Wet Peroxide Oxidation Research Articles

Catalytic wet peroxide oxidation of metronidazole over Fe and Mn supported UiO-66 catalysts: Kinetic study

The metronidazole (MNZ) antibiotic is widely used to treat infections caused by anaerobic bacteria and it is difficult to biodegrade in the pharmaceutical wastewaters. In this study, Fe-UiO-66, Mn-UiO-66 and Fe/Mn-UiO-66 catalysts were prepared for the kinetic study of catalytic wet peroxide oxidation (CWPO) degradation of metronidazole in pharmaceutical wastewater. The catalysts were characterized by XRD, FT-IR, N2 adsorption-desorption, SEM, and TGA. The effects of Fe and Mn loading rate, catalyst dosage, MNZ concentrations, calcined temperature of Mn-UiO-66 and Fe/Mn ratio on the CWPO of metronidazole wastewater were systematically studied. Fe-UiO-66 catalysts exhibited better catalytic activity for the CWPO degradation of metronidazole wastewater (XMNZ = 93 %, XH2O2 = 78 %) compared to Mn-UiO-66 catalysts (XMNZ = 20 %, XH2O2 = 30 %). The kinetics study indicates that the CWPO process is fitted for the pseudo-first-order reaction with activation energy of 89.37 kJ/mol and 95.08 kJ/mol obtained on the Fe-UiO-66 and 2Fe/Mn-UiO-66 catalysts, respectively. The supported Fe and Mn UiO-66 catalysts showed good catalytic activity for CWPO of metronidazole which exhibited potential application in the wastewater treatment process.

Preparation and characterisation of alkali-activated blast furnace slag and Na-jarosite catalysts for catalytic wet peroxide oxidation of bisphenol A

ABSTRACT In this study, cost-effective alkali-activated materials made from industrial side streams (blast furnace slag and Na-jarosite) were developed for catalytic applications. The catalytic activity of the prepared materials was examined in catalytic wet peroxide oxidation reactions of a bisphenol A in an aqueous solution. All materials prepared revealed porous structure and characterisation expressed the incorporation of iron to the material via ion exchange in the preparation step. Furthermore, the materials prepared exhibited high specific surface areas (over 200 m2/g) and were mainly mesoporous. Moderate bisphenol A removal percentages (35%–37%) were achieved with the prepared materials during 3 h of oxidation at pH 7–8 and 50°C. Moreover, the activity of catalysts remained after four consecutive cycles (between the cycles the catalysts were regenerated) and the specific surface areas decreased only slightly and no changes in the phase structures were observed. Thus, the prepared blast furnace slag and Na-jarosite-based catalysts exhibited high mechanical stability and showed good potential in the removal of bisphenol A from wastewater through catalytic wet peroxide oxidation.

Carbon Nanomaterials from Polyolefin Waste: Effective Catalysts for Quinoline Degradation through Catalytic Wet Peroxide Oxidation

Quinoline (QN) is highly toxic and carcinogenic and has been detected in soil, groundwater, and biological tissues. Advanced oxidation processes (AOPs) have shown promise to address its degradation in wastewater treatment, with catalytic wet peroxide oxidation (CWPO) being highlighted due to its cost-effectiveness and mild operation. However, developing active and inexpensive catalysts is crucial for CWPO’s effectiveness. Another pressing issue is the accumulation of mixed, dirty plastic solid waste (PSW), particularly polyolefins used in packaging. Although recycling rates have increased, much plastic packaging remains in landfills. However, polyolefins can be converted into carbon-based nanostructured materials (CNMs), such as carbon nanotubes (CNTs), through chemical vapor deposition (CVD) using PSW as a carbon precursor. While many studies focus on CNT preparation, their application is often overlooked. In this context, this work proposes the preparation of CNMs, particularly CNTs, through CVD using a single-stage pyrolysis reactor. Polyolefins (LDPE, HDPE, and PP), both individually and in a mixture simulating PSW, were used as carbon sources. Given a sufficiently high temperature, the desired CNT architecture was successfully synthesized regardless of the starting polymer. These CNMs were then tested as catalysts for CWPO in simulated wastewater containing QN. The results showed a rapid degradation of QN (30–120 min) and high removals of total organic carbon (TOC) and aromatic compounds (75% and >90%, respectively), demonstrating the applicability of PSW-derived CNTs in the CWPO process for QN abatement.

