Pseudo-second Order Kinetic Model Research Articles

Monodispersed FeS nanoparticles decorated on kaolinite for synchronous removal of benzo [a]pyrene and Cr(VI) complex pollution

Novel FeS/kaolinite composite (K-FeS) were successfully prepared using an in-situ precipitation method. At 30 % FeS loading, 1 g/L of the composite material by activating peroxymonosulfate (PMS) was able to completely remove 20 mg/L benzo[a]pyrene (BaP) and 40 mg/L Cr(VI) within 20 min under optimized conditions. The simultaneous removal experiments of BaP and Cr(VI) for the influence factors of BaP concentration, Cr(VI) concentration, composites dosage and PMS dosage to be 20 mg/L, 40 mg/L, 1 g/L, and 0.75 mmol/L, respectively. Experiments on environmental factors show that low temperature and acidic conditions are more favorable for material activity, and the addition of Cl- could promote the removal of BaP and Cr(VI). Comparative experiments showed that the simultaneous presence of BaP and Cr(VI) did not affect the removal of each other. The pseudo second-order kinetic model and Langmuir adsorption isotherm model were better to fit the experimental data, and the thermodynamic analyses indicated that the removal processes of BaP and Cr(VI) were spontaneous and exothermic. Besides, the quenching experiments yielded that SO4− and OH played a dominant role in BaP removal, and Cr(VI) removal mainly depended on the reduction of composites. This study expands the application of clay minerals in water treatment and suggests new strategies for simultaneous treatment of multiple pollutants in the environment.

Kinetic, equilibrium, and thermodynamic studies of adsorptive interactions of eosin-B on chemically treated orange peels

The present study investigated the adsorption of eosin B on the surface of powdered and chemically treated orange peels, along with this process’s condition optimizations, kinetics, and thermodynamics. The adsorbent dose (0.1–0.5 g), temperature (298, 303, 308, and 313 K), contact time (15–120 min), initial pH value (2–11) of the solution, and interfering salts (0.01 and 0.1 mol L−1) were all taken into consideration during the experiments. At all investigated temperatures and pH of 2, adsorption was more favourable. Although the Langmuir model might also represent the adsorption data, the Freundlich and Dubinin–Radushkevich (D–R) models provided a good description. The pseudo-second order kinetic model was followed during the adsorption process. The mechanics of the rate-controlling step were examined by applying the intra-particle diffusion-based mass transfer model to the experimental data. It was discovered that the only process that controlled the rate was intra-particle diffusion. The adsorption process appears to be spontaneous, and endothermic and involves van der Waals forces based on thermodynamic data.

Enabling highly efficient navy-blue dye degradation over the LaFeO3/B-g-C3N4/WO3 double z-scheme heterostructure

Chemical reactivity, optical and electronic features of conventional photocatalysts can be improved by chemical modification and nanocomposites fabrication techniques. Herein, a double Z-scheme LaFeO3/B-g-C3N4/WO3 (LFO/B-CN/WO) heterostructure nanocomposite has been successfully fabricated via a hydrothermal approach. XRD, FT-IR, SEM/EDS, TEM, TGA/DSC, and UV–visible spectroscopy confirmed crystallographic planes, phase purity, and heterojunction between LFO, WO and B-CN. From UV visible absorption spectroscopy, it was confirmed that optical band gap energy of CN is remarkably reduced after boron doping. The LFO/B-CN/WO photocatalyst revealed 96 % degradation performance for Navy Blue (NB) dye after visible light irradiation for 130 min under neutral pH conditions. The data were analyzed using pseudo-first and pseudo-second order kinetics models to evaluate the dye degradation kinetics. Compared to the CN, B-CN, LFO-CN and WO-CN photocatalysts, the performance of LFO/B-CN/WO was much significant. Improved light absorption capability, effective spatial separation and prolonged charge-carrying capacity of the double Z-scheme system resulted in enhanced photocatalytic performance. This study offers new insights into the design and synthesis of highly efficient Z-scheme heterojunction photocatalysts for environmental decontamination and clean energy purposes.

