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This study reports the application of hydrated lime for the effective adsorption of the heavy mercury metal from the aqueous phase solutions. Initially, hydrated lime was subjected to structural characterization and thermal stability analysis. The FT-IR spectrum analysis revealed that the existence of the O–H bonds as a confirmation of hydrated lime formation. Subsequently, the XRD powder-based analysis demonstrated that most of the hydrated lime is pure crystalline material known as Portlandite while a small amount of calcite is also present in the structure of the hydrated lime. The thermal stability analysis revealed that the hydrated lime is highly thermally stable under harsh conditions without decomposing at higher temperatures up to 500 °C. Furthermore, the hydrated lime was subjected to the selective adsorption of heavy metal mercury to investigate the potential influence of the adsorbent particle size and loading on adsorption capacity. The results demonstrated that the decrease in the adsorbent particle size leads to the improvement in the mercury adsorption attributing to the rise in specific surface area. The enhancement in the loading of the adsorbent resulted in a reduction in mercury adsorption directing to the fact that already adsorbed metal ions onto the adsorbent surface lead to hindrance for the adsorption of other ions of heavy metal. These results lead to a significant impact on modern in inventing different adsorbents with promising water treatment efficiency for more industrial applications and the related recovery of mercury. [Display omitted] • Batch experimentation for mercury removal via hydrated lime reported. • The hydrated lime characterization has been discussed. • Uptake capacity reduced with increase in loading and particle size. • Adsorption isotherms study revealed that adsorption process is appropriate. [ABSTRACT FROM AUTHOR]

The ligand structure and optimized calcination temperature and time of Zn-MOF produced carbon encapsulated ZnO nanostructure that showed excellent dye adsorption from water. [Display omitted] • Synthesis of nitrogen doped carbon encapsulated ZnO hybrid nanostructures from Zn-MOFs. • Optimizing the reaction condition and ligand structure for ZnO preparation. • Enhanced cationic dye adsorption by ZnO-NC hybrid nanostructures. • Removal of dyes by filtration through ZnO hybrid nanostructures as column packing materials. • Kinetics and adsorption isotherm models were evaluated. Water pollution by organic dyes poses great challenge to the environment as well as living organisms. Herein, we have fabricated nanoplates of ZnO in carbon matrix by controlled calcination of zinc-metal organic frameworks (Zn-MOFs) and used as adsorbents for efficient removal of organic dyes from water. Zn-MOF of phthalic acid and 5-nitrophthalic acid produced nanoplates of ZnO (ZnO-C and ZnO-NC) in carbon matrix without and with nitrogen doping. The fabricated hybrid nanostructures were characterized using PXRD, FTIR, BET, TGA, HR-SEM, HR-TEM and XPS analysis. Both ZnO-C and ZnO-NC showed high adsorption of cationic dyes (crystal violet (CV), methylene blue (MB) and Rhodamine B (Rh B)) compared to anionic dyes (methyl orange (MO) and Eosin yellow (EY)). Nitrogen doped ZnO-NC exhibited relatively higher percentage of dyes removal (99 %) compared to ZnO-C. Interestingly, ZnO-NC showed high adsorption of MB dye across the pH range from acidic (pH = 3.0) to alkaline (pH = 11.0). The zero-point charge indicated the negative surface charge for ZnO-NC/ZnO-C that facilitated electrostatic interactions between dyes and adsorbents. Adsorption kinetics suggested a pseudo second order model and adsorption isotherm fitted well with the Freundlich model, suggesting heterogenous adsorption with multilayer coverage of dye molecules. The reusability of ZnO-NC showed only slight reduction of adsorption in three successive cycles. Further, ZnO-NC was used as column packing materials for the successful removal of both cationic as well as anionic dyes upon filtration. Thus, the present studies provided insight on the organic ligand structure and calcination temperature of MOFs for transforming them into effective organic dye adsorbent. [ABSTRACT FROM AUTHOR]

