Alan J. Rubin

Studies on the toxicity of ammonia, nitrate and their mixtures to guppy fry

Abstract Using guppy fry as the test fish the individual and joint toxicities of ammonia and nitrate were estimated in static tests at constant pH and temperature. The 72-h lc 50 values were 199 and 1.26 mg 1−1 −N for potassium nitrate and free ammonia, respectively. The toxicities of mixtures of the two were additive except at very low ammonia to nitrate ratios. Watsons equation, a disinfection law relating toxicant concentration to survival, was applicable to both toxicants. The applicability of Chicks law and other kinetic models to fish toxicity was also evaluated.

Foam Fractionation and Precipitate Flotation of Zinc(II)

Abstract The hydrolytic behavior of a metal can be related to its removal by foaming. In this study the effect of pH and ionic strength on the foam separation of 0.1 mM zinc (II) was investigated using different concentrations of sodium lauryl sulfate as the collector. At low pH Zn2+ ion was removed by foam fractionation while above pH 8 Zn(OH)2(s) was removed by precipitate flotation. The results demonstrate that precipitate flotation is a more efficient removal process than the foam separation of soluble metal species.

Inactivation of Naegleria gruberi cysts by chlorine dioxide

Abstract Investigations were carried out to determine the kinetics of chlorine dioxide inactivation of Naegleria gruberi cysts and the influence of pH from 5 to 9, temperature from 5 to 30°C, cyst age from 3 to 12 days, and cyst clumping. Inactivation was characterized by an initial concave downward shoulder followed by an essentially linear portion but the process obeyed Watsons Law. At 25°C and pH 7 the mean concentration time product for 99% inactivation was 5.5 mg·min l−1. These products varied inversely with temperature and pH.

Determination of Soluble Species and Precipitates of Aluminum Phosphate

Abstract The interaction between aluminum(III) and orthophosphate salts was studied. The investigation involved the direct measurement of phosphate remaining in solution after precipitation with different applied concentrations of aluminum(III) at varying pH, the establishment of the pH limits of precipitation as determined from light-scattering measurements taken at varying P to Al ratios, and alkametric potentiometric titrations with subsequent computer analysis using the program SCOGS. Several soluble species and their formation constants were determined. Solid phases identified included AIP04(s), Al3(OH)3(PO4)2(s). and Na3Al5H6(P04)8(S).

Effect of coagulation and restabilization on the microflotation of illite

Abstract Investigated was the application of the foam separation technique of microflotation to the clarification of illite suspensions. Aluminum sulfate served as the coagulant and anionic and cationic collector surfactants were examined using a batch flotation system. Restabilization of the clay by hydrolyzed aluminum species prevented its removal by the cationic collector. The anionic collector was most effective in the pH ranges of aluminum hydroxide precipitation.

Effect of Complexation on the Adsorption of Cadmium by Activated Carbon

Abstract The adsorption of Cd2+ in the absence and presence of two chelating agents was examined as a function of pH. Fits of the data to the Freundlich and Langmuir equations were compared as were results with Zn and Pb using four different activated carbons. In general, adsorption increased with increasing pH and was not extensive, particularly for Cd. At low cadmium to carbon ratios, EDTA appeared to enhance adsorption. With more realistic loadings, when competition for surface sites is greatest, the presence of EDTA is shown to be detrimental to the process. 1,10-Phenanthroline, the second chelating agent studied, was more effective for promoting the removal of Cd. The uncomplexed Cd and Cd-EDTA systems were best described by the simple Langmuir adsorption isotherm. The adsorption of 1,10-phenanthroline and its Cd complex were modeled using a modified form of the Langmuir equation.

Coagulation and Flotation of Colloidal Titanium Dioxide

Abstract The foam separation of dispersed and coagulated titanium dioxide was investigated using anionic and cationic collector surfactants in a batch flotation system. Aluminum sulfate was used as the coagulating agent, and ethanol served as the frother. Removal was studied as a function of pH with coagulant and collector concentrations as parameters.

Coagulation of Escherichia Coli by neutral salts

Abstract An experimental procedure for the systematic study of microbial aggregation was developed and the coagulation of Escherichia coli by neutral salts was investigated. Changes in turbidity as estimated by absorbance measurements during settling were used as the criterion for coagulation. The effects of several parameters on the procedure and results are discussed. It was found that E. coli are coagulated by hydrogen ions and polyvalent cations at concentrations considerably lower than that of simple univalent cations. The effectiveness of divalent cations was related to their ionic radii. In general, the organisms followed the Schulze-Hardy rule for coagulation being similar in this respect to hydrophobic colloids.

Comparison of chlorine and chlorine dioxide for the inactivation of an amoebic cyst

Abstract Studied was the inactivation of the cysts of the amoeba Naegleria gruberi using chlorine at pH 7 and chlorine dioxide at pH 5, 7 and 9. The results indicate that many of the findings with other organisms are also true for the cysts except that ClO2 was somewhat more effective than chlorine. In general, the cysts are much more resistant to disinfection than bacteria or poliovirus.

Determination of Monomeric and Polynuclear Aluminum(III) Species and Hydrolysis Constants

Abstract Aqueous reactions of aluminum(III) were investigated in acidic aluminum solutions at fixed ionic strength and below the pH of precipitation. Computer analysis of potentiometric data for three concentrations (0.1, 0.5, and 1 mM Al) indicated that the experimental results could be explained by assuming only two principal hydrolyzed species, AlOH2+ and Al8(OH)4+ 20. No other combination of aluminum complexes appeared to fit the data as did these species. The equilibrium constant for the monohydroxy ion was very close to values determined by other methods. The refined values of the formation constants for ∗pK 1 and pβ8,20 were 5.55 and 68.7, respectively, at an ionic strength of 0.15, and 5.11 and 64.1, respectively, at zero ionic strength.