Positive ΔS Research Articles

EFFECTIVE ADSORPTION OF TETRACYCLINE WITH Co3O4/Fe3O4 BIMETALLIC NANOPARTICLES

In the present study cobalt oxide/iron oxide bimetallic nanoparticles (Co3O4/Fe3O4 NPs) were synthesized by chemical coprecipitation method. The synthesized Co3O4/Fe3O4 NPs were characterized by SEM and XRD analysis. The synthesized nanoparticles were used as an adsorbent for the removal of a kind of antibiotic as Tetracycline (TC) from aqueous solutions. According to characterization results, small plate-like structures and agglomerated irregular spherical nanosized particles (101.85 ± 15.04 nm) were formed. The XRD data confirmed the structure of synthesized adsorbent was Co3O4/Fe3O4. The optimum tetracycline adsorption conditions were determined as the initial pH of solution 9.0, temperature 55°C, and adsorbent concentration 3.0 g/L. A linear increase was observed in equilibrium uptakes of TC with the increasing the initial antibiotic concentrations. The experimental equilibrium data was modelled with Langmuir and Freundlich isotherm models. The experimental equilibrium data was the best agreement to the Langmuir isotherm model. The maximum monolayer coverage capacity of Co3O4/Fe3O4 NPs for TC adsorption was found to be 149.26 mg/g at 55°C optimum temperature. The experimental kinetic adsorption data were defined as the best agreement with the pseudo-second-order kinetic model. Weber Morris mass transfer modelling results showed that both the film (boundary layer) and intra-particle diffusion were effective in the adsorption process. The thermodynamic studies suggested that the adsorption process was endothermic, spontaneous and the positive ΔS value indicated increased disorder at the solid-solution interface during the adsorption. Moreover, the synthesized adsorbent showed high adsorption efficiencies at the end of seven sequence usages.

Analysis of Temperature-Dependent H/D Exchange Mass Spectrometry Experiments.

H/D exchange (HDX) mass spectrometry (MS) is a widely used technique for interrogating protein structure and dynamics. Backbone HDX is mediated by opening/closing (unfolding/refolding) fluctuations. In traditional HDX-MS, proteins are incubated in D2O as a function of time at constant temperature (T). There is an urgent need to complement this traditional approach with experiments that probe proteins in a T-dependent fashion, e.g., for assessing the stability of therapeutic antibodies. A key problem with such studies is the absence of strategies for interpreting HDX-MS data in the context of T-dependent protein dynamics. Specifically, it has not been possible thus far to separate T-induced changes of the chemical labeling step (kch) from thermally enhanced protein fluctuations. Focusing on myoglobin, the current work solves this problem by dissecting T-dependent HDX-MS profiles into contributions from kch(T), as well as local and global protein dynamics. Experimental profiles started off with surprisingly shallow slopes that seemed to defy the quasi-exponential kch(T) dependence. Just below the melting temperature (Tm) the profiles showed a sharp increase. Our analysis revealed that local dynamics dominate at low T, while global events become prevalent closer to Tm. About half of the backbone NH sites exhibited a canonical scenario, where local opening/closing was associated with positive ΔH and ΔS. Many of the remaining sites had negative ΔH and ΔS, thereby accounting for the shallowness of the experimental HDX-MS profiles at low T. In summary, this work provides practitioners with the tools to analyze proteins over a wide temperature range, paving the way toward T-dependent high-throughput screening applications by HDX-MS.

Targeting nucleic acid with a bioactive fluorophore: Insights from spectroscopic and calorimetric studies

The Schiff base (H2SALNN) (N,N′-bis(4-methoxy-salicylaldehyde)azine) has been designed to develop a DNA targeted fluorescent probe. The H2SALNN was synthesized and geometry optimized by DFT/B3LYP. The interaction of H2SALNN with Calf thymus DNA (CT-DNA) was studied by spectroscopic and calorimetric techniques. The compound was found to bind with CT-DNA through groove binding mode. From isothermal calorimetry (ITC) titration experiment, the binding constant between the compound and DNA was estimated to be (1.52 ± 0.03) × 105 M−1. The negative ΔG0 and positive ΔS0 values obtained from the calorimetric study confirmed the spontaneity of the binding of H2SALNN with DNA. Analysis of thermodynamic parameters indicated that the process of interaction of H2SALNN with DNA is entropy driven.

