Adsorption Thermodynamic Parameters Research Articles

Correlating solvation-adsorption phenomena of some styrylpyridinium dyes on SDS modified silica surface in organic media

Sodium dodecyl sulfate modified silica (SDSMS) surface has been used to study the adsorption of some cationic styrylpyridinium dyes from organic solvent media using ultraviolet-visible (UV-Vis) spectrophotometric technique. The modifications of silica surface and subsequent modification through adsorption of dye molecules on the surface have been characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), UV-Vis spectroscopy and zeta potential measurements. Kinetics of adsorption and consequent thermodynamic parameters have been studied and discussed. The isotherm modeling, choice of solvents from sedimentation analysis, and other common adsorption related parameters such as amount of adsorbent dosage, contact time, adsorption efficiencies have been reported. The influences of solvents and the substituents present on the dye molecules, on the rate of adsorption have been discussed. A pictorial model of adsorption process has been suggested based on the experimental results.

Hexamethylenetetramine functionalized graphene oxide-alginate beads nanocomposite as efficient sorbent for dye from aqueous solution

In this study, a novel eco-friendly sorbent, hexamethylenetetramine (HMTA) functionalized calcium alginate (AG) immobilized graphene oxide (GO) composite (AG-GO-HMTA) and hexamethylenetetramine functionalized calcium alginate composite (AG-HMTA) were prepared. Adsorption factors including pH impact, contact time, initial dye concentration, dosage, selectivity and reusability on methylene blue (MB) removal from water were investigated. The prepared sorbents were characterized using structural (e.g. XRD, FT-IR, EDAX), thermal (e.g. TGA, DTG), and morphological (e.g. SEM, BET) analysis techniques. The equilibrium adsorption data was described by the Langmuir and Freundlich isotherms, and the adsorption kinetic and thermodynamic parameters were investigated. The field studies and regeneration of the beads were investigated. AG-GO HMTA displays a well-defined porous structure and this desired morphology arising from high quality dispersion of HMTA within the AG-GO matrix. The highest adsorption capacities were observed at pH ∼ 5, meanwhile the adsorption of MB dye molecules, positively charged, onto the beads became faster due to strong electrostatic interactions. When the value of dosage is 0.01 g, the equilibrium concentration (mg/g) are maximum at 103, 110, 164, 168 mg/g for AG, AG-GO, AG-HMTA and AG-GO-HMTA, respectively. The present work shows that pseudo first order could describe the MB adsorption onto AG while it couldn't describe the MB adsorption onto the functionalized sorbents due to the hybrid materials complicity.

Magnetic Fe3O4 embedded chitosan–crosslinked-polyacrylamide composites with enhanced removal of food dye: Characterization, adsorption and mechanism

The water solubility in acid solution, relative low adsorption capacities and unsatisfactory separation performance limit application of traditional chitosan-based adsorbents in wastewater treatment. To break the limitation, a hydrophilic magnetic Fe3O4 embedded chitosan–crosslinked-polyacrylamide composites (abbreviated as m–CS–c–PAM) were prepared by a two–step method. The m–CS–c–PAM composites were systematically characterized using SEM, XRD, FTIR, VSM, TGA and BET. Sunset yellow (SY) was selected as model food dye to investigate adsorption kinetics and thermodynamic parameters of food dye adsorption onto m–CS–c–PAM. Compared with magnetic Fe3O4/chitosan, m–CS–c–PAM can adapt to a wider range of pH (2–10) and resist the presence of inorganic salts. m–CS–c–PAM was proved to have high adsorption capacity (359.71 mg g−1) for SY dye at 298 K, much higher than magnetic Fe3O4/chitosan and many reported adsorbents. Moreover, m–CS–c–PAM could be rapidly and efficiently separated from treated solution within 15 s by an external magnet and regenerated by NaOH solution. With its excellent adsorption capacity, pH–independent adsorption capability for food dye, easy and convenient separation ability, satisfactory reusability, m–CS–c–PAM can be a promising material for food wastewater treatment.

