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• Crystal structure studies of inclusion complexes of α-cyclodextrin with p -aminobenzoic acid and nicotinic acid. • Inclusion complexes confirmed by DSC calorimetry, FT-IR, 1H NMR spectroscopy. • ITC calorimetry appointed stoichiometry (n) and standard thermodynamic functions (ΔH, ΔG, ΔS), binding constants (K). In this work, inclusion complexes of α-cyclodextrin with p -aminobenzoic acid (PABA) and nicotinic acid (NIK) were studied. Solid-state complexes were obtained and studied with single-crystal X-ray diffraction, powder X-ray diffraction, differential scanning calorimetry, and FT-IR spectroscopy. Additionally, the formation of complexes was studied in aqueous solutions with isothermal titration calorimetry and 1H NMR spectroscopy in DMSO‑d6 solutions. Single crystal studies, FT-IR spectroscopy and powder diffraction confirmed the inclusion of PABA and NIK inside the cyclodextrin cavity. From the results of the isothermal titration calorimetry, the stoichiometry (n) and standard thermodynamic functions (ΔH, ΔG, ΔS) of complexation, as well as binding constants (K) for the formed complexes were calculated. The obtained results confirmed the thermodynamically spontaneous formation of complexes in exothermic reactions. Furthermore, the results obtained were compared for complexes of PABA/NIK acids with β-cyclodextrin. A database survey of α-cyclodextrin complexes with different benzoic acids available in the CSD database was performed. [Display omitted] [ABSTRACT FROM AUTHOR]

An experimental investigation of azo dye removal using activated Prosopis juliflora root was carried out using the batch adsorption technique. The P. juliflora roots were collected and synthesized using a chemical synthesis technique, and their pore size and surface area was analyzed using N2 - adsorption and desorption process. The scanning electron microscopy/energy-dispersive X-ray spectroscopy analysis confirms the presence of targeted azo dyes on the surface of the prepared adsorbent material and the thermal stability of the adsorbent was analyzed using thermogravimetric analysis and derivative thermogravimetry. The X-ray diffraction analysis shows the amorphous structure and the intensity of activated charcoal P. juliflora adsorbent. Batch adsorption studies were conducted to determine the optimal adsorption parameters such as pH, dosage level, concentrations, contact time, and temperature. Adsorption kinetic studies confirm the favorable adsorption process between the adsorbate and the adsorbent, and isotherm studies fitted well with the high regression values. Thermodynamic studies revealed the adsorption between the adsorbent and adsorbate to be endothermic, and the desorption studies confirmed the high recovery of spent adsorbent using concentrated sulphuric acid. As a result, the activated P. juliflora powder adsorbs 99.6% of Reactive Orange - RO-16, 94.43% of Reactive Red - RR-120, and 82.26% of Reactive Blue - RB-19 azo dyes from the prepared synthetic solutions in batch mode of adsorption process. [ABSTRACT FROM AUTHOR]

Investigations were carried out for the removal of Crystal violet (CV) dye from an aqueous solution using sewage sludge as adsorbent prepared after heating at 900°C. X-ray fluorescence spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction analysis were used for the characterization of sludge. The results of batch studies showed the values of optimum parameters such as contact time (180 min), adsorbent dose 10 g/L and temperature (30°C). The removal efficiency was found to be about 98.4% and the equilibrium adsorption capacity of Crystal violet dye was 9.508 mg/g. The Freundlich, Langmuir, Redlich–Peterson, and Dubinin–Radushkevich isotherms were employed to evaluate the equilibrium data from batch adsorption studies. Kinetic data were analyzed using kinetic models such as; pseudo-first-order, pseudo-second-order, intraparticle diffusion. Nonlinear regression method and error functions namely; R², sum of error squares, G², HYBRID, Marquardt’s percent standard deviation, root mean square error and mean square error were used to determine the best fitted model. Freundlich isotherm model best fitted the data showing multilayer adsorption of CV dye on activated sludge while kinetic studies of CV dye were well described by pseudo-second-order model. Thermodynamic characteristics for dye adsorbent system indicated that the adsorption process was spontaneous and endothermic in nature. Results show that activated sludge can be effectively used as low-cost adsorbent for the removal of cationic dyes from aqueous solution. [ABSTRACT FROM AUTHOR]

Chitosan was impregnated into porous activated coal to produce a multifunctional chitosan/activated coal (Cs/Ac) composite. The resulted Cs/Ac was characterized and utilized as a cost–effective adsorbent for Mn(VII) at altered temperatures (i.e., 25, 35, and 45 °C). The adsorption results were fitted to classical as well as advanced statistical physics models. The Freundlich equation described well the achieved experimental data at all temperatures. Enhancing the Langmuir adsorption capacity from 203.26 to 224.03 mg/g with temperature indicated that Mn(VII) adsorption was an endothermic process. Steric, energetic and thermodynamics data of the double layer model with two energy sites (i.e., the best fit statistical model) were completely interpreted. The number of Mn(VII) per adsorption site (n) was between 0.76 and 0.92 suggested the presence of multi–docking and multi–interactions mechanisms. The active sites density (N M) of the Cs/Ac decreased with improving temperature. Energetically, Mn(VII) uptake by Cs/Ac was governed by physical interactions (i.e., adsorption energy <40 kJ/mol). Macroscopically, the interaction between Mn(VII) and Cs/Ac was spontaneous. Overall, modification of the Ac by the used marine biomass (Cs) produced a promising Mn(VII) adsorbent and also, the application of physical analysis offered a deep interpretation for the adsorption mechanism. [ABSTRACT FROM AUTHOR]

Removal of toxic heavy metal ion concentration (Cr, Pb, and Zn) from the aqueous solution has been investigated using sugarcane bagasse as an adsorbent. The various properties of sugarcane bagasse powder were analyzed and the Fourier transmission infrared spectra, scanning electron microscopy, and energy dispersive X-ray analysis of sugarcane bagasse powder, before and after adsorption of Cr(VI), Pb(II), and Zn(II) were also examined. Test results show that the maximum adsorption efficiency of 95.65% for Cr(VI), 87.26% for Pb(II), and 83.32% for Zn(II) were attained at the pH of 6.0, the temperature of 30°C, the contact time of 60 min, the adsorbent dosage of 2.5 g/L with 25 mg/L of metal ion concentrations. The Langmuir and Freundlich isotherm models were adopted for the batch adsorption experimental work and the results prove that the pseudo-second-order model was fitted well with kinetic data. Also, the thermodynamic study confirms that adsorption mechanism is endothermic in nature with the best possible correlations. [ABSTRACT FROM AUTHOR]

