Maximum Adsorption Amount Research Articles

Adsorption studies of methylene blue using mangosteen shell porous biochar as adsorbent

The biomass of mangosteen shells was utilized as a raw material to prepare activated carbon based on mangosteen shells through a two-step process of mixed alkali carbonization and activation. This study aimed to investigate the efficacy of the activated carbon in removing methylene blue. The optimum preparation conditions for the study are KOH : NaOH : MSC = 1 : 1 : 1 with a particle size of 80 mesh. The activated carbon exhibits a BET specific surface area of 1432.699 m2/g and a Langmuir maximum specific surface area of 2066.130 m2/g. It demonstrates excellent adsorption performance for methylene blue, with a maximum adsorption amount of 985.5 mg/g. Characterization of the activated carbon is conducted using various techniques including Scanning Electron Microscope, X-ray Diffraction Instrument (XRD), Raman Spectrometry (RMS), Fourier IR Spectrometry (FT-IR), XPS, and BET theory. The adsorption results were consistent with the Freundlich model and the pseudo-first-order kinetic model, indicating that the carbon material exhibits multilayer physical adsorption characteristics for methylene blue. The prepared material offers a large specific surface area, good environmental economics, and excellent adsorption performance, making it a promising choice for adsorption material preparation compared to other biomass activated carbons.

Enhanced cationic/anionic dyes removal in wastewater by green nanocomposites synthesized from acid-modified biomass and CuFe2O4 nanoparticles: Mechanism, Taguchi optimization and toxicity evaluation

This article addresses the nanoadsorption mechanisms of rhodamine B (RB), crystal violet (CV), and Congo red (CR) using acid-treated C.edulis (ATCE)/CuFe2O4 (ATCE@CuFe2O4) from an aqueous solution. The physical and chemical characterizations of nanobiomass were studied using different techniques. The specific surface areas of the ATCE and ATCE@CuFe2O4 composites were 15.88 and 337.81 m2/g, respectively, indicating a significant specific surface area of ​​the ATCE@CuFe2O4 nanocomposite. A number of functional groups were determined, which promote the binding of the dye to the adsorbent. The SEM also shows that the adsorbent has a homogeneous texture with deep voids and significant porosity, which likely explains the retention and binding of dye ions on the surface of the adsorbent. In fact, the Langmuir isotherm with a correlation coefficient of 99 % for CV, RB and CR, respectively, represents the most suitable model to explain the adsorption mechanism. The maximum adsorption amount is 666.6 mg/g for CV, 645.16 mg/g for RB and 434.71 mg/g for CR at 308 °K. The adsorption kinetic processes were predicted by the pseudo-second order kinetic model. The thermodynamic properties showed that the adsorption on ATCE@CuFe2O4 was possible and spontaneous. The ATCE@CuFe2O4 recycling and elimination CV, RB, and CR were 74.23 %, 72.75 %, and 67.84 %, respectively, after seven cycles. The design, modeling and optimization of the adsorption parameters were carried out using the Taguchi experimental design. The maximum removal efficiency of CV, RB and CR dyes in optimal operating conditions were 99.96, 98.29 and 97.76 %, respectively. Which at the optimal conditions of 1 g/L, 90 min, 20 mg/L, 298 °K, pH 10 for CV and RB dyes and 1 g/L, 90 min, 20 mg/L, 308 °K, pH 4 for CR. This research demonstrated the performance of ATCE@CuFe2O4 in bean seed germination test and its effectiveness in removing dyes from wastewater.

