Removal of the surfactant sodium dodecylbenzenesulfonate from water by processes based on adsorption/bioadsorption and biodegradation

This study analyzed the bioadsorption/biodegradation kinetics of the surfactant sodium dodecylbenzenesulfonate (SDBS) on commercial activated carbons and on activated carbons prepared in the laboratory by activation of almond shells. The effect of surface oxygen species on these processes was also investigated by using an activated carbon from almond shells oxidized with H2O2 or HNO3. SDBS removal kinetics followed a first-order kinetic model, with rate constants between 1.25×10(-2) h(-1) and 2.14×10(-2) h(-1). The removal rate constants of total organic carbon (TOC) were also determined, obtaining values ranging between 0.51×10(-2) h(-1) and 1.76×10(-2) h(-1). TOC removal rate constants were lower than SDBS removal rate constants, demonstrating that SDBS is also biodegraded during bioadsorption. Both the inorganic carbon concentration and the colony forming units confirm this biodegradation. The amount of SDBS removed from water varies between 109.0 and 232.3 mg SDBS/g of carbon. When SDBS adsorption on activated carbon is conducted in the presence of bacteria, which is the real situation in water treatment plants, a fraction of bacteria are adsorbed on the surface of activated carbon. A part of the SDBS is removed by adsorption (bioadsorption) and other part by biodegradation.