A new water-soluble silicon phthalocyanine that catalyzes the photodegradation of pollutant dyes

The removal of color arising from water-soluble dyes in wastewaters is necessary to counter the threat to health. Because of the difficulty in elimination of these dyes by conventional methods, their photodegradation using photosensitizers such as phthalocyanines (Pcs) has been employed recently. When compared to peripherally substituted derivatives, silicon Pcs are reported to be more biocompatible with low toxicity. Thus a new silicon Pc substituted with two quaternized dimethylamino phenoxy units (compound 1) and its quaternized derivative (compound 2) were synthesized to test its photocatalytic ability employing the dyes methylene blue (MB), eosin B (EB), erythrosine (ERB), sulforhodamine B (SRB), and brilliant blue FCF (BRB), some of whose absorption bands overlap with those of Pcs. The overlapped absorption bands were split using first-order derivative UV-vis spectra. The photodegradation rates of BRB, MB, and ERB were 41%, 38%, and 29%, respectively, under 30-s short time irradiation in the presence of compound 2. The plots of the natural logarithm of the concentrations of dyes versus time fit the first-order reaction model. According to the experimental data, compound 2 could be used as a photocatalyst due to singlet oxygen generation for photodegradation of pollutant dyes MB, ERB, and BRB with higher photodegradation rates.