| Weathered coal loses function as fuel after weathering oxidation, but weathered coal contain a large number of reborn humic acid. Humic acid has the function of adsorption, ion exchange and complexation. And humic acid has been widely used in agriculture, industry, environmental protection, especially humic acid of small molecular weight is becoming more and more widely applied in the field of agriculture. Selecting the appropriate catalyst to increase the production rate and lower the molecular weight of humic acid from weathering coal has attracted much attention.In the process of the application in the agricultural sector, part of humic acid will be lost to the water. The water-soluble fulvic acid(FA) as the precursors can generate toxic byproducts THM in the process of the drinking water disinfection, and human health were also threatened immensely. So controlling the FA of drinking water has become a important issue in the process of water treatment.Molybdates as a kind of new catalytic materials, with more advantages such as high surface energy, more active point and high selectivity, have been more and more used in degradation of organic pollutants in recent years. In this paper, we had prepared Co Mo O4 and Ni Mo O4, then they are applied to extract humic acid from weathering coal. We discuss the influence of this two catalysts for the production rate, and the molecular structure of humic acid. We also had prepared Ag2O-Bi2 Mo O6 to degrade the FA of the drinking water, and the degradation kinetics and mechanism were discussed. The results were as follows:(1) The research used Xinjiang weathered coal as raw material, and the production rate of humic acid as the goal. Co Mo O4/Si O2 and Ni Mo O4/Si O2 have better catalytic effect than the samples didn’t load, especially Ni Mo O4/Si O2 has the most obvious catalysis. The results showed that the optimum conditions as follows: the temperature was 80 ℃, coal-to-catalyst ratio was 2 g/0.02 g, and under these conditions, the humic acid content was 57.03%. Methods of FTIR and E4/E6 were used to analyze changes of humic acid structure. The results shows that humic acid with numerous carboxylate radical and hydroxyl groups associates hydroxyl easily and the molecular weight decreases. Degradation of rhodamine B experiment prove that the mechanism of catalyst is prompting to form hydroxylation and unsaturated structures.(2) We synthesize photocatalyst——Ag2O-Bi2 Mo O6 via hydrothermal method. The photocatalyst was characterized by XRD, SEM and UV-Vis spectroscopy. The photocatalytic oxidation of fulvic acid in water was performed over the catalyst. The results show that the surface of pure bismuth molybdate is smooth while on the surface of Ag2O-Bi2 Mo O6 there are some well-distributed small grains. The XRD pattern of Ag2O-Bi2 Mo O6 shows diffraction peaks of Ag2 O. Compared with the pure sample, Ag2O-Bi2 Mo O6 has much higher photocatalytic activity under visible light, and when its doping level is 1.5%, it shows the highest activity. The best catalyst concentration is 0.6 g·L-1. The decrease in p H value of the solvent and initial concentration of fulvic acid will promote the removal of fulvic acid. The degradation process of fulvic acid conforms the first order kinetics, and the fitting equation is y =-0.0195 x. We find that the strong oxidizing hole and ·OH play main roles in the photocatalytic degradation by adding free radical scavenger. A photobacterium phosphoreum toxicity test results show that the toxicity of the 2 h photocatalytic degradation product is reduced by about 90% compared to the un-degraded fulvic acid. |
PDF Full Text Request