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Amino-functionalized mesoporous silica MCM-41 materials have been prepared to develop efficient adsorbents of Cr(VI) in wastewater, using silica fume as silica source. Functionalization with amino groups has been carried out by using grafting method. The materials have been characterized by means of X-ray diffraction (XRD), nitrogen (N2) adsorption-desorption, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Adsorption potential of the material for Cr(VI) removal from aqueous solution was investigated by varying experimental conditions such as pH, initial metal concentration, and contact time. The equilibrium data were analyzed using the Langmuir and Freundlich isotherm by linear regression analysis, and the results show that the adsorption equilibrium data obeyed the Langmuir model. In addition, the kinetics analysis revealed that the overall adsorption process was successfully fitted with the pseudo-second-order kinetic model.

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The formation of ZrB2 particles in Al–Si alloys not only improves the properties of the Al–Si alloy but also helps remove B from Si for the preparation of solar-grade Si. A thermodynamic study was performed to identify the mechanism of ZrB2 formation in Al–Si alloys. The precipitated B-bearing particles, i.e., ZrB x , were determined to be ZrB2 via electron probe microanalysis. The composition of the Al–Si alloy, which could form stable ZrB2 particles, was determined by measuring and calculating the equilibrium concentrations of Zr and B and the solubility products of ZrB2 in a Si-saturated Al–Si alloy at different temperatures. Thereafter, the segregation coefficients of B between solid Si crystals and the Si-saturated Al–Si melt with and without Zr addition were estimated thermodynamically. The mechanism whereby the B removal from Si was enhanced with Zr addition was as follows: the Zr not only reduced the concentration of B in the molten Al–Si but also significantly reduced the segregation coefficient of B between the solid Si and Si-saturated Al–Si melt.

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