Abstract
The photocatalytic degradation (PCD) of methylene blue (MB) in aqueous suspensions of nano-sized TiO2 particles containing
high concentrations of NaCl, MgCl2, and CaCl2 was studied. The rates of PCD and adsorption of ions were monitored by
measuring the total organic carbon (TOC) and using inductively coupled plasma-atomic emission spectrometry, respectively. The
results showed that the removal rate decreased with increasing concentrations of NaCl, MgCl2, and CaCl2. The trend for the
differences in the removal rates in MgCl2 and CaCl2 aqueous suspensions inverted as the salt concentration increased, which
revealed that the influence of Ca2+ and Mg2+ is related to the ion concentration. In orthogonal experiments, the hindering effect
occurred as follows in descending order: NaCl, CaCl2, and MgCl2. The rate decreased markedly under certain ratios of salt
concentrations, and the mechanisms were explored.