Multilayer Adsorption Research Articles

Nanoassemblies of Chitosan-Based Polyelectrolyte Complexes as Nucleic Acid Delivery Systems.

Nucleic acid delivery requires vectorization for protection from nucleases, preventing clearance by the reticuloendothelial system, and targeting to allow cellular uptake. Nanovectors meeting the above specifications should be safe for the patient, simple to manufacture, and display long-term stability. Our nanovectors were obtained via the green process of polyelectrolyte complexation, carried out at 25 °C in water at a low shear rate using chitosan (a polycationic biocompatible polysaccharide of specific molar mass and acetylation degree) and dextran sulfate as a polyanionic biocompatible polysaccharide. These complexes formed nanoassemblies of primary nanoparticles (20-35 nm) and maintained their colloidal stability for over 1 year at 25 °C. They could be steam sterilized, and a model nucleic acid could be either encapsulated or surface adsorbed. A targeting agent was finally bound to their surface. This work serves as a proof of concept of the suitability of chitosan-based polyelectrolyte complexes as nanovectors by sequential multilayered adsorption of various biomacromolecules.

Dynamic Change Characteristics and Main Controlling Factors of Pore Gas and Water in Tight Reservoir of Yan’an Gas Field in Ordos Basin

Tight sandstone gas has become an important field of natural gas development in China. The tight sandstone gas resources of Yan’an gas field in Ordos Basin have made great progress. However, due to the complex gas–water relationship, its exploration and development have been seriously restricted. The occurrence state of water molecules in tight reservoirs, the dynamic change characteristics of gas–water two-phase seepage and its main controlling factors are still unclear. In this paper, the water-occurrence state, gas–water two-phase fluid distribution and dynamic change characteristics of different types of tight reservoir rock samples in Yan’an gas field were studied by means of water vapor isothermal adsorption experiment and nuclear magnetic resonance methane flooding experiment, and the main controlling factors were discussed. The results show that water molecules in different types of tight reservoirs mainly occur in clay minerals and their main participation is in the formation of fractured and parallel plate pores. The adsorption characteristics of water molecules conform to the Dent model; that is, the adsorption is divided into single-layer adsorption, multi-layer adsorption and capillary condensation. In mudstone, limestone and fine sandstone, water mainly occurs in small-sized pores with a diameter of 0.001 μm–0.1 μm. The dynamic change characteristics of gas and water are not obvious and no longer change under 7 MPa displacement pressure, and the gas saturation is low. The gas–water dynamic change characteristics of conglomerate and medium-coarse sandstone are obvious and no longer change under 9 MPa displacement pressure. The gas saturation is high, and the water molecules mainly exist in large-sized pores with a diameter of 0.1 μm–10 μm. The development of organic matter in tight reservoir mudstone is not conducive to the occurrence of water molecules. Clay minerals are the main reason for the high water saturation of different types of tight reservoir rocks. Tight rock reservoirs with large pore size and low clay mineral content are more conducive to natural gas migration and occurrence, which is conducive to tight sandstone gas accumulation.

Phosphorous recovery from sewage effluent by vanadium-substituted composite synthesized via reverse coprecipitation route

MgFe2O4/MgO (S-sample) and a novel V-modified MgFe2O4/MgO (V-sample) nanocomposites were successfully synthesized using the reverse coprecipitation method and were carefully characterized by X-ray diffractometry, Infrared and 57Fe Mössbauer spectroscopies, magnetization, electron microscopy (both transmission and scanning) and surface area analysis to comprehend their structural, morphological, hyperfine and magnetic properties before and after P adsorptions. MgFe2O4 and V-modified MgFe2O4 phases (with 30 nm average in “diameter”) govern the nanocomposite magnetic properties and these phases are chemically stable in phosphate-rich effluents. 50 nm in size MgO phase is responsible for P adsorption, but it showed chemical corrosion, as suggested by surface analysis. Adsorption kinetic revealed that there are two controlling steps: film and intraparticle diffusion. The nanocomposite materials fitted better to the Freundlich isotherm model, indicating that the adsorption site distribution for P is heterogeneous, and a multilayer adsorption mechanism is favored. Multicycle reuse experiments with secondary sewage effluent were performed, and the adsorption capability of the V-sample over 3 consecutive adsorption cycles was 11 mg g−1, a value 30 % higher than that found for the S-sample. The desorption efficiency of the V-sample was about 97 %, while the S-sample reached 76 %. The V-substituted composite is a promising nanoadsorbent for water remediation process in phosphate-rich effluents and should be also tested in remediation of other contaminants.

