Intraparticle Diffusion Research Articles

Development of a limestone-based ballasted material for enhanced co-removal of turbidity and fluoride from coal mine water: An efficacy study

The rapid progression of coal mining technology in recent years has resulted to the discharge of mine water with excessively high levels of turbidity and fluoride, presenting a complex contamination issue. This study develop an innovative limestone-based ballasted material, integrating it with ballasted flocculation technology. The synergistic effects of surface flocculation and adsorption have enabled the simultaneous and efficient removal of high concentrations of turbidity and fluoride. The influence of various parameters, including the dosage of the coagulant, flocculant, ballasted material, and the stability under long-term continuous operation, on the performance of this new technology was investigated. Findings indicate that an increase in the dosage of the coagulant, polyaluminum chloride (PAC), positively affects the removal of turbidity and fluoride ions, with an optimal dosage of 60 mg/L. The addition of polyacrylamide (PAM) showed that both conventional and ballasted coagulation techniques exhibit an initial increase followed by a decrease in turbidity removal efficiency, and an ascending trend in fluoride removal efficiency, with an optimal PAM dosage of 1.0 mg/L. The dosage of the new ballasted material was determined based on the initial water turbidity and fluoride concentrations, an increase in its dosage led to a progressive reduction in effluent turbidity and a corresponding increase in fluoride removal. A 30-day continuous operation confirmed the stability of the new process, with a treatment cost of approximately 2.67 $/t. The pseudo-first-order kinetic model and the Langmuir adsorption isotherm equation provided satisfactory fits to the treatment data, suggesting that both conventional and ballasted coagulation involve a combination of surface adsorption and intraparticle diffusion mechanisms for the removal of turbidity and fluoride.

Deep Cleaning of Crystal Violet and Methylene Blue Dyes from Aqueous Solution by Dextran-Based Cryogel Adsorbents.

Polysaccharides have recently attracted growing attention as adsorbents for various pollutants, since they can be extracted from a variety of renewable sources at low cost. An interesting hydrophilic and biodegradable polysaccharide is dextran (Dx), which is well-known for its applications in the food industry and in medicine. To extend the application range of this biopolymer, in this study, we investigated the removal of crystal violet (CV) and methylene blue (MB) dyes from an aqueous solution by Dx-based cryogels using the batch technique. The cryogel adsorbents, consisting of cross-linked Dx embedding a polyphenolic (PF) extract of spruce bark, were prepared by the freeze-thawing approach. It was shown that the incorporation of PF into the Dx-based matrix induced a decrease in porosity, pore sizes and swelling ratio values. Moreover, the average pore sizes of the DxPF cryogels loaded with dyes further decreased from 42.30 ± 7.96 μm to 23.68 ± 2.69 μm, indicating a strong interaction between the functional groups of the cryogel matrix and those of the dye molecules. The sorption performances of the DxPF adsorbents were evaluated in comparison to those of the Dx cryogels and of the PF extract. The experimental sorption capacities of the DxPF cryogel adsorbents were higher in comparison to those of the Dx cryogels and the PF extract. The DxPF cryogels, particularly those with the highest PF contents (sample DxPF2), demonstrated sorption capacities of 1.2779 ± 0.0703 mmol·g-1, for CV, and 0.3238 ± 0.0121 mmol·g-1, for MB. The sorption mechanisms were analyzed using mathematical models, including Langmuir, Freundlich, Sips and Dubinin-Radushkevich isotherms, and kinetic models, like pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich and intra-particle diffusion (IPD). The sorption process was best described by the Sips isotherm and PSO kinetic models, indicating chemisorption as the dominant mechanism. This study outlines the importance of developing advanced renewable materials for environmental applications.

