Sips Isotherm Research Articles

Utilizing Novel Lignocellulosic Material from Hart's-Tongue Fern (Asplenium scolopendrium) Leaves for Crystal Violet Adsorption: Characterization, Application, and Optimization.

In this work, a new lignocellulosic adsorbent was obtained and tested for crystal violet dye removal from water. The material was obtained from hart's-tongue fern (Asplenium scolopendrium) leaves after minimal processing, without chemical or thermal treatment. The surface of the material was characterized using a variety of techniques, including FTIR, SEM, and color analysis. The effect of various factors on the adsorption capacity was then investigated and discussed. The kinetic and equilibrium studies showed that the general-order kinetic model and the Sips isotherm are the most suitable to describe the adsorption process. The equilibrium time was reached after 20 min and the maximum calculated value of the adsorption capacity was 224.2 (mg g-1). The determined values for the thermodynamic parameters indicated physical adsorption as the main mechanism involved in the process. The Taguchi method was used to optimize the adsorption conditions and identify the most influential controllable factor, which was pH. ANOVA (general linear model) was used to calculate the percentage contribution of each controllable factor to dye removal efficiency. Analysis of all the results shows that hart's-tongue fern (Asplenium scolopendrium) leaves are a very inexpensive, readily available, and effective adsorbent for removing crystal violet dye from aqueous solutions.

Adsorptive efficiency of hull-based activated carbon toward copper ions (Cu2+) removal from aqueous solution: Kinetics, modelling and statistical analysis

Activated carbons represent powerful materials for water depollution. In this study, two carbon materials were synthesized by a simple and eco-friendly method using Neem and Hyphaene thebaica biomass waste. The material preparation aimed to reach high surface activity and low cost in order to develop an adsorbent for the removal of harmful substances from water, such as heavy metals. The prepared carbon materials were characterized using various techniques, including Brunauer-Emmett-Teller (BET) specific surface area, thermogravimetric analyses (TGA), inductively coupled plasma-optical emission spectroscopy (ICP-OES) and Fourier transform infrared spectroscopy (FT-IR). The adsorption of Cu (II) ions on activated carbon from Neem (CAN) and Hyphaene thebaica (CAH) hulls was systematically investigated using a batch method by varying several key operational parameters such as contact time, pH, adsorbent dose and the effect of concentration. The results obtained from the study indicated that the maximum uptake capacity was 277 mg/g for CAN and 210 mg/g for CAH at pH 5 after 15 min of equilibrium time in contact with 500 mg/L of initial concentration of copper ions solution. Marczewski-Jaroniec and Sips isotherm models fitted well the experimental data with high R2, adj-R2 and less value or errors analysis for either CAN or CAH. Besides, the kinetic study showed that the adsorption followed a pseudo-first-order model for CAN and a pseudo-second-order for CAH. Thus, this study shows that Neem and Hyphaene thebaica hulls represent a valuable biomass source for the production of activated carbon for heavy metal remediation.

Removal of Organic Matter from Tunisian Industrial Phosphoric Acid by Adsorption onto Purified Natural Illite/Kaolinite Clay: Kinetics, Isothermal and Thermodynamic Studies.

This work aims to use a green, economical and efficient adsorbent to remove organic matter from Tunisian industrial wet phosphoric acid (WPA: 52% P2O5). For this purpose, a natural and abundant clay is extracted from the Douiret, Tataouine deposit in southern Tunisia. This clay is being tested for the first time as an adsorbent in WPA medium. The raw clay and purified clay are analysed using standard analytical techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, and BET methods. The results show that the raw clay is a mixture of illite and kaolinite, with other mineral impurities, mainly quartz. Organic matter adsorption tests show that the purified clay exhibits greater effectiveness than raw clay. The parametric study with purified clay indicates that temperature, contact time, and clay dosage strongly influence organic matter adsorption. The highest adsorption occurs at 60 °C after 50 min, reaching 56% with 8 g of purified clay per kg of WPA. Among several recognised models, the pseudo-second-order kinetic model and the Sips isotherm model are the most suitable for modelling the experimental data. This study suggests that Douiret clay can be considered an effective, inexpensive and environmentally friendly adsorbent for eliminating organic matter in industrial phosphoric acid.

