Dubinin-Radushkevich Models Research Articles

A modified dubinin-radushkevich model describing the cryogenic adsorption of 4He on carbon materials

The 4He and 3He adsorption characteristics of porous materials serve as important references for designing and optimizing cryogenic components or systems, including adsorption pumps, helium adsorption refrigerators, and gas-gap heat switches. In this study, various types of activated carbon and carbon nanotubes were measured for their 4He adsorption characteristics in the range of 3–20 K and 1–18000 Pa. Parameters such as micropore volume and adsorption potential energy of porous materials were analyzed through Dubinin-Radushkevich (DR) model. A modified DR model describing the monolayer adsorption of 4He on different carbon-based adsorbents was developed in this study, greatly facilitating the design of adsorption systems. Further, the 4He adsorption model was applied to gas-gap heat switches, and a numerical model of the 4He gas-gap heat switch was established, which accurately predicts the actuation characteristics of several heat switches.

Polymeric resins containing modified starch as environmentally friendly adsorbents for dyes and metal ions removal from wastewater.

Effective removal of organic and inorganic impurities by adsorption technique requires the preparation of new materials characterized by low production costs, significant sorption capacity, and reduced toxicity, derived from natural and renewable sources. To address these challenges, new adsorbents have been developed in the form of polymer microspheres based on ethylene glycol dimethacrylate (EGDMA) and vinyl acetate (VA) (EGDMA/VA) containing starch (St) modified with boric acid (B) and dodecyl-S-thiuronium dodecylthioacetate (DiTDTA) for the removal of dyes: C.I. Basic Blue 3 (BB3) and C.I. Acid Green 16 (AG16) and heavy metal ions (M(II)): Cu(II), Ni(II), and Zn(II) from water and wastewater. The adsorbents were characterized by ATR/FT-IR, DSC, SEM, BET, EDS, and pHPZC methods. These analyses demonstrated the successful modification of microspheres and the increased thermal resistance resulting from the addition of the modified starch. The point of zero charge for EGDMA/VA was 7.75, and this value decreased with the addition of modified starch (pHPZC = 6.62 for EGDMA/VA-St/B and pHPZC = 5.42 for EGDMA/VA-St/DiTDTA). The largest specific surface areas (SBET) were observed for the EGDMA/VA microspheres (207m2/g), and SBET value slightly decreases with the modified starch addition (184 and 169m2/g) as a consquence of the pores stopping by the big starch molecules. The total pore volumes (Vtot) were found to be in the range from 0.227 to 0.233cm3/g. These materials can be classified as mesoporous, with an average pore diameter (W) of approximately 55Å (5.35-6.10nm). The SEM and EDS analyses indicated that the EGDMA/VA microspheres are globular in shape with well-defined edges and contain 73.06% of carbon and 26.94% of oxygen. The microspheres containing modified starch exhibited a loss of smoothness with more irregular shape. The adsorption efficiency of dyes and heavy metal ions depends on the phases contact time, initial adsorbate concentration and the presence of competing electrolytes and surfactants. The equilibrium data were better fitted by the Freundlich isotherm model than by the Langmuir, Temkin, and Dubinin-Radushkevich models. The highest experimental adsorption capacities were observed for the BB3 dye which were equal to 193mg/g, 190mg/g, and 194mg/g for EGDMA/VA, EGDMA/VA-St/B, EGDMA/VA-St/DiTDTA, respectively. The dyes and heavy metal ions were removed very rapidly and the time required to reach system equilibrium was below 20min for M(II), 40min for BB3, and 120min for AG16. 50% v/v methanol and its mixture with 1M HCl and NaCl for dyes and 1M HCl for M(II) desorbed these impurities efficiently.