High-quality mesoporous adsorbent derived from pomegranate pomace for efficient removal of azo dye from textile wastewater: Influencing factors, reusability, and mechanism studies

The solid waste from the processing of pomegranate (Punica granatum L.) juice, known as pomegranate pomace, was utilized as an economical and readily available precursor to produce high-quality activated carbon (AC). The AC was synthesized using a low-cost method at a carbonization temperature of 600 °C, employing a 1:1 impregnation ratio (precursor/H3PO4), and activating for 1 h. Various characterization techniques, including SEM imaging, XRD analysis, FT-IR analysis, BET surface area analysis with pore size determination, and other physicochemical assessments, were conducted on the produced AC. To assess its efficacy in treating textile wastewater, Basic Yellow 28 (BY 28) dye was selected as a representative pollutant. The results displayed a mesoporous structure in the produced AC with a mesopore content of 78.82 %. Notably, it exhibited a high BET surface area of 1089.08 m2/g and a total pore volume of 1 cm3/g. The Langmuir non-linear isotherm model emerged as the most fitting for explaining the adsorption equilibrium data, revealing a substantial monolayer adsorption capacity of 659.13 mg/g at 20 °C. The experimental data fit into a pseudo-second-order kinetic model, where the rate-determining step was found to be intra-particle diffusion. Thermodynamic analysis revealed that the adsorption of BY 28 dye onto the produced AC was an exothermic process. The produced AC exhibited high stability, as demonstrated in desorption studies, maintaining effectiveness through multiple uses. These results signify the potential of using pomegranate pomace, an environmentally problematic waste, as a novel precursor for producing sustainable and cost-effective AC.

Understanding retention and intra-particle diffusivity of alkylsulfobetaine-bonded Ethylene Bridged Particles with different mesopore sizes for hydrophilic interaction liquid chromatography applications

The role of the average pore diameter (APD) of 1.7μm AtlantisTM Premier BEHTM Particles derivatized with a zwitterionic group (propylsulfobetaine) on the efficiency of their 2.1 × 50 mm hydrophilic interaction liquid chromatography (HILIC) packed columns is investigated experimentally. Van Deemter plots for toluene (neutral, hydrophobic), cytosine (neutral, polar), tosylate (negatively charged), bretylium and atenolol (positively charged) were measured on three HILIC columns packed with BEH Z-HILIC Particles having APDs of 95 Å, 130 Å, and 300 Å. The intraparticle diffusivities of the analytes across these three BEH Z-HILIC Particles were measured by the peak parking method.The experimental data reveal that the slope of the C-branch of the van Deemter plots can be reduced by factors of about 15 for toluene, 2.5 for cytosine, 6 for atenolol, 5 for tosylate, and 14 for bretylium with increasing the APD from 95 Å to 300 Å. This observation is explained by: (1) the reduced amount of the highly viscous water diffuse layer and subsequent increase of the amount of acetonitrile-rich eluent in the mesopores, (2) the localized electrostatic adsorption of the retained analytes onto the zwitterion-bonded BEH Particles, and (3) depletion/excess of the analytes into the water diffuse layer. A general model of intraparticle diffusivity was then proposed to account for the impact of the APD of Z-HILIC Particles on the solid-to-liquid mass transfer resistance of small molecules. The model highlights the relevance of the thickness of the water diffuse layer, the access of the bulk eluent into the mesopore, the localized electrostatic adsorption, and the partitioning constant of the retained analyte between the bulk eluent and the water diffuse layer.

Biochar Microparticles from Pomegranate Peel Waste: Literature Review and Experiments in Isotherm Adsorption of Ammonia