Synthesis and characterization of montmorillonite – Mixed metal oxide composite and its adsorption performance for anionic and cationic dyes removal

Composite material based on montmorillonite – mixed metal oxides (MMT_MMO) derived from ZnAl layered double hydroxides was successfully synthesized by facile co-precipitation method under the presence of montmorillonite suspension followed by calcination at 400 °C. The as-synthesized material was characterized by several characterization techniques, including XRD, FTIR, SEM, TEM, TGA, and BET, then tested as an adsorbent for removal of both methylene blue (MB) as a cationic dye and congo red (CR) as the anionic dye from aqueous solution under different contact time, dye concentration, temperature, and pH. The as-synthesized MMT_MMO exhibited the hybrid characteristic of MMT and nano-sized mixed metal oxides. Nano-sized mixed metal oxides were successfully distributed on the surface of MMT, which brings advantages to improving the adsorption capacity of the material for anionic-based dye removal. Moreover, the average pore diameter of synthesized MMT_MMO composite was not significantly different (3.69 nm) compared to the original MMT (3.70 nm). The adsorption kinetics of MB and CR onto MMT_MMO was best fitted by the pseudo-second-order model, which indicated that the rate-limiting step was chemisorption. The equilibrium adsorption isotherm modeling to the experimental data revealed that the adsorption equilibrium data were best fitted by the Langmuir model, with maximum adsorption capacity reached 40 mg/g, which indicated that the sorption process occurred chemically in a monolayer of a homogenous surface. The calculation of the adsorption thermodynamic parameters exhibited that the adsorption process was conducted spontaneously under endothermic nature. This work provides a facile method for producing bifunctional material for the adsorption of both anionic and cationic dyes, which exhibited potential for total dyes removal from industrial wastewater.

On the applicability of triazine-based covalent organic polymer as adsorbent for dye removal from aqueous solution

Triazine-based covalent organic polymer, TCOP, is synthesized via the reaction between cyanuric chloride and piperazine in 1,4-dioxane, and is characterized with FT-IR, EDX, elemental mapping, XRD, SEM, TEM and N2 adsorption/desorption techniques. The capability of TCOP in the removal of different types of dye pollutants is studied and it was found that the removal efficiency is more than 70% for all of them. The kinetics and equilibrium adsorption of Rhodamine B (RhB) was studied at different conditions. Most of the adsorption takes place in less than 20 min and the maximum adsorption capacity is 153 mg/g. The adsorption isotherm can be well described by the modified Langmuir-Freundlich equation and the adsorption kinetics follows the fractal-like pseudo-first order kinetics model. Both of the fitted models reveal the heterogeneity of adsorbent. The adsorption thermodynamics parameters were calculated and interpreted. Finally, it was shown that the prepared TCOP can be used for the removal of dye mixture from aqueous solution.

Adsorptive denitrogenation of indole from model fuel oil over Co-MAC: Adsorption mechanisms and competitive adsorption

The present research article depicts the adsorptive denitrogenation of indole-containing model oil using cobalt-incorporated acid-activated carbon (Co-MAC). The active metal incorporated acetic acid-activated bio-sorbent showed a significant adsorption capacity for indole from model fuel oil than mere activated carbon. In a batch study, maximum 96% indole removal was achieved with an initial indole concentration of 500 mg/L, catalyst dose of 10 g/L, time of 4 h, and reaction temperature of 303 K. The non-linear regression analysis was opted to fit the experimental equilibrium data into various adsorption isotherms, including Langmuir, Freundlich, Temkin and Redlich, and Peterson. Thermodynamic parameters of adsorption were investigated, and the entropy and heat of adsorption change were determined to be 0.26 kJ/mol K and 57.31 kJ/mol, respectively. Besides, a plausible adsorption mechanism of indole was also explored.

Amino-terminated SiO2-Al2O3 composite aerogels from fly ash for improved removal of Cu2+ and Pb2+ ions in wastewater: one-pot synthesis, excellent adsorption capacity and mechanism.