Low temperature physical activation of raw charcoal for excellent dye adsorption kinetics

The current work illustrates the physical activation of raw charcoal to produce activated carbon (AC) at low temperatures (300 and 500 °C). Prepared ACs are tested for Methylene blue (MB) adsorption experiments at various adsorption conditions (e.g., pH, temperature) and discussed efficiency, kinetics, isotherm models, and adsorption mechanism to determine the optimal adsorption conditions for the removal of MB dye. The results show that the prepared ACs (AC1, AC2 at 300 and 500 °C) efficiently absorb MB and obtain removal efficiency of ∼100 and 83% in 1 h, respectively. When the pseudo-first-order and pseudo-second-order adsorption kinematic models are used to test the adsorption data, the result fits the pseudo-first-order model better. The Freundlich and Langmuir adsorption isotherms are employed to model the isotherm data to get the maximum adsorption capacity (MAC). The MAC for AC1 and AC2 is found to be 39.14 and 40.98 mg/g, respectively. Additionally, MB adsorption has been analyzed using the Temkin and Dubinin–Radushkevich isotherm models, along with the inter-particle diffusion model. The Dubinin–Radushkevich model suggests that MB adsorption is a physical absorption process. The Temkin model showed that the Temkin constant (B) values are positive indicating that the adsorption is exothermic. The inter-particle diffusion model revealed that AC2 displays greater adsorption kinetics consistency due to its larger pore diameter. The results reveal that the Langmuir model captured the data better, demonstrating that monolayer adsorption dominated the absorption process. Additionally, prepared ACs are examined for reuse, and exhibit three cycles of recyclability. As a result, ACs made from oak wood charcoal are an easy affordable way to get rid of MB dye.

A Sustainable Solution for the Adsorption of C.I. Direct Black 80, an Azoic Textile Dye with Plant Stems: Zygophyllum gaetulum in an Aqueous Solution.

The presence of pollutants in water sources, particularly dyes coming by way of the textile industry, represents a major challenge with far-reaching environmental consequences, including increased scarcity. This phenomenon endangers the health of living organisms and the natural system. Numerous biosorbents have been utilized for the removal of dyes from the textile industry. The aim of this study was to optimize discarded Zygophyllum gaetulum stems as constituting an untreated natural biosorbent for the efficient removal of C.I. Direct Black 80, an azo textile dye, from an aqueous solution, thus offering an ecological and low-cost alternative while recovering the waste for reuse. The biosorbent was subjected to a series of characterization analyses: scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), and infrared spectroscopy (IR) were employed to characterize the biosorbent. Additionally, the moisture and ash content of the plant stem were also examined. The absorption phenomenon was studied for several different parameters including the effect of the absorption time (0 to 360 min), the sorbent mass (3 to 40 g/L), the pH of the solution (3 to 11), the dye concentration (5 to 300 mg/L), and the pH of the zero-charge point (2-12). Thermodynamic studies and desorption studies were also carried out. The results showed that an increase in plant mass from 3 to 40 g/L resulted in a notable enhancement in dye adsorption rates, with an observed rise from 63.96% to 97.08%. The pH at the zero-charge point (pHpzc) was determined to be 7.12. The percentage of dye removal was found to be highest for pH values ≤ 7, with a subsequent decline in removal efficiency as the pH increased. Following an initial increase in the amount of adsorbed dye, equilibrium was reached within 2 h of contact. The kinetic parameters of adsorption were investigated using the pseudo-first-order, pseudo-second-order and Elovich models. The results indicated that the pseudo-first-order kinetic model was the most appropriate for the plant adsorbent. The isotherm parameters were determined using the Langmuir, Frendlich, Temkin, and Dubinin-Radushkevich models. The experimental data were more satisfactory and better fitted using the Langmuir model for the adsorption of dye on the plant. This study demonstrated that Zygophyllum gaetulum stems could be employed as an effective adsorbent for the removal of our organic dye from an aqueous solution.

Adsorption of Chromium (VI) and Lead (II) in Synthetic Solutions Using Tamarindus Indica Fruit Peel

The problem of water pollution persists and, in some cases, has been getting worse since many of the industries that are currently installed in developing countries do not comply with established standards. In order to reduce water pollution, various environmental standards have been established that aim to regulate the introduction of contaminating agents into water and, thereby, control the degree of alteration of the quality of the vital liquid. Adsorption allows minimizing the generation of toxic waste and the recovery of the metal. The objective of the work was to study the bioadsorption of Cr (VI) and Pb (II) using the dry peel of <i>Tamarindus indica</i>. We worked at different pH values and concentration levels. The determination of the chemical-physical parameters was carried out at the Empress Geominera Oriente. Adsorption isotherms were performed using the Langmuir, Freundlich and Dubinin-Radushkevich models, resulting in the maximum bioadsorption capacity of Cr (VI) and Pb (II) by biomass being 3.83 and 15.63 mg/g, respectively. reaching maximum removal percentages of 90.8%. The values of mean free energy of adsorption obtained from the Dubinin-Radushkevich model in Cr (VI) and Pb (II) were 10,000 kJ/mol, respectively, showing that, for these experimental conditions, the adsorption process is of a chemical nature.