Adsorption of methylene blue onto natural Saudi Red Clay: isotherms, kinetics and thermodynamic studies

The current work investigates the adsorption behavior of methylene blue (MB) from aqueous solution using natural Saudi Red Clay (SRC) adsorbent. The surface characteristics of the adsorbent were investigated using surface area measurements (SBET), Scanning Electron Microscopy (SEM), X-ray florescence (XRF) and Fourier-Transform Infrared Spectroscopy (FTIR) and x-ray diffraction (XRD). Various process parameters such as pH, adsorbent dosage, initial dye concentration, contact time and temperature were investigated. MB removal efficiency was noticed to increase with increasing adsorbent dosage while the effect of pH was noticed to be insignificant for the pH range studied. Applying the Langmuir isotherm fitting to the experimental data, a maximum adsorption capacity was found to be 50.25 mg g−1 of clay at 298 K. Pseudo-first-order and pseudo-second-order models were applied to the experimental data to study the kinetics of the process. Pseudo-second-order model fitted well with the experimental as compared to the pseudo-first order model. The spontaneous and endothermic nature of the adsorption process was revealed by studying the thermodynamic parameters of the system. The positive ΔS° value indicates the affinity of MB molecules to the adsorbent surface. Re-usability/recycling study showed that this material can be successfully reused at least four times in this study without significant loss in the adsorption capabilities.

Preparation and utilization of cigarette filters based activated carbon for removal CIP and SDS from aqueous solutions

The smoked cigarette filters were used to prepare high-surface-area activated carbons by KOH activation. The highest BET specific surface area of cigarette-filters-based activated carbon (CFAC) was 2726 m2·g−1 obtained at the activation parameter of carbonized materials/KOH = 1:5 and activation temperature of 900 °C, which could concluded that smoked cigarette filters were excellent raw materials for preparation activated carbons. The ciprofloxacin (CIP) and Sodium dodecyl sulfat (SDS) adsorption isotherms, adsorption kinetics and adsorption thermodynamics from aqueous solution using cigarette filters based activated carbon were investigated. The results indicated that Langmuir model and pseudo-second-order models were suitable to describe the CIP and SDS adsorption process of CFAC. More negative standard free energy (ΔG) and positive entropy change (ΔS) of CIP adsorption with increasing temperature indicated the spontaneous nature and increasing randomness of the CIP adsorption process. While More positive ΔG and negative ΔS of SDS adsorption indicated the non-spontaneous processes. The both positive enthalpy change (ΔH) indicated endothermic of CIP and SDS adsorption process.

Innovative spherical biochar for pharmaceutical removal from water: Insight into adsorption mechanism

In this study, we developed an innovative spherical biochar with high porosity and excellent paracetamol (PRC) adsorption capacity. The optimal pyrolysis temperatures for the preparation of spherical biochar (derived from pure glucose) and non-spherical biochar (from pomelo peel wastes) were obtained at 900 °C and 700 °C, respectively. Various advanced techniques were applied to characterize the prepared biochars. Spherical and non-spherical biochars exhibited large specific surface area (1292 and 1033 m2/g) and high total pore volume (0.704 and 1.074 cm3/g), respectively. The adsorption behavior of PRC onto two biochars was conducted utilizing batch experiments. Results demonstrated that the adsorption process was slightly affected by the change of solution pH (2–11) and addition of NaCl (0.05–1.0 M) and was able to achieve fast equilibrium (∼120 min). The maximum adsorption capacity of spherical biochar (286 mg/g) for PRC was approximately double that of non-spherical biochar (147 mg/g). The signal of thermodynamic parameters was negative ΔG° and ΔH° values, but positive ΔS° value. The adsorption mechanism consisted of pore-filling, hydrogen bonding formations, n-π and π-π interactions, and van der Waals force. The adsorption capacities of two biochars were insignificantly dependent on different real water samples containing PRC. Consequently, the biochars can serve as a green and promising material for efficiently removing PRC from water.

