Magnetic lanthanide oxide catalysts: An application and comparison in the heterogeneous catalytic ozonation of diethyl phthalate in aqueous solution

Roles of catalytic ozonation by bimetallic Fe/Ce loading sludge-derived biochar in amelioration of sludge dewaterability: Performance and implementation mechanisms

In this study, an environmentally friendly alternative was developed using catalytic ozonation by sludge-derived biochar loaded with bimetallic Fe/Ce (O3/SBC-FeCe) for enhanced sludge dewatering. The results indicated that the lowest capillary suction time (CST) of 20.9 s and water content of dewatered sludge cake (Wc) of 64.09% were achieved under the dosage of 40 mg O3/g dry solids (DS) and 0.4 g SBC-FeCe/g DS which were considered as the optimum condition. In view of excellent electron exchanging capacity of SBC-FeCe with rich Lewis acid sites and conversions of valence sates of Fe and Ce, more O3 were decomposed into reactive oxygen species under the catalytic action of SBC-FeCe, which strengthened oxidizing capacity. Enhanced oxidation rendered sludge cells inactivation and compact network structure rupture releasing intracellular water and organic substances. Subsequently, hydrophilic organic matters were attacked and eliminated lessening sludge viscosity and colloidal forces and intensifying hydrophobicity and flowability. In addition, changes of sludge morphology suggested that sludge roughness was alleviated, structural strength and compressibility were raised and porous and retiform structure was constructed providing channels for water outflow by adding skeleton builder of SBC-FeCe. Overall, the synergistic interaction of strengthened oxidation and skeleton construction improved sludge dewaterability.

Advanced oxidation processes for phthalate esters removal in aqueous solution: a systematic review

This study addresses a systematic review of the scientific literature to evaluate the most common advanced oxidation processes (AOP) for the removal of phthalate esters (PE) in aqueous matrices. Six AOP were reviewed for PE degradation such as processes based on photolysis, Fenton, ozonation and sulfate radicals ( SO 4 • - ), combined AOP and other processes. The PE degradation efficiencies by AOP processes ranged from 40.3 to 100%. In the reviewed literature, an initial PE concentration within 0.04-250 mg/L was applied. The H₂O₂ concentrations used in the UV/H₂O₂ process and O₃ concentrations in ozonation-based processes ranged between 0.85-1,360.6 mg/L and 2-4,971 mg/L, respectively. Based on the reported results, the PE oxidation data fit well to the pseudo-first order kinetic model. A review of the studies revealed that many oxidant species are produced in the AOP, including hydroxyl radicals (^•OH), SO 4 • - , superoxide radical anions ( O 2 - • ), hydroperoxyl radicals (HO₂ ^•), hydrogen peroxide (H₂O₂), and singlet oxygen (O₂). Among these oxidants, ^•OH play a key role in the degradation of PE. However, SO 4 • - are more effective and efficient than ^•OH since SO 4 • - has a higher oxidation power (E = 2.5-3.1 V) compared to ^•OH radicals (E = 1.8-2.7 V). In different AOP processes, the aromatic rings of PE are destroyed by ^•OH and produce intermediates such as phthalic acid (C₆H₄(CO₂H)₂), benzoic acid ethyl ester (C₉H₁₀O₂), 2, 5-dihydroxybenzoic acid (C₇H₆O₄), formic acid (CH₂O₂), acetic acid (CH₃COOH), and oxalic acid (C₂H₂O₄), among some others. Until now, limited data have been reported on PE toxicity assessment. The reviewed literature has shown that AOP can be used effectively to degrade PE from aqueous matrices. However, this systematic study suggests focusing more on the evaluation of the toxicity of the effluent resulting from AOP for the decomposition of PE in future studies.

Advanced oxidation processes for the removal of phthalate esters (PAEs) in aqueous matrices: a review

Over the past few decades, phthalate esters (PAEs) used as additives to improve the persistence and flexibility of polymeric materials. They are also used in cosmetics, insect repellents, and propellants, and their continuous input into drinking waters has constituted a serious risk to human health and the environment. DBPs are compounds classified as hazardous substances and have teratogenic properties. Due to the high bioaccumulation of DBP, they have toxic properties in different organisms, making it very important to remove PAEs before discharging them into environments. In this study a systematic review was designed to evaluate Advanced oxidation processes (AOPs) studies which have successfully treated contaminated water with PAEs. Among AOPs, particularly photocatalytic, UV/H₂O₂ photolysis, sonolysis, and ozone-based processes were more tried to degrade PAEs in aqueous solutions. Additionally, a more detail of each AOPs was explained. Findings showed that all advanced oxidation processes, especially combined AOPs have good results in the degradation of PAEs in water.

