Water Treatment Technologies Research Articles

Innovative Photocatalytic Reactor for Sustainable Industrial Water Decontamination: Utilizing 3D-Printed Components and Silica-Titania Trilayer Coatings

Industrial activities generate enormous quantities of polluted effluents, necessitating advanced methods of wastewater treatment to prevent potential environmental threats. Thus, the design of a novel photocatalytic reactor for industrial water decontamination, purification, and reuse is proposed as an efficient advanced oxidation technology. In this work, the development of the active reactor components is described, utilizing a two-step sol–gel technique to prepare a silica-titania trilayer coating on 3D-printed polymeric filters. The initial dip-coated SiO2 insulator further protects and enhances the stability of the polymer matrix, and the subsequent TiO2 layers endow the composite architecture with photocatalytic functionality. The structural and morphological characteristics of the modified photocatalytic filters are extensively investigated, and their performance is assessed by studying the photocatalytic degradation of the Triton X-100, a common and standard chemical surfactant, presented in the contaminated wastewater of the steel metal industry. The promising outcomes of the innovative versatile reactor pave the way for developing scalable, cost-effective reactors for efficient water treatment technologies.

Autonomous real-time control for membrane capacitive deionization

Artificial intelligence has been employed to simulate and optimize the performance of membrane capacitive deionization (MCDI), an emerging ion separation process. However, a real-time control for optimal MCDI operation has not been investigated yet. In this study, we aimed to develop a reinforcement learning (RL)-based control model and investigate the model to find an energy-efficient MCDI operation strategy. To fulfill the objectives, we established three long-short term memory models to predict applied voltage, outflow pH, and outflow electrical conductivity. Also, four RL agents were trained to minimize outflow concentration and energy consumption simultaneously. Consequently, actor-critic (A2C) and proximal policy optimization (PPO2) achieved the ion separation goal (<0.8 mS/cm) as they determined the electrical current and pump speed to be low. Particularly, A2C kept the parameters consistent in charging MCDI, which caused lower energy consumption (0.0128 kWh/m3) than PPO2 (0.0363 kWh/m3). To understand the decision-making process of A2C, the Shapley additive explanation based on the decision tree model estimated the influence of input parameters on the control parameters. The results of this study demonstrate the feasibility of RL-based controls in MCDI operations. Thus, we expect that the RL-based control model can improve further and enhance the efficiency of water treatment technologies.

In Situ Production of Hydroxyl Radicals via Three-Electron Oxygen Reduction: Opportunities for Water Treatment.

The electro-Fenton (EF) process is an advanced oxidation technology with significant potential; however, it is limited by two steps: generation and activation of H2O2. In contrast to the production of H2O2 via the electrochemical two-electron oxygen reduction reaction (ORR), the electrochemical three-electron (3e-) ORR can directly activate molecular oxygen to yield the hydroxyl radical (⋅OH), thus breaking through the conceptual and operational limitations of the traditional EF reaction. Therefore, the 3e- ORR is a vital process for efficiently producing ⋅OH in situ, thus charting a new path toward the development of green water-treatment technologies. This review summarizes the characteristics and mechanisms of the 3e- ORR, focusing on the basic principles and latest progress in the in situ generation and efficient utilization of ⋅OH through the modulation of the reaction pathway, shedding light on the rational design of 3e- ORR catalysts, mechanistic exploration, and practical applications for water treatment. Finally, the future developments and challenges of efficient, stable, and large-scale utilization of ⋅OH are discussed based on achieving optimal 3e- ORR regulation and the potential to combine it with other technologies.

Construction of an S-scheme electron transfer channel in Cu0/CuFe2O4 magnetic plate column reactor for the LEV degradation: New strategy of visible Photo-Fenton system application

