Controllable synthesis of Fe3O4-wollastonite adsorbents for efficient heavy metal ions/oxyanions removal

Abstract

Iron oxide, in the form of magnetite (MG)-functionalized porous wollastonite (WL), was used as an adsorbent for heavy metal ions (cadmium and nickel) and oxyanions (chromate and phosphate) removal from water. The porous WL was synthesized from calcium carbonate and siloxane by controlled sintering process using low molecular weight submicrosized poly(methyl methacrylate) as a pore-forming agent. The precipitation of MG nanoparticles was carried out directly by a polyol-medium solvothermal method or via branched amino/carboxylic acid cross-linker by solvent/nonsolvent method producing WL/MG and WL-γ-APS/MG adsorbents, respectively. The structure/properties of MG functionalized WL was confirmed by applying FTIR, Raman, XRD, Mössbauer, and SEM analysis. Higher adsorption capacities of 73.126, 66.144, 64.168, and 63.456 mg g −1 for WL-γ-APS/MG in relation to WL/MG of 55.450, 52.019, 48.132, and 47.382 mg g −1 for Cd 2+ , Ni 2+ , phosphate, and chromate, respectively, were obtained using nonlinear Langmuir model fitting. Adsorption phenomena were analyzed using monolayer statistical physics model for single adsorption with one energy. Kinetic study showed exceptionally higher pseudosecond-order rate constants for WL-γ-APS/MG, e.g., 1.17-13.4 times, with respect to WL/MG indicating importance of both WL surface modification and controllable precipitation of MG on WL-γ-APS.

Lignin Based Porous, Microsphere-Shaped Adsorbent Functionalized with Magnetite Nanoparticles for Effective Chromate Anions Removal

“…The results presented in Table 2 show an increase of adsorption capacity as the temperature increases, while Langmuir constant remains constant and very slightly increases at the highest temperature. According to the Langmuir isotherm, assumed mechanism of chromate anions adsorption is attributed to the monolayer adsorption with equal enthalpy and energy for all reactive sites [6]. Obtained negative ΔG° values from -35.06 to -37.80 kJ mol -1 indicate that adsorption occurs via spontaneous reactions followed by both physisorption and chemisorption mechanisms [6].…”

“…The point of zero charge of the synthesized LMS-NM adsorbent was determined by the pH drift method. This analysis is undertaken to explore the influence of pH on the state of equilibrium of ionic/anionic species and protonation/deprotonation of LMS-NM functional groups [6].…”

“…Magnetic nanoparticles, such as iron oxide (Fe3O4) nanoparticles, are a potential wastewater treatment agent and can be used for the removal of contaminants from water [6]. Increased interest in its use is due because of their large surface area, high stability and, in particular due to potential reusability and extraction from water solutions, owing to its magnetic properties in a magnetic field [7].…”

Removal of Chromate and Nitrate Ions from Aqueous Solutions by CoxFe3‐xO4@silica Hybrid Nanoparticles Decorated with Cross‐Linked Tragacanth Gum: Experiment, Modeling and Optimization

“…For a favorable isotherm, R L is between 0 and 1, for an irreversible isotherm R L is zero, for linear isotherms R L =1 and unfavorable isotherms R L >1 . Table illustrates the parameters of the Langmuir isotherm for CrO 4 2− and NO 3 − at different concentrations of these ions in the range of 15–75 mg L −1 for 10 mL of an aqueous solution using 10 mg of the adsorbent.…”

“…The correlation coefficients, as opposed to those of the Langmuir model, were indicated that this isotherm model is not suitable for predicting the adsorption equilibria of CrO 4 2− and NO 3 − . Further n values of over 1 show that the adsorption condition is favorable …”