Research On Adsorption Properties Of Antibiotics By Carbon Nanotubes And Graphene Materials

Antibiotics are poorly biodegradable substance, easily enriched in the environment, the induction of resistant strains, seriously threatening the health of aquatic organisms and the ecological balance, so it arouses people's intense attention and concern. Adsorption method becomes a kind of effective method to remove antibiotics because of its advantages of low cost, high efficiency, good feasibility. The key to adsorption technology is the efficient adsorption material. In this paper, we select several kinds of carbon nanotubes and graphene materials with different structure as adsorbents, and systematically study the performance and mechanism of the adsorption removal to antibiotics in aqueous solution. Main conclusions are as follows:(1) That was studied that the effect of multi-walled carbon nanotubes (MWCNTs) with different oxygen content on antibiotics absorption. With the increase of oxygen content on the surface, adsorption properties of ciprofloxacin showed a continued increase state, but the growth rate became slower. This was the result mainly caused by overall coordinating effect from promotion of hydrophilic and dispersion, and inhibition of water film, as well as ?-? electron donor-receptor interaction. Oxygen content on surface of MWCNTs is an important factor influencing ciprofloxacin adsorption.(2) Graphene hydrogels with three-dimensional macrostructure were prepared through reduction method, which effectively solved problems that nano-powder adsorbents are easy to aggregate, and difficult to separate. Its adsorption behavior to tetracycline was detail studied. The results showed that the experimental data were consistent with the pseudo-second-order kinetic model and the Langmuir isotherm model. The average free energy for adsorption Ea is less than 8 kJ/mol, which indicated that physical adsorption was predominant in the adsorption process. Due to electrostatic interactions, neutral anionsSO42-?Cl-?F- promoted adsorption, while weak acid anions CO32-?SiO32-?PO43- inhibited absorption. Large amounts of electron donor groups such as hydroxyl and amino in tetracycline molecules can form complexes with metal ions like Mg2+, Ca2+?Cd2+?Cu2+?K+ and Na+. The affinities of complexes with adsorbent were higher than that of tetracycline itself, which have different degrees of promoting effect on adsorption.(3) In order to solve the problem that graphene hydrogels were hard to store and adsorption properties of graphene aerogels were poorer, carbon nanotubes with good adsorption performance were adulterated into reduced graphene oxide aerogel. Adsorption performance greatly increased through synergistic effect of both carbon nanotubes and graphene aerogel. After the load of carbon nanotubes, adsorption performance order of tetracycline on aerogels was RGO/CNTs> RGO/CNTs-COOH> RGO. The adsorption capacity of RGO/CNTs was the highest, which was about 3 times of unmodified graphene aerogel. The average free energy Ea for adsorption was less than 8 kJ/mol, which indicated that physical adsorption was predominant in the adsorption process. The adsorption of the tetracycline was strongly affected by pH value. The effect of different anions and cations on the adsorption properties of tetracycline and related mechanism were similar to that graphene hydrogel was used as adsorbent.