Isothermal Analysis Research Articles

Design and utilisation of a novel poly imino-phosphorane composite for the effective removal of Pb2+ and Cr3+ ions from contaminated water sources

ABSTRACT This study introduces a novel chitosan-immobilised imino-phosphorane composite (Chi-iph) for the efficient removal of lead (Pb2+) and chromium (Cr3+) from wastewater. The successful synthesis of Chi-iph was confirmed using FT-IR, XPS, BET, EDX, TGA, 1H-NMR, 13C-NMR, EI/MS, and ICP-OES analyses. Various experimental parameters such as pH, equilibrium time, metal concentration, adsorbent dose, temperature, and eluents were optimised to enhance the adsorption performance. At 25°C, with pH values of 5.5 for Pb2+ and 4.5 for Cr3+, an initial concentration of 200 mg/L, and an agitation time of 20 min, the maximum adsorption capacities were 55 mg/g for Pb2+ and 45 mg/g for Cr3+. Kinetic modelling demonstrated that the pseudo-first-order model best predicted the adsorption process, yielding capacities of 56.65 mg/g for Pb2+ and 46.38 mg/g for Cr3+. Isotherm analysis showed that the Langmuir model was a better fit than the Freundlich model, with theoretical capacities of 56.81 mg/g for Pb2+ and 44.64 mg/g for Cr3+. The Dubinin–Radushkevich (D-R) isotherm revealed adsorption energy (E) values of 9.45 kJ/mol for Pb2+ and 8.64 kJ/mol for Cr3+, indicating a chemisorption process. Theoretical saturation capacities (qD) were 56.28 mg/g for Pb2+ and 45.58 mg/g for Cr3+. Temkin isotherm results, with bT values of 9.71 and 8.53 kJ/mol for Pb2+ and Cr3+ respectively, aligned closely with the D-R model, further confirming chemisorption. Thermodynamic studies indicated that the adsorption process is exothermic, spontaneous, and more favourable at lower temperatures. Complete desorption of the heavy metals was achieved using 1 M HNO₃, allowing for efficient metal recovery. In a practical application, the Chi-iph composite removed 11.5 mg/L of Pb2+ and 7.01 mg/L of Cr3+ from contaminated wastewater, demonstrating its potential for environmental remediation. The composite’s performance aligns with WHO and FAO guidelines, making it suitable for treating wastewater before disposal into marine environments.

The chemoreceptor controlling the Wsp‐like transduction pathway in Halomonas titanicaeKHS3 binds and responds to purine derivatives

The chemosensory pathway HtChe2 from the marine bacterium Halomonas titanicae KHS3 controls the activity of a diguanylate cyclase. Constitutive activation of this pathway results in colony morphology alterations and an increased ability to form biofilm. Such characteristics resemble the behavior of the Wsp pathway of Pseudomonas. In this work, we investigate the specificity of Htc10, the only chemoreceptor coded within the HtChe2 gene cluster. The purine derivatives guanine and hypoxanthine were identified as ligands of the recombinantly produced Htc10 ligand‐binding domain, with dissociation constants in the micromolar range, and its structure was solved by X‐ray protein crystallography. The sensor domain of Htc10 adopts a double Cache folding, with ligands bound to the membrane‐distal pocket. A high‐resolution structure of the occupied guanine‐binding pocket allowed the identification of residues involved in ligand recognition. Such residues were validated by site‐directed mutagenesis and isothermal titration calorimetry analyses of the protein variants. Moreover, heterologous expression of Htc10 in a Pseudomonas putida mutant lacking the native Wsp chemoreceptor promoted biofilm formation, a phenotype that was further enhanced by Htc10‐specific ligands. To our knowledge, this is the first description of binding specificity of a chemoreceptor that controls the activity of an associated diguanylate cyclase, opening the way for dynamic studies of the signaling behavior of this kind of sensory complex.