In this study, by using a sol-gel grafting-atmospheric drying method, amino-terminated SiO2-Al2O3 composite aerogels, namely 3-aminopropyltriethoxysilane (APTES) or 3-(2-amino-ethoxy) propylmethyldimethoxysilane (AEAPMDS) modified SiO2-Al2O3 aerogels (AMSAAs), were synthesized from the fly ash and characterized by field-emission scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy etc.. And the AMSAAs were verified as excellent adsorbents for removing heavy metal ions (Cu2+ and Pb2+ ions) from wastewater. The effects of modification conditions and testing parameters including pH value, adsorbent dose, initial ions concentration, adsorption time and temperature were systematically investigated. Results demonstrated that 0.2mol/L APTES modified aerogels (0.2APTES-SAAs) possessed the best adsorption properties. Under the optimal pH value of 4.0-6.0 and the adsorbent dose of 0.4-0.6g/L, the equilibrium adsorption capacities of Cu2+ and Pb2+ ions were as high as 195mg/g and 500mg/g within 20-30min, respectively. The adsorption processes were agreed fairly well with Freundlich isotherm adsorption model and the pseudo-second-order kinetic model, which indicated that the adsorption processes were heterogeneous multilayer adsorption and controlled by the chemical reaction between AMSAAs and heavy metal ions. The obtained adsorption thermodynamic parameters (ΔH°, ΔS° and ΔG°) revealed that the adsorption processes were exothermic and spontaneous with decreased randomness at the solid-liquid interface. The excellent recyclability of as-prepared AMSAAs proved as economically promising adsorbents for practical applications.

Experimental and computational chemical studies on the corrosion inhibitive properties of metamizole sodium pharmaceutical drug compound for CS in hydrochloric acid solutions

The effect of sodium metamizole as a corrosion inhibitor for carbon steel (CS) in 1 M hydrochloric acid at various concentrations was studied by using chemical (weight loss, WL) and electrochemical [electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP)] methods. The results of WL showed that the effectiveness of sodium metamizole as a CS preservative in a hydrochloric acid solution at room temperature raised by improvement of the concentration of the inhibitor and reached 82.87% at 300 ppm and 25 °C. The effect of temperature on the CS was studied and the thermodynamic parameters of activation and adsorption were computed and discussed. The results showed that the inhibition efficiency (IE) decreases with increasing temperature, suggestive of physisorption. This was collaborated by values of activation energy, which are all below 80 kJ mol−1 and free energy which are below 20 kJ mol−1. The adsorption mechanism was coherent with Langmuir adsorption model. Results of the PDP revealed that the inhibitor was adsorbed on CS surface by mixed type of behavior. Furthermore, EIS revealed the dip in the values of double-layer capacitance and improvement in the charge transfer resistance with increased dose of sodium metamizole. Surface examinations were performed using altered techniques. The theoretical studies were calculated to confirm the validity of the practical results and the results of both were compared with each other, demonstrating the validity of the results obtained.

Pencil graphite supported nano zero-valent iron for removal of levofloxacin from aqueous solution: Effects of pH, kinetic and biological activity