Cu (II) adsorption in rice husk for water treatment: Batch and fixed column experiments

Cu (II) is a heavy metal found in water bodies and harmful to the environment and human health. Thus, this study evaluated Cu (II) adsorption in rice husk using batch and fixed bed tests, employing synthetic solutions and real water samples to simulate contaminated water treatment. Batch tests were performed using rice husk and synthetic Cu (II) solutions with concentrations varying from 1 to 128 mgL−1. The isothermal behavior of the adsorption process was evaluated using Langmuir and Freundlich nonlinear models, whereas mechanisms and adsorption rates were assessed using pseudo-first and pseudo-second order kinetic models. The fixed bed column was mounted on a 5-cm thick rice husk adsorbent bed and synthetic and real solutions were employed (concentration: 8 mg L−1; flux: 13 mL min−1). The equilibrium was reached after 20 min, with the best adjustment to the pseudo-second order model. The experimental data were better adjusted to the Langmuir model (estimated qmax: 7.19 mgg−1). The adsorption column exhibited adsorption capacities of 1.28 and 1.12 mgg−1 and saturation percentages of 83 % and 79 % for synthetic and real solutions, respectively, and were adjusted to Thomas model. The results indicate that rice husk can be an effective alternative for Cu (II) removal in contaminated water.

KINETIC AND THERMODYNAMIC ADSORPTION STUDIES ON THE REMOVAL AND TREATMENT OF TEXTILES EFFLUENTS USING ACTIVATED CARBON DERIVED FROM DIOSPYROS MESPILLIFORMIS SEEDS.

An agricultural waste Diospyros mespiliformis seeds were treated, and activated with 30% of 0.3M sodium hydroxide base, to obtain an activated carbon employed in an adsorption process. It was utilize to treat effluent textile water sample from African Textile Manufacturers Limited in Dala, Kano State, Nigeria. Various techniques, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and proximate analysis were employed to investigate the adsorption process. The adsorbent was able to remove the dark red color to colorless found in textile effluents and shown a higher removal affinity for zinc ( 99.4%) and least affinity for nickel (0.11%), also Chromium (Cr) reduced by 39.4%, Copper (Cu) reduced by 20.9%, Iron (Fe) reduced by 91.9% , Manganese (Mg) reduced by 79.3%, are reduced significantly, the PH change from acidic PH 6.4 to neutral PH 7.1, turbidity decrease from 131 to 14 NTU , electrical conductivity change from 723 to 110 ?s·cm?1 .Diospyros mespiliformis seeds activated carbon was used for removal of congo red and malachite green from an aqueous solution. The effect of adsorbent dose, adsorbate concentration and contact time on the process of adsorption was investigated. The optimum dosage was found to be 0.5g had a percentage removal of 98.1% for congo red and 94.4% for malachite green. 10mg/l and 80minute was found to optimum concentration and optimum time in adsorption of congo red and malachite green. The equilibrium, kinetic and thermodynamic properties of the dyes removal were also investigated. The experimental data were modeled using linear regression method of analysis. The correlation coefficient was used as a criterion for model adequacy and acceptance. The pseudo second-order kinetic model was found to best correlate the experimental data with R2 of 0.9523 for CR and 0.9297 for MG. The experimental data were investigated at three different temperature, 305k, 325k and 335k were found to follow the Langmuir model with R2 of 0.9679, 0.9662 and 0.989 for CR and 0.9529, 0.9662 and 0.994 for MG. also were found to follow Temkinp model with with R2 of 0.9549, 0.9318 and 0.9952for CR and 0.9885, 0.9443 and 0.9209 for MG. The negative free gribbs energy indicated that the adsorption processes were spontaneously feasible. The positive values of +31.66KJ/mol and +92.3KJ/mol on both CR and MG indicate that adsorption process has been found to be endothermic in nature. The removal of congo red was found to be more spontaneous and feasible than the removal of malachite green on the adsorbent. From the study, it was deduced that the Diospyros mespiliformis seeds activated with sodium hydroxide was found to be a good adsorbent for the treatment of textile wastewater containing Congo red and Malachite green.

Nanostructured layered double hydroxide (NLDH) - Zn/Al-based materials: strategy to improve performance for zirconium sorption from acidic sulfate solution.

