Multilayer Adsorption Research Articles

Deciphering Pyroxasulfone Dynamics in Punjab Soils: Insights into Adsorption, Desorption, and Leaching Behavior

ABSTRACT Adsorption-desorption and leaching studies are crucial for understanding herbicide environmental fate and transport, enabling informed decisions regarding their application and risk of groundwater contamination. Batch equilibration technique was used to study the adsorption of pyroxasulfone. Data fitted well to Freundlich (R2 > 0.992) and Langmuir model (R2 > 0.994) suggesting that pyroxasulfone adsorption occurs on both homogeneous and heterogeneous soil sites, involving a combination of monolayer and multilayer adsorption. Adsorption was higher in clay loam soil followed by sandy loam and loamy sand. Thermodynamic parameters revealed that adsorption was spontaneous but became less favourable as temperature increased. Desorption data fitted well into the Freundlich model. A low hysteresis coefficient value indicated greater adsorption and slower desorption of pyroxasulfone. Irrespective of soil type and herbicide application rate, pyroxasulfone leached up to a depth of 0-30 cm and was below detectable limit (<0.01 µg mL-1) in leachates. Pyroxasulfone has highest leachability in loamy sand followed by sandy loam and clay loam. Low leaching potential of pyroxasulfone suggested a reduced groundwater contamination risk, but slow desorption and bound residues indicate soil persistence, potentially leading to phytotoxicity in subsequent crops. Long-term studies across diverse conditions are essential for effective risk management and environmentally sustainable agricultural practices. Adsorption-desorption and leaching studies are crucial for understanding herbicide environmental fate and transport, enabling informed decisions regarding their application and risk of groundwater contamination. Batch equilibration technique was used to study the adsorption of pyroxasulfone. Data fitted well to Freundlich (R2 > 0.992) and Langmuir model (R2 > 0.994) suggesting that pyroxasulfone adsorption occurs on both homogeneous and heterogeneous soil sites, involving a combination of monolayer and multilayer adsorption. Adsorption was higher in clay loam soil followed by sandy loam and loamy sand. Thermodynamic parameters revealed that adsorption was spontaneous but became less favourable as temperature increased. Desorption data fitted well into the Freundlich model. A low hysteresis coefficient value indicated greater adsorption and slower desorption of pyroxasulfone. Irrespective of soil type and herbicide application rate, pyroxasulfone leached up to a depth of 0-30 cm and was below detectable limit (<0.01 µg mL-1) in leachates. Pyroxasulfone has highest leachability in loamy sand followed by sandy loam and clay loam. Low leaching potential of pyroxasulfone suggested a reduced groundwater contamination risk, but slow desorption and bound residues indicate soil persistence, potentially leading to phytotoxicity in subsequent crops. Long-term studies across diverse conditions are essential for effective risk management and environmentally sustainable agricultural practices.

Investigation of adsorption parameters of saxitoxin onto loblolly pine-derived biochar synthesized at various pyrolysis temperature.

This study highlights the use of loblolly pine derived biochar for the removal of harmful algal bloom toxin, Saxitoxin (STX), from water. Biochar samples were prepared at varying pyrolysis temperatures (400, 600 and 800°C) for 60min. As pyrolysis temperature increases, enhancement in surface porosity was observed (SBET=7.26±0.2m2/g to 408.15±6.19m2/g) while a decline in oxygen-containing functional groups was observed (1517.80±14.98μmol/g to 823.01±7.72μmol/g). This study aimed to discover the effects of adsorption parameters such as biochar dosage amount, contact time, initial concentration and initial pH on Saxitoxin adsorption. These studies revealed impressive results with >90 % toxin removal with dosage rate of 0.01g/L, contact time of 30min, and increasing percent removal with increasing initial STX concentration and initial pH in water. Maximum uptake was calculated for P400 with adsorption capacity of 314.37μg/g. This showed that surface functionality showed higher affinity for STX uptake, which may be possible due to hydrogen bonding, electrostatic interactions, ion-exchange, and π-π interactions. Applied kinetic models indicated both physisorption and chemisorption interactions with best fit supporting the Elovich models. Complementary, adsorption isotherm analysis confirmed the multilayer adsorption behavior of the Freundlich model. Therefore, these findings support the viable use of biochar material for the remediation of STX waters.