A highly efficient, and potentially recyclable antibacterial composite was prepared in an efficient simple process. Antimicrobial levofloxacin (LEV) was used to functionalize the surface of nano zero-valent iron (Fe0) supported by pencil graphite (PG). The surface morphology, elemental composition, particle size, and removal efficiency of the PG-Fe0 composite were confirmed by UV, FTIR, EDX, SEM, TEM, and XRD techniques. The potential influence of pH, adsorbate concentration, contact time, and temperature on the removal efficiency of LEV by the magnetic composite (PG-Fe0) from an aqueous solution was investigated. The well-known established models were used to examine the adsorption isotherms, and the results showed that the kinetic adsorption data fit well with the pseudo-second-order model, with the highest removal efficiency achieved from pH 5–7 (85%). The maximum adsorption capacity qmax on the surface of Fe0-PG for LEV was obtained using the Langmuir isotherm at pH 6.5 (66.3 mg/g) and pH 8 (11.4 mg/g). All adsorption thermodynamic parameters at pH 6.5 suggested a chemisorption endothermic natural process ΔHo(44.4 kJ/mol), and the negative value of free Gibbs energy indicated a spontaneous process at an ambient temperature. Furthermore, the removal efficiency of the PG-Fe0 composite was better than that of the Fenton-like catalyst performance for both Fe0 and PG-Fe0. Reusability and antibacterial activity of adsorbed LEV on the surface of PG-Fe0 were investigated against various types of gram-positive bacteria; (E. faecalis, S. epidermidis, and S. aureus) and gram-negative; (E. coli, K. pneumonia, and P. Mirabilia) via agar well diffusion method. Finally, the magnetic feature of the PG-Fe0-LEV composite has numerous potential for recovery and reuse.

Theoretical SERS study of the strength and suitability of Cu12 nanostar for SERS: Complete theoretical studies, coinage metal SM12 comparisons, benzothiazole (BTH) adsorbent

Theoretical calculations were used to optimize molecular structures which help determine binding energies, and elucidate electronic properties of unsubstituted benzothiazole (BTH) adsorption on metal star models, SM12 (M = Ag/Au/Cu). BTH tends to connect via its donor nitrogen and sulfur heteroatoms as well as the π-conjugated carbon atoms; adsorption is onto the bare metal atoms of the nanostar, a single 12-membered ring, involving increasingly stable adsorption energies of −3.25/-5.71/-17.57 kcal mol−1 for BTH-Ag12/Au12/Cu12 complexes as one ascends the Group 11 triad. From the electrophilicity values, it is clear that the outermost electrons of the system will be able to travel (injected) from the chemically adsorbed BTH unit into the adsorbent SM12 within the structure of the complex. The values for changes in enthalpy and entropy for all complexes studied herein show that the motion of the atoms is constrained due to the presence of the BTH; the adsorption of BTH onto the investigated SM12 adsorbents is spontaneous. The increase of dipole moments for the complexes in aqueous media support potential for molecular recognition; drug delivery-oriented applications of the complexes are predicted to undergo dissolution in polar media such as water, offering the possibility for drug molecule recognition applications. Raman inactive modes of BTH become active within the BTH-metal complexes and experience enhancement in intensity. Adsorption behavior and thermodynamics parameters also indicate that the Cu12 cluster has the strongest interaction with maximum adsorption energy of −17.6 kcal mol−1. Density of states spectral analysis supports the charge transfer, adsorption behavior, and other thermodynamic parameters. In conclusion, density functional theory (DFT) has helped to determine electronic characteristics of SM12 clusters which have been demonstrated to be highly sensitive to the presence of BTH; these findings can allow for the molecular pairs to be used in (bio) sensor devices and to potentially trace the drug in the human body via spectrophotometry.

Effect of Schiff's bases on corrosion protection of mild steel in hydrochloric acid medium: Electrochemical, quantum chemical and surface characterization studies

Schiff's bases such as (E)-3-(3-hydroxybenzylideneamino)-2-(3-hydroxyphenyl)-2,3-dihydroquinazolin-4(1H)-one (SB-1) and (E)-3-(5‑bromo-2-hydroxybenzylideneamino)-2-(5‑bromo-2-hydroxyphenyl)-2,3-dihydraquinazolin-4(1H)-one (SB-2) were synthesized and investigated to the surface interactions & corrosion protection performance on mild steel (MS) in 2 M HCl medium by means of weight loss, electrochemical polarization and electrochemical impedance spectroscopic (EIS) techniques. Tafel polarization measurements showed that, the synthesized compounds were exhibited as mixed type (cathodic / anodic) inhibitors and the maximum protection efficiencies of 86.44% and 87.36% for SB-1 and SB-2 respectively were observed at optimized concentration. The corrosion control of MS in presence of inhibitors could evaluate through adsorption phenomenon and fitted to Langmuir's adsorption isotherm. Activation energy (Ea) values in absence of the inhibitor is minimum 51.45 kJ mol−1 and higher values of 89.98 kJ mol−1 and 70.09 kJ mol−1 in the presence of SB-1 and SB-2 respectively. Thermodynamic adsorption parameters such as ∆Hads, ∆Gads & ∆Sads were correlated to the corrosion inhibition process. Quantum chemical analysis revealed the nature of chemical interaction established between the inhibitor molecules and metal atoms. The change in surface morphology of mild steel and chemical interactions of inhibitor molecules on specimen surface were evaluated through FT-IR, Scanning electron microscopic linked with EDX, Atomic force spectroscopy and Contact angle techniques. Atomic force microscopic results revealed that, an average roughness of the mild steel surface has been reduced from 443 nm to 11.0 nm and 26.9 nm in presence SB-1 and SB-2 respectively.

