Enhanced dewaterability of waste activated sludge by a combined use of permanganate and peroxymonosulfate.

Ever-increasing efforts have been made to develop rapid and practical conditioning methods of sludge dewatering. This study demonstrated an innovative combination of potassium permanganate (KMnO4) and peroxymonosulfate (PMS) for sludge dewatering. The combined use of KMnO4 and PMS (KMnO4/PMS) showed its superiority in improving sludge dewaterability over the separate use of KMnO4 or PMS. By dosing 4 mmol g-1 VSS KMnO4 and 3 mmol g-1 VSS PMS, the dewaterability of waste activated sludge (WAS) significantly enhanced as capillary suction time (CST) decreased from 73.65 s to 24.65 s while the water content of dewatered sludge cake (W C) decreased from 78.96% to 70.47%. Apart from CST and W C, the KMnO4/PMS process could also affect negative zeta potential, sludge flocs size and the concentrations of protein and polysaccharide in extracellular polymeric substances (EPS). The enhanced sludge dewaterability and changes of the physicochemical characteristics of the WAS samples during the KMnO4/PMS process were actually ascribed to sulfate radicals (SO4˙-) and hydroxyl radicals (HO˙) in situ generated via PMS activation by manganese oxides (MnO x ) in the states of MnO2 and Mn3O4 transferred from KMnO4 oxidation, which was verified by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) techniques and radical scavenging experiments. Moreover, the Fourier transform infrared spectroscopy (FTIR) analysis further confirmed that the in situ generated SO4˙- and HO˙ could improve sludge dewaterability. Thus, the KMnO4/PMS process could be considered as a promising conditioning method of sludge dewatering.

Ultrasound-enhanced nanosized zero-valent copper activation of hydrogen peroxide for the degradation of norfloxacin.

Commercial nanosized zero-valent copper (nZVC) was used as hydrogen peroxide (H2O2) activator in conjunction with ultrasonic irradiation (US) for the oxidative degradation of norfloxacin (NOR) in this study. Compared with silent degradation system, a significantly enhanced NOR removal was obtained in sono-advanced Fenton process, which involved a synergistic effect between sonolysis and Fenton-like reaction. Almost complete removal of NOR was achieved at 30min when the operating conditions were 0.25g/L nZVC and 10mM H2O2 with ultrasound power of 240W at 20kHz. The released Cu+ during the nZVC dissolution was the predominant copper species to activate H2O2 and yield hydroxyl radicals (OH) in US/nZVC/H2O2 system. According to the radical quenching experiments and electron paramagnetic resonance technique, hydroxyl radicals in solution (OHfree) were verified as the primary reactive species, and superoxide anion radicals (O2-) were regarded as the mediator for the copper cycling by reduction of Cu2+ to Cu+. NOR removal efficiencies were improved in various degrees when increased nZVC dosage, ultrasound power, hydrogen-ion amount and H2O2 concentration. Moreover, the inhibitory effect of different inorganic salts on NOR degradation followed the sequence of Na2SO4>NaNO3≈no salt>NaCl>NaHCO3. Finally, eleven intermediates were identified and five oxidation pathways were proposed, the cleavage of piperazine ring and transformation of quinolone group seemed to be the major pathway.

Activation of peroxymonosulfate by metal (Fe, Mn, Cu and Ni) doping ordered mesoporous Co3O4 for the degradation of enrofloxacin.

Various transition metals (Fe, Mn, Cu and Ni) were doped into ordered mesoporous Co3O4 to synthesize Co3O4-composite spinels. Their formation was evidenced by transmission electronic microscopy (TEM), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analysis. It was found that Co3O4-composite spinels could efficiently activate peroxymonosulfate (PMS) to remove enrofloxacin (ENR) and the catalytic activity followed the order Co3O4-CuCo2O4 > Co3O4-CoMn2O4 > Co3O4-CoFe2O4 > Co3O4-NiCo2O4. Moreover, through the calculation of the specific apparent rate constant (k sapp), it can be proved that the Co and Cu ions had the best synergistic effect for PMS activation. The Co3O4-composite spinels presented a wide pH range for the activation of PMS, but strong acidic and alkaline conditions were detrimental to ENR removal. Higher reaction temperature could promote the PMS activation process. Sulfate radical was identified as the dominating reactive species in Co3O4-composite spinel/PMS systems through radical quenching experiments. Meanwhile, the probable mechanisms concerning Co3O4-composite spinel activated PMS were proposed.

[Base Activation of Peroxymonosulfate for the Degradation of Ciprofloxacin in Water].

The degradation of ciprofloxacin (CIP) in a base activated peroxymonosulfate (PMS) system was investigated. Results showed that a base activated PMS system can efficiently remove CIP. Singlet oxygen (1 O2) and superoxide anion radical (O2-·) were confirmed to be the major reactive oxygen species through radical quenching experiments. The NaOH concentration, PMS concentration, reactive temperature, and coexisting anions also affected CIP removal. Both NaOH and PMS concentration presented a dual effect, which was highly concentration dependent. An improvement in reactive temperature accelerated CIP degradation, and the calculated activation energy (Ea) was determined to be 5.09 kJ·mol-1 through the fitting of the Arrhenius equation. Different anions had different effects on CIP degradation. No obvious change in CIP concentration was observed when Cl-, SO42-, and NO3- were introduced. H2PO42- inhibited the degradation, but CO32- significantly promoted it. Ten oxidation products were identified through UPLC-MS/MS analysis, and the piperazine ring in the molecular structure of CIP was preferentially attacked by reactive oxygen species in the base activated PMS system.