• Codium vermilara is a good biosorbent of Cu2+ ions. • RSM was successfully employed to optimize the process variables. • Removal efficiency of Cu2+ was more than 85%. • Data fitted well D–R isotherm, PFO, Elvoish and Intraparticle diffusion models. • The biosorption was non-spontaneous, randomness and endothermic. In this investigation, the efficiency of Codium vermilara for copper ions removal from aqueous solution was studied. Central Composite Design has been used for the Response Surface Methodology and has been found to be an effective method for investigating the influences of various variables and their interactions on the efficiency of Cu2+ ions removal. The interactive impacts of four variables: algal dose, pH, initial concentrations of copper and contact time on the copper removal efficiency were assessed. Algal dose 0.75 g/L, pH 5.28, contact time 70.51 min, and copper concentration 48.75 mg/L were found to be the conditions of optimum biosorption. The efficiency of copper removal was found to be 85.5% under these optimum conditions. Copper removal on the biomass of C. vermilara followed well the kinetics of pseudo-first-order, Elvoish and Intraparticle diffusion. Compared to the other models, Dubinin-Radushkevich isotherm best suited the experimental data revealing that the adsorption mechanism was physical adsorption. Thermodynamic parameters exhibited non-spontaneous, randomness and endothermic biosorption of Cu2+ ions. Additionally, the biosorbent characterization was estimated by scanning electron microscopy and Fourier transform infrared analysis. Thus, C. vermilara could be used as possible biosorbent for removing heavy metals and other pollutants from the environment. [ABSTRACT FROM AUTHOR]

Barium sulfide has been widely accepted as a useful barium compound in many fields. To reduce the emission of CO 2 through tail gas during the current industrial production of barium sulfide by the black ash method, a new clean process for barium sulfide preparation by barite reduction using elemental sulfur is proposed. Herein, we report a study on the kinetics and thermodynamics of the thermal decomposition of barium sulfate by elemental sulfur. The mechanism of this complicated gas–solid reaction was investigated under non-isothermal conditions, at different heating rates. Four isoconversional methods were used to determine the activation energy. The mechanism model of the barium sulfate decomposition was confirmed using the double equal–double step method. The results suggested that the barium sulfate decomposition followed the Jander D3 spherical symmetry model; the order of the reaction (n = 1.06) was determined using the Carne equation. Unlabelled Image • A co-production scheme for converting barium sulfate to barium sulfide, using elemental sulfur, is proposed. • The mechanism of thermal decomposition of barium sulfate by elemental sulfur was studied using thermodynamics simulation. • Non-isothermal decomposition of barium sulfate was studied at different heating rates. • Kinetics parameters were determined using isoconversional methods. [ABSTRACT FROM AUTHOR]

A novel superoleophilic-hydrophobic nonanyl chitosan-poly (butyl acrylate) grafted copolymer was fabricated as a low-cost oil-adsorbent. Chitosan (CS) was coupled with a hydrophobic nonanal (N) to form nonanyl chitosan (NCS) schiff base, and followed by grafting with butyl acrylate monomers (ButA). The grafted copolymer was characterized by FTIR, TGA and SEM tools. The grafting percent was augmented and reached 88.5% with increasing ButA concentration up to 156 mM. Moreover, measurements of contact angle proved the superoleophilic character of NCS-g-poly (ButA) copolymer with an oil-contact angle 31°. Factors affecting the removal process such as contact time, oil type, oil dose, adsorbent dose, temperature and agitation speed were optimized. An increment in the oil removal (%) was observed with increasing the oil viscosity in the order of gasoil < mobil-1 oil < light crude oil < heavy crude oil. Besides, the adsorption process followed the pseudo-second order model and the equilibrium data were sufficiently fitted with the Langmuir model with a maximum adsorption capacity 108.79 g/g at 25 °C. Thermodynamic parameters computed from Van't Hoff plot confirmed the process to be exothermic, favorable and spontaneous. The results nominate the superoleophilic adsorbent as a potential oil- adsorbent for petroleum oil spills removal. Unlabelled Image • An oleophilic nonanyl chitosan-poly (butyl acrylate) grafted copolymer was prepared. • An oil-artificial seawater system was conducted as an adsorption medium. • Factors affecting the crude oil-adsorption were studied • Results were verified by classical kinetic models, equilibrium isotherm models and thermodynamics studies. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • RSM-CCD technique provided the maximum swelling of 496.57% for the semi-IPN (adsorbent). • Maximum removal of eosin yellow and crystal violet was 95.42% and 97.58%, respectively. • Langmuir adsorption isotherm and second order kinetics were highly favorable to removal process of both dyes. • Intraparticle diffusion of dyes through three step process was applicable. • The eco-friendly adsorbent can be recycled up to many cycles before its disposal. Abstract Blending of xanthan and acacia gives a unique hybrid that was used for the synthesis of semi-interpenetrating network (semi-IPN) in which poly(acrylamide) chains were grafted onto hybrid of xanthan-acacia followed by their cross-linking (Xan-Aca-cl-poly(AAm)). Optimization was carried out under response surface methodology-central composite design (RSM-CCD). Maximum percentage swelling of semi-IPN obtained was 496.57%. The concentrations of acrylamide, citric acid and ammonium persulphate used as monomer, cross-linker and initiator, respectively were found to be significant parameters. The blend was highly effective in removal of both cationic (crystal violet) and anionic dyes (eosin yellow) showing maximum dye removal capacity of 97.58% and 95.42%, respectively under optimized parameters - 0.4 g semi-IPN dose in 15 ml dye solution of 10 mg L−1 concentration within 16 h. Adsorption mechanism of both the dyes followed three steps in accordance with intraparticle diffusion model along with mono layer langmuir adsorption criteria. Second order kinetics was followed in case of both dyes. Thermodynamic studies gave idea about the exothermic nature of adsorption. Semi-IPN could be recycled up to eight consecutive cycles and hence, can be utilized for industrial purpose for removal of dyes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chitosan, clay, carbonaceous materials, and biomass wastes for RR120 adsorption. • The maximum capacity varying from 1.45 to 482.2 mg/g. • The Langmuir isotherm and PS2 kinetic equations gave the best fit. • Electrostatic attraction, hydrogen bonding, and π-π interaction were the main mechanisms. The textile industry has a crucial role in our economy. This industry generates wastewater that contains dangerous dyes as well as pigments, suspended and dissolved solids, and heavy metals that are untreated or used directly for irrigation purposes, released into soil and water receptors, thus negatively affecting the environment. Several dyes have an impact on the human health and aquatic biota due to their toxic and even carcinogenic nature. One of the dyes widely utilized in the textile industry, Reactive Red 120 (RR120), poses a risk to the aquatic system because of its low biodegradability. There are many methods to decontaminate dye-containing wastewater such as physical, chemical, and biological processes. Adsorption is an attractive method owing to its simplicity, easy operation, and low cost. This review article explores the elimination of RR120 dye by different adsorbents. Special emphasis is given to the various adsorption parameters that affect the adsorption process, the adsorption mechanism, regeneration, and thermodynamic studies. The results demonstrated that the RR120 dye could be removed from wastewater by a wide range of different adsorbents, including chitosan, clay, carbonaceous materials, and biomass wastes, with a maximum capacity varying from 1.45 to 482.2 mg/g. The pseudo-second-order kinetic equations and Langmuir isotherm gave the best fit to the adsorption data. Future work will focus on analyzing the costs associated with the preparation and application of the various adsorbents to remove the RR120 dye and investigating their potential in column studies and also in more realistic conditions such as using real wastewater. [ABSTRACT FROM AUTHOR]