Efficient removal of perfluorooctanoic acid using fluorinated ionic liquids and granular activated carbon

Perfluoroalkylated and polyfluoroalkylated substances (PFAS) are persistent and bioaccumulative compounds in the environment and the human body. Their presence in high concentrations brings devastating consequences to health. Nowadays, there is an urgent need to develop efficient and sustainable processes that mitigate the damage caused by PFAS to improve the life quality of individuals. In the present work, perfluorooctanoic acid (PFOA) extraction properties with fluorinated ionic liquids (FILs) in aqueous media were evaluated for the first time. The most promising FIL is [P44414] [C4F9SO3] obtaining uptake capacities up to 280 mg·g−1 in 72 h. To verify if this performance is competitive for the best materials used so far in the literature for PFAS removal, adsorption processes were carried out with granular activated carbon (GAC) obtaining adsorption capacities up to 666 mg·g−1 (best fitted with the pseudo-second-order kinetic model) with an equilibrium time of 48 h. Equilibrium assays showed maximum uptake capacities around 500 mg.g−1, and multilayer adsorption due to the best fit to the Freundlich model. Both materials (FILs and GAC1240W) can open new paths in PFAS removal processes from aqueous solutions. Taking advantage of the properties of each one of these compounds, new, more efficient, and sustainable processes can be optimised in the future.

Molybdenum disulfide anchored peanut shell biochar composite for efficient adsorption of Pb2+: Performance and mechanism

Heavy metal lead (Pb2+) contamination in water poses a serious threat to human health, and developing some effective strategies for the removal of Pb2+ is urgent. Herein, molybdenum disulfide (MoS2) anchored peanut shell biochar (BC) composite adsorbents were successfully prepared by hydrothermal method and applied for the adsorption of Pb2+. Among these composites, the MoS2/BC-3 composite displayed the best adsorption performance with the adsorption capacity of 232 mg·g−1 at 30 °C. The adsorption procedure followed the pseudo-secondary kinetics and Freundlich adsorption model, indicating that the adsorption process of Pb2+ over MoS2/BC-3 composite was chemical and multilayer adsorption. Moreover, Pb2+ was spontaneously adsorbed by MoS2/BC-3, and the adsorption capacity increased with the enhance of temperature. The main mechanisms involved in the adsorption of Pb2+ by MoS2/BC-3 composite were found to include electrostatic interaction and complexation interaction. In addition, the MoS2/BC-3 composite had a good stability, and the Pb2+ removal rate could still reach more than 80 % after 6 cycles of adsorption experiments. Meanwhile, the adsorbent demonstrated a strong ability to absorb common heavy metals including copper and cadmium, further confirming that the MoS2/BC-3 composite had a potential value.

Development and characterization of novel CS-ZnO-Alg polyelectrolyte complex for enhanced removal of Cd(II), Cu(II), and Ni(II) from simulated paint industrial wastewater

