Comparison of radical and non-radical activated persulfate systems for the degradation of imidacloprid in water.

The study focuses on degradation efficiency of non-radical activation and radical activation systems of persulfate (PS) to degrade imidacloprid (IMI) by using sodium persulfate (SPS) as PS source. Copper oxide (CuO)-SPS and CuO/biochar (BC)-SPS were selected as PS non-radical activation systems, and pyrite (PyR)-SPS was selected as PS radical activation system. The degradation by CuO-SPS, CuO/BC-SPS and PyR-SPS systems was investigated from acidic to basic conditions (pH 3.0-11.0). Highest degradation by CuO-SPS and CuO/BC-SPS systems was achieved over pH 11.0. In contrast, highest degradation by PyR-SPS system was achieved over pH 3.0, however, PyR-SPS system was also found effective up to pH 9.0. It was found that degradation was more efficient in PS radical activation system, indicating that IMI could be oxidized by radicals rather than by activated PS. Electron paramagnetic resonance (EPR) analysis was carried out to investigate the generation of sulfate (SO4-) and hydroxyl (OH) radicals, which indicated the presence of SO4- and OH in CuO-SPS, CuO/BC and PyR-SPS systems. However, free radical quenching analysis indicated that radicals were main reactive oxygen species for degradation. The lower degradation in PS non-radical activation systems was probably resulted from radicals existed as minor reactive oxygen species. The findings indicated that non-radical oxidation systems showed low reality for degradation and good degradation could be achieved by radical oxidation system. The degradation was also carried out in real waters to investigate the potential applicability of applied systems, which supported PyR-SPS system for effective degradation.

Hayat W ，Zhang Y ，Hussain I ，Huang S ，Du X ... -  《-》

Degradation of tetracycline in water by biochar supported nanosized iron activated persulfate.

Biochar supported nanosized iron (nFe(0)/BC) was synthesized and used as a persulfate (PS) activator to degradation tetracycline (TC). The influence of the initial pH values, PS and nFe(0)/BC dosage, initial TC concentration, and coexist anions were investigated. In the nFe(0)/BC-PS system, TC could be effectively removed at various pH values (3.0-9.0). The degradation efficiency of TC (100 mg/L) was 97.68% using nFe(0)/BC (0.4 g/L) and persulfate (1 mM) at pH 5.0. Coexisting ions (HCO3- and NO3-) had an inhibitory effect on TC degradation. The removal of TC could be fitted by a pseudo-second-order model. Electron-Spin Resonance (ESR) analysis and scavenging tests suggested that sulfate radicals (SO4·-) and hydroxyl radicals (HO·) were responsible for TC degradation. Details of the advanced oxidation process (AOP)-induced degradation pathways of TC were determined based on liquid chromatography mass-spectrometry (LC-MS) analysis. The nFe(0)/BC could still maintain 86.38% of its original removal capacity after five cycles. The findings of this study proved that nFe(0)/BC can be applied to activate PS for the treatment of pollution caused by TC.

Shao F ，Wang Y ，Mao Y ，Shao T ，Shang J ... -  《-》

Degradation of imidacloprid by UV-activated persulfate and peroxymonosulfate processes: Kinetics, impact of key factors and degradation pathway.

UV-activated persulfate (UV/PS) and peroxymonosulfate (UV/PMS) processes as alternative methods for removal of imidacloprid (IMP) were conducted for the first time. The reaction rate constants between IMP and the sulfate or hydroxyl radical were calculated as 2.33×109  or 2.42×1010 M-1 s-1, respectively. The degradation of IMP was greatly improved by UV/PS and UV/PMS compared with only UV or oxidant. At any given dosage, UV/PS achieved higher IMP removal rate than UV/PMS. The pH range affecting the degradation in the UV/PS and UV/PMS systems were different in the ranges of 6-8 and 9 to 10. SO42-, F- and NO3- had no obvious effect on the degradation in the UV/PS and UV/PMS systems. CO32- and PO43- inhibited the degradation of IMP in the UV/PS system, while they enhanced the degradation in the UV/PMS system. Algae organic matters (AOM) were used to consider the impact of the degradation of IMP for the first time. The removal of IMP were restrained by both AOM and natural organic matters. The higher removal rate of IMP demonstrated that both UV/PS and UV/PMS were suitable for treating the water containing IMP, while UV/PS was cost-effective than UV/PMS based on the total cost calculation. Finally, the degradation pathways of IMP were proposed.

Wang Q ，Rao P ，Li G ，Dong L ，Zhang X ，Shao Y ，Gao N ，Chu W ，Xu B ，An N ，Deng J ... -  《-》

Insights into removal of tetracycline by persulfate activation with peanut shell biochar coupled with amorphous Cu-doped FeOOH composite in aqueous solution.

Xu J ，Zhang X ，Sun C ，Wan J ，He H ，Wang F ，Dai Y ，Yang S ，Lin Y ，Zhan X ... -  《-》

Degradation of acetaminophen with ferrous/copperoxide activate persulfate: Synergism of iron and copper.

To enhance the advanced oxidation process based on persulfate, CuO was introduced into the Fe2+/PS system to achieve a synergistic effect between Fe and Cu. Results showed that Fe2+ was able to adsorb onto the CuO surface to form Fe(II) and further reduced Cu(II) into Cu(I), which can further release into the solution to participate in oxidation reactions. In this case, SO4·- can be generated via Fe2+ and Cu+ reactions with PS and ·OH from Cu+ reaction with dissolved oxygen (DO). The degradation efficiency of APAP was studied under the optimal condition (initial pH 6.5, PS = 0.8 g L-1, Fe2+ = 0.7 mM, CuO = 0.3 g L-1), and the results indicated that the Fe2+/CuO/PS system can achieve a higher degradation rate of APAP (92% within 90 min) rather than Fe2+/PS and CuO/PS system (79% and 10%). Quenching experiment was performed to verify the active radicals in the Fe2+/CuO/PS system. Sulfate and hydroxyl radicals were generated in the Fe2+/CuO/PS system. Besides, some critical factors, such as Fe2+ concentration, catalyst dosage, PS concentration, initial pH (buffers and nonbuffers), and dissolved oxygen were evaluated in bath experiments. Results indicated that dissolved oxygen was essential in the Fe2+/CuO/PS system. APAP degradation experiments were conducted in surface water, and the intermediates were detected via GC-MS. The results indicated that the Fe2+/CuO/PS system is effective in the treatment of APAP in natural waters.

Zhang Y ，Zhang Q ，Dong Z ，Wu L ，Hong J ... -  《-》