Abstract The presence of organic dyes in the aquatic environment is a serious global problem because of the serious negative consequences on the quality of ecosystems. Among various physico-chemical methods, the adsorption could be considered a promising alternative for removing dyes from aqueous media, due to its efficiency, high selectivity, low cost, ease of operation, simplicity, and availability in a wide range of experimental conditions. However, all these advantages are closely related to the nature of adsorbent material used in the adsorption processes of dyes. The adsorbent materials available in large quantities requiring a simple preparation will enhance the benefits of the adsorption processes, in agreement with the concepts of green chemistry. This review is focused on the use of leaf-based materials, in raw or modified forms, as adsorbents for the removal of dyes from aqueous effluents, with applications in the wastewater treatment. This review addresses characterization of leaf-based adsorbents, possible utilization of leaf-based adsorbents (raw and activated forms) for dye removal and possible applications in pilot and full scale systems. Also, thermodynamics, equilibrium and kinetic parameters of dye adsorption on leaf-based adsorbents are discussed. The practical utility of leaf-based adsorbents for dye removal, and their possible uses in the treatment of industrial wastewater are copiously highlighted. Graphical abstract Unlabelled Image Highlights • Leaf-based adsorbents (raw & modified) are reviewed for textile dyes removal. • Recent analytical techniques were examined used in the adsorption process. • Maximum adsorption capacities, best isotherm and kinetic modeling are presented. • Enthalpy-entropy compensation effect on the adsorption process was discussed. • Due to their efficiency leaf-based adsorbents could be used at industrial scale. [ABSTRACT FROM AUTHOR]

Abstract The significance of soil mineral properties and secondary environmental conditions such as pH, temperature, ionic strength and time in the partitioning of eight selected polychlorinated biphenyl (PCB) congeners between aqueous solution and soil particles with different grain sizes was studied. The mineral properties of a model soil sample were determined, and Brunauer–Emmett–Teller (BET) adsorption–desorption isotherms were employed to observe the surface characteristics of the individual modeled soil particles. Batch adsorption experiments were conducted to determine the sorption of PCBs onto soil particles of different sizes. The results revealed that the sorption of PCB congeners onto the soil was dependent on the amount of soil organic matter, surface area, and pore size distribution of the various individual soil particles. Low pH favored the sorption of PCBs, with maximum sorption occurring between pH 6.5 and 7.5 with an equilibration period of 8 hr. Changes in the ionic strength were found to be less significant. Low temperature favored the sorption of PCBs onto the soil compared to high temperatures. Thermodynamic studies showed that the partition coefficient (K d) decreased with increasing temperature, and negative and low values of Δ H ° indicated an exothermic physisorption process. The data generated is critical and will help in further understanding remediation and cleanup strategies for polluted water. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

The discharge of toxic ions including fluoride into the aquatic environment causes huge large-scale health problems, especially for developing African countries. Defluoridation of solutions by adsorption technique is commonly applied and exhibits helpful results. In this study, natural clay was individually modified by decyltrimethylammonium bromide and a combination of hydrogen peroxide with decyltrimethylammonium bromide. The natural and modified clays were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), zeta potential, Brunauer–Emmett–Teller specific surface area (S BET ), and tested as adsorbents for fluoride from solutions in the pH range of (2.0–10.0) at 25 °C. The new strategy of natural clay treatment by a solution of the used combination gave the highest removal efficiency of fluoride as compared to the other adsorbents at pH 2.0. Fluoride adsorption studies were evaluated under different experimental parameters such as contact time, initial concentration, adsorbent dose, co-existing anions, and temperature. Removal of fluoride was found to be rapid and equilibrium was attained after 60 min of contact time. In the presence of phosphate, sulphate and chloride as competitive anions, fluoride uptake was slightly decreased. Linear and non-linear forms of Langmuir, Freundlich and Dubinin–Radushkevich models were used in fitting fluoride adsorption data. Langmuir model with a maximum adsorption capacity (53.66 mg/g) described well the experimental data at 25 °C. The pseudo-second-order model with a correlation coefficient ( R 2 = 0.999 ) fitted well the kinetic data indicating that chemisorption process could be a rate detrmining–step. Based on thermodynamic parameters, fluoride uptake process was spontaneous and endothermic in nature. This study suggested a new process for fabrication of a new clays based-adsorbent that could be efficiently used as a clean and cost–effective product for the purification of fluoride–bearing solutions. [ABSTRACT FROM AUTHOR]

Raw clay (RC) rich in organic matter (OM) was separately treated by hydrogen peroxide (H 2 O 2 ), cetyltrimethylammonium bromide (CTAB) and a solution of CTAB/H 2 O 2 . The new strategy of RC modification using CTAB/H 2 O 2 –solution presented a swollen product (CTAB/H 2 O 2 –clay) with porous structure. Raw and modified clays were characterized by XRD, SEM, FTIR, zeta potential, S BET surface area and tested as adsorbents for hexavalent chromium Cr(VI) and methyl orange (MO) from solutions. Adsorption experiments were conducted under experimental parameters including pH, shaking time, initial concentrations, adsorbent mass, temperature and ionic strength. CTAB/H 2 O 2 −clay gave the highest adsorption capacities for Cr(VI) and MO as compared to the other products at pH 2.0 and 3.0, respectively. Adsorption equilibrium of Cr(VI) and MO was evaluated using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich models. Langmuir model fitted well the uptake results and the maximum uptake capacities ( q max ) at room temperature (25 °C) were found to be 67.05 and 194.28 mg/g for Cr(VI) and MO, respectively. The values of mean free energy ( E ) were > 8.0 kJ/mol revealed the chemical nature of Cr(VI) and MO uptake. The pseudo-second-order model with R 2 = 0.9999 described well the kinetics data. Thermodynamic parameters ( ∆H 0 , ∆G 0 and ∆S 0 ) indicated that the uptake of Cr(VI) and MO was spontaneous and endothermic. [ABSTRACT FROM AUTHOR]

