Heat-activated Persulfate Oxidation Research Articles

Poly- and per-fluoroalkyl substances in water: Occurrence, analytical methodologies, and remediations strategies: A comprehensive review

Abstract Poly- and perfluoroalkyl substances (PFASs) are fluoro-organic compounds comprising thousands of anthropogenically produced chemicals with various industrial and consumer applications. This review compiles recent information on the sources, occurrence, and health effects of PFAS in aquatic environments. Secondly, as a primary requirement for assessing the PFAS concentration in water, this review systematically summarised the analytical methodologies (sample preparation and analytical detection techniques) for PFAS. Furthermore, health risks associated with PFAS in water are outlined. Finally, researchers worldwide have investigated the strategies for the remediation and elimination of PFAS from water. Previous studies have shown that PFASs are present in various water bodies with the highest concentration detected in Germany (94–4,385 ng·L−1 in river and drinking waters). The findings of this review further revealed that solid-phase extraction techniques were the most preferred for sample preparation compared to liquid–liquid extraction techniques. Solid-phase extraction technique improved the limit of detection and the limit of quantification of many analytical techniques to 0.010–1.15 and 0.030–4.00 ng·L−1, respectively. For PFAS remediation, the adsorption method and chemical oxidation using heat-activated persulfate and photochemical oxidation were the most used techniques. The most studied water matrices were drinking, river, groundwater, wastewater, and modelled ultra-pure water. The most used detection technique was found to be liquid chromatograph-tandem mass spectrometer (LC-MS/MS).

Insight into the application of micro-nano bubbles combined with heat-activated persulfate oxidation for removing dissolved organic matter from printing and dying wastewater

The effluent quality of printing and dyeing wastewater after secondary treatment does not meet industry discharge standards, which poses serious environmental risks. In this work, micro-nano bubbles and a heat-activated persulfate advanced oxidation process were innovatively combined to thoroughly treat industrial printing and dyeing wastewater. Under the optimal reaction conditions (a reaction time of 60 min, persulfate concentration of 20 mM, and temperature of 40 °C), the effluent quality met the discharge standards. Furthermore, the degradation and transformation mechanisms of dissolved organic matter during the wastewater treatment process were investigated by three-dimensional fluorescence spectroscopy and Fourier ion transform spin resonance mass spectrometry. The results showed that organic compounds in the wastewater were clearly degraded by the treatment process, and this was accompanied by a significant increase in molecular diversity. In summary, this work provides insight into the practical application of micro-nano bubbles in the advanced oxidation treatment of industrial wastewater as well as the degradation mechanism responsible for removing pollutants from this wastewater.

Enhanced treatment of azo dyes in wastewater using heat-activated persulfate with micro-nano bubble aeration

Azo dyes-containing wastewater can lead to environmental issues and pose threats to public health. The efficient degradation of azo dyes with novel and potent techniques, remains a challenge. This study presented an innovative utilization of micro-nano bubble aeration technology to improve the treatment of Rhodamine B through heat-activated persulfate oxidation. Through single factor experiments, the impacts of persulfate concentration, temperature, initial Rhodamine B concentration, and pH values were systematically explored on the degradation of Rhodamine B in heat-activated persulfate oxidation. The removal rate of Rhodamine B was 94.53% optimized by Response surface optimization method. The reaction rate was in the range of 0.0109–0.0528 min−1, governed by pseudo-first-order kinetics. By applying the Arrhenius equation, the activation energy was determined to be 14.06 KJmol−1. Furthermore, properties of micro-nano bubbles and their synergistic coefficient were investigated in heat-activated persulfate oxidation. Quenching tests revealed the predominance of sulfate radicals, and full wavelength scanning facilitated an in-depth investigation of the reaction mechanism. Additionally, a proposed electron shell structure elucidated the decomposition process of Rhodamine B. Therefore, the implementation of micro-nano bubble aeration technology based on heat-activated persulfate oxidation, held the promise as an efficient and effective approach for the treatment of printing and dyeing wastewater.