Ni(II) and Pb(II) Removal Using Bacterial Cellulose Membranes.

Bacterial cellulose (BC) is a highly crystalline nanosized material with a high number of active groups. This study focuses on the synthesis of BC membranes through fermentation, their characterization and application to remove Ni(II) and Pb(II) from wastewater by adsorption under different conditions. Four-day-grown BC membranes form three-dimensional nanofibril networks with a pH of 6.3 and a high cationic demand (52.5 μeq·g-1). The pseudo-second-order kinetic model and the Sips isotherm model best describe the adsorption of both metals. The intraparticle diffusion model of Ni(II) revealed a three-step mechanism of adsorption-plateau-adsorption, while Pb(II) adsorption followed a typical reducing-slope trend up to saturation. The highest removal of Ni(II) and Pb(II) was obtained at pH 4 with a BC dosage of 400 mg·L-1. The maximum adsorption capacities were 28.18 mg·g-1 and 8.49 mg·g-1 for Ni(II) and Pb(II), respectively, involving the total coverage of the material active sites. Thermodynamically, Ni(II) adsorption was exothermic, and Pb(II) was endothermic. The obtained values of sorption heat, activation and Gibbs' energy depicted a physisorption process. Ni(II) removal mechanism was ruled by crystallization on the metals adsorbed on the BC active groups, while Pb(II) was driven by the adsorption process, as shown by TEM images of the spent material.

Degradation of Aniline & Para- Chloroaniline from Water by Adsorption Coupled with Electrochemical Regeneration

Treatment methods for water-containing organics are gaining significant attraction in modern-day research. Amines are an important organic compound class encountered in industrial wastewater streams. The current research paper focuses on studying the adsorption behavior of aniline and parachloro-aniline using a graphite-based adsorbent, namely, Nyex-1000, and the subsequent regeneration of the adsorbent. To determine Nyex-1000's adsorption capacity, several parameters, including time, pH, and concentration, were assessed. Adsorption isotherms, kinetics, and used adsorbent regeneration were also investigated. The adsorption of aniline and parachloro-aniline was found to be quite rapid owing to its non-porous nature. Moreover, the low energy requirement makes the process quite economical due to the high electrical conductivity of the adsorbent. The adsorption data was fitted to Langmuir, Freundlich, Redlich Peterson, Sips, and Toth isotherm models. In aniline’s case, Langmuir and Parachloro-aniline Sips models gave the best fitting with the highest R2 value. A regeneration efficiency of 100% was observed in case of both aniline and parachloro-aniline by passing a charge of 5 and 10 coulombs per gram through the adsorbent bed 10 mm in thickness. Adsorption for parachloro-aniline was found to be 0.88 mg/g, and for aniline was found to be 0.40 mg/g. The reduction in adsorption capacity was minimal after several adsorption and regeneration cycles. This study found that spent adsorbent could be regenerated effectively through electrochemical regeneration.

Pectin hydrogels modified with montmorillonite: Case studies for the removal of dyes and herbicides from water

