Freundlich Isotherm Research Articles

Assessing the Role of Soil Amendments on the Sorption-Desorption Behavior of Glufosinate-Ammonium Herbicide in Soils: Kinetic, Isothermal and Thermodynamic Investigations

ABSTRACT This study compared the sorption-desorption behavior of glufosinate-ammonium herbicide in three soils (S1, S2, S3) and these soils amended with farmyard manure (S1 M, S2 M, S3 M) and bentonite clay (S1C, S2C, S3C) at 288 K, 298K and 308 K. Sorption-desorption kinetics was studied by pseudo first, pseudo second, elovich and intraparticle diffusion models and isotherms by Freundlich, Langmuir, Temkin, SIPS and Dubinin-Radushkevich (D-R) equations. The kinetic data were best explained by Pseudo-second order and isothermal data with Freundlich model with higher correlation regression coefficients, R2 values. The results indicated that the addition of farmyard manure and clay enhanced the adsorption capacity of soils, with higher adsorption by farmyard manure as confirmed from higher Kd (9.1–16. 2 in Soil III > 7.4–12.1 in Soil II > 4.8–10.3 in Soil I) and Kf values (Soil III (9.48–13.12) > Soil II (8.17–11.50) > Soil I (5.42–10.36) in following order Soil III > Soil II > I. With increase in temperature adsorption decreased, due to weak interactions as indicated by decrease in Kd and Kf values. Desorption results indicated more retention of glufosinate-ammonium at low temperature. The sorption desorption coefficients values (Kfads< Kfdes) and strengths of adsorption/desorption (1/nads <1/ndes) indicated positive hysteresis. The negative ΔGo in the range −3.99 to −5.58 KJ/mol in Soil I, −4.99 to −5.98 in Soil II and −5.66 to − 6.66 in Soil III and ΔH° values in the range −6.96 to −10.26 indicated spontaneous and exothermic nature of sorption process. The risks of water bodies contamination in terms of groundwater ubiquity score, in the range 0.79–1.20, classify it as a non-leacher pesticide; therefore, do not cause potential harm to ground-water. The results indicated that the sorption-desorption was significantly affected by organic carbon, clay and temperature, therefore their addition can be utilized as suitable alternative to reduce environmental contamination by pesticides.

Preparation of MOEAMCl and MAAm Based Hydrogels and Effective Use in Anionic Dye Adsorption

ABSTRACTIn this study, hydrogels based on [2‐(Methacryloyloxy)ethyl]trimethylammonium chloride (MOEAMCl) and methacrylamide (MAAm) were synthesized for the removal of anionic dyes from aqueous solutions. Following detailed characterization, the use of hydrogels for methyl orange (MO) adsorption was investigated. Hydrogels prepared at MOEAMCl‐MAAm monomer feed ratios of 75:25 and 50:50 (HD‐2 and HD‐3) were found to be effective in MO removal. The optimal pH for MO adsorption was determined to be 9, the adsorption time 6 h, and the amount of adsorbent 0.1 g. Under optimal adsorption conditions, dye removal at an MO concentration of 1000 ppm was 89.4% and 90.9% for HD‐2 and HD‐3 hydrogels, respectively, with adsorption capacities of 950 and 994 mg/g. It was observed that MO adsorption on both hydrogels decreased with increasing adsorbent amount and temperature, but was almost unaffected by the medium matrix. Additionally, the Freundlich isotherm was found to be the appropriate isotherm model, and kinetic results indicated that the HD‐3 hydrogel fit all examined kinetic models better than HD‐2. In conclusion, it was determined that these adsorbents could be efficiently used for anionic dye removal.

