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Purpose: In order to investigate the desorption effect and mechanism of petroleum from petroleum contaminated soil (PCS) in surfactant solution (SAA-solution). Method: In this study, the desorption effect of SAA-solution cleaning of PCS was systematically analyzed by using orthogonal experiments. In addition, the petroleum mechanism of desorption from the PCS surface was further explored by kinetic and thermodynamic studies. Results: The results indicated that the petroleum removal efficiency (Re) gradually decreased with the increase of PCS particle size and PCS aging time. The highest petroleum Re was 82.13% under optimum conditions. Subsequently, FT-IR and petroleum component analysis showed the petroleum light components were easily removed from PCS, while the petroleum heavy components limited the desorption of petroleum. The kinetic studies revealed that the petroleum desorption was well depicted by the pseudo-first-order kinetic model, and the desorption rate increased with the decrease of PCS particle size. Meanwhile, the petroleum desorption equilibrium was well described by the Langmuir isotherm model and proceeded by a chemical mechanism. The thermodynamic studies demonstrated that the petroleum desorption from PCS was a viable, spontaneous, and endothermic process. Conclusion: The study provided theoretical guidance to apply SAA-solution cleaning industrial PCS. [ABSTRACT FROM AUTHOR]

A novel method has been explored based on the recovery of two industrial wastes V2O5 and phosphogypsum from the fertilizer production industry, which also provide a significant challenge due to their toxicity and environmental impact. To solve the problem of these two harmful wastes, these residues have been transformed into valuable resources, by the elaboration of Nanoparticles vanadate-hydroxyapatite (NPs-HAP/VAP) adsorbent, contributing a sustainable solution without requiring expensive or highly skilled work. This comprehensive investigation explores the adsorption of the reactive red 141 dye (RR 141) on Ca10(VO4) x(PO4)6-x(OH)2, with (xi = 0, 1.5, 3, 4.5, and 6). Using a Centered composite design (CCD), several parameters influencing the adsorption process were examined. The optimal adsorption capacity is 50 mg. g - 1 under optimal conditions 57.5 mg of the adsorbent dose, 152.5 mgL-1 for the RR 141, pH 8, 92.5 minutes of contact time, and incorporation ratio of 4.5 with an R2 of 0.99. These results reinforce the effectiveness of our chosen CCD model. Kinetic analysis demonstrated a pseudoorder reaction model with an R² > 0.92, while the Sips isotherm describes the adsorption process. Thermodynamic studies revealed spontaneous adsorption, suggesting a physical character enhanced by a positive entropy variation. [ABSTRACT FROM AUTHOR]

The adsorption of a model protein such as bovine serum albumin (BSA) on a magnetic material based on montmorillonite (MtMag) was studied. Kinetic data, equilibrium isotherms, and thermodynamic calculations were performed and analyzed to obtain information about the rate-limiting step of the adsorption process and propose a possible adsorption mechanism. Equilibrium studies showed optimal adsorption around pH 4.5, the maximum adsorption capacity being around 231.9 mg g-1 at 25 °C. The latter behavior may be ascribed to the most packed protein conformation at pH conditions near the BSA isoelectric point. In addition, the BSA adsorption capacity decreased with the ionic strength (10–3−10–1 M) and increased with the temperature (15–30 °C). In all cases, the Sips model yielded the best fit to the experimental results. The thermodynamic analysis revealed an isosteric heat dependence on the coverage, which allowed ruling out the Langmuir model. The kinetic data were adequately fitted by the IPD model, which suggests that the rate-limiting step of the adsorption process is the diffusion of BSA molecules into the internal sites. [ABSTRACT FROM AUTHOR]