Copper corrosion inhibition in nitric acid solution by 2-(1,3-dihydrobenzimidazol-2-ylidene) -3-oxo-3-(pyridin-3-yl) propanenitrile: Gravimetric, Quantum chemical and QSPR studies

The metal corrosion threat in the metallurgical industry is becoming increasingly important. So in this work, the inhibition properties of 2-(1,3-dihydrobenzimidazol-2-ylidene)-3-oxo-3-(pyridin-3-yl) propanenitrile for copper corrosion in 1 M nitric acid medium were evaluated by mass loss technique, density functional theory (DFT) and quantitative structure-property relationship (QSPR) model. The results show that this compound was excellent anticorrosive properties with a maximum inhibition efficiency of 89.39 % for a concentration of 0.2 mM at 323 K. The inhibition efficiency increases with increasing temperature and inhibitor concentration. Adsorption isotherms reported that the molecule adsorbs on copper surface according to Langmuir isotherm. Thermodynamic adsorption and activation parameters were determined and analyzed. They revealed spontaneous adsorption and a strong interaction between the molecule and copper surface. DFT calculations at the B3LYP level with 6-31G(d,p) and 6-311G(d,p) basis set permitted to explain the electronic exchanges between molecule and copper, thus justifying the experimentally obtained inhibition efficiency values. A local reactivity study of molecules indicated that N (29) and C (7) atoms are the likely sites for nucleophilic and electrophilic attacks, respectively. In addition, QSPR model was used to correlate experimental inhibition efficiency with the descriptor parameters of the studied molecule, and it is found that the calculated inhibition efficiencies are close to experimental inhibition efficiencies. Finally, this study showed a good correlation between theoretical and experimental data.

Alkaloids extract of Alnus nepalensis bark as a green inhibitor for mild steel corrosion in 1 M H2SO4 solution

Extraction of alkaloids from Alnus nepalensis bark has been successfully carried out and used as a green inhibitor for mild steel corrosion exposed to 1 M H2SO4 solution. Alkaloids have been tested by chemical, UV and FTIR spectroscopic methods.Corrosion inhibition was monitored by weight loss measurement and electrochemical methods(open circuit potential method and potentiodynamic polarization method). Weight loss measurement was employed to study the inhibitor concentration and immersion time effect. Similarly, the temperature effect on inhibition efficiency was also carried out by this method. The maximum corrosion inhibition efficiency observed for 1000 ppm solution for 3 h was 71.94 % at 25 °C. The OCP measurement revealed that alkaloids acted as a mixed type of inhibitor. Potentiodynamic polarization for 3 h immersed samples in the presence and absence of inhibitors was carried out. The corrosion current density was decreased with the increasing concentration. The maximum efficiency of immersed sample in 1000 ppm inhibitor solution was 78.48 %. The adsorption isotherm and thermodynamic parameters were calculated and the energy of activation (Ea) was found to be 71.41 kJ/mol. The positive value of enthalpy indicated that the reaction involves is endothermic.