Copper and iron-based monolithic catalysts for phenol Catalytic Wet Peroxide Oxidation (CWPO): Support and iron effects on the catalytic performance

Water is an invaluable resource of our planet, and our lives and those of the future generations rely on it. Phenolic compounds are part of many industries effluents and they are highly toxic and not biodegradable. Therefore, they could be eliminated from water through the Catalytic Wet Peroxide Oxidation (CWPO) reaction. In this work, alumina-supported and cordierite-supported copper and iron-based monolithic catalysts were synthesized and tested in the CWPO of phenol. These structured catalysts were characterized by stereoscopic microscopy, N2 adsorption, XRD, LRS, SEM/EDX and XPS, and their mechanical resistance was analyzed. The effect of both, the support and the presence of iron as a co-active phase on the metal species leaching, and therefore on the catalytic performance, were evaluated. Alumina-supported copper species were more accessible and reducible than cordierite-supported ones and, as a consequence, these rapidly converted the totality of phenol and achieved high mineralization and COD reduction. On the other hand, iron addition as a co-active phase decreased copper leaching in all cases due to Cu-Fe interactions. The bimetallic alumina-supported catalyst exhibited the best catalytic performance with low copper and iron leachings. Consequently, it was tested in a more complex reaction media (tap water). This catalyst resulted promising, converting all the phenol with high mineralization and COD reduction, although suffering some copper and iron leaching.

Hybrid multi-core shell magnetic nanoparticles for wet peroxide oxidation of paracetamol: Application in synthetic and real matrices

Clean water availability is becoming a matter of global concern in the last decades. The responsible entities for wastewater treatment do not have the proper facilities to deal with a wide range of pollutants. Special attention should be given to emerging contaminants, whose presence in water bodies may cause adverse effects on the aquatic ecosystem and human health. Most studies in the literature do not consider the development of their solution in real matrices, which can hinder the applicability of the explored alternative in the real scenario. Therefore, in this work, we demonstrate the applicability of hybrid magnetic nanoparticles for removing paracetamol (PCM) from simulated and real matrices by catalytic wet peroxide oxidation (CWPO). To achieve carbon coating, the nanoparticles were prepared via the traditional route (resorcinol/formaldehyde, CoFe@CRF). A new methodology was also considered for synthesizing thin-layered carbon-coated magnetic nanoparticles (phloroglucinol/glyoxalic acid, CoFe@CPG). TEM images revealed a multi-core shell structure formation, with an average carbon layer size of 7.8 ± 0.5 and 3.2 ± 0.3 nm for resorcinol/formaldehyde and phloroglucinol/glyoxalic acid methodology, respectively. Screening the materials’ activity for PCM oxidation by CWPO revealed that the nanoparticle prepared by phloroglucinol/glyoxalic acid methodology has higher performance for the degradation of PCM, achieving 63.5% mineralization after 24 h of reaction, with similar results for more complex matrices. Iron leaching measured at the end of all reactions has proven that the carbon layer protects the core against leaching.

Metal-Organic Frameworks/Graphdiyne/Copper Foam Composite Membranes for Catalytic Applications.

Graphdiyne (GDY) with a three-dimensional network structure was synthesized on a copper foam (CF) via an in situ Glaser-Hay coupling reaction. A metal-organic framework/GDY composite membrane was designed and synthesized for the first time. CF serves as a template and catalyst for the directed polymerization of GDY membranes. The catalytic activities of HKUST-1/GDY/CF membrane in wet peroxide oxidation of phenol, oxidation of benzyl alcohol, and ring opening of epoxide were studied. The composite membrane has the advantages of appropriateness for continuous operation, simple use process, easy recycling, high catalytic efficiency, etc. It was found that the incorporation of GDY can facilitate electron transfer and effectively improve the catalytic activity of HKUST-1 in membrane catalysis.

Catalytic wet peroxide oxidation with in-situ generated H2O2: An efficient strategy for improving the stability of metal-organic framework catalysts