Removal of hexavalent chromium from aqueous solutions using nano-Fe3O4/waste banana peel/alginate hydrogel biobeads as adsorbent

Abstract In this study, the removal of Cr(VI), known as one of the most dangerous heavy metal pollutants, was investigated by adsorption method using magnetic alginate biopolymer-supported banana peel composite beads (MAB), which were synthesized for the first time. Using plant waste for this composite synthesis is both important in terms of utilization of plant waste and more environmentally friendly. Optimum conditions were determined by examining the parameters of concentration (10–300 ppm), adsorbent dose (1–8 g/L), mixing time (5–360 min), pH (2–8), and temperature (25–55 °C). Characterization of this new synthesized composite adsorbent, FTIR, XRD, SEM, and EDX mapping measurements were performed. The experimentally found adsorption data were modeled by applying Freundlich, Langmuir, Scharthard, Temkin, and D-R isotherm models, and isotherm constants were calculated. The adsorption data on MAB are more compatible with the Langmuir and Freundlich isotherm. In the shaking-batch system at 25 °C and pH = 2, the maximum adsorption capacity of the composite was calculated as 370.4 mg/g. Adsorption kinetics were found to be suitable for pseudo-second-order. Thermodynamic studies were realized to evaluate thermal changes of the adsorption process, and desorption processes were realized to determine the regeneration times of MAB. The temperature studies showed that adsorption capacity increased with increasing temperature, showing that the system was endothermic. As a result, it has been shown that MAB can be used as an efficient biocomposite adsorbent for the removal and recovery of Cr (VI) ions from aqueous media. Graphical Abstract

Azo dye adsorption on ZrO2 and natural organic material doped ZrO2

Natural wastes and inorganic adsorbents are used for the removal of diazo dye Congo red (CR), which causes water pollution and is a carcinogen, from wastewater. Organic waste olive pulp (ZK), inorganic ZrO2 (Zr) and three different weight percent ZK/Zr (organic/inorganic) binary adsorbent systems prepared by ball-milling method were investigated for the effective removal of CR from wastewater. Characterization of both single and binary adsorbent systems were carried out by ATR/FTIR and SEM. According to the Langmuir isotherm, qmax values for ZK, Zr, 25ZK-75Zr, 50ZK-50Zr and 75ZK-25Zr at 45 °C were 588 mgg-1, 13 mgg-1, 46 mgg-1, 65 mgg-1 and 84 mgg-1, respectively. According to Frumkin-Fowler–Guggenheim and Temkin isotherms, the adsorption heat was found to be exothermic for ZK and 75ZK-25Zr at all three temperatures, while it was found to be endothermic for Zr, 25ZK-75Zr and 50ZK-50Zr. It was observed that the ΔG° values calculated from the thermodynamic data were consistent with the values in the Flory-Huggings isotherm. According to the kinetic data, it was observed that all adsorbents except ZK obeyed the pseudo-first-order rate equation. It was shown by error calculations that the experimental data obeyed the Langmuir or Freundlich isotherms better. It was observed that a new and effective organic/inorganic adsorbent system could be obtained by adding ZK to ZrO2 for the removal of Congo red (CR) from water.

Rapid adsorption of industrial cationic dye pollutant using base-activated rice straw biochar: performance, isotherm, kinetic and thermodynamic evaluation

This work intends to effectively remove methylene blue (MB) dye from wastewater using an agricultural waste-derived sorbent made from pyrolyzing rice straw to generate biochar. This is done while keeping the sustainability idea in mind and tackling the crises arising from environmental contamination with dyes. The physicochemical scrutinization of the non-activated and the base-activated biochar materials showed that the materials have promising textural properties and surface functionalization, leading to high and fast capability to retrieve MB from aqueous solutions in alkaline conditions. The adsorption equilibrium for all the biochar was reached within a time span of 15 min, but 90 percent of the dye removed at equilibrium was already eliminated in less than 5 min. The behaviour of the equilibrium adsorption for the biochar materials was thoroughly assessed using Langmuir and Freundlich adsorption isotherms. Interestingly, the adsorption process for the base-activated biochar follows both Langmuir and Freundlich isotherms at higher pH. The base-activated biochar exhibited a maximum adsorption capacity of 129.87 mg/g at alkaline pH. The adsorption data analysis with various kinetic models revealed that the adsorption process follows a pseudo-second-order kinetics for all the biochar materials. The Gibbs free energy and activation energy studies clearly revealed the adsorption of MB on biochar to be spontaneous and physiosorption in nature. The adsorption mechanism of the fast and efficient removal of MB by the base-activated biochar involves electrostatic interactions, hydrogen bonding, n-π and π-π interactions. Overall, the base-activated biochar with higher and faster adsorption capacity in alkaline conditions is a promising low-cost bioadsorbent with a simple production process for the removal of cationic dyes from aqueous environments and practical dyeing wastewater purification.