Hydrogels were synthesized with pectin and modified with montmorillonite for case studies involving the removal of dyes and herbicides from water. Methylene blue and 2,4-dichlorophenoxyacetic acid (2,4-D) were used as model pollutants. Fourier-transform infrared spectroscopy performed before and after the pollutant sorption studies enabled the identification of chemical groups in the structure of the hydrogels and interactions with each pollutant in the aqueous medium. Thermogravimetric analysis, differential thermogravimetry and differential scanning calorimetry were employed to determine thermal events in the polymeric networks of the hydrogels before and after pollutant sorption. Scanning electron microscopy was employed to evaluate the hydrogel morphologies before and after the sorption studies. The water diffusion mechanisms and point of zero charge in each hydrogel varied according to the type of aqueous medium. Moreover, the pollutant sorption capacity of the hydrogels varied as a function of the sorption time, pH and temperature of the aqueous solution as well as the initial concentration of the pollutant. The Redlich-Peterson and Sips isotherms had the best fit to the experimental data, indicating that the sorption of methylene blue and 2,4-D tends to occur by simultaneous multi-site interactions and the formation of a monolayer. The thermodynamic and kinetic data complemented the isotherm data and assisted in the definition of real-world application strategies. Composite hydrogels with lower montmorillonite content are potentially better removers of drugs, food dyes, sugar substitutes and herbicides from water compared to conventional hydrogels not modified with montmorillonite. Overall, these hydrogels could be reused for three successive cycles of sorption after the recovery with either hydrochloric acid or ethanol.

Dual-purpose magnetic κ-carrageenan/montmorillonite hydrogel for carrying and removal of tetracycline from aqueous medium

In this work, a novel magnetic adsorbent obtained via the conjugation of montmorillonite clay and κ-carrageenan was fabricated. The successful synthesis of adsorbent was confirmed by various analytical techniques, including Fourier transform infrared spectroscopy, X-ray diffraction, zeta potential measurements, scanning electron microscopy, and N2-adsorption/desorption isotherms. The synthesized material was used as a high-performance sorbent in the removal of tetracycline from aqueous media, and the influential parameters of the process were investigated. It showed high adsorption performance in a wide pH range of 4–11. A maximum adsorption capacity of 80.28 mg g−1 was obtained at 45 °C. Furthermore, the best-fitted kinetic model was found to be the pseudo-second-order model. Regarding two-parameter nonlinear isotherms, best fitting followed the order: Freundlich ≈ Redlich-Peterson > Temkin > Langmuir, which was not the same that was obtained using linear isotherm model regression (Langmuir ≈ Redlich-Peterson > Temkin > Freundlich). Among the different isotherm models, the isotherm data was best fitted to the nonlinear Sips isotherm model. Thermodynamic studies showed the endothermic and spontaneous nature of the adsorption process, as well as its random motion. A plausible mechanism includes hydrogen bonds as well as electrostatic and anion-π interactions as adsorption interactions between tetracycline and the functional groups (O-SO3- and OH–) on the surface of magnetic clay/biopolymer adsorbent.

Adsorptive Removal of Rhodamine B Dye from Aqueous Solutions Using Mineral Materials as Low-Cost Adsorbents

In this work, the potential adsorption abilities of mineral materials such as zeolite (Ze), halloysite (Ha), chalcedonite (Ch), and Devonian sand (DS) used as low-cost resources for the removal of Rhodamine B (RhB) from aqueous solutions were investigated in batch conditions. Adsorption kinetics and equilibrium and the effect of solution reaction (pH) were studied. Adsorption kinetic data were analyzed using two kinetic models: pseudo-first-order and pseudo-second-order models. Adsorption kinetics was better represented by the pseudo-second-order model. Equilibrium data were analyzed by the Freundlich, Langmuir, and Sips isotherms. The results show that equilibrium data fit well with the Freundlich equilibrium. Monolayer maximum adsorption capacities of RhB were assumed at 6.964, 4.252, 2.701, and 0.349 mg/g for Ze, Ha, Ch, and DS, respectively. Adsorption was strongly pH-dependent. The maximum RhB adsorption on all tested materials was observed at pH = 2.2 and decreased with further pH increase. The results of these investigations suggest that natural materials represented by certain minerals have a good potential for the removal of Rhodamine B from aqueous solutions.Graphical

Magnetic zeolite@β-cyclodextrin-gum Arabic nanocomposite for adsorptive removal of levofloxacin

