Kinetic Analysis of the Ozonation Process of the Surfactant LAS Considering the Simultaneous Foaming Effect

Abstract

Advanced oxidation processes (AOP) are able to degrade pollutants into harmless substances. To demonstrate the successful application of AOP to real, polluted effluents, ozonation has been applied for the removal of linear alkylbenzene sulfonates (LAS), a surfactant mixture commonly used in detergent formulation. LAS can be identified in a wide range of concentrations, i.e., in domestic wastewater or in the raw effluent of detergent‐processing plants. The strongly tensoactive nature of LAS results in a foaming effect that eventually discourages AOP application, especially in the case of ozonation. The primary goal of this research is to analyze the LAS ozonation kinetics, considering the simultaneous effect of foam formation, by the development of a semiempirical model that is mainly based on the foaming phenomenon. Along with foaming, the proposed model also considers LAS removal by ozonation and the inverse phenomenon of LAS formation by redissolution of LAS. To the best of our knowledge, such a finding has not been previously reported. The proposed foaming model has been developed within various pH and LAS concentration values, primarily examining the initial pH value of the effluent due to its significant effect on foaming. The developed model adequately predicts the LAS concentration profiles measured in the liquid during ozonation. Moreover, this approach makes it possible to quantify the incidence of foaming and LAS redissolution during ozonation comparatively, leading to being able to propose the most desirable operating conditions for LAS removal.

Surfactant-Assisted Ozonolysis of Alkenes in Water: Mitigation of Frothing Using Coolade as a Low-Foaming Surfactant

“…It should be noted that thin layer chromatography (TLC) and 1 H NMR analyses of the crude mixtures from SDS, DBSA, and CTAB-assisted ozonolysis indicated high conversions of the alkene 1 , and thus, we concluded that the yields were lost from spillage of the foam during ozonolysis. These observations of foaming were consistent with the previous studies on the degradation of the electrically charged surfactants by ozone in wastewater treatment, in which foaming during the ozone purging presented a great challenge during the operations. , …”

“…Despite the complete conversion of alkene 1 to the aldehyde 1a as analyzed by 1 H NMR of the crude mixture, a low yield was obtained after purification, evidently resulting from the spillage as a result of the foaming during the ozonolysis. 23 Reducing the amount of SDS from 5 to 2 and 1 wt % did not diminish the foaming. Low yields of the aldehyde 1a (40 and 39%) were still obtained due to spillage (entries 2 and 3) and incomplete conversion of the alkene 1 (entry 3).…”

“…After the ozone purging was stopped, the reaction mixture was treated with dimethyl sulfide to give 4-chlorobenzaldehyde ( 1a ) as a white solid in 53% yield after purification (Table , entry 1). Despite the complete conversion of alkene 1 to the aldehyde 1a as analyzed by 1 H NMR of the crude mixture, a low yield was obtained after purification, evidently resulting from the spillage as a result of the foaming during the ozonolysis . Reducing the amount of SDS from 5 to 2 and 1 wt % did not diminish the foaming.…”

“…These observations of foaming were consistent with the previous studies on the degradation of the electrically charged surfactants by ozone in wastewater treatment, in which foaming during the ozone purging presented a great challenge during the operations. 23,24 We next turned our attention to nonionic surfactants because they produce less foaming than the electrically charged surfactants (i.e., SDS, DBSA, and CTAB). 25 Several Foaming level of surfactants was classified by the amount of time required by foam to fill up a reaction vessel (a 100 mL round-bottom flask) after application of ozone stream; +++ foam filled up within 10 min, ++ foam filled up within 1 h, + foam filled up within 2 h, and − foam was not observed during the ozonolysis.…”

Oxidizing efficiency analysis of an ozonation process to degrade the dye rhodamine 6G

“…In our case, the experiments were always performed with the same fluid dynamic conditions, those determined by the nature of the experimental device and the gas flow used in each case. A potential change in the physical properties of the solution, influencing the K L a parameter as in the case of surfactants, has not been considered in this case.…”