Efficient and inexpensive preparation of mesoporous silica microspheres and their highly selective adsorption-cycling performance for Ga(III) in acidic solutions

In this paper, efficient, economical and environmentally friendly mesoporous silica microspheres (MSMs) were prepared for the first time by reversed-phase suspension-dispersion method using water glass and acetic acid as raw materials. MSMs had excellent sphericity, with particle size concentrated at 100 µm, specific surface area of 207.90 m 2 /g and pore volume of 0.47 cm 3 /g. Adsorption equilibrium of Ga(III) by MSMs was reached in 30 min on 30 ppm GaCl 3 with dosage of 2 g/L and pH = 3, conforming to the pseudo-second-order kinetic model. The adsorption isotherm showed that the adsorption of Ga(III) by MSMs is endothermic process with saturation adsorption of 83.47 mg/g at 328 K. The K d of MSMs for Ga(III) was above 8000 in three multivariate systems of zinc ore leaching residues, fly ash and e-waste, showing excellent selectivity. The desorption equilibrium of 78.44 % was reached at 2 mol/L H 2 SO 4 for 120 min, and the adsorption rate of Ga(III) on MSMs was still exceeded 90 % after five adsorption–desorption cycles, showing that MSMs have excellent cycling performance. The fixed-bed column experiments showed the efficient separation and enrichment performance of MSMs for Ga(III) in simulated leachate. The adsorption process in MSMs is synergistic interaction is between physical adsorption and ion-exchange, with ion-exchange being the main mechanism. This provides a new approach to address the issues of poor adsorption capacity and slow adsorption–desorption rate faced by adsorbents for the highly selective recover of Ga(III) from zinc ore leaching residues, fly ash and e-waste, which is potentially promising for application.