Anionic Methyl Orange Removal from Aqueous Solutions by Activated Carbon Reinforced Conducting Polyaniline as Adsorbent: Synthesis, Characterization, Adsorption Behavior, Regeneration and Kinetics Study

This work investigated the elimination of Methyl Orange (MO) using a new adsorbent prepared from Activated Carbon (AC) with polyaniline reinforced by a simple oxidation chemical method. The prepared materials were characterized using XRD, TGA, FTIR and nitrogen adsorption isotherms. Furthermore, PANI@CA highest specific surface area values (near 332 m2.g− 1) and total mesoporous volume (near 0.038 cm3.g− 1) displayed the better MO removal capacity (192.52 mg.g− 1 at 298 K and pH 6.0), which is outstandingly higher than that of PANI (46.82 mg.g− 1). Besides, the process's adsorption, kinetics, and isothermal analysis were examined using various variables such as pH, MO concentration and contact time. To pretend the adsorption kinetics, various kinetics models, the pseudo first- and pseudo second- orders, were exercised to the experimental results. The kinetic analysis revealed that the pseudo second order rate law performed better than the pseudo first order rate law in promoting the formation of the chemisorption phase. In the case of isothermal studies, an analysis of measured correlation coefficient (R2) values showed that the Langmuir model was a better match to experimental results than the Freundlich model. By regeneration experiments after five cycles, acceptable results were observed.

Removal of methyl orange from from aqueous solutions using of PANI and PANI@Activated Carbon: Preparation, characterization, regeneration and comparative study

This work investigated the elimination of Methyl Orange (MO) using a new adsorbent prepared from Activated Carbon (AC) with polyaniline reinforced by a simple oxidation chemical method. The prepared materials were characterized using XRD, TGA, FTIR and nitrogen adsorption isotherms. Furthermore, PANI@CA highest specific surface area values (near 332 m2.g− 1) and total mesoporous volume (near 0.038 cm3.g− 1) displayed the better MO removal capacity (192.52 mg.g− 1 at 298 K and pH 6.0), which is outstandingly higher than that of PANI (46.82 mg.g− 1). Besides, the process's adsorption, kinetics, and isothermal analysis were examined using various variables such as pH, MO concentration and contact time. To pretend the adsorption kinetics, various kinetics models, the pseudo first- and pseudo second- orders, were exercised to the experimental results. The kinetic analysis revealed that the pseudo second order rate law performed better than the pseudo first order rate law in promoting the formation of the chemisorption phase. In the case of isothermal studies, an analysis of measured correlation coefficient (R2) values showed that the Langmuir model was a better match to experimental results than the Freundlich model. By regeneration experiments after five cycles, acceptable results were observed.

HIGHLY EFFICIENT REMOVAL OF COPPER(II) IONS FROM AQUEOUS SOLUTION BY NICKEL 2-ETHYLIMIDAZOLATE

Nickel 2-ethylimidazolate was obtained and characterized, which is used in this work as a sorbent for the removal of copper (II) ions. The sample characterization was carried out by scanning electron microscopy, low-temperature nitrogen adsorption. It was found that the obtained sorbent is a microheterogeneous material with the size of individual particles in the range of 0.4-0.7 μm. Nitrogen adsorption isotherms in the pores of nickel 2-ethylimidazolate were obtained. It was found that when processing the experimental data in linear coordinates of TVFM, linearization is reached in coordinates lnV-lnPs/P, which indicates the predominance of mesopores in the structure of nickel 2-ethylimidazolate. The total pore volume was determined from the TVFM linear coordinates. It was 0.21 cm3/g. According to obtained differential pore size distribution, the most probable average pore radius corresponds to 7.5 nm. One of the main characteristics of nickel 2-ethylimidazolate as a sorbent, the surface area was determined by the A.V. Kiselev method and amounted to 703.56 m2/g. The efficiency verification of using nickel 2-ethylimidazolate in the heavy metal ions sorption processes was carried out by removal of copper(II) ions from aqueous solutions by the limited solution volume method at different contact times. The copper(II) sorption kinetics in the presence of nickel 2-ethylimidazolate was studied by processing experimental data in the first and second orders linear coordinates. It was found that the adsorption kinetics of copper(II) ions is described by a second order model, which indicated ion-exchange adsorption. Equilibrium adsorption capacity in the sorbent-solution system is reached at a contact time of 90-120 min.

Study of the effect of the LDH cations precursors in the removal of arsenic in aqueous solution

Layered double hydroxides (LDH) are anionic clays, mainly used as adsorbents, ion exchange material, and catalysts. Generally, they present high specific surface areas, alkaline character, high metallic dispersion, and high thermal stability. If they contain a transitional element in their structure, the solid may present redox properties. LDH were synthesized with the following combinations: MgAl, MgFe, and ZnMgFe, aiming to determine the effect of cationic nature in the structure and the functionality of the synthesized clay as adsorbents in polluted aqueous effluents. The textural properties were determined by nitrogen adsorption isotherms. Crystalline structure was studied by XRD and the presence of the anions of the interlayer was determined by FTIR spectroscopy. The studies of removal of As(III) and As(V) from aqueous solutions, using the LDH, show that after 24 h the solids reach a high removal efficiency. ZnMgFe solid removed both species of arsenic with values of 95 and 98% for As(II) and As(V), respectively. The MgFe solid showed some selectivity to the uptake of As(V), while the MgAl only removed As(V). This selective behaviour can be beneficial in studies of arsenic speciation.