In this study, we developed and characterized a novel chitosan-alginate-based polyelectrolyte complex impregnated with zinc oxide nanoparticles (CS-ZnO-Alg PEC) for the enhanced removal of Cd(II), Cu(II), and Ni(II) from simulated paint industrial wastewater. The prepared PEC was characterized by X-ray Diffraction (XRD), Fourier-Transform Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS), X-ray Photoelectron Spectroscopy (XPS), Brunauer-Emmett-Teller (BET), and Thermogravimetric analysis/Differential Thermal Analysis (TGA/DTA). The equilibrium data for said metal ions was best appropriated by Freundlich isotherm with maximum adsorption capacity of 217.72 mg/g for Cd(II), 130.41 mg/g Cu(II), and 159.06 mg/g for Ni(II), illustrating the multilayer adsorption of metal ions on the heterogeneous surface sites of the adsorbent. The kinetics of all three metal ions adsorption process onto discussed PEC was consistent with pseudo-second-order model. The thermodynamics results illustrate exothermic and spontaneous processes for Cd(II) (ΔH° = −3.57 KJ/mol, ΔS° = 0.009 KJ/mol*K, ΔG° = −6.42 to −6.61 KJ/mol) and Cu(II) (ΔH° = −3.32 KJ/mol, ΔS° = 0.006 KJ/mol*K, ΔG° = −5.25 to −5.37 KJ/mol), and spontaneous but less favorable adsorption for Ni(II) (ΔH° = −0.82 KJ/mol, ΔS° = −0.001 KJ/mol*K, ΔG° = −0.39 to −0.36 KJ/mol). Notably, the PEC could be easily recycled and regenerated, maintaining adsorption efficiency after five cycles. Overall, the CS-ZnO-Alg PEC, due to its amphoteric nature, high adsorption efficiency, cost-effectiveness, excellent recyclability, and biodegradability, could be a promising adsorbent for paint industrial wastewater.

Adsorption performance and mechanism of a starch-stabilized ferromanganese binary oxide for the removal of phosphate

Effective removal of phosphate from water is essential for preventing the eutrophication and worsening of water quality. This study aims to enhance phosphate removal by synthesizing starch-stabilized ferromanganese binary oxide (FMBO-S), discover the factors, and investigate adsorption mechanisms. FMBO and FMBO-S properties were studied using Scanning Electron Microscopy, BET analysis, Polydispersity Index (PDI), Fourier Transform Infrared Spectroscopy, and X-ray Photoelectron Spectroscopy (XPS). After starch loading, the average pore diameter increased from 14.89 Å to 25.16 Å, and significantly increased the pore volume in the mesopore region. FMBO-S showed a PDI value below 0.5 indicating homogeneous size dispersity and demonstrated faster and higher adsorption capacity: 61.24 mg g−1 > 28.57 mg g−1. Both FMBO and FMBO-S adsorption data fit well with the pseudo-second-order and Freundlich models, indicating a chemisorption and multilayered adsorption process. The phosphate adsorption by FMBO was pH-dependent, suggesting electrostatic attraction as the dominant mechanism. For the FMBO-S, phosphate adsorption was favored in a wide pH range, despite the weaker electrostatic attraction as evident from the point of zero charge and zeta potential values, indicating ligand exchange as a main mechanism. Moreover, the XPS analysis shows a significant change in the proportion of Fe species for FMBO-S than FMBO after phosphate adsorption, indicating significant involvement of Fe. Meanwhile, phosphate adsorption was almost unaffected by the presence of Cl−, NO3−, and SO42− anions, whereas CO32− significantly reduced the adsorption capacity. This study revealed that FMBO-S could be a promising, low-cost adsorbent for phosphate removal and recovery from water.

Effectiveness of Activated Carbon from Jackfruit Skin for The Heavy Metal Lead (Pb) Adsorption Using The Langmuir and Freundlich Equations