The present study evaluates the capability of ion exclusion chromatography (IEC) of short chain aliphatic carboxylic acids using a cation exchange column (8% sulfonated cross-linked styrene-divinylbenzene copolymer) in different experimental conditions. Since one of the prerequisites to the development of an efficient carboxylic acid separation process is to obtain the optimum operational conditions, response surface methodology (RSM) was used to develop an approach to evaluate carboxylic acids separation process in IEC columns. The effect of the operating conditions such as column temperature, sulfuric acid concentration as the mobile phase, and the flow rate was studied using Central Composite Face (CCF) design. The optimum operating conditions for the separate injection of lactic acid and acetic acid is temperature of 75 °C, sulfuric acid concentration of 0.003 N for both acids and flow rate of 0.916 (0.886) mL/min for acetic acid (lactic acid). Likewise, the optimum conditions for the simultaneous injection of acetic and lactic acid mixture are the column temperature of 68 °C, sulfuric acid concentration of 0.0003 N, and flow rate of 0.777 mL/min. In the next step, the adsorption equilibria of acetic acid and lactic acid on the stationary phase were investigated through a series of Frontal Analysis (FA), Frontal Analysis by Characteristic Points (FACP), and using Langmuir isotherm model. The results showed an excellent agreement between the model and experimental data. Finally, the results of thermodynamic studies proved that the IEC process for separation of acetic and lactic acid is a spontaneous, feasible, exothermic, and random process with a physical adsorption mechanism. The results of the current paper can be a valuable information in the stages of designing IEC columns for separation of aliphatic carboxylic acids. [ABSTRACT FROM AUTHOR]

Gallic acid is a natural polyphenol with important biological implications. Nevertheless, gallic acid present in agro-industrial wastewaters is considered like a micropollutant, due to its toxicity above certain levels. Therefore, recovery of gallic acid from these effluents is interesting both from industrial and environmental points of view. Industrially, it is attractive the recovery of polyphenols and the obtainment of added value products. On the other hand, from the environmental point of view it is always welcome the decrease of the contaminant charge of an effluent, which could be, for instance, further reused for irrigation. In this work, the adsorption of gallic acid on a novel anionic resin has been investigated. In first place, thermodynamic studies have been carried out. The adjustment of experimental data to Langmuir, Freundlich and Temkin isotherms has been checked. Results evidence that the Langmuir model offers the best fitting (coefficient of determination, R2 = 0.9961). Secondly, in an attempt of understanding the kinetic behaviour of the system, the fitting of experimental data to three different kinetic models has been carried out. Namely, pseudo-first order, pseudo-second order and Weber-Morris intraparticle diffusion models have been considered. The highest coefficients of determination (R2) are obtained when a pseudo-second order model is assumed (R2 in the range 0.9840-0.9997). Lately, the evaluation of Gibbs free energy revealed that gallic acid uptake is a spontaneous process for the considered Dowex 21K XLT resin (ΔGJ = -11.30 kj mol-1). Desorption studies have been also conducted and it has been found that after 120 min recovery efficiencies of gallic acid close to 100% are obtained. It has been proven that the resin performance is not altered at least for ten complete adsorption/desorption cycles. [ABSTRACT FROM AUTHOR]

n-Butane dehydrogenation to 1-butene and 2-butene intermediates on Bi-Ni (III) surface. [Display omitted] • n-Butane dehydrogenation pathway was investigated using thermodynamic and DFT studies. • Modification of NiO catalysts with BiO x enhanced the selectivity to 1,3-butadiene. • Thermodynamic studies revealed that reasonable yield of 1,3-butadiene is possible at higher temperatures. • n-Butane adsorption strength decreases with the addition of Bi promoters to Ni (III) surfaces. • 1,3-butadiene is favored via 1-butene pathway compared to 2-butene pathway due to lower activation barrier of the former. Dehydrogenation of n-butane is one of the main on-purpose method for producing 1,3- butadiene. Thermodynamics studies revealed that reasonable yields of 1,3-butadiene can only be achieved at higher temperatures, while the formation of butene isomers are favored at lower temperatures, confirming that 1,3-butadiene is a secondary product. In the present study, NiO/Al 2 O 3 and Ni-BiO x /Al 2 O 3 catalysts, having 10 and 20 wt% Ni and 10 and 30 wt% Bi loading were synthesized. Experimental testing using fixed bed reactor validated that the addition of BiO x improved 1,3-butadiene selectivity from 20 % to 43 % with similar n-butane conversion, at 500 °C. Also, density functional theory (DFT) studies for n-butane adsorption on Ni (1 1 1) and Bi-Ni (1 1 1) surfaces confirmed that, the addition of Bi promoters to the Ni surface modifies the n-butane adsorption strength resulting in lower adsorption energies of −0.02 eV weaker than −0.36 eV on Ni (1 1 1) surfaces. The reaction pathways investigation for the successive dehydrogenation route of n-butane on the most stable structures of Ni (1 1 1) and Bi-Ni (1 1 1) surfaces revealed that 1-butene pathway via the formation of 1-butyl, is most favorable relative to the 2-butene pathway via 2-butyl formation. This is due to the higher activation barrier for the formation of 2-butene intermediate on both Ni (1 1 1) and Bi-Ni (1 1 1) surfaces. [ABSTRACT FROM AUTHOR]

In this review classical studies on insoluble liquid monolayers formed by proteins are examined and compared. It has been focused the attention on the information that it is possible to obtain from the π-a isotherms recorded by compression of the monolayers. In recent decades new techniques have developed, mainly microscopy, that provide valuable information on the behavior and structure of fluid films. However, frequently the data are difficult to interpret and require a previous thermodynamic study of them on the basis of the surface tension (or surface pressure) as a function of the molecular area measurement. The main aim of this paper is to underline that surface balance type of Langmuir is a powerful technique since it enables to obtain information at molecular level from a macroscopic analysis. Notably, this information is revealed very interesting when it comes to studying protein films. From this point of view it has been reviewed the study methods and results for four proteins. [ABSTRACT FROM AUTHOR]

The present work aims to purify and perform a preliminary analysis on a thermostable serine alkaline protease from a recently identified P. minor. The enzyme was purified 2.7-fold with a 12.4 % recovery using Sephadex G-100 chromatography, DEAE-cellulose, and ammonium sulphate precipitation. The isolated enzyme has a specific activity of 473 U/mg. The purified protease had a molecular mass of 29 kDa, and just one band was seen, which matched the band obtained using SDS-PAGE. High thermostability was demonstrated by the enzymes, which had half-lives of 31.79 and 6.0 min (a 5.3-fold improvement), enthalpies of denaturation (ΔH°) of 119.53 and 119.35 KJ mol−1, entropies of denaturation (ΔS°) of 32.96 and 41.11 J/mol·K, and free energies of denaturation (ΔG°) of 108.87 and 105.58 KJ mol−1 for the protease enzyme. Studies on the folding and stability of alkaline proteases are important since their use in biotechnology requires that they operate in settings of extreme pH and temperature. According to the kinetic and thermodynamic properties, the protease produced by P. minor is superior to that produced by other sources and previously described plants, and it might find utility in a variety of industrial fields. Isolation, purification and thermodynamic characterizations of an Alkaline protease from Phalaris minor seeds. [Display omitted] • Biocatalytic potential of the alkaline protease isolated from P. minor. • Probing protein unfolding of the enzyme at high temperature and in strong denaturants. • Thermodynamic parameters indicated stability of alkaline protease in high temperature. • Urea mediated transitions of protein unfolding, of alkaline protease purified from P. minor Seeds. • Oxidants, cations, anions, metal ions, osmolytes, and surfactant stable protease. [ABSTRACT FROM AUTHOR]