This research aimed to synthesize biochar microparticles from pomegranate peel waste for ammonia adsorption. This research also focused on analyzing adsorption isotherm and kinetics models to understand the mechanism of ammonia adsorption on the biochar. The experiments were conducted by carbonizing pomegranate peel waste. The carbonized material was then milled and sieved to obtain biochar microparticles with a certain size (i.e. 500, 1000, and 2000 μm). The particles were then characterized using microscopy and infrared spectroscopy (FTIR) to identify particle morphology and functional groups. The prepared particles were then used for the ammonium adsorption process, and compared with ten isotherm models (such as Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Jovanovic, Halsey, Harkin-Jura, Flory-Huggins, Fowler-Guggenheim, and Hill-Deboer) to identify the adsorption mechanism. Adsorption kinetic analysis was also performed to identify the adsorption rate of the prepared particles using first-order and second-order pseudo-kinetic models. The adsorption isotherm model informed that ammonia adsorption on biochar with sizes of 2000 μm (large) and 1000 μm (medium) occurs in a multilayer process with physical interaction accompanied by pore filling. Meanwhile, small biochar (500 μm) indicates that the ammonia adsorption process occurs on homogeneous sites with physical interaction through pore filling. From the results of fitting the isotherm model, information about the maximum adsorption capacity for each size of 2000, 1000, and 500 μm are 65.631, 62.231, and 50.086 mg/g, respectively. Overall, the adsorption mechanism occurring on biochar involves interactions among ammonia molecules that repel each other under endothermic conditions. The largest adsorption capacity was obtained for biochar with sizes of 2000 μm. Analysis of adsorption kinetics showed that the adsorption process follows a first-order pseudo-kinetic model, indicating an adsorption mechanism controlled by intraparticle diffusion. This study concludes that biochar from pomegranate peel is prospective for use as an environmentally friendly adsorbent for ammonia removal applications from wastewater, offering a sustainable and effective alternative adsorbent to existing water treatment technologies and solving current issues in the sustainable development goals (SDGs).

Study of heavy metals adsorption using a silicate-based material: Experiments and theoretical insights

Heavy metal toxicity in water is a serious problem with harmful effects on human health and the ecosystem. This research studied a silicate-based material as an adsorbent for removing four heavy metals from aqueous solutions. The target metal pollutants selected include manganese (Mn2+), copper (Cu2+), cobalt (Co2+), and zinc (Zn2+). First, theoretical tools including potential energy surface analysis, Natural Population Analysis, AIM, Wiberg Bond Index, QTAIM, and topological methods offer profound insights into the nature of interactions present in the Mg2O8Si3M (M = Mn2+, Cu2+, Co2+, Zn2+) clusters. Second, the synthesis and characterization of eco-friendly hydrated amorphous magnesium silicate (MgOSiO2nH2O) was developed. Last, a simple kinetic adsorption test was applied to assess the material selectivity towards heavy metals and support theoretical results. The kinetic adsorption study was analyzed through the pseudo-first and second-order kinetics, Elovich, and the intraparticle diffusion models. The theoretical analysis of the adsorption energies indicates that the adsorption of four metal ions on the Mg2O8Si3 surface is energetically favorable in all cases. The material displayed the following adsorption sequence: Cu2+ (59 mg g-1) > Zn2+(25 mg g-1) ≈ Co2+ (23 mg g-1) > Mn2+ (15 mg g-1). This knowledge can then be used to design and optimize low-cost silicate-based materials for effective heavy metal removal, contributing to efforts to address environmental pollution and protect public health.

Comparative kinetic study of Pb(II) and Cd(II) metal ions removal from aqueous solutions by Lactobacillus helveticus, Limosilactobacillus fermentum, and Lactiplantibacillus pentosus

ABSTRACT In this study, selected lactic acid bacteria, including Lactobacillus helveticus, Limosilactobacillus fermentum, and Lactiplantibacillus pentosus, were evaluated for their potential to remove Pb(II) and Cd(II) ions from aqueous solutions. The highest removal efficiency was achieved at a pH value of 4. Kinetic modeling using the pseudo-first-order, pseudo-second-order, and intraparticle diffusion models demonstrated that the intraparticle diffusion model provided the best fit for describing the adsorption process. The results of the study indicated that among the three bacteria tested, L. fermentum exhibited the highest maximum adsorption capacity for Pb(II) at 4.95 mg g−1, followed by L. helveticus at 4.91 mg g−1 and L. pentosus at 4.08 mg g−1. In contrast, for Cd(II) adsorption, L. helveticus showed the highest maximum adsorption capacity at 4.38 mg g−1, followed by L. pentosus at 3.45 mg g−1 and L. fermentum at 2.86 mg g−1. The mechanism of Pb(II) and Cd(II) ions removal by LAB strains involves adsorption onto the bacterial cell surfaces, where interactions such as ion exchange, electrostatic attraction, and complexation play crucial roles. Overall, L. helveticus, L. fermentum, and L. pentosus hold promising potential for various applications in wastewater treatment, particularly in the removal of heavy metal ions.