Removal of hexavalent chromium and pentavalent arsenic from aqueous solutions by adsorption on polyethylenimine-modified silica nanoparticles.

Chromium and arsenic are commonly found in water and wastewater as hexavalent chromium, Cr(VI), and inorganic arsenic species, such as pentavalent arsenic, As(V). In aqueous media, both Cr(VI) and As(V) exist predominantly in the form of oxy-anions. In our study, we prepared a polyethylenimine-silica composite material (SiO₂-PEI) as an adsorbent to study the adsorption capacity for chromate and arsenate ions. Polyethylenimine (PEI) can effectively bind negatively charged species through electrostatic interactions. The parameters that were evaluated, regarding the adsorption capacity were the effect of pH, the effect of the initial concentration of Cr(VI) and As(V), and the presence of other anions. Also, we examined the effect of Cr(VI) and As(V) on each other by studying the simultaneous removal of chromate and arsenate ions. Isotherm, kinetic, and thermodynamic analyses on the experimental data obtained were conducted. The results showed that the pH of the solution is affecting the charge density of PEI, and at pH 4, the lower value that was examined, the SiO₂-PEI exhibited higher adsorption capacity. The presence of other anions, such as phosphate, nitrate, and sulfate ions, had an adverse effect on the adsorption capacity of the SiO₂-PEI material for both chromate and arsenate ions. The adsorption capacity of arsenate was more affected by the presence of other anions compared to the chromate, and the higher impact was observed by the sulfate ions at pH 4, on the contrary for the chromate ions the higher impact was observed by the sulfate ions at pH 7 and by the phosphate ions at pH 4. Concerning the effect of temperature, the adsorption is an exothermic process and it was more favorable at lower environmental temperature. The study of simultaneous removal of Cr(VI) and As(V) declares the material's ability to accommodate both types of ions without requiring separate treatment steps. Addressing the simultaneous removal is essential for reducing the complexity of water treatment systems, lowering operational costs, and improving the safety of treated water.

Experimental and theoretical insights into the adsorption mechanism of methylene blue on the (002) WO3 surface

This work investigates the efficiency of green-synthesized WO3 nanoflakes for the removal of methylene blue dye. The synthesis of WO3 nanoflakes using Hyphaene thebaica fruit extract results in a material with a specific surface area of 13 m2/g and an average pore size of 19.3 nm. A combined theoretical and experimental study exhibits a complete understanding of the MB adsorption mechanism onto WO3 nanoflakes. Adsorption studies revealed a maximum methylene blue adsorption capacity of 78.14 mg/g. The pseudo-second-order model was the best to describe the adsorption kinetics with a correlation coefficient (R2) of 0.99, suggesting chemisorption. The intra-particle diffusion study supported a two-stage process involving surface adsorption and intra-particle diffusion. Molecular dynamic simulations confirmes the electrostatic attraction mechanism between MB and the (002) WO3 surface, with the most favorable adsorption energy calculated as -0.68 eV. The electrokinetic study confirmed that the WO3 nanoflakes have a strongly negative zeta potential of -31.5 mV and a uniform particle size of around 510 nm. The analysis of adsorption isotherms exhibits a complex adsorption mechanism between WO3 and MB, involving both electrostatic attraction and physical adsorption. The WO3 nanoflakes maintained 90% of their adsorption efficiency after five cycles, according to the reusability tests.