A nano-spectral study of charge transfer complexes to alizarin dye with electronic acceptors (TiO2)

The research involves the preparation of the nano-accepters, titanium dioxide (TiO2). It is diagnosed by different techniques such as IR, AFM, SEM, XRD and EDX, which illustrated the topographic features and features of the nano-crystalline prepared in terms of crystalline level, size of minute, pore shape, and elements analysis and et al. The study also includes a spectroscopic study of the transfer complexes of the charge using nano-TiO2 as the accepter’s electron with the alizarin dye extracted as donor electrons using absolute ethanol as a solvent. The Bensi-Hildebrand equation is applied to calculate the equilibrium constant and the molecular absorption coefficient of the resulting complex. The linear relationship resulting from the application of the equation showed that the forward ratio of the talent to the receiver is 1: 1. The effect of temperature change at the range (293-313 °K) was study on the equilibrium constants calculated from the Bensi-Hildebrand equation and used in the calculation of thermodynamic functions ΔH°, ΔS° and ΔG°. Negative values ​​ΔG° showed that the reaction was automatic and the positive values ​​ΔH° Indicate that the interaction of the composition of the complex is endothermic, while the positive values ​​ΔS° are indicative of the random reaction. The stability energy of the complex complexes is calculated and is equal to (2.24 eV) as well as the calculation of the ionization Potential and the dissociation energy of the excitation state of these complexities and other physical properties. The kinetics of the transition of the prepared charge complexes were studied in the absolute ethanol solvent. The results of the study showed that the kinetics of the formation and decomposition of the complexes are first order.

Design and synthesis of a sulphur containing Schiff base drug: DNA binding studies and theoretical calculations

The Schiff base compound MTA ((E)-5-methyl-N'-((5-methylthiophen-2-yl)methylene)-1H-pyrazole-3-carbohydrazide) derived from 2-thiophenecarboxaldehyde and 5-methylpyrazole-3-carbohydrazide has been designed to develop new sulphur containing DNA targeted molecule. The MTA has been characterized by elemental analyses, 1H-NMR, single crystal X-ray diffraction studies as well as by geometry optimization of using DFT/B3LYP. The interaction of MTA with Calf thymus DNA (CT-DNA) was studied by spectroscopic and calorimetric techniques. The synthesized compound was found to bind with CT-DNA through groove binding mode, and the binding constant was estimated to be (4.15 ± 0.08) × 104 M−1. The negative ΔG0 and positive ΔS0 values obtained from the calorimetric technique confirmed the spontaneity of the binding of MTA with DNA.Communicated by Ramaswamy H. Sarma

Adsorptive Removal of Copper Ions from Polluted Water Using Sorbents Derived from Cordia dichotoma, Albizia thompsonii and Polyalthia cerasoides Plants