Mechanistic Insights into the Eco-Friendly Conifer Cone Extract's Corrosion Inhibition on Steel Rebar and Cement Mortar: An Experimental and Simulation Approach.

This study investigates the corrosion inhibition effects of eco-friendly conifer cone extract (CCE) on steel rebars embedded in cement mortar exposed to 3.5% NaCl under alternate wet/dry cycles. CCE concentrations of 0, 0.5, 1.0, 1.5, and 2.0% (denoted CCM0 to CCM4) were tested. Electrochemical and weight loss analyses revealed that 0.5% CCE significantly enhanced corrosion resistance, achieving 84.8% inhibition efficiency via polarization methods and a reduced corrosion rate of 9.46 mmpy. Chloride-binding studies indicated that 0.5% CCE improved adsorption intensity and multilayer adsorption constants compared to those of the control, as confirmed by Freundlich and Harkins-Jura isotherms. Surface analyses using SEM/EDS and AFM demonstrated the formation of a dense, protective passive layer on steel rebar surfaces, effectively reducing the surface roughness to 41.05 nm in CCM1 specimens. Theoretical simulations using SCC-DFTB and molecular dynamics showed a strong interaction between CCE functional groups and the iron surface, supporting experimental findings. Mechanical and porosity evaluations confirmed that 0.5% CCE maintained compressive strength and permeability while improving corrosion resistance. These results position CCE as a cost-effective, eco-friendly inhibitor with potential applications in protecting reinforced concrete structures in chloride-rich environments.

Batch Adsorption of Orange II Dye on a New Green Hydrogel-Study on Working Parameters and Process Enhancement.

A new green hydrogel consisting of cherry stone (CS) powder and sodium alginate (SA) was synthesized through physical crosslinking. The product had a mean diameter of 3.95 mm, a moisture content of 92.28%, a bulk density of 0.58 g/cm3, and a swelling ratio of 45.10%. The analyses of its morphological structure and functional groups by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) showed the successful entrapping of the CS in the SA polymeric matrix. The viability of the prepared hydrogel as adsorbent was tested towards Orange II (OII) anionic dye. The influence of the pH, adsorbent amount, contact time, and initial dye concentration was evaluated. Then, the impact of three accelerating factors (stirring speed, ultrasound exposure duration, and temperature) on the OII retention was investigated. The highest recorded removal efficiency and adsorption capacity were 82.20% and 6.84 mg/g, respectively. The adsorption followed Elovich and pseudo-second-order kinetics, was adequately described by Freundlich and Khan isotherms, and can be defined as spontaneous, endothermic, and random. The experiments confirmed that the obtained hydrogel can be used acceptably for at least two consecutive cycles, sustaining its effectiveness in water decontamination.

Flexible chitosan-graphene oxide-based biomacroporous cryogel via grafting cryopolymerization for selective recovery of myricetin from food sample.