Boronate affinity metal–organic frameworks molecularly imprinted membranes with hierarchical porous channels for the selective separation of naringin

Naringin (NRG), known as an important natural flavoniod compounds, exhibits excellent phamaceutical value and clinical application prospect. However, the main obstacle to the isolation and purification of NRG is the low concentration and complexity of the extraction system. Herein, a new kind of hierarchical porous metal–organic frameworks (MOFs) based molecularly imprinted membranes (PBMMA-MIMs) for the specific separation of NRG. The prepared PBMMA-MIMs showed the fast adsorption kinetics (within 120 min). Moreover, the abundant boronic acid imprinted recognition sits and hydrophilic hierarchical porous MOFs improved the adsorption capacity (the maximum adsorption amounts 57.39 μmol/g) and exhibited selective NRG adsorption (imprinting factor 2.31) with efficiency over 91.69 % after seven adsorption–desorption cycles. In addition, the coarse NRG could be effectively extracted to a promising purity of 93.13 % via PBMMA-MIMs. This study provides new insights into the design molecularly imprinted membranes via environmentally friendly synthesis route for the preparation for enriching high-value flavoniods, achieving efficient purification rate of agricultural wastes for pollution control, and promoting the sustainable reuse in complex agricultural wastewater.

Concurrent removal of Fe(II), Cu(II), and Zn(II) cations from acid mine drainage by an industrial solid waste - steel slag: Behaviors and mechanisms

Acid mine drainage (AMD) contamination poses a severe environmental threat and is a significant risk to human health. There is an urgent need to develop environmentally sustainable and technically viable solutions for water contamination caused by heavy metals. In this study, steel slag (SS) was used as a secondary resource to concurrently remove Fe(II), Cu(II), and Zn(II) from AMD. Because of the loose and porous structure, abundant functional groups, fast sedimentation velocity, and excellent solid-liquid separation, SS showed exceptional removal performance for heavy metal ions. The adsorption kinetic data of Fe(II), Cu(II), and Zn(II) showed good regression with the pseudo-second-order model. Besides, the adsorption of Fe(II) by SS conformed to the Freundlich model, whereas the adsorption of Cu(II) and Zn(II) followed the Langmuir model, with the maximum adsorption amounts of Cu(II) and Zn(II) being 170.69 and 155.98 mg/g. Furthermore, competitive adsorption was observed among Fe (II), Cu (II), and Zn (II) in a multi-component system, with the adsorption priority being Fe (II) > Cu (II) > Zn (II). The removal mechanism of Fe(II), Cu(II), and Zn(II) in AMD by SS mainly includes electrostatic attraction, chemical precipitation, and surface complexation. Interestingly, the leached concentrations of Fe(II), Cu(II), and Zn(II) from the spent slag after calcination were all within the detection limit of the Chinese emission standard, demonstrating excellent environmental stability. Theoretically, this renders it a viable candidate for use as an additive in construction materials. Meaningfully, the work offers a practical approach for energy-efficient and eco-friendly heavy metal ions adsorption, and the secondary utilization of SS also contributes to the sustainable development of the steel industry. It is beneficial to implement the development concepts of clean production and efficient utilization of industrial solid waste.

Preparation of dandelion flower extract-based polyvinyl alcohol-chitosan-dandelion-CuNPs composite gel for efficient bacteriostatic and dye adsorption

A multifunctional composite gel with efficient bacteriostatic and dye adsorption properties was prepared using polyvinyl alcohol, chitosan, and soybean isolate protein as carriers, CuNPs prepared by green reduction of dandelion extract as bacteriostatic agent, and glutaraldehyde as cross-linking agent. The composite gel showed good inhibition capacity of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa with the diameter of inhibition zone of 27.0–28.3 mm by agar diffusion method. The composite gel antibacterial rate remained above 90 % after 14 days of preparation. After 6 times reuse of composite gel in water, the antibacterial rate remained above 90 %, proving its good stability and reusability. Adding dandelion extract and CuNPs greatly improved the gel antioxidant property, acquiring free radical scavenging rate at 95.6 %. This composite gel had good biocompatibility and adsorption performance, and the maximum adsorption amount of methylene blue and methyl orange was 40.36 mg/g and 41.81 mg/g, respectively. To sum up, the green composition of composite gel has good antimicrobial performance and high dye adsorption, which holds significant promising for treating the water body pollution and protecting the environment. To build cost-effective antibacterial and dye adsorption process on a large-scale, in-depth exploration about this topic is still needed to develop.

