Relationship of structure to properties of some anionic surfactants as collectors in the flotation process. 2. Effect of phenyl group

Surface and thermodynamic properties of four synthetic anionic surfactants are studied. The properties of these surfactants are correlated with their flotation performance to upgrade a petroleum coke sample to minimize its im purities. The surfactants are isomers for dodecylbenzenesulfonate of the sa me molecular weight, but the benzene ring is attached to different carbon a toms along the dodecyl chain. The results show that the position of benzene ring, attached to the carbon chain, affects their surface and thermodynami c properties. The values of critical micelle concentration (cmc), minimum a rea per molecule (A(min)), effectiveness (Pi(cmc)) and efficiency (pC(20)), to reduce surface tension of water, are decreased with changing the positi on of benzene ring from carbon atom number 3 to 5. Increasing temperature i s accompanied by an increase in each of cmc, minimum area per molecule (A(m in)), Gibbs energy of micellization (Delta G(mic)(o)), and adsorption (Delt a G(ad)(o)). Meanwhile, the values of surface tension (gamma(cmc)) at cmc, surface excess concentration (Gamma(max)), and effectiveness (Pi(cmc)) to r educe surface tension of water are decreased. There is a good relationship between the structure of a surfactant and its efficiency as a collector. Ch anging the position of the phenyl group along the alkyl chain of a surfacta nt toward its central carbon atom (6 phi C12) improves its efficiency as a collector.