Myricetin has a significant role in pharmacology, specifically in traditional Chinese medicine. The most intriguing pharmacological action of myricetin consists of its multi-pathway anticancer effects. Therefore, rapid and selective isolation of myricetin from garlic and apple juices has notable pharmacological benefits. Chitosan-graphene oxide-based biomacroporous cryogel are highly efficient and environmentally friendly materials for adsorption. The current study involved the synthesis of chitosan-graphene oxide-based biomacroporous cryogel sorbent for the selective recovery of myricetin. The characterization investigation utilizing SEM, XRD, EDS and FTIR demonstrated the successful synthesis of a chitosan-graphene oxide-based biomacroporous cryogel. Additionally, XPS effectively revealed the interaction of functional groups on the biomacroporous cryogel sorbent with myricetin. The maximum adsorption capacity for myricetin, under optimized conditions, was 167 mg g-1 in 60 min. The equilibrium adsorption capacity was achieved at neutral pH with optimal parameters, and the Freundlich isotherm model was followed. The pseudo-second-order model presented better descriptions of the adsorption process. In addition, the chitosan-graphene oxide-based biomacroporous cryogel exhibited remarkable selectivity: due to involvement of two primary factors: the number of hydroxyl-groups and the fact that the extra hydroxyl group at position 5' in ring B allows for a more noticeable transfer of the unshared electron pair from oxygen to the π system of the B ring. The adsorption of myricetin decreases to 2 % after three consecutive cycles, indicating the significant reusability of chitosan-graphene oxide-based biomacroporous cryogel. Additionally, the chitosan-graphene oxide based-biomacroporous cryogel that was produced has been utilized after one month and shown a comprehensive shelf-life. Typical adsorption mechanisms include hydrogen bonding and demonstrates significant potential for the efficient and specific isolation of myricetin in complex mixtures. Furthermore, the chitosan-graphene oxide-based biomacroporous cryogel demonstrated a significant rise in recovery of myricetin flavonoid in real samples of garlic and apple juices, rising from 99.66 % to 114.29 %.

Facile Preparation of Poly(AA‐co‐NaAMPS) Hydrogels Toward Toxic Dyes and Heavy Metals Removal via Frontal Polymerization

ABSTRACTWastewater treatment contributes to the sustainable utilization of water resources for alleviating water scarcity. The application of polymeric materials as adsorbents for eliminating hazardous substances in water has garnered extensive attention owing to their remarkable adsorption efficiency, stability, and selectivity. Herein, a facile strategy is provided to rapidly synthesize poly(acrylic acid‐co‐sodium 2‐acrylamide‐2‐methylpropanesulfonate) (poly(AA‐co‐NaAMPS)) hydrogels with exceptional adsorptive capacity via frontal polymerization (FP). The FP processes are meticulously examined in terms of initiator dosage and monomer ratio. The as‐prepared hydrogels demonstrate pH‐responsive swelling ability and pH‐dependent adsorption capacity for various dyes and heavy metal ions. Compared with traditional batch polymerization (BP), the hydrogels prepared by FP exhibit superior swelling and adsorption abilities. Additionally, research on the adsorption mechanism for both dyes and heavy metal ions is conducted by fitting the adsorption kinetic data both with Langmuir and Freundlich equations. The maximum adsorption capacity (qm) of hydrogels derived from Langmuir model for dyes of methylene blue (MB) and rhodamine B (RB) is, respectively, 595.3 and 3078.5 mg g−1, while for heavy metal ions of Cr3+ and Cd2+ is, respectively, 1010.8 and 1191.3 mg g−1. This research exploits an alternative approach for the rapid preparation of high‐efficiency hydrogel adsorbents toward wastewater treatment.

Optimizing Ni (II) adsorption on Carica papaya fiber through experimental and advanced neural network prediction

ABSTRACT Detoxification of Ni (II) ion from the synthetic wastewater by Carica papaya fiber (CPF) has been attempted in batch method. FTIR analysis detected prominent functional groups that helped in binding Ni+2. The most efficient sorption was observed at pH 6 and with the increase in the ratio of biomass to Ni (II) ion strength, the removal efficiency improved. 2.5 g/L CPF powder removed 90.83% Ni (II) from 10 mg/L solution at a contact time of 120 min and at 30°C. Both linear and non-linear forms of Langmuir, Freundlich, and Temkin isotherms were attempted. Langmuir isotherm in both types matched well (R2 = 0.999 and 0.994) and the maximum adsorption capacity was 21.84 mg/g. The spontaneity of the reaction was confirmed by ΔG° values (−12.06 to −13.71 kJ/mol) and was more favorable at higher temperatures. The reaction was endothermic (ΔH° 83.03 kJ/mol) and random (ΔS° 83.07 J/mol/K). The desorption study proposed active reprocessing of CPF up to three cycles. The results were scaled up for use by industries. This study reflects sustainable eco-innovation and a cost-effective approach for locally based small-scale industries for environmental preservation. The feed-forward back propagation neural network technique was applied for efficient prediction of the Ni(II) removal efficiency.