Quantum physisorption behavior of methane in nanoporous shales: Model and new mechanism

Methane adsorption in nanoporous shales plays a significant role in the storage and flow of shale gas. Although previously numerous theoretical models have been proposed to describe the gas adsorption behavior, how the potential energy distribution in nanopores impacts gas adsorption remains unclear. The mechanism of methane adsorption in extremely complicated nanopores is still no satisfactory explanation. In this study, a total of 28 shale samples located in the Paleozoic-Mesozoic strata from different sedimentary environments were utilized to investigate the nature and process of quantum physisorption of methane in nanoporous shales. It was suggested that methane confined within nanoscale space shows a quantum effect, and the physisorption behavior of methane may be the result of molecular energy level transition. Further, the quantum physisorption model was developed by considering the quantum potential energy distribution, maximum adsorption amount, gas temperature and gas pressure, which matches the isothermal adsorption data well for a various of shales under widely varied temperature and gas pressure condition. The adsorption amounts of methane with different energy levels can also be obtained by the model. Finally, a new mechanism of the methane quantum physisorption in nanoporous shales was proposed. Uneven spatial distribution of gas molecules and elementary space of gas adsorption are the intrinsic factors of controlling the quantum physisorption behavior. The former is mainly influenced by minimum potential unit (E0) and gas temperature, while the latter is represented by the parameter of maximum adsorption amount (nL) which impacted by specific surface area and gas temperature. Gas pressure only affects the molecule concentration with different energy levels, but does not affect the spatial distribution of molecule. E0 and nL vary in shales from different sedimentary environments, due to the difference in organic matter properties (TOC content and kerogen type), which indirectly impacts the methane physisorption behavior. These results are helpful to deeply understand the storage of methane in shales and improve the efficient development of shale gas. In addition, this study is expected to open a new research direction about the quantum physisorption of gas in nanoporous media.

Rapid and efficient carbon dioxide capture through benzene-1,4-diamine based hierarchical porous hyper-cross-linked polymers

Carbon dioxide (CO2) emission causes global warming which has been the greatest challenge for humanity since last decade. Herein, we developed nitrogen and phosphorus rich hyper cross-linked polymers for CO2 capture, designated as BDA-HCP-1 and BDA-HCP-2 (benzene-1,4-diamine based hyper cross-linked polymers) having BET surface area 294.5904 m2g-1 and 519.6918 m2g-1 respectively. The pore width range of BDA-HCP-1 and BDA-HCP-2 is 0–25 nm and 0–15 nm and pore volume of BDA-HCP-1 and BDA-HCP-2 is 0.01–0.18cm3/g and 0.01–0.25 cm3/g, respectively.Total pore volume, studied using DFT, is 0.20100 cm3/g for BDA-HCP-1 and 0.27973 cm3/g for BDA-HCP-2. BJH cumulative pore volume of BDA-HCP-1 is 0.113023 cm3/g and BDA-HCP-2 is 0.284733 cm3/g. The BDA-HCP-1and BDA-HCP-2 were synthesized by replacement of chlorines of hexachlorocyclophosphazenes (HCCP) and phosphorousdichlorophosphazenes (PDCP) with bezene-1,4-diamine to form linear and cyclic polyphosphazenes, which are later cross-linked through Friedal crafts reaction to form hyper cross-linked polymers. The maximum CO2 adsorption quantity of BDA-HCP-1 is 48.62 cm3/g (CO2 weight adsorbed 9.070 % with equilibrium time 8.16 min) at 273K/1 bar and 37.96 cm3/g (weight adsorbed 7.15 % with equilibrium time 8.25 min) at 298K/1 bar that gives adsorption capacity of 2.14 mmol/g and 1.69 mmol/g, respectively. Adsorption capacity of BDA-HCP-2 is 2.30 mmol/g and 2.13 mmol/g at 273 K/1 bar and 298 K/1 bar respectively. It is calculated from maximum CO2 adsorption quantity of 51.6 cm3/g (weight adsorbed 9.83 % with equilibrium time 11.4 min, at 273 K/1 bar) and 47.7 cm3/g (weight adsorbed 9.25 % with equilibrium time 8.45 min, at 298 K/1 bar) respectively. Both BDA-HCPs can be reused with minor loss in adsorption capacity (2 and 1 %), which makes them excellent candidates to use on industrial scale applications. Adsorption isotherm study (Langmuir, Freundlich, and Temkin) and Kinetics study (pseudo first order and pseudo second order) reveals that this study fit best for Freundlich isotherms and pseudo first order kinetic model for both BDA-HCPs. This research contributes valuable insights into the design of hyper cross-linked materials with high surface area, good pore volume, excellent thermal stability and promising gas adsorption capacities particularly for addressing environmental pollution challenges related to CO2 emissions.

