Adsorption Thermodynamic Parameters Research Articles

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.

The adsorption mechanisms of oriental plane tree biochar toward bisphenol S: A combined thermodynamic evidence, spectroscopic analysis and theoretical calculations

Garden pruning waste is becoming a problem that intensifies the garbage siege. It is of great significance to purify polluted water using biochar prepared from garden pruning waste. Herein, the interaction mechanism between BPS and oriental plane tree biochar (TBC) with different surface functional groups was investigated by adsorption experiments, spectroscopic analysis and theoretical calculations. Adsorption kinetics and isotherm of BPS on TBC can be satisfactorily fitted into pseudo-second-order kinetic and Langmuir models, respectively. A rapid adsorption kinetic toward BPS was achieved by TBC in 15 min. As compared with TBC prepared at low temperature (300 °C) (LTBC), the maximum adsorption capacity of TBC prepared at high temperature (600 °C) (HTBC) can be significantly improved from 46.7 mg g−1 to 72.9 mg g−1. Besides, the microstructure and surface functional groups of HTBC were characterized using SEM, BET-N2, and XPS analysis. According to density functional theory (DFT) theoretical calculations, the higher adsorption energy of HTBC for BPS was mainly attributed to π-π interaction rather than hydrogen bonding, which was further supported by the analysis of FTIR and Raman spectra as well as the adsorption thermodynamic parameters. These findings suggested that by improving π-π interaction through high pyrolysis temperature, BPS could be removed and adsorbed by biochar with high efficacy, cost-efficiency, easy availability, and carbon-negative in nature, contributing to global carbon neutrality.

Fabrication of the composite sepiolite@polyethyleneimine/sodium alginate and its excellent adsorption performance for heavy metal ions

In order to explore more excellent heavy metal adsorbents with clay mineral sepiolite (Sep), this work was carried out and presented the novel design and fabrication processes of the composite Sep@polyethyleneimine/sodium (SEP@PEI/SA), which were characterized by SEM, EDX, FT-IR, XPS, TGA, and porous analysis, and were efficiently utilized for heavy metal ions adsorption. The adsorption properties of SEP@PEI/SA for Pb(II), Cu(II), Au(III), Ag(I), Pd(IV), Pt(IV), Hg(II), Cr(VI), Cr(III), Co(II), Zn(II), and Ni(II) were investigated, and it was employed to remove lead ions from the simulated lead-containing industrial wastewater through adsorption method. The adsorption properties of lead ions on SEP@PEI/SA were thoroughly investigated in this study, and the results demonstrated that the adsorption kinetics of SEP@PEI/SA for lead ions at different temperatures could be modeled closely by a pseudo second-order rate equation, Langmuir isotherm model was the best fit one and the maximum adsorption capacity was could reach 1094.86 mg/g at 25 °C. Adsorption thermodynamic parameters, standard Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) changes, were −6.29 KJ·mol−1 (35 °C), 30.81 KJ·mol−1, 0.12 KJ·(K·mol)−1, respectively, suggesting the spontaneous and endothermic nature of the adsorption process with the increase of the randomness. All these research work results showed that the novel adsorbent SEP@PEI/SA has promising potential to removal lead ions from water body efficiently.

Influence of Organic-Inorganic Composition on the Adsorption of Niutitang Formation Shale in Huijunba Syncline

To study the influence of different organic-inorganic composition on the adsorption in shale, taking the Niutitang Formation shale in the Huijunba syncline in southern Hanzhong as the research object, based on acid treatment to extract kerogen and wet chemicals. Extracting mineral components by oxidation method, a series of isothermal adsorption experiments were carried out on the original rock, kerogen, and mineral components of the samples. Through the three-dimensional Langmuir model fitting and adsorption thermodynamic calculation method, the adsorption thermodynamic parameters such as the isometric heat of adsorption and the standard adsorption entropy are obtained. The research results show that organic matter is the primary factor affecting the methane adsorption of shale and clay minerals also affect the adsorption to a certain extent. When the burial depth is relatively shallow, diagenesis has a promoting effect on the total amount of adsorption. As the depth increases, the diagenesis will turn into an inhibitory effect on the total amount of adsorption. Through the component weighting method, the lower limit ratio of the adsorbed amount of organic matter to the total amount in the shale is 29.3%~46.7% when the depth reaches to 3000 m, while the upper limit ratio of the adsorption of mineral components is 66.4%~73.6%.