Experimental study on the preparation of desulfurizer for low temperature dry desulfurization by digesting CaO in urea solution

Calcium hydroxide (Ca(OH)2) with outstanding sulfur dioxide (SO2) adsorption properties was synthesized through the utilization of calcium oxide (CaO) with a urea solution via a digestion method. This innovative calcium-based desulfurizer aims to meet the needs of low-temperature dry flue gas desulfurization in the steel industry. Fixed-bed experiments were conducted to investigate the impact of different water-ash ratios, urea solution concentrations, and digestion time on the desulfurization efficiency and particle structure of the desulfurizers. Sample CAC-2–0.1 U exhibited outstanding desulfurization performance, achieving 100 % removal efficiency, a sulfur capacity of 34.64 mg/g, and a breakthrough time of 142.6 minutes under target flue gas conditions. The sample also displayed a high specific surface area of 22.10 m2/g and demonstrated adaptability under varying operating conditions. Characterization and reaction mechanisms of the desulfurizer were studied using XRD, SEM, BET, XPS, ICP-OES, and Materials Studio software. Experimental data was analyzed through pseudo-first-order and pseudo-second-order kinetic equations, and intra-particle diffusion model. The product's strong adsorption capacity for SO2 positions it as a highly promising adsorbent for controlling low-temperature flue gas emissions in the steel industry.

Development of a mayenite composite pellet towards salinity remediation: Experimental demonstration of passive chloride removal from saline oilfield groundwater

This study investigates newly developed sand/gravel-sized mayenite composite pellets with cellulose-based binders as a chloride (Cl−) remover that is compatible with saline groundwater also impacted by hydrocarbons. The mayenite pellets remove Cl− from impacted oilfield groundwater with 60–90 % efficiency in the range of salinity values found at field sites (< 20,000 mg/L total dissolved solids, TDS) in the presence of hydrocarbons, without agitation. The pellet reactions are driven by hydration, anion exchange, adsorption, and mineral phase reconstruction with increasing intraparticle diffusion and pellet heterogeneity during Cl− removal. Cl− removal is significantly correlated with changes in the quantities of pellet components. Mayenite is a key mineral for Cl− removal, during which hydrocalumite is formed. However, high mayenite purity is not required due to the contributions of non-mayenite pellet components (CaO and Al2O3) to Cl− removal. Drastic morphological transformations of pellet minerals occurred from honeycomb-like to cubic or hexagonal structures. Sand/gravel-sized pellets had a comparable Langmuir qmax of 74.5 mg/g. Mayenite pellets are not affected by hydrocarbons in both aqueous and nonaqueous phases. The removal of hydrocarbons observed was likely associated with porous pellet structures. TDS and competitive anions in impacted groundwater regulate the mayenite pellet reactions for Cl− removal.

Investigation on the adsorption mechanism of a mixture of seven pharmaceutical compounds on virgin and aged biodegradable microplastics

In this study the adsorption of a mixture of seven pharmaceutical compounds on virgin and aged polylactic acid (PLA) microplastics (MPs) was investigated. PLA MPs were aged under UV radiation and simulated solar light (SSL) creating three types of MPs: i) virgin, ii) UV-aged and iii) SSL-aged PLA-MPs. The different PLA-MPs were characterized with various characterization techniques (FTIR, SEM, TGA) which revealed modifications on the surface of the aged MPs like cracks and pits, creating more adsorption sites. Pseudo-first, pseudo-second and the intraparticle diffusion model were applied to explore the mechanism and the rate limiting step of the adsorption mechanism. Isothermal study was also conducted and revealed better fitting with the Freundlich model indicating a multi-layer coverage on the MPs surface. Aging appears to enhance the adsorption capacity of the target compounds on the PLA-MPs for both types of aged MPs however the UV-aged showed higher uptake. Finally, the effect of other parameters, like the pH or the type of the water matrix were also investigated offering a deeper insight on the adsorption mechanism of the target compounds.

