Discharges of heavy metals from different sources to the water lead to water hardness which is the major problem of the world due to their toxic and carcinogenic nature. Among several methods to eliminate heavy metals, absorption is the leading technique for the removal of heavy metals from wastewater because it is efficient, available, low-cost, and eco-friend. This review paper gives detail information about adsorbents on both conventional and nanostructured materials, either occur naturally or available commercially. The review also contains properties and parameters which affect the adsorption process with essential clarifications that are given by researchers.

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Various Absorbents and Parameters Affecting Removal of Water Hardness from Wastewater: Review

Our ability to characterize the physical and chemical properties of gas–liquid interfaces is limited by the information content of surface-sensitive methods. Dynamical observables from gas–liquid s...

Scattering-Angle Randomization in Nonthermal Gas–Liquid Collisions

Equations of motion for a fast, light rare gas atom passing over a liquid surface are derived and used to infer the dynamics of neon collisions with squalane and perfluorinated polyether surfaces from experimental data. The equations incorporate the local mode model of a liquid surface via a stochastic process and explicitly account for impulsive collisional energy loss to the surface. The equations predict angular distributions for scattering of neon that are in good quantitative agreement with experimental data. Our key dynamical conclusions are that experimental angular distributions derive mainly from local mode surface topography rather than from structural features of individual surface molecules, and that the available data for these systems can be accounted for almost exclusively by single collisions between neon atoms and the liquid surface.

A stochastic, local mode study of neon-liquid surface collision dynamics.

Inelastic collisions of OH with an inert liquid perfluoropolyether (PFPE) surface have been studied experimentally. A pulsed molecular beam of OH with a kinetic energy distribution peaking at 35 kJ mol-1 was directed at a continually refreshed PFPE surface. OH molecules were detected state-selectively with spatial and temporal resolution by pulsed, planar laser-induced fluorescence. The scattered speed distributions were confirmed to be strongly superthermal, regardless of the incidence angle (0° or 45°). Angular scattering distributions were measured for the first time; their reliability was confirmed through extensive Monte Carlo simulations of experimental averaging effects, described in Paper II [A. G. Knight et al., J. Chem. Phys. 158, 244705 (2023)]. The distributions depend markedly on the incidence angle and are correlated with scattered OH speed, consistent with predominantly impulsive scattering. For 45° incidence, the angular distributions are distinctly asymmetric to the specular side but peak at sub-specular angles. This, along with the breadth of the distributions, is incompatible with scattering from a surface that is flat on a molecular scale. New molecular dynamics simulations corroborate the roughness of the PFPE surface. A subtle but unexpected systematic dependence of the angular distribution on the OH rotational state was found, which may be dynamical in origin. The OH angular distributions are similar to those for kinematically similar Ne scattering from PFPE and hence not strongly perturbed by OH being a linear rotor. The results here are broadly compatible with prior predictions from independent quasiclassical trajectory simulations of OH scattering from a model-fluorinated self-assembled monolayer surface.

/pdf/inelastic-scattering-of-oh-from-a-liquid-pfpe-surface-1m2dqfpe.pdf

Inelastic scattering of OH from a liquid PFPE surface: Resolution of correlated speed and angular distributions.

https://drum.lib.umd.edu/bitstream/handle/1903/7761/umi-umd-5043.pdf;sequence=1

Title of Document: HIERARCHICAL INTERMOLECULAR INTERACTION MODELS OF N-HETEROAROMATIC STM ADLAYER STRUCTURES

Angle resolved X-ray photoelectron spectroscopic (XPS) studies of a series of perfluoropolyethers of general formula F[CF(CF3)CF2O] n CF2CF3, where n = 27, 65, and >70, show that there is preferential ordering of-CF3 groups at the liquid surfaces. The C 1s intensity corresponding to the -CF3 groups increases with decrease in the electron take-off angle. No measurable change in the oxygen or fluorine intensity is observed upon varying the electron take-off angle. However, experiments show that no adsorption site exists at the surfaces, indicating that the ether oxygens are not available for any of the surface processes. Relative enhancement of the C 1s intensity of the -CF2/CF3 group with decreasing take-off angle is different for different liquids, with smaller chain length liquids showing a more rapid change. This is explained as due to an increase in helicity and tilt of molecular chains from the surface normal. Computational studies have been performed at the semiempirical level to understand the mo...

http://www.dstuns.iitm.ac.in/listpdf/57.pdf

T. Pradeep

Papers

Tilted orientation of molecular chains at the surface of a series of perfluoropolyether liquids: an X-ray photoelectron spectroscopic investigation