Effects of fulvic acids and electrolytes on colloidal stability and photocatalysis of nano-TiO2 for atrazine removal

The colloidal stability and photocatalysis of nano-TiO 2 particles were investigated in the presence of fulvic acids (FA) and electrolytes (NaNO 3 , Na 2 SO 4 , Na 3 PO 4 ) at different pH. Results showed that increasing FA concentration, the absolute value of zeta potential of nano-TiO 2 increased and particle size decreased at all pH which promoted the colloidal stability of nano-TiO 2 . Particle size of nano-TiO 2 was larger with the coexistence of FA and electrolytes than with FA only as the concentration of electrolytes was greater than or equal to 0.01 mol/L. The largest particle size occurred in the presence of Na 3 PO 4 , followed by Na 2 SO 4 and NaNO 3 . Particle size of nano-TiO 2 decreased with higher pH and stability further increased in the presence of FA and/or electrolytes. Nano-TiO 2 stabilization was enhanced by increasing FA concentration when the solution pH was 7.0. However, the removal efficiency of atrazine by nano-TiO 2 decreased with the increase in FA concentration. Adding electrolytes (0.01 mol/L), atrazine removal by nano-TiO 2 further decreased, albeit slightly. The inhibitory effect of electrolytes on nano-TiO 2 removal of atrazine was highest for Na 3 PO 4 , followed by Na 2 SO 4 , and NaNO 3 , which were consistent with the results of colloidal stability of nano-TiO 2 . These findings help to better understand the mechanisms and correlation between colloidal stability and photocatalysis of nano-TiO 2 in the presence of FA and electrolytes.