The complicated loading process and easy falling off of powder catalysts still restrict the wide application of Photo-Fenton technology in practical water treatment. In this study, a magnetic fixed film plate column water treatment equipment is designed as a visible Photo-Fenton reactor to remove levofloxacin (LEV). The effect of magnetic force can ensure that the catalyst is firmly fixed, and the multi-level shallow column plate structure achieves full contact and efficient reaction between the catalyst and wastewater. Simultaneously, the Cu0/CuFe2O4 (STCCF) utilizes Cu0 to construct an S-scheme electron transfer channel, which improves the separation efficiency of photo-generated carriers and provides sufficient photo-generated electrons for the reduction of Fe (Ⅲ) and Cu (Ⅱ). The pseudo-first-order reaction kinetic constant k for the degradation of LEV in the visible Photo-Fenton system is 0.0349 min−1, which is 15.9 times that of the photocatalytic system and 4.8 times that of the Fenton system. After continuous operation for 72 h, the magnetic fixed film plate column reactor can still remove more than 90 % of LEV and 82 % of COD in the secondary effluent of simulated antibiotic pharmaceutical wastewater treatment process, and the effluent is stable and meets the standard. The magnetic fixed film plate column reactor can be used for advanced treatment of antibiotic pharmaceutical wastewater. This study provides a new insight into the application of the Photo-Fenton process.

Exploring Plasma-Based Water Treatment Technology to Achieve a Cleaner Future

Plasma as the fourth state of matter otherwise referred to as ionized gases has gained significant attention recently due to its vast applications across different fields of research such as the medical, the industrial, nanomaterials, etc. The role of clean water for sustainability is important. However, water contaminants have remained a big challenge especially in Nigeria and Africa in general, making it difficult to gain access to clean water, resulting to inadequate clean water supply for many communities. This review work explores the applications of non-thermal plasmas for effective water treatment. It is and upshot from previous studies on the applications of plasma for water treatment and has shown the capability of this method to effectively degrade complex pollutants and heavy metals, etc. as an environmentally friendly approach without the use of harmful chemical addictives like chlorine. Plasma-based method for water treatment is significant for environmental sustainability and general health of the public. This review will be useful for state actors, industries and further research is recommend to assess the economic impacts of plasma-based method of water treatment.

Overview of the low-cost technologies for household water treatment in developing countries

ABSTRACT This study explored various low-cost water treatment technologies that are used to minimize levels of pathogens and contaminants in raw water. The paper focused on techniques such as cloth filtration, boiling, chlorination, and solar water disinfection. In the communities, cloth filtration is applied as the initial step of treating raw water with the proper choice of cloth fabrics followed by either boiling, chlorination or solar water disinfection. In low-income communities with unclean burning fuel sources, boiling was found to be the preferred method. Chlorination was also a popular technique associated with the challenges of low or high levels of free chlorine at the point of use and disinfection by-products. Solar water disinfection required optimal residence time and detection sensors for microorganism inactivation. Overall, the paper provided valuable insights into the different low-cost water treatment techniques that are commonly used for household applications, particularly in developing countries.

Encapsulation hierarchical bimetallic oxide with flexible electrospinning carbon nanofibers for efficient capacitive deionization

Water scarcity, an intensifying issue, has spurred extensive research into the development of sophisticated freestanding pseudocapacitive electrode materials. Characterized by their precise morphology, intricate mechanics, and superior desalination capabilities, these materials are revolutionizing water treatment technologies. However, their broad adoption is hampered by complex fabrication processes and the necessity for various unique components. Herein, the paper introduces a streamlined method combining electrospinning and carbonization to produce a freestanding nitrogen-doped carbon nanofiber encapsulating manganese cobalt oxide (MCO) nanoparticles for desalination purposes. The approach significantly enhances interfacial interactions, mitigates volume shifts during sodium ion adsorption and desorption, and strengthens interfacial stability. Benefiting from its structural and compositional merits, the optimal MCO-1.0 electrode showcases exceptional electrochemical attributes. It achieves an impressive desalination efficiency (34.68 mg g−1), swift capacitive deionization rate (0.58 mg g−1 min−1), and superior cyclic durability. The study enhances our understanding of freestanding carbon fibers encapsulated with metal oxide nanoparticles, a key step toward developing robust electrodes for industrial applications.

