Simultaneous Determination of Cr, As, Se, and Other Trace Metal Elements in Seawater by ICP-MS with Hybrid Simultaneous Preconcentration Combining Iron Hydroxide Coprecipitation and Solid Phase Extraction Using Chelating Resin

In the present study, ICP-MS with a new hybrid simultaneous preconcentration combining solid phase extraction using chelating resin and iron hydroxide coprecipitation in one batch at a single pH adjustment (pH 6.0) were developed for multielement determination of trace metal ions in seawater. In multielement determination, the present method makes it possible to determine Cr(III), As(V), Se (IV), and other 14 trace metal elements (Ti, V, Co, Ni, Cu, Zn, Zr, Ge, Cd, Sb, Sn, W, Pb, and U) in seawater. Moreover, for speciation analyses of Cr, As, and Se, the pH dependence on recovery for the different chemical forms of Cr, As, and Se was investigated. In speciation analyses, Cr, As, and Se were determined as the total of Cr (III) and a part of Cr (VI), total of As (III) and As (V), and Se(IV), respectively. Determination of total of Se and Cr(VI) remains as future task to improve. Nevertheless, the present method would have possibility to develop as the analytical method to determine comprehensively most metal elements in all standard and guideline values in quality standard in environmental water in Japan, that is, most toxic metal elements in environmental water.

Evaluation of the Applicability of Concrete Sludge for the Removal of Cu, Pb, and Zn from Contaminated Aqueous Solutions

In this study, the possibility of using concrete-sludge recycling as an immobilizer, including dried sludge (DS), precipitated calcium carbonate (PCC), and calcite-coated particles (CCP), was evaluated for the remediation of Cu-, Pb-, and Zn-contaminated aqueous solutions. Experimental variables characterizing immobilization, including reaction time, initial solution pH, and immobilizer dosage, were selected. After DS was applied, 98.3% of Cu, 99.9% of Pb, and 95.2% of Zn were removed via metal-hydroxide coprecipitation onto the surface of DS, which increased in pH within the shortened contact time. On the contrary, PCC and CCP removed metals (above 99.9% removal) via the formation of metal carbonates, which was highly dependent on both the pH and the carbonates released from the immobilizers. The acidic solution pH contributed to the dissolution of calcite (leading to an increase in carbonates in solution), thus enhancing the removal of metals. An increase in PCC and CCP dosage (liquid to solid ratio of 1000 to 100) was effective in removing Cu with an increasing final pH and number of carbonates in solution. Our results show that concrete sludge can be recycled to reduce environmental loads, including alkaline wastewater discharge, waste disposal, CO2 emissions, and metal-contaminated aqueous solutions.

Effects of Microwave Processing on the Properties of Nickel Oxide/Zirconia/Ceria Composites

The effect of a microwave-assisted hydrothermal (MWH) treatment on the structural, thermal, and electrical properties of NiO/ZrO2:8 mol%Y2O3(YSZ)/CeO2 (60/20/20 wt.%) composite was investigated. Powders were synthesized by a hydroxide coprecipitation-impregnation technique, in which Ni and Ce oxides were coprecipitaed in a suspension containing YSZ. Simultaneous thermogravimetry and differential thermal analysis revealed that MWH treatment promotes the crystallization of coprecipitated phases. X-ray diffraction analysis was used for phase identification and the calculated lattice parameters indicated the formation of YSZ:CeO2 solid solution during sintering. Impedance spectroscopy measurements showed that the electrical properties of the composite samples were not significantly affected by the MHW.