Evaluation of ozonated and ultrasonically treated corn starch as an adsorbent for patulin in buffer solutions

This study evaluates the potential of ozonated corn starch (OCS) and ultrasonicated ozonated corn starch (USOCS) as adsorbents for patulin removal in buffer solutions. The results indicated that dual modification significantly altered the starch’s structure, introducing functional groups such as carbonyl and carboxyl groups, and increasing its surface area. These modifications led to enhanced patulin adsorption capacity. Adsorption efficiency was tested across different adsorbent doses (150 mg, 200 mg, 250 mg) and contact times (15, 30, 45, and 60 min). The highest removal efficiency of 92.5% was recorded for the 250 mg dose at 60 min, with USOCS showing superior performance compared to native corn starch and OCS. Kinetic studies revealed that the pseudo-second-order model provided the best fit for the adsorption process, indicating chemisorption as the dominant mechanism. The Langmuir and Freundlich isotherms were used to describe the adsorption behavior, with a maximum adsorption capacity (qmax) of 15.19 µg/mg and a Langmuir constant (KL) of 54.00 L/µg for the 250 mg dose. Additionally, the modified starch demonstrated consistent adsorption performance at varying concentrations, with a favorable adsorption intensity (n > 1), supporting its potential for practical applications. These findings highlight the modified corn starch as an efficient, biodegradable, and low-cost adsorbent suitable for mitigating patulin contamination in food products, offering a sustainable alternative for improving food safety.

Valorization of Bauxite Residue for Use as Adsorbent for Reactive Blue Removal: Regeneration Evaluation

In recent years, there has been increasing concern regarding the widespread occurrence of dyes in aquatic environments, due to their harmful effects on both water quality and human health. This investigation uses bauxite residue as a cost-effective sorbent to eradicate the hazardous reactive blue (RB) dye from aqueous solutions. The reusability potential of bauxite residue was also evaluated. The bauxite residue was characterized by X-ray diffraction, Cation Exchange Capacity, Chemical analysis, FTIR, and Analysis of particle size and particle distribution. The RB dye adsorption parameters revealed that the removal efficiency and adsorption capacity of bauxite residue was 100% and 186.01 mg/g, respectively, under the following adsorption conditions: adsorbent dosage of 0.5 mg/L, initial pH of 2, dye concentration of 50 mg/g, and reaction temperature of 25 °C. Furthermore, the adsorption of RB dye on bauxite residue followed the pseudo-second-order kinetic and Freundlich isotherm models. After one adsorption cycle, the adsorption capacity of bauxite residue for reactive RB removal reached 186.01 mg/g. The regeneration study revealed that the bauxite residue remained 99% of its original condition following the water regeneration cycle.

Cell Morphology, Material Property and Ni(II) Adsorption of Microcellular Injection-Molded Polystyrene Reinforced with Graphene Nanoparticles.

Graphene's incorporation into polymers has enabled the development of advanced polymer/graphene nanocomposites with superior properties. This study focuses on the use of a microcellular foamed polystyrene (PS)/graphene (GP) nanocomposite (3 wt%) for nickel (II) ion removal from aqueous solutions. Adsorption behavior was evaluated through FTIR, TEM, SEM, TGA, and XRD analyses. Key factors, including initial ion concentration, pH, temperature, and sorbent dosage, were examined. Results showed optimal nickel removal at specific pH levels with removal efficiency decreasing from 91 to 80% as Ni (II) concentrations increased from 10 to 100 mg/L. The adsorption capacity improved from 11 to 130 mg/g. Equilibrium data aligned with Langmuir and Freundlich isotherm models, while adsorption kinetics followed a second-order kinetic model. These findings highlight the potential of PS/GP nanocomposites for nickel ion removal, offering a promising solution for small-scale industrial applications.