Copyright of Nativa is the property of Revista Nativa and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The potential usage of activated carbon from plantain peel (Musa paradisiaca) (TPPC) and unactivated carbon from plantain peel (UPPC) for the removal of Hexachlorocyclohexanes (HCHs) from water systems was investigated. The TPPC and UPPC were characterized using Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). Adsorption experiments were conducted as a function of adsorbent weight (2 – 10 g), temperature (30 -50 °C), and solution pH (2 - 9) under an adsorbent packed column. The Optimum removal efficiency of 98.23 % was achieved in the column studies under the following conditions: pH = 5, the dosage of adsorbent = 5 g/100 mL, temperature = 30 °C. The batch adsorption process was employed to evaluate the kinetics, equilibrium, and thermodynamics of the adsorption processes. The equilibrium study showed that Langmuir among other isotherm models applied performed better in fitting the data. Additionally, the kinetic data was best described by the pseudo-second-order model (R2 > 0.97), indicating a chemisorption mechanism. Furthermore, the thermodynamic calculations of the adsorption process suggest that HCH adsorption was exothermic (ΔH = -110.87) and spontaneous (-ΔG).

This work investigates the adsorptive properties of Pyracantha coccinea berries powdered biomass (BPC) towards Reactive Red 120 (RR120) in an aquatic system. The morphological and structural features of BPC particles were examined before and after the adsorption of RR120 through field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (XEDS), elemental analysis and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). Various adsorption parameters were explored. The application of adsorption isotherms and kinetic models showed that Langmuir and PS2 models provide the best fitting parameters (R2 > 0.99). The qmax is calculated to be 22.01 mg/g at pH 2.0 and T= 295 K. The relative removal efficiency rises with temperature from qmax = 22.01 mg/g (295 K) to qmax = 31.2 mg/g (323 K) and the positive ΔH0 value obtained from the thermodynamic study indicates an endothermic and entropy-governed adsorption process. The increase of the ionic strength was found to favor the dye removal and the associated qmax values increased from 21.2 mg/g to 28.9 mg/g.

This paper presents tests related to the reactivity of commercial Hi-Fuel sorbent toward H2S (H2S/N2 mixture) in a packed bed at 300 °C. The sorbent used for breakthrough test was characterized before and after test by ESEM-EDX, FTIR-ATR, Raman, and elemental analyses. Testing reveals that the commercial sorbent contains two compounds reacting with H2S: ZnO and ZnCO3. According to thermodynamical studies, the reactivity of ZnCO3 at 300 °C is privileged (KR = 9.5 × 108) than ZnO (KR = 6.6× 106). In addition, the reaction of H2S with ZnCO3 induces a volume decrease, which promotes the movement of gas through the newly formed layer. The properties of this sorbent thus hold a good potential for the desulfurization process of gases polluted with H2S. We observed that the maximum sulfidation rate was reached on the surface of the sorbent and showed a maximum conversion of 27%. [ABSTRACT FROM AUTHOR]

ZSM-5 zeolite modified with acetic acid eggshell and chitosan was impregnated in three distinct proportions. As nanocomposites (NCs), the purpose of the composites was to adsorb Acid Red 1 dye (AR-1) from an aqueous solution. The characterization of chitosan@CaO/zeolite NCs included (CHT)1@(CaO/ZT)1, (CHT)1.5@(CaO/ZT)1, and (CHT)1@(CaO/ZT)1.5, as determined by FTIR, XRD, EDX, BET, TGA, and UV- Visible absorption spectroscopy. In a bulk system, the adsorption of the AR-1 dye onto (CHT)1@(CaO/ZT)1.5 was analyzed in terms of solution temperature, pH, contact time, and NCs dosage. The most favorable parameters for achieving efficient dye adsorption were: a pH of 2, an adsorbent dosage of 0.05 g/25 mL of dye solution, and 20 mg/L of dye concentration at 22°C temperature. The reaction reached equilibrium after 120 min. The estimated adsorption efficiency of the AR-1 dye by the prepared NCs is 99.70%. The mechanism by which the dye was sequestered onto (CHT)1@(CaO/ZT)1.5 was exothermic. The correlation coefficient (R²) for the pseudosecond-order adsorption kinetic model held true at different temperatures with a value of 0.99, indicating that the model accurately described the chemical interaction between the adsorbent and Acid Red (AR-1). Adsorption processes are characterized as exothermic, feasible, and spontaneous when the Gibbs free energy (ΔG°) and enthalpy (ΔH°) changes have negative values, respectively. It was determined that the Langmuir model best described the isotherm behavior of AR-1 dye adsorption onto (CHT)1@ (CaO/ZT)1.5. Under ideal conditions, the surface was found to be homogeneous and had a maximum adsorption capacity (qm) of 84.03 mg/g. [ABSTRACT FROM AUTHOR]

