Study On Adsorption Characteristics Of Typical Antibiotics In Water Body Of Power Plant

Many antibiotics have been produced and unreasonably used or abused in China. As antibiotics have long function and metabolism time and they’re difficult to be effectively degraded in the natural environment, once released into the environment, they will put a serious threat to human health and ecological safety, and now they have become one of the most important pollutants in the aquatic environment. Adsorption is one of the important methods for treating antibiotics in water, and selection of adsorption materials, optimization of their interaction conditions, and exploration of adsorption mechanism have become research hotspots.Fly ash is formed of the minerals contained in coal-fired particles through a series of changes, and it has special physical and chemical properties, such as large surface area, high surface energy, and multiple active sites. Coal is the main source of energy in China, and fly ash, as a kind of industrial solid wastes in coal-fired power plant, its annual production is large. It has become imperative to achieve its comprehensive utilization, improve its recycling rate, thereby reducing its storage volume in ash yards. The performance of fly ash is stable and its price is low, which provide the potential to realize its application as an adsorbent to treat pollutants in water.Adsorption characteristics of fly ash from a power plant and its main ingredient-alumina on three typical antibiotics in aqueous solution, namely, sulfanilamide (SA), tetracycline hydrochloride (TC) and norfloxacin (NOR), under different conditions of initial adsorbent dosage, oscillating frequency, temperature, and solution pH, were investigated, kinetics and thermodynamics of those adsorption systems were analyzed, and their interaction mechanisms were simulated in theory by the molecular dynamics (MD) simplified models. It can provide references for the selection of adsorbent to treat antibiotics in water, and also provide a new way to achieve the recycling utilization of fly ash from power plants.The main conelusions are as follows:(1) In the adsorption removal process of antibiotics in aqueous solution by alumina and fly ash, the adsorption effect is influenced by many factors. Within the adsorbent dosing range (0.1-5.0 g·L-1) in this experiment, with the increase of adsorbent dosage, the adsorption effect becomes obvious and the equilibrium adsorptive quantity decreases; Within the temperature range studied (15,25 and 35℃), the adsorption effect at 25℃ is the best; A high oscillating frequency is conductive to the adsorption; for different antibiotics, adsorption effects varies obviously under different pH conditions, and adsorption processes of SA, TC, NOR correspond to different optimum pH conditions. These differences are related to solubility, existing form and surface charge species of antibiotics and various components in fly ash under different pH values.(2) Adsorption mechanisms of three kinds of typical antibiotics onto alumina and fly ash can be explained by adsorption isotherm model, dynamics and thermodynamics analysis. Different adsorption systems fit Langmuir and Freundlich adsorption isotherm models differently, and the overall fitting condition is poor, which may be related to the actual complexity of fly ash composition and the interaction mechanism between antibiotics and adsorbent. The pseudo-second-order model fits all the corresponding adsorption behaviors of three kinds of antibiotics well, indicating that the adsorption rate is proportional to the square of the adsorbate concentration. All adsorption systems fit intraparticle diffusion model well, showing that adsorption processes of antibiotics onto fly ash or alumina are controlled by both membrane diffusion and internal diffusion. The internal diffusion rate constant kint decreases with the increase of adsorbent dosage, which is related to the impetus in mass transfer process and the diffusion trend of antibiotic molecules.(3) For the adsorption systems of antibiotics onto both alumina and fly ash, they have the following same rule: the adsorption effect of TC is the best, NOR is better, and SA is the worst. The energy data of MD simulation is also consistent with the results, showing that the simulation systems designed are reasonable and reliable.