Iver W. Duedall

Role of amorphous ferric oxyhydroxide in removal of anthropogenic vanadium from seawater

Adsorption of dissolved vanadium V(V) onto synthetic amorphous ferric oxyhydroxide ((am)Fe2O1,-H2O) was measured using synthetic seawater medium (35 cee). Experiments were conducted at 253C as a function of reaction time, pH, concentration of adsorbent, and concentration of adsorbate. The purposes of the study were to determine the effectiveness of (am) Fe2O3, -H2O in removing dissolved V(V) from seawater, and to estimate the role of (am)Fe2O3,-H2O in sediments in removing vanadium leached from stabilized oil ash blocks placed on the sea floor. Adsorption of V(V) onto (am)Fe2O3-H2O in seawater was rapid and reached a quasi-equilibrium condition within 1 h under laboratory conditions. pH was the major factor influencing adsorption of V(V) by (am) Fe2O3,-H2O. Maximum adsorption occurred at pH 4.6 in the solutions containing total particulate iron (FeT) concentrations of 0.6 × 10−3 and 1.3 × 10−3M. Adsorption of anionic V(V) onto (am)Fe2O2-H2O decreased when pH increased. Significant dissolution of (am)Fe2O3-H2O occurred at pH values < 3.5 and this enhanced the observed decrease in adsorption for low concentrations of FeT. The increased presence of neutral and cationic V(V) :species at pH 3.5 may also be a major factor in reducing the amount of V (V) available for adsorption by (am)Fe2O3-H2O. The effect of pH was, however, overridden by the effect of a relatively high FeT concentration; complete removal of dissolved V (V) was found in both alkaline and acidic solutions when the FeT concentration was 5.6 × 10−3M. Adsorption isotherms of V (V) conformed to a Langmuir shape, suggesting that V (V) adsorption by (am) Fe2O2-H2O is a site-specific reaction. The results of this study indicate that the surface sites of (am)Fe2O3-H2O are heterogeneous. A preliminary model was developed to predict the geochemical fate of anthropogenic V (V) in seawater in the presence of (am) Fe2O2-H2O; the model is applicable for solutions containing FeT in the concentration range 3 × 10-3 to 5.6 × 10−1M and dissolved V (V) in the range 1 × 10-4 to 2 × 10−3M.

Metal release from particulate oil ash in seawater

Abstract Oil ash, the solid residue remaining after the combustion of oil in oil-fired electric power plants, is rich in metals including vanadium (0.54–2.36%) and nickel (0.44–1.33%). Ocean disposal of oil ash may provide an alternative to present landfill practices. This study examined the chemical behavior of particulate oil ash in seawater as a first step towards evaluating the environmental acceptability of oil ash in the sea. In 1:100 oil ash-seawater mixtures (weight:volume), oil ash particles reacted with seawater to produce alkaline or acidic solutions ranging in pH from 3.0 to 9.9. The acidic oil ash No. 3 that produced a leachate of pH 3.0 released 8.8% of the total iron in the ash, 40% of the copper, 70% of the nickel, 94% of the manganese, 35% of the chromium, 68% of the sulfate, but only 1.5% of the vanadium. The alkaline oil ash No. 5 (pH of leachate 9.9) released only 7.6% of the vanadium and 57% of the sulfate. Oil ash No. 1 (pH of leachate 7.9) released 27% of the vanadium and 33% of the sulfate to the seawater. Calculations based on a hypothetical dump of particulate oil ash at sea from a moving barge show that ambient vanadium, nickel, and manganese concentrations in the water column would be exceeded during the first 24 h after the dumping event. However, surface currents and turbulent diffusive processes, not accounted for in this hypothetical dump, would act to further dilute the metals in the water column.

Leaching Characteristics of Lead and Cadmium From Waste-To-Energy Residues in Sea Water

Abstract Laboratory studies were conducted to determine leaching characteristics of waste-to-energy (WTE) residues in sea water to provide initial evaluation on the potential impact of WTE residues on the marine environment. Both loose and stabilized WTE residues were investigated for the leachability of lead (Pb) and cadmium (Cd) in sea water. Results of the study showed that loose WTE fly ash was very reactive in sea water; release of Pb and Cd occurred immediately (<0.5 hr) after the ash came in contact with sea water. Stabilization (treated with Portland cement and other additives), however, significantly reduced leaching of Cd and Pb. While ocean disposal of untreated WTE residues would not be advisable, utilization of stabilized WTE residues for beneficial uses should be investigated.

The partial molal volume of silicic acid in 0.725 M NaCl at 1°C determined by the neutralization of Na2SiO3

Abstract The partial molal volume of silicic acid ( V (Si(OH) 4 ) ) in 0.725 M NaCl at 1°C was calculated from the measured volume change (Δ V n ) due to the neutralization of anhydrous sodium metasilicate with HCl and the V (HCl) and V (NaCl) obtained from the literature. V (Si(OH) 4 ) = 59.0 cm 3 mol − 1 , determined under experimental conditions of pH = 2.2, compares favorably with V (Si(OH) 4 ) = 58.9 cm 3 mol −1 calculated from the measured volume change due to the hydrolysis of the meta-silicate salt at pH = 11 and from the partial molal volume due to electrostriction ( V elect ) of water by charged Si species present in the solution at the high pH. This agreement lends support to a semiempirical model for calculating V elect in developed by Millero (1969). V (NaOH) = − 5.45 cm 3 mol −1 in 0.725 M NaCl needed for this calculation was also determined in this work. The rate of polymerization of Si(OH) 4 at 1°C was monitored to insure that the monomer Si(OH) 4 was the main Si species present during the determination of V (Si(OH) 4 ) by neutralization of the alkali silicate. V (Si(OH) 4 ) determined in this study compares favorably with the value calculated from high pressure solubility measurements.

Possible Use of Ash Residues for the Construction of Artificial Reefs at Sea

Abstract Utilization of ash residues, including coal ash, oil ash, and municipal solid waste combustion ash, for the construction of artificial reefs at sea has been investigated by many researchers throughout the world for nearly 20 years. Both laboratory and field studies have shown that an artificial reef made of stabillized ash-concrete (SAC) has had no adverse effect on the marine environment. Indeed, published studies have shown that fish counts increase around SAC reefs owing to an abundance of colonizing organisms and to protection provided by cavities within the reef structures. However, public and regulatory resistance to the use of SAC for artificial reef construction at sea is still very strong in certain countries due to concern for possible negative environmental impacts, primarily in the area of bioaccumulation of elements or compounds originating from the ash component of SAC. In this paper, technological feasibility of using ash residues for artificial reef construction is presented, base...

Chemical Behaviour of Calcium in Stabilized Oil Ash Reef Blocks After Five Years in the Ocean

Abstract Reef blocks made from stabilized oil ash were taken from the sea after five years in the ocean to examine the chemical behaviour of calcium. Experiments included (1) determination of the calcium leaching rate and a comparison with the rate for unexposed blocks to test the validity of a diffusion model for predicting long term (5 years) leaching rates, (2) determination of the effect of biological cover (shell) on the leaching rate, (3) determination of the leaching rate of the core of exposed reef blocks, (4) determination of the calcium content in ‘ring areas’ - regions of discoloration observed in sectioned exposed reef blocks, and (5) determination of the leachable fraction of the total calcium in exposed reef blocks. Results showed the presence of a pronounced calcium discontinuity zone located 3–7 cm from the outside surface of the reef blocks. Cumulated calcium release rates ranged from 2.81–3.14 μmol cm−2 day−1 for original unexposed reef blocks and the core of exposed (in the ocean for fi...