Water is one of the fundamental resources for the existence of humans and the environment. Throughout time, due to urbanization, expanding population, increased agricultural production, and intense industrialization, significant pollution with persistent contaminants has been noted, placing the water quality in danger. As a consequence, different procedures and various technologies have been tested and used in order to ensure that water sources are safe for use. The adsorption process is often considered for wastewater treatment due to its straightforward design, low investment cost, availability, avoidance of additional chemicals, lack of undesirable byproducts, and demonstrated significant efficacious potential for treating and eliminating organic contaminants. To accomplish its application, the need to develop innovative materials has become an essential goal. In this context, an overview of recent advances in hydrogels based on chitosan and nanocomposites and their application for the depollution of wastewater contaminated with dyes is reported herein. The present review focuses on (i) the challenges raised by the synthesis process and characterization of the different hydrogels; (ii) the discussion of the impact of the main parameters affecting the adsorption process; (iii) the understanding of the adsorption isotherms, kinetics, and thermodynamic behavior; and (iv) the examination of the possibility of recycling and reusing the hydrogels. [ABSTRACT FROM AUTHOR]

In this work, copper oxide nanoparticles (CuO NPs) were successfully synthesized by a simple chemical process. After conjugation of 3-glycidoxypropyltrimethoxysilane (GPTMS), the surfaces of CuO NPs@ GPTMS were functionalized with hyaluronic acid (HA) and folic acid (FA) for the formation of CuO NPs@ GPTMS@HA-FA. The samples were characterized by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). Surface modification of CuO NPs with Fourier-transform infrared (FT-IR), thermo-gravimetric analysis (TGA), and CHN analysis was proven. Imatinib mesylate (IM) adsorption was studied under various conditions. The maximum sorption capacity was achieved at pH = 6, a contact time of 30 min, an adsorbent dosage of 0.01 g, and a temperature of 298 K. The evaluation of kinetic and isotherm models showed that the pseudo-second-order and Langmuir models were selected as the best fitting model to describe the adsorption method. In vitro release investigations of IM from the CuO NPs@ GPTMS@HA-FA were performed in stimulated human blood fluid (pH = 7.4) and cancer fluid (pH = 5.6) at 37 °C. Release of − 47.10% of IM from CuO NPs@ GPTMS@HA-FA was observed within a period of 6 h at pH = 5.6. The investigation shows that IM, an anticancer drug can be successfully entrapped in the CuO NPs@ GPTMS@HA-FA for the targeted delivery of cancer therapy. [ABSTRACT FROM AUTHOR]

This paper presents tests related to the reactivity of commercial Hi-Fuel sorbent toward H2S (H2S/N2 mixture) in a packed bed at 300 °C. The sorbent used for breakthrough test was characterized before and after test by ESEM-EDX, FTIR-ATR, Raman, and elemental analyses. Testing reveals that the commercial sorbent contains two compounds reacting with H2S: ZnO and ZnCO3. According to thermodynamical studies, the reactivity of ZnCO3 at 300 °C is privileged (KR = 9.5 × 108) than ZnO (KR = 6.6× 106). In addition, the reaction of H2S with ZnCO3 induces a volume decrease, which promotes the movement of gas through the newly formed layer. The properties of this sorbent thus hold a good potential for the desulfurization process of gases polluted with H2S. We observed that the maximum sulfidation rate was reached on the surface of the sorbent and showed a maximum conversion of 27%.

