Adsorption Behavior and Treatment of Mixed Surfactant Systems with lonic and Nonionic Adsorbents

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The adsorption isotherms of ionic and nonionic surfactants and their mixed systems onto ionic and nonionic adsorbents were measured in aqueous solution at 25ﾟC.The ionic adsorbents used were Amberlite IRA35, IRA94 and copolymer of 4-vinylpyridine, and their modified types which introduced alkyl groups on the adsorbents. The nonionic adsorbents used were activated carbon and synthetic adsorbents.The adsorption affinities of the ionic adsorbents for sodium dodecylbenzenesulfonate (NaDBS) increased with an increase in the length of alkyl groups in adsorbents. On the other hand, the adsorption affinities for nonionic surfactants decrease with increases in both of the length of alkyl groups in the adsorbents and oxyethylene units in the adsorbates.The adsorption isotherms of NaDBS from aqueous solution onto ionic and nonionic adsorbents were measured in the presence of nonionic surfactants at 25ﾟC.The adsorption affinities of the ionic adsorbents for NaDBS in ionic surfactants decreased with increases in the ratio of nonionic surfactant to NaDBS,in comparison to the pure NaDBS solution. In same cases, the NaDBS was displaced by the nonionic surfactants in the region of higher surfactant concentration. The adsorption affinities of the nonionoc adsorbents for NaDBS increased by addition of nonionc surfactants, but decreased with increases in the ratio of nonionic surfactant to NaDBS,in comparison to the pure NaDBS solution. From the above results, the adsorption mechanism was discussed to gain the basic information about the treatment of wastewaters containing mixeddetergents.