A new tannin-based coagulant and flocculant agent has been tested on the removal of sodium dodecyl benzene sulfonate (SDBS), a dangerous and pollutant anionic surfactant. It is called SilvaFLOC and consists of a chemical modified tannin extract from Schinopsis balansae, commonly known as Quebracho. A fully detailed study has been carried out. SilvaFLOC has been revealed as an efficient product in anionic surfactant removal. Around 80% of SDBS removal has been achieved with SilvaFLOC doses of 300 mg L-1. pH has a negative influence on surfactant removal, while the higher initial surfactant concentration the higher q capacity is obtained. Theoretical data adjustment has been carried out according to three different models: Fowler-Frumkin-Guggenheim (FFG), Gu and Zhu (G-Z) and Freundlich (F). Adjustment parameters have been obtained with r(2) levels above 0.96 in all cases. In order to study the interaction between pH and initial surfactant concentration, a design of experiments procedure has been carried out. Optimum pH has been found in 5.8. (C) 2009 Elsevier B.V. All rights reserved.