Chiral 1,4-disubstituted-1,2,3-triazole mono- and biheterocyclic ‘click’ ligands derived from Cinchona alkaloids were synthesized using copper(I) catalyzed azide–alkyne cycloaddition (CuAAC) and studied in terms of coordination chemistry towards Cu(II). In broad range of pH the studied ligands form complexes with stoichiometry ML 2 in which the coordination involves two neighboring nitrogen atoms from 1,2,3-triazole (N3) and pyridine unit, respectively. The copper(II) coordination is site-selective among studied ligands ( L 1,2,4 ) apart for L 3 , which due to the lack of pyridine next to the triazole moiety and/or possible steric strain in formed complex turned out to be the ligand which metal binding is weaker than others under studied conditions. Thermodynamic analysis which involved potentiometric and calorimetric studies revealed relatively low stability of formed complexes, which binding events are entropy driven processes. [ABSTRACT FROM AUTHOR]

Humic acid was applied to the adsorption of U(VI) from aqueous solution. Adsorption kinetics was determined from the experimental data, and the results showed that pseudo-second-order kinetic model matched well for the adsorption of U(VI) onto humic acid. Thermodynamic parameters including free energy, enthalpy, and entropy of adsorption were obtained, and all the results were in favor of the adsorption. It was found that the adsorption rate was the best at pH 5.0. It can be concluded from FT-TR spectra that there is chemical adsorption in the U adsorption. [ABSTRACT FROM AUTHOR]

In this paper, batch removal of Brilliant Red HE-3B (BRed) and Methylene Blue (MB) dyes onto apple seeds powder was studied in order to evaluate the sorptive properties of this food waste. The experimental data equilibrium was analyzed using the Langmuir, Freundlich, and Dubinin–Radushkevich adsorption models. Results of the study reveal that the Langmuir model best describes the dyes sorption processes. The monolayer sorption capacity was established to be 66.225 mg/g BRed and, respectively, 26.316 mg/g MB at 25°C. The values of the mean free energy obtained from the Dubinin–Radushkevich model indicated a porous structure of the sorbents and suggest that physical sorption is the main sorption type involved in the studied processes. The values of the thermodynamic parameters (ΔG, ΔH, and ΔS) showed that sorption of tested dyes was feasible, spontaneous, and endothermic under examined conditions. The Fourier transforms infrared spectroscopy has been used to investigate the interaction between apple seeds powder and dyes. Environmental scanning electron microscopy technique was used to analyze the surface morphology of the sorbent before and after dyes sorption. [ABSTRACT FROM AUTHOR]

A new carboxylate-functionalized sugarcane bagasse (SMA) was prepared via a solvent-free procedure involving esterification of sugarcane bagasse with Meldrum's acid. The optimized conditions provided SMA with a percent weight gain of 86.0% and 4.69 ± 0.20 mmol/g of carboxylic acid groups. SMA was characterized by FTIR, TGA, elemental analysis and SEM. Kinetic experiments showed that the amount of crystal violet adsorbed increased with increasing temperature and equilibrium was reached at 12 h. Adsorption kinetics followed a pseudo-second-order model. The Arrhenius and Eyring models were used to obtain the activation energy and changes in free energy, enthalpy, and entropy of activation for the adsorption process. The calculated activation energy (14.14 kJ/mol) suggested physical adsorption of CV onto SMA. The equilibrium data were well fitted to the Langmuir and Sips isotherms. Maximum adsorption capacity was 692.1 mg/g at 45 °C. Thermodynamic parameters such as changes in free energy, enthalpy and entropy were also determined. [ABSTRACT FROM AUTHOR]

Highlights: [•] Calcined Mussels shells considered as new and eco-friendly biosorbent to remove dyes. [•] Biosorption kinetics of Rhodamine B, Alizarin Red S and Orange II in a batch system was found to conform to pseudo-second order model. [•] The biosorption equilibrium was well described by the Langmuir isotherm model. [•] Thermodynamic studies indicated that biosorption process was spontaneous, endothermic for Alizarin Red S and Orange and physical reaction. [•] Thermodynamic studies indicated that biosorption process was spontaneous, exothermic for Rhodamine B and chemical reaction. [Copyright &y& Elsevier]

• Complexes with the formula [Cu(bq)(PR 3) 2 ]+ were synthesized. • [C u (bq) 2 ]+ were formed from the ligand redistribution reaction of [Cu(bq)(PR 3) 2 ]+. • The formation constant of [Cu(bq) 2 ]+ was solvent-dependant. • The electronic and steric characteristics of the phosphines affects the formation constant of [Cu(bq) 2 ]+. • The steric factor is more dominant. Complexes with the formula [Cu(bq)(PR 3) 2 ]+ {where bq = 2,2′-biquinoline and R = Ph (Cu-Ph-2), C 6 H 4 –4-OMe (Cu-OMe-2), C 6 H 4 –4-F (Cu-F-2), cyclohexyl (Cu-Cy-2)} were synthesized and characterized. The absorption and emission spectra of the complexes in dichloromethane indicated the presence of [Cu(bq) 2 ]+, resulting from the ligands redistribution reactions. The solvent-dependence of [Cu(bq) 2 ]+ formation from [Cu(bq)(PPh 3) 2 ]+ was investigated, highlighting a decrease in the formation constant in the order: DCM > ACE > DMSO > EtOH > MeCN. The presence of coordinating solvents lowers the formation constant; possibly through the formation of stable adducts with the formula [Cu(bq) 2 (PPh 3)(solvent)]+. Moreover, the electronic and steric aspects of the phosphines were explored for the redistribution reaction of [Cu(bq)(PR 3) 2 ]NO 3 in DCM. The steric environments of the phosphines in Cu-Ph-2, Cu-F-2 and Cu-OMe-2 are identical; the variable electronic properties caused increases in the homoleptic formation constant in the order: Cu-OMe-2 < Cu-Ph-2 < Cu-F-2. Moreover, comparison between the formation constants of [Cu(bq) 2 ]+ from Cu-Ph-2 and Cu-Cy-2 indicated higher values for Cu-Cy-2. Despite the strong electron-donating nature of PCy 3 , the high steric bulkiness induces the high formation constant. Calculations suggest that Cu-Cy-2 possesses longer Cu-P bonds, rationalizing the fast dissociation rate of PCy 3. Overall, the study highlights that the ligand redistribution equilibrium of [Cu(bq)(PR 3) 2 ]+ is dependant on the electronic and steric characteristics of the phosphine ligands. [Display omitted] [ABSTRACT FROM AUTHOR]