Versatile silicate-modified hydrochar based on Scutellaria baicalensis-residue for efficiently removing heavy metal-antibiotic co-contamination and relevant bio-contaminants from wastewater

In this study, we utilized typical Chinese medicine herbal residues (CMHRs)－Scutellaria baicalensis (Scutellaria baicalensis Georgi) residue (SR), as the raw material and employed Na2SiO3 and Fe2(SO4)3 as modifying agents to fabricate a novel and multifunctional hydrochar (FeSi-SRHC), which was designed for comprehensive removal of typical contaminants such as Cu2+, Zn2+, tetracycline (TC), and ciprofloxacin (CIP), along with relevant bio-contaminants (resistant bacteria (RBs) and resistance genes (RGs)) present in wastewater. Based on the analysis of adsorption kinetics and Freundlich isotherm, it was found that FeSi-SRHC exhibited physical monolayer adsorption for Cu2+/Zn2+ while mainly chemical multilayer adsorption for TC/CIP in single-contamination system. Furthermore, Langmuir isotherm demonstrated excellent adsorption capacity of FeSi-SRHC towards Cu2+/Zn2+/TC/CIP with maximum capacities of 255.75, 265.26, 425.53, and 404.86 mg/g, respectively. In the co-contamination system, the presence of Cu2+, Zn2+, TC, and CIP exhibited varying degrees of inhibitory or promotive effects on the mutual adsorption by FeSi-SRHC. This divergence stemmed from differences in complexation intensities and concentration ratios among diverse co-existing contaminants. Based on XPS and Density Functional Theory (DFT) analyses, the adsorption process for Cu2+, Zn2+, TC, and CIP by FeSi-SRHC primarily involves pore fill, complexation reactions, ion exchange, hydrogen bonding, π-π stacking interactions, and electrostatic interactions. Bio-contaminant removal experiments revealed that the release of baicalin and wogonoside from FeSi-SRHC disrupts the structure of RBs cells and compromises the integrity of resistance plasmids. The practical application experiment showed that FeSi-SRHC displayed favorable performance for removing heavy metals, antibiotics, and bio-contaminants in actual wastewater. This study presented a “Treating waste with waste” strategy, which provided a method with low carbon, eco-friendly, and inexpensive for CMHRs resources and turning waste into treasure while proposing a idea to address the challenges associated with treating heavy metal, antibiotic, and bio-contaminant contamination in wastewater.

Adsorption of malachite green dyes from aqueous solution by metal organic framework-5 incorporated coal fly ash (MOF-5/CFA)

Dye contamination of water is a global issue with significant environmental and health risks. This research explores the use of metal organic framework-5 (MOF-5) adsorbents modified with coal fly ash to effectively remove malachite green (MG) dye from water, addressing global dye pollution. Preliminary batch adsorption experiments showed that the addition of CFA to MOF-5 significantly increased the removal efficiency of MG dye (77.90 ± 1.74%) compared to using pristine MOF-5 (30.00 ± 2.14%). Batch adsorption studies showed that MG adsorption efficiency increased with shaking rate and contact time but decreased with adsorbent dosage. Temperature study reveals exothermic behavior of adsorption process. MOF-5/CFA adsorbents can be regenerated for up to four cycles. The results demonstrated that the highest adsorption efficiency of 80.32 ± 0.90% was achieved under the following conditions: a stirring speed of 300 rpm, a dosage of 0.3 g of MOF-5/CFA adsorbent, a temperature of 27 °C, 2 h contact time, and an initial dye concentration of 100 mg/L. Analysis of adsorption isotherms and kinetics revealed that the Langmuir isotherm and pseudo-second-order kinetic models provided the most accurate fit to the experimental data. FTIR analysis revealed significant functional groups in the prepared adsorbent and only minor spectral changes in the spent adsorbents. SEM analysis showed a rough, porous MOF-5/CFA surface before dye adsorption, becoming smoother and less porous afterwards. This study demonstrates the promise of MOF-5/CFA as an alternative adsorbent for the removal of MG dyes from water, paving the way for advances in wastewater treatment and the sustainable use of industrial waste materials.

