Carboxymethyl-Chitosan Cross-Linked 3- Aminopropyltriethoxysilane Membrane for Speciation of Toxic Chromium from Water

Adsorption of Cr(VI) from aqueous solution onto the nanomaterials prepared by modified chitosan was investigated in a batch system to evaluate the efficiency of biomass as an adsorbent. The crosslinking materials of chitosan & silicon dioxide and carboxymethyl chitosan & silicon dioxide were synthesized, respectively, as new adsorbent materials for the removal of Cr(VI) from aqueous solutions. The adsorption potential of Cr(VI) by the nanomaterials for desalination was investigated by varying experimental conditions such as pH, contact time and the dosage of the nanomaterials. Adsorption isotherms of Cr(VI) onto the membrane were studied with varying initial concentrations under optimum experiment conditions. The surface property of the membrane was characterized by SEM (scanning electron microscope) and Fourier transform infrared spectrometer (FT-IR). The concentrations of Cr(VI) in solution are determined by ICP-AES (inductively coupled plasma atomic emission spectrometry). The membrane of carboxymethyl chitosan & silicon dioxide exhibited higher adsorption capacity than the membrane of chitosan & silicon dioxide for Cr(VI). The adsorption sites and specific surface area may be increased by changing from chitosan to carboxymethyl chitosan. The maximum adsorption capacity was estimated as 80.7 mg·g−1 for Cr(VI) under the optimum conditions

Adsorption of Heavy Metals on Layered Double Hydroxides (LDHs) Intercalated with Chelating Agents

Layered double hydroxides (LDHs) are lamellar ionic compounds containing a positively charged layer and exchangeable anions in the interlayer. In this study, LDHs intercalated with chelating agents were synthesized by anion exchange reaction. The materials synthesized in this work were characterized by chemical analysis, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and powder X-ray diffraction (XRD) to confirm their properties. Adsorption experiments from aqueous solutions containing known amounts of some heavy metallic ions onto the adsorbent were explored in a batch system. The amount of metallic ions adsorbed by LDHs intercalated with EDTA and precursor LDHs were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and atomic absorption spectrometry (AAS). In order to examine the adsorption capacity of LDHs intercalated with chelating agents, the adsorption experiment was investigated under the optimum condition. The data were applied to Langmuir and Freundlich isotherm models. The pseudo-second-order kinetic model was more adequate to describe the kinetic in this case. LDHs intercalated with chelating agents synthesized in this work can be promising adsorbents for heavy metals. It is very significant information from the viewpoint of environmental protection

Chromium isotopic composition of some chondritic meteorites

The Cr isotopic composition of primitive meteorites (acid-residue fractions) was studied. Five chondrites were analyzed in this work [Allende (CV3), Murchison (CM2), Nuevo Mercurio (H5), La Criolla (L6), Qingzhen (EH3)]. Although in most samples, no isotopic anomalies beyond the experimental errors could be detected, an elevated ^Cr/^Cr ratio was found in the acid-soluble fraction from Qingzhen. Moreover, ε^Cr and ε^Cr show an inverse correlation among the meteorites analyzed in this study, and the acid residues have larger ε^Cr and smaller ε^Cr values than do the acid-soluble fractions in Allende and Murchison. The enrichment of ^Cr in the Qingzhen sample suggests that the ^Cr heterogeneity due to stellar nucleosynthesis has remained in enstatite chondrite as well as carbonaceous chondrite. In addition, the inverse correlation of ε^Cr and ε^Cr detected in acid residue samples indicates that the high-temperature condensate contained more exotic ^Cr. It is also suggested that the homogenization of Cr isotopes proceeded with time, and terminated within a relatively short time scale of less than 2-3 Ma

Biosorption of Uranium and Rare Earth Elements Using Biomass of Algae

In order to investigate the behavior of rare earth elements (REEs) and uranium (U) in marine organism, the concentrations of REEs and U in some brown algae samples taken on the coast of Niigata Prefecture were determined. In addition, laboratory model experiment to uptake these elements using living and dried algae (Undaria pinnatifida and Sargassum hemiphyllum) was also carried out to survey the uptake and bioaccumulation mechanism of REEs and U in algae. Consequently, the following matters have been mainly clarified. (1) The order of the concentration of REEs for each organ in Sargassum hemiphyllum is “main branch” > “leaf” > “vesicle,” however for U, the order is “leaf” > “vesicle” > “main branch.” (2) The concentration of REEs in Sargassum hemiphyllum may be strongly affected by suspended solid in seawater. (3) The uptake and/or accumulate mechanism of REEs in brown algae may be different from that of U

Chemical and isotopic compositions in acid residues from three meteorites

Chemical compositions of acid residues obtained from three types of meteorites, 1) Canyon Diablo (IA), 2) Allende (CV3) and 3) Nuevo Mercurio (H5) were determined. Refractory elements were generally enriched in these acid residues. The results match the features that acid residues contain primary condensates from the cooling solar gas as well as extra-solar grains. In the cases of Allende and Canyon Diablo, the contents of a series of refractory siderophile elements such as W, Re, Os, Ir, Mo, Ru and Pt were determined by INAA and AAS. Particularly, in acid residue of Allende, enrichment factors of these elements relative to CI are generally higher (7-20 times/CI), whereas in the cases of W and Mo, they are slightly depleted compared with those of Canyon Diablo. Since both elements would be the first metals to be oxidized under high oxygen fugacity, acid residue of Allende should contain fractions that were produced under oxidizing conditions. In these samples, the isotopic compositions of Ru have been measured by thermal ionization mass spectrometry. So far, in the measurements of acid residue of Allende, all Ru isotope ratios were found to be indistinguishable from terrestrial values within the experimental errors, though errors were large because of small Ru ion beam intensities

Behavior and Distribution of Heavy Metals Including Rare Earth Elements, Thorium, and Uranium in Sludge from Industry Water Treatment Plant and Recovery Method of Metals by Biosurfactants Application

In order to investigate the behavior, distribution, and characteristics of heavy metals including rare earth elements (REEs), thorium (Th), and uranium (U) in sludge, the total and fractional concentrations of these elements in sludge collected from an industry water treatment plant were determined and compared with those in natural soil. In addition, the removal/recovery process of heavy metals (Pb, Cr, and Ni) from the polluted sludge was studied with biosurfactant (saponin and sophorolipid) elution by batch and column experiments to evaluate the efficiency of biosurfactant for the removal of heavy metals. Consequently, the following matters have been largely clarified. (1) Heavy metallic elements in sludge have generally larger concentrations and exist as more unstable fraction than those in natural soil. (2) Nonionic saponin including carboxyl group is more efficient than sophorolipid for the removal of heavy metals in polluted sludge. Saponin has selectivity for the mobilization of heavy metals and mainly reacts with heavy metals in F3 (the fraction bound to carbonates) and F5 (the fraction bound to Fe-Mn oxides). (3) The recovery efficiency of heavy metals (Pb, Ni, and Cr) reached about 90–100% using a precipitation method with alkaline solution