Pseudo First-order Model Research Articles

Evaluation of Thermodynamic Parameters for Cu(II) Ions Biosorption on Algae Biomass and Derived Biochars

The removal of metal ions by biosorption on inexpensive materials is still a challenge for environmental engineering research. In this study, marine green algae biomass (Ulva lactuca sp.) and the biochars obtained from this biomass, at 320 °C (BC-320) and 550 °C (BC-550), were used as biosorbents for the removal of Cu(II) ions from aqueous solution. In addition to comparing the biosorption capacities, the determination of the thermodynamic parameters allows the choice of the most suitable material for the biosorption processes. The experimental results, obtained for Cu(II) ions biosorption on each biosorbent (algae biomass (AB), BC-320 and BC-550), at three different temperatures (10, 30 and 50 °C) were analyzed using Langmuir and Freundlich isotherm models, while pseudo-first order, pseudo-second order and intra-particle diffusions models were used to model the kinetic data. The biosorption of Cu(II) ions is best described by the Langmuir model and the pseudo-second kinetic model, regardless of the type of biosorbent. Such behavior is characteristic for the retention of metal ions on low-cost materials, and is explained in the literature using the concepts of molecular symmetry. The maximum biosorption capacity (qmax, mg/g) depends on the temperature, but also on the type of biosorbent, and follow the order: BC-320 < AB < BC-550. Using the experimental isotherms, the thermodynamic parameters (ΔG0, ΔH0 and ΔS0) for the biosorption of Cu(II) ions on each biosorbent were calculated. The analysis of the obtained values constitutes the main arguments in choosing BC-550 as the most effective biosorbent for the removal of Cu(II) ions from aqueous media.

COPPER ADSORPTION ONTO POMEGRANATE PEEL ACTIVATED CARBON AS A NEW ADSORBENT

Pomegranate peel-based activated carbon was prepared using phosphoric acid impregnation for removing copper ions from aqueous solutions. The activated carbon sample was characterized using N2 adsorption–desorption isotherms, SEM, FTIR, and Boehm titration. Batch adsorption experiments were performed as a function of initial pH, contact time, initial ion concentration and temperature. The metal adsorption was found pH dependent, with maximum adsorption occurring at an initial pH of 5.4. Langmuir, Freundlich and Temkin isotherms were used to analyze the equilibrium data at different temperatures. The Freundlich isotherm was considered to be the best model for representing Cu(II) adsorption data. The kinetic studies were analyzed using pseudo-first order, pseudo-second order and intraparticle diffusion models, with good fitting to the pseudo-second-order model. The adsorption behavior of the binary solution system Cu(II)-Cd(II) showed that the adsorbent has higher selectivity towards copper ions than cadmium ions.

Removal of benzotriazole derivatives by biochar: Potential environmental applications

Benzotriazole and its derivatives (BTAs) are commonly present in wastewater due to their extensive use in industrial processes, yet their removal is still unexplored. Here, we test the removal of these pollutants using two functionalised biochars, synthesised from wild plum (WpOH) and apricot (AsPhA) kernels. The aim of this work was to optimise the adsorption process against various BTAs (i.e., benzotriazole (BTZ), 4-hydroxy-1H-benzotriazole (OHBZ), 4-methyl-1H-benzotriazole (4 MBZ), 5-methyl-1H-benzotriazole (5 MBZ), 5-chloro-1H-benzotriazole (ClBZ), 5,6-dimethyl-1H-benzotriazole (DMBZ)), and determine the adsorption mechanisms at play, using real wastewater matrices. Batch studies showed that the optimal adsorption pH ranged between 4 and 6 for WpOH and AsPhA, respectively, and equilibrium was reached after 240 min. The kinetic models that best described the adsorption process were in the following order: Elovich model > pseudo-second order model > pseudo-first order model. The equilibrium data showed the highest correlation with the Freundlich isotherm, indicating multilayer adsorption. The maximum adsorption capacity obtained in mixtures was 379 mg/g on WpOH and 526 mg/g on AsPhA. The mechanistic work revealed that the BTAs became bound to the biochar primarily through H-bonding, n-π and π-π EDA interactions. In wastewater, obtained before and after conventional treatment, the concentration of OHBZ and BTZ was reduced by >40%, while the concentration of the other compounds studied fell below the detection limit (∼2.0–90 ng/L). Finally, using a Vibrio fischeri assay, we showed that adsorption onto AsPhA significantly reduced the relative toxicity of both raw and treated wastewater.

