Sodium dodecylbenzene sulfonate (DBS), an anionic surfactant, is used as an important content of detergent. Its discharge without treatment causes environmental problem and its adsorptive behavior in soils is not fully understood. In this study, the adsorption behavior of DBS of linear carbon chain on volcanic ash soil was investigated before and after removing most of the organic matter from the soil. The soil used in the experiment is highly humic non- allophanic Andisol soil. Non-allophanic Andisol and DBS have negative charge, which helped to observe the negative-negative soil-surfactant interaction. The adsorption isotherm amount was measured at the electrolyte concentration of 100 mmol L-1 NaCl in order to get the smooth adsorption isotherm and to shorten the diffuse double layer. The adsorption amounts were increased by increasing the concentration of DBS in both soils. The soil having organic matter showed the more adsorption compared to the soil after removing most of the organic matter at different pH conditions. It was also observed that adsorption amount was higher at lower pH. These results indicate that organic matter has increased the adsorption of DBS on volcanic ash soil at all pH condition.
Key words: Sodium dodecylbenzene sulfonate (DBS), adsorption isotherm, anionic surfactant, electrolyte, volcanic ash soil.
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