Advanced oxidation processes for removal of organics from cooling tower blowdown: Efficiencies and evaluation of chlorinated species

One of the major challenges in reusing cooling tower blowdown water (CTBD) utilizing membrane processes is its remaining organic compounds, e.g., humic substances leading to biofouling. Besides, the possible abundance of chloride in CTBD imposes the concern of the formation of chlorinated by-products. To choose a pre-treatment process for the studied CTBD composition, various advanced oxidation processes (AOPs), including electrooxidation (EO), photocatalytic degradation (PCD), heat-activated persulfate oxidation (PS), UVC/vacuum UV (UVC/VUV), and UVC processes, were evaluated and compared based on two main targets: i) highest removal and mineralization of the organics, especially humic substances; and ii) lowest formation of chlorinated by-products including adsorbable organic halides and oxychlorides. All the processes were conducted in the natural condition of the real CTBD, while solution pH was monitored. Based on results of chemical oxygen demand, total organic carbon, dissolved organic carbon, UV254 absorbance, liquid-chromatography–organic carbon detection (LC-OCD), and fluorescence excitation-emission matrices (FEEM), it is concluded that PS leads to complete removal of organic compounds along with the lowest formation of low molecular weight organic acids and organic neutrals. FEEM and LC-OCD data also indicated that EO, PCD, and UVC/VUV processes brought about substantial removal of organic compounds and broke down the humic substances into low molecular weight building blocks and organics. Besides, EO exhibited the highest AOX and oxychlorides formation, while these were limited when using the other AOPs. Summarizing, PS, PCD, and UVC/VUV were efficient processes for the degradation and mineralization of organics without generating significant amounts of chlorinated by-products.

Impact of application of heat-activated persulfate oxidation treated erythromycin fermentation residue as a soil amendment: Soil chemical properties and antibiotic resistance

Erythromycin fermentation residue (EFR) is the precipitation of fermentative biowaste used for extracting erythromycin (ERY) and may be disposed via land application after heat-activated persulfate (PS) oxidation treatment. However, the effects of the treated EFR as a soil amendment on soil chemical properties and the potential resistance risks caused by introduced ERY remain unclear. Here, a laboratory soil incubation experiment was performed to investigate the soil pH, salinity, introduced antibiotics, antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs), as well as bacterial community structure in the treated EFR-amended soil. The results indicated that pH in treated EFR-amended soil decreased firstly and then increased. The salinity of soil increased but soil was still non-saline soil. In addition, the introduced ERY in the treated EFR-amended soil decreased with the half-life of 12.3 d. Moreover, the relative abundances of ERY resistance genes and MGEs in the treated EFR-amended soil were much lower than those in the control at the end of incubation. Bacterial community structure in the treated EFR-amended soil converged to similar structure in control soil after 49 d incubation. Our results showed that heat-activated PS oxidation treatment of EFR prior to application to soil might be in favor of limiting the spread of ERY resistance genes and MGEs.

The release of organic matter, nitrogen, phosphorus and heavy metals from erythromycin fermentation residue under heat-activated persulfate oxidation conditioning

Erythromycin fermentation residue (EFR) is one kind of biological waste with high organic matter content. The recycling of EFR is not only beneficial to the environmental protection, but also to the economic development. In this study, the release of organic matter, nitrogen (N), phosphorus (P) and heavy metals (HMs) from EFR under heat-activated persulfate (PS) oxidation conditioning was investigated. Results indicated that oxidation conditioning promoted the release of soluble chemical oxygen demand (SCOD). Heat-activated PS oxidation conditioning boosted the release of total nitrogen (TN), ammonia‑nitrogen (NH4+-N) and nitrate‑nitrogen (NO3−-N) into the supernatant, as well as the decomposition of organic nitrogen (ON). Concurrently, heat-activated PS oxidation conditioning facilitated the release of total phosphorus (TP), orthophosphate (PO43−-P) and organic phosphorus (OP) into the supernatant, and the decomposition of OP. Furthermore, heat-activated PS oxidation conditioning resulted in the increase of release efficiencies of HMs. Therefore, heat-activated PS oxidation conditioning was beneficial to the release of organic matter, nutrients and HMs.