Phenyl acetic acid modified biosilica from Cyclotella striata TBI diatom as an adsorbent for low molecular weight polycyclic aromatic hydrocarbons

ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) are persistent environmental contaminants with health risks due to bioaccumulation. This study explores phenyl acetic acid (PAA)-modified biosilica from Cyclotella striata as an adsorbent for low molecular weight (LMW) PAHs: phenanthrene, anthracene, and fluorene. Biosilica was isolated from C. striata biomass via acid soaking and calcination, then modified with PAA to enhance hydrophobicity and affinity towards PAHs by introducing aromatic groups, facilitating π-π interactions. Characterisation using FTIR, water contact angle (WCA), and BET surface area analysis confirmed successful modification. FTIR results confirmed the successful removal of organic residues and the presence of new functional groups post-modification. Post-modification, the WCA increased, reflecting a more hydrophobic surface. BET analysis showed a surface area decrease from 152.985 m2/g for unmodified biosilica to 86.039 m2/g post-modification. Adsorption experiments indicated qe values followed the following trend: anthracene > phenanthrene > fluorene. Kinetics studies revealed pseudo-second-order kinetics, reaching equilibrium within 80–120 minutes, with adsorption occurring in distinct phases. Adsorption isotherm studies of modified biosilica sorbents showed that the Freundlich model best described anthracene and phenanthrene adsorption, suggesting multilayer adsorption, while fluorene followed the Langmuir model, indicating monolayer adsorption. Adsorption thermodynamics of modified biosilica sorbents shows that adsorption of LMW PAHs is endothermic. After modification, the PAHs are less selective towards fluorene. These results demonstrate the potential of PAA-modified biosilica as an effective adsorbent for LMW PAHs.

One‐Walled Phthalimide Extended Calix[4]Pyrrole‐Based Supramolecular Adsorbent for Alleviating Nitrate From Simulated Water

AbstractIn this investigation, meso‐substituted one‐walled phthalimide appended calix[4]pyrrole (mPth–C4P) was prepared from pthalimide functionalized dipyrromethane (DPM, 4), acetone, and freshly distilled pyrrole via both conventional as well as green protocols utilizing the deep eutectic solvent (DES) of N,N'‐dimethyl urea (DMU) &amp; l‐(+)‐tartaric acid (TA) in an appropriate ratio of 7:3. In order to lessen the nitrate (NO3−) ion endowed eutrophication peril, the mPth–C4P was effectively employed as a supramolecular adsorbent for the sequestration of NO3− ion from aquatic phase. The mPth–C4P was extensively characterized by FTIR, 1H‐NMR, SEM–EDX, and elemental mapping to corroborate the synthesis and adsorption of NO3− ion. The surface area was found to be 11.465 m2 g−1 and the pore size of 3.2 nm, pointed out to the mesoporous nature of mPth–C4P. Batch methodology was exploited for detailing the influence of process parameters on %efficiency and adsorption capacity. The mPth–C4P demonstrated excellent adsorption competence (&gt; 91%) within 16 min from a [NO3−] of 20 mg L−1, which translates into a good pseudo‐second order rate constant value of 0.026 g mg−1 min−1. Freundlich model was the best‐fit model pointing out multilayer adsorption. The maximum saturation capacity was 239.03 mg g‒1 at 298 K, which is far better than most of the reported adsorbents indicating the potential of mPth–C4P to confiscate NO3−. The dynamics appraisal elucidated pseudo‐second order to favor the uptake with both intraparticle and liquid film diffusion models governing the rate of reaction. Thermodynamic parameters suggested that the uptake of NO3− was spontaneous, favorable, and exothermic which is in harmony with the isotherm studies. The mPth–C4P can be used consecutively up to 4 cycles along with good potential in real water &gt; 80% uptake. All these results established mPth–C4P as an efficacious scavenger for NO3− from simulated water.

Mechanisms of removing terdizolamide phosphate from water by the activation of potassium peroxymonosulfate with CeFe2O4 biochar.