Adsorption studies of methylene blue on cation-modified graphene oxide and graphene oxide/MXene membranes

Membranes prepared from graphene oxide (GO) have greater advantages over traditional materials for water treatment, while MXene is a good candidate for pollutant removal. However, the effect of different cations introduced into the prepared GO membranes on their adsorption performance must be further explored. In this study, a series of cation-modified GO and GO/MXene membranes were prepared based on the self-assembly of GO. Na+-modified membranes were found to be more effective at removing methylene blue (MB) than multivalent cation-modified GO membranes. However, the cation-modified GO/MXene membranes improved the MB adsorption efficiency, and the higher the ionic valence, the more pronounced the effect. In addition, the effects of the pH, temperature, contact time and initial concentration of MB on the adsorption performance of the membranes were investigated. The best removal of MB was achieved under neutral conditions, and the adsorption process was consistent with quasi-secondary kinetics and Langmuir isotherm models. The fitting results of the Langmuir isotherm model showed that the maximum adsorption capacities of the cation-modified GO membranes for MB were 654.9, 319.8, and 246.3 mg/g, respectively. The maximum adsorption capacities of the cation-modified GO/MXene membranes for MB were 687.3, 497.6, and 772.4 mg/g, respectively. Furthermore, the results of the intraparticle diffusion model revealed that the entire adsorption process was controlled by both external and internal diffusion. The thermodynamic analysis results indicated that the entire adsorption process was a heat-absorbing process and could proceed spontaneously. That the findings suggest that the Na+-modified GO and Al3+-modified GO/MXene membranes demonstrate the best adsorption effects and are promising adsorbents for MB removal.

Smart fabrication of CaFe2O4 using water in-solution organic fuels via facial combustion route and its multidimensional application in dye elimination

In the present work, successive nanomagnetic-porous CaFe2O4 (CFO) fabrication was achieved using pioneer water-insoluble organic fuels in the sustainable combustion technique and examined to eliminate hazardous Acid Fuchsin (AF) dye from simulated wastewater. The synthesized CFO samples exhibit miscellaneous morphology, including rock-strewn sharp-edge cubic to porous honeycomb particles examined by FESEM analysis. The CFO shows a high surface area (36.7 to 71.2 m2/g), orthorhombic structure, and superparamagnetic nature (magnetic saturation 19.5 to 24.6 emu/g). The AF adsorption mechanism was investigated through isotherm and kinetic study, wherein the Langmuir model and the pseudo-second-order (PSO) kinetic model describe the AF adsorption. The Langmuir maximum monolayer adsorption capacity was found to be 1083 to 2505 mg/g for F1-CFO to F4-CFO (F1-F4 represent fuel 1 – fuel 4) adsorbents. However, the Intraparticle diffusion model (IPDM) shows the multi-linearity plot, suggesting that more than two mechanisms were involved in the adsorption process. The adsorption rate suggests that the morphology of the adsorbent mainly influences the adsorption process. The PSO rate constant was found to be 6.96E-05, 1.00E-04, 1.28E-04, and 1.59E-04 g/mg min-1for F1-CFO, F2-CFO, F3-CFO, and F4-CFO respectively. Innovative visible-light aided photocatalytic regeneration approach effectively generates (heterogeneous activation H2O2) exhausted adsorbents up to eight consecutive cycles: the manifold efficiency and facile magnetic isolation of CFO nanomaterial directed to the sustainable solution in environmental remediation.