Zirconium is a highly stable radionuclide commonly used in various nuclear operations. However, removing zirconium from wastewater streams is crucial to protect the environment and human health. To achieve this, a zinc and aluminum nanostructured layered double hydroxide (Zn/Al-NLDH) was prepared and investigated for effective removal of zirconium from aqueous solutions. This study examined the prepared Zn/Al-NLDH's structural and textural properties and the impact of various factors on its adsorption performance. The Langmuir isotherm and Pseudo-second order kinetic models were found to be the best fit for the adsorption process of Zr(vi). This suggests that the adsorption process is uniform, involves the formation of a monolayer, and is chemisorption in nature. The maximum uptake capacity was 117.6 mg g-1, and the process was endothermic, spontaneous, and feasible. About 96% of Zr(vi) was successfully desorbed from the loaded sorbent using 1.0 M hydrochloric acid, and the Zn/Al-NLDH sorbent remained stable for six consecutive sorption/desorption cycles. These findings emphasize the high potential of Zn/Al-NLDH to act as a remarkable sorbent for efficiently tackling water contaminants.

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.

Removal of Pb(II) ions from aqueous solutions using natural and HDTMA-modified bentonite and kaolin clays

This work focused on the removal of Pb(II) from aqueous solution using kaolin and bentonite clays modified with hexadecyl trimethyl ammonium bromide (HDTMA). The clays were characterized using a zetasizer, scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Brunauer-Emmet-Teller (BET), Fourier-transform infrared (FTIR) spectroscopy and thermal gravimetric analysis (TGA). Factors that influence the adsorption of Pb(II) from aqueous solution, namely pH, contact time, adsorbent mass, ionic strength, temperature and initial Pb(II) concentration were investigated. The results show that HDTMA was successfully incorporated into the kaolin and bentonite clay structures. The most favorable parameters for the adsorption of Pb(II) ions onto all adsorbents was pH of 6.0, temperature of 25 °C and adsorbent mass of 200 mg. Adsorption isotherms and kinetic studies showed that the adsorption of Pb(II) onto kaolin, bentonite and organobentonite clays followed the Langmuir isotherm and pseudo-first order kinetic model, while the adsorption onto organobentonite was better explained by the Freundlich isotherm and pseudo-second order kinetic model. Maximum monolayer adsorption capacity of organobentonite, calculated from the Langmuir model was 18.75 mg/g, which is higher than that obtained for the unmodified bentonite (14.71 mg/g); while for organokaolin it was 2.26 mg/g, which is less than that of the unmodified kaolin (4.19 mg/g). Thermodynamic studies showed that the reactions were exothermic and unfavoured at high temperatures. The adsorbents also showed good removal efficiency for up to four regeneration cycles.

Removal of sulphur and nitrogen compounds from model fuel by adsorption of modified activated carbon

This study aimed to achieve the highest percentage removal of dibenzothiophene (DBT), quinoline (QUI), and indole (IND) adsorbed by double-impregnated modified activated carbon (MAC). Modification of commercial activated carbon (AC) by sulphuric acid (H2SO4) of 15%, 30%, 45%, 60%, and 75% w/v followed by subsequent 1 zinc chloride (ZnCl2): 1 AC impregnation ratio and activated at 500 oC in a muffle furnace under self-generated atmosphere for an hour. The determination of optimized MAC was identified through the highest removal rate of DBT, QUI, and IND from adsorption experiments which were analysed using an ultraviolet-visible (UV-Vis) spectrophotometer. It was found that DBT and IND showed a removal high percentage of up to 86.23% and 82.77% respectively by using 75% H2SO4 with ZnCl2 MAC. Meanwhile, QUI favoured 30% H2SO4 with ZnCl2 MAC with a removal percentage of 33.17% which was still higher than unmodified AC. Physical and chemical properties such as the morphological structure, elemental analysis, porosity, pore size, surface functional group, percentage yield, pH, bulk density, content, ash content, and iodine number were studied for the optimized MAC. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy and Fourier transform infrared spectroscopy (FTIR) were used to characterize the MAC. Both MACs showed high percentage yields of 72.08% and 71.13% for 30% and 75% H2SO4 and ZnCl2 MAC respectively. Meanwhile, the pH was between the ranges of 5.36-5.53 for both MACs. Bulk densities were also favourable while the moisture and ash content were within acceptable limits. Iodine numbers for 30% and 75% H2SO4 and ZnCl2 MAC were 857 and 861 mg/g respectively, hence indicating that the MAC achieved high porosity and good adsorption performance. Langmuir, Freundlich, and Temkin adsorption isotherm models as well as pseudo-first order (PFO) and pseudo-second order (PSO) kinetic models were considered for understanding the adsorption mechanisms. The study revealed that DBT, QUI, and IND removal processes, followed the Langmuir adsorption isotherm model with correlation coefficients, R2 of 0.9905, 0.9791, and 0.9964 respectively. Moreover, the adsorption kinetic data of DBT, QUI, and IND provided a better fitting to the PSO kinetic model with R2 of 0.9992, 0.9987, and 0.9998 respectively. According to the Langmuir isotherm model and PSO kinetic model, the adsorption mechanisms of DBT QUI and IND were chemisorbed under monolayer formations.