Terdizolamide phosphate (TZD), a second-generation oxazolidinone antibiotic with a long half-cycle, poses a potential threat to ecosystems and humans if present in water over an extended duration. Magnetic biochar (CF-biochar) loaded with CeFe2O4 was firstly synthesized by microwave ablation-anaerobic carbonization using corn straw as raw material and Ce(NO3)3 and Fe(NO3)3 as modifiers. These modifiers were used as activators for peroxymonosulfate (PMS) and adsorbents for removing TZD. The maximum adsorption capacity of CF-biochar was up to 2869.44 mg g-1, which was much higher than that of modified biochar. The CF-biochar/PMS system achieved 99.72% removal of TZD and accelerated the removal rate with good results. Results from quenching and electron spin resonance (ESR) tests showed that and played a major role in the oxidative degradation of TZD. Besides, they had a good removal effect on TZD among other co-existing anions. CF-biochar exhibited a smaller particle size, larger specific surface area, more abundant pore size, and high magnetic nature. The removal kinetics and removal isotherms were modeled to show that the adsorption of TZD by CF-biochar was a spontaneous, exothermic, physical multilayer adsorption process. Main driving force corresponded to electrostatic attraction and hydrophobic properties. Therefore, the CF-biochar/PMS system was an efficient, promising, and sustainable technology for removing TZD.

Pharmaceuticals removal from aqueous solution by water hyacinth (Eichhornia crassipes): a comprehensive investigation of kinetics, equilibrium, and thermodynamics.

This study shows the efficiency of WH-C450, an adsorbent obtained from water hyacinth (WH) biomass, in the removal of sulfamethoxazole (SMX) from aqueous solutions. The process involves calcination of WH at 450°C to produce an optimal adsorbent material capable of removing up to 73% of SMX and maximum SMX adsorption capacity of 132.23mg/g. Fourier-transform infrared (FTIR) characterization reveals the involvement of various functional groups in the adsorption process through hydrogen bonds and electron-donor-acceptor (EDA) interactions. X-ray diffraction (XRD) analysis confirms the presence of phases containing CO32-, PO43- ions, as well as elements such as Si and Fe, which contribute to the adsorption mechanism through hydrogen bonding and complexation, respectively. X-ray photoelectron spectroscopy (XPS) analysis further supports these interactions. Kinetic analysis shows rapid adsorption, which combines physical and chemical processes and leads to rapid attainment of equilibrium. This is due to the high affinity of WH-C450 for SMX, which allows for a fast and efficient adsorption process. Isothermal modeling reveals multilayer adsorption with favorable interactions. Thermodynamic analysis confirms the endothermic and temperature-dependent nature of the process. In addition, pH, adsorbent dose, and initial concentration are important in adsorption. Lower pH levels enhance cationic SMX adsorption, while higher adsorbent doses improve efficiency. Optimal conditions were identified by experimental design, enabling the establishment of a predictive model. Consequently, the SMX removal capacity is strongly correlated with the initial concentration. This research underscores the potential of WH-C450 for antibiotic removal in water treatment applications.

A Novel Capacitor Deionization Performance Study Based on Carbon Nanorods/MnO2 Composite Material

The Earth abounds in water resources; however, only 0.4% of the freshwater resources are suitable for drinking. The scarcity of freshwater resources has a severe impact on the sustainable development of human society. Desalination is regarded as one of the most effective solutions. In this study, a research approach integrating materials and devices was utilized to synthesize manganese oxide-coated carbon nanospheres (CS@MnO2). Experimental results demonstrated that the system, by combining the distinctive performance merits of the CS@MnO2 material and the balanced desalination features, exhibited outstanding desalination performance. In the EDS elemental mapping analysis, the relatively feeble signal of carbon was ascribed to the encapsulation of MnO2 on the outer surface of CS. Through computational TGA analysis, the mass fraction of carbon in CS@MnO2-2 was determined to be approximately 51.2%. The excellent hydrophilicity of the material facilitated the permeation of the salt solution throughout the electrode, thereby enhancing the capacitance. CS@MnO2-2 manifested a high salt adsorption capacity of 27.42 mg g⁻¹ and the fastest electrosorption rate of 7.81 mg g⁻¹ min⁻¹. During 50 adsorption desorption cycles, the adsorption capacity showed good results. The adsorption kinetics and adsorption isotherm fitting indicated that the desalination process involved electrostatic and multilayer adsorption. This study holds great significance for reducing the cost of desalinated water and guaranteeing a sustainable supply of freshwater resources.