Stabilization and sustained release of rutin dye via eco-friendly Zn/Al-LDH adsorbent: Kinetic, thermodynamic, and antioxidant investigations

This study focuses on the stabilization of rutin dye by intercalating it within Zn/Al-LDH (R-Z/A-L) through co-precipitation (CO) and ion exchange (IO) methods. For the IO method, rutin was intercalated onto Z/A-L using a circulator, achieving an optimal intercalation efficiency of 86.37 % and a capacity of 43.18 mg g−1. Comprehensive characterization of the intercalated compounds was performed using XRD, FTIR, FE-SEM, TEM, TGA, DSC, BET, and XPS techniques, confirming efficient intercalation of rutin into LDH. Kinetic analysis indicated that the pseudo-second-order and intraparticle diffusion models best illustrate the intercalation and release mechanisms, respectively. Isotherm data supported the Langmuir model as the most accurate for describing rutin's intercalation behavior. Thermodynamic investigation disclosed the process to be endothermic and spontaneous. Using the CO method, R-Z/A-L was synthesized under optimal conditions with varying rutin concentrations (5 %, 15 %, and 25 %), achieving maximum intercalation efficiencies and capacities up to 98.15 % and 49.07 mg g−1, respectively. Additionally, the antioxidant activity of the intercalated rutin was evaluated, showing that its integration into the adsorbent allowed for prolonged and consistent release. These results confirm the effectiveness of the Z/A-L adsorbent in enhancing stability.

(Battery Student Slam 8 Award Winner) Multi-Clustered Lithium Diffusion in Single-Crystalline NMC Battery Particles

Understanding the diffusion dynamics of lithium within solid-state electrodes is pivotal for developing high-performance batteries. In this context, layered oxides were utilized as a promising cathode material due to their high energy density and fast intraparticle lithium diffusivity. Despite advancements in material composition, coating, and doping, the understanding of intraparticle lithium diffusion has long been described by Fick's law. Conventionally, lithium diffusion is assumed to generate a monotonic lithium concentration gradient within solid-solution single-crystalline battery materials during cycling. This raises fundamental questions about diffusion in layered oxides; (1) Can the diffusion of Li in solids be interpreted as Fickian diffusion, similar to diffusion in gases or liquids, even though it involves structural and phase evolution throughout the battery cycle? and, (2) Does the fast diffusivity (10-11-10-9 cm2/s) support the homogenization of Li?In this study, we address these questions surrounding lithium diffusion in layered oxide by utilizing operando scanning transmission X-ray microscopy. We revealed the formation of mobile Li-dense/-dilute nano-domains within individual single-crystalline LiNi1/3Mn1/3Co1/3O2 (scNMC) during battery cycles. We term this phenomenon ‘multi-clustered lithium diffusion’, distinguishing our findings from the conventionally suggested Fickian diffusion model in solid-solution materials. These domains persist for at least 4 hours during relaxation, accompanied by locally residing strained domains, as confirmed by Bragg coherent diffraction imaging (BCDI), within a single particle. We believe these domains arise due to the compensation of localized chemical potential gradients that are generated by the sustained presence of strain within the battery particles during cycling.While maintaining integrity of Li-dense/-dilute domain at various C-rates, STXM result further show that Li-dilute domains maintain during the discharging. Given the lower concentration of Li at insertion boundaries, which could lower the surface charge transfer impedance of the system, Li-dilute domains facilitate lithium transport by functioning as low-resistance pathways. Through a comprehensive analysis of electrical impedance spectroscopy (EIS), STXM imaging and finite element analysis (FEA), we showed that controlling the local domain fraction is crucial for controlling the overpotential during subsequent charging. Our study introduces new insights into nanoscale solid-state diffusion, thereby enabling the fabrication of high-performance batteries. Figure 1

Mixed-Mode Adsorption of l-Tryptophan on D301 Resin through Hydrophobic Interaction/Ion Exchange/Ion Exclusion: Equilibrium and Kinetics Study.

