A series of core–shell SiO2@MgxSiyOz (SM) composites were synthesized with high efficiency for the adsorption of Rhodamine B (RhB). The composites were characterized by powder X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and nitrogen adsorption–desorption. The influences of different magnesium oxide additions, adsorbent dosage, temperature, contact time and initial RhB concentration on RhB adsorption were investigated, and the optimized adsorption parameters were also obtained. The adsorption data was evaluated using Langmuir and Freundlich models, but high correlation coefficients (R2) confirmed the validity of the Langmuir isotherm, with maximum adsorption capacity of 52.71 mg g−1 at 313 K. The kinetic data fitted a pseudo-second order model well and thermodynamic studies showed that the adsorption process was spontaneous and endothermic. Even after five successive cycles for the adsorption–desorption of RhB, the regenerated powders retained excellent adsorption capacity with more than 99% dye removal and could be utilized as an efficient and low-cost adsorbent for adsorption of RhB dye in wastewater.
