Synthesis And Adsorption Behavior Of Magnesium Silicate Gels

A series of novel magnesium silicate gels were synthesized by a mild hydrothermal route using Na₂SiO₃·9H₂O and MgCl₂·6H₂O as raw material. The optimum synthesis conditions were assured by varying the parameters of Mg/Si molar ratio, material mixed mode, calcinations'temperature, hydrothermal time, hydrothermal temperature and adding pore reagent. The samples were characterized by BET, SEM, XRD, and FT-IR. The adsorption behavior of magnesium silicate gels were studied by adsorption of the two kinds of dyes (Basic Brilliant Green and Basic Flavine O) and Ca²⁺. The effects of the functions of initial concentration of solution, adsorbent dosage, contact time, initial pH, and ionic strength on the adsorption performance were studied.From the physical characterization and the adsorption of basic brilliant green on the magnesium silicate gels, we can concluded that the main factors affecting the adsorption properties were Mg/Si molar ratio and calcinations'temperature, the secondary factors were material mixed mode, hydrothermal time and hydrothermal temperature and adding pore reagent could not improve the adsorption properties significantly. The magnesium silicate gels with different Mg/Si molar ratios have formed the 1:1 structural unit layers. They were layered Mg-Si compounds with micro porous or mesoporous, and the solubility of magnesium in distilled water was very low.The adsorption behavior of magnesium silicate gels for basic brilliant green was studied and the results indicated that 1:1 C-Mg-Si gel-700 behaved the best adsorbent performance. In the range of 298 to 348 K, the equilibrium dates were found to be well represented by the Langmuir isotherm equation. The best fit of the kinetic result was achieved by a pseudo second-order equation, with the maximum adsorption capacity up to 598.95 mg·g^-1. The optimum adsorption effect was achieved using the following conditions: adsorption with initial concentration of 300 mg·L^-1 at 45℃for 200 min for 0.5 mg·L^-11:1 C-Mg-Si gel-700. The concentration gradient of the solution was the main driving force of the rapid adsorption process. In the initial pH range of 3 to 11, theremoval rate for basic brilliant green remained unchanged. In the range of high pH values, Adsorption and reaction of basic brilliant green and NaOH were both contribute to the removal of basic brilliant green. The adsorption behavior of magnesium silicate gels for basic flavine O was studied and the results indicated that 1:1 Mg-Si gel behaved the best adsorbent performance. In the range of 298 to 348 K, the equilibrium dates were found to be well represented by the Langmuir isotherm equation. The best fit of the kinetic result was achieved by a pseudo second-order equation, with the maximum adsorption capacity up to 149.25mg·g^-1. The optimum adsorption effect was achieved using the following conditions: adsorption with initial concentration of 300 mg·L^-1 at 55℃for 200 min by 2.0g·L^-1 1:1 Mg-Si gel. The concentration gradient of the solution was the main driving force of the rapid adsorption process. In the initial pH range of 3 to 11, the removal rate for basic flaine O remained unchanged.The adsorption behavior of magnesium silicate gels for Ca²⁺ was studied and the results indicated that 1:4 180-Mg-Si gel behaved the best adsorbent performance. In the range of 298 to 348 K, the equilibrium dates were found to be well represented by the Langmuir isotherm equation. The best fit of the kinetic result was achieved by a pseudo second-order equation, with the maximum adsorption capacity up to 50.00mg·g^-1. The optimum adsorption effect was achieved using the following conditions: adsorption with initial concentration of 50 mg·L^-1 at 55℃for 150 min by 1.5g·L^-1 1:4 180-Mg-Si gel. The nature of electric charge on the surface of adsorbent was the main driving force of the rapid adsorption process. In the initial pH range of 2 to 11, the removal rate for Ca²⁺ remained steeply rising trends.