Optimized Lithium(I) Recovery from Geothermal Brine of Germencik, Türkiye, Utilizing an Aminomethyl phosphonic Acid Chelating Resin

ABSTRACT This study investigates the performance of Lewatit TP 260 ion exchange resin for the efficient recovery of lithium (Li(I)) from geothermal water sourced from the Germencik Geothermal Power Plant in Türkiye. A series of batch sorption experiments were performed to evaluate the influence of key parameters, including resin dosage, solution pH, temperature, initial Li(I) concentration, and contact time, on the Li(I) recovery process. The optimal conditions were determined to be a resin dose of 0.5 g per 25 mL of geothermal water, pH in the range of 6–8, and a temperature of 25°C. Under these conditions, the resin achieved a maximum Li(I) recovery rate of 71% from the geothermal water. Sorption isotherms were further analyzed using the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) models. Among these, the Langmuir model provided the best fit (R² = 0.9841), suggesting a maximum sorption capacity (qm) of 4.31 mg/g. Continuous recovery experiments conducted in column mode confirmed the practical applicability of Lewatit TP 260, achieving a total sorption capacity of 0.41 mg Li(I)/mL resin. The findings exhibit the potential of this resin as a viable sorbent for sustainable Li(I) extraction from geothermal brines, supporting the development of green energy technologies and contributing to the circular economy.

The potential of Gd doping as a promising approach for enhancing the adsorption properties of nickel-cobalt ferrites.

The study shows that the addition of gadolinium ions has a significant impact on the structure, morphology, and adsorption properties of Ni-Co spinel ferrite that was synthesized by the sol-gel auto-combustion method. The research also indicates that the higher the Gd content, the greater the increase in the lattice parameter, which suggests that Gd3+ ions uniformly replaced the octahedral Fe3+ ions. The morphology and chemical composition of Gd-doped Ni-Co ferrites have been studied using SEM and EDS. Gd adding to the NiCoFe matrix increases the BET surface area by 50% (from 48 to 72 m2/g) and promotes the formation of mesopores with an average radius from 3.9 to 4.9nm. The pHPZC values of Gd-doped ferrites are in the range of 7.22-7.39, which means that the ferrite surface will acquire a positive charge at natural pH, so this will promote the adsorption of Congo red anionic dye through electrostatic interaction forces. Langmuir, Freundlich, and Dubinin-Radushkevich models were used to explain the mechanism of CR adsorption on the Ni0.5Co0.5GdxFe2-xO4 adsorbent surface. The ionic-covalent parameter has been estimated to describe the surface acid-base properties. Overall, this study highlights the potential of Gd3+ doping as a promising approach for enhancing the adsorption properties of nickel-cobalt ferrites.

Adsorption of dibenzothiophene sulfone using Fe3+ and Fe6+-impregnated clay adsorbents

