Remediation of phenanthrene contaminated soils by nonionic–anionic surfactant washing coupled with activated carbon adsorption

Batch experiments were conducted to investigate the performance of nonionic–anionic mixed surfactants and their recovery through activated carbon. The solubilization capabilities of mixed surfactants toward phenanthrene (PHE) were reduced by addition of anionic surfactant to the mixed systems. Results showed that sorption of Triton X-100 (TX100) onto soil decreased with increasing mass fraction of sodium dodecyl sulfate (SDS) in the mixed surfactant solutions. Soil contaminated with PHE at 200 mg/kg was washed with different surfactant concentrations at various mass ratios of nonionic–anionic mixed surfactant. Experiments with low-concentrations of mixed surfactants revealed that removal efficiencies for PHE-contaminated soil close to the individual higher nonionic surfactant concentration can be achieved. Overall performance considering both soil washing and surfactant recovery steps is apposite when an TX100:SDS mass ratio of 8:2 at 3 g/L is used.