Application, mechanism and prospects of Fe-based/ Fe-biochar catalysts in heterogenous ozonation process: A review

A growing number of novel organic contaminants have escalated the demands and challenges for water treatment technology. Advanced oxidation processes based on ozone have the advantage of strong oxidative capacity and higher efficiency, which have promising application prospects in the treatment of refractory organic contaminants. Biochar has attracted a lot of interest in recent years in wastewater treatment owing to its porous structure, portable preparation and outstanding stability. Moreover, iron species are widely used in catalytic ozonation owing to their magnetic polarization, vast abundance and low price. Despite a plethora of research on Fe-based catalysts in ozonation process, the heterogeneous catalytic ozonation with Fe-loaded biochar lacks a comprehensive compendium. This review intends to introduce the research progress on Fe-based catalysts and Fe-loaded biochar in heterogeneous catalytic ozonation progress, summarize and further explore the mechanisms and detection techniques of various active components in catalytic ozonation, as well as providing fresh insights for future research.

Advanced catalytic ozonation for degradation of pharmaceutical pollutants-A review

Various chemical treatment techniques are involved in removing refractory organic compounds from water and wastewater using the oxidation reaction of hydroxyl radicals (^•OH). The use of catalysts in advanced catalytic ozonation is likely to improve the decomposition of molecular ozone to generate highly active free radicals that facilitate the rapid and efficient mineralization and degradation of numerous organics. For the degradation of toxic organic pollutants in wastewater, the advanced catalytic ozonation process has been widely applied in recent years. Low utilization efficiency of ozone and ineffective mineralization of organic contaminants by ozone can be remedied with advanced catalytic ozonation. Advanced catalytic ozonation has gained popularity because of these merits. However, homogeneous catalytic ozonation has the disadvantage of producing secondary contaminants from the addition of metallic ions. Heterogeneous catalytic ozonation can overcome this drawback by utilizing metals, metallic oxides, and carbon materials as a catalyst of efficacy and stability. This review discusses various aspects of catalytic ozonation in wastewater treatment of pharmaceutical pollutants, application of catalytic ozonation process in typical wastewater, and prospects in advancing the techniques in heterogeneous catalytic ozonation.

Catalytic effect of γ-Al(OH)3, α-FeOOH, and α-Fe2O3 on the ozonation-based decomposition of diethyl phthalate adsorbed on sand and soil

Diethyl phthalate (DEP) is a pollutant which can be found on soils as a result of its widespread application in plastic industry. Soil contaminated with DEP requires the application of different chemical methods to attain its remediation. Among these methods, ozonation has proven to be effective against toxic soil pollutants. The presence of metal oxides in soil is a possible source of catalytic effect. In this study, it was analyzed the catalytic effect of goethite (α-FeOOH), hematite (α-Fe₂O₃), and gibbsite (γ-Al(OH)₃) in combination with O₃ to achieve DEP decomposition. The DEP elimination efficiency by ozonation on the sand increased according to the following order: without catalyst < γ-Al(OH)₃ < α-Fe₂O₃ < α-FeOOH. Among these three oxides, goethite has the highest OH groups density. The reaction of OH groups and O₃ favors the formation of oxidant species, such as O₂•^- and OH•. The effect of the moisture content, the catalyst concentration, and the type of soil (sand and calcined soil) were also studied. The latter had a significant influence on the total organic carbon (TOC) removal. The mineralization degree was 84% in the O₃-soil system, while only 40% was obtained with O₃-sand (α-FeOOH) in dry sand after 8 h of treatment. Calcined soil promoted the increase of TOC removal due to the presence of different metal oxides, which were active centers for O₃ decomposition. The toxicity tests of the three reaction systems (O₃-sand, O₃-sand (α-FeOOH), and O₃-soil) were evaluated on lettuce seed germination before and after DEP ozonation.

