Ion adsorption components in liquid/solid systems

Effectively removing indole-3-butyric acid from aqueous solution with magnetic layered double hydroxide-based adsorbents

The magnetic layered double hydroxide-based materials (MLDHs) with the metal composition of Mg(II)Al(III) were synthesized by different conditions as the adsorbent for removal of a phytohormone, indole-3-butyric acid (IBA). The morphological characteristics of MLDHs were studied through various characterization methods such as XRD, SEM, TEM, FTIR, BET, Zeta-potential and VSM. The adsorption results showed that the adsorption capacity of MLDH-1 synthesized by co-precipitation method with ammonia as the base source was the best (maximum 522.6 mg/g). The extent of adsorption in the pH range of 3.0-9.0 was observed to be no noticeable change. From the economical point of view, 1.0 g/L MLDH-1 composites were selected as optimum parameter. For a given adsorbent concentration (C_s), its kinetics and adsorption isotherm followed the pseudo-second-order and Liu isotherm model, respectively. The adsorbed sample can be easily magnetically separated and regenerated with NaNO₃. The adsorption process was spontaneous and exothermic, including two path stages: surface adsorption of lamellar and interlayer anion exchange. The research makes a contribution to evaluating the ability of MLDHs in IBA removal and helping the public to understand the mechanism of adsorption process.

Kinetic, thermodynamic and isotherm investigations of Cu2+ and Zn2+ adsorption on LiAl hydrotalcite-like compound

LiAl hydrotalcite-like compound (LiAl HTlc) was synthesized via a hydrothermal method and used to adsorb Cu²⁺ and Zn²⁺ for investigating the adsorption characteristics of heavy metal cations. The X-Raydiffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and transmission electron microscopy (TEM) characterizations revealed the interconnecting flower-like layered structure of LiAl HTlc. The adsorption kinetics and isotherms of Cu²⁺ and Zn²⁺ on LiAl HTlc agreed with the pseudo-second-order model and the Langmuir model at a given sorbent concentration (C_s), respectively. The C_s-effect on the adsorption kinetics and isotherms was observed, and the Langmuir-surface component activity (SCA) equation could be utilized to characterize the effect of C_s in the adsorption isotherms. The adsorption process was spontaneous and endothermic. The adsorption mechanism denoted that the adsorption process was controlled using two main mechanisms, i.e., surface complexation and isomorphic substitution. This is the first report, to the best of our knowledge, on the usage of LiAl HTlc for the removal of heavy metal cations Cu²⁺ and Zn²⁺ from a solution. LiAl HTlc is a promising sorbent for treating water containing heavy metal cations.

Examination of current adsorption models for Pb(II) and Cu(II) adsorption onto Fe3O4@Mg2Al-NO3 Layered Double Hydroxide in aqueous solution

The adsorption of Pb(II) and Cu(II) onto Fe3O4@Mg2Al-NO3 Layered Double Hydroxide (LDH) as a function of Fe3O4@Mg2Al-NO3 LDH concentration was studied. An adsorbent concentration effect ( Cs effect), namely adsorption isotherm declines as adsorbent concentration ( Cs) increases, was observed. The experimental data were fitted to the adsorption models including the classic Freundlich model, the metastable-equilibrium adsorption theory, the flocculation model, the power function model, and the surface component activity model. The results show that the Freundlich-type metastable-equilibrium adsorption equation, the power function model, and the Freundlich-surface component activity equation can adequately describe the Cs effect observed in the batch adsorption tests as all the correlation coefficients ( R2) of the nonlinear plots are higher than 0.96. In other words, their intrinsic parameters simulated from the experimental data are independent of Cs value. It is considered that the Freundlich-surface component activity equation is the best model to describe the Cs effect of the studied adsorption systems by Akaike Information Criterion evaluation criterion.

Synthesis and characterization of ferric tannate as a novel porous adsorptive-catalyst for nitrogen removal from wastewater

Ferric tannate was synthesized herein using tannic acid and ferric chloride at neutral pH, showing a unique capacity for adsorption-catalyzed conversion of NH₄⁺-N and NO₂⁻-N to N₂.