Conversion of PET bottles into carbonaceous adsorbents for Pb(II) removal from aqueous solutions via KOH activation

In this study, we present a novel approach to repurpose waste Polyethylene terephthalate (PET), a prominent contributor to global plastic usage, for the synthesis of efficient adsorbents via facial pyrolysis. The as-synthesized adsorbents were applied for the removal of lead (Pb(II)) ions in aqueous solution. Controlled batch experiments at pH 5 with 0.075 g of adsorbent at room temperature (20 °C) were conducted to measure Pb(II) adsorption capacities (mg/g) and fitted on isotherm models (Langmuir, Freundlich, and Temkin) and kinetics models (Pseudo-First order, Pseudo-Second order, and Elovich). Thermodynamic experiments conducted at four different temperatures (293 K, 303 K, 313 K, and 323 K) provided enthalpy, entropy, and Gibbs free energy change parameters, explaining the Pb(II) adsorption behaviors on PET-based adsorbents. The activation process involving KOH, followed by carbonization, yielded adsorbents with exceptional surface areas, pore volumes, and elevated oxygen contents (up to 22.8 %). The best adsorbent exhibited superior performance, achieving a maximum adsorption capacity of 219.7 mg/g within a rapid equilibrium time of 15 min. The adsorption behavior adhered well to the Langmuir isotherm model (R2 = 0.999) and Pseudo-Second Order kinetics model (R2 = 0.999). Furthermore, C600K600 displayed outstanding reusability, with negligible efficiency reduction (<5 %) even after five consecutive cycles. These results underscore the successful conversion of PET waste into a low-cost and highly effective adsorbent, offering a promising solution for sustainable waste management.

Novel sustainable porous organic polymer for multifunctional water treatment: Adsorption and disinfection applications

The removal of dyes and bacteria from wastewater is crucial for environmental remediation and public health protection. The discharge of untreated wastewater containing dyes and bacteria can lead to water pollution, ecosystem disruption, and human health risks. In this context, we report the development of a sustainable gallic acid-based porous organic polymer (GA-azo-DADPM POP) for multifunctional water treatment applications. The polymer was characterized using 13C CP/MAS NMR, ATR-FTIR, SEM, and TEM, confirming its formation and revealing its agglomerate morphology, porous nature, and stacked sheet-like structure. The polymer exhibited a high BET surface area of 402 m2/g and a pore size distribution in the range of 2–20 nm, indicating its mesoporous nature. The adsorption studies demonstrated a maximum methylene blue dye removal capacity of 141.94 mg/g, while the antibacterial performance showed effective disinfection against E. coli. The adsorption studies followed the Freundlich isotherm and Pseudo second-order kinetic model. These results highlight the potential of GA-azo-DADPM POP for simultaneous dye removal and bacterial disinfection in wastewater treatment. In conclusion, this study demonstrates a novel, sustainable, and multifunctional material for water treatment, offering a promising solution for environmental restoration. The development of such materials can contribute significantly to the advancement of water treatment technologies, ensuring a safer and more sustainable future.

Deep Cleaning of Crystal Violet and Methylene Blue Dyes from Aqueous Solution by Dextran-Based Cryogel Adsorbents.