Adsorption Performance and Mechanistic Pathways of Raw Powdered Pine Cone Toward the Removal of Dye and Cr(VI)

ABSTRACTThis work aims to valorize pine cones powder (PCP), an agricultural waste, as a bioadsorbent for the removal of a cationic dye, Rhodamine B (RhB), and hexavalent chromium Cr(VI) from an aqueous solution. The adsorbent was characterized by scanning electron microscopy (SEM), Fourier‐transformed infrared (FTIR), and X‐ray diffractometer (XRD) spectroscopy. Adsorption studies were carried out in a batch mode under different operating parameters like initial solution pH (2–11), adsorbent dosage (0.025–0.6 g), initial contaminant concentration (20–100 mg/L), temperature (283–328K), contact time (0–120 min), and ionic strength (NaCl, MgCl2, CuSO4, Na2SO4, and FeCl3). The optimum conditions for adsorption for Cr(VI) were; ([Cr(VI)] = 30 mg/L, pH = 2, adsorbent dose = 1.5 g/L, T = 25°C), and for RhB: ([RhB] = 30 mg/L, pH = 4.6, adsorbent dose = 4 g/L, T = 25°C). Under these conditions, the maximum adsorption capacities reached were 19.861 and 6.565 mg/g, for Cr(VI) and RhB, respectively. The inhibiting effect of the studied salts on RhB dye and metal ion removal is as follows: FeCl3 &gt; CuSO4&gt; MgCl2&gt; Na2SO4&gt; NaCl. The Freundlich isotherm described the best the adsorption of Cr (VI) and RhB onto PCP, since it gave the highest R2 values (R2 ≥ 0.983) associated with the lowest error values (χ2, RMSE, and Δq). The calculated Dubinin–Radushkevich mean energy (E) is less than 8 kJ/mol. It is 3.391 kJ/mol for Cr(VI) and 2.310 kJ/mol for RhB sorption, respectively, confirming the physical character of adsorption onto PCP sorbent. Experimental data for Cr(VI) and RhB ion adsorption onto PCP, fitted well the pseudo‐second‐order kinetic model (R2 ≥ 0.997). According to the thermodynamic analysis, the retention of Cr(VI) and RhB followed a physisorption, endothermic, and spontaneous process at all temperatures for Cr(VI), and at higher temperatures for RhB dye. These results suggest that raw PCP may be envisaged as a promising biosorbent for water remediation without the need of costly heat and activation processes as a cheap and sustainable adsorption process.

Dictyota bartayresiana a sustainable biosorbent for the decolorization of reactive blue 19 – optimization, equilibrium, desorption and toxicological studies

The present study aims to investigate the dye decolorization efficiency of the brown seaweed Dictyota bartayresiana against reactive blue 19 (RB19) dye. The process variables namely dye and biosorbent concentration, pH and incubation time were optimized through BBD based RSM for achieving enhanced dye decolorization. The experimental data well fitted into Freundlich isotherm and proving the heterogenous adsorption of RB19. The Temkin and Dubinin – Radushkevich isotherm models showcased the endothermic and chemisorption mediated adsorption of RB19 onto D. bartayresiana. The pseudo second order kinetic model exhibited the chemisorption assisted adsorption and the Weber Morris kinetic model proved that the intra particle diffusion was not the rate limiting step in the adsorption of RB19 onto D. bartayresiana. Thermodynamic studies revealed the spontaneous, feasible and endothermic process of biosorption. Interaction between the dye and the biosorbent was assessed through UV-Vis, FT-IR and SEM which confirmed the process of decolorization. Desorption and regeneration studies revealed that 73% of the dye was desorbed in the first cycle using 0.1 M NaOH as eluent with regeneration efficiency of 68% which reduced in subsequent cycles highlighting the reusability of the biosorbent. Toxicity assessments of untreated and D. bartayresiana treated RB19 dye solution were examined on the microflora, brine shrimp and fenugreek and the results revealed the nontoxic nature of D. bartayresiana treated RB19 solution. Thus, this study provides valuable insights on utilization of D. bartayresiana as an eco-friendly biosorbent for the decolorization of RB19 and affirms its safe use in various biological applications.