Sustainable cost-effective chemically modified banana leaf powder for methyl blue dye removal: kinetics, isotherm, thermodynamics and artificial intelligence-based analysis

This study investigates cellulose-based adsorbents that are naturally occurring and have a unique, abundant supply for adsorbing organic dye. The effectiveness of chemically modified banana leaf powder (CMBLP) as a biodegradable and environmentally friendly adsorbent for extracting methyl blue (MB) dye from aqueous solutions was studied. Point-zero charge (pHpzc) analysis, scanning electron microscopy (SEM), X-ray energy dispersion (EDS), and Fourier transform infrared spectroscopy (FTIR) were used to characterize the CMBLP. At pH 6.0, 100 mg/L of dye, 50 min of contact time, and 300 K temperature, the maximum removal values were obtained. Under ideal circumstances, CMBLP displays 77.13215% removal rate. Langmuir and Freundlich models, along with pseudo-first- and pseudo-second-order kinetics equations, were used to investigate the equilibrium isotherm and kinetics of CMBLP. The acquired experimental data fit pseudo-second-order kinetics (R2 = 0.9986 and 0.9984) and the Langmuir isotherm (R2 = 0.9996) better. Utilizing the Langmuir isotherm model, the maximum adsorption capacity (qmax) of CMBLP has been identified to be 118.24 mg/g. At a temperature of 300 K, the adsorbent was also able to adsorb the maximum amount of methyl blue (MB). The thermal properties of methyl blue (MB) dye adsorption validate the spontaneous and exothermic nature of the adsorption process. The majority of statistical and artificial intelligence-based model (like KNN, SVM, ANN and LSTM) validate the superiority of MB removal onto CMBLP and support our experimental findings.Graphical

Carbon dot aggregates: a new strategy to promote corrosion inhibition performance of carbon dots

The corrosion of metal not only produces serious economic losses and environmental pollution but also threatens equipment safety. Carbon dots (CDs) exhibit outstanding inhibition properties to availably retard the corrosion of metal. However, the present CDs-based corrosion inhibitors still fail to fully exert the environmentally friendly and low-cost merits of CDs. To address this issue, CD aggregates (CDAs) prepared by low-cost and eco-friendly CDs are developed as novel corrosion inhibitors for the first time, and their corrosion inhibition mechanism is disclosed. Specifically, CDAs with excellent long-term dispersion stability are synthesized by solvothermal treatment of CDs formed by citric acid and urea. CDAs at only 200 mg/L provide a corrosion inhibition effect of 90.38% for Q235 carbon steel in 1 mol/L HCl solution, approximately 1.53 times higher than that of CDs (59.21%). Moreover, the corrosion inhibition mechanism of CDAs is proposed through the analysis of adsorption isotherm, examination of corrosion morphologies, and theoretical calculations. That is, CDAs physically and chemically adsorb on the carbon steel surface, mainly hindering its anodic reaction, thus retarding the corrosion of carbon steel. This research firstly verifies the corrosion inhibition potential of green and low-cost CDAs and provides a novel strategy to promote the corrosion inhibition performance of CDs, promoting the progress of aggregate-based corrosion inhibitors.

The simultaneous application of fulvic acid and protein hydrolysate biostimulants enhances cucumber responses to Fe deficiency

Iron (Fe) is widely recognized as a critical factor in limiting crop production; however, eco-friendly strategies to address its deficiency are still required. The use of biostimulants has displayed promising results in mitigating Fe deficiency. Our hypothesis was that the combined application of two biostimulants with distinct molecular structures - fulvic acid (FA) and protein hydrolysate (PH) - could be more effective than the use of a single compound. The simultaneous presence of FA and PH (MIX) in a Fe-free nutrient solution led to a redistribution of endogenous Fe, resulting in a higher leaf SPAD index. Furthermore, the addition of FeCl3 as a Fe source (resupply) in MIX-treated plants enhanced the biostimulant effect, as evidenced by increased dry root and shoot weight and a more developed root system. In addition, the expression of Strategy-I-related genes, CsFRO1 and CsIRT1, remained elevated. These effects can be attributed to improved interaction between the roots and biostimulants through the formation of the FA-PH complex, as demonstrated by circular dichroism and isothermal titration calorimetry analyses.