This study reports the synthesis, characterisation, and application of magnetic zeolite@β-cyclodextrin-gum Arabic (MZ@β-CD-GA) adsorbent for adsorptive removal of levofloxacin (LEV). The kinetic studies confirmed that the adsorption of LEV was described by pseudo-second order and Elovich models. Furthermore, Langmuir and Sips isotherms confirmed a monolayer adsorption process. While the Dubinin-Radushkevich model confirmed that the mechanism was controlled by chemisorption (Ea > 20 kJ/mol). Furthermore, the maximum Langmuir adsorption capacity of MZ@β-CD-GA nanocomposite for sorption of LEV was 150 mg/g. The negative values of ΔG° and positive ΔH° suggested that the adsorption process was feasible, spontaneous, and endothermic. The applicability of MZ@β-CD-GA material was evaluated for the laboratory-scale treatment of real water samples spiked with known concentrations of LEV, and the removal efficiencies ranged from 89-97.8%. Findings from this study indicate that MZ@β-CD-GA material was commercially feasible and can be used as an alternative adsorbent in antibiotic decontamination.

Adsorption kinetics and equilibrium performance of Di-n-butyl phosphate on XAD-4 and XAD-7 from alkaline medium

ABSTRACT The present study investigates the feasibility of adsorption method for the removal of Di-n-butyl phosphate from sodium carbonate solution on adsorbents such as XAD-4 and XAD-7. The fundamental aspects of equilibrium and kinetics of adsorption have been studied. The experimental equilibrium data were fitted well with Sips isotherm, and maximum solid uptake capacity for monolayer coverage (qm) was found to be 0.363 × 10−3 mol/g and 0.385 × 10−3 mol/g for XAD-4 and XAD-7, respectively. The adsorption kinetics was well described by the pseudo-first-order model, and estimated first-order rate constant values were found to be 0.041 min−1 for XAD-4 and 0.027 min−1 for XAD-7. The transport mechanism of solute from the bulk solution to adsorbent was described in detail with suitable mathematical model, and experimental kinetic data were superimposed on numerically solved concentration profiles to calculate external mass transfer coefficient (kf) and effective diffusivity (De). The values of kf and De were estimated as 4.632 × 10−7 m/s and 8.849 × 10−13 m2/s, respectively, for XAD-4, whereas for XAD-7, the values were found to be 2.132 × 10−6 m/s and 1.389 × 10−12 m2/s. XAD-7 is found to have slightly better adsorption capacity and transport characteristics than XAD-4.

Fabrication of versatile Ag-P/Ppy core-shell nanocomposite: Adsorption efficacy for chromium (VI) removal and assessment of antioxidant and antibacterial activities

This study reports the synthesis, via in-situ chemical oxidative polymerisation, of conducting polymer-based silver phosphate Polypyrrole (Ag-P/Ppy) core-shell nanocomposite, exhibiting antioxidant and antibacterial characteristics, for the adsorption of chromium (VI) ions from aqueous solutions. Filtering away Cr (VI) ions efficiently also improves the filtered water with antibacterial and antioxidant properties. P-XRD, ATR-FTIR, FESEM, EDAX, TEM, zeta potential, TGA, and BET studies characterized Ag-P/Ppy. The core-shell nanostructure of Ag-P/Ppy was determined by TEM micrographs, which indicated the presence of an Ag-P core and a Ppy shell. pH value, adsorbent dose, stirring rate, contact time, and Cr (VI) pollutant concentration, were investigated as potential influencing factors. At pH 2, 99.4 % of Cr(VI) was removed in 55 min. The adsorption kinetics was effectively depicted by a pseudo-second-order kinetics model, signifying that chemisorption played a momentous role in the total adsorption capacity. Freundlich, Temkin, Redlich-Peterson, and Sips isotherm models were fitted to adsorption data. Temkin and Redlich-Peterson models have a higher (0.99) correlation coefficient than Freundlich (0.95) and Sips (0.98). The maximum adsorption capacity (qm) evaluated using the Sips model was 138.5 mg g−1, which was quite close to the 130.55 mg g−1 value obtained from experiments. The manufactured nanocomposite showed 91.2 % radical scavenging activity in a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. Antibacterial activity of the Ag-p/Ppy core-shell nanocomposite contrary to gram-positive (S. aureus) and gram-negative (P. aeruginosa, E. coli, and K. pneumoniae) bacteria was assessed by means of the agar well diffusion technique. Compared to the positive control, it inhibited S. aureus, E. coli, K. Pneumoniae, and P. Aeruginosa by 82.35 %, 79.5 %, 63.63 %, and 76.7 % respectively. Therefore, the Ag-P/Ppy core-shell nanocomposite has the potential as a potent and versatile adsorbent for the exclusion of Cr (VI) ions from water.