Magnetically recyclable Ag/TiO2 co-decorated magnetic silica composite for photodegradation of dibutyl phthalate with fluorescent lamps

In recent years, industrial contaminants and especially organic pollutions have been threatening both environmental safety and human health. Particularly, dibutyl phthalate (DBP) has been considered as one of the major hazardous contaminants due to its widespread production and ecological toxicities. Consequently, reliable methods toward the efficient and environmentally benign degradation of DBP in wastewater would be very desirable. To this end, a novel magnetically separable porous TiO₂/Ag composite photocatalyst with magnetic Fe₃O₄ particles as the core was developed and successfully introduced to the photocatalytic degradation of DBP under visible irradiation with a fluorescent lamp. The presented work describes the grafting of Ag co-doped TiO₂ composite on the silica-modified porous Fe₃O₄ magnetic particles with a simple and inexpensive chemical co-precipitation method. Through the investigation of the influencing factors including photocatalyst dosage, initial concentration of DBP, solution pH, and H₂O₂ content, we found that the degradation efficiency could reach 74%. The photodegradation recovery experiment showed that the degradation efficiency of this photocatalyst remained almost the same after five times of reuse. In addition, a plausible degradation process was also proposed involving the attack of active hydroxyl radicals generated from this photocatalysis system and production of the corresponding intermediates of butyl phthalate, diethyl phthalate, dipropyl phthalate, methyl benzoate, and benzoic acid.

Application of Heterogeneous Catalytic Ozonation for Refractory Organics in Wastewater

Catalytic ozonation is believed to belong to advanced oxidation processes (AOPs). Over the past decades, heterogeneous catalytic ozonation has received remarkable attention as an effective process for the degradation of refractory organics in wastewater, which can overcome some disadvantages of ozonation alone. Metal oxides, metals, and metal oxides supported on oxides, minerals modified with metals, and carbon materials are widely used as catalysts in heterogeneous catalytic ozonation processes due to their excellent catalytic ability. An understanding of the application can provide theoretical support for selecting suitable catalysts aimed at different kinds of wastewater to obtain higher pollutant removal efficiency. Therefore, the main objective of this review article is to provide a summary of the accomplishments concerning catalytic ozonation to point to the major directions for choosing the catalysts in catalytic ozonation in the future.

A comparative study on ozone, hydrogen peroxide and UV based advanced oxidation processes for efficient removal of diethyl phthalate in water

Several Advanced Oxidation Processes (AOPs) including O₃/H₂O₂, O₃/TiO₂, O₃/activated carbon (AC), O₃/Al₂O₃, O₃/Fe²⁺/H₂O₂ and UV/TiO₂ have been investigated and compared for the removal of diethyl phthalate (DEP), an endocrine disrupting compound, in aqueous solutions. Hydroxyl radicals were the main species responsible for DEP degradation and this was supported by computational chemistry calculation, scavenger experiments, and LC/MS/MS analysis. The change of the abundance of reaction products over time was determined. Organic acids as well as anhydride and hydroxylated products were found to accumulate in solution even after long reaction time (2 h). Careful choice of the operating parameters (pH, ozone concentration and catalyst dosage) was crucial to achieve enhanced performance of the combined processes above what each oxidant and catalyst can achieve alone. O₃/AC process was found to reduce the oxidation efficiency of O₃ at high ozone concentrations. Heterogeneous catalytic ozonation with Al₂O₃ was the most effective process for DEP removal (∼100% removal in about 15 min) and based on pseudo-first-order kinetics at pH7, the studied oxidation processes followed the order: O₃/Al₂O₃(0.093 min^-1)>O₃/H₂O₂/Fe²⁺(0.076 min^-1)>O₃/AC(0.069 min^-1)>O₃/H₂O₂(0.053 min^-1)>O₃/TiO₂(0.050 min^-1)> O₃ alone (0.039 min^-1)>UV/TiO₂(0.009 min^-1).