Kinetic, isothermal and thermodynamic studies for the oil spills removal process have been conducted by Chitosan and novel amphiphilic Chitosan-g-Octanal Schiff base adsorbents developed by click chemistry and evaluated successfully in the removal of heavy crude oil spills. Chitosan was first prepared from wastes of marine shrimp shells, and then Chitosan and Chitosan-g-Octanal Schiff base adsorbents were synthesized and verified their structures, thermal stability and their morphological changes using FT-IR spectroscopy, TGA and SEM. The oil adsorption percentages (%) using heavy crude oil were 96.41% for the Chitosan-g-Octanal Schiff base adsorbent compared to 64.99% for native Chitosan counterpart. High rate of adsorption was observed where 40% of oil adsorbed within 15 min only using the Chitosan-g-Octanal Schiff base adsorbent compared to 90 min for native Chitosan adsorbent. 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 30.30 g/g at 25 °C. Thermodynamic parameters computed from Van't Hoff plot confirmed the process to be endothermic, favorable and spontaneous. [ABSTRACT FROM AUTHOR]

• 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]

The present work investigated the kinetic and thermodynamic study of adsorbents to remove copper ions from aqueous solutions and compared the efficiency between the natural microalgae bio-adsorbent chlorella species (sp.) and synthetic magnetic nanoparticles. All materials synthesized and characterized by Fourier transform infrared (FT-IR), scanning electron microscope (SEM), energy dispersive X-ray (EDX). The highest Cu+2 ion adsorption for the copper solution at 100 mg/L was 57.2%, while at pH 8 it was 59.7%. The more efficient adsorbent for Cu+2 acquired by chlorella was 0.24 mg/g. The second-order kinetic model is fitted, the activation energy (Ea) for the three adsorbents; Chlorella, Fe3O4, (Fe3O4 coated with SiO2) were 95.24, 40.69, 20.39 kJ/mol, respectively indicating the adsorption process is slower than the magnetic nanoparticles. Enthalpy activation changes (ΔH#) were endothermic and showed that the adsorption of the Cu+2 on the chlorella was chemisorption and on the magnetic nanoparticles was physisorption. Entropy change of activation (ΔS#), and activation Gibbs free energy change (ΔG#) showed that adsorption process of Cu+2 on the three adsorbents was feasible and spontaneous in temperature range 293-313 K. The novelty of this work is to determine the type and efficiency of adsorption of algae and nanoparticles. [ABSTRACT FROM AUTHOR]

A new hybrid cation exchange material PANI-Ti(IV) phosphosulphosalicylate was synthesized by intercalating polyaniline (PANI) into Ti(IV) phosphosulphosalicylate (Ti(IV) PSS) using sol-gel chemical route. Then, it is renewed into H+ form and used as an adsorbent for the removal of Pb(II) from aqueous solution. The morphology and structure properties of the as prepared hybrid cation exchange material were characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET), thermo gravimetric analysis (TGA-DTG), and Transmission Electron Microscopy (TEM). The sorption experiment for Pb(II) removal was performed using batch method. Dependence of adsorption on contact time, exchanger dose, Pb(II) initial concentration, pH, and temperature has been studied to achieve the optimum conditions. The adsorption isotherm, kinetics, and thermodynamics of PTPSS for Pb(II) were studied. The results of the above mentioned analyses show that the adsorption isotherm process of Pb(II) on PTPSS was closely related to Langmuir model (r2 > 0.998). The adsorption kinetic process fits well with the pseudo-second order equation. Thermodynamic studies suggested the spontaneous and exothermic nature of PTPSS system. The ion exchange adsorbent shows ion exchange capacity for Li+, Na+, and K+ ions have been found to be 1.75, 2.24, and 2.41 meq/g, respectively. Its selectivity was examined by achieving some important binary separations like Pb2+- Cd2+, Pb2+- Hg2+, Pb2+- Cu2+, Pb2+- Zn2+, Pb2+- Ni2+, and Pb2+- Fe3+ on its column. On the basis of distribution studies (Kd values), PTPSS was highly selective for Pb(II). Therefore, the hybrid cation exchange material PTPSS can be used as a potential ion exchange material for the selective separation of Pb(II) ion in environmental remediation. [ABSTRACT FROM AUTHOR]