Carbon-doped CuO nanoparticle-constructed single tube adsorbent for high efficient adsorption of Pb2+ at near room temperature

How to prepare adsorbents using economical, environmentally friendly and simple methods has become the focus of research. In this paper, silk cotton (SC) was used as a biomass template impregnated with copper nitrate solution and then calcined to prepare CuO-based adsorbent. Carbon-doped CuO (C/CuO-400) adsorbent was obtained under 400 °C air calcination calcination. It completely replicates the morphology of kapok and consists of uniformly smaller nanoparticles. The effects of different calcination temperatures, adsorption temperatures, adsorption times, adsorbent dosages and different concentrations on the adsorption of lead ions were investigated. The results showed that C/CuO-400 had a good adsorption effect on Pb2+, which was suitable for Pseudo second-order and Langmuir, and the maximum adsorption amount of Pb2+ was 588.24 mg/g with good Reusability. This environmentally friendly, economical and simple to operate biomass template prepared adsorbent of single tube C/CuO has good adsorption effect on lead ions, which is very meaningful and easy to promote the preparation of adsorbent.

One-step synthesis of superparamagnetic copper alginate gel microspheres (Cu2+-Alg@Fe3O4) using a compression nebulizer

For the application needs of histidine-rich protein separation, this study proposes to prepare a magnetic adsorbent enriched with copper ions and small particle size. Using a compression nebulizer, the magnetic + sodium alginate solution was broken into micrometer-sized droplets and cross-linked and cured with copper ion solution. The magnetic copper alginate microspheres (Cu2+-Alg@Fe3O4) were obtained with an average particle size of 7.1 μm, a magnetic saturation intensity of 36.9 emu·g−1, and a Cu2+ content of 149.2 mg·g−1.The adsorption equilibrium time of the Cu2+-Alg@Fe3O4 microspheres on bovine hemoglobin(BHb) was 90 min, and the maximum adsorption amount was 4318.5 mg·g−1. The Cu2+-Alg@Fe3O4 microspheres also showed stable and good adsorption performance in five cyclic adsorption experiments.

Preparation of eggshell-based materials and their adsorption performance on Fe(III) in water*

Abstract If there is too much trivalent iron in the body, it will disrupt the balance of osmotic pressure inside the body, and its heavy metal properties will denature proteins. Therefore, effective management of industrial pollution source wastewater is very important for environmental protection and human’s health. Calcium carbonate particles have a good ability to adsorb trivalent iron in wastewater. The aim is to prepare porous calcium carbonate by a template method using eggshell powder, hydrochloric acid, sodium stearate, and anhydrous sodium carbonate solution as the raw materials and research the adsorption properties of porous calcium carbonate to trivalent iron. Porous calcium carbonate was prepared by a template method using eggshell powder, hydrochloric acid, sodium stearate, and anhydrous sodium carbonate solution as the raw materials. The morphology and adsorptive properties of Fe (III) of the porous calcium carbonate were analyzed by scanning electron microscope (SEM) and UV-visible spectrophotometer (UV). The best value was found between different temperatures, time, and pH. The results verified that the maximum amount of adsorption was obtained when calcination was 400°C, pH was 5, time was 60 min, and the input amount was 20 mg. The adsorption of porous calcium carbonate to Fe (III) is chemical and has a better adsorption effect.

