Preparation of Sulfhydryl Functionalized MCM-48 and Its Adsorption Performance for Cr(VI) in Water

In this study, we modify the Mobil Composition of Matter No. 48 (MCM-48) silica material (MCM-48-SH) using Mercapto. The preparation conditions of MCM-48-SH are then explored, its structural characteristics are analyzed using characterization, and it is used to adsorb Cr(VI) from wastewater. A series of experiments are then designed to adsorb Cr(VI) in experimental water, and the influence of solution environment changes (such as time, temperature, pH, and coexisting ions) on the adsorption effect was explored. The experimental data showed that the MCM-48-SH material not only retained the basic structure of MCM-48 but also successfully grafted the functional group -SH. The adsorption of Cr(VI) on MCM-48-SH followed the Langmuir isotherm model and the kinetic adsorption was fitted with a pseudo-second-order kinetic model. Under these conditions, the adsorption capacity of MCM-48-SH (17.9 mg/g) on Cr(VI) was much larger than that of unmodified MCM-48 (4.0 mg/g) and amino-modified MCM-48-NH2 (0.5 mg/g). The adsorption effect was the most obvious when the pH = 2 but the adsorption effect was not good under alkaline conditions. Other competitive ions in the solution had an influence on the adsorption effect, among which anions had a great influence. Within 3 d, when the concentration of Cr(VI) was 80 mg/L, the maximum adsorption capacity reached 17.9 mg/g and the maximum removal rate reached 93.45%. In the comparative adsorption experiment, the adsorption effect of MCM-48-SH (17.9 mg/g) on Cr(VI) was notably better than that of the other two common adsorbents: coconut shell activated carbon (9.2 mg/g) and bentonite (1.2 mg/g). In summary, MCM-48-SH can be used to effectively eliminate Cr(VI) in waste water.