Won-Gee Kim

Sorption behaviour of manganese‐coated calcined‐starfish and manganese‐coated sand for Mn(II)

The objective of the present investigation was to explore the sorption behaviour of manganese‐coated samples of calcined starfish (MCCSF) (i.e. the impregnation of calcined starfish with manganese) for the removal of low levels of an important heavy metal toxic ion, Mn(II), from aqueous solutions. The suitability of this solid was further compared with two different samples of manganese‐coated sands (MCS): MCS4 and MCS9 impregnated at pH 4.0 and pH 9.0, respectively. These comparative studies were performed in both batch and column experiments. Batch data indicated that a fairly good stability of the coating was obtained for these three samples in the pH region 2.5 to 10.0. The removal efficiency of MCCSF was fairly good in comparison with the MCS4 and MCS9 samples. These last two samples possessed similar Mn(II) removal capacities. Moreover, a small dose of sodium hypochlorite further enhanced the uptake of Mn(II) by these solids. The sorbate concentration dependence data fitted reasonably well to the Freundlich adsorption isotherm. The column data indicated that MCCSF possessed a relatively higher adsorption capacity compared with the MCS4 and MCS9 samples. The breakthrough curves obtained were then used to evaluate the apparent removal capacity of these solids under the dynamic conditions using the Thomas equation. The SEM images obtained for these manganese‐coated solids along with the virgin base materials, i.e. sand and calcined starfish, showed that manganese oxides occupied the surfaces or pores of the base materials and formed clusters on the base surface.

Application of Fe(VI) in the treatment of Zn(II)‐NTA complexes in aqueous solutions

The higher oxidation state of iron, i.e. Fe(VI), was exploited to treat the synthetic wastewater containing Zn(II)‐NTA. The decomposition of Zn(II)‐NTA by Fe(VI) was investigated with the help of analytical data obtained for the change in Fe(VI) concentration, dissolved organic carbon (DOC) and total soluble Zn(II) concentration as a function of time at various concentrations of Zn(II)‐NTA and at constant Fe(VI) concentration. The UV‐Visible data was used to explain the reaction kinetics for redox reactions between Fe(VI) and Zn(II)‐NTA. The pseudo‐first‐order rate constant was calculated keeping the Zn(II)‐NTA concentration in excess and hence the overall second‐order‐rate constant was obtained. Fe(VI) reduction was almost unaffected with the 1000 times increase in ionic strength (NaNO3), as well as in the presence of completely oxidized background electrolytes. However, Fe(VI) reduction was greatly affected in the presence of both SO3 2− and NO2 − especially at higher concentrations, indicating a competitive reduction took place between Zn(II)‐NTA and Na2SO3 or NaNO2 in the Fe(VI) treatment. These results were again supported by the dissolved organic carbon observations since relatively very low removal of the dissolved organic carbon occurred in the presence of Na2SO3 and NaNO2.

Organo-modified sericite in the remediation of phenol-contaminated waters

AbstractHexadecyltrimetyl ammonium bromide and alkyldimethylbenzyl ammonium chloride-modified sericite samples were obtained by wet cation exchange process. The solid materials were then characterized by the FT-IR and XRD data whereas the surface morphology was obtained by the scanning electron microscopic images. Further, the suitability of these solids was assessed for the decontamination of phenol-contaminated waters under the batch reactor operations. Batch reactor data showed that an increase in sorbate concentration (from 1.0 to 20.0 mg/L) favoured the uptake of phenol from aqueous solution whereas an increase in pH (from 2.0 to 10.0) caused for significant decrease in percent uptake of phenol. The equilibrium state concentration dependence data were well modelled with the Freundlich adsorption isotherm.