Although catalytic wet peroxide oxidation (CWPO) may offer an efficient method for wastewater treatment, the use of metal-organic framework (MOF) catalysts for the CWPO reaction in the presence of H2O2 is challenging because the MOF structure is highly vulnerable to water and/or oxidizing agents. Herein, a range of M-1,3,5-benzenetricarboxylate (BTCs) (M = Fe, Co, Mn, and Cu) were prepared, and their catalytic activities in the CWPO of methyl orange (MO) were evaluated. To examine the stability of the M-BTCs under different reaction conditions, the CWPO reaction was performed with ready-made H2O2 (CWPO-I) or in-situ generated H2O2 using H2 and O2 (CWPO-II). In the latter, Pd was supported onto an M-BTC (Pd/M-BTC). The CWPO-I reaction rate was significantly affected by the metal nodes of the M-BTC, with the Fe-BTC catalyst showing the fastest MO degradation rate. However, regardless of the type of metal node, the M-BTC catalysts underwent significant decomposition during the CWPO-I reaction, leading to a considerable decrease in their textural properties. This result suggests that the M-BTC structure collapsed due to attack by the hydroxyl radicals generated during the reaction. Therefore, the activity of the regenerated Fe-BTC catalyst significantly decreased to 40% of that of the fresh catalyst. In contrast, the catalyst stability in CWPO-II outperformed that in CWPO-I. The Pd/Fe-BTC catalyst exhibited a moderate decrease in activity owing to the gradually reduced surface area of the catalyst during the recycling runs, and the crystallinity of Fe-BTC was preserved. Moreover, the content, particle size, and electronic properties of Pd supported on Fe-BTC showed little change after the reaction. These results demonstrate that the use of in-situ generated H2O2 is superior for impeding the catalyst deactivation caused by structural deformation of the MOF.

Influence of the aqueous matrix on the degradation of cyanotoxins by CWPO: A study on the Iberian Peninsula freshwaters

The increasing occurrence of toxic cyanobacterial blooms worldwide represents a critical health and environmental risk. Catalytic wet peroxide oxidation (CWPO) has emerged as an efficient and environmentally friendly technology for the removal of cyanotoxins in water. Nevertheless, its effectiveness has just been demonstrated in deionized water or simple synthetic aqueous matrices. In this work, the effect of the different components of the aqueous matrix on the CWPO of cyanotoxins was deeply evaluated considering the widespread properties of the Iberian Peninsula freshwaters. The presence of Cl-, HCO3- and SO42- ions reduced the oxidation rate of cylindrospermopsin (CYN) up to 70–80% at the highest concentrations tested (2000, 250 and 500 mg L−1 for Cl-, HCO3- and SO42-, respectively) due to their hydroxyl radical scavenging capacity. The presence of natural organic matter (NOM) resulted in a similar outcome (oxidation rate reduction up to 90% at the highest concentration tested, 20 mg L−1), but in this case due to the consumption of hydroxyl radicals in competition with CYN oxidation. The presence of NO3- and H2PO4- did not show any significant effect on CYN oxidation. Similarly, the presence of cyanobacteria (Chrysosporum ovalisporum, 50 µg chlorophyll-a L−1) did not appreciably affect the CYN oxidation rate. These results were consistent with those obtained by evaluating the impact of real aqueous matrices from drinking water treatment plants (DWTPs) located in Castilla y León and Extremadura regions (Spain) on CWPO performance. This knowledge is key to the implementation of the technology for the treatment of surface waters affected by toxic cyanobacterial blooms.

Promoted wet peroxide oxidation of chlorinated volatile organic compounds catalyzed by FeOCl supported on macro-microporous biomass-derived activated carbon

Chlorinated volatile organic compounds (CVOCs) are a recalcitrant class of air pollutants, and the strongly oxidizing reactive oxygen species (ROS) generated in advanced oxidation processes (AOPs) are promising to degrade them. In this study, a FeOCl-loaded biomass-derived activated carbon (BAC) has been used as an adsorbent for accumulating CVOCs and catalyst for activating H2O2 to construct a wet scrubber for the removal of airborne CVOCs. In addition to well-developed micropores, the BAC has macropores mimicking those of biostructures, which allows CVOCs to diffuse easily to its adsorption sites and catalytic sites. Probe experiments have revealed HO• to be the dominant ROS in the FeOCl/BAC + H2O2 system. The wet scrubber performs well at pH 3 and H2O2 concentrations as low as a few mM. It is capable of removing over 90% of dichloroethane, trichloroethylene, dichloromethane and chlorobenzene from air. By applying pulsed dosing or continuous dosing to replenish H2O2 to maintain its appropriate concentration, the system achieves good long-term efficiency. A dichloroethane degradation pathway is proposed based on the analysis of intermediates. This work may provide inspiration for the design of catalyst exploiting the inherent structure of biomass for catalytic wet oxidation of CVOCs or other contaminants.

