Mechanism And Application Of Treatment Of Composite Wastewater Containing Heavy Metal And Dye With Foam Separation Method

Foam separation is a new surfactant-based method which utilizes physical absorption of the foam and water interface to remove contaminants in form of table-polymer. Adsorption mechanism and application of foam separation to remove Cd2+and methylene blue (MB) were studied in this paper. During the whole experimental study, sodium dodecyl sulfate (SDS) was selected as the effervescing agent and a continuous foam flotation device was adopted to separate pollutants. The mechanism of action between surfactant and contaminant were systemically investigated. The condition of separation process was optimized to decrease effluent concentrations of Cd2+, MB and SDS. Moreover, spectral characteristics of cadmium-methylene blue containing composite wastewater and foam properties of SDS were preliminary studied.Firstly, the current situation and harm of heavy metals and organic matters were summarized, the application prospect and existing problem of the technique of foam separation in the industrial wastewater treatment were introduced, and the purpose and content of this research were also proposed. Next, foam properties of surfactant and spectral characteristics of various wastewater with different water qualities were investigated. Finally, the single Cd2+-containing or MB-containing wastewater and the Cd2+-MB complex wastewater were treated by foam separation. The results showed that, the spectral curve trend almost did not change except of a sudden increase occurring at200nm while adding Cd(NO3)2·4H2O into solution. Though some change appeared in adsorption peak, it’s particularly slight. The presence of dye MB will inhibit the improvement of foam properties, on the other hand, the addition of Cd2+can enhance the foam properties. The effect on foam properties of improvement is greater than the inhibition strength. In single foam separation process, the best removal efficiency of Cd2+was more than98.6%while99.6%for MB removal, respectively. In synchronous process, foam separation based on SDS was proved to be simple and efficient for simultaneous removal of Cd2+and MB. The highest removal efficiencies of Cd2+and MB could reach to99.0%and99.7%under appropriate operating conditions, respectively, which indicated that there was no significant interrelation between Cd2+and MB compared with single removal of Cd2+/MB. The solution preparation and foam separation operation were both conducted at room temperature rapidly. The study results demonstrated that both single Cd2+-containing or MB-containing wastewater and cadmium-methylene blue containing composite wastewater were quickly and efficiently purified with foam separation. The interaction between SDS and Cd2+/MB was detected by UV-visible spectroscopy method to reveal the feasibility of simultaneous interaction between Cd2+/MB and surfactant on microcosmic level.In this paper, key issues including process optimization of Cd2+and MB containing wastewater with foam separation, process and adsorption mechanism between SDS and Cd2+/MB were investigated and discussed. This study provided foundation for practical industrial application and popularization of foam separation to treat textile wastewater or printing and dyeing wastewater. It also provided the prospects development and application value for the purification of heavy metal-dye composite wastewater.