Novel enhancement strategy for Hg adsorption in wastewater: Nonthermal plasma-mediated advanced modification of zero-valent iron-carbon galvanic cells with thiol functionalization.

Mercury (Hg) pollution poses a critical threat to human health and the environment, necessitating urgent control measures. This study introduces a novel modification method for the common zero-valent iron-carbon (ZVI-AC) galvanic cells using a two-step process, nonthermal (NTP) irradiation followed by targeted functionalization, aiming to enhance Hg adsorption potential by adjusting the physicochemical properties of the cells. The NTP irradiated functionalized adsorbent demonstrated superior Hg adsorption performance across various concentrations and pH variations. Multichannel adsorption mechanisms were confirmed by fitting a total of 22 different adsorption isotherm models, indicating the coexistence of monolayer and multilayer adsorption processes. The NTP irradiation modifies the ZVI and AC, inducing nitrogen and oxygen doping on carbon-based surfaces and oxidizing ZVI to Fe(II)-Fe(III) species. The deepened oxidation of Fe in NTP-Fe-C, coupled with Hg2+ reduction to elemental Hg by raw Fe, contributed to Hg removal. NTP irradiation facilitated electron transfer between Fe and Hg, promoting oxidation of Fe and reduction of Hg2+ cations. The emergence of diverse Hg species further supported the multichannel adsorption/removal mechanism achieved by NTP-irradiated cells. This method offers a promising solution to Hg pollution and expands the application of the traditional iron-carbon galvanic cells in treating hazardous heavy metal wastes.

Mechanistic Insights into the Eco-Friendly Conifer Cone Extract's Corrosion Inhibition on Steel Rebar and Cement Mortar: An Experimental and Simulation Approach.

This study investigates the corrosion inhibition effects of eco-friendly conifer cone extract (CCE) on steel rebars embedded in cement mortar exposed to 3.5% NaCl under alternate wet/dry cycles. CCE concentrations of 0, 0.5, 1.0, 1.5, and 2.0% (denoted CCM0 to CCM4) were tested. Electrochemical and weight loss analyses revealed that 0.5% CCE significantly enhanced corrosion resistance, achieving 84.8% inhibition efficiency via polarization methods and a reduced corrosion rate of 9.46 mmpy. Chloride-binding studies indicated that 0.5% CCE improved adsorption intensity and multilayer adsorption constants compared to those of the control, as confirmed by Freundlich and Harkins-Jura isotherms. Surface analyses using SEM/EDS and AFM demonstrated the formation of a dense, protective passive layer on steel rebar surfaces, effectively reducing the surface roughness to 41.05 nm in CCM1 specimens. Theoretical simulations using SCC-DFTB and molecular dynamics showed a strong interaction between CCE functional groups and the iron surface, supporting experimental findings. Mechanical and porosity evaluations confirmed that 0.5% CCE maintained compressive strength and permeability while improving corrosion resistance. These results position CCE as a cost-effective, eco-friendly inhibitor with potential applications in protecting reinforced concrete structures in chloride-rich environments.

Integrating Zeolitic Imidazolate Framework-8 with DES-Treated Loofah Sponge for Enhanced Toluene Adsorption.

The pervasive presence of toluene in aquatic environments, primarily due to oil spills and industrial effluents, necessitates the development of effective and sustainable remediation strategies. This study introduces ZIF-8@DES-treated loofah sponge (ZIF-8@DLS), a novel adsorbent composite material, synthesized via an in situ process that integrates the high surface area of ZIF-8 with the natural loofah sponge. The composite was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR), confirming the successful loading of ZIF-8 onto the loofah substrate. The adsorption capacity of ZIF-8@DLS for toluene was evaluated, achieving a maximum of 145.3 mg/g with an efficiency of 72% under standard conditions. Kinetic studies revealed that the adsorption process predominantly followed a pseudo-second-order model, indicative of chemisorption. The adsorption isotherm data were found to align more closely with the Freundlich model, suggesting a multilayer adsorption mechanism on the composite's heterogeneous surface. The ZIF-8@DLS composite demonstrates a promising synergy of high adsorption performance, cost-effectiveness, facile synthesis, and environmental benignity, positioning it as a candidate for practical applications in wastewater treatment and adsorptive separation processes.