<p><span lang="EN-US"><strong>ABSTRACT. </strong>Activated carbon is a commonly used medium for adsorption to combat environmental pollution in both water and air. It is produced from plant or plantation waste containing carbon. Jackfruit skin, often considered as plantation waste, contains lignocellulosic compounds and has the potential to be used as active carbon. Activated carbon from jackfruit skin has a good absorption capacity and can absorb heavy metal waste such as lead (Pb). A recent study aimed to evaluate the absorption effectiveness of active carbon from jackfruit skin. The process involved making activated carbon using the pyrolysis method, and then analyzing its lead absorption capacity in lead nitrate solution by varying the weight of the activated carbon (10g, 15g, 20g, 25g, 30g) and the adsorption time in minutes (40, 60, 80, 100, 120). The levels of absorbed lead on activated carbon were tested using Atomic Absorption Spectrophotometry (AAS) at a wavelength of 283.3 nm. The research findings indicate that the </span><span lang="EN">effectiveness of activated carbon absorption reaches 99%</span><span lang="EN-US">, and the appropriate equation model for the adsorption process is the Freundlich isotherm, indicating a multilayer adsorption process.</span></p><p><strong><span lang="EN-US">Keywords:</span></strong></p><p><span lang="EN-US">Adsorption Isotherm, Activated Carbon Jackfruit Skin, Lead (Pb)</span></p>

Effective removal of chromium by adsorption using Delonix regia bark derived activated carbon from aqueous solution: a sustainable approach.

This study introduces a new biosorbent derived from Delonix regia bark-activated carbon to efficiently remove Chromium Cr(VI) metal ions from aqueous systems. The biosorbent was synthesized from the bark powder of the plant species and chemically activated with phosphoric acid. The biosorbent was characterized using FTIR, SEM, and BET to determine its functional properties and structural morphology. The batch adsorption experiments examined the optimal conditions for Cr(VI) metal ion adsorption, identifying that the highest removal efficiency occurred at pH levels of 2. The ideal adsorbent dosage was determined to be 2.5g/L, with equilibrium achieved at a contact time of 60min at the optimal temperature of about 303K for a Cr(VI) metal ion concentration of 20mg/L. Various isotherm models were applied to the adsorption equilibrium values, revealing that the adsorbent had a maximum removal capacity of approximately 224.8mg/g for Cr(VI) metal ions. The adsorption process of Cr(VI) on the DAC biosorbent was best described by the Freundlich isotherm, indicating multilayer adsorption. The kinetic data fit well with the pseudo-second-order model. Thermodynamic parameters suggested that the adsorption process was spontaneous, exothermic, and feasible across different temperatures. Furthermore, the desorption studies showed that the DAC biosorbent can easily be rejuvenated and utilized several cycles with high adsorption capacity. These findings indicate that the developed adsorbent is environmentally friendly and effective for removing Cr(VI) from water systems.

Fe nanoparticle-functionalized ordered mesoporous carbon with tailored mesostructures and their applications in magnetic removal of Ag(i)

Abstract Fe nanoparticle-functionalized ordered mesoporous carbon (Fe0/OMC) was synthesized using triblock copolymers as templates and through solvent evaporation self-assembly, followed by a carbothermal reduction. Fe0/OMC had three microstructures of two-dimensional hexagonal (space group, p6mm, Fe0/OMC-1), body centered cubic (Im3̄m, Fe0/OMC-2), and face centered cubic (Fm3̄m, Fe0/OMC-3) which were controlled by simply adjusting the template. All Fe0/OMC displayed paramagnetic characteristics, with a maximum saturation magnetization of 50.1 emu·g−1. This high magnetization is advantageous for the swift extraction of the adsorbent from the solution following the adsorption process. Fe0/OMC was used as an adsorbent for the removal of silver ions (Ag(i)) from aqueous solutions, and the adsorption capacity of Fe0/OMC-1 was enhanced by the functionalization of Fe0. Adsorption property of Fe0/OMC-1 was significantly higher than that of Fe0/OMC-2 and Fe0/OMC-3, indicating that the long and straight ordered pore channels were more favorable for adsorption, and the adsorption capacity of Ag(i) on Fe0/OMC-1 was 233 mg·g−1. The adsorption process exhibited conformity with both the pseudo-second-order kinetic model and the Freundlich model, suggesting that the dominant mechanism of adsorption involved multilayer adsorption on heterogeneous surfaces.