Preparation of sodium zinc phosphate/polyaniline nanocomposite for Cr(VI) and eriochrome black T adsorption from water

In this study, ultrasound physical mixing of polyaniline (PAni) and sodium zinc phosphate (NaZnP) materials resulted in the synthesis of a new nanocomposite (NaZnP/PAni). Samples were physicochemically characterized via different analytical techniques. The X-ray diffraction pattern indicated the synthesis of hydrated sodium zinc phosphate (Na6(ZnPO4)6.8 H2O) with an average crystallite size of 40.8 nm. After physical mixing with PAni, the crystallite size of the resulting composite was reduced to 36 nm. Scanning electron microscopy (SEM) revealed that the nanocomposite was formed by the deposition of NaZnP nanospheres over PAni nanorods. The adsorption efficiency of the composite was monitored using an azo dye (eriochrome black T (EB)) and hexavalent chromium (Cr(VI)). The optimization of the effects of operating parameters (pH, NaZnP/PAni dosage, starting pollutants concentration, and reaction time) on the removal efficiency were examined using the central composite design (CCD). The predicted removal efficiencies under the optimum conditions were 93 % and 98 % for EB and Cr(VI), respectively. The adsorption kinetics modeling reveals that the pseudo-second-order describes the uptake of Cr(VI) and EB. Equilibrium data fitted well with the Redlich-Peterson and Sips isotherm models. The highest retention capacity of NaZnP/PAni was 234 mg/g for EB and 231 mg/g for Cr(VI). Consequently, the developed NaZnP/PAni nanocomposite could be applied to remove heavy metals and dyes from wastewater with great efficiency.

Activated charcoal modified BaFe12O19 powder: a recyclable magnetic adsorbent for removal of methyl blue dye from aqueous solutions

ABSTRACT Use of sophisticated adsorbent materials to clean harmful dye-contaminated water is rapidly gaining popularity. Among different adsorbent, magnetic ferrites based adsorbent are gaining much attention because of their easy recyclability. In this current work, activated charcoal (AC) modified magnetic BaFe12O19 (BaM) ferrite-based novel adsorbent (BaM-AC) powder was synthesised through a sol-gel combustion route. As a model dye pollutant, methyl blue (MB) was used to estimate the adsorption efficiency of BaM-AC adsorbent. X-ray diffraction (XRD) was utilised to analyse pure BaM and BaM-AC powder phases. Fourier transform infrared spectroscopy (FTIR), Brunauer, Emmett and Teller (BET), vibrating sample magnetometer (VSM) and field emission scanning electron microscope (FESEM) were also used for the characterisation of prepared adsorbents. The surface area of BaM-AC powder determined by BET was 5.93 m2 g−1. The BaM-AC adsorbent has a saturation magnetisation (Ms) of 56.8 emu g−1 and a coercive field (Hc) of 5176 Oe. Microstructural analysis showed the porous morphology of the material. In-depth studies with BaM-AC powder investigated how pH, adsorbent dose, adsorption period, MB dye concentration, and effect of temperature affected MB dye adsorption. Conferring to the outcomes of the MB-adsorption experiment, the equilibrium was reached after around 45 minutes. Pseudo-second-order kinetics and the Sips isotherm model govern the adsorption process. BaM-AC powder exhibited a good recyclability up to five-regeneration cycle. These outcomes suggest that the composite material has the potential to serve as an effective adsorbent for dye-containing wastewater treatment.

