Preparation and characterization of hydroquinone based polyoxalate and its application in the removal of heavy metals from water

Hydroquinone based polyoxalate was synthesized from oxalyl chloride and hydroquinone. The polymer was characterized with FTIR, 1H-NMR, 13C-NMR, PXRD, SEM and thermal analysis. The chelation behaviour of the polymer towards Pb(II), Cd(II), and Hg(II) in aqueous solutions was studied by batch technique as a function of contact time and pH. The polymer showed high metal uptake toward Pb(II) and Cd(II) and moderate metal uptake toward Hg(II). The adsorption capacity was not affected by the pH of solution. The adsorption data were fitted with second order kinetic model and the isotherms models of Langmuir and Freundlich. Thermodynamics measurements showed that sorption process was spontaneous. Furthermore, the chelating polymer was loaded with metal ions using fixed bed column. For regenerating the loaded polymer, different eluting agents include HNO3, H2SO4, and EDTA was investigated. The highest recovery of metal ions was achieved using HNO3, indicating that desorption process was governed by the solubility factor and cation exchange mechanism.Â

Adsorption of lead, zinc and cadmium ions on polyphosphate-modified kaolinite clay

The aim of this research work is to determine the potential of application of sodium polyphosphatemodified kaolinite clay as an adsorbent for the removal of lead (II), zinc (II) and cadmium (II) ions from aqueous solutions. The adsorbent dosage, pH, temperature and contact time were investigated. The adsorption isotherms of all three metal ions followed well Langmuir equation. ) calculated using the Langmuir constants for metal ions sorption on the sodium polyphosphate-kaolinite clay showed that the adsorption process is spontaneous and endothermic in nature. The results of this study showed that the sodium polyphosphate-kaolinite clay powder can be efficiently used as a low-cost adsorbent for the removal of divalent lead, zinc and cadmium from aqueous solution

Solvent Extraction of Thorium(IV) by Didodecylphoric Acid

Solvent extraction of Thorium (VI) ion from perchlorate solution using didodecylphosphoric acid, DDPA, in chloroform diluent was studied. The effects of stripping hydrochloric acid concentration, stripping time, extraction time, DDPA concentration, pH, ionic strength, supporting electrolyte and temperature on the extraction processes have been studied. From the distribution coefficient values at different temperatures,the enthalpy, the free energy and the entropy changes associated with the extraction processes were determined. The composition of the complex formed was established to be Th(ClO4)4-nRn(HR)5-n where, n=1 or 2 and (HR)2 represents the dimer of DDPA

Preparation and characterization of poly(Bisphenol A-Phthalate) and its metal removal behavior toward Pb(II), Cu(II), and Cd(II) ions

ABSTRACTThe polymer poly(BPA-phthalate) (BPA-PHTH) was synthesized from BPA and phthaloyl dichloride by using interfacial condensation polymerization. The prepared polymer was characterized using (FTIR,1H-NMR, 13C-NMR, DSC, TGA, SEM, and polymer solution viscosity. The characterization by 1H-NMR, 13C-NMR, and FTIR proved the suggested structure. The DSC shows that the polymer is not linear, while the TGA shows that it is thermally stable up to 350°C. SEM showed solid surface filled with pores. The polymer uptake behavior towards Pb(II), Cd(II), and Cu(II) ions was studied by the batch equilibrium technique as a function of pH and contact time. The metal-ion uptake by the polymer reached at pH = 6 a maximum of 92.59, 65.79, and 72.46 for Pb(II), Cd(II), and Cu(II) ions, respectively. The metal ion uptake properties of the polymer show fitting for Langmuir, Freundlich, and (D-R) isotherm equations. The experimental data fit to both the Langmuir and the Freundlich models (R2 > 0.99). Column experiments were used to determine the loading capacity and study the desorption of metal ions. The metal-bound polymer was regenerated by treatment with 0.1 M HNO3 for Pb(II) and Cd(II), while 0.5 M EDTA for Cu(II). Therefore, it may be employed for the removal of heavy metal pollutants in environmental and industrial applications

A study on removal characteristics of <i>o</i>-, <i>m</i>-, and <i>p</i>-nitrophenol from aqueous solutions by organically modified diatomaceous earth

<div><p></p><p>The natural diatomaceous earth (DAT) was modified with surfactant of hexadecyltrimethylammonium bromide (HDTMABr) to form organic-modified diatomaceous earth (DAT-HDTMABr). The DAT and DAT-HDTMABr were characterized by X-ray fluorescence, X-ray diffraction, FT-IR and DTA-TG. The surface area was determined using Brunauer, Emmett, and Teller adsorption method. Cation exchange capacity was estimated using an ethylenediamine complex of copper method, and the modifier loading was calculated from the total carbon analysis. The ability of raw and organomodified diatomaceous earth to remove <i>o</i>-nitrophenol (ONP), <i>m</i>-nitrophenol (MNP), and <i>p</i>-nitrophenol (PNP) from aqueous solutions has been carried out at predetermined equilibration time, adsorbent amount, pH, and temperatures using a batch technique. The removal of ONP, MNP, and PNP from aqueous solutions by modified clay seems to be more effective than unmodified sample. The experimental equilibrium adsorption data were analyzed by four widely used two parameters, Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich (D–R) isotherm equations. Kinetic studies showed that pseudo-second-order described the adsorption experimental data better than the pseudo-first-order kinetic model. Based on the calculated thermodynamic parameters, such as enthalpy (Δ<i>H</i>), entropy (Δ<i>S</i>), and Gibb’s free energy changes (Δ<i>G</i>), it is noticeable that the adsorption of ONP, MNP, and PNP by DAT and DAT-HDTMABr adsorbents was carried out spontaneously, and the process was exothermic in nature.</p></div