ANALYSIS OF THE EFFICIENCY OF TRADITIONAL TECHNOLOGIES OF WATER PREPARATION OF THE KREMENCHUK RESERVOIR OF THE DNIPRO RIVER TO ENSURE DRINKING NEEDS

An analysis of the efficiency of the surface water treatment systems of the Dnipro reservoirs when their quality is changed to ensure the normative indicators of the quality of drinking water were carried out. The study of the effectiveness of traditional water treatment technologies was carried out by analyzing the results of laboratory studies of source and drinking water at the Dnipro water treatment plant with water intake from the Kremenchuk Reservoir (data from the Svitlovodsk Water and Sewage Services (SWS) of the Regional Municipal Production Enterprise (RMPE) of the Dnipro-Kirovograd), establishing correlations of quality indicators and assessing the state of water resources by the requirements of water legislation. The treatment plants of the Dnipro water supply station are not designed to treat water with a high content of biogenic substances during active phytoplankton vegetation, and under such conditions, increased doses of preliminary chlorination are used. As a result, water is polluted with residual chlorine and organochlorine. An increase in the dose of aluminum-containing coagulants in the corresponding period leads to an increase in the aluminum content in drinking water to the limit of the normative value (0,5 mg/dm3). According to the results of research in drinking water, turbidity was found to be 1,4 higher and permanganate oxidizability 1,3 higher than the standard content; excesses of color, iron, and residual chlorine content were found only sporadically and were on average within the upper limits of normative values. Correlation analysis (Pearson and Spearman correlations methods) of the influence of temperature on the following hydrometric, chemical, and physical factors was carried out: changes in turbidity, color, and changes in the concentration of total iron and ammonia. The analysis confirmed the visual connection of oxygen with temperature and water level and the influence of factors on oxygen concentration. The practical aspects of phytoplankton extraction during water intake from Dnipro reservoirs and water treatment at stations have gained further scientific justification.

Preparation magnetic graphene oxide/diethylenetriamine composite for removal of methylene blue from aqueous solutions

Graphene oxide (GO) and its derivatives have several applications in many areas such as environmental and energy materials, water treatment and biomedical technologies. Because of having various polar groups on its surface, GO is considered as an excellent adsorbent. However, for many applications such as adsorption of pollution from aqueous solutions, chemical functionalization of graphene oxide is often a necessary requirement. In the present study, a new composite from graphene oxide, diethylenetriamine (DETA) and silica coated MnFe2O4 nanoparticles (GO/DETA/MnFe2O4@SiO2) was prepared. The structure, thermal stability and magnetic properties of the composite were studied by FT-IR, XRD, SEM, EDS, VSM and TGA spectroscopic methods. The prepared composite showed magnetic property with a saturation magnetization of 3.0 emu/g. The adsorption properties of GO/DETA/MnFe2O4@SiO2 composite for methylene blue (MB) in aqueous solution were studied using batch method. The effects of important parameters on the surface adsorption process of MB, including pH, contact time, adsorbent dosage and initial dye concentration were investigated. The adsorption isotherm was in accordance with Langmuir model showing surface homogeneity of the adsorbent. According to the Langmuir analysis, the maximum adsorption capacity (qm) of GO/DETA/MnFe2O4@SiO2 composite for MB was found to be 243.91 mg/g. The kinetic studies showed that the adsorption was pseudo first-order process. In addition, the thermodynamic studies indicated the adsorption was spontaneous and endothermic process.

Synthesis of aminopropyl triethoxysilane/melamine incorporated superhydrophilic membranes for simultaneous removal of oil, metals, and Salt ions from produced water

Water treatment has turned out to be more important in most societies due to the expansion of most economies and to advancement of industrialization. Developing efficient materials and technologies for water treatment is of high interest. Thin film nanocomposite membranes are regarded as the most effective membranes available for salts, hydrocarbon, and environmental pollutants removal. These membranes improve productivity while using less energy than conventional asymmetric membranes. Here, the polyvinylidene fluoride (PVDF) membranes have been successfully modified via dip single-step coating by silica-aminopropyl triethoxysilane/trimesic acid/melamine nanocomposite (Si-APTES-TA-MM). The developed membranes were evaluated for separating the emulsified oil/water mixture, the surface wettability of the membrane materials is therefore essential. During the conditioning step, that is when the freshwater was introduced, the prepared membrane reached a flux of about 27.77 L m−2 h−1. However, when the contaminated water was introduced, the flux reached 18 L m−2 h−1, alongside an applied pressure of 400 kPa. Interestingly, during the first 8 h of the filtration test, the membrane showed 90 % rejection for ions including Mg2+, and SO42− and ≈100 % for organic pollutants including pentane, isooctane, toluene, and hexadecane. Also, the membrane showed 98 % rejection for heavy metals including strontium, lead, and cobalt ions. As per the results, the membrane could be recommended as a promising candidate to be used for a mixture of salt ions, hydrocarbons, and mixtures of heavy metals from wastewater.