Three different activated carbons as effective adsorbents were prepared by digesting the stems of Cordia dichotoma, Albizia thompsonii and Polyalthia cerasoides plants in conc. H2SO4 for Cu2+ removal from wastewater. The sorption natures of these sorbents are optimized with respect to various physico-chemical characteristics for the maximum Cu2+ removal using simulated waters. Cordia dichotoma (CDAC), Albizia thompsonii (ATAC) and Polyalthia cerasoides (PCAC) activated carbons show good sorption capacities of values: 97.0, 76.8 and 66.7 mg/g, respectively in a wide pH ranges. Unlike that of other two activated carbons, Cordia dichotoma activated carbon is effective even in acid conditions, indicting its direct applicability to Cu-based industrial effluents which are generally acidic in nature. Interference of two fold excess of co-ions is minimal. The established extraction conditions for the removal of more than 95.0% from 10 ppm Cu2+ solution at room temperature (303 K) using CDAC as sorbent are: pH: 3-9; time of equilibration: 1 h; sorbent dosage: 0.100 g/100 mL; with ATAC: pH: 6-9; time of equilibration: 1.5 h and sorbent dosage: 0.125 g/100 mL; and with PCAC: pH: 6-9; time of equilibration: 2.0 h and sorbent dosage 0.50 g/100 mL. Spent adsorbents can be regenerated and reused until four cycles with minimal loss of adoption capacities. Thermodynamic studies revealed that the sorption is spontaneous and endothermic in nature. Further, the ΔH value for CDAC is 30.156 KJ/mol; it indicates the strong chemisorption and may be through reduction to Cu+/Cu and/or complex formation between Cu2+ and functional groups of the adsorbent. The ΔH values of other two activated carbons, ATAC and PCAC, indicated that the sorption is mainly physical with strong inclination towards chemical nature. Positive ΔS values of all the three sorbents, emphasizes the disorder or randomness at the solid-liquid interface and hence favourable conditions for more penetration of Cu2+ into the surface layers of the adsorbent and hence, more removal of Cu2+ ions. The negative ΔG values indicate that the sorption forces are good enough to cross the potential barrier at the solid-liquid interface and hence the process is spontaneous. The prepared three activated carbons were also successfully applied to industrial effluent and polluted lake samples.

Removal of Lead(II) Ions from Industrial Waste Water using Biomaterials of Terminalia ivorensis Plant and its Composite with Fe-Alginate Beads as Adsorbents

Three effective adsorbents are developed for the removal of lead ions from industrial effluents based on stem powder of Terminalia ivorensis (TISP), its active carbon (TIAC) and a composite of Fe-alginatebeads doped with the active carbon (TIAC-beads). The beads are synthesized by crosslinking the Na-alginate with Fe3+ instead of conventional Ca2+, with an aim to improve its adsorptivity. The conditions for obtaining the uniform beads with good morphology are established. These sorbents are investigated for their adsoptivity for Pb2+ ions with respect to various extractions conditions and are optimized for the maximum removal of Pb2+. The sorption capacities are found to be: 34.0 mg/g for TISP, 39.0 mg/g for TIAC and 49.0 mg/g for TIAC-beads. The higher sorption of TIAC-beads may be due to the cumulative sorption nature of active carbon assisted by iron-alginate beads towards Pb2+. The optimum conditions are: for TISP: pH: 5, sorbent dosage: 2.0g/and, eqi. time: 120 min; for TIAC: pH: 7, sorbent dosage: 1.5 g/L; eqi. time: 90 min; and for TIAC-beads: pH: 6, sorbent dosage: 1.0 g/L and eqi. time: 60 min. Substantial removal of Pb2+ is noted in a range of pHs: 4 to 9 for TIAC-beads; 4 to 8 for TISP and 6 to 8 for TIAC. This permits the applicability of the sorbents in neutral as well as less acidic and basic solutions and it is a good feature as Pb2+ containing industrial effluents are inconsistent in their pHs. Three fold excess of co-ions marginally interfered. Thermodynamic studies reveal that the adsorption is endothermic and spontaneous. The high ΔH values, > 30.0 KJ/mol, emphasizes the chemical nature of binding between Pb2+ and surface functional groups of sorbent and is increasing in the order: TISP (32.385 KJ/mol) < TIAC (35.531 KJ/mol) < TIAC-beads (42.480 KJ/mol). This is supported by symmetrical humps with in the curves of pH vs. % removal. Positive ΔS values reflect disorder at the solid-liquid interface-an ideal condition for Pb2+ ions to cross the surface barrier existing at the solid/liquid interface, resulting in good adsorptivity. Negative ΔG values indicate the spontaneity of the sorption process. Spent TISP/TIAC/TIAC-beads can be regenerated and reused for 2 cycles for TISP, 3 cycles for TIAC and 3 cycles for TIAC-beads. The sorbents are successfully applied to remove Pb2+ form industrial effluents.