Heat activated persulfate oxidation of Reactive Black 5

Heat activated persulfate oxidation of Reactive Black 5

Investigation of iohexol degradation kinetics by using heat-activated persulfate

In this study, we investigated the degradation kinetics of a commonly used iodinated contrast medium, iohexol, by using heat-activated persulfate. The results indicate that the iohexol concentration can be effectively reduced with a removal percentage higher than 85% despite the long reaction time (2–3 h). The iohexol disappearance fitted well with the pseudo-first-order kinetic model. The persulfate consumption almost reached the maximum value during the initial 5 min of the reaction. Subsequently, persulfate was no longer consumed, which resulted in a decrease in the reaction rate. The pseudo-first-order rate constant of iohexol degradation significantly increased with temperature but decreased with an increase in pH from 5 to 9. The results of the quenching experiments performed using ethanol and tert-butanol indicate that the role of hydroxyl radicals was more important than that of sulfate radicals in iohexol degradation during heat-activated persulfate oxidation. However, without heat activation, persulfate did not react with iohexol. Therefore, the effect of pH on the HO· concentration dominated the effect of pH on iohexol degradation. High concentrations of bicarbonate (≥5 mM), chloride (≥1 mM), and dissolved natural organic matter (≥5 mg/L) inhibited the degradation of iohexol due to the consumption of sulfate and hydroxyl radicals. The mineralization percentage was only 3.8% (no considerable improvement) when the temperature was increased to 80 °C. The molecular structures of the intermediates contained iodine with molecular weights higher than 377 Da. Moreover, the generation of iodide was detected. The experimental results suggest that special attention should be paid to the risk of the formation of disinfection by-products in the subsequent chlorine disinfection process when treating natural water containing iohexol through heat-activated persulfate oxidation.

Degradation of sulfamethoxazole by heat-activated persulfate oxidation: Elucidation of the degradation mechanism and influence of process parameters

In this article, heat-activated persulfate oxidation was investigated as a promising technique for the removal of sulfamethoxazole from an aqueous environment. It was found that the degradation efficiency of sulfamethoxazole increases with increasing persulfate concentration due to the increased SO4− production. As suggested by the Arrhenius equation, the sulfamethoxazole degradation rate constant increased with increasing temperature. An activation energy of 103 kJ/mol was determined. Furthermore, the initial pH of the reaction mixture had a large influence on the degradation of sulfamethoxazole. At higher initial pH values, the degradation of sulfamethoxazole increased. The main cause for this increase is a difference in sulfamethoxazole distribution: at higher pH, the deprotonated form of sulfamethoxazole is present and found to be more susceptible to degradation. A second reason was found to be the formation of OH at higher initial pH values, although this contribution was smaller. To elucidate the degradation process, six intermediates were identified, and the difference in formation of these compounds at different initial pH values was revealed. Through ECOSAR modeling, some degradation products were found to be of main interest when monitoring the toxicity of the degradation mixture.

Variations of physical and chemical properties in relation to erythromycin mycelial dreg dewaterability under heat-activated persulfate oxidation conditioning

Erythromycin mycelial dreg (EMD) resulting from erythromycin (ERY) production process may be used as a nutrient resource. However, it has a high moisture content, which makes handling operations complicated. In this study, the EMD dewaterability under heat-activated persulfate (PS) oxidation conditioning was investigated. The variations of physical and chemical properties of EMD were further investigated to uncover the underlying mechanism of EMD dewaterability. Results indicated that EMD dewaterability was worse under single heat process, but significantly improved under heat-activated PS oxidation process. Heat-activated PS oxidation conditioning was capable to increase zeta potential, reduce median particle size, alter EMD flocs morphology, and disrupt mycelial cells. Concurrently, heat-activated PS oxidation conditioning resulted in the decrease of protein in tightly bound (TB) extracellular polymeric substances (EPS) and total EPS, and the decrease of fluorescing constituents (tryptophan protein, tyrosine protein and tryptophan amino acid) in EPS. Furthermore, a possible mechanism was proposed for heat-activated PS oxidation conditioning.

