An efficient heterogeneous catalyst, pre-magnetized Fe 0 (pre-Fe 0 ) could significantly activate persulfate (PS) to remove Rhodamine B (RhB). The effect of pH, Fe 0 and PS dose on the RhB removal in the pre-Fe 0 /PS and Fe 0 /PS processes were investigated, and optimized by response surface methodology (RSM) to analyze the rate constants of the RhB removal in the pre-Fe 0 /PS process and Fe 0 /PS process ( f ). High RhB removal was obtained at low pH and high dose of Fe 0 and PS in both systems. Low Fe 0 and high PS dose and large pH would result in big value of f , and the simulated maximum f of 44.3 was achieved at 2 mM Fe 0 , 16 mM PS and pH 9. The synergetic factor of pre-Fe 0 /PS (45.6) was larger than that of Fe 0 /PS (21.4). The pre-Fe 0 /PS process presented 2.1–37.5 folds enhancement than the Fe 0 /PS process for the degradation of RhB. The RhB removal in the pre-Fe 0 /PS process was 1.5–11.2 folds enhancement than that of the Fe 0 /PS process in the presence of different anions and cations. Scanning Electron Microscope (SEM) results and the larger intensity of DMPO-SO 4 − adduct signal in the Electron Paramagnetic Resonance (EPR) confirmed the primary role of sulfate radicals generated from the reaction of PS with Fe 0 in the contaminant degradation. The pre-Fe 0 /PS process exhibited advantages over other processes to remove RhB in terms of contaminant removal, working pH range and chemical dose. Therefore, the pre-Fe 0 /PS process is a cost-effective approach for degrading RhB.
Volatile organic compounds (VOCs) emissions are regarded as a worth concerned threat to human health. The UV-Fenton coupled with mass transfer enhanced process shows promising effects on VOCs treatment. However, the detailed mechanism and mathematical model for this method have not been established. This work focuses on the hypothesis and validation of a mathematical model for UV-Fenton removal of VOCs using activated carbon particles to enhance mass transfer efficiency. Based on the mathematical model of reaction-diffusion-mass transfer, a mathematical model is established by using a series of important parameters such as u b , D g , D l , K ial , K l a and hydroxyl radical lifetime. The proposed model in this study introduces the key parameter of synergistic factor, which greatly improves the consistency between the model predicted results and the experimental data (the determination coefficient R 2 distribution range changed from 0.71–0.98 to 0.95–0.98). Moreover, it can also explain reasonably the steady trend of outlet VOC concentration after 30 min of reaction. The mathematical model confirms that the addition of activated carbon during the UV-Fenton reaction ensures mass transfer efficiency and considerably improves (growth from 2% to 54%) the VOCs removal efficiency due to the synergy between UV-Fenton oxidation and mass transfer enhancement. Meanwhile, it provides insight into fruitful utilization of the oxidation capacity in the oxidation reaction,and achieves the purpose of predicting the efficiency of VOC removal in the Fenton process.
Wanhe Qi,Songming Zhu,Abubakar Shitu,Zhangying Ye,Dezhao Liu
Under Minamata Convention restrictions, mercury-free UV source was in need for ultraviolet disinfection in recirculating aquaculture systems (RAS). Ultraviolet emitting diodes (UV-LEDs) seemed a potential mercury-free UV source and had gained increasing attention in water disinfection. In this study, a mercury-free UVA-LED and low concentration peroxymonosulfate (PMS) combination was proposed for E. coli (CGMCC 1.3373) inactivation and real RAS wastewater disinfection. Results showed that UVA-LED and low concentration PMS combination enhanced E. coli inactivation over UVA-LED alone. A synergistic effect on E. coli inactivation with synergy factor of 58.7 % was found when combining UVA-LED irradiation with 1 mg/L PMS. Kinetic rate constant increased by up to 139 % by UVA-LED and 1 mg/L PMS combination, which implied the required UV fluence to 2-log E. coli inactivation was saved up to 42 %. Also, UVA-LED and 1 mg/L PMS combination showed disinfection potential for real RAS wastewater treatment. Mechanism study revealed that the Cl − , · OH and SO 4 ·- played important roles and · OH was dominant radical in saline solution by UVA-LED/PMS process compared to that in phosphate buffered solution(PBS). The E. coli inactivation was caused by UVA-LED irradiation and reactive species generated in UVA-LED/PMS system. Our study provided a potential strategy to introduce the mercury-free UV-LED into RAS and a better understanding of UVA-LED/PMS disinfection process.
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