must not exceed 5 µmol/mol. Therefore, an adsorption purification process following the electrolyzer is necessary. This study numerically investigates the adsorption of water and the corresponding water loading on zeolite 13X BFK, based on the mass flows entering the adsorption column from three 5 MW electrolyzers coupled to a 15 MW offshore wind turbine. As the mass flow is influenced by wind speed, a direct comparison between realistic wind speeds and adsorption loading is presented. The presented numerical discretization of the model also accounts for perturbations in wind speed and, consequently, mass flows. In addition, adsorption isobars were measured for water on zeolite 13X BFK within the required pressure and temperature range. The measured data was utilized to fit parameters to the Langmuir–Freundlich isotherm. Full article

Methylene blue and safranin are dyes that may have harmful effects on both aquatic ecosystems and human health. This research aims to simulate an industrial-scale operational adsorption column for competitively removing these dyes from wastewater, employing Cedrela odorata L. as a bioadsorbent material. Aspen Adsorption (v.1) software simulated an industrial-scale packed-bed adsorption column under various configurations. Moreover, machine learning algorithms were applied to predict the results generated by Aspen, representing an advancement in the development of new strategies in this field. The kinetic model employed was the Linear Driving Force (LDF) model. Adsorption efficiencies of 96.1% were achieved for both methylene blue and safranin using the Langmuir–LDF model. The Freundlich–LDF model showed efficiencies of 94.8% for methylene blue and 96% for safranin. Meanwhile, the Langmuir–Freundlich–LDF model achieved up to 96.1% for methylene blue and 94.8% for safranin. This study demonstrated the feasibility of simulating the competitive adsorption of dyes in solution at an industrial scale using Cedrela odorata L. as a bioadsorbent. The application of LDF kinetic models and adsorption isotherms (Langmuir, Freundlich, and Langmuir–Freundlich) resulted in high adsorption efficiencies, highlighting the potential of this approach for the remediation of dye-contaminated effluents as a viable method for predicting the performance of full-scale packed columns. Machine learning algorithms were implemented in this research, obtaining R² higher than 0.996 for validation and testing stages for the responses of the model. Full article

Fine-grained intertidal sediments are typically characterized by low hydraulic conductivity and high nutrient loads, conditions that hinder biogeochemical recovery and exacerbate eutrophication. This study examined the feasibility of calcium-rich steel slag (SS) as a multifunctional capping material for improving both physical and chemical properties of cohesive sediments. Short-term (24 h) column experiments with two slag dosages (25 g and 50 g) revealed that the higher dosage (SS50) increased sediment hydraulic conductivity by 113.2%, likely through Ca²⁺-mediated flocculation and enhanced pore connectivity. Phosphate (PO₄-P) in pore water decreased by up to 64.1%, and effluent dissolved inorganic nitrogen (DIN) declined by 62.8%, indicating combined effects of Ca-driven precipitation, adsorption, and enhanced flushing. However, SS addition also raised pore water pH (to 11.8) and lowered redox potential, leading to transient phosphate release at the effluent boundary under reducing conditions. Cation analysis confirmed Ca²⁺ stability and Na⁺ reduction, suggesting improved sediment structural integrity. The results suggest that steel slag is a promising reactive capping material capable of enhancing permeability and controlling nutrient release in cohesive coastal sediments, yet further investigation into long-term ecological effects and dosage optimization is necessary. Full article

In the exploitation of ion-adsorption rare earth ores, the environmental effects of leaching agents are key constraints for green mining. Understanding the release behavior of typical heavy metals from soils under leaching conditions is of great significance. Laboratory column leaching experiments were conducted to systematically investigate the effects of three leaching agents—(NH₄)₂SO₄, Al₂(SO₄)₃, and MgSO₄—as well as varying concentrations of Al₂(SO₄)₃ on the release and speciation transformation of heavy metal Pb in mining-affected soils. The results revealed a three-stage pattern in Pb release—characterized by slow release, a sharp increase, and eventual stabilization—with environmental risks predominantly concentrated in the middle to late stages of leaching. Under 3% (NH₄)₂SO₄ and 3% Al₂(SO₄)₃ leaching conditions, Pb concentrations in soil increased significantly, with a higher proportion of labile fractions, indicating pronounced activation and risk accumulation. Due to its relatively weak ion-exchange capacity, MgSO₄ exhibited a lower and more gradual Pb release profile, posing substantially lower pollution risks compared to (NH₄)₂SO₄ and Al₂(SO₄)₃. Pb release under varying Al₂(SO₄)₃ concentrations showed a nonlinear response. At 3% Al₂(SO₄)₃, both the proportion of bioavailable Pb and the Risk Assessment Code (RAC) peaked, while the residual fraction declined sharply, suggesting a threshold effect in risk induction. All three leaching agents promoted the transformation of Pb in soil from stable to more labile forms, including acid-soluble, reducible, and oxidizable fractions, thereby increasing the overall proportion of active Pb (F1 + F2 + F3). A combined analysis of RAC values and the proportion of active Pb provides a comprehensive framework for assessing Pb mobility and ecological risk under different leaching conditions. These findings offer a theoretical basis for the prevention and control of heavy metal risks in the green mining of ion-adsorption rare earth ores. Full article