The adsorption of l-tryptophan (l-Trp) was studied based on the hydrophobic interaction/ion exchange/ion exclusion mixed-mode adsorption resin D301. Firstly, the interaction mode between l-Trp and resin was analyzed by studying the influence of pH variation on the adsorption capability and the dissociation state of l-Trp. Secondly, the adsorption mechanism was illuminated by studying the adsorption equilibrium and kinetic behaviors. The adsorption equilibrium and a kinetics model were constructed. The augmentation of pH gradually elicited an enhancement in the adsorption capacity of l-Trp. l-Trp existing in varied dissociation states could be adsorbed by the resin, and the interaction mode relied upon the pH of the solution. An integrated adsorption equilibrium model with the coadsorption of different dissociation states of l-Trp was developed and could predict the adsorption isotherms at various pH levels satisfactorily. Both external mass transfer and intra-particle diffusion collectively imposed constraints on the mass transfer process of l-Trp onto the resin. An improved liquid film linear driving force model (ILM) was constructed, and the model provided a satisfactory fit for the adsorption kinetics curves of l-Trp at various pH levels. l-Trp molecules had a high mass transfer rate at a relatively low solution pH.

Adsorption characteristics and mechanisms of bisphenol A on novel nitrogen-modified biochar derived from waste masks and biomass.

Resource utilization of waste masks has become an urgent scientific issue. In this work, with sustainably, waste masks and biomass were co-pyrolysis with oxygen limitation to prepare mask-based biochar (MB). Then, urea was introduced to prepare novel nitrogen modified mask-based biochar (NMB) via a one-step hydrothermal synthesis method. The adsorption characteristics of NMB on the emerging environmental pollutant, bisphenol A (BPA), were evaluated via batch adsorption tests. Moreover, the physicochemical properties of the materials were characterized with various advanced techniques. Also, the roles of waste masks and nitrogen modification were explored. The adsorption mechanisms of NMB on BPA were revealed as well as the performance differences between different adsorbents. The results showed that waste masks participated in thermochemical reactions, shaped the microsphere structure of biochar, and increased the types of surface functional groups. The nitrogen modification enriched the surface elemental composition and activated the specific surface area via the mesopore. These would enhance the adsorption performance. The maximum adsorption of BPA by NMB was 62.63mg·g-1, which was approximately 2.35-5.58 times higher than that of the control materials. Temkin model and pseudo-second-order model optimally simulate the isothermal and kinetic adsorption, respectively. The adsorption mechanisms are jointly by physical and chemical adsorption, which mainly includes π-π interaction, hydrogen bonding, intraparticle diffusion, surface adsorption, and ion exchange. After discussion and evaluation, NMB has lower preparation process cost (7.21 USD·kg-1) and safety, with potential for environmental applications. This study aims to expand new ideas for the comprehensive utilization of waste masks and the preparation of eco-friendly materials. Moreover, it provides a theoretical basis for the removal of BPA.

Prosopis juliflora biochar for adsorption of sulfamethoxazole and ciprofloxacin from pharmaceutical wastewater