In this study, the adsorption of dibenzothiophene sulfone (DBTO) was investigated using clay minerals as adsorbents. Raw bentonite (BR) and raw activated clay (ACR) were impregnated with Fe3+ and Fe6+, creating bentonite-Fe3+ (BF3), bentonite-Fe6+ (BF6), activated clay-Fe3+ (ACF3), and activated clay-Fe6+ (ACF6). The surface functional groups, surface morphology, and surface area of the raw and modified adsorbents were studied through Fourier transform infrared spectroscopy, a scanning electron microscope, and Brunauer, Emmett, and Teller analysis, respectively. Batch experiments on simulated oil were done to test the effect of adsorption time (0.5–24 h), adsorption dosage (0.3–1.5 g), and adsorption temperature (30–50 °C). The results of the experiments showed the suitability of the pseudo-second order kinetic model on the clay adsorbent and sulfone system. This suggests that chemisorption is the rate-limiting step of the reaction. Equilibrium isotherms indicated the adherence of DBTO onto BR and BF3 to the Freundlich model, implying the heterogeneous adsorption of the sulfones onto the adsorbents. The systems of DBTO with BF6, ACR, ACF3, and ACF6 showed a better fit with the Dubinin-Radushkevich model. This denotes that adsorption happens through the filling of sulfones of the micropores on the adsorbent. Lastly, thermodynamic studies revealed the endothermic and non-spontaneous nature of the clay adsorbents and sulfone systems. The experiments showed that the impregnation of Fe3+ and Fe6+ lowered the desulfurization ability of the adsorbents. This could be due to the iron ions being hard acids and the sulfones being soft bases, thus showing lower compatibility than the raw counterparts of the adsorbents. Comparison with related studies showed that the prepared adsorbents, namely BF3 (5.1 mg g−1) and BF6 (6.4 mg g−1), had a higher adsorption capacity than Ni2+-loaded activated carbon (4.9 mg g−1) and activated clay (4.1 mg g−1). The study shows that BR (7.2 mg g−1) is the best-performing adsorbent, which can be set as the direction for future research. This study is a step toward the commercialization of oxidative desulfurization methods.

Using natural antioxidant Rhubarb extracts in PVA/chitosan bio-adsorbent films for efficient removal of cationic and anionic dyes from polluted water

In this research, sustainable membrane films were developed for removal of cationic and anionic dyes from wastewater based on polyvinyl alcohol/chitosan (PVA/CS) incorporated with natural antioxidant Rhubarb dye (Rh) extracts. Rh dye was extracted from Rhubarb roots by a green method. Three different quantities of Rh dye extracts (i.e., 2.5, 5, and 10 %) were used to fabricate crosslinked PVA/CS films by solvent-casting approach. The fabricated films subjected to different techniques such as X-ray diffraction (XRD), scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM-EDX), dynamic mechanical analysis (DMA), as well as antioxidant activity. In all cases, the incorporation of Rh dye extracts inside the composite improved the crystallinity, biocompatibility, stress–strain properties, besides the DPPH scavenging activity reached 42.50 % for PVA/CS-10 % Rh membrane compared to PVA/CS blank (i.e., ∼ 2.10 %). Dyes adsorption including different cationic and anionic dyes implemented for all selected membranes. The data revealed that the membrane containing 10 % Rh dye was the optimum for removal of malachite green oxide (MG, 93 %) as cationic dye and methyl orange (MO, 95.70 %) as anionic dye. Moreover, the kinetics of the removal process exhibited that this process followed the Langmuir, Freundlich, Temkin, Dubinin-Radushkevich models, and the pseudo-1st order kinetic model, with an R2 of 0.998 and 0.943 for MG and MG, respectively. Whereas, the adsorption process corresponded to the Freundlich isotherm model, with coefficients R2 was of 0.989 and 0.988 for MO and MG, respectively. Other parameters including dye concentration, contacting time, pH media, and kinetic studies were also applied on PVA/CS-10 % Rh membrane.

A statistical optimization for almost-complete methylene blue biosorption by Gracilariabursa-pastoris

In this study, the dried biomass of four marine algae, namely Porphyra sp., Gracilaria bursa-pastoris, Undaria pinnatifida and Laminaria sp., were screened for their ability to remove methylene blue (MB) dye from aqueous solutions. Statistical approaches of the Plackett-Burman Design (PBD) and Box-Behnken Design (BBD) were applied to optimize different environmental conditions in order to achieve the maximum MB removal percentage by Gracilaria bursa-pastoris. The biosorbent was characterized before and after adsorption process using FTIR, XRD and SEM analysis. Additionally, isotherms, kinetics and thermodynamics studies were conducted to investigate the adsorption behavior of the adsorbent. The results showed that Gracilaria bursa-pastoris achieved the highest dye removal efficiency (98.5 %) compared to 96.5 %, 93.5 % and 93.9 % for Undaria pinnatifida, Porphyra sp. and Laminaria sp., respectively. PBD analysis revealed that the agitation speed, pH, and biomass dose were found to be the significant parameters affecting MB removal onto Gracilaria dried biomass. According to the BBD results, the maximum dye removal percentage (99.68 %) was obtained at agitation speed of 132 rpm, pH 7 and biomass dose of 7.5 g/L. FTIR, XRD and SEM analysis demonstrated the participation of several functional groups in the adsorption process and changes in the cell surface morphology of the adsorbent following the dye adsorption. The adsorption isotherms showed better fit to Freundlich model (R2 = 0.9891) than the Langmuir, Temkin, and Dubinin-Radushkevich models. The adsorption kinetics were best described by the pseudo-second-order model (R2 = 0.9999), suggesting the chemical interactions between dye ions and the algal biomass. The thermodynamic parameters indicated that the adsorption of MB onto Gracilaria dried biomass was spontaneous, feasible, endothermic and random. These results indicate that dried biomass of Gracilaria bursa-pastoris is an attractive, environmentally friendly, cheap and effective agent for MB dye removal from environmental discharges.