Transformation fate of bisphenol A in aerobic denitrifying cultures and its coercive mechanism on the nitrogen transformation pathway.

Bisphenol A (BPA) is a commonly used endocrine-disrupting chemical found in high levels in wastewater worldwide. Aerobic denitrification is a promising alternative to conventional nitrogen removal processes. However, the effects of BPA on this novel nitrogen removal process have rarely been reported. Herein, we investigated the removal and interaction effects of BPA (0, 0.1, 1, and 10 mg/L) in aerobic denitrifying cultures. Our experimental results demonstrated that the aerobic denitrification system could remove 66%-86% of BPA from wastewater. Fourier transform infrared spectroscopy revealed that polysaccharides and amides were the primary sites for adsorption. An increase in the type and number of intermolecular hydrogen bonds might enhance the ability of aerobic denitrifying cultures to adsorb BPA. Adsorption kinetics analysis demonstrated that inhomogeneous multilayer adsorption was the leading cause of BPA removal. Adsorbed BPA decreased the sedimentation, flocculation, and hydrophobicity of aerobic denitrifying cultures, triggering changes in the levels of proteins and polysaccharides in extracellular polymeric substances. As the influent BPA increased from 0 to 10 mg/L, the nitrate-nitrogen and total organic carbon in the reactor effluent increased from 0.4 ± 0.2 and 26 ± 7.9 mg/L to 18.8 ± 9.3 and 116.2 ± 55.6 mg/L, respectively. BPA (initial concentration range: 1-10 mg/L) significantly influenced the abundance of genes involved in the nitrogen transformation pathway, contributing to the increase in the abundance of gaseous NOx-transformed genes and altering the relative abundance of denitrifying bacteria, particularly Thauera. Correlation analyses revealed that Pseudomonas, Thauera, and AKYH767 are important for maintaining systemic nitrogen transformations and BPA adsorption.

Performance, isotherm, kinetics and mechanism of simultaneous removal of Cr(VI), Cu(II) and F ions by CeO2–MgO binary oxide nanomaterials

This study focuses on the synthesis of a novel Cerium-Magnesium (CeO2-MgO) binary oxide nanomaterials by a simple co-precipitation process and used to remove harmful pollutants such as Cr(VI), Cu(II), and F. The morphology, phase, crystallite size, thermal stability, functional groups, surface area, and porosity of the synthesized nanomaterial were determined by using XRD, SEM, FTIR, TGA/DTA, and BET studies. The prepared nanomaterials showed adsorption selectivity of Cu(II) ≈ F−> Cr(VI) with a high adsorption capacity of 84.3 − 133.3 mg/g for Cu(II), Cr(VI), and F−. The distribution coefficient (Kd) for F− and Cu(II) was found to be in the range of 104 mL/g which was adequate. The adsorption isotherms for Cr(VI), Cu(II), and F− followed the Freundlich isotherm model and the pseudo-second-order kinetic model in linear and nonlinear forms, indicated multilayer adsorption. Maximum removal of Cr(VI), Cu(II), and F− ions was found to be 92.84%, 98.88%, and 95%, respectively, for a high initial concentration of 50 mg/l by 2 g/l dosages of prepared CeO2-MgO binary oxide nanomaterials employed as an adsorbent in this study. The results showed that novel CeO2-MgO binary oxide nanomaterials are promising adsorbent for removing hazardous inorganic contaminants from the water due to their adsorption capability and chemical stability.

Kinetic multilayer models for surface chemistry in indoor environments.