Polysaccharides have recently attracted growing attention as adsorbents for various pollutants, since they can be extracted from a variety of renewable sources at low cost. An interesting hydrophilic and biodegradable polysaccharide is dextran (Dx), which is well-known for its applications in the food industry and in medicine. To extend the application range of this biopolymer, in this study, we investigated the removal of crystal violet (CV) and methylene blue (MB) dyes from an aqueous solution by Dx-based cryogels using the batch technique. The cryogel adsorbents, consisting of cross-linked Dx embedding a polyphenolic (PF) extract of spruce bark, were prepared by the freeze-thawing approach. It was shown that the incorporation of PF into the Dx-based matrix induced a decrease in porosity, pore sizes and swelling ratio values. Moreover, the average pore sizes of the DxPF cryogels loaded with dyes further decreased from 42.30 ± 7.96 μm to 23.68 ± 2.69 μm, indicating a strong interaction between the functional groups of the cryogel matrix and those of the dye molecules. The sorption performances of the DxPF adsorbents were evaluated in comparison to those of the Dx cryogels and of the PF extract. The experimental sorption capacities of the DxPF cryogel adsorbents were higher in comparison to those of the Dx cryogels and the PF extract. The DxPF cryogels, particularly those with the highest PF contents (sample DxPF2), demonstrated sorption capacities of 1.2779 ± 0.0703 mmol·g-1, for CV, and 0.3238 ± 0.0121 mmol·g-1, for MB. The sorption mechanisms were analyzed using mathematical models, including Langmuir, Freundlich, Sips and Dubinin-Radushkevich isotherms, and kinetic models, like pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich and intra-particle diffusion (IPD). The sorption process was best described by the Sips isotherm and PSO kinetic models, indicating chemisorption as the dominant mechanism. This study outlines the importance of developing advanced renewable materials for environmental applications.

FACILE SYNTHESIS OF ACTIVATED CARBON/ALGINATE/CHITOSAN COMPOSITE BEADS AS RHEMAZOLE BRILLIANT BLUE R ADSORBENT

Developing composite beads composed of chitosan, alginate, and activated carbon for dye removal is essential due to their improved adsorption capabilities and environmental benefits. By utilizing natural resources efficiently for an effective dye removal process, this study developed an activated carbon/alginate/chitosan composite bead as Rhemazole Brilliant Blue R (RBBR) adsorbent. The surface shape of composites exhibits more protrusions, grooves, and asymmetric pores than activated carbon, which could improve dye adsorption capability. FTIR analysis verified that functional groups such as OH, NH, protonated amine, and carboxylate from the constituent polymers were enriched in the activated carbon/alginate/chitosan composite. These groups also function as active sites for adsorbents. It was aligned with the composite beads' Freundlich isotherm model, which shows that heterogeneous or many active sites contribute to adsorption and provide multilayer adsorption. The kinetic model of pseudo-second order fits well with the adsorption process, indicating that chemisorption is the rate-limiting step in RBBR adsorption. The optimum adsorption conditions were at pH 1, with an adsorbent dose of 0.08 g, RBBR dye concentration of 125 mg/L, and a contact time of 60 min. The composite beads also exhibit stability in acidic and basic solutions, with the effectiveness of being reused up to four times, providing a reusable adsorbent with versatility in various water treatment conditions. Hence, synthesizing activated carbon/alginate/chitosan composite beads presents a promising solution for sustainable wastewater treatment based on biodegradable and eco-friendly composite.

Removal of hazardous Aniline Blue dye using a potential Biosorbent – Hen feather

In this research we have successfully removed a highly toxic dye, “Aniline Blue”, from its aqueous solution employing an adsorbent, Hen Feathers. The dye adsorption over Hen Feather was comprehensively studied over ranges of contact time, pH, concentration, and adsorbent dosage, and the optimum values were evaluated. In order to understand the behaviour of the adsorption system, various isotherm models were evaluated at temperatures of 30, 40 and 50 °C. The data obtained from contact time studies were used to test pseudo-first and pseudo-second order kinetic models and it was found that the adsorption follows pseudo-second-order kinetics. Using the Langmuir constant, b, thermodynamic parameters including ΔG°, ΔH° and ΔS° were calculated and it was ascertained that the process is endothermic (positive ΔH°), involves an increase in disorder (positive ΔS°) and is spontaneous (negative ΔG°). The values of the separation factor (r) also confirmed a favourable adsorption process at all three temperatures studied. Overall, it is affirmed that the adsorbent, Hen Feather, acts as highly potent scavenger to remove the dye Aniline Blue from its aqueous solutions.

