| Adsorption by activated carbon is an effective technology for removing organic pollutants from drinking water. In this paper, we select three kinds of typical organic matters-atrazine, dichloroacetic acid and trichloroacetic acid and study the adsorption characteristics of the organics by two bamboo-made activated carbons and five coal-made activated carbons in both natural water and purity water. On this basis, we can explore the effect of physical and chemical characteristics of activated carbon on the adsorption and competitive adsorption between organics from natural water and target organics. We also use the technology of molecular weight distribution and three dimensional fluorescence spectroscopy to study the removal of natural water organics in different molecular weight and different component and the effect of carbon struction on the removal efficiency. At last, we want to provide useful information and theoretical support for the application of bamboo-made carbons and the selection of carbons.Seven kinds of activated carbon are mainly composed of micropores. Their average pore size are between 2.2-2.6 nm. Their pores have very narrow distribution range which is between 0.4-4.5nm. These activated carbons contain the elements such as C, H, O, N. Because of oxygen atom, there are many functional groups on the surface, like carboxyl, carbonyl and hydroxyl. The surface of seven carbons is alkaline because their p Hpzc are higher than 7. Judging from the physical and chemical structure, two bamboo-made activated carbons have the most developed pore structure and the most abundant functional groups.Three target organics can be well removed by activated carbons and their adsorption isotherms can be well fitted by Freundlich and the modified Freundlich models in purity water. The order of adsorption quantity is atrazine> trichloroacetic acid> dichloroacetic acid. For the same organic matter, the order of adsorption capacity is bamboo-made column carbon>coal-made column carbon > bamboo-made broken carbon > coal-made broken carbon > shenhua1# carbon > shenhua2# carbon >JC carbon. The physical parameters,especially the surface area of micropore, the volume of micropore and the total surface area are the leading factors during the adsorption. The chemical parameters have little effection on the adsorption.The adsorption isotherms of three target organics can be well fitted by Freundlich models in natural water. Compared with the condition of purity water, the adsorption quantity is much lower. The order is that, the target organics were loaded in purity water > the target organics and dissolved organic matter(DOM)were loaded in the nature water at the same time > DOM was loaded first and then the target organic compounds were loaded in the nature water, the order shows that there is competition between DOM and the target organics when they were absorbed. The reason is that DOM with small molecular weight can compete adsorption sites with target organics directly and DOM with large molecular weight can block the pores.The result of molecular weight distribution turns out that small molecule organics can be well removed by activated carbons. For the DOM which molecular weight is between 500-1000 Da, the difference between carbons is caused by micropores and mesoporous. For the DOM which molecular weight is between 100-500 Da, the difference is mainly caused by micropores. The organics which molecular weight is smaller than 100 Da can not be adsorbed easily under low concentration, but they can be removed under high concentration because of enough adsorption sites. The result of three dimensional fluorescence spectroscopy shows that activated carbons have selective when they adsorb different components of DOM. The order of adsorption quantity is microorganism metabolites> humic acid> tyrosine > fulvic acid with ultraviolet region> fulvic acid with visible region> tryptophan. The adsorption capacity of activated carbons is caused by both physical and chemical characteristics. |
PDF Full Text Request