The Integrating Impacts of Extreme Weather Events and Shrimp Farming Practices on Coastal Water Resource Quality in Ninh Thuan Province, Vietnam

Ninh Thuan is a coastal province in the central region of Vietnam and is characterized by a climate that is the hottest and driest in the country. Vietnam is also one of the top five countries most vulnerable to the effects of climate change worldwide. The objective of this study was a thorough evaluation of the quality of water supply sources and the impacts of water effluents from shrimp farms in Ninh Thuan province. The comprehensive evaluation was based on an understanding of the water–wastewater cycle employed in coastal shrimp cultivation. We combined qualitative and quantitative analyses in undertaking this study. Secondary data of groundwater and coastal water from the local periodic water quality monitoring program and national technical regulations were collected in the qualitative approach. We also integrated participatory rural appraisal techniques and field observations to understanding shrimp cultivation and the environmental and social impacts of shrimp farm effluents. The quantitative assessment consisted of measuring groundwater and wastewater contamination from shrimp ponds. As a result, four main reasons for water pollution issues were determined including extreme weather events, shrimp cultivation practices, degraded infrastructure, and mismanagement by local governance. Shrimp cultivation practices (feeding, using chemicals) have resulted in elevated levels of suspended solid (TSS, total Coliform), organic and carbon matter (BOD5, COD), and excessive nutrients (total Nitrogen, NO2-N, NO3-N, PO4-P). According to a local monitoring program, the coastal water and groundwater have experienced nutrient pollution. Groundwater sampling near the shrimp farms identified salinization elevated levels of Coliform from local domestic sewage sources. This study resulted in an integrated approach that evaluated the combined effects of extreme weather events and shrimp farming practices on the quality of coastal water. Also, the finding can be useful in recommending remedial water treatment technologies as a follow-on phase.

Eco-friendly synthesis and application of NH2-COOH functionalized Fe3O4@graphite carbon microballs in heavy metal removal

Heavy metal pollution in wastewater is quite challenging for the environment. This study pioneers the synthesis of a novel adsorbent, amine-acid functionalized Fe3O4 decorated carbon micro-balls (NH2-COOH/Fe3O4@CMBs) via hydrothermal process and controlled thermal treatment under nitrogen atmosphere, utilizing eco-friendly resource glucose as a carbon precursor. The formation of cubic Fe3O4 nanoparticles and crystalline graphite within a carbon core-shell structure is confirmed. NH2-COOH/Fe3O4@CMBs show a porosity conducive to ion exchange in the range of 100–300 nm via FE-SEM, exhibiting a significant surface area of 494 m²/g with optimal pore volume. Within the carbon matrix, H2-TPR affirms the robust integration of Fe3O4, essential for high adsorption rates. In practical applications, NH2-COOH/Fe3O4@CMBs demonstrate exceptional performance, removing ∼ 99 % of Pb2+ ions in 30 min., showcasing an impressive adsorption capacity of 360 mg/g. The rapid and potent adsorption is attributed to the electron-rich graphite layers and the presence of abundant chelating sites. This research introduces NH2-COOH/Fe3O4@CMBs as a commercially viable and environmentally responsible solution for the removal of hazardous heavy metals from wastewater. Scientific understanding of adsorptive material not only advances but also offers a tangible approach to mitigate a pressing public health concern, marking a significant stride towards sustainable water treatment technologies.

The application of diatomic catalysts in advanced oxidation Fenton-like water treatment technology:A mini review

In the past few years, there has been a widespread utilization of diatomic catalysts in the catalysis sector because of their distinct benefits. In this review, we specify the application of diatomic catalysts based on carbon and carbon nitride in the Fenton-like field. This paper focuses on the synthesis and characterization of homonuclear and heteronuclear diatomic catalysts and methods to improve the catalytic performance by optimizing d-band structure, tuning charge transfer, and constructing spin states. There is no doubt that diatomic catalysts have bright prospects in the Fenton-like field.

