# Removal of Sodium Dodecylbenzenesulfonate by Macroporous Adsorbent Resins
## 1 Introduction  
Huge amounts of radioactive liquid wastes (RLWs) are generated during the operation of nuclear power plants. In addition, such RLWs include enormous amounts of various kinds of surfactants used to remove radioactive nuclides during decontamination processes [1; 2; 3]. One of the general methods for treating RLWs is the membrane separation method. Although membrane separation has advantages such as low cost, good separation capacity, and reusability, membrane fouling (the adsorption of organic materials, including surfactants) still limits the versatility of this process [4; 5; 6]. Thus, more convenient separation methods to treat RLWs are urgently required to improve the efficiency of purification processes for RLWs.  
Among the surfactants used for removal of radioactive nuclides generated from decontamination and decommissioning, SDBS is one of the anionic surfactants that are frequently used. Although most of the surfactants containing SDBS in domestic waste water (concentration range: 1-10 mg/L) can be completely removed in liquid-waste treatment facilities, a potential environmental problem of incomplete elimination of SDBS from RLWs, which contain a high concentration of SDBS and radioactive nuclides, still remains [7; 8]. Because of the toxicity of SDBS, water contaminated with thesurfactant including drinking water [9] or RLWs should be purified to discharge clean water to the environment. Although a number of studies have reported the removal of SDBS mixed with metal ions, the removal of SDBS mixed with radioactive nuclides has rarely been studied. Various inorganic materials with high porosity, such as activated carbon [10; 11], zeolite [12], magnetic materials [13], and carbon nanotubes [14] have been used for adsorbing SDBS from aqueous solutions. Porous polymeric resins have many advantages over such porous inorganic materials, for example, low cost, high adsorption capability, high porosity, large surface areas, and easy synthesis and surface modification [15]. Such advantages of MARs have resulted in various applications, including in the biomedical field [16] and for separation [17; 18], catalysis [19; 20], and adsorption [21; 22]. Despite the diverse applications of MARs, the removal of surfactants using the MARs has rarely been reported.  
In this work, two kinds of MARs that did not contain an ionic functional group (sulfonic acid or ammonium salt) were used to adsorb SDBS in aqueous solution and in an imitation of RLWs containing SDBS at high concentration. The MARs were commercial products with the trade names Dianion HP20 and Dianion HP2 MGL, suggesting that they are cost effective. They have different chemical structures, crosslinked polystyrene (PSt) for HP20 and crosslinked poly(methyl methacrylate) (PMMA) for HP2 MGL. The adsorption behavior of SDBS on the MARs was investigated in terms of measuring the effects of adsorption time, initial SDBS concentration, and amount of adsorbents used. The adsorption of SDBS mixed with Cs ions, simulating water-based radioactive waste, was investigated using the MARs as a test of this possible practical application.