Investigation of adsorption equilibrium in the system of ammonium ions and a calcined sorbent from ash and slag waste of thermal power plants

A calcined sorbent from ash and slag waste of thermal power plants was used for water purification from ammonium ions. Experiments were carried out under static conditions at a temperature of 25±2 °С. The concentration of ammonium ions in the solution was measured by the spectrophotometric method according to the established graduation characteristic tested for convergence and correctness. The sorption process was studied at a sorbent dose of 1.0 g per 50 cm3 of the model solution taking the specific pore volume of the sorbent into account. For a solution with an ammonium ion content of 20 mg/dm3, the following modifications were carried out: the frequency of magnetic stirrer rotation was varied from 50 to 500 rpm; the pH of the solution – from 4 to 9; and the time to equilibrium – from 10 to 210 min. The time to equilibrium was 180 min. The effect of initial concentration of ammonium ions (2.0; 5.0; 20; 50 and 100 mg/dm3) in the solution on the adsorption process was studied under optimal sorption parameters. The adsorption equilibrium in the “ammonium ions–calcined sorbent” system was studied for the initial concentration of ammonium ions from 5 to 300 mg/dm3. Experimental data were processed using Langmuir and Freundlich adsorption isotherms. The maximum value of adsorption comprised 1.1251 mg/g. The experimental data were found to agree with the Langmuir theory. To describe the adsorption kinetics, the parameters of pseudo-first and pseudo-second order equations were determined. The highest convergence between the experimental and calculated data was achieved by the pseudo-first order model.

Utilization of Agricultural Waste as Low-Cost Adsorbents in Dye Wastewater Treatment: Kinetic and Thermodynamic Study

In recent years, the treatment of dye wastewater has attracted more attention because of its harmful impact on the environment. Therefore, dye wastewater should be treated using effective treatment methods, such as adsorption, which is widely employed to remediate many dyes from wastewater. This work studied the use of Laurus Nobilis Leaves (LNL) and sawdust (SD) as low-cost natural adsorbents to remediate reactive blue (RB) dye from synthetic wastewater under the influence of their dosages (0.5-5.5 g) for each, pH (3-9), and contact time (10-190 min). The experimental design, analysis of results, and optimization were conducted using Response Surface Methodology (RSM) based on Box-Behnken method (BBM) and the Minitab-Statistical program. The BET and FT-IR tests have been used to characterize these adsorbents, which show that SD-adsorbent includes more pore volume and surface area than LNL-adsorbent. The adsorption isotherms study revealed that Langmuir isotherm was a more fitted model than Freundlich model. Adsorption kinetic shows that the current adsorption process obeys the pseudo-second order model (R2=0.998) compared to the pseudo-first order model (R2=0.973) and the intraparticle diffusion model (R2=0.915). Thermodynamics study revealed that the present adsorption is endothermic, random irregularity at the solid-liquid, and a spontaneous nature. More than 60% of RB-dye removal efficiency was achieved at the optimal conditions, which were 5.5 g of SD-adsorbent, 0.8 g of LNL-adsorbent, pH 3, and 141 min of the contact time. The core results proved that the interaction effect of using multi-natural adsorbents was significant and cost-effective, providing considerable removal of dye from wastewater.

Comparison of kinetic study of the adsorption of bromothymol blue on activated Attapulgite clay and commercial activated carbon