Polyolefin-derived carbon nanotubes as magnetic catalysts for wet peroxide oxidation of paracetamol in aqueous solutions

This work deals with developing feasible valorization technologies to prepare carbon nanotubes (CNTs) from plastic solid waste and demonstrate their application in catalytic wet peroxide oxidation (CWPO). CNTs were synthesized by catalytic chemical vapor deposition (CCVD) at 850 ºC, considering low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) as carbon precursors representative of urban plastic solid waste. Iron oxide nanoparticles supported in alumina, previously synthesized by sol-gel, were used as catalysts in the CCVD process. TEM micrographs allow us to determine 41 nm as the average outer diameter of the CNTs and to visualize magnetic iron nanoparticles (ca. 10 nm) embedded inside the CNTs (ca. 6.4 % of content measured as ashes). These magnetic nanoparticles were kept in the CNT structure even after the purification of the CNTs with sulphuric acid, allowing to obtain magnetic CNTs. All purified and non-purified CNTs prepared from the polyolefins were assessed as catalysts in CWPO of paracetamol (PCM), used as a model pharmaceutical contaminant in water at CPCM,0 = 100 μg mL−1 (CH2O2,0 = 472 μg mL−1, CCNT = 2.5 g L−1, pH0 = 3.5 and T = 80 °C). The concentrations of PCM, H2O2, aromatic and total phenolic compounds were monitored for 24 h. All CNTs showed catalytic activity, allowing the complete degradation of PCM at 6 h of reaction time. The stability and reusability of materials are tested and proved in CWPO.

Occurrence and characteristics of microplastics in surface water and sediment of Zayandeh-rud river, Iran

Background: Zayandeh-rud river is the most important river in the central regions of Iran and the present study aimed to provide new insights into microplastics (MPs) pollution in surface water and sediments of this river. Methods: Water and sediment samples were collected in July 2021 from 19 sampling sites along the river. Organics matters were removed from the samples by wet peroxide oxidation (WPO), and MPs were extracted by floatation in ZnCl2 -saturated salt and filtration on a polytetrafluoroethylene (PTFE) membrane filter. Trapped MPs on the filter were counted and qualified by a stereomicroscope. Results: MPs were found in 13 sites from 19 sampling sites along the river. The minimum and maximum levels of MPs in water samples were 0 and 51±16.5 particles/m3 , respectively. MPs also were detected in the sediments of all sampling sites except the first two sampling sites (the maximum level was 58±25.9 particles/kg as dry sediment). Fragments were the most common shape of MPs in both water and sediment samples. 72.3% of MPs detected in water samples were 1-5 mm in size, while this percentage for sediment was 49.2%. The five main polymer types found in water and sediment samples were polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC). Conclusion: These levels of MPs in the water and sediments of Zayandeh-rud river and longtime persistence of plastics in the environment is a significant threat to environmental and human health and need serious attention to restrict MPs release into the river.

Porous graphitized carbon-supported FeOCl as a bifunctional adsorbent-catalyst for the wet peroxide oxidation of chlorinated volatile organic compounds: Effect of mesopores and mechanistic study

Wet scrubbing coupled with adsorption-enhanced heterogeneous advanced oxidation processes (AOPs) are promising approaches to the treatment of chlorinated volatile organic compounds (CVOCs). However, microporous activated carbon-based adsorbents and catalyst supports have the disadvantage of difficult molecule diffusion. Herein, we have demonstrated that porous graphitized carbon (PGC) allowed faster intra-particle diffusion of organic molecules due to its well-developed mesoporous structure. Therefore, a wet scrubbing system containing H2O2 and a PGC-supported FeOCl catalyst has been developed to effectively remove gaseous dichloroethane, trichloroethylene, dichloromethane and chlorobenzene. The scrubber performed well at pH 3.0 using a FeOCl/PGC dosage of 0.2 g/L and initial H2O2 concentration of 40 mM. Its good long-term performance was achieved by replenishing H2O2 to maintain a suitable concentration. The degradation pathways of dichloroethane have been proposed using a combination of intermediate analysis and density functional theory calculations. PGC-supported catalysts may be desirable bifunctional adsorbent-catalyst materials for wet scrubbing of CVOCs.