Porous silica composites as efficient adsorbents for dye removal from aqueous solution

This study aimed to analyze the feasibility of removing Alizarin red S (ARS) used as model pollutant from aqueous solutions using the preparative porous silica composites (PSCs) as adsorbents which were prepared via hydrothermal approach. The physicochemical properties of materials were characterized by means of Transmission electron microscope (TEM), Scanning electron microscope (SEM), Energy dispersive spectrometer (EDS), Brunauer-Emmett-Teller (BET) method, Barret-Joyner-Halenda (BJH) method, Fourier Transform Infrared Spectrometer (FTIR) and X-Ray Diffractometer (XRD). PSCs possessed the specific surface area were 731.6 m2/g, 420.9 m2/g, 294.6 m2/g, respectively. The presence of silica structures was confirmed by FTIR spectra. In order to confirm efficiency of composites as adsorbents and reveal adsorption mechanism, the impacts of pH, contact time, initial ARS concentration, temperature on adsorption were conducted. The adsorption experiment results showed that the adsorption efficiency of ARS onto PSC-3 was better than that of PSC-1 and PSC-2 at pH = 11. Furthermore, the adsorption kinetic models, isotherm models and thermodynamic model were analyzed for comprehensive adsorption process. The maximum adsorption capacity of PSC-3 for ARS was 43.1 mg/g. The pseudo-second-order kinetic model and Sips isotherm model were more suitable for experimental results. The adsorption process was endothermic according to the adsorption thermodynamic model. The free energy of adsorption required for ARS onto PSCs was less than 8 kJ/mol, indicating physical adsorption. What’s more, PSC-3 possessed advantages of higher adsorption capacity and shorter equilibration time. Overall, these results made it potentially applicable as an effective adsorbent for ARS dye from effluent.

The application of Rumex abyssinicus based activated carbon for Brilliant Blue Reactive dye adsorption from aqueous solution

The environmental pollution and human health impacts associated with the discharge of massive dye-containing effluents necessitate a search for cost-effective treatment technology. Therefore, this research work is conducted with the objective of investigating the potential of Rumex abyssinicus-derived activated carbon (RAAC) for the adsorption of Brilliant Blue Reactive (BBR) dye from aqueous solutions. Chemical activation with H3PO4 followed by pyrolysis was used to prepare the adsorbent. Characterization of the developed adsorbent was done using proximate analysis, pH point of zero charge (pHpzc), scanning electron microscope (SEM), Fourier transform infrared spectrometer (FTIR), Brunauer, Emmett, and Teller (BET), and X-ray diffraction (XRD). The experimental design and the effect of independent variables including pH (2, 6, and 10), initial dye concentration (50, 100, and 150 mg/L), adsorbent dosage (0.05, 0.1, and 0.15 g/100 mL), and contact time (20, 50, and 80 min) were optimized using the response surface methodology (RSM) coupled with Box Behnken design (BBD). The analysis results revealed the exitance of high specific surface area of 524 m2/g, morphological cracks, and the presence of multiple functional groups like –OH, C=C, alkene, and amorphous structure. Maximum removal efficiency of 99.98% was attained at optimum working conditions of pH 2, contact time of 50 min, dye concentration of 100 mg/L, and adsorbent dosage of 0.15 mg/100 mL, reducing the pollutant concentration from 100 to 0.02 mg/L. Evaluation of the experimental data was done using Langmuir, Freundlich, Temkin, and Sips isotherm models, in which the Langmuir model was found to be the best fit with the experimental data at R2 0.986. This shows that the adsorbent surface is homogeneous and mono-layered. Furthermore, the kinetic study confirmed that the pseudo second-order model best describes the experimental data with R2 = 0.999. In general, the research work showed that the low cost, environmental friendliness and high adsorption capabilities of the activated carbon derived from Rumex abyssinicus could be taken as an effective nt for the removal of BBR dye from aqueous solutions.

