Study On Degradation Of Nitrate And Humic Acid Simultaneously By Metal Modified TiO₂

Formic acid is generally used as a hole scavenger in the removal of nitrate using photocatalytic method.In natural waters, humic acid is a kind of poorly biodegradable traditional organic pollutants, but also safe drinking water priority control pollutants. With the nitrate concerntration is highly increased, using humic acid which already exists in water instead of the fomic acid as hole scavenger, photocatalytic degradation of nitrate and humic acid becomes a worthy study of safe drinking water technology.In this paper, different content of metal ions doped TiO2 catalysts were prepared by photo reduction method. Metal ion species included Zinc (Zn)、chromium (Cr)、 Iron (Fe)、copper (Cu)、Argentum (Ag).Study the removal effect of different metal /TiO2 on the nitrate (NO3--N) and humic acid,and chose out the better screening doped metal species and load capacity. The chosen metal/TiO2 then is used to make XRD, XRF, SEM characterization. Finally, explore the coexistence of nitrates and humic acid removal in water, then examine the factors of humic acid concentration, pH, catalyst dosage, pass into the gas and other factors on both the removal efficiency. The results are described below.1.In the photocatalytic degradation of nitrate experiment, the initial concentration of nitrate was 100mg/L, the amount of catalyst 1g/L, the amount of formic acid is 0.04mol/L, with 125W UV lamp as the light source, Ag/TiO2 degradation rate is the highest in 150min of the five metals. While in the three doping Ag/TiO2, the 1wt% Ag/TiO2 ratio has the highest conversion of nitrate (97.2%) and the selectivity for nitrogen is 75.8%.2.In the humic acid degradation separate experiments, the initial concentration of humic acid is 10mg/L, the amount of catalyst is 1g/L, with 125W UV lamp as a light source,in addition to Cr/TiO2 four metal-doped TiO2 for humic acid degradation rate are higher than 80% in 30 min. However, based on the fact that the best metal nitrate removal is 1Ag/TiO2, taking into account the need for nitrate and humic acid degradation simultaneously, so eventually screened the 1Ag/TiO2 as the co-catalyst for nitrate and humic acid degradation.3.By the results of characterization of 1Ag/TiO2, Ag-doped TiO2 did not change the particle size and crystal form of TiO2, but XRD results showed that the Ag-doped into the TiO2 in indeed, XRF characterization results indicate that the actual doping is consistent with the theoretical.4.1n total degradation experiments,we found that when the initial concentration of nitrate was 100mg/L, the UV light source is 125W,with the initial concentration of humic acid increased,the nitrate removal firstly increased and then decreased,the optimum value of the initial concentration of humic acid was 60mg/L;With the Ag/TiO2 amount increased from 0.5g/L to 2.0g/L, the nitrate removal firstly increased and then decreased,the Ag/TiO2 optimum dosage was 1.0g/L;With the increasing pH,nitrate removal increased then reduced,the optimum value is 8;Compared with nitrogen and air condition,when there was no gas pass in,we can get high nitrate removal.Under the optimum value of the above conditions,after 150min reaction,the nitrate removal rate was 38.2%,nitrogen selectivity is 40.6%.