Search

• SG-G0∼SG-G4.0 could be potentially used as effective adsorbents for the removal of Cd(II). • The adsorption capacity does not increase accordingly with the increase of dendrimer generation. • Adsorption kinetic can be described by the pseudo-second-order model. • Adsorption isotherm follows Langmuir model with monolayer adsorption behavior. • The adsorption mechanism was revealed by combining experiment and DFT calculation. The adsorption behavior of polyamidoamine (PAMAM) dendrimers functionalized silica (SG-G0∼SG-G4.0) for Cd(II) from aqueous solution was investigated by combining experimental and theoretical method. The influences of dendrimer generation, terminal functional group, solution pH, contact time, temperature, as well as the initial concentration of Cd(II) on the adsorption behavior were explored. Static adsorption indicates that the adsorption capacity increases first and then decreases with the increase of dendrimer generation, SG-G2.0 and SG-G2.5 possess the highest adsorption capacity for amino- and ester-terminated PAMAM functionalized silica, respectively. The optimal adsorption pH value is 6 for all the adsorbents. Kinetic adsorption implicates that the adsorption can approach equilibrium at about 200 min. The kinetic adsorption follows pseudo-second-order kinetic model and is dominated by film diffusion. The isotherm adsorption demonstrates that the adsorption favors high concentration and the adsorption capacity first increases and then decreases with the increase of temperature. Adsorption isotherm process can be well described by Langmuir model. FTIR technique and DFT calculation reveal that the involvement primary and secondary nitrogen atoms, as well as carbonyl oxygen atoms dominate the adsorption. As SG-G0∼SG-G4.0 displays excellent adsorption performance for Cd(II), they could be potentially used as effective adsorbents for the decontamination of aqueous Cd(II). [ABSTRACT FROM AUTHOR]

Water pollution caused by Cr(III) is a serious environmental problem which bring adverse effect to environmental protection and public safety. Efficient removal of Cr(III) from aqueous solution is important for the remediation of Cr(III) pollution. Herein, a series of silica-gel/polyamidoamine (PAMAM) dendrimer hybrid materials (SG-G0~SG-G4.0) were used for the removal of Cr(III) from aqueous solution. The factors that affect the adsorption were extensively studied and the adsorption mechanism was demonstrated based on the experimental results and density functional theory (DFT) calculation. Result demonstrates the adsorption capacity of ester-terminated silica-gel/PAMAM dendrimers follow the order of SG-G2.5 > SG-G3.5 > SG-G1.5 > SG-G0.5, while that of amino-terminated ones decrease in the order of SG-G2.0 > SG-G4.0 > SG-G3.0 > SG-G1.0 > SG-G0. The highest adsorption is achieved at pH 4.0 for both ester- and amino-terminated materials. Adsorption kinetic indicates the adsorption equilibrium can be reached at about 240 and 180 min for amino- and ester-terminated hybrids, respectively. Adsorption kinetic can be well fitted by pseudo-second-order kinetic model with film diffusion process as the rate-limiting step. Adsorption isotherm follows Langmuir model with monolayer adsorption behavior. Fourier transform infrared spectra (FTIR) indicate the adsorption of Cr(III) by PAMAM dendrimer mainly involve the participation of N–H and C=O groups. DFT calculation demonstrates the uptake of Cr(III) by ester-terminated adsorbents mainly involves carbonyl oxygen and secondary amine nitrogen atoms to form tetra-coordinated chelate, while that of amino-terminated one tends to form hexa-coordinated chelates by carbonyl oxygen, primary and secondary amine nitrogen atoms. [ABSTRACT FROM AUTHOR]