Removal of methylene blue from aqueous solutions by adsorption onto Carpobrotus edulis biomass

The aim of this work is to investigate the influence of an alkaline pretreatment of the Mediterranean plant Carpobrotus edulis on the adsorption capacity toward the dye methylene blue and to estimate the content of soluble organic matter that can be released into the aqueous solution by this biomaterial. The biomaterial used was characterized by SEM-EDX, SS, FT-IR, pHZ, COD and BOD5. Removal of methylene blue (MB) dye by this biomaterial was carried out and the effects of physicochemical factors such as initial pollutant concentration, adsorbent dose, contact time, pH and temperature were investigated. After adsorbent treatment, the soluble organic matter was reduced by 97%, 96%, and 96% for biological oxygen demand, chemical oxygen demand, and organic matter, respectively. Kinetics and equilibrium studies of MB adsorption on the bioadsorbents were fitted with a pseudo-second order kinetic model and a Langmuir model, respectively. The maximum adsorption amount of the modified C. edulis plant was 153.9 mg/g at 298°K. The thermodynamic parameters show that the adsorption process was possible and spontaneous in nature. The adsorption mechanism of MB on the surface of biomaterials was attributed to the electrostatic interaction and H-bonding. The prepared biomaterial (0.016 U$ per gram) was easily regenerated with aqueous HNO3 solution, with a slight decrease in adsorption capacity up to five cycles. The results of Taguchi experimental design and analysis of variance showed that contact time, adsorbent mass and initial concentration are the most important factors affecting the removal efficiency with a contribution of 43.91%, 32.68%, and 22.95%, respectively. The maximum removal capacity of MB dye in optimal operating conditions was 99.39%, which was obtained at the optimum conditions of m = 1 g, pH 4, T = 35 °C, Ci = 1000 mg/L, tc = 5 min. These results confirm previous results obtained with the batch system and show that this absorbent is also promising for the removal of cationic dyes from wastewater.

A recyclable biochar with ultrahigh absorption ability for efficient removal of tetracycline hydrochloride

In this study, a novel iron-doped biochar (Fe@C) with excellent adsorption capacity and strong magnetism was easily prepared by a simple one-step synthesis method to adsorb tetracycline hydrochloride (TCH) in water. The adsorption capacity of biochar prepared from different materials was investigated, and the results showed that the adsorption performance of cotton-based biochar for TCH was much higher than other materials. The effects of pyrolysis temperature, material ratio and pH on adsorption capacity were explored. The adsorption kinetics and isotherms of TCH removal were studied, from the fitted adsorption curves, it was shown that the prepared Fe@C had superior adsorption capacity, and the maximum adsorption amount could reach as high as 1492.4 mg/g at 45 °C. The strong magnetic property of Fe@C (94.65 emu/g) enabled it to be rapidly separated from the solution after adsorption. In addition, the obtained Fe@C exhibited good stability and reusability, it maintained a high adsorption capacity even after five times of reuse. The adsorption mechanism was investigated systematically, which was mainly collaborated by pore filling, electrostatic effect and π-π interaction. Overall, the Fe@C had ultrahigh adsorption capacity, easy separation and good reusability, showing great potential for the removal of THC from water.

The Characteristics of Adsorption of Di-n-Butyl Phthalate by Surface Sediment from the Three Gorges Reservoir.