Equilibrium and kinetic modeling studies for copper and cadmium removal from aqueous solutions by ground nut husk

This study investigates the equilibrium and kinetics of copper and cadmium adsorption from aqueous solutions using groundnut husk. Characterization of the groundnut husk reveals various functional groups and a porous morphology. Isothermal studies were conducted, and different models were evaluated to fit the data. The Langmuir model exhibits the best fit for copper adsorption, while the Temkin and Dubinin–Radushkevich (DR) isotherm models show superior fitting for cadmium adsorption. Results suggest that physisorption significantly influences both cases, with mean sorption adsorption energy lower than 8000 J/mole. Error analysis reveals that the Freundlich and Temkin models demonstrate maximum adsorption capacity, with lower Chi-square (ꭓ2), Sum of Square Errors (SSE), and SAE compared to Langmuir and DR models. Additionally, intra-particle diffusion was analyzed using the Weber and Morris equation. Evaluation of model parameters indicates that cadmium demonstrates better nonlinear fitting of data compared to copper. FTIR and SEM analysis confirm the involvement of various functional groups in adsorption and reveal changes in surface distribution post-adsorption due to copper and cadmium presence.

Fabrication of Nanocellulose/Chitosan Nanocomposite Based on Loofah Sponge for Efficient Removal of Methylene Blue: Thermodynamic and Kinetic Investigations

AbstractWe established three nano-solid adsorbents: nanocellulose based on plant loofah sponge (NC), chitosan (CS), and nanocellulose/chitosan composite (CSC). These substances were employed as solid adsorbents to eliminate methylene blue (MB) dye from wastewater. Various characterization techniques were employed to investigate all the synthesized solid adsorbents, including TGA (thermogravimetric analysis), XRD (X-ray diffraction spectra), (BET) nitrogen gas adsorption-desorption, SEM (scanning electron microscope), TEM (transmission electron microscopy), FTIR (Fourier transform infrared) spectrometer, and zeta potential. According to our results, CSC showed greater thermal stability than LS and NC but lower than CS, mesoporous (2.012 nm), higher total pore volume (0.366 cm3. g− 1), specific surface area (639.3 m2. g− 1), and pHpzc of 7.22. The static adsorption of MB was well described by the Langmuir (R2 > 0.9872), Temkin (R2 > 0.9668), and Dubinin-Radushkevich (R2 > 0.9485) models. The composite of nanocellulose and chitosan exhibited the highest Langmuir adsorption capacity (301.20 mg. g− 1) at 47 °C after a 24 h shaking period at a dosage of 2 g. L− 1 as the adsorbent and pH of 7. The adsorption of MB by the fabricated solid materials fitted well with the linear PSO (R2 > 0.9806) and Elovich (R2 > 0.9574) kinetic model. The enthalpy, entropy, and free energy change for the adsorption of MB onto CSC were determined to be 47.11 kJ. mol− 1, 0.172 kJ. mol− 1. K− 1, and − 3.29 kJ. mol− 1, respectively at 20 °C. Thermodynamic investigation showed that MB adsorption is spontaneous, endothermic, favorable (0 < RL<1, 0.017–0.313), and physisorption (EDR < 8 kJ. mol− 1). Compared to the other eluents, nitric acid produced the highest desorption percentage (98.5%).