Improved Carboxylate Density in Functionalized Biochar for Methylene Blue Adsorption

AbstractCarboxylate appended biochar BCKA was synthesized by a two‐step functionalization of leached rice straw biochar using ethyl 2‐bromoacetate/K2CO3/DMF and hydrolysis to furnish the modfied biochar. The modified biochar was characterized using proximate analysis, CHNS, SS CPMAS 13C NMR, FESEM, FTIR, XPS, BET, and zeta potential. Biochar BCKA was optimized for pH and dose, respectively, as 7 and 0.2 g/L for methylene blue (MB) adsorption with a contact time of 6 h at 298 K. MB removal up to 98% from 20 mg/L dye solution, using BCKA as adsorbent pH 7, 298 K. The nonlinear fit to Langmuir, Freundlich, Temkin, SIPS, and D‐R adsorption isotherm showed a good fit with correlation coefficients (R2) 0.970, 0.969, 0.988, 0.984, and 0.983, respectively, and maximum MB adsorption (qm) of 261 mg/g. Thermodynamic parameters for the adsorption of MB using BCKA were 38.72 kJ/mol (∆H°), 225.42 J/mole K (∆S°), and negative ∆G° confirming the spontaneity driven by entropy. Kinetic studies showed good nonlinear fit to pseudo‐second order (R2 0.967), intraparticle diffusion (R2 0.977), and Elovich equation (R2 0.958) with chemisorption‐based interaction between BCKA and MB. Chemisorption, particularly ion exchange on the surface of BCKA with MB, is inferred from the D‐R isotherm and kinetic analysis. Column breakthrough studies showed Thomas model fit with qt 267.09 mg/g, and efficiency >80% was retained for two cycles of MB adsorption.

Preparation of magnetic composite titanium-based MOFs for rapid and effective lead ion adsorption in aqueous solution

Lead contamination constitutes a significant risk to ecology and human beings, which necessitates the development of efficient lead removal adsorbents. In this context, magnetic composite MOFs are promising as they combine the tunable properties and high specific surface area of MOFs with the easy recyclability of magnetic materials. In this study, a novel magnetic composite material, DMP-MIL@Fe3O4, was synthesized by loading magnetic Fe3O4 on titanium-based MOFs and postmodifying it with 4,6-diamino-2-mercaptopyrimidine. The adsorption capacity was maximized within 20 min at pH 6.0 and room temperature. At the same time, it has very high adsorption efficiency for lead ions, with a maximum adsorption capacity of 200.1 mg/g. The adsorption mechanism of DMP-MIL@Fe3O4 was elucidated by kinetic, isothermal and thermodynamic analyses. Pseudo-second-order modeling showed that the binding of functional groups to lead ions was the key rate-limiting step. Isotherm modeling confirmed that multiple functional groups work together to promote the adsorption of lead ions, while thermodynamic analysis demonstrated the spontaneous endotherm of the adsorption process. DMP-MIL@Fe3O4 also exceled in selective adsorption of lead ions and recyclability.

Simplified synthesis of BaZn2(PO4)2 conversion coating with enhanced corrosion resistance

Phosphate conversion coatings with high corrosion resistance are crucial for the rapid advancement of anti-corrosion systems for steel materials used in aviation. In this study, BaZn2(PO4)2 coating was synthesized using a chemical liquid phase deposition method and characterized by X-ray diffraction, scanning electron microscopy, and N2 adsorption–desorption isotherm analysis. Electrochemical tests revealed that the dense stacking morphology of the BaZn2(PO4)2 coating led to a significant decrease in electrochemical active surface area, electrochemical impedance response, and corrosion potential. As a result, the BaZn2(PO4)2 coating exhibited satisfactory anti-corrosion performance in 3 wt% NaCl solution.