Phthalic acid esters (PAEs), recognized as endocrine disruptors, are identified as predominant organic pollutants in the Three Gorges Reservoir (TGR). Di-n-butyl phthalate (DBP), a representative PAE, has been extensively studied for its sources, distribution and ecological risks. However, there are few studies on the adsorption of DBP by sediment from the TGR, and the adsorption characteristics of surface sediment on DBP are not clear. Therefore, based on the actual sediment contents and particle sizes in the TGR, the kinetics and isothermal adsorption characteristics of surface sediment on DBP were investigated in this study. The results showed that the equilibrium time was 120 min, the adsorption kinetics were more in line with the pseudo-second-order kinetic model, and the sediment in water from the Yangtze River exhibited a higher adsorption rate and maximum adsorption amount on DBP than that observed in deionized water. Additionally, a decrease in DBP adsorption was observed with increasing sediment content, while sediment particle size and specific surface area had a slight influence. Analysis using SEM, TGA and FTIR revealed that organic matter on the sediment surface significantly contributed to DBP adsorption. This study contributes valuable insights into the adsorption characteristics of DBP by the surface sediment from the TGR, providing a scientific foundation for understanding the migration and transformation of DBP in this critical reservoir in China.

Yolk-shell MOF-on-MOF hybrid solid-phase microextraction coatings for efficient enrichment and detection of pesticides: Structural regulation cause performance differences

Metal-organic frameworks (MOFs) based composites with different structure-activity relationships have been widely used in the field of organic pollutant adsorption and extraction. Here, two MOF-on-MOF composites with different structures (yolk-shell and core-shell) from homologous sources were prepared by a simple in-situ growth synthesis method and structural regulation. In order to verify the effect of composite structure on the extraction capacity, the adsorption performance of the yolk-shell structure (YS–NH2-UiO-66@CoZn-ZIF) and the core-shell structured (NH2-UiO-66@CoZn-ZIF) material were compared by using them as coating material of direct immersion solid-phase microextraction (DI-SPME) to enrich six pesticides in five matrices. The results showed that because of the unique hollow hierarchical structure, high specific surface area (930.68 m2 g−1), abundant and open active sites, and synergistic and complementary adsorption forces, YS-NH2-UiO-66@CoZn-ZIF composites had the maximum adsorption amount of 36.01–66.31 mg g−1 under the same experiment condition, which was 6.81%–34.26 % higher than that of NH2-UiO-66@CoZn-ZIF. In addition, the adsorption mechanism of the prepared materials was verified and elaborated through theoretical simulations and material characterization. Under the optimized conditions, the YS-NH2-UiO-66@CoZn-ZIF-coated SPME-HPLC-UV method had a wide linear range (0.241–500 μg L−1), a good linear correlation coefficient (R2 > 0.9988), a low detection limits (0.072–0.567 μg L−1, S/N = 3) and low quantification limits (0.241–1.891 μg L−1, S/N = 10). The relative standard deviations of individual fibers and different batches of fibers were 0.47–6.20 % and 0.22–2.48 %, respectively, and individual fibers could be recycled more than 104 times. This work provided a good synthetic route and comparative ideas for exploring the in-situ growth synthesis of yolk-shell composites with reasonable structure-activity relationships.

Effect and mechanism of coexistence of microplastics on arsenate adsorption capacity in water