Multiphase interactions and chemical reactions at indoor surfaces are of particular importance due to their impact on air quality in indoor environments with high surface to volume ratios. Kinetic multilayer models are a powerful tool to simulate various gas-surface interactions including partitioning, diffusion and multiphase chemistry of indoor compounds by treating mass transport and chemical reactions in a number of model layers in the gas and condensed phases with a flux-based approach. We have developed a series of kinetic multilayer models that have been applied to describe multiphase chemistry and interactions indoors. They include the K2-SURF model treating the reversible adsorption of volatile organic compounds on surfaces, the KM-BL model treating diffusion through an indoor surface boundary layer, the KM-FILM model treating organic film formation by multi-layer adsorption and film growth by absorption of indoor compounds, and the KM-SUB-Skin-Clothing model treating reactions of ozone with skin lipids in skin and clothing. We also developed the effective mass accommodation coefficient that can treat surface partitioning by effectively taking into account kinetic limitations of bulk diffusion. In this study we provide detailed instructions and code annotations of these models for the model user. Example sensitivity simulations that investigate the impact of input parameters are presented to help with familiarization to the codes. The user can adapt the codes as required to model experimental and indoor field campaign measurements, can use the codes to gain insights into important reactions and processes, and can extrapolate to new conditions that may not be accessible by measurements.

Transport mechanisms of the anthropogenic contaminant sulfamethoxazole in volcanic ash soils at equilibrium pH evaluated using the HYDRUS-1D model.

The volcanic soils in Chile, where a significant portion of agricultural activities take place, are impacted by the presence of veterinary drugs, including sulfamethoxazole (SMX). The study examines how different soil types influence the movement and retention of sulfamethoxazole (SMX) across four regions of Chile, focusing on conditions at a neutral pH of 7.0. Collipulli's Ultisol soils (CLL), characterized by high clay and sand content but low organic matter (OM), promote low SMX adsorption and rapid transport. In contrast, the volcanic ash-derived Andisols from Frutillar (FRU), Nueva Braunau (NBR), and Osorno (OSR) have high OM and cation exchange capacity (CEC), which enhance their ability to retain SMX and reduce its mobility. Adsorption batch, kinetics, and column breakthrough curve (BTC) experiments were conducted alongside transport modelling. The adsorption kinetics of SMX in CLL soil followed a pseudo-first-order (PFO) model, while FRU, NBR, and OSR soils aligned with a pseudo-second-order (PSO) model. Freundlich isotherms effectively described SMX adsorption in CLL and OSR soils, indicating multilayer adsorption, while Langmuir isotherms fit the FRU and NBR soils, suggesting monolayer adsorption. Using HYDRUS-1D software, we simulated SMX transport in soil columns. BTCs were best modelled using a two-site sorption model with both equilibrium and kinetic adsorption. SMX was more mobile in CLL soil due to its lower organic matter (OM) content and adsorption capacity. In contrast, FRU, NBR, and OSR soils showed slower transport, reflecting higher OM content and greater adsorption capacity, reducing SMX leaching. These findings emphasize the importance of soil properties, such as OM content, in influencing SMX behavior, and are vital for assessing environmental impacts and developing mitigation strategies.

A "cyclodextrin-salicylic acid-chitosan" bifunctional monomer magnetic hydrophilic imprinted sandwich gel for targeted adsorption and slow release of ginkgolic acid.

This study aims to address the challenge of detoxifying ginkgolic acid and transform it from waste into a valuable resource. By using pseudo-template molecular imprinting technology to chemically modify polysaccharide materials, we developed a polysaccharide-based molecular imprinted material (MMCC-CD/CS-MIP) for the targeted separation and controlled release of ginkgolic acid. Under optimal conditions, MMCC-CD/CS-MIP demonstrated excellent adsorption performance (Qmax=47.786mgg-1) and desorption performance (QD=42.33mgg-1), with a desorption rate of 88.58%. In addition, the material exhibited outstanding selectivity, stability, recyclability, antibacterial activity, and sustained-release properties, with a cumulative release rate of 95.57% over 72h. The release data followed the Korsmeyer-Peppas model, while the adsorption behavior fit a multi-layer heterogeneous adsorption model (Freundlich model) and conformed to a second-order kinetic model. Thermodynamic analysis confirmed that the adsorption of ginkgolic acid by MMCC-CD/CS-MIP is both feasible and spontaneous. MMCC-CD/CS-MIP provides a promising solution for the detoxification of medicinal components.