The kinetic and the thermodynamic characteristics of the physical and the physicochemical processes, taking place under thermal treatment of fly ash (FA) from lignite coals, were investigated. The obtained results are important for the thermal stability of this material, as well as for the determination of appropriate regimes for its zeolitization, vitrification and thermal activation. The thermal treatment is essential for the development of advanced technologies for utilization of ash residues. FA was subjected to differential thermal analysis (DTA) as the heating was performed at different rates: 2.5, 5.5, 11.0, 15.0, 25.0 and 35.0°Сmin−1. The obtained experimental thermograms were divided conditionally in three thermal zones: up to 200°C, 200–675°C and 675–950°C, where the following thermal effects were registered: first zone – an endothermic effect, attributed to the water desorption and the liberation of adsorbed gases; second zone – two exothermic effects, related to the chemical oxidation of the magnetite in the FA composition; third zone – a small endothermic effect in the interval 760–861°C related to the glass transition of the amorphous constituents of the FA. The activation energy Ea of the surface and the bulk oxidation of magnetite to hematite, corresponding to the exothermic peaks in the second zone, was calculated by the derived kinetic equations. The process thermodynamic parameters, such as enthalpy ΔH and entropy ΔS, were computed comparing the areas of the characteristic thermal effects of the investigated FA and an appropriate etalon. The values of Ea , ΔH and ΔS of the low- and the high-temperature oxidation were found to be =29.3kJmol−1, ΔHL =1.01kJmol−1, ΔSL =1.67Jmol−1 K−1, and =51.7kJmol−1, ΔHH =3.97kJmol−1 and, ΔSH =5.05Jmol−1 K−1, correspondingly. [ABSTRACT FROM AUTHOR]

Abstract: A zwitterionic 3-P,P-diphenylphosphonium-propylsulfate stationary phase called HZI was synthesized for hydrophilic interaction liquid chromatography (HILIC). A set of 15 solutes including apolar aromatic compounds, positively charged β-blockers, polar nucleic acid bases and negatively charged compounds was used to prepare van’t Hoff plots between 10 and 70°C with HILIC mobile phases containing between 10 and 20% v/v 20mM or 50mM ammonium acetate buffer (pH 4.1) in acetonitrile. The unique Π–Π interaction capability of the HZI phase is evidenced by the low but significant retention of the apolar aromatic compounds in the HILIC mode as well as by the strong retention of the aromatic containing β-blockers. The linear van’t Hoff plots gave the ΔH° and ΔS° thermodynamic changes of the solute transfer from the mobile to the stationary phase. Plotting the ΔH° values versus the corresponding ΔS° ones produced a line excluding the three apolar aromatic solutes and a negatively charged compound. The excluded compounds corresponded to curved van’t Hoff plots. If the non-linearity of van’t Hoff plots is classically explained by changes in solute transfer interactions, we showed that it could also be explained by a temperature induced change in the hydrated stationary phase volume seen by the solutes. [Copyright &y& Elsevier]

Abstract: This paper deals with the immobilization of various weight percentage of TiO2 on mesoporous MCM-41, characterization of the materials by X-ray diffraction (XRD), nitrogen adsorption–desorption, Fourier Transform Infrared (FTIR) analysis, UV–vis diffuse reflectance spectroscopy (DRS) and evaluation of the adsorption capacity toward Cr(VI) removal. It is found that the MCM-41 structure retained after loading of TiO2 but the surface area and pore diameter decreased due to pore blockage. Adsorption of Cr(VI) from aqueous state was investigated on TiO2-MCM-41 by changing various parameters such as pH, metal ion concentration, and the temperature. When TiO2 loading was more than 20wt.%, the adsorption activity (25)TiO2-MCM-41 reduced significantly due to considerable decrease in the surface area. It is also observed that TiO2 and neat MCM-41 exhibits very less Cr(VI) adsorption compared to TiO2-MCM-41. The adsorption of Cr(VI) onto (20)TiO2-MCM-41 at pH∼5.5 and temperature 323K was 91% at 100mg/L Cr(VI) metal ion concentration in 80min. The experimental data fitted well to Langmuir and Freundlich isotherms. The adsorption of Cr(VI) on TiO2-MCM-41 followed a second order kinetics with higher values of intra-particle diffusion rate. Thermodynamic parameters suggested that the adsorption process is endothermic in nature and desorption studies indicated a chemisorption mode. [Copyright &y& Elsevier]

Abstract: A highly porous metal-organic framework (MOF) material based on chromium-benzenedicarboxylates (MIL-101) was applied to the adsorption of xylenol orange (XO) from aqueous solution. Adsorption kinetics and isotherms were determined from the experimental data, and the results showed that pseudo-second-order kinetic model and Langmuir adsorption isotherm matched well for the adsorption of XO onto MIL-101. Thermodynamic parameters including free energy, enthalpy, and entropy of adsorption were obtained, and all the results were in favor of the adsorption. It was found that the adsorbed amounts decreased with increasing pH value of the XO solution, which indicates that the mechanism may be the charge interactions between the dye stuffs and the adsorbents. The used MIL-101 could be regenerated by washing with a dilute concentration of NaOH solution. Compared with other adsorbents like active carbon and MCM-41, especially in high concentrations of XO, MIL-101 demonstrated a superior dye adsorption capability. [Copyright &y& Elsevier]

Abstract: Microparticles with complex architectures based on the polyelectrolyte complexes between an acrylic ion exchange resin and two polysaccharides: gellan and xanthan gum were prepared and used for the adsorption of antibiotic in order to obtain a new drug delivery systems. Batch adsorption studies have been carried out to determine the effect of the contact time, temperature and the initial concentration of drug solution on the adsorption behavior. The Langmuir, Freundlich, Temkin and Dubinin–Radushkevich adsorption isotherms were used to model this behavior. The kinetics were fitted with the pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion models. The best results were achieved with pseudo-second order kinetic model. The thermodynamic parameters (ΔG, ΔH, ΔS) were also calculated and the values indicate that the adsorption process was endothermic and spontaneous. The results showed that the microparticles with complex structures have a higher adsorption capacity, making it suitable for use in drug delivery systems. [Copyright &y& Elsevier]

