Sorption of norfloxacin onto humic acid extracted from weathered coal.

Norfloxacin (NOR), is an ionizable and polar antimicrobial compound, and it may enter the environment in substantial amounts via the application of manure or sewage as a fertilizer. Sorption of NOR onto humic acid (HA) may affect its environmental fate. In this study, HA extracted from weathered coal was used to investigate the sorption of NOR at different solution chemistry conditions (pH, ionic strength) and temperatures. The sorption of NOR onto HA showed a two-stage sorption process with an equilibration time of 48 h. The sorption kinetic curve fitted well with a pseudo second-order kinetic model. Thermodynamic characteristics demonstrated that the sorption of NOR onto HA was a spontaneous and exothermic process predominated by physical sorption. All sorption isotherms fitted well with the Freundlich and Langmuir models and they were highly nonlinear with values of n between 0.4 and 0.5, suggesting the high heterogeneity of HA. Increasing Ca2+ concentration resulted in a considerable reduction in the K(d) values of NOR, hinting that Ca2+ had probably competed with NOR(+,0) for the cation exchange sites on the surfaces of HA. The sorption reached a maximum at pH 6.0 over the pH range of 2.0-8.0, implying that the primary sorption mechanism was cation exchange interaction between NOR(+,0) species and the negatively charged functional groups of HA. Spectroscopic evidence demonstrated that the piperazinyl moiety of NOR was responsible for sorption onto HA, while the carbonyl group and the aromatic structure of HA participated in adsorbing NOR.

Remediation of soils contaminated with polychlorinated biphenyls by microwave-irradiated manganese dioxide.

The removal of polychlorinated biphenyls (PCBs) using microwave-irradiated manganese dioxide (MnO(2)) in PCB-contaminated soils under different conditions is investigated. The removal of PCB77 in two actual soil samples exhibits strong pH-dependent behavior, and the removal efficiency is higher in acidic soil (Ali-Perudic Ferrosols) than that in neutral soil (Udic Argosols). The removal kinetics of PCB77 using microwave-irradiated MnO(2) under different experimental conditions fits a pseudo-first-order kinetic model well. Both the removal efficiency and the kinetic constant (k) values of PCB77 in Ali-Perudic Ferrosols considerably increase, although in a nonlinear fashion, as the initial amount of MnO(2) is increased, as the treated soil mass is increased, and as the microwave power is increased. The reactivity of three PCBs (PCB28, PCB77, and PCB118) did not present as a function of the degree of chlorination in the reaction with microwave-irradiated MnO(2). The pronounced removal of three PCBs in contaminated soil (all above 95%) indicates that MnO(2) in combination with microwave irradiation is promising for technological applications that seek to remediate sites critically polluted with PCBs.

[Catalytic degradation of PCB77 by microwave-induced nano-particle metal oxides in diatomite].

The degradation of PCB77 in diatomite by microwave-induced catalytic oxidation was studied in a sealed vial, including four effects such as microwave (MV) radiating time, addition of different nano-particle metal oxides, concentration and type of acids and dosage of MnO2. The results indicated that PCB77 could be removed significantly by microwave-induced catalytic oxidation. Compared to control reactor (without MV radiation), the removal rate of PCB77 increased by twice after 1 min. In addition, the removal rate of PCB77 under MV radiation was gradually increased with time of radiation and then reached equilibrium after 10 min. The removal rates are about 50% and 20% by addition of H2SO4 and ultrapure water respectively. No significant removal was observed by addition of NaOH and without aqueous media. Moreover, catalytic degradation of PCB77 by microwave-induced nano-particle MnO2 had best removal rate was up to 90% after 1 min, in contrast with addition of nano-particle Fe2O3, CuO and Al2O3. The removal rate raised from 37.0% to 98.5% rapidly with the concentration of H2SO4 ranged from 1 mol/L to 8 mol/L, and H2SO4 mainly played a role of acidification but not oxidation. The addition of 0.01, 0.03 and 0.05 g MnO2 showed the similar result.