Adsorption properties of dodecylsulfate-intercalated layered double hydroxide for various dyes in water

• LDHs-SDS has a hydrophobic surface and great affinity toward organic dyes.
• LDHs-SDS effectively remove anionic, cationic and nonionic dyes from wastewater.
• The treatment of LDHs-SDS to an actual dye wastewater proved to be favorable.

Organic dyes are an important class of pollutants in wastewater, and it is necessary to find a broad-spectrum adsorbent that can effectively remove different kinds of organic dyes. Through the organic modification of layered double hydroxides (LDHs), the surface properties of the LDHs change from hydrophilic to hydrophobic, resulting in a greater affinity for organic pollutants. Dodecylsulfate-intercalated layered double hydroxide (LDHs-SDS) was prepared with a Mg/Al molar ratio of 2:1 using a co-precipitation method, and was characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The synthesized LDHs-SDS was used as an adsorbent to remove anionic (direct blue G-RB (DB), reactive yellow 4GL (RY), acid red GR (AR)), cationic (basic blue (BB)) and nonionic dyes (disperse red 3B (DR)) from aqueous solution. The sorption was found to be independent of pH from 5 to 10. The maximum removal capacities for DB, RY, AR, DR and BB were 707.76, 392.88, 137.33, 249.24 and 165.11 mg/g, respectively, at 298 K. The adsorption isotherm for AR fitted the Freundlich model well, and data for the other dyes fitted the Langmuir model. The sorption kinetics of all five dyes were well described by the pseudo-second-order model. After treating actual dye wastewater with LDHs-SDS, the results indicate that this could be a potentially effective adsorbent for dye effluent treatment.

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