Use of Fe and Al Containing Electrocoagulation Sludge as an Adsorbent and a Catalyst in Water Treatment

In this study, three different electrocoagulation (EC) sludges were studied as an adsorbent (removal of humic acids) and as a catalyst [catalytic wet peroxide oxidation (CWPO) of bisphenol A (BPA)]. The sludges originated from electrocoagulation process in which aluminum (Al) and iron (Fe) electrodes were used for the treatment of mining industry wastewater. All the materials were used as dried sludge and calcined material. The stability of these materials was studied in neutral and alkaline conditions with analysis of the leached iron content in solution. Based on the EC sludge characterization with X-ray fluorescence (XRF), X-ray diffractometer (XRD), and diffuse-reflectance infrared Fourier transform (DRIFT) spectroscopy different forms of Fe occurring in EC sludges were found. The Brunauer–Emmett–Teller (BET) method showed reduced surface area after calcination process. Stability of the sludges was studied in neutral conditions, and the amount of iron leaching was low (<1.4 ppm). Adsorption experiments showed that the removal of humic acids (measured as total organic carbon) was over 50% in all tested materials in the pH range of 3–9, and over 92% with the S3 calcined material in all studied pH range. The calcined samples were catalytically more active than raw material in CWPO of BPA. The highest removal of BPA was 85% over calcined sludge. Therefore, calcined EC sludges are suitable materials for catalyst and adsorbent use. The main novelty of this paper was the finding of sludge modification in the EC process of water treatment through different electrode material and current density. This modification can be made in EC water treatment process, and it may provide low-cost materials to different utilization of EC sludge.

Abatement of 1,2,4-Trichlorobencene by Wet Peroxide Oxidation Catalysed by Goethite and Enhanced by Visible LED Light at Neutral pH

Abatement of 1,2,4-Trichlorobencene by Wet Peroxide Oxidation Catalysed by Goethite and Enhanced by Visible LED Light at Neutral pH

Evidence of microplastics in leachate of Randegan landfill, Mojokerto City, Indonesia, and its potential to pollute surface water

About 80–90 tons municipal solid waste (MSW) in Mojokerto City, Indonesia, is disposed of into Randegan landfill daily. The landfill was facilitated with a conventional leachate treatment plant (LTP). The plastic waste component in the MSW, which is 13.22 % weight, possibly contaminates leachate with microplastics (MPs). This research aims to determine the presence of MPs in leachate of the landfill, its characteristics, and the removal efficiency of the LTP. The potential of leachate as MP pollutant source to surface water was also discussed. Raw leachate samples were collected from the LTP inlet channel. Leachate samples were also taken from each LTP's sub-units. Leachate collection was performed two times using a 2.5 L glass bottle during March 2022. The MPs were treated using Wet Peroxide Oxidation method, and filtered using PTFE membrane. MP size and shape were determined using a dissecting microscope with 40–60 x magnifications. The polymer types in the samples were identified using Thermo Scientific™ Nicolet™ iS™ 10 FTIR Spectrometer. The average MP abundance in raw leachate was 9.00 ± 0.85 particles/L. MP shape in the raw leachate was dominated by fiber (64.44 %), followed by fragment (28.89 %), and film (6.67 %). The majority of the MPs were of black color (53.33 %). Abundance of 350 - <1000 μm sized MPs was the highest (64.44 %) in the raw leachate, followed by those of 100–350 μm (31.11 %), and 1000–5000 μm (4.45 %). MP removal efficiency of the LTP was 75.6 %, leaving <100 μm fiber shaped MP residuals of 2.20 ± 0.28 p/L in the effluent. Based on these results, effluent of the LTP is considered potential as MP contamination source to surface water.

Preliminary study on the occurrence of microplastics in a local sewage treatment plant

Recent studies have found that sewage treatment plants are potential source of microplastics pollution to its receiving freshwaters, which potentially affect freshwater ecosystems. This study aimed to investigate the occurrence of microplastics in sewage treatment plant, i.e., outlet of a primary clarifier and within an activated sludge system. A digestion method (oxidation digestion using Fenton’s reagent coupled with wet peroxide oxidation technique) followed by microplastics extraction were attempted. Microplastics were detected, through instrumental characterizations, in all sewage samples in this study with microplastics found in the primary clarifier included polyamide, polytetrafluoroethylene and polyethylene terephthalate, while microplastics in the activated sludge system were polyamide, polystyrene and polyvinyl chloride. Results indicated that the sewage treatment plant successfully reduced microplastics from the primary clarifier to the activated sludge system by retaining bigger sizes of microplastics during early treatment stages of the system.

