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The objective of this research was to assess the mechanism and effectiveness of the zerovalent iron (ZVI) to remediate the Cr(VI) contaminated water. The mechanism of Cr(VI) reduction by ZVI was evaluated by characterising surface properties and chemical compositions of Fe and Cr products using SEM-EDS, XRD and XPS analyses. The effectiveness of ZVI in Cr(VI) reduction was assessed by the luminescent bacteria (Photobacterium Phosphoreum). The Cr(VI) was reduced to Cr(III), when the reactive Fe° was oxidised to Fe(II,III), showing the presence of Fe2O3, (Fe-Cr)2O3 and FeOOH. The SEM-EDS analysis showed that ZVI with a higher reducing capacity was more subject to changes of surface and morphological properties due to ionisation of ZVI. The Cr and Fe in precipitates subsisted exclusively in the Cr(III) or Fe(III) states with the respective forms of Cr(OH)3 or Cr2O3 and FeOOH or Fe2O3. Electrons produced from ZVI oxidation reduced Cr(VI) to Cr(III), thus resultantly Cr(III) precipitated or co-precipitated with Fe(III) to form Fe(III)-Cr(III) hydroxide or Fe(III)-Cr(III) oxyhydroxide. Toxicity of water reacted with ZVI was significantly lower than that of the untreated water. [ABSTRACT FROM AUTHOR]

Crops grown in calcareous Montana soils with Olsen-P concentrations above critical levels often show responses to phosphorus (P) fertilizers. Objectives of this experiment were to (i) investigate the effects of P fertilization and soil incubation time on soil inorganic P fractions (P[sub i]) and Olsen-P concentrations, and (ii) determine the relationship between each Pi fraction and Olsen-P in P-responsive calcareous soils. Six soils (Ap horizon) were collected from P-responsive locations in Montana based on previous field and greenhouse trials. Each soil was fertilized with 0, 11, 22, and 33 mg P kg[sup -1]-soil and incubated at 20°C for up to 12 weeks. Soils collected after 1, 4, 8, and 12 weeks of incubation were analyzed for Olsen-P, and inorganic P was fractionated into Resin-P, Water-P, NaHCO[sub 3]-P (bic-P), NaOH-P, and HC1-P. Relative distributions of each Pi fraction followed the order of HC1-P > NaOH-P > Resin-P > bic-P > Water-P, with NaOH-P and HC1-P representing greater than 75% of the total P[sub i]. In general, Resin-P, Water-P, bic-P, their summation (Avail-P), and Olsen-P were significantly correlated with the amount of P added, while NaOH-P and HC1-P were not. Compared to the other P[sub i] fractions, Resin-P was more highly correlated with the amount of P added and increased the most following P fertilization. Olsen-P was significantly correlated with Resin-P at most incubation times, yet, in general, was not significantly correlated with bic-P, NaOH-P, or HC1-P. During the incubation, Resin-P decreased the most of the three available fractions, yet Olsen-P was relatively constant. Combined results suggest that available Pi fractions, especially the Resin-P fraction, may be better indicators than Olsen-P at predicting P availability and P responses in calcareous soils. [ABSTRACT FROM AUTHOR]

A highly chromate-selective biosorbent with high adsorption capacity was found by examining the chromate adsorption capacities of 48 species of red, brown, or green marine algae sampled from the east coast of Korea. As a result of screening, a red marine alga showed excellent adsorption characteristics. It was identified as Pachymeniopsis sp. The timing of the sampling of Pachymeniopsis sp. did not affect the adsorption capacity of the alga but the optimum period for mass collection was April–May. The alga also showed high selectivity for chromate and its adsorption capacity for other heavy metal ions such as cadmium and manganese was relatively low. An investigation of the adsorption isotherm of Pachymeniopsis sp. as a dried powder for chromate adsorption at 25 °C showed Langmuir-type dependence. The maximum chromate adsorption capacity of the selected alga was about 225 mg/g. The desorption of adsorbed chromate from Pachymeniopsis sp. was done by treating samples with 1 N NaOH. It was confirmed that ion exchange type adsorption was observed with anion exchangers but not with cation exchangers. Therefore it is believed that the chromate adsorption is based on the anionic exchange of Pachymeniopsis sp. [ABSTRACT FROM AUTHOR]

A high-chromate-selective biosorbent with high adsorption capacity was sought by examining the chromate adsorption capacities of 48 species of red, brown, or green marine algae sampled from the east coast of Korea. Screening showed a red marine alga to have the most excellent adsorption characteristics among them, and it was identified as Pachymeniopsis sp. The period at which Pachymeniopsis sp. was sampled did not affect the adsorption capacity of the alga, but the optimum period for mass collection was April to May. The alga also showed high selectivity for chromate since its adsorption capacity for other heavy metal ions such as cadmium and manganese ions was relatively low. An investigation of the adsorption isotherm of dried powder of Pachymeniopsis sp. for chromate adsorption at 25 °C showed a Langmuir-type dependence. The maximum chromate adsorption capacity of the selected alga was about 225 mg/g. Desorption of the adsorbed chromate from Pachymeniopsis sp. was done by treating the sample with 1 N NaOH. It was confirmed that ion exchange type adsorption was observed with an anion exchanger but not with a cation exchanger. It is therefore believed that the chromate adsorption is based on anionic exchange of Pachymeniopsis sp. [ABSTRACT FROM AUTHOR]