Exploring the drug-lipid interaction of weak-hydrophobic drug loaded solid lipid nanoparticles by isothermal titration calorimetry

Drug-lipid interaction was a vital issue for weak-hydrophobic drug-loaded solid lipid nanoparticles (WHD-SLNs). With a weak drug-lipid interaction, the drug loading capacity and physical stability could be low, and thus the drug-lipid interaction should be investigated. This paper was aimed to explore the drug-lipid interactions of WHD-SLNs by isothermal titration calorimetry (ITC). Benzoic acid (BEA) and salicylic acid (SAA) were chosen as the model weak-hydrophobic drugs, and stearic acid (SA) was selected as the model lipid material. For reference, the melting point depression (the proof of molecular interaction) of BEA-SA system and SAA-SA system was explored by differential scanning calorimetry (DSC) and hot stage polarized-light microscopy (HSPM). The ITC results demonstrated that BEA-SA interaction had negative ΔH and negative ΔS, while SAA-SA interaction possessed slightly negative ΔH and positive ΔS. It was indicated that the major interactions in BEA-SA interaction and SAA-SA interaction were hydrogen bonds and hydrophobic forces, respectively. Shown by DSC and HSPM results, the melting point depression in BEA-SA system was more significant than SAA-SA system. Therefore, melting point depression was mainly associated with hydrogen bond interactions, rather than hydrophobic forces. This study could provide new insight for the interpretation of drug-lipid interaction of WHD-SLNs.

Studies on conformational changes induced by binding of pendimethalin with human serum albumin.

Pendimethalin (PND) is a widely used herbicide in modern means of agricultural practices. So, its toxic residues exist extensively in the environment and can enter human body. Therefore, the invitro interaction of PND with human serum albumin (HSA) has been explored by employing various biophysical, molecular docking and dynamics simulation studies as well as enzyme kinetics to unravel its binding mechanism. The binding constant of the PND-HSA complex was about 104 M-1 using Fluorescence quenching spectra. The negative value of Gibbs free energy change (ΔG0 = -32.0 kJ mol-1) indicates this interaction is a spontaneous process. A large negative ΔH0 and positive ΔS0 suggests that hydrophobic interactions and H-bonding are involved in the binding process of PND with HSA. The binding of PND can cause conformational and micro-environmental changes in HSA molecule, as shown by various biophysical and molecular dynamics simulation studies. The site marker competition and molecular docking and simulation experiments affirmed that the binding of PND to HSA occurs at or near site I. Esterase-like activity of HSA exhibited decline in the presence of PND revealed the direct involvement of Lys199 of subdomain IIA (Sudlow's site I) in the binding process.

Optimizing textile dye removal by activated carbon prepared from olive stones

Activated carbon prepared from black and green olive stones were successfully used as an adsorbing agent to remove methylene blue from water. Scanning electron microscopy showed how the deep abundant cavities were occupied after adsorption. Fourier-transform infrared spectroscopy showed various functional groups on both adsorbents before and after adsorption. It was also noted that the highest N%, H% and C% prior to adsorption was found in black activated carbon olive stones. Furthermore, results showed that the maximum adsorption of methylene blue was at the optimum pH value of 10. The maximum adsorption capacity of methylene blue was 714 and 769 mg/g for black and green activated carbon olive stones, respectively. Methylene blue removal efficiency reached its maximum capacity at approximately 79%. The equilibrium data were best fitted by Freundlich isotherm reaching R2 value of 98%. In addition, thermodynamic studies resulted in negative ΔG∘ value indicating that the adsorption process was spontaneous and feasible, negative ΔH∘ value confirming the exothermic reaction of the adsorption process, and positive ΔS∘ value for green activated carbon olive stones was higher than that for black activated carbon olive stones indicating the good affinity of methylene blue towards the adsorbent.