Sustainable Processes of Biosorption of Pb(II) Ions from Synthetic Wastewater Using Waste Biomass from Mullein Leaves

The aim of this study is to evaluate mullein (Verbascum thapsus) as a cost-effective and sustainable adsorbent for the biosorption of Pb(II) ions from synthetic wastewater samples. Biosorption of mullein was investigated as a function of initial Pb(II) concentration (25–400 mg L−1), biosorbent dosage (2–20 g L−1), solution pH (3–7), and contact time (10–120 min). Mullein as a material with a high affinity for Pb(II) ions had a biosorption efficiency of 98.56% under the optimal conditions: pH 6, initial concentration of Pb(II) at 100 mg L−1, contact time of 90 min, and biosorbent dosage of 20 g L−1. The FTIR spectra of mullein leaves showed that oxygen-containing functional groups on the surface are potentially active sites for the biosorption of Pb(II) ions. EDS analysis and the pHPZC value confirmed the adsorption of Pb(II) ions at the active sites of the mullein. Kinetic and isotherm data enabled insights into the modes of Pb(II) biosorption on the mullein surface which were best explained with the pseudo-second-order kinetic model and the Freundlich adsorption isotherm. Biosorption occurs on the mullein surface via multilayer adsorption. The reusability of mullein showed that the native biosorbents can be reused five times, showing the economic and sustainable benefit of this low-cost biosorbent material.

Adsorption of Methylene Blue using Bottom Ash: Experimental Design, Isotherm Analysis, and Optimum Conditions

<p><span lang="EN-US" style="font-size:12.0pt"><span style="line-height:107%"><span style="font-family:"Times New Roman",serif"><span style="color:black">This study investigated the removal of methylene blue (MB) via adsorption using waste bottom ash.  The bottom ash, sourced from a waste storage site in the Çorlu district of Tekirdağ province, Thrace Region, was utilized as the adsorbent. The research examined the impact of several variables on MB removal, including bottom ash dosage, pH, contact time, and agitation speed. It was found that all parameters had a single-variable effect, while pH exhibited a quadratic effect on MB removal in a model-based analysis. The optimization of the model for maximum MB removal identified the optimal conditions as 0.978 g bottom ash dosage, pH 3, 15 minutes of adsorption time, and 50 rpm agitation speed. Under these conditions, the model predicted an MB removal efficiency of 71%, which was experimentally confirmed to be 72.5%. The adsorption process was found to fit with the Freundlich isotherm, indicating a multilayer adsorption mechanism on the heterogeneous surface of the adsorbent. This research not only highlights the feasibility of using bottom ash from coal combustion as an economical adsorbent for dye-contaminated wastewater but also underscores its potential to inform and inspire future studies on waste recycling and wastewater treatment. </span></span></span></span></p>

Highly Defective Zirconium-Based Metal-Organic Frameworks for the Efficient Adsorption and Detection of Sugar Phosphates in the Biological Sample.

Enrichment and quantification of sugar phosphates (SPx) in biological samples were of great significance in biological medicine. In this work, a series of zirconium-based metal-organic frameworks (MOFs) with different degrees of defects, namely, HP-UiO-66-NH2-X, were synthesized using acetic acid as a modulator and were utilized as high-capacity adsorbents for the adsorption of SPx in biological samples. The results indicated that the addition of acetic acid altered the morphology of HP-UiO-66-NH2-X, with corresponding changes in pore size (3.99-9.28 nm) and specific surface area (894.44-1142.50 m2·g-1). HP-UiO-66-NH2-10 showed the outstanding performance by achieving complete adsorption of all four SPx using only 80 μg of the adsorbent. The excellent adsorption efficiency of HP-UiO-66-NH2-10 was also obtained with a wide pH range and short adsorption time (10 min). Adsorption experiments demonstrated that the adsorption process involved chemical adsorption and multilayer adsorption. By utilizing X-ray photoelectron spectroscopy and density functional theory to explain the adsorption mechanism, it was found that various interactions (including coordination, hydrogen bonding, and electrostatic interactions) collectively contributed to the exceptional adsorption capability of HP-UiO-66-NH2-10. Those results indicated that the defect strategy not only increased the specific surface area and pore size, providing additional adsorption sites, but also reduced the adsorption energy between HP-UiO-66-NH2-10 and SPx. Moreover, HP-UiO-66-NH2-10 showed a low limit of detection (0.001-0.01 ng·mL-1), high precision (<13.77%), and accuracy (80.10-111.83%) in serum, liver, and cells, good stability, high selectivity (SPx/glucose, 1:100 molar ratio), and high adsorption capacity (292 mg·g-1 for SPx). The practical detection of SPx from human serum was also verified, prefiguring the great potentials of defective zirconium-based MOFs for the enrichment and detection of SPx in the biological medicine.