Abstract: This paper deals with an investigation on coir-based adsorbent, puresorbe, in the removal of chromium(VI) from the aqueous solutions. The adsorption of chromium(VI) was carried out by varying the parameters such as agitation time, metal concentration, adsorbent dose, temperature and pH. The experimental isotherm data were analyzed using Langmuir, Freundlich and Redlich and Peterson isotherms. Adsorption followed second order rate expression for the particle size 250–500μm at pH 2. The monolayer adsorption capacity is 76.92mg chromium(VI) per gram of puresorbe. Thermodynamic parameters show the endothermic nature of chromium(VI) adsorption. Desorption study carried out using distilled water adjusted to pH of 2–10, suggests that chemisorption might be the mode of adsorption. [Copyright &y& Elsevier]

Abstract: Oxidation of penicillin derivative, ampicillin (AMP) by diperiodatocuprate(III) (DPC) in alkaline medium at a constant ionic strength of 0.01-moldm−3 was studied spectrophotometrically. The reaction between DPC and ampicillin in alkaline medium exhibits 1:4 stoichiometry (ampicillin:DPC). Intervention of free radicals was observed in the reaction. Based on the observed orders and experimental evidences, a mechanism involving the protonated form of DPC as the reactive oxidant species has been proposed. The oxidation reaction in alkaline medium has been shown to proceed via a DPC–AMP complex, which decomposes slowly in a rate determining step to yield phenyl glycine (PG) and free radical species of 6-aminopenicillanic acid (6-APA), followed by other fast steps to give the products. The two major products were characterized by IR, NMR, LC–MS and Spot test. The reaction constants involved in the different steps of the mechanism were calculated. The activation parameters with respect to slow step of the mechanism were computed and discussed and thermodynamic quantities were also determined. [Copyright &y& Elsevier]

Abstract: Goethite (α-FeOOH), lepidocrocite (γ-FeOOH), hematite (α-Fe2O3) and maghemite (γ-Fe2O3) constitute the main natural occurrences with magnetite (Fe3O4), for ferric oxides and oxyhydroxides. By thermal dehydrations goethite and lepidocrocite respectively give rise to hematite and maghemite by topotactic transformations. In fact, this kind of transformation permits alone to explain why hematite, the most stable oxide in a thermodynamical point of view, is not obtained directly by dehydration of lepidocrocite. Topotactic transformations can only exist between solids displaying structural relationships. In these conditions, atom displacements are reduced so that dehydration processes are performed at a relatively low temperature and then clear vectorial relations can be established between crystal parameters of the two structures. Therefore, we can consider that trivalent iron oxyhydroxides and oxides, belong to two different structural types: goethite/hematite type and lepidocrocite/maghemite type and conclude that, in this case, kinetic phenomena are more important than laws of thermodynamic for explaining the experimental results found. [Copyright &y& Elsevier]

In this work, we examined the possibility on the application of rice husk as biosorbent for the elimination of heavy metal ions (chromium, lead, and zinc) existing in the aqueous solutions. The biosorbent was prepared from rice husk powder and modified with 0.1 N of HCl for creating the functional groups and increase specific surface area. The FT-IR spectra, SEM& EDX studies of rice hulls powder were examined for the pristine adsorbent and after the adsorption of heavy metal ions. The batch adsorption technique was adopted for this work and adsorption parameters were optimized. The maximum efficiency of adsorption is obtained at 6.0 pH, 1 h of contact duration, the rice husk dosage is 2.5 g/L, and temperature of 30°C for 25 mg/L of Cr, Pb & Zn metal ion solutions. The Cr, Pb & Zn metal ions are removed up to 87.12 %, 88.63 % & 99.28 %, respectively, using the rice husk powder. The adsorption process follows the Temkin & D-R isotherm model. Elovich model was fitted against the kinetic data of metal ion adsorption. Based on the experimental observations, the rice husk powder can be considered as a low cost adsorbent for heavy metal ion removal from the industrial effluent. [Display omitted] • This experimental study provides the details of the production of low cost adsorbent material from rice husk powder. • Adsorptive removal of Cr, Pb & Zn metal ions was investigated by batch mode. • The maximum adsorption efficiency of 87.12% for chromium, 88.63 % for lead and 99.28 % for zinc heavy metal ions was attained. • The maximum amount of desorption was attained by adding 0.2 N of HCl in the adsorbate material. [ABSTRACT FROM AUTHOR]

Caffeine is an emerging pollutant and is considered the most representative pollutant of the Pharmaceutical Active due to its high consumption by the general population. It can be used to track pollution caused by humans. Different technologies have been employed to remove the caffeine from aqueous media, however the adsorption has been preferred due to its simplicity, high removal efficiency, operational and implementation facility and low cost. This paper provides a systematic review of the published peer-reviewed literature concerned with caffeine removal by the adsorption process. The Scopus and ScienceDirect databases were used to identify relevant articles researches on caffeine removal. Many authors have studied caffeine's adsorption equilibrium in aqueous media, different conditions, and different adsorbents. This paper aims to uncover the overall trend of adsorbent used, kinetic and thermodynamic studies. The impact of pH, temperature, adsorbent dosage and competitive effect were presented and analyzed. It was observed that the adsorption capacities ranged between 10 and 1000 mg g−1, according to the nature and properties of the adsorbent. The pseudo-second order (kinetic model) and the Langmuir isotherm model showed the best adjustment of the experimental data from caffeine adsorption in most studies. The mechanistic understanding of adsorption and the development of new adsorbents are still a matter of future research, as well as the use of other kinetic models based on statistical factors and the thermodynamic studies should be considered. Unlabelled Image • The effect of physicochemical factors on the adsorption efficiency is discussed. • The mechanism for the adsorption of caffeine on different adsorbents was presented. • Some structural properties (S BET and V p) of adsorbents were presented and discussed. • The thermodynamic data, isotherm models, and kinetic models are compiled. • Adsorption is certainly an efficient method for caffeine removal. [ABSTRACT FROM AUTHOR]

A series of isostructural water stable UiO-66-X (X = H, NH 2 , NO 2), one of the most well-known metal-organic framework (MOF) materials, was synthesized by solvothermal synthesis. Their dye adsorption capacity toward a neutral dye, Phenol Red (PR), was investigated for the first time in this research in order to elucidate how the functional group of the organic linker contribute to the adsorption capacity. The operational parameters, i.e. pH, adsorbent concentration, initial dye concentration, contact time and temperature were monitored. The maximum adsorption capacities of UiO-66, UiO-66-NO 2 and UiO-66-NH 2 were measured to be 19 mg/g, 11 mg/g and 27 mg/g, respectively. The adsorption kinetics of all three adsorbents were similar and fitted best with pseudo-second-order kinetics model. Adsorption isotherms of the adsorbents can be explained by Freundlich model which suggests that the adsorption of PR on the adsorbents can be both physisorption and chemisorption. Thermodynamic studies indicated that the adsorption process in all studied adsorbents was spontaneous, endothermic and entropic-driven which was confirmed by the obtained thermodynamic variables. Functional group of the organic ligand was found to contribute significantly to the adsorption capacity of MOFs. The adsorbent with a functional group that can create more intermolecular forces will enhance the adsorption capacity. Experimentally, UiO-66-NH 2 showed the highest adsorption capacity when compared to UiO-66 and UiO-66-NO 2. Image 1 • Adsorption capacity toward Phenol red in UiO-66-NH 2 is 2.5 times higher than that in UiO-66-NO 2. • Neutral dye adsorption capability of UiO-66 is 4 times lesser than in that of charge dye. • Their adsorptive behavior fits well with Freundlich model. • Their adsorption kinetics can be best described by pseudo-second-order kinetics model. • Thermodynamic studies suggest that adsorption process is spontaneous, endothermic and entropic- driven. [ABSTRACT FROM AUTHOR]