Natural mackinawite catalytic ozonation for N, N-dimethylacetamide (DMAC) degradation in aqueous solution: Kinetic, performance, biotoxicity and mechanism

To enhance the degradation of N, N-dimethylacetamide (DMAC) in aqueous solution, the natural mackinawite (NM) is introduced for catalytic ozonation in this study as it is an environmentally friendly catalyst with low cost and easy availability. The properties of the NM were initially characterized via scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Then, impact factors including NM dosage, ozone gas concentration and initial pH were investigated and the optimal conditions (i.e., NM dosage = 3.5 g/L, ozone gas concentration = 300 L/min, initial pH = 6.8) were obtained in NM/O3 process. Besides, the superiority of the NM/O₃ process was confirmed by the experiments that the degradation efficiency of DMAC in the NM/O₃ process (i.e., 95.4%) was much higher than that in the zero-valent iron (ZVI)/O₃ process (i.e., 46.1%) and the synthetic FeS/O₃ process (i.e., 68.6%). Furthermore, the intermediate and possible degradation pathway of DMAC were proposed, and the biological toxicity of the intermediate was subsequently evaluated by the activated sludge. Finally, the mechanism of the NM/O3 process was proposed in this study based on control experiment and radical scavenging experiment. The extraordinary efficiency for DMAC degradation was found to be mainly caused by HO^• of the reactive oxygen species (ROS) (i.e., HO^•, O₂^•- and H₂O₂) generated in the NM/O₃ process. Therefore, this study confirmed that NM was a high efficient catalyst for degradation the toxic and refractory pollutants in catalytic ozonation system.

Chemical and petrochemical industry

The potential sources of various metals in chemical and petrochemical processes are discussed. Special emphasis is put on the catalysts used in the industry. Their main applications, compositions, especially metal contents are presented both for fresh and spent ones. The focus is on the main types of metals used in catalysts: the platinum-group metals, the rare-earth elements, and the variety of transition metals. The analysis suggested that chemical and petrochemical sectors can be considered as the secondary source of metals. Because the utilization of spent refinery catalysts for metal recovery is potentially viable, different methods were applied. The conventional approaches used in metal reclamation as hydrometallurgy and pyrometallurgy, as well as new methods include bioleaching, were described. Some industrial solutions for metal recovery from spent solution were also presented.

Photocatalytic degradation properties of α-Fe2O3 nanoparticles for dibutyl phthalate in aqueous solution system

The phthalate ester compounds in industrial wastewater, as kinds of environmental toxic organic pollutants, may interfere with the body's endocrine system, resulting in great harm to humans. In this work, the photocatalytic degradation properties of dibutyl phthalate (DBP) were investigated using α-Fe₂O₃ nanoparticles and H₂O₂ in aqueous solution system. The optimal parameters and mechanism of degradation were discussed by changing the morphology and usage amount of catalysts, the dosage of H₂O₂, pH value and the initial concentration of DBP. Hollow α-Fe₂O₃ nanoparticles showed the highest degradation efficiency when 30 mg of catalyst and 50 µl of H₂O₂ were used in the DBP solution with the initial concentration of 13 mg l^-1 at pH = 6.5. When the reaction time was 90 min, DBP was degraded 93% for the above optimal parameters. The photocatalytic degradation mechanism of DBP was studied by the gas chromatography-mass spectrometry technique. The result showed that the main degradation intermediates of DBP were ortho-phthalate monobutyl ester, methyl benzoic acid, benzoic acid, benzaldehyde, and heptyl aldehyde when the reaction time was 2 h. DBP and its intermediates were almost completely degraded to CO₂ and H₂O in 12 h in the α-Fe₂O₃/ H₂O₂/UV system.

Removal of aqueous oxalic acid by heterogeneous catalytic ozonation with MnOx/sewage sludge-derived activated carbon as catalysts

MnO_x/sewage sludge-derived activated carbon (MnO_x/SAC) was prepared as catalysts to improve the performance of aqueous oxalic acid degradation by ozonation. The results indicated that MnO_x/SAC had excellent catalytic activity in mineralization of oxalic acid during heterogeneous catalytic ozonation process. MnO_x/SAC with a manganese load of 30% exhibited the strongest catalytic activity under the condition of solution pH3.5, which enhanced the oxalic acid removal from 10.3% to 92.2% in 60min compared with that treated by ozone alone. Increase of catalyst dosage and aqueous ozone concentration was advantageous for oxalic acid removal from water. On the basis of catalyst characterization analysis and the observation of inhibitory effect induced by higher pH, less catalyst dosage as well as the presence of hydroxyl radical scavenger, it was deduced that the reaction mechanism involved both hydroxyl radicals attack and surface reactions.