sonocatalytic degradation of humic acid by n-doped tio2 nano-particle in aqueous solution

Background: un-doped and n-doped tio2 nano-particles with different nitrogen contents were successfully synthesized by a simple sol–gel method, and were characterized by x-ray diffraction, field emission scanning electron microscopy, energy dispersive x-ray analysis and uv–visible diffuse reflectance spectra techniques. then enhancement of sonocatalytic degradation of humic acid by un-doped and n-doped tio2 nano-particles in aqueous environment was investigated. the effects of various parameters such as initial concentration of humic acid, n-doping, and the degradation kinetics were investigated. results: the results of characterization techniques affirmed that the synthesis of un-doped and n-doped tio2 nano-particles was successful. degradation of humic acid by using different nano-particles obeyed the first-order kinetic. among various nano-particles, n-doped tio2 with molar doping ratio of 6 % and band gap of 2.92 ev, exhibited the highest sonocatalytic degradation with an apparent-first-order rate constant of 1.56×10-2 min?1. conclusions: the high degradation rate was associated with the lower band gap energy and well-formed anatase phase. the addition of nano-catalysts could enhance the degradation efficiency of humic acid as well as n-doped tio2 with a molar ratio of 6 %n/ti was found the best nano-catalyst among the investigated catalysts. the sonocatalytic degradation with nitrogen doped semiconductors could be a suitable oxidation process for removal of refractory pollutants such as humic acid from aqueous solution.