Assessing the physicochemical properties of surface/groundwater of Sudhnoti district, Azad Jammu and Kashmir: Impacts on lindane degradation by photocatalysis

Since polluted water deteriorates the health of human beings and other animals, healthy society and environmental sustainability demand for clean and safe water. The presence of contaminants, and imbalance of common physicochemical parameters significantly disturb the quality of water. Taking the importance of clean and safe water into account, this study investigated fourteen physicochemical parameters of hand pump and open well water (main drinking water sources) from fifteen places of district Sudhnoti, Azad Jammu and Kashmir (AJK). The mean values of pH, electrical conductivity (EC), alkalinity, hardness and total dissolved solids (TDS) were 7.6, 349.9 μS/cm, 144, 152 and 190 mg/L, respectively. The mean concentration of Na+, K+, Ca2+, Mg2+, HCO3−, Cl−, SO42− and NO3− was found to be 9.5, 0.96, 9.9, 44.2, 144, 16.8, 8.1 and 6.67 mg/L, respectively. The turbidity as well as the concentration of CO32− was found below the detectable level in all water samples tested. Interestingly, all the studied physicochemical parameters had lower values than the maximum permissible level recommended by the world health organization (WHO) for drinking water. Eventually, the impacts of the studied physicochemical parameters, particularly anions and cation, on the efficiency of water treatment technology for real field application were discussed. The results revealed that physicochemical parameters of the groundwater of Sudhnoti, AJK had a slight effect on the degradation efficiency of one of the most widely used pesticides, lindane, in water by using ultraviolet–visible titanium oxide/hydrogen peroxide (UV–Vis)/TiO2/H2O2) and ultraviolet–visible/titanium oxide persulfate photocatalysis. Of note, the quality of hand pump and open well water which are the main drinking water sources of district Sudhnoti, AJK was found to be fit for drinking and other domestic purposes as well as for the ecosystem.

Photoelectrode materials for photo-assisted electrochemical water treatment

Mohamed Ateia Ibrahim (environmental engineer and group leader at the US Environmental Protection Agency and adjunct assistant professor at Rice University) and Ashley Hesterberg Butzlaff (environmental engineer at the US Environmental Protection Agency) discuss material-based guidelines for optimizing photoelectrode design with a focus on utilizing advanced nanostructure fabrication techniques to enhance charge separation and transport, as well as identifying and integrating the most effective co-catalysts to improve efficiency and stability. These insights are critical for the development of practical and efficient photo-assisted electrochemical systems, essential for future water-treatment technologies.

Successful application of photocatalytic recycled TiO2-GO membranes for the removal of trace organic compounds from tertiary effluent

Photocatalytic membranes are a promising technology for water and wastewater treatment. Towards circular economy, extending the lifetime of reverse osmosis (RO) membranes for as long as possible is extremely important, due to the great amount of RO modules discarded every year around the world. Therefore, in the present study, photocatalytic membranes made of recycled post-lifespan RO membrane (polyamide thin-film composite), TiO2 nanoparticles and graphene oxide are used in the treatment tertiary-treated domestic wastewater to remove trace organic compounds (TrOCs). The inclusion of dopamine throughout the surface modification process enhanced the stability of the membranes to be used as long as 10 months of operation. We investigated TrOCs removal by the membrane itself and in combination with UV-C and visible light by LED. The best results were obtained with integrated membrane UV-C system at pH 9, with considerable reductions of diclofenac (92%) and antipyrine (87%). Changes in effluent pH demonstrated an improvement in the attenuation of TrOCs concentration at higher pHs. By modifying membranes with nanocomposites, an increase in membrane hydrophilicity (4° contact angle reduction) was demonstrated. The effect of the lamp position on the light fluence that reaches the membrane was assessed, and greater values were found in the middle of the membrane, providing parameters for process optimization (0.29 ± 0.10 mW cm−2 at the center of the membrane and 0.07 ± 0.03 mW cm−2 at the right and left extremities). Photocatalytic recycled TiO2-GO membranes have shown great performance to remove TrOCs and extend membrane lifespan, as sustainable technology to treat wastewater.

Application of Engineered Nanomaterials as Nanocatalysts in Catalytic Ozonation: A Review.

