An innovative approach to recycle boron waste by mesoporous silica production and its application in methylene blue removal

The study shows an innovative method for boron waste treatment through synthesizing mesoporous silica (MCM-41) from it. At the initial stage of the process, magnesium was extracted from the waste by HCl solution and the silica source was leached by sodium hydroxide solution from the residue. Afterwards, n-hexadecyltrimethyl ammonium bromide (CTAB) was employed as the template. XRF investigated the influence of HCl/boron waste ratio, reaction time and temperature on preparing silica source. XRD results showed the compositions of boron waste and the acid leaching residue. Four typical characteristic peaks of MCM-41 were also appeared in the XRD results. The rod shape and 2D hexagonal pore structure of synthesized MCM-41 were determined by SEM and TEM. And it possessed a high BET surface area of 1035.534 m2/g and a large average pore diameter of 2.969 nm according to the N2 physisorption results. FT-IR result indicated calcination is an effective way to remove the template. These properties suggested synthesized MCM-41 has a wide range of applications. The adsorption capacity for methylene blue (MB) on BW-MCM-41 was explored by adsorption kinetics and isotherm models fitting as well as thermodynamic study. The effect of MB solution's pH and the adsorbent dose was studied to determine the optimal adsorption conditions.