Insights on the removal of the azole pesticides included in the EU Watch List by Catalytic Wet Peroxide Oxidation

Insights on the removal of the azole pesticides included in the EU Watch List by Catalytic Wet Peroxide Oxidation

Selective denitrification of simulated oily wastewater by oxidation using Janus-structured carbon nanotubes

The intense industrial development has resulted in several consequences for human and environmental health, including the increased discharge of oily products in water bodies. Oily products are widely used in industry, often bearing an associated high cost. Finding alternatives to treat oily wastewater aiming at recovering oily and water phases is an approach allowing recovery of products of economic interest. In this work, Janus-like carbon nanotubes (CNTs) were synthesized by varying the feed time of acetonitrile and ethylene, respectively, as nitrogen/carbon and carbon precursors in a chemical vapor deposition (CVD) approach. The CVD approach allowed the synthesis of completely undoped, completely doped and partially doped CNTs with a Janus structure. The CNTs were then tested as catalysts for the selective oxidation of 4-nitrophenol (4-NP) contained in a simulated oily wastewater (2,2,4-trimethylpentane/water (O/W) = 1:9, volume basis) by catalytic wet peroxide oxidation (CWPO). The CWPO experiments were conducted for 24 h, 80 °C, 2.5 g L−1 of catalyst, and the stoichiometric concentration of H2O2 (3.6 g L−1) for the degradation of 4-NP (1 g L−1). The same conditions were kept for experiments conducted under a biphasic system. The catalysts bearing a Janus-like structure were demonstrated to be more effective in CWPO experiments in aqueous-only and biphasic systems for the abatement of 4-NP.

Cu-based perovskite as a novel CWPO catalyst for petroleum refining wastewater treatment: Performance, toxicity and mechanism

For the first time, Cu-based perovskite oxides were used as catalysts to treat highly toxic and refractory petroleum refining wastewater based on catalytic wet peroxide oxidation (CWPO) technology. Perovskite La2CuO4 was synthesized by sol-gel method. A series of characterizations showed that the synthesized catalyst particles are tetragonal phase perovskite structure. The experimental results showed that under the conditions of catalyst dosage of 0.75 g, temperature of 100 ℃ and reaction time of 30 min, the COD removal rate was 89.58 %, the TOC removal rate was 87.38 %. The morphology and structure of the catalyst before and after the reaction proved that the catalyst has strong stability and catalytic activity. The components of raw water, Wet Air Oxidation (WAO) effluent and CWPO effluent were compared and analyzed by Gas Chromatography-Mass Spectrometry (GC-MS), and the possible mechanism and path of WAO and CWPO degradation of petroleum refining wastewater were further explored. The changes of Cu components in La2CuO4 before and after CWPO reaction and the transformation of lattice oxygen and adsorbed oxygen were analyzed by X-ray Photoelectron Spectroscopy (XPS). The involvement of Cu (Ⅱ) /Cu (Ⅰ) in the activation of H2O2 was speculated. Finally, the biotoxicity of raw water, WAO effluent and CWPO effluent was predicted. The results provide reference value for the application of catalyst La2CuO4 in various petrochemical wastewater.

Distribution and removal mechanism of microplastics in urban wastewater plants systems via different processes

Microplastic pollution threatens water systems worldwide. As one of the most important parts of city wastewater treatment, wastewater treatment plants are not only microplastics interception barriers but also emission sources. Water samples were collected from each sewage treatment plant stage and sludge from the sludge dewatering room. Microplastics were extracted using wet peroxide oxidation and flotation, and the abundance, size, shape, and polymer type of microplastics were detected. Basis on the results, the influence of each process on the removal rate and characteristics of microplastics under the same influent source was analysed. The influent microplastic concentration in this study was 32.5 ± 1.0 n/L, which rapidly decreased after treatment. The removal rates of the sequencing batch reactor activated sludge, cyclic activated sludge, and anaerobic anoxic oxic technologies were 73.0%, 75.6%, and 83.9%, respectively. Most microplastics were transported to the sludge, and the concentration of microplastics in dehydrated sludge was 27.2 ± 3.1 n/g. Microplastics removal occurred primarily during the primary and secondary stages. Disposal processes, settling time, and process design affected wastewater treatment plant microplastic removal rates at each stage. Significant differences in microplastic characteristics were observed at each stage, with the most abundant being fragment shaped, particle sizes of 30–100 μm, and black in colour. Sixteen polymer types were identified using a Raman spectrometer. The predominant polymers are polypropylene, polyethylene, and polyethylene terephthalate. This study demonstrates that optimising the process design of existing wastewater treatment plants is crucial for the prevention and control of microplastic pollution. It is suggested that the process settings of contemporary wastewater treatment plants should be studied in depth to develop a scientific foundation for avoiding and managing microplastic pollution in urban areas.