"Sweeping" Ortho Substituents Drive Desolvation and Overwhelm Electronic Effects in Nd3+ Chelation: A Case of Three Aryldithiophosphinates.

Bis[o-(trifluoromethyl)phenyl]dithiophosphinate is a sulfur-donating ligand capable of providing the largest reported trivalent lanthanide (Ln3+)-actinide (An3+) group separation factors. Literature has shown that the placement and number of the -CF3 functionalities on the aryl rings proximate to the ligating sulfur atoms can significantly impact Ln3+-An3+ extraction and separation factors, but the complexation thermodynamics of -CF3-derivatized aryldithiophosphinates have not been considered to date. This systematic study considers the complexation of three CF3-substituted aryldithiophosphinates-bis(phenyl)dithiophosphinate (LI), [o-(trifluoromethyl)phenyl](phenyl)dithiophosphinate (LII), and bis[o-(trifluoromethyl)phenyl]dithiophosphinate (LIII), with Nd3+ in an ethanolic environment. The chelating ability of NdIII by these ligands follows the order of LIII > LII > LI, which is in line with the reported extraction efficiency. The positive ΔS, as well as positive ΔH, suggests that Nd3+ chelation is entropy-driven and effective desolvation is critical to enabling Nd3+ interaction with otherwise weakly interacting sulfur-containing ligands. Extended X-ray absorption fine structure results confirm thermodynamic investigations and suggest that LI can only form up to 1:2 (M-L) complexes, while LII and LIII form up to 1:3 complexes with Nd3+. All three LIII anions have bidentate interactions with NdIII, but two LII anions have bidentate interactions with Nd3+, while the third LII anion is monodentate. The significant increase in ΔS with each o-CF3 addition suggests aiding desolvation could be central in enabling f-element interaction with weakly interacting donor groups, and this report provides an approach to controlling f-element desolvation as an innovative f-element chelating strategy.

Potential of isoquercitrin as antisickling agent: a multi-spectroscopic, thermophoresis and molecular modeling approach

Sickle cell disease is an inherited disease caused by point mutation in hemoglobin (β-globin gene). Under oxygen saturation, sickle hemoglobin form polymers, leading to rigid erythrocytes. The transition of the blood vessels is altered and initiated by the adhesion of erythrocytes, neutrophils and endothelial cells. Sickle Hemoglobin (HbS) polymerization is a major cause in red blood cells (RBC), promoting sickling and destruction of RBCs. Isoquercitrin, a medicinal bioactive compound found in various medicinal plants, has multiple health benefits. The present study examines the potential of isoquercitrin as an anti-sickle agent, showing a significant decrease in the rate of polymerization as well as sickling of RBCs. Isoquercitrin-induced graded alteration in absorbance and fluorescence of HbS, confirmed their interaction. A negative value of ΔG° strongly suggests that it is a spontaneous exothermic reaction induced by entropy. Negative ΔH° and positive ΔS° predicted that hydrogen and hydrophobic binding forces interfered with a hydrophobic microenvironment of β6Val leading to polymerization inhibition of HbS. HbS-Isoquercitrin complex exhibits helical structural changes leading to destabilization of the HbS polymer as confirmed by CD spectroscopy. MST and DSC results indicate greater changes in thermophoretic mobility and thermal stability of sickle hemoglobin in the presence of isoquercitrin, respectively. These findings were also supported by molecular simulation studies using DOCK6 and GROMACS. Hence, we can conclude that isoquercitrin interacts with HbS through hydrogen bonding, which leads to polymerization inhibition. Consequently, isoquercitrin could potentially be used as a medication for the treatment of sickle cell disease.Communicated by Ramaswamy H. Sarma

DNA-binding studies of a new Cu(II) complex containing reverse transcriptase inhibitor and anti-HIV drug zalcitabine