Adsorption properties of boron nitride: A promising material for depollution applications

The interest in boron nitride (BN) materials has progressively increased due to their special properties such as high chemical stability and non-toxicity. The synthesis of the BN-based materials, starting from boric acid, urea (BN-u) and boric acid and melamine (BN-m) was presented. The obtained materials were characterized by BET, IR Spectroscopy, DR UV-Vis analysis, and Scanning Electron Microscopy (SEM). The synthesized BNs have a high surface area (538.0 m2/g for BN-u and 994 m2/g for BN-m) and large pore volume. However, even the material obtained starting from melamine presents a large pore volume, the pore size is higher from BN obtained from urea making it suitable for dye adsorption from wastewater. For this purpose, its performances in adsorption of Brilliant Blue FCF dye, as a model for dye molecules, were studied. The maximum adsorbed quantity of 24.8 mg/g was calculated based on Sips isotherm. The materials were also tested for CO2 adsorption, with promising results.

Clean water production from plastic and heavy metal contaminated waters using redox-sensitive iron nanoparticle-loaded biochar

The unceasing release of tiny plastics (microplastics and nanoplastics) and their additives, like metal ions, into the aquatic systems from industries and other sources is a globally escalating problem. Their combined toxic effects and human health hazard are already proven; hence, their remediation is requisite. This study utilised the nano-zerovalent iron-loaded sugarcane bagasse-derived biochar (nZVI-SBC) for simultaneous removal of Nanoplastics (NPs) of different functionality and size along with metal ions (Ni2+, Cd2+, AsO43−, and CrO42−). Batch and column experiments were conducted, and the results showed an efficient removal of contaminants with maximum sorption of carboxylate-modified NPs of size 500 nm (qmax = 90.3 mg/g) among all three NPs types. Significant removal was observed in Cd2+ in case of cations and CrO42− in case of anions with qmax = 44.0 and 87.8 mg/g, respectively. Kinetics and the isotherm modelling better fitted the pseudo-second-order kinetic model and Sips isotherm model, respectively for both NPs and metal ions. The designed material worked well in pH range of 4–8, ionic strength 1–20 mM and in complex aqueous matrices, with >90% removal. FTIR, zeta potential and the imaging analysis of the reaction precipitates confirmed the electrostatic attraction, pore retention and complexation as the potential mechanisms for removing NPs, whereas, XPS studies confirmed the reduction co-precipitation and surface complexation as the possible mechanism for removing metal ions. High values of attachment efficiency factor calculated from colloidal filtration theory (CFT) validated the experimental results and justified the high sorption of carboxylate modified 500 nm NPs particles. The synthesized material successfully removed both NPs of varying size and functionality and metal ions simultaneously with significant efficacy in complex environmental samples proving the broad applicability of material in realistic environmental conditions and different types of water treatment processes.