Olive leaf extract-assisted preparation of nanoferrite for adsorptive removal of cationic dye

In this work, magnetic Fe3O4 nanoparticles synthesized with olive leaf extract were used to investigate the adsorption of Basic violet 16 from aqueous solutions. The physicochemical characteristics of Fe3O4 nanoparticles were evaluated by DLS, zeta potential, XRD, FTIR SEM, EDX, N2 adsorption-desorption, TEM, and VSM analyses. Using DLS analysis, the average size of the Fe3O4 nanoparticles was found to be 231.2 nm. Zeta potential studies indicated that the synthesized nanoparticles were moderately stable, and zeta potential was calculated as −14.9 mV. According to TEM analysis, the synthesized nanoparticles ranged in size from 6.28 to 17.3 nm. The optimum parameters for the adsorption of basic violet 16 with Fe3O4 nanoparticles were determined as pH: 9.0, adsorbent dose: 0.8 g, contact time: 210 min, stirring speed: 250 rpm. Langmuir, Freundlich, Dubinin Radushkevich (D-R) and Temkin isotherm models were used to characterize the basic violet 16 sorption data onto Fe3O4 nanoparticles and it was seen that Basic violet 16 adsorption onto the Fe3O4 nanoparticles followed Langmuir isotherm model at all temperatures. The maximum adsorption capacity of Basic violet 16 with Fe3O4 nanoparticles was determined as 117.64 mg/g at 318 K. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to describe the adsorption kinetics at 298–318 K. The adsorption followed the pseudo-second-order kinetic model. Adsorption of Basic violet 16 onto Fe3O4 nanoparticles occurred spontaneously and endothermically. Characteristic peaks Fe3O4 nanoparticles were visible in the XRD analysis. The SBET surface area dropped from 110.42 m2/g to 91.27 m2/g after dye adsorption. Peaks in the FTIR analysis showed that Basic violet 16 had been successfully adsorbed on Fe3O4 nanoparticles.

Performance and mechanism of phytic acid-modified mesoporous tobermorite for U(VI) adsorption in water

Tobermorite (TOB) was first prepared with waste fly ash and calcium carbide slag by the hydrothermal method, and then TOB was subjected to thermal activation, hydrochloric acid acidification, and phytic acid modification to synthesize phytic acid-modified mesoporous tobermorite (P-STOB). The adsorption results showed that the maximum adsorption ratio of U(VI) by P-STOB could achieve 99.17 %, significantly higher than that of TOB (79.20 %). Moreover, under conditions of pH=5, T=303 K, and an initial U(VI) concentration of 10 mg/L, the theoretical uptake capacity for U(VI) by P-STOB was 176.66 mg/g. Pseudo-second-order and Langmuir isotherm adsorption models fit the adsorption process well, which indicated that the adsorption process was mainly chemical adsorption and primarily monolayer adsorption. Thermodynamic parameters revealed that the U(VI) adsorption was an endothermic and spontaneous process. The Dubinin-Radushkevich model suggests that the adsorption mechanism is surface chemical complexation. Even after five cycles, the U(VI) removal ratio remained above 74.63 %. Characterizations using SEM, EDS, XRD, BET, XPS and FT-IR confirmed the successful introduction of phytic acid onto the surface of P-STOB. The main mechanism of the adsorbent's interaction with U(VI) is the coordination between P-O and U(VI), the surface complexation between -OH and U(VI), and the electrostatic gravitational force between ions.

Revolutionizing dye removal from wastewater using low-cost natural material

The contamination of wastewater by textile dyes has emerged as a significant and pressing environmental concern that requires immediate attention and the development of inventive solutions. One highly effective technique for addressing this issue involves using adsorption processes with nanoparticles for dye removal. To address this challenge, white stone powder (WSP) and calcined white stone powder (CWSP) were prepared for their potential in adsorbing and removing dyes from wastewater. The effect of pH, dosage, contact time, initial dye concentrations, and temperature were optimized during the present study. Furthermore, the equilibrium data for the WSP was subjected to rigorous analysis using multiple isothermal models, including the Freundlich, Langmuir, Dubinin Radushkevich, Harkin Jura, and Temkin models. A comparison of calculated and experimental uptake capacities and higher values of the correlation coefficient indicated that the Freundlich model fited better than the other models. In addition to the isothermal modeling, the morphology of the adsorbent materials was examined. The dye uptake capacity (mg/g) of white stone powder was 72.24 which increased up to 92.56 after calcination. This research work highlighted the potential of the calcined WSP as a cost-effective and efficient alternative for removing dyes from wastewater, presenting a promising solution to this pressing environmental issue.

