Research On The Combined Action Of Surfactant Mixture And Flocculants For Black Carbon Removal

To coal-fired kilns, as the incomplete combustion of carbon-based fuels, a greatdeal of black smoke (BS) was emitted, which is mainly combined by black carbon(BC),and it always suspends in air. What’s more, as the surface of BC is covered by oilyorganic compound, it could absorb heavy metals and toxic substance much easier. Ifhuman body touch this thing in a long period, they may get respiratory system diseases,such as: bronchitis, emphysema and so on. In term of the gas purification of coal-firedfurnace flue gas, the dedust efficiency of cyclone separator is too low and could notremove BC. Electric precipitation and bag-type dedust have a higher dedust efficiency,however, to black smoke pollution which is formed by superfine and surfacehydrophobicity black carbon particle, they are useless. In this study, through addingsuitable additives into the adsorption solution, wet dust removal could get higherremoval efficiency for black carbon. Surfactant in adsorption solution can change thecombinative condition between water and BC, thus BC is able to be wetted sufficientlywhen it contacts with adsorption solution. Besides, flocculant is also used in adsorptionsolution, it improves the aggregation of black carbon. Therefore, black carbon would beeasier precipitated to the bottom of the solution, and the adsorption solution could bereused.In the experiments, nonionic surfactant lauryl polyoxyethylene (9) ether (AEO-9)was used as the main surfactant. It was blended with cation surfactant cetyltrimethylammonium bromide (CTAB), anion surfactant sodium dodecyl benzene sulfonate (SDBS)and nonionic surfactant polyoxyethylene (10) nonyl phenyl ether (TX-10), respectively.The best mole ratio of the mixed surfactant solution which owned the lowest surfacetension was investigated. Atfer that, in order to get better surface activity andcoagulation property,different flocculants were added. In the process: firstly, The criticalmicelle concentration and surface tensions of surfactant mixture AEO-9-CTAB,AEO-9-SDBS and AEO-9-TX-10were investigated, respectively. In order to analysis thenature and the strength of the interaction between two surfactant molecules in the mixedmicelle, the value of p parameter which is the molecular interaction parameter was used.Secondly, the influence of different flocculants polyacrylamide(PAM) andpolyaluminium chloride (PAC) to surfactant mixture solution were also studied. Finally, the sediment of BC in absoption solution by wetting method was simulated, in order tochoose the best flocculant and the optimal concentration, flocculating efficiency ofdifferent flocculants and zeta potential of black carbon surface was measured.Experimental results showed that when AEO-9was blended with TX-10, andconcentration of AEO-9,TX-10was0.05mmol/L,0.09mmol/L respectively, theinteraction between the two surfactants was positive effect and the lowest surface tensionof the surfactant mixture solutiton was36.75mN/m, besides, the influence of flocculantaddition can be ignored. However, the addition of the two different flocculants all coludnot get a better sediment result. Nevertheless, when AEO-9was blended with SDBS, andthe concentration of AEO-9, SDBS was0.07mmol/L, O.5mmol/L respectively, theinteration between the two surfactant was slight,and the lowest surface tension of thesurfactant mixture solutiton was37.05mN/m. The existent of AEO-9in surfactantmixture reduced the influence of temperature and flocculants to the absorbtion solution’surface tension. In the BC sediment experiment, when the flocculant was PAC and theconcentration was300mg/L, the flocculating efficiency of BC could reach to94.5%.According to the zeta potential of BC surface’ investigation, the improvement offlocculating efficiency related to the existent of SDBS.