Effective removal of cesium by ammonium molybdophosphate–polyethylene glycol magnetic nanoparticles

This study synthesizes a new adsorbent composite for the removal of Cs ions from waste effluents. The adsorbent is composed of polyethylene glycol-decorated ammonium molybdophosphate magnetic Fe3O4 nanoparticles (PEG–AMP MNs) and is prepared via coprecipitation by grafting ammonium phosphomolybdate onto the surface of Fe3O4 and coprecipitation with polyethylene glycol. The physical and chemical structure of the PEG–AMP MNs was investigated using various spectroscopic and analytical techniques, revealing that Fe3O4 was tightly bound to the AMP particles and that the composites exhibited superparamagnetic behavior. The Cs+ adsorption behavior of the adsorbent was investigated in a wide range of pH values and temperatures, using multiple Cs+ contact times and initial Cs+ concentration, and with interference from additional ionic species. The adsorbent achieved 99.8% removal of Cs+ in the solution pH range of 1–12 and maintained its stability after adsorption. Interfering ions had little effect on the amount of Cs+ adsorbed. The experimental data were fitted using Langmuir, Freundlich, Redlich-Peterson and Sips isotherms pseudo-first-order and pseudo-second-order kinetic models. The results showed that the adsorption data fitted well with pseudo-second-order kinetics and the Langmuir isotherm model, with a maximum adsorption capacity of 53.89 mg g−1 and equilibrium reached within 20 min. Thermodynamic experiments showed the adsorption process to be inherently endothermic. The mechanism of Cs+ adsorption by PEG–AMP MNs is proposed to primarily be a combination of weak electrostatic attraction and ion exchange between NH4+ and Cs+. More importantly, the encapsulation of a magnetic carrier allows for the efficient separation and recovery of Cs+ after adsorption.

Adsorption of chloroquine, propranolol, and metformin in aqueous solutions using magnetic graphene oxide nanocomposite.

The work proposes the application of a nanocomposite formed by graphene oxide and magnetite to remove chloroquine, propranolol, and metformin from water. Tests related to adsorption kinetics, equilibrium isotherms and adsorbent reuse were studied, and optimization parameters related to the initial pH of the solution and the adsorbent dosage were defined. For all pharmaceuticals, adsorption tests indicated that removal efficiency was independent of initial pH at adsorbent dosages of 0.4 g L-1 for chloroquine, 1.2 g L-1 for propranolol, and 1.6 g L-1 for metformin. Adsorption equilibrium was reached within the first few minutes, and the pseudo-second-order model represented the experimental data well. While the equilibrium data fit the Sips isotherm model at 298 K, the predicted maximum adsorption capacities for chloroquine, propranolol, and metformin were 44.01, 16.82, and 12.23 mg g-1, respectively. The magnetic nanocomposite can be reused for three consecutive cycles of adsorption-desorption for all pharmaceuticals, being a promising alternative for the removal of different classes of pharmaceuticals in water.

Biodiesel Production Using Palm Oil with a MOF-Lipase B Biocatalyst from Candida Antarctica: A Kinetic and Thermodynamic Study

This research presents the results of the immobilization of Candida Antarctica Lipase B (CALB) on MOF-199 and ZIF-8 and its use in the production of biodiesel through the transesterification reaction using African Palm Oil (APO). The results show that the highest adsorption capacity, the 26.9 mg·g−1 Lipase, was achieved using ZIF-8 at 45 °C and an initial protein concentration of 1.20 mg·mL−1. The results obtained for the adsorption equilibrium studies allow us to infer that CALB was physically adsorbed on ZIF-8 while chemically adsorbed with MOF-199. It was determined that the adsorption between Lipase and the MOFs under study better fit the Sips isotherm model. The results of the kinetic studies show that adsorption kinetics follow the Elovich model for the two synthesized biocatalysts. This research shows that under the experimental conditions in which the studies were carried out, the adsorption processes are a function of the intraparticle and film diffusion models. According to the results, the prepared biocatalysts showed a high efficiency in the transesterification reaction to produce biodiesel, with methanol as a co-solvent medium. In this work, the catalytic studies for the imidazolate, ZIF-8, presented more catalytic activity when used with CALB. This system presented 95% biodiesel conversion, while the biocatalyst formed by MOF-199 and CALB generated a catalytic conversion percentage of 90%. Although both percentages are high, it should be noted that CALB-MOF-199 presented better reusability, which is due to chemical interactions.