Louis Kravetz

Influence of hydrophobe type and extent of branching on environmental response factors of nonionic surfactants

A number of ethoxylated nonionic surfactants differing in hydrophobe branching and chainlengths have been evaluated for environmental responses. Screening biodegradation tests show that those nonionics having more than one methyl group per hydrophobe degrade considerably slower than those having less extensive branching. Continuous flow-through activated sludge tests, simulating actual waste treatment, show that the more highly branched nonionics biodegrade more slowly and less extensively than those with less hydrophobe branching. In addition, treated effluents originating from influents containing the more highly branched nonionics tend to be more surface active and more toxic to aquatic species than those originating from influents containing surfactants with less hydrophobe branching. Under conditions simulating plant stress, such as high surfactant concentrations in the influent or low temperature, biodegradation of the highly branched nonionics was considerably less extensive, while biodegradation of the linear nonionics was not affected to any measurable degree compared to more normal operating conditions.

Analysis of nonionic surfactants in bench-scale biotreater samples

The effluents and activated sludges used in benchscale biotreater units have been analyzed for nonionic alcohol ethoxylates and their residues. Separate bench-scale units were fed linear alcohol ethoxylates (AE), highly branched and branched nonylphenol ethoxylates. Effluents and sludges were first pretreated by a foam sublation technique to provide a gross separation of surfactants from the environmental matrix. This step was followed by normal-phase high-performance liquid chromatography (HPLC) with either fluorescence detection (FD) or evaporative light-scattering detection (ESLD). The AEs were derivatized with phenylisocyanate and analyzed by normal-phase HPLC coupled with FD. At extremely low surfactant levels, pretreatment of large sample volumes resulted in interferences on derivatization. Hence, a normal-phase HPLC method with ELSD was developed. Although some interferences do appear using ELSD, this method appears to be a more viable alternative to derivatization/FD for very low levels of AE. HPLC with FD and ELSD detection methods are more quantitative and provide information on the polyoxyethylene chain than is possible with traditional methods like cobalt-thiocyanate active substance.

Aerobic biodegradability of surfactants at low concentrations using an automated pressure transducer system

Abstract We have developed a simple and reliable automated pressure transducer system (APTS) to evaluate the ready and ultimate aerobic biodegradability of surfactants in 28 days at low concentrations (5 mg C/L) using modifications of existing CO 2 evolution assays (Sturm & Gledhill). Pressure transducers (PT) are fitted to Gledhill-type flasks containing Sturm minerals solution, dilute (50 mg/L) unacclimated activated sludge microbial seed and test compound. PT monitor microbial respiration through oxygen consumption from the headspace and CO 2 from metabolism is absorbed in a 1M KOH solution within the flask. Results with nonionic ethoxylate (AE-7) and anionic sulfate (AS) surfactants prepared from linear or 2-alkyl branched C 14−15 alcohol moieties show that sewage bacteria readily consumed 02 (70–140% ThO 2 ) and degraded these compounds to C02 (65–75% ThCO 2 ) in 12 days at 25C. However, when a more branched alcohol ethoxylate (NPE-9) was tested in the APTS, only 50% of both the ThO 2 was consumed and ThCO 2 was produced. Glucose and benzoic acid were biodegraded to CO 2 similarly to the AE-7 and AS surfactants. Comparison of alcohol ethoxylate degradation data in the APTS with those published from traditional Sturm test methods demonstrated that the C0 2 recovery results were the same for readily metabolized compounds. Our experience with the APTS indicate that the method is reliable, less cumbersome and requires less manipulation than the Sturm and Gledhill assays. Furthermore, the method can be adapted to screen the ready biodegradability of volatile, insoluble and other organic compounds for which radiolabelled material is not available to study microbial degradation.

A New Catalyst System for Cross-Linking Cotton Cellulose with Formaldehyde:

A dual catalyst system containing magnesium and fluoborate ions facilitates the cross-linking of cotton cellulose with formaldehyde. Compared with previous formaldehyde cross-linking processes, the dual catalyst system permits operating at lower temperatures, shorter curing times, and lower concentrations of formaldehyde to produce high and nonvariable wash-wear characteristics which are durable in home and commercial launderings. In addition, this dual catalyst system may be used to impart durable-press properties to cotton fabric by using either pre-cure, partial cure, or post- cure techniques. The magnesium cation seems to be unique in the dual catalyst system, since other divalent cations, e.g., barium and zinc, do not act synergistically with fluoborate. The role of fluoborate is discussed and data are shown which indicate that boron trifluoride is the active species which accelerates the cross-linking reaction in the presence of magnesium. 14Carbon tracer studies reveal that, under equivalent processing conditions, more formaldehyde is bound to cellulose by the dual catalyst system than by a single catalyst (magnesium chloride) system.