Surfactant Concentration In Water Research Articles

Bioavailability of sediment‐sorbed and aqueous surfactants to Chironomus riparius (midge)

AbstractThe bioavailability of sediment‐sorbed and soluble fractions of three surfactants were compared in egg hatchability and partial life cycle chronic bioassays with the midge Chironomus riparius. The chemicals tested were linear alkyl (dodecyl) benzene sulfonate (LAS), dodecyl trimethyl ammonium chloride (TMAC) and distearyl dimethyl ammonium chloride (DSDMAC). Midge eggs exposed to ranges of surfactant concentrations in water were monitored for hatching success and posthatch survival. No significant reductions in egg hatching were observed at the highest concentrations tested: 18.9 mg/L LAS, 21.5 mg/L DSDMAC and 15.4 mg/L TMAC. Newly hatched larvae were more sensitive than eggs; respective 72‐h LC50 concentrations (48‐h for TMAC) were 2.2, 11.3 and 14.6 mg/L. In partial life cycle chronic bioassays in sediment/water test systems, percentages of winged adults emerging after continuous exposure of larvae and pupae to doses of each surfactant were determined. Exposure concentrations in sediment, interstitial water and overlying water were monitored by 14C liquid scintillation counting. Lowest observed effect concentrations (LOECs) of sediment‐spiked surfactants were 319 to 993 μg/g (dry weight) LAS, 876 to 2,708 μg/g DSDMAC and >3,084 μg/g TMAC (highest concentration tested). Corresponding no observed effect concentrations (NOECs) were 319 μg/g LAS, 876 μg/g DSDMAC and 3,084 μg/g TMAC. The NOECs are approximately 100, 1,000 and 10,000 times greater than respective NOECs of the solubilized materials, and exceed levels of these materials measured in the environment. The results indicated that adsorption onto sediment significantly mitigates surfactant bioavailability to Chironomus.

Wetting and adsorption: I. The structure of adsorbed layer of nonionic surfactants at SiO2/water and SiO2/cyclohexane interface

Based on the adsorption of Triton X-100 on silica/water and silica/cyclohexane interfaces and the adsorption of Triton X-305 on silica/water interface, two adsorption models have been proposed. On silica/cyclohexane interface, the adsorption of Triton X-100 is monomolecular layer. The molecules in the monolayer are presumed to be attached to the silica surface by their EO chain such that their hydrocarbon chain are exposed to the cyclohexane phase. On silica/water interface, the adsorption of Triton X-100 or Triton X-305 is bimolecular layer. The surfactant molecules orientated in the first layer are similar with that on the silica/cyclohexane interface. The molecules in the second layer are postulated to adsorb on those of the first in the opposite orientation, with EO chain directed toward the adsorption medium. The contact angle of quartz-water-cyclohexane (θW) as a function of the concentration of Triton X-100 and Triton X-305 in water has been measured with quartz plate employing the captive drop (cyclohexane) technique. The observed θW (measured through water) rose from < 10° to a maximum of about 120° for Triton X-100 and of about 40° for Triton X-305 as the concentration of surfactant in water increased, and then fell, as the concentration increased further. The results are consistent with the proposed adsorption models.

Chlorine-Release Test for Cavitation-Activity Measurements

A new method is described for measuring the cavitation activity in an ultrasonic cleaning system. The method is based on the sonochemical liberation of chlorine from carbon tetrachloride dissolved in water. The chlorine release rate is found to be rapid and linear with irradiation time. The method is used to measure the effect on chlorine release rate of variables such as power input to the transducer, water height, water temperature, and concentration of surfactant in water. The method is also evaluated against the removal of graphite from alumina-ceramic rings. The result indicates that the chlorine-release rate has a quantitative relationship with cleaning efficiency. A further comparison of the method and an actual soil-removal process indicates that a quantitative relationship exists between the chlorine-release rate and cleaning capability at a given frequency.