The adsorption behavior and mechanism of Cu(Ⅱ), Fe(Ⅱ) and Co(Ⅱ) on straw biochar and their Fenton-like performance for ciprofloxacin decontamination.

In this study, the adsorption of aqueous Cu(Ⅱ), Fe(Ⅱ), and Co(Ⅱ) on biochars at diverse synthesized temperatures was evaluated. The optimal sample BC-800 achieved superior adsorption performance of Cu(Ⅱ), Fe(Ⅱ), and Co(Ⅱ) at 10-50mgL-1 initial concentration. Due to the larger surface area (349.6m2/g), total pore volume (0.24cm3/g), average pore diameter (6.4nm), higher degree of graphitization (IG/ID=1.00) and stable aromatic carbon structure, BC-800 achieved excellent adsorption of Cu(Ⅱ), Fe(Ⅱ), and Co(Ⅱ) through multilayer chemical adsorption, corresponding to the pseudo-2nd-order and Freundlich model (Qm Cu(Ⅱ)=433.4mgg-1, Qm Fe(Ⅱ)=472.0mgg-1 and Qm Co(Ⅱ)=301.0mgg-1). After then, the adsorbed biochars with Cu(Ⅱ), Fe(Ⅱ), and Co(Ⅱ) were directly used as heterogeneous catalysts in Fenton-like reaction for ciprofloxacin (CIP) degradation. Compared with Co-BC-800/peroxymonosulfate (PMS) system, Co-BC-800/H2O2 system exhibited the 56.6% decontamination of CIP with lower ions leaching (0.53mg/L) within 70min. The 97.9% of CIP was finally removed by Co-BC-800/H2O2 under optimized conditions: initial pH=6.94, catalyst dosage=1.0gL-1, H2O2 concentration=0.44gL-1. Furthermore, Co-BC-800 exhibited superior acid-base adaptability (2.94-10.94) and anti-anion interference ability. The removal of CIP was achieved by the synergistic effect of adsorption and oxidative degradation. This study proposes some insights into the behavior and mechanism of metal ions adsorption on biochar and hazardous waste treatment.

Study on the adsorption performance of carbon-magnetic modified sepiolite nanocomposite for Sb(V), Cd(II), Pb(II), and Zn(II): Optimal conditions, mechanisms, and practical applications in mining areas.

A carbon-magnetic modified sepiolite nanocomposite (γ-Fe2O3/SiO2-Mg(OH)2@BC) was synthesized using a hydrothermal method, consisting of γ-Fe2O3, activated sludge biochar (BC), and alkali-modified sepiolite. Its ability to remove heavy metals such as Sb(V), Pb(II), Cd(II), and Zn(II) was investigated through adsorption experiments. Using response surface optimization, the optimal adsorption conditions were determined: adsorption time = 3.78 h, pH = 2.63, initial concentration = 15.78 mg/L, temperature = 35.14°C, and adsorbent dosage = 100.71 mg. Characterization results revealed that the main adsorption mechanisms included complexation, π-π interactions, and electrostatic attraction. Kinetic and isotherm model analyses indicated that the adsorption process of γ-Fe2O3/SiO2-Mg(OH)2@BC adhered to the pseudo-second-order kinetic model and the Freundlich isotherm model, primarily involving multilayer chemical adsorption. The application of this composite material in complex aquatic environments in antimony mining areas demonstrated promising practical results, as well as excellent regeneration performance. This study provides technical and theoretical support for the treatment of complex heavy metal wastewater in antimony mining areas and lays a foundation for the development of novel carbon-magnetic modified nanocomposite adsorbents.