In this study, a new copper(II) complex with zalcitabine (ddC) drug was synthesized and characterized by Fourier-transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–vis), mass spectroscopy, thermal gravimetric analysis and density functional theory. Then, its effect on calf-thymus DNA (CT-DNA) was investigated using absorption and fluorescence spectroscopy and viscometry technique. On the basis of FT-IR and computational studies, zalcitabine chelates with copper using its C(2)=O and N(3) group in the [Cu(zalcitabine)Cl2] ([CuCl2(ddC)]) complex. On the basis of the electrospray ionization mass spectroscopy of the Cu–ddC complex, monomeric copper complex [C9H13N3O3CuCl2] was formed. The results of fluorescence studies indicated increasing to around 2.5 times in emission intensity of fluorescence signal of the complex. The enhancement of emission intensity and also the positive ΔH and positive ΔS values suggested that the hydrophobic interaction plays a major role in the binding with overall binding constant of 1(±0.25)×105 M−1. The ΔG value implied that the interaction occurred between DNA and the complex formation was spontaneous. Finally, changes in the relative viscosity showed that groove binding must be the predominant form of binding. Evidences are provided that [Cu(ddC)Cl2] could interact with DNA via minor groove interaction mode.

Synthesis of MoO3/polypyrrole nanocomposite and its adsorptive properties toward cadmium(II) and nile blue from aqueous solution: Equilibrium isotherm and kinetics modeling

AbstractMolybdenum trioxide/polypyrrole (MoO3/Ppy) nanocomposite was prepared via oxidative polymerization of pyrrole monomer with MoO3 nanoparticles. The adsorption of Cd+2 and nile blue (NB) onto the nanocomposite was investigated in terms of various process parameters. The characterization of MoO3/Ppy nanocomposite was carried out by Fourier transform‐infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy dispersive X‐ray spectroscopy. Higher R2 (0.992–0.997 for Cd+2 and 0.997–0.998 for NB) and lower standard error of estimation values (1.04–1.82 for Cd+2 and 0.87–1.07 for NB) for Freundlich isotherm highlighted the multilayer adsorption onto heterogeneous nanocomposite surface. The higher Qm values at 323 K for Cd+2 (181 mg/g) and NB (189 mg/g) compared to many reported adsorbents proved the adsorptive superiority of MoO3/Ppy. The energy of adsorption (E) values from Dubinin–Radushkevich model was 1.26–1.38 and 1.36–1.44 kJ/mol for Cd+2 and NB, respectively, suggesting physical adsorption. Pseudo‐second order kinetic model governed the adsorption of Cd+2 and NB with intraparticle and liquid film diffusion controlling the mechanism. The negative ΔG values (8.4–9.4 kJ/mol) and positive ΔH values (2.5–6.1 kJ/mol) implied spontaneous and endothermic adsorption process. The positive ΔS values (0.036–0.048 kJ/mol/K) indicated increased randomness at MoO3/Ppy‐Cd+2 or NB interface. The MoO3/Ppy nanocomposite proved to be suitable and efficient adsorbent for sequestering of Cd+2 and NB from aqueous solution.

Biosynthesis and Characterization of Iron Nanoparticles for Effective Adsorption of Cr(VI)