Effect of 2-ethylbutyric acid on thermodynamics stability of various nonionic surfactants tanshione-loaded micelles

At present, the stability of drug-loaded micelles is scarcely researched. The effects of different amounts of 2-ethylbutyric acid (EBA) on the interface and micelle behavior of Polyoxyl 15 Hydroxystearate (HS15), Kolliphor RH40, Kolliphor ELP and Tween80 (Polysorbate 80) micelles have been studied in this work. Tanshinone (TAN), a fat-soluble extract of Salvia miltiorrhiza was used as a model drug. The surface properties of drug-loaded micelles have been studied, including critical micelle concentration, minimum adsorption area, pC20 and thermodynamic parameters. The results indicated that the addition of the appropriate amount of EBA contributed to the formation of drug-loaded micelles and improved their physical stability. In addition, the same conclusion can be drawn from determining the absorbance of drug-loaded micelles stored by UV–visible spectrophotometry at different times. The hydrodynamic diameter (dη) of drug-loaded micelles was measured by dynamic light scattering (DLS). The dη values of TAN -loaded micelles with and without EBA were different, indicating that the internal structure of the micellar hydrophobic core had varied. In a word, appropriate amount of EBA added can improve the stability of TAN -loaded micelles, which provides a reference for studying the stability of drug-loaded micelles with nonionic surfactants.

Environmentally azithromycin pharmaceutical wastewater management and synergetic biocompatible approaches of loaded azithromycin@hematite nanoparticles

Pharmaceutical wastewater contamination via azithromycin antibiotic and the continuous emergence of some strains of bacteria, cancer, and the Covid-19 virus. Azithromycin wastewater treatment using the biosynthesized Hematite nanoparticles (α-HNPs) and the biocompatible activities of the resulted nanosystem were reported. Biofabrication of α-HNPs using Echinaceapurpurea liquid extract as a previously reported approach was implemented. An evaluation of the adsorption technique via the biofabricated α-HNPs for the removal of the Azr drug contaminant from the pharmaceutical wastewater was conducted. Adsorption isotherm, kinetics, and thermodynamic parameters of the Azr on the α-HNPs surface have been investigated as a batch mode of equilibrium experiments. Antibacterial, anticancer, and antiviral activities were conducted as Azr@α-HNPs. The optimum conditions for the adsorption study were conducted as solution pH = 10, 150 mg dose of α-HNPs, and Azr concentration 400 mg/L at 293 K. The most fitted isothermal model was described according to the Langmuir model at adsorption capacity 114.05 mg/g in a pseudo-second-order kinetic mechanistic at R2 0.9999. Thermodynamic study manifested that the adsorption behavior is a spontaneous endothermic chemisorption process. Subsequently, studying the biocompatible applications of the Azr@α-HNPs. Azr@α-HNPs antibacterial activity revealed a synergistic effect in the case of Gram-positive more than Gram-negative bacteria. IC50 of Azr@α-HNPs cytotoxicity against MCF7, HepG2, and HCT116 cell lines was investigated and it was found to be 78.1, 81.7, and 93.4 µg/mL respectively. As the first investigation of the antiviral use of Azr@α-HNPs against SARS-CoV-2, it was achieved a safety therapeutic index equal to 25.4 revealing a promising antiviral activity. An admirable impact of the use of the biosynthesized α-HNPs and its removal nanosystem product Azr@α-HNPs was manifested and it may be used soon as a platform of the drug delivery nanosystem for the biomedical applications.

Low-cost Posidonia oceanica bio-adsorbent for efficient removal of antibiotic oxytetracycline from water.