A Facile Synthesis of RGO-Ag2MoO4 Nanocomposites for Efficient Lead Removal from Aqueous Solution

Efficiently treating wastewater, particularly the elimination of heavy metal ions from water systems, continues to be one of the most pressing and complex challenges in modern environmental management. In this work, reduced graphene oxide coupled silver molybdate binary nanocomposites (RGO-Ag2MoO4 NCs) have been prepared via hydrothermal method. The crystalline nature and surface properties of the developed RGO-Ag2MoO4 NCs were proved by XRD, FTIR, SEM, and EDS techniques. Adsorption experiments demonstrated that the nanocomposites (NCs) effectively removed Pb(II) ions within 120 min, achieving a maximum removal efficiency ranging from 94.96% to 86.37% for Pb(II) concentrations between 20 and 100 mg/L at pH 6. Kinetic studies showed that the adsorption process followed a pseudo-second order model. Isotherm analysis presented that the Langmuir model provided the greatest fit for the equilibrium data, with a monolayer adsorption capacity of 128.94 mg/g. Thermodynamic analysis revealed that the adsorption process was spontaneous and endothermic. The results of this study highlight RGO-Ag2MoO4 NCs as a highly promising and eco-friendly material for the effective elimination of Pb(II) ions from wastewater. Their strong adsorption capacity, coupled with sustainable properties, makes them an efficient solution for addressing lead contamination, offering significant potential for practical applications in water treatment systems.

Regulation of Adsorption Properties of Whey Protein Isolate Fibril-Calcium Alginate Aerogels by Controlling Protein Fibrillation Time.

Amyloid-like fibrils have a relatively high specific surface area, which makes them suitable as absorbents. In this study, we prepared absorbent composite aerogels from whey protein isolate fibril (WPIF) and calcium alginate (CA). The impact of protein fibrillation time (4-24 h) on the adsorption properties of these aerogels was assessed, as this influences the nature of the WPIFs formed. Fourier transform infrared spectroscopy analysis indicated that hydrogen bonding, hydrophobic interactions, and electrostatic interactions were the main molecular interactions in the composite aerogels. Then, the adsorption properties of the aerogels were investigated using crystal violet as a model compound. The adsorption properties of all composite aerogels were significantly improved compared to CA aerogels, which was mainly attributed to the numerous functional groups of the surfaces of the WPIFs, as well as the rougher surface topology of the composite aerogels. The adsorption capacity of the composite aerogels first increased and then decreased with increasing fibrillation time, with 8 h fibrillation leading to the largest adsorption capacity (1886.11 mg/g). Thioflavin T fluorescence, atomic force microscopy, light extinction, average particle size, and zeta potential analysis indicated that the high fibril content, mature fibril morphology, large number of available functional groups on the surface, and relatively low zeta potential of WPIF8 might be the main reasons. Adsorption kinetics and isothermal adsorption profile analysis suggested that monolayer adsorption occurred through chemical adsorption processes. The edible aerogel with high adsorption properties developed in this work has potential application in food and biomedical fields.

Effective remediation of toxic metal ions (Cd(II), Pb(II), Hg(II), and Ba(II)) using mesoporous glauconite-based iron silicate nanorods: Experimental and theoretical studies