Ionic Transport in CsNO2-Based Nanocomposites with Inclusions of Surface Functionalized Nanodiamonds

Composite solid electrolytes (1 − x)CsNO2-xND, where ND are nanodiamonds, including those after liquid-phase and gas-phase oxidation and reduction functionalization, were prepared, and their properties investigated by XRD, analysis of BET nitrogen adsorption isotherms, IR spectroscopy and impedance spectroscopy. The electrical conductivity of composites (1 − x)CsNO2-xND obeys the Arrhenius dependence and has a maximum at x = 0.95 regardless of the ND pretreatment. It was found that the conductivity depends on the mode of functionalization of the ND surface, as well as on the processing time. The electrical conductivity of composites with ND, processed by the gas-phase method, is 1.5–2.6 times higher than that of composites with initial ND, in which the conductivity is 2 orders of magnitude higher than that of pure cesium nitrate. Thus, the possibility of using ND as an effective heterogeneous additive for the preparation of composite solid electrolytes, including cesium nitrite, has been demonstrated for the first time.

Sorption of Methylene Blue for Studying the Specific Surface Properties of Biomass Carbohydrates

The surface area is an important parameter in setting any biorefining technology. The aim of this study was to investigate the applicability of sorption of methylene blue to characterize the surface of the main biomass carbohydrates: α-cellulose, sigmacell cellulose, natural gum, β-glucan, and starch. The morphology of particles of the model objects was studied by scanning electron microscopy. Nitrogen adsorption isotherms demonstrate that the selected carbohydrates are macroporous adsorbents. The monolayer capacities, the energy constants of the Brunauer–Emmett–Teller (BET) equation, and specific surface areas were calculated using the BET theory, the comparative method proposed by Gregg and Sing, and the Harkins–Jura method. The method of methylene blue sorption onto biomass carbohydrates was adapted and mastered. It was demonstrated that sorption of methylene blue proceeds successfully in ethanol, thus facilitating surface characterization for carbohydrates that are either soluble in water or regain water. It was found that the methylene blue sorption values correlate with specific surface area determined by nitrogen adsorption/desorption and calculated from the granulometric data. As a result of electrostatic attraction, the presence of ion-exchanged groups on the analyte surface has a stronger effect on binding of methylene blue than the surface area does. Sorption of methylene blue can be used in addition to gas adsorption/desorption to assess the accessibility of carbohydrate surface for binding large molecules.

Surface Characteristics Change of Zinc Modified H-ZSM-5 Zeolites in Methanol to Hydrocarbons Transformation Process

The t-plot method is a well-known method for determining the volumes of micro- and/or mesoporous materials and the specific surface area of a sample by comparison with a reference adsorption isotherm of a non-porous material having a similar surface chemical composition. The article describes the applicability of the t-graph method to the analysis of the surface properties of zinc modified samples of zeolite H-ZSM-5 before and after the reactions of methanol transformation into hydrocarbons occur on them. Zeolites are widely used as catalysts in the petrochemical and refining industries. These materials contain active Bronsted acid sites, distributed within the microporous structure of zeolites, which leads to selective catalysis due to the difference in the pore shape of the zeolites used. The size, shape of the zeolite catalyst determines the catalytic performance in terms of both product selectivity and catalyst deactivation. In most zeolite catalyzed hydrocarbon conversion reactions, catalyst activity is lost due to carbon deposition. In this connection, the determination of the surface properties of zeolites is an important task that contributes to the disclosure of the physicochemical essence of the process of deactivation of zeolites. The recalculation of nitrogen adsorption isotherms using the t-plot model made it possible to determine the volume of micro and mesopores. Based on the t-graph data, it can be concluded that during the transformation of methanol into hydrocarbons, carbon accumulates on the surface of the zeolite. In this case, the predominant deposition of carbon on the surface of mesopores, due to the fact that in the process of decontamination, from 61 to 73% of the volume of mesopores is lost. The number of micropores also decreases, but the share of losses is 42–54%, which is 10–15% lower compared to the loss of mesopore volume.

Adsorptive-Oxidative Removal of Sulfides from Water by MnO2-Loaded Carboxylic Cation Exchangers

Hybrid ion exchangers (HIX) containing manganese(IV) oxide (MnO2) based on macroporous and gel-type carboxylic cation exchangers as supporting materials were obtained. The hybrid materials were characterized using scanning electron microscopy with energy dispersive spectrometry (SEM/EDS), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and nitrogen adsorption isotherms at 77 K and mercury porosimetry. HIX with introduced MnO2 (20.0–32.8 wt% Mn) were tested for removal of dissolved sulfides from anoxic aqueous solutions with 100–500 mg S2−/dm3 concentrations. The process proceeded effortlessly at pH 10–13 despite unfavorable electrostatic interactions of the reactants. The highest exhibited sorption capacity was 144.3 ± 7.1 mg S2−/g. Approximately 65% of dissolved sulfides were oxidized to S2O32− ions and repelled from HIX structure. On average, 13% of sulfide removal products were adsorbed by the MnO2 surface. The impact of MnO2 load and the ionic form of HIX functional groups on removal of sulfides and resulting products was examined. The mechanism of the process is suggested.