Enhanced Adsorption of Arsenate from Contaminated Waters by Magnesium-, Zinc- or Calcium-Modified Biochar—Modeling and Mechanisms

The adsorption of arsenate from wastewaters was investigated by applying Mg-, Zn- or Ca-modified nut residue biochar activated by nitrogen/steam. The parameters studied were the contact time, adsorbent dose, initial arsenate concentration and solution pH. The adsorption mechanism was investigated. Various analyses of the material before and after arsenate adsorption were carried out, and experimental data were simulated by applying two isotherm models. The results indicated that the maximum removal efficiency of arsenate was 29.4% at an initial concentration of 10 mg/L. The modification of biochar by Mg, Zn or Ca oxides increased the removal rate significantly, from 49.4% at 100 mg/L As5+ up to 8%, 97% and 97%, respectively. Zn-modified biochar presented an excellent performance for both low and high As5+ concentrations. All experimental data were accurately fitted by the Freundlich isotherm model (R2 = 0.94–0.97), confirming a multilayer adsorption mechanism. For a biochar dose of 2 g/L, the maximum capacity of adsorption was enhanced after Mg-, Zn- or Ca-modification from 12.4 mg/g to 35 mg/g, 50 mg/g and 49 mg/g, respectively. The potential mechanisms of adsorption were ligand exchange, chemical complexation, surface precipitation and electron coordination.

Assessment of carbonized himalayan chir pine biomass as an eco-friendly adsorbent for effective removal of industrial dyes

This study investigates the use of carbonized Himalayan Chir Pine Biomass, known as Chir Pine Activated Carbon (CPAC), as an eco-friendly and cost-effective adsorbent for efficient industrial dye removal, with a focus on environmental sustainability. By applying different additive treatments, four adsorbents (C1, C2, C3, and C4) were formulated. CPAC was synthesized through pyrolysis and characterized using various analytical techniques including FE-SEM, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The adsorption capacity of CPAC was evaluated using Malachite Green (MG) dye as a model contaminant. FE-SEM images revealed high porosity (~ 10 µm) and a high surface area (119.886 m2/g) as confirmed by BET testing. CPAC effectively removed MG dye within 30 min at a solution pH of 7. Langmuir and Freundlich isotherm models indicated both monolayer and multilayer adsorption, while kinetic models suggested chemisorption. The regeneration efficiency was assessed using 0.1 N HCl over five consecutive cycles, with C4 demonstrating a high regeneration tendency of 85% and only a 9% reduction in adsorption ability after the fifth cycle. The developed CPAC shows excellent potential for use in the textile, paper, and leather industries for industrial dye adsorption, contributing to the protection of aquatic ecosystems. Additionally, CPAC can be utilized in other water and air purification applications.

Preparation of MnO2 modified winter melon-derived biochar for enhanced adsorption of U(VI) from aqueous solution

