Pore size and surface area control of MgO nanostructures using a surfactant-templated hydrothermal process: High adsorption capability to azo dyes

Dioctylsulfosuccinate sodium surfactant (AOT) was selected as a structure-directing agent to prepare mesoporous MgO adsorbent by a hydrothermal method. The anionic AOT surfactant combines with Mg(OH)2 crystallites to form AOT·Mg(OH)2 micelle colloids by hydrogen bonding and electrostatic attraction to template the mesopores with diameter of 10–20 nm in MgO nanoplates The whole process is composed of three stages: nucleation, orientation growth, and porecreating. The results demonstrated that the presence of AOT surfactant was essential to produce the mesopores and to adjust the structural parameters of the nanoplates. Because of their higher specific surface area and porous structure, the MgO materials exhibit a satisfactory adsorptive property to three typical azo dye pollutants, Congo red (471–588 mg/g), Methyl orange (∼370 mg/g) and Sudan III (∼180 mg/g), and good performance for decolorization of low-concentration dyes. The highly adsorption capacities of the adsorbents are ascribed to their mesoporous structures which can provide more interaction sites, facilitate the mass diffusion in pores and help the dye molecules to contact the adsorptive sites more easily. The present work provided an alternative approach for preparation of inorganic adsorbent with controlled porous structures and high adsorption ability for hazardous dyes.