The Sorption Kinetics Characteristic Of Antibiotics Onto Carbonous Adsorbent

The potential application of biochars as soil amendments has attracted a great deal of research attention.One of the most attractive advantages of biochar is that it could sequester carbon and thus controls carbon cycling. This process is essential in regulating global climate change. The analysis of literature results indicated that during the production of biochars using common biomass, only a very small portion of carbon was stabilized. Most of the carbon was released as low-molecular weight volatile organic chemicals or was converted to biofuel. From this point of view, carbon sequestration during biochar production using biomass should be re-evaluated.In this study, the adsorption of ofloxacin (OFL) on carbonaceous sorbents, including biochars produced by pyrolysis of banana peel and corncob, multi-walled carbon nanotubes (CNTs) and activated carbon (AC) were investigated. The adsorption kinetics of OFL could be well fitted using two-compartment model. With the increased carbonization temperature of biochars, the aromaticity increased but organic components for partition reduced, leading to the decreased adsorption of OFL. The O-contents of biochars greatly affected the formation of water cluster on the surface of biochars which inhibited the fast adsorption of OFL. The fast sorption of OFL onto CNTs and AC were faster than onto biochars, attributed to the relatively single surface properties of CNTs and AC. As the more surface area being exposed with the increasing sorption, the slow sorption of OFL onto CNTs indicated slower than onto AC. Furthermore, the highest OFL adsorption based on unit surface was observed on CNTs, implying that if CNTs could be completely dispersed, it might be an efficient adsorbent for organic pollutants removal due to the abundant exposed surface area.The adsorption kinetics of carbamazepine (CBZ) on 9 biochars produced at different charred temperature (200,300 and 500℃) and deashed with different acids (HC1 and HC1-HF) were investigated in this study. The pseudo-first-order model, pseudo-second-order model and two-compartment first order model were applied to fit the adsorption kinetic data. The results showed that the two-compartment first order model fitted the adsorption kinetic data better than other two models. The pyrolytic temperature and mineral contents had significant impact on adsorption kinetics of CBZ. Specifically, the mineral altered significantly after deashing treatment with different acids and was responsible to the fast adsorption of CBZ on biochars, while the aromatic ring structure of biochars become more condensed with increasing pyrolytic temperature and mainly contributed to the slow adsorption. On the one hand, the mineral of biochars likely blocked some adsorption sites of organic matter. On the other hand, the mineral could effectively adsorb organic contaminants. Thus, the effects of mineral on the apparent adsorption of contaminants on biochars were likely controlled by the balance of two aspects. The contribution of fast sorption decreased but the contribution of slow sorption increased to the total sorption with increasing CBZ initial concentrations. The π-π EDA interaction might be an important mechanism for CBZ sorption. The slow sorption was controlled by pore-filling mechanism which was likely to be the rate-limiting step of CBZ sorption kinetics.