Effect of inorganic ions on the photocatalytic treatment of methylene blue by reduced graphene oxide

In this study, reduced graphene oxide (RGO) was prepared separately by hydrothermal and chemical reduction methods. The catalytic activity of RGO with hydrothermal and the chemical methods was investigated when they were applied in the degradation of methylene blue (MB) under visible light. The results show that the catalytic activity of RGO with the chemical method was negligible, whereas that of RGO with the hydrothermal method was significant but unstable. The addition of 2 mmol L-1 inorganic ions (HCO3-, HPO42-, NO3-, SO42-, Al3+, Mg2+, Na+, Ca2+, and NH4+) and humic acid (HA) into RGO with the hydrothermal method affected the degradation of MB. The photodegradation efficiency of MB was improved by the addition of HCO3- or HPO42-, whereas NO3-, SO42-, Al3+, Mg2+, Na+, Ca2+, and NH4+ inhibited photodegradation of MB. Moreover, the addition of HA was proven to inhibit the degradation of MB by RGO via the hydrothermal method.