Abstract This work synthesized MnO2 modified winter melon-derived biochar (MnO2@WBC) using potassium permanganate oxidation/hydrothermal method for uranium(VI) removal. The factors influencing uranium(VI) adsorption by MnO2@WBC, including pH, adsorbent dosage, time, temperature, and initial U(VI) concentration were explored. The material’s performance was characterized, and the underlying mechanism of U(VI) removal was analyzed using various techniques. The characterization results indicated that the MnO2@WBC exhibited excellent dispersibility, suggesting that MnO2 effectively prevented WBC aggregation and enhanced the reactive surface area, and providing more active sites that can effectively promote the complexation and adsorption of U(VI). The process suggested a dominant role for chemical adsorption. The Freundlich isotherm model demonstrated a high degree of alignment with the observed adsorption behavior, indicating a predominantly multilayer adsorption process. Thermodynamic studies indicated that adsorption was a spontaneous endothermic process. The XPS analysis demonstrated that the adsorption process was primarily due to the formation of stable complexes with C–O, Mn–O–H and C=O. The results demonstrated that MnO2@WBC effectively removed U(VI), achieving a maximum adsorption capacity of 240.86 mg g−1 at a pH of 5.0. These findings provided a theoretical basis for the treatment of wastewater contaminated with U(VI).

Adsorption mechanism of hexavalent chromium on electron beam-irradiated aged microplastics: Novel aging processes and environmental factors

Microplastics are widely present in the natural environment and exhibit a strong affinity for heavy metals in water, resulting in the formation of microplastics composite heavy metal pollutants. This study investigated the adsorption of heavy metals by electron beam-aged microplastics. For the first time, electron beam irradiation was employed to degrade polypropylene, demonstrating its ability to rapidly age microplastics and generate a substantial number of oxygen-containing functional groups on aged microplastics surface. Adsorption experiments revealed that the maximum adsorption equilibrium capacity of hexavalent chromium by aged microplastics reached 9.3 mg g−1. The adsorption process followed second-order kinetic model and Freundlich model, indicating that the main processes of heavy metal adsorption by aged microplastics are chemical adsorption and multilayer adsorption. The adsorption of heavy metals on aged microplastics primarily relies on the electrostatic and chelation effects of oxygen-containing functional groups. The study results demonstrate that environmental factors, such as pH, salinity, coexisting metal ions, humic acid, and water matrix, exert inhibitory effects on the adsorption of heavy metals by microplastics. Theoretical calculations confirm that the aging process of microplastics primarily relies on hydroxyl radicals breaking carbon chains and forming oxygen-containing functional groups on the surface. The results indicate that electron beam irradiation can simultaneously oxidize and degrade microplastics while reducing hexavalent chromium levels by approximately 90%, proposing a novel method for treating microplastics composite pollutants. Gas chromatography-mass spectrometry analysis reveals that electron beam irradiation can oxidatively degrade microplastics into esters, alcohols, and other small molecules. This study proposes an innovative and efficient approach to treat both microplastics composite heavy metal pollutants while elucidating the impact of environmental factors on the adsorption of heavy metals by electron beam-aged microplastics. The aim is to provide a theoretical basis and guidance for controlling microplastics composite pollution.

3D- printed modular spr platform integrated with ellipsometer for in-situ label-free optical sensing applications

The present work focuses on advancing optical sensing abilities through the instrumentation of Surface Plasmon Resonance Spectroscopy (SPR) with a commercial ellipsometer. This approach involves the incorporation of an in-house-built 3D-printed SPR module to circumvent the complexity of optical alignments with the ellipsometer. Currently, no commercially available SPR-enhanced Ellipsometry (SPRE) system exists, and previous systems are mostly custom-designed. Our work addresses this gap by introducing an in-house-built SPR module compatible with Ellipsometry and constructed using 3D printing technology. The 3D-printed SPR module is user-friendly, durable, lightweight, and cost-effective, incorporating a flow cell crucial for liquid media operation. This integrated tool provides a highly surface-sensitive, non-invasive, and label-free optical sensing platform. The developed SPR-Ellipsometry platform demonstrates excellent performance in detecting biochemical analytes and multilayer adsorption of poly-electrolytes. The bulk refractive index sensitivity measurement was performed to calibrate the Au sensor chip. The Wavelength (SPR mode), amplitude (Ψ), and phase interrogation (∆) exhibit bulk refractive index sensitivities of 3098 ± 177 nm/RIU, 835 ± 22 °/RIU and 5839 ± 229 °/RIU, respectively. We obtained the refractive index resolution around 1.712 × 10−7 RIU. Protein-protein (BSA/Anti-BSA) interactions were also conducted, achieving a detection limit of 3 pM for Anti-BSA. This work will significantly expand the functionality of SPRE sensors by offering enhanced sensitivity, rich information, and high precision, as well as opening avenues for more efficient and accessible optical sensing technologies. Moreover, the study establishes a foundational framework for researchers, shedding light on the potential of 3D printers in laboratories and expediting the development of cost-effective integrated sensing platforms.