Arsenic pollution control technology in water was important to ensure environmental health and quality safety of agricultural products. Therefore, the adsorption performance of three adsorbents for chitosan, sepiolite, and Zeolitic Imidazolate Framework-8 (ZIF-8) were investigated in arsenate contaminated water. The results revealed that the adsorption capacity of ZIF-8 was higher than that of chitosan and sepiolite. The analysis of adsorption isotherm models showed that the behavior of ZIF-8 was more consistent with the Langmuir model. Furthermore, the adsorption mechanisms of three adsorbents for arsenate were investigated by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The analysis of FTIR showed that ZIF-8 maintained the stability of the interaction with arsenate by forming As-O chemical bonds. However, the effect of chitosan and sepiolite with arsenate was mainly physical adsorption. The analysis of XPS showed that the absorption of ZIF-8 with arsenate involved metal sites and nitrogen through the characteristic peak and the change of the binding energy. Furthermore, the impact of microplastics as a widespread coexistence pollutant in the water on adsorbent performance was investigated. The results indicated that the adsorption capacity of ZIF-8 was almost not affected by microplastics. The maximum adsorption amount of arsenate was changed from 73.45 mg/g to 81.89 mg/g. However, the maximum adsorption amount of chitosan and sepiolite decreased by 31.4 % and 11.6 %, respectively. The analysis of FTIR and XPS revealed that ZIF-8 enhances arsenate adsorption by forming N-O-As bonds in the presence of microplastics. This study provides scientific evidence for the management of arsenate pollution in water bodies, especially in complex water bodies containing microplastics.

Hexagon MXene based heterojunction interface with high ion adsorption and electron transfer efficiency for soft-package potassium-ions aqueous supercapacitors

Potassium-ion hybrid capacitors (PIHC) are considered as ideal large-scale rechargeable energy storage devices due to their low-cost, high-power density and environmental protection. However, a low energy density is the main factor restricting the practical application of PIHC. The interface is formed on the surface of electrode material of PIHC through strong correlation to construct heterojunction, which can significantly improve the performance of ion energy storage. However, how to reveal the influence of the interfacial state of the heterojunction on the adsorption and electron transmission of energy storage ions at the atomic level is still one of the key scientific problems in this field. In this work, metal ion intercalation and microwave-assisted in-situ etching are used to construct the Hexagon MXene Ti3C2 heterojunction with TiOHO strong correlation. At the interface of heterojunction, TiOHO highway for electron transmission is developed to improve the rate performance of PIHC. Through experimental and theoretical calculation, the optimum adsorption position and maximum adsorption amount of potassium-ion at the single interface of heterojunction are obtained, and the specific energy density of PIHC is increased. This lays a foundation for the practical application of high-performance soft-package PIHC.

Novel granular bentonite-carbon sorbents: textural characterization, adsorption-desorption isotherm, kinetics, and cost estimation.

This research focuses on the synthesis of novel low-cost granular sorbents based on bentonite clay of the Navbahor deposit, dust fraction of Angren brown coal, and agricultural wastes such as straw and sawdust to meet the internal needs of the Republic of Uzbekistan. The impact of the initial mixture ingredients on the structural and textural properties of bentonite-coal sorbents (BCSs) has been studied using X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, optical microscopy, and nitrogen adsorption-desorption analysis. For determining the sorption capacity of BCSs, a standard model substance methylene blue (MB), was applied. It was revealed that the maximum adsorption amount of MB was 5.3 mg∙g-1 during 2 h of contact. Prolonging the contact time to 24 h allowed for more extensive diffusion of dye molecules into the sorbent's pores, increasing the adsorption capacity to 13 mg∙g-1. It was demonstrated that BCSs could be regenerated by strong oxidizing agents such as sulfuric acid and hydrogen peroxide, with sulfuric acid proving more effective. Regeneration fully restores sorption properties, particularly at low dye concentrations (up to 0.2 mg∙ml-1). Despite slight reductions in adsorption capacity over multiple regeneration cycles, the sorbents maintain their structural integrity and durability. It is shown that compared to imported expensive activated carbon, the gross profitability of the in-house production of such granular BCSs within the territory of Uzbekistan increases from 48 to 78%, while the net income increases almost three times.