Synthesis of porous carbons for the fixing of cationic molecules in aqueous solution

In Africa, the calyxes of the Hibiscus sabdariffa are widely used to produce a fresh fruit juice, known in Benin as bissap. The stems from this production have no potential use and are therefore an environmental problem. The parietal composition of these stalks revealed a high level of lignin (31 ± 1 %) and cellulose (35 ± 1 %). They can therefore be converted into activated carbon for various applications. In this study, the stems were transformed into activated carbons at moderate temperature using orthophosphoric acid (H3PO4) as the activating agent. The physicochemical, structural, and textural properties were determined. Adsorption kinetics and isotherms were studied and modelled. Porous carbons give specific surface areas equal to 1066 and 1053 m2.g−1 respectively for 2:1 and 4:1 ratios according to the B.E.T-Rouquerol model. Similarly, the said porous carbons give specific surface areas equal to 991 and 975 m2.g−1 respectively for 2:1 and 4:1 ratios according to the 2D-NLDFT model. Using the latter model, the pore size distribution is predominantly microporous, with the Vµ/VT (%) ratio increasing to 56 %. Thermogravimetric analysis of the porous coals showed favourable fixed carbon levels (≈ 60 %). The adsorption kinetics of methylene blue on activated carbons is governed by the pseudo-second order kinetic model indicating that the dye adsorption process is globally controlled by chemisorption. The results of the modelling of the methylene blue adsorption isotherms shown that the Langmuir model is the most credible model that best describes these experimental results, with 588 and 526 mg.g−1. These activated carbons are good candidates for the development of bio-sourced filters for the treatment of industrial wastewater.

Urea-modified hazelnut shell biochar (N-HSB) for efficient Cr(VI) removal: Performance and mechanism insights

Composite with a high specific surface area of 224.62 m2 g−1 was prepared by adding urea as a nitrogen source to hazelnut shell biochar (HSB). Nitrogen doping significantly enhanced the ability of biochar for Cr(VI) elimination, achieving twice the removal efficiency of unmodified biochar. The impacts of varying the pH and initial concentrations on Cr(VI) removal by urea-modified biochar (N-HSB) were investigated. The Cr(VI) removal by N-HSB was better described by intra particle diffusion model and pseudo-second order kinetic model under optimal conditions. Furthermore, XPS, FTIR, SEM, and BET analyses were used to verify the pivotal roles of oxygen- and nitrogen-containing functional groups. Electrostatic attraction, redox reaction, and complexation constituted the principal mechanisms facilitating Cr(VI) elimination by N-HSB. This study demonstrated that the modification of biochar with urea as a nitrogen source represented a promising strategy for enhancing the removal capacity of biochar for Cr(VI) in aqueous environments.

PW12/Fe3O4/biochar nanocomposite as an efficient adsorbent for metronidazole removal from aqueous solution: Synthesis and optimization

The growing occurrence of antibiotics in aquatic environments has emerged as a notable environmental issue given their potential detrimental impacts on ecosystems and the well-being of individuals. Therefore, there is a pressing need to develop effective strategies for removing antibiotics from wastewater. Herein, PW12/Fe3O4/biochar nanocomposite as a highly efficient adsorbent was synthesized to remove metronidazole (MNZ) antibiotic from wastewater through a sustainable and environmentally friendly approach. Simple surface modifications, such as chemical and physical modification with acid and base, as well as adding polyoxometalate were employed to enhance the adsorption of MNZ. The physical and chemical characteristics of the adsorbent were extensively analyzed using several techniques as follows, Fourier transform infrared (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray (EDX), Brunauer-Emmett-Teller (BET), and transmission electron microscopy (TEM). Experimental results demonstrated a significant increase in the efficacy of MNZ removal when the adsorbent surface was modified with polyoxometalate (H3PW12O40) compared to magnetic biochar (MBC). This improvement favors the pore-filling mechanism, electrostatic, H-bonds, and π-π interactions. To optimize the operating parameters for MNZ removal, response surface methodology (RSM) was employed using Design Expert software, considering the pH of a solution, initial pollutant concentration, adsorbent amount, and contact time. The results revealed that when the conditions were ideal (pH ∼1, initial concentration of MNZ at 5 mg/L, adsorbent amount of 0.6 g/L, and contact time of 60 minutes), the removal efficiency and the adsorption capacity reached 94.28 % and 78.45 mg/g, respectively. The analysis of isotherm and kinetic experiments revealed that the adsorption mechanism followed the Freundlich isotherm and pseudo-second order kinetic models, respectively. Furthermore, the adsorbent demonstrated excellent efficiency and reusability, with a removal efficiency of over 90 % even after four cycles, highlighting its potential and economic viability as an adsorbent for metronidazole removal.