A detailed surface characterization study of SBA-15 and B-SBA-15-x mesoporous materials using the IGC technique

Pure and boron-containing B-SBA-15-x (molar ratio, Si/B = 50, 30, 10) mesoporous materials were synthesized by a direct hydrothermal procedure. Samples were characterized by XRD, ICP-OES, FT-IR, BET and SEM. Inverse gas chromatography (IGC) technique was used to determine the dispersive surface energies (γSd), adsorption thermodynamic parameters (ΔH, ΔG, ΔS) and the acid-base constants (KA and KD) of the samples. IGC experiments were performed at infinite dilution region at 200, 210, 220 and 230 °C. The surface characterization results confirmed that the SBA-15 structure was formed, boron was added to the structure and all samples have meso pores. The surface area of the pure SBA-15 was determined as 745.288 m2/g and it was found that the surface area decreases with increasing boron content. Physical adsorption occurred between the IGC probe molecules and all SBA-15 materials according to the adsorption thermodynamic parameters. (γSd) values of pure SBA-15, B-SBA-15-50, B-SBA-15-30 and B-SBA-15-10 were found at 40.873, 37.039, 36.636 and 37.444 mJ/m2 at 200 °C, respectively. It has been observed that the dispersive surface energy of all samples decreases with increasing temperature. According to the SC value calculated from the KA and KD parameters, the surface of B-SBA-15-10 with the highest boron content was found to be acidic. On the other hand the surfaces of all other samples were determined as basic.

Eco-Friendly Synthesis and Characterization of Double-Crossed Link 3D Graphene Oxide Functionalized With Chitosan for Adsorption of Sulfamethazine From Aqueous Solution: Experimental and DFT Calculations

Graphene oxide–chitosan composites are attracting considerable interest as an eco-friendly adsorbent material for most aquatic environmental pollutants. Today, the focus is on the emerging applications of 2D and 3D graphene functionalized with chitosan to enhance its mechanical properties and adsorption efficiency. Herein, the super adsorbent 3D graphene functionalized with chitosan (3D GF-CS) is synthesized to remove sulfamethazine, (SMZ) as a model aquatic antibiotic pharmaceutical. The synthesized materials were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photon spectroscopy (XPS), Brunauer–Emmett–Teller (BET), and Raman spectroscopy. After that, adsorption experiments were conducted for SMZ adsorption to find out the optimized adsorption parameters, such as pH, temperature, contact time, initial antibiotic concentration, and adsorbent dosage. The results show the optimal adsorption parameters were as pH of 7, temperature of 25°C, initial antibiotic concentration Ci of 50 ppm. Also, the kinetics, isotherms models, and thermodynamics parameters of SMZ adsorption were studied. The experimental results revealed to be best suited by both the pseudo-second-order kinetic and the Freundlich isotherm model compared with other isotherm models. The thermodynamics parameters demonstrated that the adsorption is exothermic, exhibiting higher adsorption efficiency at lower temperature. In addition, Gibb’s free energy suggested the adsorption to be spontaneous as well as entropy indication of the loss of disorder. Furthermore, the regeneration of 3D GF-CS was utilized in ten consecutive cycles, and the SMZ adsorption capacity did not decline significantly. Additionally, this research studied the adsorption energies and how sulfamethazine adsorbs onto 3D GF-CS was determined by applying the density-functional–based tight binding (DFTB) and Monte Carlo simulations at different adsorption positions. The chemical reactivity (local and global) of the free drug was investigated using the density functional theory (DFT), namely, the B3LYP and PBEPBE functionals with the 6–31+G (d, p) basis set in the gas phase and aqueous solution.