Highlights • SiO 2 -G0∼SiO 2 -G4.0 exhibit good adsorption performance for Mn(II). • The adsorption capacity is affected by the terminal group and generation of PAMAM dendrimer. • The adsorption mechanism was revealed combined experiment and DFT calculation. • The adsorption proceeds chemically and charge transfer occurs from PAMAM to ion during adsorption. Abstract The adsorption of Mn(II) from aqueous solution by silica-gel supported polyamidoamine (PAMAM) dendrimers (SiO 2 -G0∼SiO 2 -G4.0) were investigated using experimental and DFT method. The effects of terminal group, dendrimer generation, pH, time, temperature, initial Mn(II) concentration, and adsorbent dosage on the adsorption were investigated. Results indicate the adsorption capacity of amino-terminated PAMAM dendrimers is higher than the corresponding ester-terminated ones. The adsorption capacity of ester- and amino-terminated PAMAM dendrimers follow the order of SiO 2 -G3.5 > SiO 2 -G2.5 > SiO 2 -G1.5 > SiO 2 -G0.5, and SiO 2 -G3.0 > SiO 2 -G2.0 > SiO 2 -G4.0 > SiO 2 -G1.0 > SiO 2 -G0, respectively. Adsorption kinetic follows pseudo-second-order model and is controlled by film diffusion process. Adsorption isotherm can be well fitted by Langmuir model and proceeds by chemical mechanism. Thermodynamic parameters suggest the adsorption is spontaneous, endothermic, and entropy increased process. FTIR analysis and DFT simulation indicate ester-terminated PAMAM dendrimers mainly coordinate with Mn(II) by carbonyl O and secondary N atoms to form tetra-coordinated chelates, while that of amino-terminated ones tend to bind Mn(II) with primary and secondary amine N atoms, and carbonyl O atoms in penta-coordinated manners. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Schiff-base functionalized superparamagnetic Fe 3 O 4 composites (Fe 3 O 4 @SiO 2 -HO-S and Fe 3 O 4 @SiO 2 -HE-S) were synthesized by homogeneous and heterogeneous method, respectively. Their structures were characterized by FTIR, elemental analysis, SEM, TEM, TGA, XRD, and porous structure analysis. The feasibility of Fe 3 O 4 @SiO 2 -HO-S and Fe 3 O 4 @ SiO 2 -HE-S for the removal of Pb(II) and Cd(II) from aqueous solution was systematically investigated. The effects of pH, time, temperature, and initial metal ions concentration on the adsorption were determined. Results demonstrated that the optimal adsorption pH for both Pb(II) and Cd(II) is 6. Adsorption kinetic showed that the adsorption equilibrium time for Pb(II) and Cd(II) are 270 and 210 min, respectively. Adsorption kinetic followed pseudo-second order model and dominated by film diffusion process. Isotherm adsorption indicated that the adsorption capacity increased with the increase of metal ion concentration and temperature. The isotherm adsorption process can be well depicted by Langmuir isotherm model. Thermodynamic parameters indicated that the adsorption process is spontaneous, endothermic, and randomness-increasing process. FTIR and DFT calculation demonstrated the interaction between N atom and metal ion dominated the adsorption of Pb(II) and Cd(II), while O atom also participated in the coordination. Charge transfer occurred from Schiff base ligand to Pb(II) and Cd(II) during the adsorption process. [ABSTRACT FROM AUTHOR]

Highlights: [•] PMPSQ was promising adsorbent for the removal of Hg(II) and Mn(II). [•] The adsorption kinetics followed the pseudo-second-order model. [•] The adsorption isotherms can be described by the monolayer Langmuir model. [•] The adsorption was controlled by film diffusion and chemical ion-exchange mechanism. [ABSTRACT FROM AUTHOR]

Type of functional groups of the adsorbent is crucial for an adsorption process which significantly affects adsorption rate and adsorption capacity for certain adsorbate. In this study, attapulgite (APT) was modified with different amino groups and the adsorbents obtained were used to remove toxic organic dyes from aqueous solution. Five adsorption kinetic models and three adsorption isotherm models were employed to estimate the adsorption behaviors for organic dyes methylene blue (MB) and Congo red (CR) onto the adsorbents. The results showed that adsorption behaviors of the adsorbents for MB were different from those for CR, and among the four adsorbents, APT exhibited the highest adsorption capacity for MB (307.27 mg/g) while APT modified with hyperbranched polyamide-amine (APT-(3)) had the highest adsorption capacity for CR (1277.33 mg/g) according to adsorption kinetic data, indicating the type of amino groups did have a significant impact on adsorption. It can be concluded that APT-(3) exhibited certain adsorption selectivity for CR. In addition, the adsorption of MB and CR was a fast and highly efficient process. The results indicated that the APT samples used can remove and enrich cationic and anionic dyes and can be potentially used in the wastewater treatment. [Display omitted] • APT is nontoxic as it has been used as decolorizing agent for some edible oils. • APT was modified by different amino groups and used to remove toxic organic dyes. • APT-(3) showed certain adsorption selectivity for CR compared to MB. • APT samples can be used potentially for removal of toxic CR and MB from aqueous solution. [ABSTRACT FROM AUTHOR]