The presence of antibiotics as micro-contaminants in the water and aqueous environments is a health concern to humans and the ecosystem. Therefore, their elimination by adsorption to available and cheap materials in water treatment plants is a research topic of high relevance. The present paper reports on the adsorption behavior of oxytetracycline on a bio-adsorbent prepared from Posidonia oceanica; an abundant Mediterranean biomass. Characterization of the pretreated Posidonia biomaterial was achieved using several analyses such as Boehm acid-base titration method, pHPZC determination, and analysis techniques (FTIR, 13C CP-MAS NMR, optical microscopy, and TGA). The pHPZC occurred around pH 2.11. Posidonia biomaterial showed a fast and high uptake rate throughout the adsorption process, which is a definite advantage for analytical applications such as water decontamination. The experimental kinetic data fitted very rightly the pseudo-second-order kinetic model and the equilibrium uptake can adopt the bi-Langmuir isotherm model for all studied pH values which assumes adsorptions at the two localized sites. Maximum adsorption capacities of 11.8mg∙g-1 and 4.4mg∙g-1 for the two adsorption sites are reached at pH 6. The oxytetracycline adsorption process onto Posidonia bio-adsorbent is spontaneous (ΔadsG0 < 0), exothermic (ΔadsH0 < 0), and entropically favorable (ΔadsS0 > 0). The effect of pH on adsorption behavior and the thermodynamic parameters of adsorption are consistent with a possible origin of adsorption of oxytetracycline by means of hydrogen bonding interactions between surface hydroxyl and phenolic groups of the biomaterial and oxytetracycline. The proposed green and environmentally friendly biomaterial offers potential benefits as a bio-adsorbent in the remediation of aquatic environments contaminated by various organic materials.

Защита металлов ингибиторами коррозии в растворах различных кислот

The current state of research in the field of inhibitor protection of metals and alloys in solutions of mineral and organic acids has been summarized and analysed. Acid solutions in modern industry are widely used at oil-and-gas facilities, metallurgy, housing-and-communal services, where they can be in contact with metal parts of industrial equipment for a long time, without the use of additional protection measures, causing its destruction. The specificity of the corrosive effect of acid solutions on metallic materials is analysed. Various groups of metal corrosion inhibitors (CIs) for these media and the features of the mechanism of their protective action were discussed. Among the various groups of CIs that protect metals in acidic media, various azole derivatives deserve the most attention. The industrial use of azoles is promising in the form of mixtures with other compounds. Promising lines of research in the field of inhibitory protection of metals in acidic media are associated with the wider application of the possibilities of electrochemical methods (voltammetry and electrochemical impedance spectroscopy). When determining the thermodynamic parameters of CIs adsorption, one should be guided by determining their true values, and not effective values. In the development of mixed CIs, a thorough theoretical study of these issues is required, taking into account prospects of such developments for the industrial use. Prospects for the industrial application of environmentally friendly («green») CIs for the protection of metals in acidic environments are considered. At present, the practical application of such products is limited by the lack of data on their compliance with the tight requirements of modern industries for CIs. The bibliography includes 129 references.

Highly Efficient Adsorption of Heavy Metals and Cationic Dyes by Smart Functionalized Sodium Alginate Hydrogels.

In this paper, functionalized sodium alginate hydrogel (FSAH) was prepared to efficiently adsorb heavy metals and dyes. Hydrazide-functionalized sodium alginate (SA) prepared hydrazone groups to selectively capture heavy metals (Pb2+, Cd2+, and Cu2+), and another functional group (dopamine grafting), serves as sites for adsorption methylene blue (MB), malachite green (MG), crystal violet (CV). Thermodynamic parameters of adsorption indicated that the adsorption process is endothermic and spontaneous. The heavy metals adsorption by FSAH was physical adsorption mainly due to ΔHθ < 40 kJ/mol, and the adsorption of cationic dyes fitted with the Langmuir models, which indicated that the monolayer adsorption is dominated by hydrogen bonds, electrostatic interactions, and π-π interactions. Moreover, the adsorption efficiency maintained above 70% after five adsorption-desorption cycles. To sum up, FSAH has great application prospect.

Investigation of Thermodynamic, Kinetic, and Isothermal Parameters for the Selective Adsorption of Bisphenol A.

