Preparation of optimized porous honeycomb magnesium silica gels and their adsorption properties for weak acid red

Many magnesium brine resources, including huge magnesium chloride reserves, exist in China. However, development and deep processing of magnesium chloride were once considered to have low value-add, and have been neglected for a long time. In order to study and develop new adsorbents' economic, high adsorption capacity and renewable ability, sodium silicate and magnesium chloride were taken as raw materials, and a series of optimized porous honeycomb magnesium silica gels were synthesized by the sol-gel method. The optimum calcination conditions of the magnesium silica gel were studied as well. Structural characterization and property determination of the samples were obtained through a series of observations and analysis, including TG analysis, infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), specific surface and porosity analysis and SEM. The behaviour of magnesium silica gel adsorbing weak acid red in an aqueous solution was studied subsequently. After calcinating for 4 h at 500, the magnesium silica gel with a ratio of magnesium to silicon (n(Mg2+)n(SO32-)) of 31 had the best adsorption capacity for weak acid red. The adsorption of weak acid red conformed to the Langmuir isothermal adsorption model and secondary dynamic equation. At 25, dosage 0.5 g/L, and initial ρ(weak acid red) 200 mg/L, the saturated adsorption quantity of weak acid red by magnesium silica gel reached 199.51 mg/g, representing a removal rate of 99.34%. After five replications of regeneration, the magnesium silica gel still had a high adsorption capacity of 192.12 mg/g, and the removal rate was 95.60%. The results showed that optimized porous honeycomb magnesium silica gel synthesized by sodium silicate and magnesium chloride has high adsorption capacity and renewable ability to weak acid red. It is an optimized low cost and efficient adsorption material. © 2015, Editorial Board, Research of Environmental Sciences. All right reserved.