Water pollution is one of the most serious environmental issues facing the world, including India. The present study mainly focuses on removal of major pollutant from agriculture wastewater that is responsible for eutrophication in water, that is, phosphates. Fish scales and Hami‐melon peels were used as adsorbents in this investigation. Numerous studies are carried out for how effective adsorbents are at removing the pollutant phosphate. Equilibrium studies, thermodynamic studies, kinetic studies, and isotherm studies are all variations of these types of investigations. According to investigations, both the adsorbents of 0.2% concentration at 165 rpm with pH 6 and a constant temperature of 30°C can successfully remove 95%–97% of phosphate. The initial concentration of the pollutant was also varied from 30 to 70 ppm and the pH is varied from 3 to 9 which showed the maximum adsorption occurred in the range of 5–7. Additionally, contact time varied at an intervals of 10 min to determine the optimum contact time and was found to be 140 min. The uptake capacities 24.15 mg/g for fish scales as adsorbent whereas 23.94 mg/g for Hami melon peels as adsorbent. The isotherm studies showed that Langmuir isotherm fits well where second order kinetics is suited based on kinetic studies. The thermodynamic studies showed that fish scales and Hami melon peels are suitable to remove phosphates since the adsorption occurred is spontaneous and the reaction is endothermic in nature. [ABSTRACT FROM AUTHOR]

Copyright of Nativa is the property of Revista Nativa and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Metal corrosion is brought about by the oxidation of atoms on the surface resulting in irreversible damage to structures at staggering costs. Hence, the search for efficient and cost-effective corrosion inhibitors is relevant. In this study, the ethanolic extract of Red Dragon Fruit (Selenicereus costaricensis) waste peels (RDF) has been tested for its anti-corrosion property using the weight loss method at different temperatures (303-343 K). The calculated inhibition efficiency of 2% RDF is 97%. Thermodynamic studies reveal that increasing inhibitor concentration raises the activation parameters of mild steel in acidic media such as activation energy (Ea) and changes in enthalpy (ΔHo) and entropy (ΔSo). Moreover, increased immersion time, inhibitor concentration, and temperature led to increased inhibition efficiency. The spontaneous process (Δ Goads = -23.47 kJ/mol) of adsorption of RDF on mild steel surfaces obeys the Langmuir isotherm model. Lastly, optical microscopy of the inhibited and uninhibited systems confirms the potential of the RDF against pitting corrosion. [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]

The present study is aimed at the utilization of waste polyurethane (PU) foam derived magnetized carbon material for the treatment of simulated dye effluent. Activated carbon (AC) was prepared from waste PU foam by chemical activation method using K2CO3. The surface of the prepared AC was incorporated with nano-sized iron oxide particles to aid the recovery of the spent adsorbent. The polyurethane derived AC-iron oxide (PUAC-Fe3O4) nanocomposites were characterized with FE-SEM, XRD, Vibrating Sample Magnetometer (VSM), FT-IR, TGA, surface area and point of zero charge. The morphology of the prepared AC had an extremely porous texture which was incorporated with iron oxide nanoparticles of size less than 100 nm with a surface area of 250 m2/g. The nanocomposites had superparamagnetic properties as evident from the VSM plot. The prepared PUAC-Fe3O4 nanocomposites was used for the removal of Rhodamine B (RB) dye. Batch adsorption studies were performed and the equilibrium parameters were calculated by fitting the data with Langmuir and Freundlich isotherm models. The thermodynamic parameters were also evaluated. The adsorption of RB dye onto PUAC-Fe3O4 composites was spontaneous and endothermic. Kinetic studies were also carried out and the data were tested with different kinetic models. Intraparticle diffusion model and Boyd plots suggested that the boundary layer diffusion step controlled the rate of adsorption. Continuous column studies were also performed and it proved that 1 g of prepared material was able to treat 1.075 L of 10 mg/L RB dye with an efficiency of 64.87%. The interferential effect of the electrolytes on the RB dye removal was also studied. Reusability studies proved that the prepared PUAC-Fe3O4 nanocomposites was efficient even after three cycles of operation. [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]