This work is included studying the removal efficiency method of bromothymole blue (BTB) from industrial waste water by using thermally activated Attapulgite clay (ATC) and by activated carbon (AC) as adsorbent when applying adsorption technology. The most efficient dose obtained for the removal of BTB by AC and ATC is then using 20 mL of dye solution with 3*10-4 M concentration are 0.03 and 0.1 g respectively. The use of AC required 0.03g of AC to give % ads 95.97 while the use of o.1 g of ATC gave % ads. 91.71, The results gave a preference of the clay ATC to be used as a cheap and efficient adsorbent. Comparison of the adsorption efficiency of the Attapulgite clay with commercial activated carbon where carried out. The optimal conditions of the adsorption systems under study such as effect of dose, initial concentration, and temperature were investigated. Two isotherm models, Langmuir and Freundlich were fitted to the experimental data of adsorption. The thermodynamic Functions of the studied systems (∆Ho, ∆G°, ∆S°) were estimated. The results of the thermodynamic study showed that the forces controlling the adsorption process of the systems under consideration are physical in nature. The adsorption process is exothermic, occur spontaneously in the direction of connecting the dye to the clay surface, and forming less random system. The research also included achieving kinetic study by application of the pseudo first-order and pseudo second-order reaction models on the experimental data of the studied system, this indicted by the value of R2 (0.999) and the agreement between the experimental and calculated ( qe ) . The second order equation were better fitted to the experimental data of the system under consideration. In addition, the matching of the calculated qe value (34.843 mg/g) with the practical (33.821 mg/g) one sustain this results. The application of the intra-particle diffusion method showed that, the diffusion process of the adsorbed molecules into the pores present on the adsorbent surface is not the only mechanism driving the adsorption process in the studied reaction Kdiff.(mg.g‾¹.min‾½) = 0.893, R2 = 0.943.

Highly selective and reusable nanoadsorbent based on expansive clay-incorporated polymeric nanofibers for cationic dye adsorption in single and binary systems

Fabrication of nanoadsorbents with excellent adsorption capacity, selectivity, easy separation, and superior reusability for removing organic dyes from polluted water remains challenging. In this study, novel expansive clay/polyvinyl alcohol nanofibers (clay/PVA NFs) were fabricated as sheet-membranes using an electrospinning technique. The expansive clay with different ratios (5, 10, and 15 wt%) was incorporated into PVA NFs and comprehensively studied in terms of morphological and physicochemical characteristics. SEM images showed that incorporating the clay by electrospinning resulted in nanofibers with smaller diameters than the neat PVA NFs. The clay/PVA composite possesses high stability in aqueous media and a negatively charged surface at a pH higher than 4.1. The results showed that incorporating clay into PVA NFs improved the adsorption capacity for removal of crystal violet dye (CV) from single and binary systems. The incorporation of 5 % clay into the PVA NFs reduced diameter from 341 to 217 nm and increased its maximum adsorption capacity for the CV dye removal from 48.65 to 121.73 mg/g. The Redlich-Peterson and pseudo-first order models provided the best modeling of the experimental adsorption isotherm and adsorption kinetic data, respectively. The clay/PVA NFs exhibited outstanding reusability, with a removal efficiency for CV dye of 99.34 % after ten cycles of reuse with easily separated after adsorption. In addition, the clay/PVA NFs have good selectivity for separating CV dye from various binary dye systems. The selectivity of the clay/PVA to separate the CV dye from the binary dye systems of CV/methylene blue, CV/Coomassie brilliant blue, and CV /hematoxylin was 88.57 %, 90.92 %, and 97.24 %, respectively. Finally, excellent adsorption performance, good selectivity, high reusability, and ease of separation make clay/PVA NFs a promising adsorbent for CV dye removal from complex wastewater.

Enhanced removal of Pb (II) and Cd (II) ions from aqueous systems using coated magnetic nanoparticles in activated carbon derived from corncob waste

The study investigated the use of a cheap, high-efficiency, and eco-friendly adsorbent as an alternative to activated carbon coated Maghemite nanoparticles (γ-Fe3O4) for removing lead and cadmium ions from aqueous solutions. The Maghemite nanoparticles were synthesized using a sol-gel method. The characteristics of the adsorbent SEM, FT-IR, XRD and pHZPC, were analysed. The adsorption isotherm data were examined, and the data showed good fit with the Langmuir, Temkin and Freundlich isotherm models. The maximum adsorption capacity for Pb (II) and Cd (II) ions, as determined by the Langmuir isotherm, was found to be 127 mg/g and 100 mg/g, respectively. The kinetics of adsorption were studied using four kinetic models: pseudo-first order, pseudo-second order and Elovich model. Among these, the pseudo-second order kinetic model showed a good fit with high correlation values. Thermodynamic parameters such as the change in free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were calculated. These parameters indicated that the sorption of Pb (II) and Cd (II) ions is feasible, spontaneous, and endothermic. Overall, the results demonstrated that Maghemite nanoparticle coated activated carbon derived from agricultural biomass could be an attractive option for removing metals from industrial effluents. This alternative adsorbent offers advantages such as cost-effectiveness, high efficiency, and environmental friendliness in the removal of lead and cadmium ions from aqueous solutions.