Preparation and application of cattail residue-based magnetic cellulose composites for tetracycline antibiotics adsorption

Tetracycline antibiotics (TCs) are widely present in wastewater and surface water due to their extensive use. Removal of TCs from water is urgent. In this study, magnetic cellulose (MC) composites were prepared from cattail residues to adsorb oxytetracycline hydrochloride (OTC·HCl), chlortetracycline hydrochloride (CTC·HCl), and tetracycline hydrochloride (TC·HCl) from water. The influence of Fe3O4 content on the antibiotics removal was studied. The synthesized MC composites were characterized using FTIR, XPS, zeta potential, SEM, and XRD. Adsorption mechanisms and characteristics were explored using classic isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models) and common kinetic models (pseudo-first-order, pseudo-second-order, Elovich and Intraparticle diffusion models). Optimum adsorption capacity was achieved by MC2–1 (mass ratio of cellulose to Fe3O4 was 2:1), with a larger specific surface area (18.24 m2 g−1) and mesoporous structure. The adsorption processes were well described by the pseudo-second-order and Langmuir models. MC2–1 demonstrated maximum adsorption capacities of CTC·HCl (194.29 mg g−1), OTC·HCl (168.25 mg g−1), and TC·HCl (41.10 mg g−1). The results of models fitting and characterizations of the MC composites before and after the adsorption processes revealed that the main adsorption mechanisms were pore filling, hydrogen bonding, electrostatic interactions, and metal complexation. This study proposes a practical approach for utilizing wetland plant residues as an effective adsorbent for tetracycline antibiotics removal.

Sodium alginate-encapsulated nano-iron oxide coupled with copper-based MOFs (Cu-BTC@Alg/Fe3O4): Versatile composites for eco-friendly and effective elimination of Rhodamine B dye in wastewater purification

This study explores the effectiveness of Alginate-coated nano‑iron oxide combined with copper-based MOFs (Cu-BTC@Alg/Fe3O4) composites for the sustainable and efficient removal of Rhodamine B (RhB) dye from wastewater through adsorption and photocatalysis. Utilizing various characterization techniques such as FTIR, XRD, SEM, and TEM, we confirmed the optimal synthesis of this composite. The composites exhibit a significant surface area of approximately 160 m2 g−1, as revealed by BET analysis, resulting in an impressive adsorption capacity of 200 mg g−1 and a removal efficiency of 97 %. Moreover, their photocatalytic activity is highly effective, producing environmentally friendly degradation byproducts, thus underlining the sustainability of Cu-BTC@Alg/Fe3O4 composites in dye removal applications. Our investigation delves into kinetics and thermodynamics, revealing a complex adsorption mechanism influenced by both chemisorption and physisorption. Notably, the adsorption kinetics indicate equilibrium attainment within 100 min across all initial concentrations, with the pseudo-second-order kinetic model fitting the data best (R2 ≈ 0.999). Furthermore, adsorption isotherm models, including Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich, elucidate the adsorption behavior, with the Temkin and Dubinin-Radushkevich models showing superior accuracy compared to the Langmuir model (R2 ≈ 0.98 and R2 ≈ 0.96, respectively). Additionally, thermodynamic analysis reveals a negative Gibbs free energy value (−6.40 kJ mol−1), indicating the spontaneity of the adsorption process, along with positive enthalpy (+24.3 kJ mol−1) and entropy (+82.06 kJ mol−1 K) values, suggesting an endothermic and disorderly process at the interface. Our comprehensive investigation provides insights into the optimal conditions for RhB adsorption onto Cu-BTC@Alg/Fe3O4 composites, highlighting their potential in wastewater treatment applications.