• Silica supported thiosemicarbazide (SG-GPTS-ATS) was synthesized. • SG-GPTS-ATS exhibits superior adsorption property in ethanol for both Cu(II) and Zn(II). • The adsorption mechanism was reveal combined the results of XPS analysis and DFT calculation. Silica supported thiosemicarbazide (SG-GPTS-ATS) was synthesized for adsorption of Cu(II) and Zn(II) from ethanol and aqueous solutions, respectively. SG-GPTS-ATS was fully characterized and the adsorption property was systematically investigated. Result illustrates the adsorption capacity of SG-GPTS-ATS for both Cu(II) and Zn(II) in ethanol solution is superior than that in aqueous solution. The equilibrium adsorption time for Cu(II) is 150 min in both solutions, while these for Zn(II) are 130 and 160 min in ethanol and aqueous solution. Adsorption kinetic illustrates the adsorption is controlled by film diffusion step and follows pseudo-second-order model. The adsorption isotherm shows the uptake of Cu(II) and Zn(II) can be increased by increasing the initial concentration of metal ion and temperature in both ethanol and aqueous solution. The adsorption is proceeded by monolayer behavior and is endothermic, spontaneous, and entropy increased in nature. The adsorption mechanism analysis illustrates the capture of Cu(II) and Zn(II) by SG-GPTS-ATS is mainly dominated by hydroxyl O, secondary amine N, and S atoms. [ABSTRACT FROM AUTHOR]

Zr-based MOFs hybridized by attapulgite (APT) were successfully prepared by simple reflux method and characterized by FTIR, BET, XRD, TGA and XPS. Both cationic and anionic dyes were efficiently, quickly and simultaneously adsorbed by UiO-66, 1%APT/UiO-66 and 5%APT/UiO-66 in 5 min. In anionic dyes (Congo red and alizarin yellow GG) and cationic dye methylene blue, adsorption capacities of UiO-66, 1%APT/UiO-66 and 5%APT/UiO-66 for Congo red were higher, 304.07, 585.00 and 394.63 mg/g, respectively. Capillary effect was adopted to explain characteristic trend of adsorption kinetic curves (first decrease and then increase of adsorption capacity in the second stage). Pseudosecond-order kinetic model and Langmuir isotherm was the best-fit model to evaluate adsorption behaviors of UiO-66, 1%APT/UiO-66 and 5%APT/UiO-66 for adsorption of Congo red. It was more favorable and effective for prepared materials to removal Congo red from solutions containing inorganic salts. When concentration of NaCl was 0.09 mol/L, adsorption capacities of 1%APT/UiO-66 were increased to 589.77, 724.56 and 635.59 mg/g, accordingly. UiO-66, 1%APT/UiO-66 and 5%APT/UiO-66 exhibited good stability and reusability. Main adsorption driving forces were hydrogen bonding interactions, π-π conjugations, electrostatic interactions and sieving effects, and adsorption driving forces of 1%APT/UiO-66 were largest. Above results indicated that UiO-66 hybridized by APT could simultaneous and ultrafast removal of anionic and cationic dyes in aqueous solution, and were potential adsorbents in practical application. [Display omitted] • UiO-66 hybridized by attapulgite were fabricated by simple refluxing method. • Capillary effect was applied to explain characteristic trend of adsorption kinetic. • 1%APT/UiO-66 could simultaneous and ultrafast remove anionic and cationic dyes. • Adsorption forces were hydrogen bonding, π-π, electrostatic and sieving effects. • The presence of salt ions was beneficial to increase of adsorption capacity. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Poly(ionic liquid)-based adsorbents were prepared through ionic self-assembly method. • The adsorbent showed fast adsorption and high adsorption capacity for anionic dyes. • The adsorbent can selectively remove anionic dyes from mixed dyes aqueous solutions. Abstract In this work, poly(ionic liquid)-based porous hybrid materials were facilely prepared through ionic self-assembly method and proposed as adsorbents for removal and separation of ionic dyes. PIL, namely poly-[ N , N -dimethyl-dodecyl-(4-vinylbenzyl)ammonium chloride], was synthesized by simple radical polymerization and directly assembled with the multi-charged anionic cluster of polyoxometalate (POM) to yield PIL/POM hybrid materials without involving any toxic organic solvents and tedious modification processes. The obtained hybrid materials were characterized by various techniques and utilized as adsorbents for removal of a variety of ionic dyes from water. By adjusting the proportion of PIL and POM in the hybrid materials, the adsorption capability and selectivity towards cationic and anionic dyes could be effectively regulated. The preferred adsorbent showed fast adsorption rate and large adsorption capacity, and was able to selectively remove anionic dyes from cationic/anionic mixed dyes aqueous solutions. Furthermore, the used adsorbent can be easily collected and regenerated. All the results demonstrate that the PIL/POM hybrid material is an efficient, durable and sustainable adsorbent in water purification treatment. [ABSTRACT FROM AUTHOR]

