Study On The Adsorptive Capacity And Mechanism Of Ultrafine Coal Powders

As a kind of important physicochemistry method, adsorption process has irreplaceable actions in the advanced treatment of water and wastewater. The technical key of adsorption lies in that adsorbent should have good adsorption capacity.In this research, the coal, which is cheap and abundant, was crushed by high energy ball milling, and ultrafine coal powders, 1-10 μm, were acquired, which could be used as adsorbent. Then, by bottle technical test, the influence of coal powders with different sizes and different ball mill conditions on its adsorptive capacity were systematically studied, including the adsorbance and the adsorption rate, to phenol, aniline and Ni2+ in aqueous media, as well as the influence of temperature and pH on their adsorptive capacities. It was expected that the cheap ultrafine coal powder was a kind of high quality adsorptive material.The results showed that, at 25℃, the equilibria adsorbance to phenol, aniline and Ni2+ were 53.49mg/g, 39.05mg/g, 6.45mg/g, respectively. And the adsorption isotherms could be expressed by Freundlich isotherms.It was also shown that the adsorbance, on the coal powders, which had been milled for 0.5h, to phenol, aniline and Ni2+ were 26.12mg/g, 28.86mg/g, 2.92mg/g, respectively, which was about 1.5 times of the same grade non-milling, and was about 3 times of the coal powders with mm diameter.The adsorbance on ultrafine coal powders to phenol decreased with increase of pH, and the adsorbance to aniline increased with increase of pH. The adsorbance on ultrafine coal powders to phenol and Ni2+ decreased with increase of temperature, and the effect of the temperature on aniline was not important.The intraparticle effective diffusion coefficient was between 10-12 and 10-13.In the exploratory parts of the theory, the new model, describing the adsorption rate of ultrafine coal powders, was put forward based on mass transfer theory and was confirmed by the experiments, i.e.The model pointed out that the adsorption rate was linear to the concentration of the solution. When the size of adsorbent powders was small enough, intrapartical diffusion resistance can be neglected, and the adsorption rate was determined by external diffusion, and the rate was quick. While the size of adsorbent powders was big enough, the adsorption rate was mainly controled by the resistance of intrapartical diffusion, and the rate was slow.The experimental result revealed that the adsorption rate of the ultrafine coal powders, 1000nm-0.1mm,was determined both by external and intrapartical diffusion.The ultrafine coal powder was an adsorbent with low cost and high quality. It could be used to remove the phenol in aqueous system.