A novel biochar adsorbent for treatment of perfluorooctanoic acid (PFOA) contaminated water: Exploring batch and dynamic adsorption behavior

Perfluoroalkyl substances (PFAS), like perfluorooctanoic acid (PFOA), are of concern worldwide given they are ubiquitous in the environment. In this study, the treatment of PFOA-contaminated water was assessed using biochar adsorbents produced from raw canola straw (RCS) through chemical activation with H3PO4 and ZnCl2 and microwave-assisted pyrolysis (MWP). MWP conditions were evaluated to create optimal H3PO4-treated (PBC) and ZnCl2-treated (ZnBC) biochar adsorbents with treatments determined using a central composite design (CCD) based on the response surface methodology (RSM) considering activator concentration, and microwave heating time and power. The highest PFOA removal efficiency for PBC (3.0 mol/L) was achieved at 92 % (368 μg/g), while for ZnBC (0.55 mol/L) it was 84 % (336 μg/g). In contrast, untreated biochar and RCS had markedly lower PFOA removals of 5 % and 1 %, respectively. Activation of biochar under optimal pyrolysis conditions (6 min at 600 W) led to increased chemical functional groups, porosity, and surface area, as confirmed by FT-IR, XPS, and BET. The kinetic study indicated that chemisorption was the primary PFOA adsorption mechanism, while the Freundlich isotherm model suggested heterogeneous multilayer adsorption for PFOA removal. Further, background salts enhanced PFOA adsorption through divalent bridges and salting-out mechanisms. PBC and ZnBC adsorbents performed well over a broad pH range of 3 to 9. Lastly, Yan and Yoon-Nelson models were used to assess adsorption breakthrough for a model fixed-bed adsorption system. This study exhibits that PBC and ZnBC adsorbents, derived from accessible biomass, offer an environmentally friendly solution to remove PFOA from contaminated water.

Competitive Adsorption Studies of Cd(II) and As(III) by Poly (Butylene Succinate) Microplastics: Based on Experimental and Theoretical Calculation

Microplastics (MPs) can serve as vectors for heavy metals in aquatic environments; however, the adsorption behavior of MPs on multiple heavy metal systems is still unclear. This study investigated the adsorption characteristics of biodegradable poly (butylene succinate) (PBS) for cadmium (Cd(II)) and arsenic (As(III)) in both single and binary systems. Adsorption isotherms were studied using the Linear, Langmuir, and Freundlich models, and further analysis of MPs adsorption characteristics was conducted using site energy distribution theory and density functional theory. The results indicate that the maximum adsorption capacities of PBS for Cd(II) and As(III) are 2.997 mg/g and 2.606 mg/g, respectively, with the Freundlich model providing the best fit, suggesting multilayer adsorption on heterogeneous sites. As(III) has a higher adsorption affinity for PBS than Cd(II), with a binding energy of −11.219 kcal/mol. Additionally, the adsorption mechanisms of Cd(II) and As(III) on PBS include electrostatic interactions and surface complexation, with the primary adsorption sites at the C=O of the carboxyl group and the hydroxyl group. The comprehension of interfacial interactions between biodegradable plastics and heavy metals is facilitated by a combination of theoretical calculations and experimental investigations.

Study on Enhancing Adsorption Efficiency in Best Available Techniques for Arsenic Reduction in Water

The Integrated Environmental Management System promotes the treatment of emissions, wastewater, and waste using Best Available Techniques (BAT), accounting for environmental, economic, and technical factors. Heavy metals in wastewater, including arsenic, a highly toxic and carcinogenic substance, have raised significant global water quality concerns. Adsorption technology for arsenic removal is favored due to low installation and operational costs and its stability across water quality variations. While magnesium oxide-based adsorbents are actively researched, conventional methods often require surfactants, making large-scale production costly. This study developed a porous, layered magnesium oxide adsorbent by calcining a precursor of magnesium ions and ethylene glycol. The adsorbent showed strong affinity for pentavalent arsenic ions, and structural and adsorption mechanisms were analyzed. SEM analysis revealed surface characteristics, and BET analysis showed a specific surface area of 34.98 m²/g. Kinetic experiments (0-12 hours) applied pseudo-first and pseudo-second-order models, and adsorption isotherms, tested for initial concentrations of 10-1000 mg/L, were fitted to Langmuir and Freundlich models with a q&lt;sub&gt;max&lt;/sub&gt; of 817.8 mg/g. Results indicated that the pseudo-second-order (R²=0.881) and Freundlich models (R²=0.968) best fit the data, suggesting physical, multilayer adsorption. Higher initial pH improved performance, and FT-IR and XPS analysis compared the adsorbent before and after adsorption.