Influence of Surfactant Concentration and Chain Length on the Absorption of CO2 by Aqueous Surfactant Solutions in the Presence and Absence of Induced Marangoni Effect

Effect of Contaminants on the Gas Holdup and Mixing in Internal Airlift Reactors Equipped with Microbubble Generator

The impact of contaminants on the gas holdup and mixing characteristics encountered in internal airlift reactors was investigated using a 200 L pilot scale unit equipped with a two-phase transonic sparger capable of generating microbubbles. Small dosages of a cationic surfactant (0–50 ppm of sodium dodecyl sulfonate (SDS)) were used to simulate the coalescence-retarding effect encountered in most industrial streams and resulted in the formation of bubbles that varied in size between 280 and 1,900 μm. Gas holdups as high as 0.14 were achieved in the riser under homogeneous flow regime when slowly coalescent systems were aerated at the relatively low superficial velocity of 0.02 ms−1, whereas liquid circulation velocities as high as 1.3 ms−1were achieved in conjunction with rapidly coalescent systems at the same superficial velocity. This excellent hydrodynamic performance represents a 5-fold improvement in the riser gas holdup and up to 8-fold enhancement in the liquid circulation velocity and is expected to yield good mixing and mass transfer performance at low energy dissipation rates.

Combined photochemical and biological processes for the treatment of linear alkylbenzene sulfonate in water

In this study, the effects of photochemical pre-treatment (pilot-plant UV/H2O2 process) of linear alkylbenzene sulfonate (LAS) on its subsequent biological treatment were examined. It was observed that the photochemical pre-treatment of the LAS solution did not increase its biodegradability. Moreover, the effects of acclimated microorganisms on the biodegradability of the LAS solution were also studied. It was observed that the acclimated activated sludge increased the biodegradation of the LAS solution. However, due to the presence of some intermediates in the effluent of the photoreactor, the biodegradability of this effluent was less than the biodegradability of the untreated LAS solution with the same concentration of the LAS in the effluent of the photoreactor.

Biological activity and environmental impact of anionic surfactants

The newest results concerning the biological activity and environmental fate of anionic surfactants are collected and critically evaluated. The chemical and physicochemical parameters related to the biological activity and the field of application are briefly discussed. Examples on the effect of anionic surfactants on the cell membranes, on the activity of enzymes, on the binding to various proteins and to other cell components and on their human toxicity are presented and the possible mode of action is elucidated. The sources of environmental pollution caused by anionic surfactants are listed and the methods developed for their removal from liquid, semiliquid and solid matrices are collected. Both the beneficial and adversary effects of anionic surfactants on the environment are reported and critically discussed. It was concluded that the role of anionic surfactants in the environment is ambiguous: they can cause serous environmental pollution with toxic effect on living organisms; otherwise, they can promote the decomposition and/or removal of other inorganic and organic pollutants from the environment. The relationship between their chemical structure, physicochemical parameters, biological activity and environmental impact is notwell understood. A considerable number of data are needed for the development of new anionic surfactants and for the successful application of the existing ones to reduce the adversary and to promote beneficial effects.