Figure 5 shows the removal ratio of Rh.B with selleck increasing loading amount of absorbent under visible-light irradiation recorded at 270 min. For the G/M-CdS, the photodegradation ratio of Rh.B keep increasing from 4 to BTSA1 manufacturer 20 mg, after which it
keeps constant; for CdS MPs, the photodegradation ratio of Rh.B gets to maximum at 30 mg. This is consistent with the result of adsorption-desorption equilibrium experiment, and the suitable loading amount of the G/M-CdS composites should be 20 mg in this work. Figure 4 Removal ratio of G/M-CdS and pure CdS MPs with increasing stirring time under visible-light irradiation. The loading amount of both materials is 20 mg. Figure 5 Removal ratio of G/M-CdS and pure CdS MPs with increasing loading amount under visible-light irradiation. The adsorption characteristics of the G/M-CdS composites are displayed check details in Figure 6. It can be seen that, after stirring the mixture of the G/M-CdS composites and Rh.B aqueous solution (Figure 6, left) under visible-light irradiation for 270 min, the supernatant turned nearly colorless (Figure 6, right). This proved that the G/M-CdS composites possessed the properties of adsorption capacity and photodegradation. We would like to attribute the high efficient photodegradation activity to the
electron transfer from CdS to graphene. As shown in Figure 7, CdS can be excited by UV light to generate electrons and holes. Then, the photogenerated electrons transfer to graphene while holes are left behind in CdS since the conduction band of CdS is more negative. This electron transfer route reduces the possibility of recombination of electron-hole pairs and prolongs the lifetime of charge carriers. In other words, the transfer of photoexcited electrons from CdS to graphene Y-27632 chemical structure facilitates the charge separation, producing more –OH responsible for photodegradation of Rh.B. Previous reports on graphene-CdS
composites as the adsorbent for the extraction of organic pollutants were mainly focused on nanoscaled CdS particles. Herein, the adsorption performance and photocatalytic activity of the large-sized CdS/G composite with approximately 0.64 μm CdS particles were investigated, and the results exhibited that the current composites possess comparable purification ability of waste water with that of nanoscaled CdS/graphene composites. The accurate decision of size effect of large CdS particles needs further investigation, which is a subject of our future research. Figure 6 Rh.B solution (0.01 mg/mL, left) before and after separation of G/M-CdS adsorbent after photodegradation (right). Figure 7 Illustration of charge separation and transfer in G/M-CdS system. Conclusions In summary, we have successfully prepared G/M-CdS composites via an effective solvothermal method. Their ability of extraction of dye from aqueous solution was examined using Rh.B as adsorbate.