Herein, a novel imprinted solid-phase extraction cartridge was fabricated to investigate the kinetic, thermodynamic, and isothermal parameters for the selective adsorption of Bisphenol A (BPA). The imprinted polymeric cartridges (BMC) for the BPA adsorption were fabricated in the presence of a template and functional monomer using the in situ polymerization technique. To prove the efficiency and selectivity of BMC, the nonimprinted polymeric cartridges (BNC) and the empty polymeric cartridges (EC) were also fabricated with and without functional monomer using the same manner for the preparation of BMC. The characterization of cartridges was performed by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area measurements, and swelling tests. BPA removal studies were performed by analyzing some parameters such as temperature, BPA concentration, flow rate, salt type, and concentration. The highest capacity was determined as 103.2 mg BPA/g polymer for a 0.75 mL/min flow rate of 0.75 M (NH4)2SO4 containing 200 mg/L BPA solution at 50 °C. NaOH (1.0 M) was used as a desorption agent. The reusability performance was examined by performing 10 consecutive cycles. The solid-phase extraction (SPE) performance was also checked to determine the enrichment and extraction recovery factors for tap water and synthetic wastewater samples. Temkin, Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models were applied to BPA adsorption data examining the adsorption mechanism, surface properties, and adsorption degree. The most suitable isotherm model for BPA adsorption was determined as the Langmuir isotherm model. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were investigated to reveal the thermodynamics of adsorption. Adsorption thermodynamic parameters (ΔH°, ΔS°, and ΔG°) were calculated using the thermodynamic equilibrium constant (thermodynamic equilibrium constant, K°) values that change with temperature. It was determined that BPA adsorption was spontaneous (ΔG° < 0) and endothermic (ΔH° > 0) and entropy increased (ΔS° > 0) at the temperatures studied in the BPA adsorption process. The rate control step in the adsorption process was examined by applying pseudo-first-order and pseudo-second-order kinetic models to the adsorption data for the investigations of BPA adsorption kinetics, and the pseudo-second-order kinetic model was found to be more suitable for describing BPA adsorption kinetics. In examining the selectivity of cartridges, structural analogues of hydroquinone, phenol, β-estradiol, and 8-hydroxyquinoline were tested.

Hydrothermal conversion of lignocellulosic waste to value-added biomaterial for high-performance contaminant removal: Focusing on synthesis route and uptake mechanism

In this paper, a novel carbonaceous material was successfully synthesized from lignocellulosic waste by a green conversion technology. Pomegranate (Punica granatum L.) pulp waste (PPW) was transformed to hydrochar (PPWHC) through hydrothermal carbonization (HTC) and the key affecting factors including the holding temperature (HT; 180–220 °C) and holding time (Ht; 6–24 h) were explored. The physico-chemical, structural, functional, morphological properties were discussed by 13C NMR, BET, XRD, XPS, SEM/EDX, FT-IR, Raman, and CHNS elemental analysis. Based on the carbon content, higher heating value and energy densification values, a HT of 220 °C and Ht of 12 h were determined as optimal operational conditions. Further, PPWHC was utilized for the removal of Rhodamine B (RhB) in batch mode. The maximum uptake was 121.95 mg/g at 323 K. Adsorption thermodynamics parameters were calculated. Additionally, reusability studies demonstrated that PPWHC exhibited a superior removal performance for RhB after five consecutive sorption/desorption cycles.

Design of molecularly imprinted polymer materials relying on hydrophobic interactions

The design of molecularly imprinted polymers (MIPs) for the specific binding of hydrophobic molecules (mitotane) was investigated by considering monomers and cross-linking agents with variable hydrophobic character, methyl methacrylate, butyl methacrylate and lauryl methacrylate as functional monomers, and ethylene glycol dimethacrylate and 1,6-hexanediol dimethacrylate as cross-linking agents. MIPs were bound to a porous silica support by means of a radical transfer reaction with grafted 3-mercaptopropyl groups. Equilibrium adsorption isotherms to molecularly imprinted and non-imprinted materials were modeled with the Volmer and Langmuir–Volmer isotherms, giving the thermodynamic parameters of adsorption. The most hydrophobic monomer provided the highest selective adsorption although strong non-selective adsorption and the intrinsic softness of poly(lauryl methacrylate) is detrimental to selectivity. Adsorption was exothermic with a predominant enthalpic contribution. Adsorption kinetics were fast due to the high accessibility of molecular imprints on the surface of the thin MIP layer coating the porous silica support.