Polypyrrole-Modified Nanocellulose Exhibits Superior Performance for Hg(II) Adsorption.

Cellulose, a kind of polymer containing abundant functional groups, has widespread use in the adsorptive removal of environmental pollutants. An efficient and environmental friendly polypyrrole (PPy) coating approach is employed to modify the agricultural by-product straw derived cellulose nanocrystal (CNC) into excellent property adsorbents for removing the heavy metal ion of Hg(II). The FT-IR and SEM-EDS results demonstrated that PPy is formed on the surface of CNC. Consequently, the adsorption measurements proved that the obtained PPy-modified CNC (CNC@PPy) possesses a remarkably enhanced Hg(II) adsorption capacity of 1095 mg g-1, owing to a plentiful functional group of doped Cl element on the surface of CNC@PPy by forming Hg2Cl2 precipitate. The results of the study suggest that the Freundlich model is more effective than the Langmuir model at describing the isotherms, while the pseudo-second order kinetic model is better suited to correlating with the experimental data compared to the pseudo-first order model. Further, the CNC@PPy exhibits an outstanding reusability, capable of maintaining 82.3% of its original Hg(II) adsorption capacity after five successive adsorption cycles. The findings of this work reveal a method to convert the agricultural by-product into high performance environmental remediation materials.

1H NMR study of kinetics of the Ni(II) and Zn(II) cations complex formation with 2-aza-5,10,15,20-tetraphenyl-21-carbaporphyrin

The methodology of 1H NMR study of the kinetics of the Ni(II) and Zn(II) cations complex formation with 2-aza-5,10,15,20-tetraphenyl-21-carbaporphyrin ([2-N, 21-CH]TPP I) was developed. The processes rate constants are determined using the pseudo-first and pseudo-second order models. It was shown that this methodology allows for identification and evaluation with high accuracy of the effects of donor–acceptor and solvation interactions that occur in the processes of the d-metal cations complex formation with the inverted tetrapyrrole macrocyclic ligands.

Characterization of β-Cyclodextrin Hybridized Diatomite as Potential Delivery Systems of Oxaliplatin and 5-Fluorouracil Drugs; Equilibrium Modeling of Loading and Release Kinetics

The present study involved the functionalization of diatomite’s bio-siliceous frustules with polymeric chains of β-cyclodextrin (β-CD/Di) to serve as advanced delivery structures for the anticancer drugs oxaliplatin (OXPL) and 5-Fluorouracil (5-Fu). The β-CD/Di carrier demonstrated significant loading capabilities, particularly at saturation (324.8 mg/g (OXPL) and 425 mg/g (5-Fu). Both OXPL and 5-Fu were loaded onto the β-CD/Di according to the kinetic properties of the traditional pseudo-first order model (R 2 > 0.90) and the isotherm assumptions of the classic Langmuir model (R 2 = 0.99). The density of occupied active sites on the β-CD/Di was found to be 38.76 mg/g and 88.19 mg/g during the loading process of OXPL and 5-Fu, respectively. The loading energies, which were less than 40 KJ/mol, confirmed the primary and significant influences of the physical mechanisms. The observed release profiles of OXPL and 5-Fu exhibited significant sustained and prolonged characteristics for up to 100 h. The release kinetic modeling and diffusion exponent values (>0.45) verified the release of OXP and 5-Fu based on non-Fickian transport features and the erosion/diffusion process. The β-CD/Di carrier significantly augmented the cytotoxic effects of OXPL and 5-Fu on HCT-116 cancer cell lines (OXPL (9.72% cell viability), and 5-Fu (4.17% cell viability)).

