A novel advanced oxidation process to degrade organic pollutants in wastewater:Microwave-activated persulfate oxidation

This article, for the first time, provides a novel advanced oxidation process based on sulfate radical （SO^4·-） to degrade organic pollutants in wastewater： microwave （MW）-activated persulfate oxidation （APO） with or without active carbon （AC）. Azo dye acid Orange 7 （AO7） is used as a model compound to investigate the high reactivity of MW-APO. It is found that AO7 （up to 1000 mg/L） is completely decolorized within 5-7 min under an 800 W MW furnace assisted-APO. In the presence of chloride ion （up to 0.50 mol/L）, the decolorization is still 100% completed, though delayed for about 1-2 min. Experiments are made to examine the enhancement by AC. It is exciting to find that the 100% decolorization of AO7 （500 mg/L） is achieved within 3 min by MW-APO using 1.0 g/L AC as catalyst, while the degradation efficiency maintains at 50% by MW energy without persulfate after about 5 min. Besides the destruction of visible light chromophore band of AO7 （484 nm）, during MW-APO, two bands in the ultraviolet region （228 nm and 310 nm） are rapidly broken down. The removal of COD is about 83%-95% for 500 mg/L AO7. SO^4·- is identified with quenching studies using specific alcohols. Both SO^4·- and ·OH could degrade AO7, but SO^4·- plays the dominant role. In a word, MW-APO AC is a new catalytic combustion technology for destruction of organic contamination even for high concentration.

A comparison between high temperature catalytic and persulfate oxidation for the determination of total dissolved nitrogen in natural waters

Total dissolved nitrogen(TDN) is an important parameter for assessing the nutrient cycling and status of natural waters.The accurate determination of TDN in natural waters is essential for assessing its contents and distinguishing different forms of nitrogen in the water.The TDN in various systems has been largely documented,and the concentrations of TDN are usually obtained using high-temperature catalytic(HTC) or persulfate oxidation(PO).However,the accuracy of these methods and their suitability for all types of natural waters are still unclear.To explore both methods in-depth,assorted samples were tested,including eight solutions composed of nitrogen-containing compounds(3 dissolved inorganic nitrogen fractions:NO_(3)^(-),NO_(2)^(-)and NH_(4)^(+);5 organic compounds:EDTA-2Na,vitamin B1,vitamin B12,amino acids,and urea) and 105 natural waters which were collected from an open ocean(Northwest Pacific Ocean,28),a marginal sea(Yellow Sea,34),an estuary(Huanghe River mouth,31),rivers(Huanghe River,4;Licun River,4),and precipitations(4 samples).The results showed that heterocycles and molecular dimensions had certain effects on the oxidation efficiency of the PO method but had little effect on HTC.There was no significant difference between the two methods for natural waters,but HTC was more suitable for deep-sea samples with low TDN concentrations(less than 10 μmol/L) and low organic activity.Overall,HTC has a relatively simple measurement process,a high degree of automation,and low error.Therefore,HTC can be recommended to determine the TDN of samples in freshwater and seawater.

Comparison of exogenous degrader-enhanced bioremediation with low-dose persulfate oxidation for polycyclic aromatic hydrocarbon removal in alkaline soil:efficiency and influence on ecological health

Polycyclic aromatic hydrocarbon(PAH)-contaminated soils are usually complex and characterized by a lack of nutrition and soil salinization,resulting in difficulties in soil remediation.In this study,bioaugmentation with a PAH-degrading Bacillus PheN7(BA)and low-dose persulfate oxidation(PS),along with natural biodegradation,were utilized to remediate alkaline PAH-contaminated soil.The soil used in the study had a pH of 9.35,and the total PAH content was 568.8±31.0 mg/kg dry soil.After 42 d of remediation,the degradation efficiency of PAHs was 96.72%and 93.88%using persulfate oxidation and bioaugmentation,respectively,whereas 38.66%of PAHs were degraded in natural attenuation(NA).Bacillus was the dominant genera throughout the process of bioremediation with the relative abundance of 79.3%on day 42 in the BA system,whereas,Alcanivorax was enriched and became the dominant genera in PS systems.In the meantime,PAH degradation genes were detected with remarkably higher level in the BA system than in PS system during the remediation.In addition to the degradation of contaminants,persulfate oxidation promotes microbial bioremediation efficiency mainly by lowering the pH to neutral and increasing the active phosphorus content in the soil.Microbial species and ecological niches were less reduced in the PS system than in the BA system.Collectively,persulfate oxidation had a better impact on the soil microbiome and is more suitable for long-term soil health than bioaugmentation through PheN7 addition.

Tourmaline activated persulfate for degradation of Sirius Türkis GL 01

The high Fe^(2+)content of tourmaline(TM)has potential of activating a persulfate reaction.However,information pertaining to using TM as an activator in persulfate oxidation process is currently unavailable.In this study,powdered TM was used to activate persulfate(PS)oxidation for decolorization synthetic direct azo dye,Sirius Türkis GL 01(STGL).Findings revealed that decolorization was significantly enhanced by TM/PS combined with ultrasound.A suitable oxidation condition for removal true color was TM 1.5 g/L,PS 5 *10^(-4)M,US 106 W/cm^2(20 min sonication at 20 kHz),and initial pH 6.0,which could completely remove the color and COD of 40 mg/L STGL after 20 min treatment.Oxidation condition under higher TM dosage with higher sonication power is beneficial for generation of sulfate radicals,consequently,promoting the oxidation performance of TM/PS process.Results clearly indicated that Fe-tourmaline,can be potentially used to activate PS oxidation for effective decolorization of wastewater containing direct azo dyes.

Investigation of the mechanism of phytate-modified biochar-catalyzed persulfate degradation of Ponceau 2R

The mechanism of oxidation and degradation effect of phytate-modified biochar catalyzed persulfate on Ponceau 2R was investigated.Chemical-structural properties of phytate-modified biochar,such as surface morphology and surface oxygen-containing functional groups were characterized.The results suggest that modified biochar has better oxidation performance than unmodified biochar,and the modified biochar generated at 500℃pyrolysis temperature can catalyze peroxymonosulfate(PMS)system with high efficiency,in large pH and temperature scope.And the degradation mechanism of Ponceau 2R by biochar-catalyzed PMS generation(BC-PMS)system was researched.It revealed that PBC300(phytate-modified biochar pyrolyzed at 300℃),PBC500(phytate-modified biochar pyrolyzed at 500℃),and PBC700(phytate-modified biochar pyrolyzed at 700℃)may have metaphosphoric acid linked to oxygen atoms and metaphosphoric acid linked in a bridging manner on the surface of biochar,catalyzing the production of hydroxyl radicals by PMS.PBC700 catalyzes the production of singlet oxygen by PMS through its structural defects,and singlet oxygen is the main catalytic product of PBC700.