Removal of malachite green dye by adsorption onto chitosan‐montmorillonite nanocomposite: Kinetic, thermodynamic and equilibrium studies

AbstractIn this study, the efficiencies of chitosan, montmorillonite, and chitosan/montmorillonite composites in various ratios for the removal of malachite green dye from aqueous solutions were investigated, and their maximum adsorption capacities were compared, and the effects of factors such as composite concentration, pH, contact time, dye concentration, and temperature were examined. Recovery attempts using different chemicals were also performed. Adsorption was analyzed using Langmuir and Freundlich isotherm models, and thermodynamic analyses were conducted. Fourier‐transform infrared (FTIR) and scanning electron microscopy (SEM) analyses were used to investigate surface changes. The highest adsorption capacity was found for the 20% chitosan/montmorillonite composite (400 mg g−1). Temperature studies indicated a decrease in adsorption capacity with increasing temperature. Kinetic studies observed that the data fit the pseudo‐second‐order kinetic model better. In recovery attempts, more than 95% recovery was achieved with HNO3 and HCl. FTIR results showed that chitosan–montmorillonite interactions involved ‐NH, ‐OH, C=O, and C‐O bonds, while dye binding was mainly through OH bonds. SEM analysis revealed that montmorillonite reduced surface cracks and roughness, creating a more homogeneous structure, and more rough areas appeared after dye binding. As a result, the chitosan/montmorillonite composite significantly enhanced dye adsorption capacity.

The Synthesis of Functionalized W5O14 Nanorods for the Adsorption of Bismarck Brown R from Wastewater

In this research, a tungsten oxide was prepared via a green (biogenic) synthesis route where sodium tungstate dihydrate and Punica granatum peel extract were used as a precursor and a reducing/capping agent, respectively. The characterization of the prepared tungsten oxide was performed through various spectroscopic and microscopic techniques. The characterization results revealed the preparation of highly crystalline and nanorod-shaped (length = 123 nm and width = 31.3 nm) tungsten oxide with a probable chemical formula of W5O14. Various functional groups on the W5O14 surface were also reported. The prepared nanorods were further used for the removal of Bismarck Brown R (BBR) dye from water in a batch manner. By varying the dose of nanorods (0.5–3.0 g L−1), BBR solution pH (2−10), contact time (15–120 min), BBR concentration in solution (10–60 mg L−1), and temperature of BBR solution (30, 40, and 50 °C), the optimized condition for maximum adsorption efficiency was measured. The results revealed that 2.0 g L−1 amount of nanorods of tungsten oxide were used to remove ~98% of BBR dye from its 10 mg L−1 at 30 °C and 7.0 pH. The temperature-dependent adsorption data were fitted to different types of non-linear isotherm models (e.g., Langmuir and Freundlich) to assess the adsorption potential and adsorption mechanisms in relation to temperature impacts. The synthesized nano-adsorbent fits the Langmuir as well as the Freundlich isotherm model with a maximum adsorption capacity of 17.84 mg g−1. Pseudo-first-order, pseudo-second-order, and Elovich kinetic models were used for the study of adsorption kinetics. BBR adsorption onto the W5O14 nanorods follows the pseudo-second-order rates. The present adsorption is governed by physico-chemical adsorption with predominant chemical interactions.

"Theory of Pore Conflation" and "Shubhjyot's equation" in the treatment of Brilliant green dye-contaminated water using Jamun leaves biochar