Reaction pathways of heat-activated persulfate oxidation of naphthenic acids in the presence and absence of dissolved oxygen in water

Dissolved oxygen has been found to participate in the mineralization of naphthenic acids (NAs) by heat-activated persulfate (PS) oxidation. However, the reaction mechanisms involved needs further study. This work reports on the reaction pathways of heat (80 °C)-activated PS oxidation of model NAs in the presence and absence of molecular oxygen from the analyses of the reaction byproducts. The NAs selected include saturated and aromatic ring-bearing structures. The analyses were performed by gas chromatography with mass spectrometer (GC–MS), liquid chromatography with quadrupole time-of-flight mass spectrometer (LC-QTOF-MS), gas chromatography with flame ionization detector (GC-FID) and ion chromatography (IC). The results suggest that decarboxylation of NAs is the initial step of PS-oxidation under air and inert atmosphere. Cyclohexanone-like compounds are one kinds of the main intermediates, indicating the occurrence of oxygenation upon the reaction. The formation of those compounds relies on the dissolved oxygen since it was significantly hindered in inert atmosphere. This hindering effect was less significant in the case of aromatic ring-bearing NAs than for the saturated ones. Meanwhile, condensation byproducts were formed in the absence of oxygen. The corresponding degradation and ring-opening mechanisms were postulated on the basis of analytical results.

Erythromycin degradation and ERY-resistant gene inactivation in erythromycin mycelial dreg by heat-activated persulfate oxidation

Erythromycin mycelial dreg (EMD) is a bio-fermentation residue of the pharmaceutical industry that may be used as a nutrient resource. However, the contaminants present in EMD need to be considered and controlled at an acceptable level prior to utilization. In this study, heat-activated persulfate (PS) oxidation of EMD was developed to degrade the residual erythromycin (ERY) and inactivate the ERY-resistant genes. The effects of temperature, initial PS concentration, and pH on the removal of ERY in EMD were studied. The results revealed that 99.0% ERY was degraded by 25 g PS/kg EMD under 80 °C within 120 min. The apparent rate constant (kapp) in the acidic condition was higher than that in the alkaline condition. The contribution of sulfate radical (SO4·-) and hydroxyl radical (HO) on ERY removal in EMD was found to be 36.8% and 29.4%, respectively. Six intermediate products (IPs) of ERY were clarified, and total organic carbon (TOC) was efficiently reduced by 99.4%. Finally, the detected ERY-resistant genes ere(B), erm(A), and erm(B) obviously presented a reduction during the heat-activated PS oxidation process.

Kinetic and mechanistic investigations of the degradation of sulfachloropyridazine in heat-activated persulfate oxidation process

Sulfachloropyridazine (SCP) has significant threat to natural environment and human health worldwide. Efforts have been made to remove SCP using traditional water treatment technologies but the outputs achieved are limited. In this study, we focused on heat-activated persulfate oxidation of SCP. Various factors have been investigated, such as PS concentration, initial pH, temperature and natural water constituent effects. The results showed that the SCP removal rate constants (kobs) followed a quadratic relationship with initial persulfate concentrations (kobs = −1.526 ∗ 10−6 [PS]02 + 5.621 ∗ 10−4 [PS]0 + 0.01158, R2 = 0.923, [PS]0 = 17.5–280 µM) and excellent fitting with the Arrhenius equation (ln (kobs) = −19487.9/T + 59.63, R2 = 0.967, T = 303.15–323.15 K). The pH tests were applied at a wide range of 3.0–10.0, the quickest degradation rate observed at pH 3.0. The consumption rate of PS was strengthened at elevated temperatures, and 40 °C was determined to be an optimal condition. The presence of chloride (Cl−), bicarbonate (HCO3−) and humic acid all showed inhibitory effects. The radical scavenging experiments revealed that HO and SO4− were predominant oxidizing species responsible for SCP removal. These oxidizing species were further verified by EPR tests. LC-MS/MS analysis confirmed seven kinds of byproducts during the removal process which are mainly deriving from SO2 extrusion/Smile-type rearrangement and S-N bond cleavage. Efficiencies of the antibiotics removal were over 85% when 50 g L−1 PS was added to piggery anaerobic fermentation slurry. This remediation technology may appear as a promising way for the removal of highly antibiotics-contaminated water in a small scale.