Removal of Cr (III) from wastewater by using raw and chemically modified sawdust and corn husk

Abstract The contamination of water resources by heavy metals (HMs), mainly introduced by anthropogenic resources, has been considered as a serious environmental issue in the recent era. Therefore, the conventional methods for heavy metal removal have various drawbacks in terms of cost, toxicity, and efficiency. The novel study investigated the biosorption intensity of raw and chemically modified sawdust (SD) and corn husk (CH) to eliminate chromium (III) from the aqueous solutions. SD and CH were used as biosorbents and were treated chemically with sulfuric acid (H2SO4), sodium hydroxide (NaOH), and detergent powder. The biosorption potential was estimated based on percentage removal efficiency (% RE) of chromium (III) and the adsorption intensity (qmax). The characterization of surface morphology and functional groups of biosorbents was studied by SEM and FTIR. Moreover, the adsorption isotherm models (Langmuir and Freundlich), kinetic models (pseudo-first-order kinetics and pseudo-second-order kinetics), and thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were also assessed to predict the biosorption process. The results of % RE revealed that detergent-treated SD (DTSD) and detergent-treated CH (DTCH) showed highest % RE of 9.27 ± 0.15 (%) and 99.16 ± 0.08 (%) for elimination of chromium (III), respectively. Similarly, base-treated SD (BTSD) and base-treated CH (BTCH) exhibited 95.53 ± 0.18 (%) and 92.43 ± 0.22 (%) of % RE compared with 77.87 ± 1.64 (%) and 81.96 ± 0.34 (%) removal efficiency of acid-treated SD (ATSD) and acid-treated CH (ATCH), respectively. The raw SD (RSD) and raw CH (RCH) showed lower % RE of 23.68 ± 1.52 (%) and 35.52 ± 4.74 (%) for Cr (III) removal. Further, the porosity on the biosorbent's surface and attached functional groups increased after chemical treatment and this variation resulted in increased removal efficiency after chemical treatments. The Langmuir isotherm model and the Freundlich isotherm model were employed to predict the biosorption process, and both these models are best-fitted. The pseudo-second-order kinetic model was promising representative of the biosorption data. The process was endothermic and the parameters indicated that Cr (III) biosorbtion was thermodynamically favorable. Therefore, the obtained results highlighted that detergent-treatment enhanced the % RE, and DTSD and DTCH are highly efficient biosorbents for eliminating Cr (III) from aqueous solutions. Thus, detergent-treated biosorbents are proved to be a promising sustainable, eco-friendly, and cost-effective way to treat HMs from aqueous solutions as they utilize natural agriculture waste products and also handle issues related to excessive solid waste management.

Influence of calcination atmosphere on Fe doped activated carbon for the application of lead removal from water

In the current work, granular activated carbon (GAC) materials doped with 5 and 10 wt% of Fe were prepared via incipient wetness impregnation method utilizing two different solvents (water and ethanol) and calcined in N2 and static air atmosphere. The prepared materials were thoroughly characterized by FE-SEM, EDS, XRD, FT-IR, XPS and BET surface area techniques. The Fe doped materials were examined for adsorptive removal of lead (Pb2+) ions from aqueous solution. According to the adsorption screening experiments, the 5 wt% Fe doped GAC impregnated in ethanol and calcined under nitrogen demonstrated the highest removal of Pb2+ ions (86.6%). The adsorption results were found consistent with the surface and porous properties of the doped GAC. The 5 wt% Fe-GAC/ethanol/nitrogen illustrated the maximum surface area (715 m2/g), the largest pore diameter and volume, and the lowest size of Fe nanoparticles. The adsorption kinetics, isotherm and thermodynamics were evaluated for the remediation of Pb2+ ions by the optimized adsorbent. The kinetic analysis outcomes found well matched with the pseudo-second order model while the isotherm results modelling were well correlated with Redlich-Peterson, Sips and Langmuir models. The Langmuir highest adsorption capacity of Pb2+ ions was 124.3 mg/g at pH 4.7 and room temperature. The process of Pb2+ ions removal by Fe modified GAC was found as endothermic and spontaneous process as confirmed by the analysis of thermodynamic adsorption parameters. It was anticipated that both chemical and physical mechanisms were participated in the adsorption process including electrostatic interactions, complexation, ion exchange and surface adsorption.