Facile and economic preparation of graphene hydrothermal nanocomposite from sunflower waste: Kinetics, isotherms and thermodynamics for Cd(II) and Pb(II) removal from water

Keeping the need for good water quality and the demand of climatic issues, the sunflower waste was converted into graphene hydrothermal nanocomposite absorbents for the removal of toxic Cd(II) and Pb(II) metal ions from water. The graphene composite materials were studied by scanning (SEM) and transmission electron microscopy (TEM), XRD analysis, TG and DSC, Raman and IR spectroscopy. According to SEM and TEM analysis, the decarbonized materials had a disordered structure with amorphous carbon with a small pore content. During the carbonization process, the pores space was opened due to the removal of amorphous organic matter and the formation of defects; providing a significant number of meso- and micropores. The prepared graphene composite showed 133.33 and 222.22 mg/g Langmuir adsorption of Cd(II) and Pb(II) at pH 6.0, dose 0.33 g/30 mL, initial concentration 300 mg/L, time 30 min and at 45 °C temperature using hydrothermal nanocomposite HTC/graphene oxide absorbent. The obtained results followed the sorption of heavy metal ions in a mixed-diffusion mode with the contribution of a second-order reaction between the active center of the sorbent and the metal ions. The Temkin and Dubinin-Radushkevich model’s parameters and thermodynamic results confirmed endothermic physical interactions among adsorbent and metal ions. This paper is highly useful for managing sunflower waste and purifying water; leading to the present demand for clean water and climatic issues. The production of the effective low-cost nanocomposite using green synthesis technologies (hydrothermal carbonization of raw materials) is highly useful for the removal of Cd(II) and Pb(II) toxic metal ions from water.

Efficient capture performance and mechanism of thiadiazole-functionalized covalent organic framework for Pb(II) ion

Covalent organic frameworks (COFs) are very promising adsorbent developed during recent years. Here, a COFs adsorbent (COF@HPLC) for efficient adsorption of lead is designed by post-modification. The adsorption properties were studied by batch adsorption. It is shown that pH 4 is the optimum value for the adsorption of Pb(II) by COF@HPLC. When the temperature is 25 °C, the maximum adsorption capacity of COF@HPLC reaches 251.37 mg/g. The fitting results of adsorption isotherm indicate that the process is a non-uniform adsorption in a single molecular layer. The activation energy fitted by the Dubinin-Radushkevich model are 16.22 kJ/mol, 21.32 kJ/mol, 18.87 kJ/mol and 16.67 kJ/mol, showing that Pb(II) adsorption by COF@HPLC is a chemical reaction. Kinetic studies show also that Pb(II) adsorption is a chemically controlled process. Thermodynamic shows that the adsorption is a spontaneously exothermic process. Finally, COF@HPLC has good adsorption selectivity and reusability. The adsorption mechanism of Pb(II) by COF@HPLC was the electrostatic and chelating interaction between functional groups containing sulphide and nitrogen and Pb(II) based on the zeta potential, XPS and DFT analyses. This work offers guidance toward the design and preparation of functional adsorbents for the treatment and removal of Pb(II).

Analysis of the Sorption Properties of Molecularly Imprinted Polymers as Materials for Potential Monitoring of the Amount of Amoxicillin in an Aqueous Environment

ABSTRACT This work describes a procedure for obtaining molecularly imprinted polymers (MIPs) toward amoxicillin based on methyl methacrylate. To characterize the polymers synthetized, physicochemical and sorption properties were analyzed. The influence of the main parameters on the adsorption efficiency was investigated (the monomers composition of materials, contact time, initial concentration, and regeneration conditions). The adsorption isotherms were fitted by Freundlich, Langmuir, and Dubinin–Radushkevich models. Pseudo-first-order, pseudo-second-order, intraparticle diffusion, and second Fick’s law models were used to fit the kinetic data. Molecularly imprinted polymer which was obtained using 5 wt.% of amoxicillin in relation to the monomers, characterized by the highest sorption value of 4.8 mg/g. This polymer showed selective properties in competition with gentamicin and norfloxacin. Furthermore, in the case of testing imprinted polymers in real samples, materials with an imprint were characterized by higher sorption values compared to those without an imprint (3.27 and 2.02 mg/g, respectively). For the first time, for this type of MIP, we conducted research for regenerating. Water solutions with pH 3 or 9, 1% acetic acid, and ethanol were tested as regeneration solutions. Molecularly imprinted polymer regeneration for the most effective regeneration solution was carried out on SPE columns, allowing a 94% cleaning of the sorption material.