Synthesis of clay-based superabsorbent composite and its sorption capability.

A novel superabsorbent composite was synthesized by copolymerization reaction of partially neutralized acrylic acid (AA) on bentonite micropowder using N,N'-methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator in aqueous solution. The superabsorbent composite (SAC) was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The water retention test of SAC was also performed. The water absorbency of SAC synthesized was found to be 352 and 110 g H(2)Og(-1) in distilled water and 0.2% NaCl, respectively. Sorption capacity of SAC was investigated for heavy metal ions (HMI) using Langmuir and Freundlich model of adsorption. The maximum adsorption capacity (Q(m)) of HMI onto the bentonite-based SAC from their solution was 1666.67, 270.27, 416.67 and 222.22 mg g(-1) for Pb(II), Ni(II), Cd(II) and Cu(II), respectively. All results suggested that SAC offers excellent potential for HMI removal from contaminated water.

The characterization of prepared organomontmorillonite (DEDMAM) and sorption of phenoxyalkanoic acid herbicides from aqueous solution.

The montmorillonite has been subjected to modification through ion-exchange reaction by N,N'-didodecyl-N,N'-tetramethylethanediammoniumdiiodide (DEDMAI). The modified sample was studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). The basal spacing of modified montmorillonite was determined as 28.72 A. The IR spectra of organomontmorillonite showed changes in C-H vibrations. The characterization of N,N'-didodecyl-N,N'-tetramethylethanediammonium montmorillonite (DEDMAM) and the adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4-dichlorophenoxybutyric acid (2,4-DB), 4-chloro-2-methylphenoxyacetic acid (MCPA), and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) on organomontmorillonite was studied as a function of the solution concentration. The adsorption energy (E) and adsorption capacity (qm) for phenoxyalkanoic acid herbicides adsorbing on organomontmorillonite (DEDMAM) were estimated using the Dubinin-Radushkevic (D-R) equation. These isotherms were modeled according to Freundlich and Dubinin-Radushkevic adsorption isotherms. The sorption of the herbicides on DEDMAM increased in order of MCPA<2,4-D<2,4-DB<2,4,5-T.

Removal of 2,4-dichlorophenoxyacetic acid from aqueous solutions by partially characterized organophilic sepiolite: thermodynamic and kinetic calculations.

The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) on organophilic sepiolite (dodecylammonium sepiolite, DAS) was studied as a function of solution concentration and temperature. The observed adsorption rates were found to be equal to the first-order kinetics. The rate constants were calculated for temperatures ranging between 25 and 40 degrees C at constant concentration. The adsorption energies, E, and adsorption capacity, q(m), for 2,4-D adsorption on organophilic sepiolite was estimated using the Dubinin-Radushkevic equation. Thermodynamic parameters (Deltag(a), Deltah(a), Deltas(a)) were determined by a new approximation from the isotherm of 2,4-D adsorption on DAS. Also, DeltaS(0) and DeltaH(0) values were calculated from the van't Hoff equation. These isotherms were modeled according to the Freundlich and Dubinin-Radushkevic adsorption equations. The amount of adsorption of this herbicide on organophilic sepiolite was found to be dependent on the relative energies of adsorbent-adsorbate, adsorbate-solvent, and adsorbate-adsorbate interaction.

The removal of phenolic compounds from aqueous solutions by organophilic bentonite.

The adsorption of p-chlorophenol (p-CP) and p-nitrophenol (p-NP) on organophilic bentonite (dodecylammonium bentonite, DDAB) was studied as a function of solution concentration and temperature. The observed adsorption rates were found to be equal to the first-order kinetics. The rate constants were calculated for temperatures ranging between 25.0-35.0 degrees C at constant concentration. The adsorption energies, E and adsorption capacity, (qm), for phenolic compounds adsorbed to organophilic bentonite were estimated by using the Dubinin-Radushkevic equation. Thermodynamic parameters from the adsorption isotherms of p-CP and p-NP on organophilic bentonite were determined. These isotherms were modeled according to Freundlich and Dubinin-Radushkevic adsorption isotherms and followed the V-shaped isotherm category with two steps. The amount of adsorption was found to be dependent on the relative energies of adsorbent-adsorbate, adsorbate-solvent and adsorbate-adsorbate interaction.