Reduction of perchlorate using zero-valent titanium (ZVT) anode: kinetic models.

The kinetics of perchlorate reduction by zero-valent titanium (ZVT) undergoing electrical pitting corrosion was described by interactions of two domains (pit and solution). Two kinetic models were developed based on two possible inhibition mechanisms. A competitive adsorption model was developed based on surface coverage of perchlorate and chloride on bare ZVT, and a Ti(II) consumption model was developed based on Ti(II) oxidation by electrochemically developed chlorine.

Perchlorate reduction during electrochemically induced pitting corrosion of zero-valent titanium (ZVT).

Zero-valent metals and ionic metal species are a popular reagent for the abatement of contaminants in drinking water and groundwater and perchlorate is a contaminant of increasing concern. However, perchlorate degradation using commonly used reductants such as zero-valent metals and soluble reduced metal species is kinetically limited. Titanium in the zero-valent and soluble states has a high thermodynamic potential to reduce perchlorate.

Arsenic stabilization on water treatment residuals by calcium addition.

A common method of removing arsenic from contaminated water is the co-precipitation or sorption of arsenic onto oxy-hydroxides formed by the addition of metal salts. Arsenic co-precipitation produces solids containing high concentrations of arsenic. The elevated arsenic content poses leaching problems requiring expensive disposal in certified hazardous impoundments.

Disinfection and dewatering of wastewater solids by interstitial vapor generation.

Disinfection of wastewater solids (waste activated solids [WAS]) by interstitial vapor generation was investigated. In addition to the magnitude of disinfection, the amount of water removed and cost relative to traditional residuals disinfection processes was also examined. The process of interstitial vapor generation occurs as a result of the rapid heating of liquid in the interstices of the solid-liquid array.

An evaluation of the colloidal stability of metal working fluid.

The effect of calcium on the stability of a commercial MWF is characterized through the experimental determination of the stability ratio, W. Three experimental methods of stability ratio evaluation are investigated. (1) The initial slope of the absorbance versus time curve is used to estimate the rate of coagulation.

Prediction of three-dimensional fractal dimensions using the two-dimensional properties of fractal aggregates.

Fractal dimension analysis using an optical imaging analysis technique is a powerful tool in obtaining morphological information of particulate aggregates formed in coagulation processes. However, as image analysis uses two-dimensional projected images of the aggregates, it is only applicable to one and two-dimensional fractal analyses. In this study, three-dimensional fractal dimensions are estimated from image analysis by characterizing relationships between three-dimensional fractal dimensions (D(3)) and one (D(1)) and two-dimensional fractal dimensions (D(2) and D(pf)).

Adsorption and transport of arsenic(V) in experimental subsurface systems.

The adsorption and transport of As(V) in a heterogeneous, iron oxide-containing soil was investigated in batch and column laboratory experiments. The As(V) adsorbed rapidly to the soil over the first 48 h, but continued to adsorb slowly over the next several weeks, clearly indicating the potential for rate-limited transport. The equilibrium As(V) adsorption isotherm was markedly nonlinear, further indicating the potential for nonideal transport.