This work develops a novel phosphate-functionalized extraction resin (HEHEHP + Cyanex272)/SiO₂-P via the vacuum impregnation method for efficient separation of light rare earth element impurities from lanthanum (La³⁺) in nitric medium through synergistic extraction. Batch experiments have demonstrated superior adsorption selectivity toward impurity ions over La³⁺ in a pH 4 nitric acid solution. Column studies confirmed exceptional performance under ambient conditions, achieving a lanthanum treatment capacity of 120.6 mg/g and over 98% impurity removal, which surpasses most reported values. Notably, this purification process enables direct production of purified La³⁺ solutions through a single-column system without desorption, significantly enhancing efficiency and reducing costs. Mechanistic insights revealed combined ion exchange and coordination interactions between metal ions and P-OH/P=O groups, corroborated by advanced characterization and density functional theory calculations. These findings indicate a higher binding affinity of light rare earth compared with La³⁺. This strategy provides a scalable approach for ultra-high-purity lanthanum compound production in advanced optical and electronic applications. Full article

Natural zeolites have gained attention as low-cost adsorbents for the removal of heavy metals (HMs) from wastewater. However, their performance can be compromised by the presence of competing cations such as ammonium (NH₄⁺). This study investigated the competitive adsorption and desorption dynamics of NH₄⁺ and six HMs (Cd, Cr, Cu, Ni, Pb, and Zn) on two natural zeolites. Batch and column experiments using synthetic wastewater were conducted to evaluate the effects of different NH₄⁺ concentrations, pH, and particle size on HM removal efficiency and desorption effects. Results showed that increasing NH₄⁺ concentrations significantly reduce HM adsorption, with total capacity decreasing by ~45% at 100 mg/L NH₄-N in kinetic tests. Adsorption isotherms of the HM mixture for both zeolite types followed a clear sigmoidal trend, which was captured well by the Hill model (R² = 0.99), with loading rates up to 56.14 mg/g. Pb consistently exhibited the highest affinity for zeolites, while Cd, Cr, Ni, and Zn were most affected by NH₄⁺ competition in the column tests. Desorption tests confirmed that NH₄⁺ rapidly re-mobilises adsorbed metals, in particular Cd, Cu, and Zn. Slightly acidic to neutral pH conditions were optimal for minimising HM remobilisation. These findings underscore the need to consider competitive interactions and operational conditions when applying natural zeolites for HM removal, especially in ammonium-rich environments such constructed wetlands, soil filters, or other decentralised applications. Full article

This study investigates key factors affecting the adsorption behavior of proteins on the multimodal chromatographic adsorbent Capto MMC, aiming to enhance selective protein separation strategies. Batch equilibrium experiments were conducted using six model proteins to explore the combined effects of pH, ionic strength, and the nature of salts (kosmotropic and chaotropic) on protein–ligand interactions. Given that the Capto MMC ligand supports multiple interaction modes beyond cation exchange, particular focus was placed on acidic proteins (pI 4–5), which exhibited binding even at moderately elevated pH values—conditions ineffective for conventional cation exchangers. Hydrophobic interactions were identified as critical for stable binding of proteins like BSA and fetuin, while hydrophilic proteins such as ovalbumin showed minimal adsorption. Chromatographic column experiments were performed to evaluate elution performance under various buffer conditions, revealing that prolonged adsorption phases can reduce recovery yields for proteins with less stable tertiary structures. The findings highlight how salt type, pH, and protein hydrophobicity interplay to modulate multimodal binding mechanisms, providing practical insights for the design of tailored purification protocols. Full article

Terbium-161 (¹⁶¹Tb) is an emerging β⁻-emitting radionuclide of high interest for targeted radionuclide therapy. However, its reactor-based production presents significant challenges in the efficient separation of ¹⁶¹Tb from target ¹⁶⁰Gd and co-produced ¹⁶¹Dy. In this study, the separation of ¹⁶¹Tb by a solvent-impregnated resin P350@resin has been evaluated. A combination of static adsorption and dynamic column experiments was conducted to investigate the separation behavior of Gd³⁺, Tb³⁺, and Dy³⁺. Optimal separation performance was achieved at 0.4–0.6 mol/L HNO₃, using a column bed height of 20–28 cm and flow rates of 0.5–1.0 mL/min. A two-step elution protocol enabled near-baseline resolution between Tb and Gd, Dy within 3 h, ensuring high-purity and fast product recovery. Comprehensive characterization using SEM-EDS, FT-IR, and XPS confirmed that metal ion uptake occurs via coordination with phosphoryl groups on the resin. The P350@resin thus enables a simple and selective separation platform for the production of no-carrier-added ¹⁶¹Tb, with high potential for clinical radiopharmaceutical manufacturing. Full article

Ammonia emissions in poultry houses are common and pose health concerns for animals and workers. However, effective control of these emissions with sustainable products is lacking. Therefore, we investigated if an agricultural byproduct, cottonseed hulls, could be recycled through pyrolysis and used to remove ammonia from air. In this study, the efficacy of ammonia removal was observed using cottonseed hull biomaterials pyrolyzed at seven different temperatures: 250, 300, 350, 400, 500, 600, and 700 °C. In this study, ammonia was passed through a column filled with pyrolyzed material, and ammonia in the filtered air was monitored. The results showed that materials pyrolyzed at intermediate temperatures of 350 and 400 °C were the most efficient at ammonia removal and were able to adsorb approximately 3.7 mg NH₃/g of material. Despite extensive characterization, ammonia adsorption could not be linked to intrinsic material properties. Evaluation of the materials showed that the carbon in the pyrolyzed materials would be stable over time should the spent material be used as a soil amendment. Full article