Biodegradable cellulose nanocrystals hydrogels for removal of acid red 8 dye from aqueous solutions

Biodegradable cellulose nanocrystals hydrogels (CNCsH) were synthesized from cellulose nanocrystals (CNCs) which were prepared from office wastepaper (OWP) by a chemical crosslinking method using epicholorohydrin (ECH) as a cross-linker. CNCsH were tested for their swelling behavior and biodegradability and the point of zero charge had been determined. The ability of CNCsH for removing the Acid Red 8 (AR8) anionic dye from its aqueous solution was evaluated. The different parameters affecting removal of the dye, such as pH, initial concentration of dye, content of CNCs, temperature and adsorbent dosage were investigated. The optimum conditions for 68% removal efficiency were pH = 1, initial concentration of dye = 10 ppm, contact time = 105 min, CNCs content = 5% and CNCsH dosage = 0.5 g at 30 °C. The adsorption isotherms, kinetics, and thermodynamic parameters have been studied. The results showed an appropriate fit for Langmuir adsorption isotherm and pseudo-second order kinetics model with an adsorption capacity of 17.12 mg/g. According to the obtained values of thermodynamic parameters, the removal of Acid red 8 by CNCs hydrogels was exothermic spontaneous process.

Removal of Cadmium(II) by hydrated manganese dioxide: behaviour and mechanism at different pH

ABSTRACT Homogeneous precipitation was proposed to prepare hydrated manganese dioxide (HMO) with KMnO4 as oxidant, NaCl as reductant and HNO3 as reaction auxiliary. HMO was applied to remove Cd(II) and the effect of contact time, initial concentration, adsorbent dose and pH value on adsorption efficiency were investigated. The removal mechanisms at various pH values were analysed in detail. Adsorption thermodynamics parameters were calculated as ΔG < 0, ΔH > 0 and ΔS > 0, which meant that the adsorption process was endothermic. The result of adsorption kinetics indicated the adsorption process conformed to pseudo-second-order kinetics. When adsorbing Cd(II) with initial concentration equaling 100 mg·L−1, the activation energy (Ea) was 62.740 kJ·mol−1. The Langmuir model could describe adsorption behaviour on HMO better than the Freundlich model, indicating that the adsorption sites of HMO were homogeneous and that single-layer adsorption was a dominant way in this process. The maximum adsorption capacity of Cd(II) on MnO2 calculated by the Langmuir model was 267 mg·g−1. The adsorbent HMO could be recycled and reused for several times with a high efficiency above 70% by adding HCl. SEM, EDS, FTIR and XPS were used to analyse the mechanisms of removal of Cd(II) at pH = 3,7 and 10. The mechanisms included electrostatic attraction, ion exchange and chemical precipitation. With pH increasing, the zeta potential decreased and the surface negative charge increased, promoting Cd(II) removal through enhanced electrostatic attraction. Meanwhile, ion exchange mechanisms including inner-sphere complexation and outer-sphere complexation occurred during adsorption process at different pH.

Adsorption Isotherms and Kinetics of the Adsorption of Rare Earth Elements {La(III)&amp;Pr(III)} by Nanocobalt Ferrite

Background: Thermal decomposition of metal oxalates, which lead to transition metal oxide composite, is considered to be a versatile method for the synthesis of transition metal oxide composite and its extraordinary applications. Objectives: Nanometal oxide composite, especially, nanocobalt ferrite (CoFe2O4), is prepared efficiently in a simple, eco friendly and cost effective manner. Various characterization techniques like XRD, FTIR, SEM and EDS are applied to explore the morphology, functional groups, bonding nature and size of the nano particles synthesized. Adsorption of rare earth elements La(III) and Pr(III) onto synthesized nanocobalt ferrite is further studied using ICPAES method. Methods: Here, authors make an attempt to exploit meso porous CoFe2O4 synthesized through thermal decomposition method and exploited it as an adsorbent for the adsorption of REEs, namely Lanthanum and Praseodymium in their trivalent oxidation state La (III) &amp; Pr (III) using ICPAES technique. Results and discussion: The influencing parameters such as the adsorption efficiency, which include equilibrium time, pH, initial rare earth element concentration, adsorbent dosage and effect of temperature are studied. Adsorption isotherms, kinetics and thermodynamic parameters are analyzed. Conclusion: It is observed that adsorption studies follow pseudo second order kinetics and follow adsorption isotherms of Langmuir. The adsorption capacity is observed to be more than 90%.