Glauconite minerals underwent an advanced exfoliation and scrolling process, yielding novel iron silicate nanorods (GRs) with increased surface area, reactivity, and improved physicochemical properties. These structures were introduced as superior adsorbents for the highly efficient adsorption of various toxic metal ions, such as Cd(II), Pb(II), Hg(II), and Ba(II). The GRs exhibited maximum adsorption capacities of 283 mg/g for Cd(II), 247 mg/g for Pb(II), 132.3 mg/g for Hg(II), and 165.2 mg/g for Ba(II). The adsorption properties of the GRs during the adsorption of these four metal ions were elucidated through traditional (Langmuir model) and advanced (monolayer model of single energy site) isotherm analyses. Advanced isotherm modeling revealed that the GR surface was saturated with numerous effective adsorption sites, with densities of 125 mg/g for Cd(II), 68.8 mg/g for Pb(II), 40.9 mg/g for Hg(II), and 57.9 mg/g for Ba(II). Moreover, each site could accommodate approximately four ions of the studied metals, which are vertically oriented and participate in multi-ionic adsorption reactions. Energetic analyses, whether based on classical models (Gaussian energy <8 kJ/mol) or advanced models (adsorption energy <40 kJ/mol), indicated that the adsorption processes are governed by physical mechanisms, including electrostatic attractions, van der Waals forces, and hydrogen bonding. Furthermore, thermodynamic assessments confirmed that the adsorption of these ions occurs through exothermic and spontaneous reactions.

Improving In Situ Combustion for Heavy Oil Recovery: Thermal Behavior and Reaction Kinetics of Mn(acac)3 and Mn-TO Catalysts

In this research work, the catalytic performances of two manganese-based catalysts, manganese (III) acetylacetonate (Mn(acac)3) and manganese tallate (Mn-TO), were studied during the process of Ashalcha heavy oil oxidation under in situ combustion conditions. DSC analysis shows distinct thermal behavior of both ligated catalysts during low- and high-temperature oxidation phases (LTO and HTO); for example, the shifting in peak temperature (Tp) in the HTO at a heating rate of 10 °C/min was reduced by approximately 5.3% for Mn-TO and 2.24% for Mn(acac)3 when compared with uncatalyzed heavy oil. Combined isothermal kinetic analyses using the Friedman and Kissinger–Akahira–Sunose analytic methods have provided insights about activation energies and frequency factors over the whole conversion range, where the catalytic performance of Mn-TO showed low activation energies in both LTO and HTO (Eα of Mn-TO was approximately 13.33% (LTO) and 7.68% (HTO) less than with the heavy oil alone). In addition, calculations of the effective rate constant confirmed the increased oxidation rate trend of both catalysts, with Mn-TO exhibiting the highest values. The findings highlight the potential of these manganese-based catalysts, the Mn-TO catalyst in particular, in optimizing heavy oil oxidation processes. The overall results further contribute to developing more efficient ligand catalyst complexes for sustainable heavy oil recovery while continuously improving their efficient application during in situ combustion in the petroleum industry.

Corrosion Inhibitory Evaluation of Indole-3-Carbaldehyde 4-Methyl-3-Thiosemicarbazone on Mild Steel: Weight Loss, Langmuir Isotherm, SEM-EDX and DFT Analysis

Corrosion Inhibitory Evaluation of Indole-3-Carbaldehyde 4-Methyl-3-Thiosemicarbazone on Mild Steel: Weight Loss, Langmuir Isotherm, SEM-EDX and DFT Analysis

Nutrient recovery from urine: Urea adsorption onto biochar integrated with Na-chabazite as urease inhibitor

This study presents an innovative technical integration for concomitant nutrient recovery from source-separated urine. While cation exchange is known for efficient K+ recovery, it faces competition due to the high molarity of NH4+ in hydrolyzed urine. This study proposes inhibiting urease activity to facilitate the recovery of K⁺ and urea from fresh urine. Na-chabazite was first proposed as a urease inhibitor in this study, reducing urease activity by 50 %. Wood biochar, with its high porosity (308.0 m²/g) and polar functional groups, shows a urea adsorption capacity of 25.4 mg/g, which can be further improved by steam activation. The isotherm analysis suggests that urea adsorption onto biochar follows a multi-layer adsorption process. Finally, an integrated process is suggested: "Na-chabazite and Biochar adsorption → urea hydrolysis → struvite precipitation + ammonia stripping-acid scrubbing", ensuring efficient recovery of urea, NH4+, PO43-, and K+ from source-separated urine.