Effect of polyelectrolyte structure on perchlorate adsorption performance by functionalized montmorillonite

Polyelectrolyte (with different unit structure or molecular weight) modified montmorillonite (PMt) was synthesized for perchlorate (ClO4-) removal. It was found polyelectrolytes were successfully loaded on montmorillonite (Mt), and the surface potential of most PMt changed from negative to positive. Polyelectrolyte desorption on Mt was < 10 % after 48 h. Poly(diallyldimethylammonium chloride) species modified montmorillonite (PDDAx-Mt) showed excellent adsorption performance for ClO4- with maximum adsorption amount over 2.78 mmol/g and equilibrium time within 10 min. The adsorption performance of PMt toward ClO4- followed this order: PDDAx-Mt > CH-Mt > PAM-Mt > PQ28-Mt. Moreover, PDDAx-Mt and CH-Mt showed a superior adsorption selectivity to ClO4- among competitive oxyanions in the quaternary-adsorbate system (ClO4- > PO43- > SO42- > NO3–). The enhanced ClO4- adsorption could be mainly attributed to the presence of anion exchange sites (−R4N+-Cl− or –NH3+-Cl−) provided by PDDA or CH, followed by electrostatic gravitation and weak hydrogen bonding interaction. Density functional theory (DFT) calculation revealed that ClO4- adsorbed on PMt is a process of electrons transferring from O atoms in ClO4- to H atoms on C in PDDA+ or N in CH+, PAM+ and PQ28+. The preparation method of PMt is simple with excellent adsorption performance and selectivity toward ClO4-, suggesting promising applications in anion wastewater treatment.

One step synthesis of a novel Co-doped UiO-66 adsorbent for superior adsorption of organic dyes from wastewater

Metal-organic frameworks (MOFs) is a promising material that can be used in many fields, including environmental remediation. In this work, a novel adsorbent was successfully prepared by doping the Co element into the framework of UiO-66 with an in-situ oil bath synthesis. This modification ensured that the materials retained relatively good crystallinity. The Co-doping process had a major impact on the particle size and morphology of the original MOFs. The CoUiO-2 exhibited larger surface area and pore size than pristine UiO-66. Accordingly, the maximum adsorption amount of malachite green (MG) on CoUiO-2 (628.93 mg/g) was significantly larger compared with UiO-66 (343.64 mg/g), which was due to more active adsorption sites. In addition, the CoUiO-2 also showed a superior adsorption capacity on rhodamine B (RhB) (1106.22 mg/g). The adsorption process was well described by both the pseudo-second order and Langmuir models, indicating it was dominated by chemisorption and the adsorbent had a homogeneous surface area for adsorption. Therefore, the CoUiO-2 material could be a promising adsorbent for wastewater treatment. This work can provide an important insight into the modification of MOF materials and identify further opportunities to promote the adsorption performance in environmental remediation.

Fabrication of nitrogen-doped carbon dots biomass composite hydrogel for adsorption of Cu (II) in wastewater or soil and DFT simulation for adsorption mechanism

With the increase of Cu (II) content, its bioaccumulation becomes a potential pollution to the environment. It is necessary to design an economical and efficient material to remove Cu (II) without causing other environmental hazards. A novel material of alginate composite bead (ALG@NCDs) was synthesized by embedding N-doped carbon dots into pure alginate bead for the adsorption of Cu (II) from wastewater and contaminated soil. The initial concentration, the amount of adsorbent, temperature, adsorption time, and pH value were optimized for the adsorption of Cu (II). According to the Langmuir isothermal adsorption model, the maximum adsorption amount of the material to Cu (II) was 152.44 mg/g. The results of selective adsorption showed that ALG@NCDs had higher affinity to Cu (II) than to Pb (II), Co (II), Ni (II), and Zn (II). After five adsorption-desorption experiment, adsorption capacity of the ALG@NCDs was kept 89% of the initial adsorption capacity. Its Cu (II) adsorption mechanism was studied by density functional theory calculations. In addition, the material could effectively adsorb Cu (II) and release the phytonutrient Ca (II) simultaneously when applied to actual wastewater and soil. The fabricated ALG@NCDs would be a promising material for the adsorption of Cu (II) from wastewater or soil.