Experimental and theoretical study of Sodium Cocoyl Glycinate as corrosion inhibitor for mild steel in hydrochloric acid medium

Corrosion of metals is a big economic concern all over the globe. Corrosion inhibitors, particularly those based on surfactants, are one of the utmost efficient methods of defense of metal surfaces against corrosion. This research looks at the application of the amino acid-based surfactant Sodium Cocoyl Glycinate (SCG) as a corrosion inhibitor. The inhibitor's ability to protect a mild steel (MS) sample in 1 M HCl was investigated, and it was shown to be quite effective. The inhibitory behaviour of SCG on MS corrosion was investigated employing procedures such as weight loss (WL), Electrochemical Impedance Spectroscopy (EIS), potentiodynamic polarization (PDP), Scanning Electron Microscopy (SEM), Atomic force microscopy (AFM) and so on. Based on the temperature and concentration of inhibitor, the compound resisted MS corrosion to varying degrees. At 30 °C, SCG showed a 95.21 % inhibition efficiency (IE%) at 0.2864 mM which reduced to 73.21 % at 60 °C. Thermodynamic and kinetic parameters of MS corrosion and inhibitor adsorption were evaluated and addressed. The Gibbs free energy of adsorption (ΔGads0) was calculated to be in between −30 and −40 KJ mol−1, depicting mixed adsorption (i.e., both chemisorption and physisorption). Quantum chemical parameters were employed to investigate surfactant reactivity and adsorption behaviour. The outcomes of the experimental investigation and the theoretical study were well-aligned.

Green synthesis of mesoporous Ni-Co layered double hydroxide and its application for removal of 2,4-dinitrophenol from water: A theoretical study complemented by the first principle density functional theory-Monte-Carlo approach

This paper describes the synthesis of a novel mesoporous Ni-Co layered double hydroxide(LDH) and its application for the adsorptive removal of 2,4-dinitrophenol(2,4-DNP) from an aqueous solution. A green synthetic method was used involving a non-aqueous ‘soft chemical' ethanol: acetone mixture in order to avoid intercalation or interlayer contamination by CO2 gas, which is responsible for carbonate formation. The synthesized material was characterized using PXRD, HR-TEM, FESEM, XPS, FT-IR, TGA-DTA, etc. The experimental and model fitting results of adsorption studies showed that equilibrium Freundlich adsorption isotherm and kinetic pseudo-second-order were the best-fitting models. Also, thermodynamic adsorption parameters ∆Ho,∆Soand∆Go were found to be favorable, non-spontaneous, and endothermic. Furthermore, theoretical molecular dynamic simulation (MD) revealed that the nature of adsorbate-substrate (2,4-DNP- Ni-Co LDH) interactions were favorable hydrophobic interactions. DFT-based DMoL3 approach showed that the adsorbate-substrate energy gap (eV) increases with the increase in the interfacial region, explaining the high chemical stability after the adhesion of adsorbate molecules. The regeneration adsorption cycles showed that the Ni-Co LDH acts with an excellent removal affinity towards the 2,4-DNP molecule within 150–180 min from cycles 1–4.

Synthesis Characterization and Highly Protective Efficiency of Tetraglycidyloxy Pentanal Epoxy Prepolymer as a Potential Corrosion Inhibitor for Mild Steel in 1 M HCl Medium.

Anticorrosive protection efficiency of novel tetrafunctional epoxy prepolymer, namely 2,3,4,5-tetraglycidyloxy pentanal (TGP), for mild steel in 1 M HCl medium was assessed through potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), contact angle (CA), adsorption isotherm model, temperature effect and thermodynamic parameters. The synthesized TGP was characterized and confirmed by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR). The inhibitory efficiencies found at lower concentration of the prepolymer TGP were85% (PDP) and 87.17% (EIS). PDP measurement illustrated that the TGP behaved as a mixed-type inhibitor in the realized solution. SEM and EDS analysis showeda significant decrease in the corrosion of the MS surface in the presence of the inhibitory prepolymer compared with the blank (1 M HCl). Langmuir adsorption isotherm is the most acceptable modelto describe the TGP epoxy prepolymer on the MS area.