Degradation kinetics of sodium alginate via sono-Fenton, photo-Fenton and sono-photo-Fenton methods in the presence of TiO2 nanoparticles

Sono-photo-Fenton, sono-Fenton and photo-Fenton methods combined with heterogeneous TiO 2 nanoparticles are adopted to investigate the degradation of sodium alginate (NaAlg), and the kinetics mechanism is also explored. Experimental results suggest that the reaction order of NaAlg degradation ( n ) is 0.51 and the extent of photocatalytic degradation can increase with the loading of TiO 2 nanoparticles. Meanwhile, as the catalyst concentration increases from 0.05 to 0.5 gL −1 , the degradation rate constant ( k ) is decreased. In addition, the structure of degraded NaAlg is characterized by Fourier transform infrared (FT-IR), 1 H NMR spectroscopy, and X-ray diffraction analyses. The FT-IR and 1 H NMR spectra results indicate that the C2-C3 bond in the structure of NaAlg is broken and intra-molecular esters are formed during the degradation process due to the strong oxidization of the Fenton system. In general, the sono-photo-Fenton process with TiO 2 nanoparticles could provide an efficient way to degrade the NaAlg to low-molecular-weight.