Degradation of Triclosan by Heat Activated Persulfate Oxidation

Sulfate radical (SO4·-)-based advanced oxidation technologies (SR-AOPs) are widely used for remediation of contaminated groundwater and soils. This study investigated the reaction kinetics, products, and transformation pathways of triclosan, a widely used antimicrobial agent, during its degradation by heat activated persulfate oxidation. Experimental results revealed that increasing temperature or initial persulfate concentration significantly enhanced the degradation of triclosan. The reaction could be fitted in the pseudo-first-order kinetic model and the activation energy (Ea) was determined to be 142 kJ·mol-1. The presence of humic acid markedly inhibited triclosan degradation, whereas chloride (Cl-) showed a more complicated effect. Triclosan degradation was slightly accelerated in the presence of 5 μmol·L-1 Cl-, however, a higher concentration of Cl- (e.g., 10 μmol·L-1) showed an inhibitory effect. Using liquid chromatography-mass spectrometry, a total of six transformation products, including 4-chlorocatechol, 2,4-dichlorophenol, and 2-chloro-5-(2,4-dichloro-6-hydroxyphenoxy)-1,4-benzoquinone, were identified. Accordingly, the cleavage of the ether bond and hydroxylation of the phenol ring were proposed as the principal pathways of triclosan degradation upon reaction with SO4·-. The findings of this study can be used to evaluate the feasibility of decontamination of triclosan by SR-AOPs.

Kinetic and mechanistic investigations of the degradation of propranolol in heat activated persulfate process.

This study investigated the heat activated persulfate (heat/PS) process in the degradation of propranolol from water. Various factors (e.g., temperature, persulfate dose, initial pH and natural water constituent) on PRO degradation kinetics have been investigated. The results showed that the PRO degradation followed a pseudo-first-order kinetics pattern. As temperature rises, the pseudo-first-order rate constant (kobs) was improved significantly, and the kobs determined at 40–70 °C satisfied the Arrhenius equation, yielding an activation energy of 99.0 kJ mol−1. The radical scavenging experiments and the EPR tests revealed that both SO4˙− and ·OH participated in degrading PRO, with SO4˙− playing a dominant role. Higher PS concentration and neutral pH favored PRO degradation. The impact of Cl− and HCO3− were concentration-dependent. A lower concentration of Cl− and HCO3− could accelerate PRO degradation, while the presence of HA showed inhibitory effects. Seven degradation products were recognized through LC/MS/MS analysis. Cleavage of ether bond, hydroxylation, and ring-opening of naphthol moiety are involved in the PRO's degradation pathway. Finally, the formation of disinfection byproducts (DBPs) before and after pre-treated by heat/PS was also evaluated. Compared with direct chlorination of PRO, the heat/PS pre-oxidation greatly impacted the DBPs formation. The higher PRO removal efficiency in natural water indicated the heat/PS process might be capable of treating PRO-containing water samples, however, its impacts on the downstream effect on DBPs formation should be also considered.

Treatment of dinitrodiazophenol industrial wastewater in heat-activated persulfate system.

Heat-activated persulfate oxidation process was investigated as the treatment of dinitrodiazophenol industrial wastewater to degrade refractory pollutants and improve biodegradability. By studying the effects of 4 factors and carrying out orthogonal tests and scale-up experiments, optimal treatment conditions (temperature 90 °C, reaction time 75 min, PS dosage 20.0 g L−1 and initial pH ∼2.0) were obtained. The results showed that under these conditions, COD and color removal efficiencies were 99.22% and 99.99%, respectively. Moreover, an increase in BOD5/COD ratio (from 0 to 0.31) indicates significantly improved biodegradability. Dinitrodiazophenol dosage was measured by high performance liquid chromatography, which showed that dinitrodiazophenol removal efficiency reached 99.99%. Furthermore, the degradation process was analyzed by ultraviolet-visible spectra and Fourier transform infrared spectra. The former demonstrated that aromatic compounds in the system were destroyed during mineralization and the latter indicated that nitro groups on the benzene ring could be oxidized to nitrate. After verification test of the free radicals, mechanism of heat-activated persulfate system was assumed to be that SO4˙− and ·OH function together and SO4˙− predominate. To conclude, the heat-activated PS oxidation technology performs effectively in treatment of DDNP wastewater and expands applications of sulfate-radical-based advanced oxidation technology in industrial-wastewater treatment.