Silica-gel functionalized with 3-amino-1,2-propanediol (SG-AP) was used as adsorbent for the removal of copper ions from both aqueous and ethanol solutions. The adsorption isotherms and adsorption kinetics were comparatively investigated by using batch method. The static saturated adsorption amount for Cu 2+ in ethanol is less than that in aqueous, indicating a much lower adsorption rate. The experimental data were fitted to pseudo-first-order and pseudo-second-order kinetic models. The results indicated that all the adsorption data in both solutions fitted well with the second-order kinetic model, implying that SG-AP is suitable to apply in the low initial concentration of copper ions in aqueous or ethanol solution. The adsorption isotherms were fitted by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models. It was showed that the adsorption processes in both aqueous and ethanol solutions were favorable and Freundlich model was much appropriate. From the D-R isotherm model, the calculated mean free energy E showed that the adsorptions occurred in aqueous via physical processes, while those in ethanol mainly via chemical processes. Desorption study showed that SG-AP had good durability as well as good efficiency for repeated use. [ABSTRACT FROM AUTHOR]

Abstract: Two types of silica gel supported amidoxime (SG-HE-AO and SG-HO-AO) adsorbents were prepared via the reactions of silica gel supported acrylonitrile functional group (SG-AN) with hydroxylamine under alkaline conditions. The SG-AN was obtained by so-called “heterogeneous” and “homogeneous” methods and named SG-HE-AN and SG-HO-AN, respectively. All the structures of adsorbents and intermediate were characterized by FT-IR, SEM, porous structure analysis and elemental analysis. The amidoxime group content of SG-HE-AO and SG-HO-AO were 1.28 and 0.77mmolg−1, respectively, indicating that the heterogeneous method is more effective than the homogeneous method to anchored functional groups onto the surface of silica gel in this study. In terms of Hg(II) adsorption, SG-HE-AO exhibited better capability than SG-HO-AO. The adsorption kinetics of the two adsorbents followed the pseudo second-order process in the temperature range of 5–35°C. Increased temperature was beneficial to adsorption. Langmuir and Freundlich isotherm models were both applied to experimental data analysis, and the former proved to be a better fit. Finally, in Hg(II)–Pb(II), Hg(II)–Ag(I), Hg(II)–Cu(II) and Hg(II)–Ni(II) binary systems, both SG-HE-AO and SG-HO-AO exhibited excellent adsorption selectivity for Hg(II). [Copyright &y& Elsevier]

Schiff-base functionalized magnetic Fe 3 O 4 were prepared by feasible one-pot subsequent homogeneous method (Fe 3 O 4 @SiO 2 –HO–S) and heterogeneous method (Fe 3 O 4 @SiO 2 -HE-S), respectively. The as-prepared adsorbents were used for the adsorption of aqueous Hg(II) and Ag(I). The effects of solution pH, time, temperature, coexisting metal ions, and initial metal ion concentration on the adsorption were investigated. The as-synthesized adsorbents were characterized by transmission electron microscope, scanning electron microscope, and X-ray photoelectron spectroscopy. The effect of solution pH indicates the optimal adsorption pH is 6. The adsorption equilibrium time are 180 and 220 min for both Hg(II) and Ag(I) under the concentration of 0.002 and 0.004 mol L−1, respectively. The adsorption kinetic process is proved to be dominated by film diffusion process and follows pseudo-second-order kinetic model. The adsorption isotherm process is proceeded by chemical mechanism and can be described by Langmuir model. Thermodynamic parameters indicate that the adsorption process is spontaneous, endothermic, and entropy increase. Adsorption selectivity demonstrates Fe 3 O 4 @SiO 2 -HE-S and Fe 3 O 4 @SiO 2 –HO–S exhibit good adsorption selectivity for Hg(II). The adsorption mechanism demonstrates the N atoms of Schiff base functional group mainly dominate the adsorption of Fe 3 O 4 @SiO 2 -HE-S and Fe 3 O 4 @SiO 2 –HO–S for metal ions. The regeneration property indicates the adsorbents can be reused with practical value. Image 1 • Magnetic Fe 3 O 4 composites were used for the removal of Hg(II) and Ag(I). • The adsorption mechanism were revealed based on experiment and DFT calculation. • The composites exhibit excellent adsorption capacity and selectivity for Hg(II). [ABSTRACT FROM AUTHOR]