Copper and Zinc Mono- and Multi-Component Adsorption Kinetics in Tropical Soils: A Multivariate Analysis

ABSTRACT Copper and zinc are present in fertilizers, such as copper sulfate and zinc sulfate, and evaluation of their susceptibility to leaching is important, as well as their interaction and competitiveness in soil systems. This article aimed to evaluate the adsorption kinetics of copper and zinc in mono- and multi-component systems in an Oxisol, Inceptisol and Entisol Quartzipsamment using multivariate analyses. Physical, chemical, and mineralogical analyses of the soils were performed, and the batch method was used. Copper and zinc solutions containing the same concentrations of target and competitive ions were used in the sorption kinetics assays, and quantification was performed in an atomic absorption spectrophotometer. The pseudo first-order, pseudo second-order and Elovich models were fitted to the observed data. The results showed that the first principal component was related to the adsorption estimated by the pseudo first-order model and the adsorption properties of the soils. The second principal component was associated with charged adsorptive surfaces, such as clay and organic matter. In the dendrogram, Cluster 1 consisted of the Inceptisol, which contains minerals that enhance the adsorption of ions. Cluster 2 highlighted the similarities in ion adsorption between the Oxisol and Entisol Quartzipsamment, which have lower ion retention capacities.

Green Synthesis of Hydrogel-Based Adsorbent Material for the Effective Removal of Diclofenac Sodium from Wastewater.

The removal of pharmaceutical contaminants from wastewater has gained considerable attention in recent years, particularly in the advancements of hydrogel-based adsorbents as a green solution for their ease of use, ease of modification, biodegradability, non-toxicity, environmental friendliness, and cost-effectiveness. This study focuses on the design of an efficient adsorbent hydrogel based on 1% chitosan, 40% polyethylene glycol 4000 (PEG4000), and 4% xanthan gum (referred to as CPX) for the removal of diclofenac sodium (DCF) from water. The interaction between positively charged chitosan and negatively charged xanthan gum and PEG4000 leads to strengthening of the hydrogel structure. The obtained CPX hydrogel, prepared by a green, simple, easy, low-cost, and ecological method, has a higher viscosity due to the three-dimensional polymer network and mechanical stability. The physical, chemical, rheological, and pharmacotechnical parameters of the synthesized hydrogel were determined. Swelling analysis demonstrated that the new synthetized hydrogel is not pH-dependent. The obtained adsorbent hydrogel reached the adsorption capacity (172.41 mg/g) at the highest adsorbent amount (200 mg) after 350 min. In addition, the adsorption kinetics were calculated using a pseudo first-order model and Langmuir and Freundlich isotherm parameters. The results demonstrate that CPX hydrogel can be used as an efficient option to remove DCF as a pharmaceutical contaminant from wastewater.

Mesoporous biobased carbonaceous adsorbent for dye removal from water: Eutectic molten salts effect and adsorption mechanisms

Dye-polluted wastewater is released from various industries, such as textile and paint industries. Among different reclamation techniques, adsorption has been widely used for dye removal. Carbonaceous adsorbents, such as graphene, are among the most sought-after compounds for adsorption applications because of their high specific surface area and adjustable surface features. In this study, graphene-like carbon (GLC) was prepared from biomass as it is a facile and eco-friendly approach. Biomass-derived GLC was prepared by pyrolyzing waste wood in the presence of FeCl3/ZnCl2 as a eutectic binary mixture. Brunauer–Emmett–Teller (BET) and Raman analyses revealed that FeCl3 had a template effect during pyrolysis, whereas ZnCl2 acted as a pore former. Moreover, FeCl3 and ZnCl2 concentrations positively affected the BET value, regardless of the salt type. Further, waste wood-derived graphene-like carbon (WGLC) pyrolyzed at 900 °C with biomass: FeCl3: ZnCl2 at a ratio of 1:2:1 (WGLC-121) showed the highest specific surface area (2073.78 m2 g−1) and could remove >90 % of rhodamine B (RhB) and Congo red (CR) dyes. The pseudo-second order kinetic model showed a stronger correlation with the experimental data than the pseudo-first order model. While intra-particle diffusion was the rate-determining step in RhB adsorption, it did not influence CR adsorption. Further, the Freundlich model better explained the RhB (qmax = 633.86 mg g−1) and CR (qmax = 141.28 mg g−1) adsorption and revealed the superiority of WGLC-121 in dye removal compared to the previously reported adsorbents. The adsorption isotherm, energy, and thermodynamic parameters confirmed that the dyes were adsorbed through physisorption. Furthermore, the inter-molecular interaction between the RhB and CR molecules influenced the dye adsorption rate and isotherm. The findings of this study demonstrate the high potential of a binary mixture of FeCl3 and ZnCl2 for preparing carbonaceous adsorbents from waste wood to remove dyes from industrial wastewater.