Abstract Novel smart polystyrene-poly(N -isopropylmethacrylamide-acrylic acid) [PSt@p(NIPMAM-Aac] core/shell gel particles were prepared by two step precipitation polymerization method and used as adsorbent for removal of heavy metal ions such as Pb(II), Cu(II), Cd(II) and Cr(III) from aqueous medium. The adsorption capacity of gel particles for Pb(II), Cu(II), Cd(II) and Cr(III) ions was found as 555.6, 526.3, 476.2 and 434.8 mg/g, respectively. Adsorption process was also studied under different adsorption conditions such as adsorbent dose, metal ions concentration, agitation time, pH and temperature. Adsorption isotherms study was performed for heavy metal ions removal under optimum adsorption conditions. Langmuir and Freundlich adsorption isotherms were employed to evaluate the mechanism of adsorption process. Kinetic study showed the adsorption process followed pseudo second order kinetics. Thermodynamic study enlightens the nature of adsorption process on the basis of thermodynamic parameters such as standard Gibbs energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°). Fourier transform infrared (FTIR) spectroscopy was used to elucidate the characteristics of gel and metal ions loaded gel particles. pH sensitivity and size of gel particles were evaluated by dynamic light scattering (DLS) and transmission electron microscopy (TEM), respectively. Recoverability and reusability of gel particles for Pb(II) ions removal were also studied to investigate the repeated usage of our reported adsorbent for removal of pollutants from aqueous medium. Graphical abstract Unlabelled Image Highlights • Core/shell polymer particles with narrow size distribution were successfully synthesized. • Core/shell microgel particles have excellent ability to extract heavy metals from aqueous medium. • Langmuir adsorption isotherm model best interprets the metal ions adsorption process. • The adsorbent system has high stability and recoverability and can be re-used. [ABSTRACT FROM AUTHOR]

CO 2 sequestration into coalbed seams is one of the practical routes for mitigating CO 2 emissions. The adsorption mechanisms of CO 2 onto Malaysian coals, however, are not yet investigated. In this research CO 2 adsorption isotherms were first performed on dry and wet Mukah-Balingian coal samples at temperatures ranging from 300 to 348 K and pressures up to 6 MPa using volumetric technique. The dry S1 coal showed the highest CO 2 adsorption capacity of 1.3 mmol g−1, at 300 K and 6 MPa among the other coal samples. The experimental results of CO 2 adsorption were investigated using adsorption isotherms, thermodynamics, and kinetic models. Nonlinear analysis has been employed to investigate the data of CO 2 adsorption onto coal samples via three parameter isotherm equilibrium models, namely Redlich Peterson, Koble Corrigan, Toth, Sips, and Hill, and four parameter equilibrium model, namely Jensen Seaton. The results of adsorption isotherm suggested that the Jensen Seaton model described the experimental data well. Gibb's free energy change values are negative, suggesting that CO 2 adsorption onto the coal occurred randomly. Enthalpy change values in the negative range established that CO 2 adsorption onto coal is an exothermic mechanism. Webber's pore-diffusion model, in particular, demonstrated that pore-diffusion was the main controlling stage in CO 2 adsorption onto coal matrix. The activation energy of the coals was calculated to be below −13 kJ mol−1, indicating that adsorption of CO 2 onto coals occurred through physisorption. The results demonstrate that CO 2 adsorption onto coal matrix is favorable, spontaneous, and the adsorbed CO 2 molecules accumulate more onto coal matrix. The observations of this investigation have significant implications for a more accurate measurement of CO 2 injection into Malaysian coalbed seams. • CO 2 adsorption was investigated onto dry and wet coals at 300–348 K and 6 MPa • CO 2 interacts with the coal surface at high pressure in presence of water molecules. • Enthalpy value change confirmed that CO 2 adsorption with coal is an exothermic process. • Jensen Seaton model showed CO 2 adsorption best compliance with the experimental data. • Webber's pore-diffusion model showed the pore-diffusion was the major controlling step. [ABSTRACT FROM AUTHOR]