Two-dimensional MXene and molybdenum disulphide for the removal of hexavalent chromium from water: A comparative study

Chromium is a carcinogenic heavy metal that accumulates in plant and animal bodies. New materials for efficient removal of chromium from water bodies are in high demand. MXene was synthesized from MAX phase by using ammonium fluoride as an etching agent while molybdenum disulphide was synthesized by hydrothermal method. The pseudo-second order kinetic model described the adsorption of hexavalent chromium on MXene and molybdenum disulphide whereas the Freundlich Isotherm model best fitted for Mxene, and Langmuir Isotherm model was more suitable in case of molybdenum disulphide. The adsorption capacity obtained by MXene for hexavalent chromium was 59.8 mg/g (At Dosage = 1 g/L, T = 298 K, Time = 9 h, pH = 2, Co = 30 mg/L) and 113.7 mg/g in case of molybdenum disulphide (At Dosage = 0.5 g/L, T = 298 K, Time = 1.5 h, pH = 2, Co = 30 mg/L). Thermodynamic investigations showed that the process was endothermic and spontaneous. The coexisting ions showed a decrease in removal percentage up to 70 % and 79 % in case of MXene and molybdenum disulphide, respectively, after fifth cycle. It can be inferred that these developed materials have the advantages of simplicity for reducing heavy metal pollution.

Calcined biomass-bentonite composites as eco-friendly adsorbents for the treatment of toxic anionic and cationic dye wastewater

Adsorption is a suitable technique for decontamination of organic dye wastewaters. Herein, we comparatively investigated the adsorption performance of bentonite (BEN) and its modification with groundnut shell (BGS) and palm kernel shell (BPS) for methylene blue (MB) and congo red (CR) dyes removal from aqueous solution. BGS and BPS were prepared by calcination at 300 °C for 6 h and were characterized using BET, SEM, EDS and FTIR to determine their textural properties, morphologies, elemental compositions, and functional groups. The BET surface examination revealed that the surface area of BEN was enhanced from 78 m2/g to 195 m2/g and 141 m2/g after modification with groundnut shell (BGS) and palm kernel shell (BPS), respectively. The adsorption process in a batch system was subjected to comprehensive experimentation to investigate the effect of adsorbent dosage, contact time, temperature, initial concentration, and pH. The adsorption was fitted to adsorption isotherm and kinetic models and the results revealed that the adsorption process of BEN, BGS, and BPS towards MB and CR adsorption can be best described by Temkin, Freundlich and pseudo-second order kinetic models. The adsorption capacities (qmax) for uptake of MB by BEN, BGS and BPS are 10.61, 10.85 and 10.93 mg, while CR exhibited 8.83, 6.87 and 5.86 mg/g, respectively. The thermodynamics study revealed that the adsorption process was spontaneous, feasible, endothermic in nature. The adsorption process is governed by electrostatic attraction with the involvement of physical and chemical adsorption. This study suggests that biomass-modified bentonite is a sustainable, cost-effective, non-toxic, and greener approach for eliminating MB and CR from aqueous solution. Furthermore, the modification method does not only achieve substantial removal of MB and CR dyes, but also offers considerable energy savings and operational cost reductions in real-time based on water quality data. This study does present a novel, sustainable approach to improve natural water treatment efficiency and compliance.

Thermodynamics, kinetic study and equilibrium isotherm analysis of cationic dye adsorption by ternary composite

This article investigates the kinetics, equilibrium, and thermodynamics of brilliant green dye adsorption on Fe3O4/CdS/MWCNTs. The effects of adsorbent dosage (0.01–0.06 g), contact time (1–120 min), temperature (278, 288,298 and 308 K), ionic strength (NaCl and CaCO3 salt), and initial solution pH (4,6,7, and 10) were all studied in relation to the adsorption of BG dye. Langmuir (R2 = 0.86883), Temkin (R2 = 0.96323) and Freundlich (R2 = 0.96958) and isotherms were fitted to describe the equilibrium of BG adsorption process. Isothermal models showed that BG adsorption was a favorable process on ternary composite Adsorption kinetics were well fitted by Pseudo-second order kinetic model (R2 = 0.99396). The thermodynamic parameters ΔH° = −0.0277 kJ.mol−1 and ΔS° = −60.9031 J mol−1.k−1 indicate endothermic and spontaneous adsorption process, (ΔG° > 0) non-spontaneous, and exothermic. Five adsorption/desorption cycles were demonstrated by the adsorbents’ high reusability.