Empirical modeling and kinetic study of methylene blue removal from synthetic wastewater by activation of persulfate with heterogeneous Fenton-like process

Towards advanced removal of organics in persulfate solution by heterogeneous iron-based catalyst: A review

Heterogeneous iron-based catalysts have drawn increasing attention in the advanced oxidation of persulfates due to their abundance in nature, the lack of secondary pollution to the environment, and their low cost over the last a few years. In this paper, the latest progress in the research on the activation of persulfate by heterogeneous iron-based catalysts is reviewed from two aspects, in terms of synthesized catalysts (Fe0, Fe2O3, Fe3O4, FeOOH) and natural iron ore catalysts (pyrite, magnetite, hematite, siderite, goethite, ferrohydrite, ilmenite and lepidocrocite) focusing on efforts made to improve the performance of catalysts. The advantages and disadvantages of the synthesized catalysts and natural iron ore were summarized. Particular interests were paid to the activation mechanisms in the catalyst/PS/pollutant system for removal of organic pollutants. Future research challenges in the context of field application were also discussed.

Harnessing bromide ions to boost peroxymonosulfate for reactive yellow 145 dye degradation

Bromide (Br-) was found in the fresh waters at concentrations from 0.1 to 1 mg/L and can be used to activate peroxymonosulfate (PMS) as a widely used chemical oxidation agent. In the present study, the reaction between PMS and Br- ions (PMS/Br- process) for the effective degradation of reactive yellow 145 (RY-145) dye was investigated by changing operational parameters vis solution pH, dosage of Br- ions and PMS, RY-145 concentration, and reaction time. Based on the results, the simultaneous presence of PMS and Br- ions in the solution led to efficient degradation of RY-145 with a synergistic index of 11.89. The degradation efficiency of RY-145 was decreased in severe basic pH and the presence of CO32- ions as a coexisting anion. Likewise, 4 mg/L of humic acid (HA), used as a classic scavenger, led to a 26.53% decrease in the RY-145 degradation efficiency. The free bromine (HOBr/OBr-), superoxide radical (●O2-), and singlet oxygen (1O2) was the dominant oxidation agents in RY-145 degradation, which confirmed the nonradical degradation pathway. In addition, PMS/Br- process showed excellent ability in mineralizing RY-145 in different aqueous solutions (total organic carbon (TOC) decreased 86.39% in deionized water and 78.23% in tap water). Although pollutants such as azo dyes can be effectively removed in the PMS/Br- process, the formation of byproducts should be strategically controlled and special attention should be paid when the PMS-based advance oxidation process is applied to treat Br- containing solutions.

Magnetized Activated Carbon Synthesized from Pomegranate Husk for Persulfate Activation and Degradation of 4-Chlorophenol from Wastewater

The compound 4-chlorophenol (4-CP) is known to be a highly toxic compound having harmful effects on human health and the environment. To date, the removal of 4-CP by advanced oxidation processes (AOPs) has attracted tremendous attentions. The persulfate-based AOPs show higher oxidation, better selectivity, wider pH range, and no secondary pollution compared to the traditional Fenton-based AOPs. Carbon materials with low cost and chemical stability are useful for the activation of persulfate (PS) to produce reactive species. Herein, we magnetized activated carbon synthesized from pomegranate husk (MPHAC). By using 4-CP as a model organic pollutant, tests of the activation of PS via MPHAC for the removal of 4-CP were performed. Batch processes were carried out to study the influence of different parameters (initial solution pH, catalyst dose, PS dose, and initial 4-CP concentration) on the adsorption of 4-CP on PHAC with ferric oxide (Fe3O4-PHAC). The results show that under the obtained optimal conditions (MPHAC dose: 1250 mg/L, PS dose: 350 mg/L, solution pH 5, an initial 4-CP concentration of 100 mg/L, and a contact time of 60 min), a 4-CP removal factor of 99.5% was reached by the developed MPHAC/PS system. In addition, it was found that reusing MPHAC in five successive cycles is feasible because the catalyst in the last cycle kept exhibiting a high potential for 4-CP absorption, indicating the economically viable procedure. Therefore, this study provides a comprehensive understanding on the degradation of 4-CP by the magnetized activated carbon persulfate system.

Advanced oxidation of 4-chlorophenol via combined pulsed light and sulfate radicals methods: Effect of co-existing anions

Pulsed light (PL) technology, which is based on photonic technology involves the application of broadband emission of light with short and high-power pulses is beginning to emerge for the treatment of wastes via advanced oxidation processes (AOP). The present work investigates the efficiency of PL as a light source for persulfate (PS) activation (PL/PS) and 4-chlorophenol)4-CP) degradation, an organic model pollutant. The influencing parameters on 4-CP degradation such as solution pH, reaction time, initial concentration of 4-CP, PS dose, pulse intensity and frequency, and distance from PL source are systematically investigated. With increasing pH from 3 to 9, the 4-CP degradation decreased from 49.79 ± 2.49 to 33.12 ± 1.66%. The 4-CP degradation followed the first order kinetics that was improved with increasing reaction time, PS dose, pulse intensity, frequency of pulse, and decreasing pH, initial 4-CP concentration and distance from the PL source. The presence of sulfate, chloride, and carbonate anions in the solution has the inhibitory effects on 4-CP degradation, while nitrate anion improved the performance of PL/PS system. In addition, presence of humic acid had an inhibitory effect on the PL/PS system, which led to a decrease of reaction rate constant and 4-CP degradation was performed in PL/PS system with OH, SO₄^-, O₂^- and ₁O² radicals. The contributions of OH and SO₄^- radicals were 46% and 51%, respectively for the 4-CP degradation and synergistic effect of PL/PS system showed a significant influence on 4-CP degradation while using a combination of PL and PS, suggesting that PL is an effective activator of PS.