Efficient removal of Mn2+ ions from aqueous solutions using apple pomace biochar

The increasing contamination of water resources is a severe environmental problem. Manganese is highly soluble in water, has adverse effects on the environment and human health during excessive exposure, and is difficult to remove. Biosorbents have been suggested to remove metals from aqueous solutions, therefore, apple pomace was utilized to prepare activated biochar (activated charcoal from apple pomace, ACAP). The biochar sample was characterized by X-ray fluorescence spectrometry, scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and Brunauer–Emmett–Teller analysis. The aim of this study was to use ACAP as an adsorbent to remove Mn2+ ions from aqueous solutions. Adsorption experiments were performed in the pH range 3.2–6.5, with various masses of ACAP biochar and Mn2+ ion concentrations. The results were evaluated using the pseudo-first order, pseudo-second order, general order, Elovich, and Webber and Morris kinetics models. All the models fitted the experimental results, the equilibrium time was 15 min, and the pseudo-second order model presented the highest constant (k2), indicating that chemosorption is an important mechanism in adsorption. The adsorption isotherm results were adjusted using different models, wherein the Langmuir and Temkin models exhibited the best fit to the experimental results. Adsorption experiments yielded a 97.5% removal rate of Mn2+ ions at pH 6.5 and <5% at pH 3.2, and the desorption of manganese in nitric acid (0.1 M) was 97.5%. Overall, apple pomace biochar is an efficient adsorbent for removing Mn2+ ions in aqueous media, and is applicable for treating water for human consumption.

Enhanced UV-light driven photocatalytic performance of magnetic CoFe2O4/TiO2 nanohybrid for environmental applications.

In this work, CoFe2O4/TiO2 nanostructure was prepared through a facile and effective solvothermal route for efficient use in the degradation of the Erionyl Red A-3G model pollutant under ultraviolet irradiation. Characterization analysis indicated the successful heterojunction among the precursors. The composite presented band gap value of 2.75eV, being smaller than that of the pristine TiO2, as well as mesoporous structure. The catalytic activity of nanostructure was investigated by employing a 22 factorial experimental design with 3 central points. The optimized reaction conditions were set as pH = 2 and catalyst dosage = 1.0gL-1 for an initial pollutant concentration of 20mgL-1. The prepared nanohybrid presented remarkable catalytic activity, reaching color removal efficiency of 95.39% after 15min, as well as total organic carbon (TOC) removal of 69.4% after 120min. The kinetic studies of TOC removal followed the pseudo-first order model, with a rate constant of 0.10min-1. Moreover, the nanostructure presented magnetic behavior, being easily separated from the aqueous medium through the use of a simple external magnetic field.

Synthesis and characterization of chitosan sheet modified by varied weight ratio of anatase (TiO2) nano mixture with Cr(VI) adsorbing

TiO2 and varied weight TiO2 incorporated Chitosan (CS–TiO2) were successfully prepared via photolysis method utilizing manual UV irradiation system with a maximum intensity wavelength 256 ​nm and 125 ​W power source to remove Cr(VI) from aqueous solution. The structure and morphology properties were characterized by utilizing XRD, Raman spectrum, BET, TEM and FESEM. The mechanism of Cr(VI) were investigated by XPS. The best conditions for removing Cr(VI) from the aqueous solution were investigated by examining the effects of adsorption parameters, including pH, contact time, catalyst dosage, dye concentration, and temperature. The Freundlich and Isotherm of Langmuir models were used to characterize the equilibrium data of Cr(VI) removal by CS-TiO2, and the pseudo-first order, pseudo-second order, and Elovich models were used to study the adsorption kinetics. By employing CS-TiO2 nano mixture adsorbents, the thermodynamics parameters showed an endothermic reaction and the spontaneous nature. The maximal adsorption capacity (qmax) for Cr(VI) sorption was 60 ​mg ​g−1. The reusability of the chitosan and TiO2 nano mixture combination was tested for a fifth cycle, and the results demonstrated that it was equivalent to other adsorbents. Thus, this present study recommends the choice of 30 ​mg of absorbent (5wt.% TiO2:CS) for removing Cr(VI) from aqueous solution.