Optimization and mechanistic insight of phenol removal using an effective green kaolin adsorbent through experimental and computational approaches

The discharge of phenols into the aquatic environment has detrimentally affected human health and the aquatic ecosystem. Hence, removing phenols from polluted water bodies has been a global concern. In this study, a natural and low-cost adsorbent, kaolin, was used to remove phenol from aqueous solutions. Experimental and computational approaches were applied to optimize the removal efficiency and provide mechanistic insight into the phenol removal process. Based on the response surface methodology findings, the optimum conditions were pH 1.6, 40 min, 50 mg/L, and 2 g with 92.19 % maximum percentage removal. The regeneration test shows that kaolin retained over 76.76 % of adsorption capacities. SEM and FESEM reveals the surface morphology and effectiveness of kaolin as phenol removal. The best fit for the Isotherm adsorption for the phenol on kaolin is Freundlich isotherm, which indicated multilayer adsorption. The hydroxyl group from phenol (-OH) and the siloxane group of kaolin (Si-O-Si) shifted, suggesting the presence of a hydrogen bond between kaolin and phenol during adsorption, as determined by one- and two-dimensional IR spectroscopy. Density functional theory calculations were used to support the experimental results by providing information on the Mulliken charge and electronic transition of the complex to improve understanding of the adsorption of phenol on kaolin. Based on the quantum theory of atoms in molecules analysis (QTAIM) and the reduced density gradient non-covalent interaction (RDG-NCI) technique, the chemical reaction occurring during the removal of phenol by kaolin was determined to occur through hydrogen bonding and classified as an intermediate type (∇2ρ(r) > 0 and H < 0). Further characterizations employing molecular electrostatic potential, global reactivity, and local reactivity descriptors were conducted to investigate the mechanism of the phenol adsorption on kaolin. The findings demonstrated that phenol functions as an electrophile while kaolin acts as a nucleophile during the formation of hydrogen bonds, where the interaction occurred between the O2 atom of kaolin (electron donor) and the H13 atom of phenol (electron acceptor).

Lanthanum-loaded geopolymer for phosphate removal from agricultural runoff

The removal of phosphate from agricultural runoff is of great importance to mitigate an overabundance of nutrients discharging into receiving water bodies, which are susceptible to eutrophication. In this study, a La-loaded geopolymer was produced by adding metakaolin within an alkaline medium, consisting of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH). The ratio of Na2SiO3:NaOH within the geopolymer slurry was manipulated to evaluate its effect on phosphate adsorption capacity. The 1.54 ratio yielded the highest adsorption capacity of 33.65 mg g−1. However, due to structural strength, safety, and economic considerations, the 2.0 ratio was used for the isotherm and kinetic adsorption testing. The La-loaded geopolymer exhibited higher phosphate removal in batch adsorption experiments at an acidic level (pH 4) and elevated temperature (40 °C). Moreover, ionic strength (3.5–20 mM) had a negligible impact on phosphate removal, indicating inner-sphere complexation as the main mechanism of adsorption. Additionally, bicarbonate and humic acid increased phosphate removal, whereas sulfate slightly decreased adsorption capacity. The La-loaded geopolymer was further evaluated using a synthetic agricultural solution, which yielded a Type III adsorption isotherm, demonstrating unrestricted multilayer phosphate adsorption. Results from this study verified the La-loaded geopolymer is a promising adsorbent for phosphate removal from agricultural runoff and underlined the importance of matrix effects on treatment performance.