This study investigates the adsorption of Brilliant Green (BG) dye onto biochar derived from Syzygium cumini (Jamun) leaves (JLB). Biochar was produced via pyrolysis at 800 °C and examined employing various methods, including Scanning electron microscopy (SEM–EDX), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) analysis, Raman spectroscopy, Zeta potential and X-ray photoelectron spectroscopy (XPS). The optimum parameters for BG dye adsorption, determined by batch adsorption studies, were a temperature of 80 °C, an initial dye concentration of 500 mg L−1, a contact period of 30 min, and an agitation speed of 400 RPM. The maximum adsorption capacity of JLB for BG was 243.90 mg g−1. It was found that the adsorption process adhered to the Freundlich isotherm model and pseudo-second-order kinetics, revealing heterogeneous adsorption with chemisorption. A novel "Theory of Pore Conflation" was proposed to explain enhanced adsorption at higher temperatures, supported by SEM and FTIR analyses. Additionally, a new equation termed "Shubhjyot's equation" was introduced to account for time dependency in adsorption capacity calculations. The thermodynamic analysis demonstrated that the process is endothermic and spontaneous. Isopropanol was the most effective organic solvent for desorption studies, demonstrating biochar regeneration potential for up to five cycles. Phytotoxicity and cyto-genotoxicity assessments demonstrated the environmental safety of JLB compared to BG dye. The use of JLB production offers a way to repurpose agricultural waste, contributing to circular economy principles. This extensive study demonstrates JLB's promise as an effective, economical, and environmentally safe adsorbent for wastewater treatment that eliminates textile dyes.Graphical

Effectively eliminating lead and cadmium from industrial wastewater using a biowaste-based sorbent

Toxic heavy metals, such as Pb(II) and Cd(II), pose serious environmental and health risks, stressing the urgent demand for innovative and sustainable techniques to reduce their adverse effects. This study investigates the use of sugar beet biowaste as an eco-friendly biosorbent for the removal of Pb(II) and Cd(II) from aqueous solutions, in both laboratory and industrial effluents. Characterization through scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy revealed the formation of stable hydrocerussite and otavite, confirming chemisorption. Approximately 95% of the employed biowaste is composed of calcium (Ca), carbon (C), and oxygen (O). The zeta potential was measured at − 17.5 mV with a point of zero charge at pH 8.0, and the total surface area of the biosorbent was approximately 7.72 m2 g−1, with a Langmuir surface area of 11.563 m2 g−1 and a pore volume of 0.028 cm3 g−1. Various parameters, such as the metal concentration, biosorbent dosage, pH, temperature, and contact time, were optimized, achieving maximum removal of Pb(II) and Cd(II) within 60 min at pH 12 and 328 K. Sorption followed a pseudo-second-order kinetic model (R2 = 0.99) and the Freundlich isotherm (R2 = 0.98), with high sorption capacities of 466.5 mg g−1 for Pb(II) and 505.6 mg g−1 for Cd(II). Thermodynamic analysis indicated that the sorption process is spontaneous, thermodynamically favorable, and endothermic. The biowaste effectively removed heavy metals and demonstrated removal efficiencies exceeding 85% for most heavy metals in industrial effluent samples from Alexandria and Ain Sokhna. Sorption capacity ratio values close to 1 indicate effective Pb(II) and Cd(II) uptake with minimal interference, even in the presence of methylene blue dye. Comparative analysis revealed that the untreated biosorbent was more efficient than typical biosorbents, and an economic cost evaluation revealed that processing the biosorbent costs 1.05 USD/kg, highlighting its potential as a sustainable and economically viable option for industrial effluent treatment and supporting broader environmental goals.

A Comparative Kinetic and Thermodynamic Adsorption Study of Methylene Blue and Its Analogue Dye on Filter Paper.

A comparative adsorption study was carried out for methylene blue (MB) and its 3,7-bis(N,N-(2-hydroxyethyl)amino)-phenothiazinium dye analog (MBI). Batch experiments employed aqueous solutions and commercial filter paper. Out of seven kinetic models tested by means of four quality statistical indicators, the pseudo-second-order, the double-exponential, and the bi-linear Weber-Morris equations were best fits. For both dyes, the process was described as a succession of two diffusion-controlled steps. The Freundlich isotherm was chosen from 11 models describing a variety of mechanism assumptions. Physisorption was considered responsible for the dye removal from liquid. Adsorption of MB is thermodynamically favored, whereas that of MBI is sterically hindered. Both processes are exothermic and exhibit reduced randomness at the S-L interface. The paper was found suitable for retaining MB but served rather filtration/purification purposes for MBI.