This study aimed to synthesize the biochar of Prosopis juliflora (PJ) and apply it to the adsorption of antibiotic residues sulfamethoxazole (SMZ) and ciprofloxacin (CIX) from pharmaceutical industry wastewater. The PJ biochar was synthesized using the pyrolysis method and characterized by proximate analysis, TGA, SEM-EDX, FTIR, XRD, and BET methods. The moisture content, volatile matter, ash content, and fixed carbon were found to be 6.4 %, 72.3 %, 3.0 %, and 18.3 %, respectively. Moreover, biochar characteristics were described by a high BET surface area of 875 m2/g, various FTIR peaks with different functional groups, high TGA thermal stability at increasing temperature, amorphous XRD structure, and high SEM surface morphology, and major EDX carbon compositions of 97 %. These analysis results demonstrated insights into the potential and nature of biochar adsorbent. The maximum adsorption of SMZ and CIX was found to be 98.7 % and 97.8 %, respectively, at a contact time of 120 min, initial concentration of 50 mg/L, pH (5 for CIX and 8 for SMZ), and adsorbent dose of 1 g/L for a synthetic solution. On the other hand, COD and TOC of real wastewater were reduced from 2498 to 514 mg/L and 1050 to 124 mg/L during the real wastewater treatment. Target pollutants concentration in real wastewater was found to be 8.29 and 5.3 mg/L for CIX and SMZ and their removal efficiency was obtained as 80.4 % and 76.7 % respectively. The obtained experimental data were best fitted with the Langmuir isothermal model at R2 = 0.999, implying the adsorbent surface is homogeneous and monolayer. Similarly, the adsorption kinetics process was well described by a pseudo-second-order kinetics model for both SMZ and CIX at R² = 0.999. Finally, the non-linear intra-particle diffusion graphs suggest that chemical adsorption is the main influencing factor for overall kinetics. In conclusion, using PJ biochar is a promising precursor in advancing adsorbents for removing contaminants from industrial wastewater to address environmental pollution challenges.

Study on the adsorption efficiency and mechanism of Sb(V) in aqueous solutions using enhanced surfactant-modified iron-calcium composite

The presence of Sb(V) in aqueous solutions poses a significant threat to the surrounding environment, and current treatment methods are inadequate. In this study, a magnetic surfactant (CTAB)-modified iron-calcium composite (CTAB-IC) was successfully synthesized using iron-calcium composite as the base material. This novel composite was used for the efficient removal of Sb(V) from textile wastewater solutions. Characterization analyses revealed that the CTAB-IC material exhibits a rich long-prismatic structure and superparamagnetic properties, classifying it as a soft magnetic material. Post-adsorption particle agglomerates were found to comprise Ca, S, and O. Sequential batch experiments demonstrated a maximum adsorption capacity of 54.05 mg/g, with adsorption kinetics data fitting the pseudo-second-order model. The intraparticle diffusion model indicated the presence of multiple diffusion steps during the adsorption process. Additionally, the adsorption of Sb(V) by CTAB-IC was identified as a heterogeneous surface adsorption process, best described by the Freundlich model. The primary adsorption mechanisms involved the formation of surface Ca-O-Sb complexes and inner-sphere Fe-O-Sb complexes, as well as amorphous surface precipitation and electrostatic adsorption. Notably, the treatment of textile wastewater often results in iron-calcium-rich sludge, which is challenging to manage and valorize. This study explored the potential for resource recycling by utilizing CTAB to harness the Fe elements in textile wastewater sludge, thereby promoting waste-to-resource conversion.

Selective lead capture using amide-containing COFs: A novel strategy for efficient soil remediation

A critical consideration in the application of phytoremediation to remediate sludge soil contaminated with heavy metals is the potential for leaching risks that prevail prior to the efficient uptake of these metals by plants. The most cost-effective method is to use heavy metal stabilizers with selective adsorption. A novel amide-based COF material (COF-TH) has been synthesized as a heavy metal stabilizer for Pb. COF-TH exhibits significant selectivity for Pb in five-metal-mixed solutions, with a distribution coefficient KD as high as 3279 mL·g–1, which was more than 7.3 times that of other heavy metals. The maximum adsorption capacity of COF-TH for Pb was 189 mg·g–1. The adsorption fitted Langmuir model and intra-particle diffusion model, and satisfied pseudo-second-order kinetic model. The excellent selectivity and adsorption performance originate from the complexation between abundant amide groups and Pb ions. Pot experiments and leaching assays confirm that COF-TH decreased Pb leachate concentrations by 77.8 % without significantly decreasing total phytoextracted amounts of other heavy metals, due to the high selectivity of COF-TH to Pb. Additionally, its positive impact on plant growth and microbial diversity makes it a promising soil remediation agent. This investigation offers a novel approach to mitigate the leaching risk of a specific heavy metal Pb during sludge land application by integrating soil phytoremediation with stabilization techniques.

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.