Adsorption is one of the most versatile and widely used techniques for the removal of toxic metals from the aqueous solutions. Cadmium is the toxic metal selected for adsorption in this study and adsorbent of interest was activated carbon prepared from Bauhinia purpurea leaves as a plant biomass. The following process parameters were investigated during the batch adsorption process: The adsorption efficiency and cadmium deposition on the adsorbent surface were increased from 15.95 to 89.98%, 0.074 to 0.418 mg/g, and 7.27 to 89.97%, 0.034 to 0.418 mg/g with increasing contact time from 2 to 50 min and pH from 2 to 6.5, respectively. The adsorption efficiency was decreased from 89.98 to 45.96% and the amount of cadmium deposited on the surface of the ACBPL adsorbent was increased from 0.418 to 1.032 mg/g with an increase in solute concentration. The adsorption efficiency of cadmium decreased from 98.41 to 84.51% and 0.457 to 0.392 mg/L with an increase in particle size from 74 to 177 μm. The rate of adsorption of cadmium was increased from 61.31 to 96.34% with an increase in dosage of the ACBPL adsorbent from 0.05 to 0.15 g. The adsorption efficiency and cadmium deposition was decreased from 89.98 to 97.90%, 0.418 to 0.454 mg/g as the temperature increased from 303K to 323K. The variation of thermodynamic energy parameters (ΔG°, ΔH° and ΔS°) with the solution temperature described that the adsorption process is endothermic, spontaneous at high temperatures and non-spontaneous at low temperatures. The positive value of ΔS, reflecting the high degree of disorder in the adsorbent/adsorbate interface that is formed during the transition. [ABSTRACT FROM AUTHOR]

Purpose: The role of initial aqueous humic acid concentrations (dose), as well as secondary environmental conditions on the sorption of PCB congeners PCB 28, 52, 77, 101, 105, 138, 153, and 180 onto soil particle grain sizes, was investigated in this study.Materials and methods: Scanning electron microscopy equipped with energy dispersive X-ray and Fourier transform infrared spectroscopy were used for the internal morphology and qualitative elemental analysis, as well as identification of possible functional groups found in commercial HA. Batch adsorption experiments were used for sorption studies.Results and discussion: The results showed that the sorption of PCBs onto soil decreased with an increase in the aqueous HA concentrations. The adsorption of the selected PCBs onto the soils was found to decrease with an increase in the solution pH of humic acid. Thermodynamic studies showed that the partition coefficient values increased with an increase in solution temperature. All the standard free energy were negative indicating the spontaneity and feasibility of the sorption process with positive and high enthalpy and entropy values of the system. The sorption was best fitted with the Freundlich isotherm with the intensity parameter 1/n found to be greater than 1.Conclusions: The outcome of this study revealed that secondary pollution of river water may possibly be altered depending on variations in the environmental conditions such as pH and temperature. The presence of organic pollutants in alkaline soils having less organic matter content could increase the chances of leaching of organic pollutants causing groundwater contamination. [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]

This research work described the synthesis and metal ion binding properties of bis(2,2 - methylylidenephenol)diaminoethane a biologically, chemically and industrially important compound to make it more suitable and efficient for industrial scale production. To optimize the relationship between reactions conditions and yield of Co(II)-H2BMPDE, a second order quadratic polynomial equation was generated. The economical operating optimal reaction parameters were 0.30% bis(2,2 - methylylidenephenol)diaminoethane (H2BMPDE), 6.22 g CoCl2.9H2O, temperature of 39.27 °C, extraction time of 14.83 min and HCl concentration of 10-4 M. Based on the optimized reaction parameters, the laboratory yield was 31.70 g, which was in close agreement with the predicted yield of 31.89 μg. Thermodynamic studies indicated that the complexation is feasible, spontaneous, endothermic and involved solvation process. The high regression coefficient observed from the pseudo-second order kinetic model (R² =0.9948) as against pseudo-first order kinetic model (R²=0.3382) indicated that pseudo-second order kinetic model was obeyed and clearly described the complexation process. The complexation of cobalt(II) ions on the H2BMPDE correlated well with both Langmuir (R2 =0.8822) and Freundlich (R² = 0.9979) isotherms. The response surfaces and scale-up experiments indicated that the optimized process conditions could improve the yield of the complex at larger scales. [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]

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 (ΔG°) and the enthalpy of formation (ΔH°) as well as the entropy (ΔS°) 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.

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]