Response to the comments on ‘‘Changes in activation energy and kinetics of heat-activated persulfate oxidation of phenol in response to changes in pH and temperature’’ by Ma, J., Li, H., Chi, L., Chen, H., & Chen, C. [Chemosphere 189 (2017) 86–93

Response to the comments on ‘‘Changes in activation energy and kinetics of heat-activated persulfate oxidation of phenol in response to changes in pH and temperature’’ by Ma, J., Li, H., Chi, L., Chen, H., & Chen, C. [Chemosphere 189 (2017) 86–93

Comment on “Changes in activation energy and kinetics of heat-activated persulfate oxidation of phenol in response to changes in pH and temperature”

Comment on “Changes in activation energy and kinetics of heat-activated persulfate oxidation of phenol in response to changes in pH and temperature”

Changes in activation energy and kinetics of heat-activated persulfate oxidation of phenol in response to changes in pH and temperature

Persulfate (peroxydisulfate, S2O82−) is the newest oxidant used for the in situ chemical oxidation (ISCO) remediation of soil and groundwater. The present study investigated impacts of solution pH, temperature, and persulfate concentration on the reaction rate constant (k1), activation energy (Ea), and reaction order of the heat-activated persulfate process. Phenol was chosen as the model organic contaminant. As temperature increased from 30 °C to 70 °C, k1 exhibited a significant increase from 0.003 h−1∼0.962 h−1 (pH 1.3–13.9) to 1.184 h−1∼9.91 h−1 (pH 1.3–13.9), which corroborated with the activation of persulfate using heat. As pH increased from 1.3 to 13.9, k1 exhibited a 4.3-fold increase at 70 °C and a 320-fold increase at 30 °C, thereby suggesting that: 1) the phenol oxidation rate increased under alkaline conditions, and 2) the enhancement of reaction rate due to alkaline activation was more pronounced at a lower temperature. Increasing pH significantly reduced Ea from 139.7 ± 1.3 kJ/mol at pH 1.3 to 52.0 ± 3.3 kJ/mol at pH 13.9. In contrast to changing pH, increasing persulfate concentration from 20 to 320 mM significantly increased k1 but did not affect Ea. Changes in Ea suggest that persulfate oxidation of phenol experienced different reaction pathways or elementary reaction sequences as the pH changed from 1.3 to 13.9. In addition, the k1 and Ea data also suggest that a minimal pH threshold of ∼11 was required for the effective alkaline activation of persulfate.

Transformation of iodide and formation of iodinated by-products in heat activated persulfate oxidation process

Formation of halogenated disinfection by-products (DBPs) in sulfate radical-based advanced oxidation processes (SR-AOPs) have attracted considerable concerns recently. Previous studies have focused on the formation of chlorinated and brominated DBPs. This research examined the transformation of I− in heat activated PS oxidation process. Phenol was employed as a model compound to mimic the reactivity of dissolved natural organic matter (NOM) toward halogenation. It was found that I− was transformed to free iodine which attacked phenol subsequently leading to iodinated DBPs such as iodoform and iodoacetic acids. Iodophenols were detected as the intermediates during the formation of the iodoform and triiodoacetic acid (TIAA). However, diiodoacetic acid (DIAA) was formed almost concomitantly with iodophenols. In addition, the yield of DIAA was significantly higher than that of TIAA, which is distinct from conventional halogenation process. Both the facts suggest that different pathway might be involved during DIAA formation in SR-AOPs. Temperature and persulfate dose were the key factors governing the transformation process. The iodinated by-products can be further degraded by excessive SO4− and transformed to iodate. This study elucidated the transformation pathway of I− in SR-AOPs, which should be taken into consideration when persulfate was applied in environmental matrices containing iodine.