Study On Foam Separation Of Surfactant From Its Aqueous Solution

People use foam separation to separate surfactants from solution because of adsorption. In this paper, removal of Cetyltrimethylammonium bromide(CTAB), sodium dodecyl benzene sulfonate(SDBS), sodium lauryl sulfate(SDS) and Cetyl pyridinium chloride(CPC) by foam fractionation from simulated aqueous solutions was studied, especially the effects of initial concentration of surfactant,air flow rate, liquid height, the content of ethanol, ionic strength and solution pH value were investigated. Various influential operating conditions for surfactants were selected by a series of single-factor test. And each surfactant obtained its combination of the best operating conditions through orthogonal test.By using the orthogonal experiment and comparison of variables in each factor, the experimental results showed the best combination of operating conditions of each surfactant. The appropriate separation conditions for CTAB were determined by comparing the influence factors. The recovery ratio can reach 95.99%, and the corresponding operating conditions were: initial concentration of CTAB 0.7mmol/L, the air flow rate 0.25m3/h, liquid height 33.9cm, the content of ethanol 4mL/500mL. The recovery ratio of SDBS can reach 97.42%, and the corresponding operating conditions were: initial concentration of SDBS 1.05mmol/L, the air flow rate 0.20 m3/h, solution pH value 9, ionic strength 0.4mmol/L. The recovery ratio of SDS can reach 85.40%, and the corresponding operating conditions were: initial concentration of SDS 1.0mmol/L, the air flow rate 0.25 m3/h, the content of ethanol 5mL/500mL and liquid height 20.5cm. The recovery ratio of CPC can reach 98.99%, and the corresponding operating conditions were: initial concentration of CPC 0.5mmol/L, the air flow rate 0.15 m3/h, liquid height 23.83cm and ionic strength 5.0mmol/L.Then a mathematical model of the foam fractionation of surfactants was constructed. And some parameters were assumed reasonably. A series of differential equations were established by material balance and solved by means of matlab software. Effects of parameters on enrichment were predicted by the model.