Evaluation of microplastic contamination by metals in a controlled environment: A risk to be considered

The metal contamination and the degradation of polyethylene terephthalate (PET) due to human activities have contributed to the worsening of environmental problems in aquatic systems. Therefore, the study aimed to evaluate PET microplastic adsorption levels when exposed to high amounts of Ni, Cu and Co. The PET microplastic was characterized by scanning electron microscopy, Brunner-Emmet-Teller, porosimetry system, Barrett-Joyner-Halenda and Fourier transform infrared spectroscopy with attenuated total reflectance for evaluation of surface morphology, surface area, porosity, pore size and functional groups, respectively. The results showed that the surface area, the presence of macro and mesopores, and the functional groups influence the adsorption of metals on the surface of PET microplastic. The adsorption isotherms confirmed the presence of mesoporosity and macroporosity on the PET microplastic surface. The Freundlich and Langmuir models were used to study the adsorption capacity. The kinetics of adsorptions were interpreted using pseudo-first order and pseudo-second order models. The results indicated that the Langmuir isotherm and the pseudo-second order adequately described the adsorption of metals by the PET microplastic. The removal rates by the PET microplastic varied from 8 to 34% for Ni, 5 to 40% for Cu and 7 to 27% for Co after a period of 5 days. Furthermore, the adsorption was predominantly chemical and extremely fast, indicating that the presence of microplastics in the environment can lead to a rapid metal accumulation which elevates the hazards potential of microplastic in living beings.

Mann’s Cucumeropsis Seed Shell as an Oil Sorbent: Kinetic, Isotherm, and Thermodynamic Studies

Oil spill cleanup using agricultural wastes, which otherwise cause environmental contamination, has gained popularity. In this study, the feasibility of using Mann's cucumeropsis seed shell, a commonly found agricultural waste, as an oil spill mop, was investigated. To identify the surface characteristics of the seed shell, SEM and BET analyses were employed. Batch crude oil sorption tests were performed under various adsorption conditions to determine the effects of initial oil concentration, contact time, adsorption temperature, and adsorbent dosage. Kinetic study of the sorption process involved the pseudo-first order, pseudo-second order, Elovich, and intraparticle diffusion models. Isotherm analysis involved the Langmuir, Temkin, Freundlich, and Dubinin-Radushkevich isotherms. Additionally, the thermodynamic parameters for the sorption process were established. SEM analysis revealed the porous nature of the seed shell's surface. The BET surface area was 313.2 m²/g. The oil sorption process conformed best to the pseudo-first-order kinetics and Langmuir isotherm. The monolayer sorption capacity of the seed shell was 13.072 g/g. The sorption process was exothermic, with some order at the adsorbent–mixture interface. The study's findings demonstrate that Mann's cucumeropsis seed shell is a potent oil sorbent that is safe for the environment and can be enhanced for use in cleaning up oil spills.

A novel green synthesized magnetic biochar from white tea residue for the removal of Pb(II) and Cd(II) from aqueous solution: Regeneration and sorption mechanism

A novel biochar-based magnetic nanocomposite (GSMB) was prepared from white tea waste via green synthesis method. The sorption properties and regeneration of GSMB were studied using Pb(II) and Cd(II) to better understand its ability in heavy metal recovery. The adsorption kinetics data were modelled using pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion models, while Pb(II) and Cd(II) isotherms were modelled with Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models. Results showed that Pb(II) adsorption was well described by pseudo-second order while the Elovich model best described the Cd(II) adsorption trend, indicating the sorption of Pb(II) and Cd(II) onto GSMB were dominated by chemisoprtion rather than physisorption. Langmuir model gave the best fit to Pb(II) sorption, and the Cd(II) adsorption was well described by Temkin model. The maximum adsorption capacity of Pb(II) and Cd(II) onto GSMB were 81.6 mg/g and 38.6 mg/g, respectively. Scanning electron microscope coupled with energy dispersive x-ray, X-ray diffraction and Fourier transform infrared spectroscopy analyses revealed that iron oxides played a key role during adsorption process and the adsorption mechanisms include surface electrostatic attraction and surface complexation for both metals. Among the five regenerating agents studied, 0.1 M EDTA-2Na was favoured for the desorption of Pb(II) onto GMSB. The findings from the regeneration studies revealed ∼54% of Pb(II) adsorption capacity remained after three sorption-desorption cycles implying the adsorbent could potentially be further reused.