Uptake of arsenic(V) using iron and magnesium functionalized highly ordered mesoporous MCM-41 (Fe/Mg-MCM-41) as an...

Mesoporous silica (MCM-41) is widely used as a supporting material due to its large specific surface area and good stability, but it cannot remove heavy metals due to the lack of adsorption active sites. In this study, the MCM-41 (a mesoporous SiO₂ material) decorated with iron and magnesium oxide (Fe/Mg-MCM-41) was found to be an excellent adsorbent to remove arsenic(V) from water. FTIR, BET, TEM-EDS, XRD, XPS, etc. were applied for characterization analysis. Adsorption isotherms were fitted well by the Langmuir model and the experimental maximum adsorption capacity of Fe/Mg₄-MCM-41 (magnesium accounts for 4%) was 71.53 mg/g at pH = 3. Thermodynamics analysis suggested exothermic nature of adsorption behavior. Kinetic process was well described by the pseudo-second-order model and adsorption rate was controlled by intraparticle diffusion and film diffusion. Moreover, the adsorption behavior of As(V) onto Fe/Mg₄-MCM-41 was investigated under different reaction conditions, such as pH, temperature, Mg-doping and competing ions. The results showed that loading a certain amount of magnesium can significantly improve arsenic removal efficiency. Additionally, Fe/Mg₄-MCM-41 exhibits high arsenic(V) removal in the wide pH range of 3-10. The Fe/Mg₄-MCM-41 can be regenerated and used after four consecutive cycles. The high arsenic(V) sorption capacity, wide range of pH applications, ability to regenerate, and reusability of Fe/Mg₄-MCM-41 confirmed that this adsorbent is promising for treating As-contaminated wastewater.