Interactive impacts of organic-inorganic modifiers on surface characteristics of Cu+-doped activated carbon for stable CO-adsorptive separation from CO2

Conventional Cu+-doped activated carbon (C) materials are problematic in carbon monoxide (CO)-selective adsorption from carbon dioxide (CO2) due to their CO2-friendly surface basicity and microporosity. In this study, boehmite (AlOOH) film modified-carbon composite (AlC) was hydrothermally synthesized to dope with 30 wt% Cu+ ions by the impregnation-calcination method. The functional hydroxyl groups of Boehmite behaved as metallic anchoring sites for better Cu+ ion dispersion, enhancing the CO adsorption uptake to 38.84 cm3/g at 25 °C and ∼ 100 kPa in isotherm analysis. Additionally, the improved Lewis acidity of AlC surface interface together with pore widening impact reduced the CO2 uptake to 14 cm3/g, around half that of Cu+-doped activated carbon, by undergoing Lewis acid-acid repelling interaction between boehmite film and CO2. However, to address rapid oxidation of Cu+ ions in the hygroscopic AlC structure, iron (II) chloride (FeCl2) surface modification on the Cu+-doped AlC composite created a Fe3+-Cu+ bimetallic interface with high Cu+ immobilization, enriching the CO adsorption stability to 92 % even after 30 day-air exposure. Noticeably, pre-complexation of FeCl2 with thiourea (NH2CSNH2) before its dispersion over the doped Cu+ ions led to distinct Cu+ stabilization mechanisms without bimetallic redox interaction. This involves developing auto-redoxable iron (II) sulfides as barrier coatings for Cu+ species against oxidation and raising the Cu2+ reducibility via cyanide-ligands of thiourea. These combined preservation effects for Cu+ ions ensured CO adsorption stability of 91 %, underlining higher CO adsorption uptake (39.38 cm3/g) and CO/CO2 selectivity (67.49 at 0.2 kPa and 3.09 at ∼ 100 kPa) than modification effects of boehmite and FeCl2.

Zwitterionic MOF-embedded alginate beads with polydopamine surface functionalization for efficient doxycycline removal: Optimization and mechanistic study

The adsorptive removal of amphoteric antibiotics like doxycycline (DOX) is a difficult task because of the electrostatic repulsion between these amphoteric molecules and adsorbents. For this purpose, a zwitter adsorbent was fabricated by incorporating zwitter ZIF-67/MIL-88A binary MOF into the matrix of alginate (Alg); in addition, the surface of the beads was modified by polydopamine (PDA). The batch experiments implied the super-high adsorption efficacy of ZIF-67/MIL-88A@Alg@PDA toward DOX attained 384.61 ± 5.08 mg/g at a neutral pH medium, 25 °C, and using 0.02 g. The isotherm analysis implied the physisorption of DOX onto ZIF-67/MIL-88A@Alg@PDA, while the kinetic analysis denoted the chemisorption of DOX. The results of XPS, Zeta potential, and Lab experiments identified the types of physical and chemical interactions between ZIF-67/MIL-88A@Alg@PDA and DOX. The durability of the ZIF-67/MIL-88A@Alg@PDA beads was inspected by the recycling test, clarifying that the DOX adsorption aptitude declined by 12.22 mg/g. In addition, the measured leaching concentrations of cobalt and iron from the leaching test were 0.008 and 0.098 mg/L. The ionic strength of ZIF-67/MIL-88A@Alg@PDA, implying an enhancement in the DOX removal (%) from 83.51 to 93.50 % by raising the NaCl concentration from 0.2 to 1.0 mol/L. Therefore, our study could provide a simple procedure to overcome the electrostatic repulsion that retard the adsorption process of the amphoteric drugs onto charged adsorbents with positive or negative charges. Additionally, this procedure could also generate an electrostatic interaction between the zwitter adsorbents and the amphoteric drugs at specific pH media when they are in a zwitterionic nature.