Photothermal sensor require liquid media with its conductivity significantly changed at different temperature. Owing to the outstanding advantage of easy synthesizing procedure and high tunability, deep eutectic solvents (DESs) might be the promising candidate for the highly efficient photothermal sense. Herein, several DESs composed by DBU/DBN and LiTf 2 N/LiBr were used as liquid media of sensor, among which DBU:LiTf 2 N (4:1) exhibits the excellent thermal response ability. The near-infrared light (NIR) photothermal sensor was simultaneously constructed through blending photothermal conversion materials polydopamine (PDA) with DBU:LiTf 2 N (4:1) and it indicates the higher NIR photothermal response than that of ionic liquids-based media. On-off cycles of NIR photothermal response show that the reusability of DESs is favorable. This work provides a sustainable method for achieving the highly efficient photothermal sensor by using DESs. Highly efficient photothermal sensor is achieved by using thermal-sensitive deep eutectic solvents. Unlabelled Image • Highly thermal-sensitive DESs composed by DBU/DBN and LiTf 2 N/LiBr. • Pioneering work of NIR photothermal response by blending DBU:LiTf 2 N (4:1) with PDA particles. • Highly NIR light photothermal efficiency of PDA particles. [ABSTRACT FROM AUTHOR]

• Short-staple microfibers (SSM) from different sources were fabricated via a wet rotate-spinning technique. • SSMs were employed for removal Cr(IV) from aqueous solution for the first time. • Effects of pH value, fiber dose on the adsorption efficiency of Cr(VI) were investigated. • Physical, chemical, kinetics and thermodynamic properties were studied and evaluated. Short staple microfibers (SSM) based on chitosan (CS) or silk fibroin (SF) were fabricated via the wet-rotate-spinning technique and employed to adsorb hexavalent chromium from aqueous solution. Adsorption efficiencies, physicochemical and morphological properties of CS and SF-SSM were systematically investigated and evaluated before and after adsorption of Cr(VI) using different techniques like ATR-FTIR, TGA, XRD, XPS, and SEM. CS and SF-SSM showed removal efficiency (>90 %) toward Cr(VI) ions. Pseudo-second order kinetic and Langmuir isotherm models could describe the Cr(VI) ions uptake process. Considering the inexpensive, sustainability and higher adsorption capacity of CS and SF-SSM hold great promising applications as natural adsorbent materials for removing different hazardous metals from aqueous medium. [ABSTRACT FROM AUTHOR]

Toxic metals can be present in the environment, causing negative effects on the ecosystem and human health. Although several technologies have been used for decontamination purposes, biosorption is an environmentally friendly and cost-effective alternative to remove toxic metals from wastewater. Agricultural biomasses are a class of biosorbents that offer several advantages, including their low cost, availability in nature, simplicity to be obtained and used as adsorbents. This review article is focused on the use of agricultural biomass materials for the removal of toxic metal(oid)s from contaminated aqueous matrices. In addition, raw and modified forms of these biosorbents are considered as precursors for the preparation of other adsorbents like biochar. Following agricultural biomasses are discussed: i) watermelon, ii) potato, iii) cucumber, iv) peanut, v) almond, vi) walnut and hazelnut, vii) pistachio, and viii) tea waste-based biosorbents. The adsorption potential of the biomasses is exhibited under the optimum experimental conditions, and their characterization and possibility to reuse is also considered. Moreover, isotherm and equilibrium parameters of the metal(oid) adsorption by the biomasses are discussed. Specifically, thermodynamic studies are described in order to better understand the nature of the biosorption process between contaminant and biomass. All these considerations reflect the high potential of agricultural waste-based adsorbents for toxic metal(oid)s removal related to wastewater treatment technologies. Unlabelled Image • Review on the use of agricultural biomasses as adsorbents for toxic metal removal • Comprehensive compilation of factors affecting the adsorption • Presentation and summary of best isotherm, kinetic models and maximum adsorption capacities • Extensive discussion of the thermodynamic aspects associated with the adsorption process [ABSTRACT FROM AUTHOR]

Spectrophotometric procedures were presented for the determination of antihistaminic drug, emedastine difumarate. The methods are based on the charge transfer complexation reaction of the drug with π-acceptors; 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), chloranilic acid (CA) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). Different charge-transfer complexes and colored radical anions were obtained. The formations of the colored complexes were utilized in the development of simple, rapid and accurate spectrophotometric methods for the analysis of emedastine in drug substance and products. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9996–0.9999) were found between the absorbance at the relevant maxima and the concentrations of emedastine in the range of 0.8–200 μg mL −1 . The limits of detection ranged from 0.06 to 0.76 μg mL −1 . The molar absorptivities and association constants for the colored complexes were evaluated using the Benesi–Hildebrand equation. The free energy change (Δ G °) and the enthalpy of formation (Δ H °) as well as the entropy (Δ S °) were also determined. The methods were successfully applied to analyze the drug formulation with mean recovery percentages ± RSD% of 100.04 ± 0.59–100.22 ± 0.72. The results were compared favorably with the official and reported methods. [ABSTRACT FROM AUTHOR]

Adsorptive removal of a cationic dye – Rhodamine B – from aqueous solutions was achieved by the use of Animal Bone Meal as a new low cost adsorbent. Adsorption of Rhodamine B was occurred by studying the effects of contact time, adsorbent amount, dye concentration and temperature. Dye adsorption equilibrium was rapidly attained after 60 min of contact time. The isotherms of adsorption data were analyzed by Langmuir and Freundlich adsorption isotherm models. The adsorption capacity ( Q m ) obtained from the Langmuir isotherm plots was 62.11, 63.69, 64.13 and 64.95 mg/g, respectively at 303, 313, 323 and 333 K. Thermodynamic parameters such as Δ H 0 , Δ S 0 and Δ G 0 were calculated, which indicated that the adsorption was spontaneous and endothermic nature. The characteristic results and dimensionless separation factors R L showed that Animal Bone Meal can be employed as an alternative to commercial adsorbents in the removal of Rhodamine B from aqueous solution and wastewater. [ABSTRACT FROM AUTHOR]