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A quaternary nanocomposite Fe3O4@SiO2@TiO2/graphene oxide (GO) was for the first time successfully synthesized in this work for the repeated use in simultaneous adsorption and photocatalytic degradation of aromatically structured chemical pollutants. The resulting sample was characterized by TEM, XRD, FTIR, TG-DTG, XPS, PL, and VSM. Its photocatalytic activity was evaluated in the photocatalytic degradation of rhodamine B (RhB) under high-pressure mercury lamp irradiation. The results showed that about 63% of RhB was absorbed onto the prepared Fe3O4@SiO2@TiO2/GO nanocomposites by just 30 minute mixing, and after 120 min high-pressure mercury lamp irradiation, about 92.03% of RhB was converted. The photocatalytic degradation followed pseudo first-order reaction with an apparent rate constant of 0.0136 min(-1). Compared with the Fe3O4@SiO2@TiO2 nanoparticles, it exhibits an excellent ability to adsorb aromatic compounds via π-π stacking and a higher photocatalytic activity due to the presence of GO. In addition, the synthesized nanomaterial exhibited good magnetic response and the reusability study suggested that the prepared nanocomposites were stable enough and maintained high degradation rate and catalyst recovery even after five cycles, verifying their potential application in water purification.

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Interactions between alkali metals in catalysts and silicon or aluminum minerals in coal are closely related to gasification reactivity, deactivation, and recovery of alkali catalysts during coal catalytic gasification, and alkali-containing minerals and their transformation behaviors are key issues for understanding these interactions. In this paper, Na-containing mineral transformation behaviors and their influences on the catalytic performance during Na 2 CO 3 -catalyzed CO 2 gasification of highalumina coal were comprehensively investigated by thermogravimetry, inductively coupled plasma, X-ray diffraction, and Fourier transform infrared spectroscopy. Moreover, to have a better understanding of the mineral transformation during catalytic gasification, model compounds, i.e., kaolinite (Al 2 O 3 •2SiO 2 •2H 2 O) and boehmite (AlOOH), the main Al-containing minerals in high-alumina coal, were chosen as model compounds to investigate the mineral transformation behaviors. The results show that Na 2 CO 3 first deactivates to generate inert sodium aluminum silicate (Na 1.55 Al 1.55 Si 0.45 O 4 ) at 700 °C, which contributes to the deactivation of catalysts, and then various kinds of sodium aluminum silicates are formed with increasing temperature and Na 2 CO 3 addition. Among them, sodium aluminum silicate [(Na 2 O) 0.33 NaAlSiO 4 ] has been testified as the most stable mineral during gasification. In addition, Na-containing mineral transformation and its resulting products are helpful to the recovery of Al from the ash of catalytic gasification, and 94% recovery rate can be obtained, which is considered to be a method to extract Al from gasification ash. Model kaolinite and boehmite can well explain the mineral transformation during Na 2 CO 3 -catalyzed CO 2 gasification of high-alumina coal.

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