In this study, iron nanoparticles (FeNPs) were synthesized via a green method using loquat (Eriobotrya japonica) leaves aqueous extract as a renewable reducing agent. The synthesized FeNPs were characterized by DLS, XRD, FT-IR, SEM/EDX, and TEM analysis, and then, they were used as an adsorbent for Cr(VI) removal from aqueous solutions. Batch adsorption experiments were carried out to investigate the optimum adsorption parameters such as the initial pH of the solution, temperature, initial Cr(VI) concentration, and adsorbent concentration. The optimum adsorption conditions were determined as initial pH 3.0, temperature 45°C, and adsorbent concentration 1 g/L. Also, a linear increase was observed in adsorbed Cr(VI) amounts with the increasing initial Cr(VI) concentrations. The biosynthesized FeNPs showed the high removal levels higher than 90% for Cr(VI) adsorption at a wide range of initial Cr(VI) concentrations (50–500 mg/L). The experimental equilibrium data were modelled with Langmuir and Freundlich isotherm models, and it was found that experimental equilibrium data could be well described by the Langmuir isotherm model. The maximum monolayer coverage capacity of FeNPs for Cr(VI) adsorption was found to be 312.5 mg/g. The pseudo-first-order and the pseudo-second-order kinetic models were applied to the experimental adsorption data, and it was concluded that the data were defined as the best agreement with the pseudo-second-order kinetic model. Weber–Morris model was used to investigate the effect of mass transfer on the adsorption of Cr(VI) onto FeNPs; it was observed that both the film (boundary layer) and intraparticle diffusion affected the studied adsorption process. The thermodynamic studies suggested that Cr(VI) adsorption onto FeNPs was endothermic and nonspontaneous, and the positive ΔS value indicated increased disorder at the solid-solution interface during the adsorption.

Sorption studies of toxic cations on ginger root adsorbent

This research reports the feasibility of using pristine ginger root (PGR), base treated ginger root (BTGR) and acid treated ginger root (ATGR) adsorbents to simultaneously remove Cu(II), Pb(II) and Ni(II) ions from aqueous solution under different experimental parameters by batch method. Different system parameters such as the effect of metal concentration, time dependent studies and temperature effect were evaluated. The sorption trend indicated that the pretreated adsorbents; ATGR and BTGR had better performance than PGR. The sorption of Cu(II), Ni(II) and Pb(II) ions onto BTGR is 16.3, 18.9 and 17.6 mg/g onto ATGR is 15.3, 18.6 and 17.5 mg/g and onto PGR is 1.8, 1.9 and 1.9 mg/g respectively. The overall Cu/Ni/Pb ions sorption trend for the adsorbents is BTGR > ATGR > PGR. Freundlich isotherm best describes all the sorption processes in this work. The sorption rate results of Ni(II) ions was much faster than those of Pb(II) and Cu(II) in all the adsorbents. The good unity fits of PSO data suggests that Cu(II), Ni(II) and Pb(II) is better described by this model and the sorption mechanism is based on electrostatic interactions and adsorption sites. The ΔG° data gave negative values for all samples; suggesting that the sorption processes were spontaneous. The positive ΔS° figures indicated that the degree of freedom for Cu(II), Ni(II) and Pb(II) ions was not restricted on PGR, ATGR and BTGR adsorbents.

Water-insoluble cyclodextrin polymer crosslinked with citric acid for paraquat removal from water

The anionic water-insoluble cyclodextrin polymer (polyCTR-β-CD) was crosslinked between β-cyclodextrin (β-CD) and citric acid (CTR) at 180 °C during 30 minutes to eliminate paraquat (PQ) from water. The reaction yield was equal to 70.2%, the ionic exchange capacity corresponded to 3.29 mmol·g−1 and the β-CD content was 0.29 mmol·g−1. Then, samples were characterized by SEM, ATR-FTIR, TGA, BET and stereoscopic microscope. Adsorption experiments were investigated with different factors such as pH of the solution, contact time, initial concentration of paraquat and adsorption temperature. The relevant pH was equal to 6.5 and the optimal contact time was 120 minutes to attain adsorption equilibrium. At 30 °C, the adsorption capacity was increased (9.4, 17.4 and 20.8 mg·g−1) when the initial concentration of paraquat was raised (25, 50 and 200 mg·L−1 respectively). Adsorption kinetics was appropriated to the pseudo-second-order model and adsorption isotherm was fitted to the Langmuir model. For thermochemistry parameters at different temperatures, the negative ΔG° showed a spontaneous adsorption process, the negative ΔH° indicated an exothermic process and the positive ΔS° exhibited an increase disorder. Finally, the reusability of the insoluble polymer was reached 78.3% after four regeneration cycles in methanol.