Given the growing scarcity of water and the continuous increase in emerging pollutants detected in water bodies, there is an imperative need to develop new, more effective, and sustainable treatments for wastewater. Advanced oxidation processes (AOPs) are considered a competitive technology for water treatment. Specifically, ozonation has received notable attention as a promising approach for degrading organic pollutants in wastewater. However, different groups of pollutants are hardly degradable via single ozonation. With continuous development, it has been shown that using engineered nanomaterials as nanocatalysts in catalytic ozonation can increase efficiency by turning this process into a low-selective AOP for pollutant degradation. Nanocatalysts promote ozone decomposition and form active free radicals responsible for increasing the degradation and mineralization of pollutants. This work reviews the performances of different nanomaterials as homogeneous and heterogeneous nanocatalysts in catalytic ozonation. This review focuses on applying metal- and carbon-based engineered nanomaterials as nanocatalysts in catalytic ozonation and on identifying the main future directions for using this type of AOP toward wastewater treatment.

Removal of per- and polyfluoroalkyl substances (PFAS) from wastewater using the hydrodynamic cavitation on a chip concept

The elimination of micropollutants such as highly fluorinated substances, including per- and polyfluoroalkyl substances (PFAS), in wastewater treatment plants has been receiving growing attention due to the urgent need to minimize their adverse effects on natural water and associated ecosystems. Conventional treatment methods often fall short in effectively removing PFAS. In this study, the Hydrodynamic Cavitation on a Chip concept (HCOC) was utilized to degrade 11 common PFAS variants (PFAS11) for the first time in three different hydrodynamic cavitation reactor set-ups, each enhanced with surface modifications involving roughness elements. Stockholm municipal wastewater treated by a Membrane BioReactor (MBR) process was subjected to fully developed cavitating flow treatment using the three distinct microscale hydrodynamic cavitation (HC) reactors. The obtained results indicate that the chemical-free HCOC technique employed in this study has a significant potential in the degradation of nearly all investigated PFAS11 compounds at a notable rate of 36.1 % while the combination with MBR process can prevent blockage within the fluidic channels, enabling continuous operation with high throughput processing rates. Our proposed methodology demonstrated promising results in eliminating PFAS and could contribute to advancements in the use of microscale HC to treat micropollutants in wastewater. These findings could be a major leap in water treatment technologies addressing the global burden of resource-efficient micropollutant water treatment.

Progress in the Sustainable Development of Biobased (Nano)materials for Application in Water Treatment Technologies.

Water pollution remains a widespread problem, affecting the health and wellbeing of people around the globe. While current advancements in wastewater treatment and desalination show promise, there are still challenges that need to be overcome to make these technologies commercially viable. Nanotechnology plays a pivotal role in water purification and desalination processes today. However, the release of nanoparticles (NPs) into the environment without proper safeguards can lead to both physical and chemical toxicity. Moreover, many methods of NP synthesis are expensive and not environmentally sustainable. The utilization of biomass as a source for the production of NPs has the potential to mitigate issues pertaining to cost, sustainability, and pollution. The utilization of biobased nanomaterials (bio-NMs) sourced from biomass has garnered attention in the field of water purification due to their cost-effectiveness, biocompatibility, and biodegradability. Several research studies have been conducted to efficiently produce NPs (both inorganic and organic) from biomass for applications in wastewater treatment. Biosynthesized materials such as zinc oxide NPs, phytogenic magnetic NPs, biopolymer-coated metal NPs, cellulose nanocrystals, and silver NPs, among others, have demonstrated efficacy in enhancing the process of water purification. The utilization of environmentally friendly NPs presents a viable option for enhancing the efficiency and sustainability of water pollution eradication. The present review delves into the topic of biomass, its origins, and the methods by which it can be transformed into NPs utilizing an environmentally sustainable approach. The present study will examine the utilization of greener NPs in contemporary wastewater and desalination technologies.

Research and Application of Water Treatment Technologies for Emerging Contaminants (ECs): A Pathway to Solving Water Environment Challenges

As industrialization and urbanization accelerate, the quality of the water environment has been deteriorating, and pollution from novel pollutants (ECs), such as microplastics, pharmaceutical residues, and endocrine disruptors, has become increasingly prominent. Although the concentration of these new pollutants in the environment is very low, they pose a long-term cumulative threat to human health and ecosystem security because of their persistent and difficult-to-degrade properties. This paper reviews the treatment technologies for novel pollutants such as microplastics, pharmaceutical residues, and endocrine disruptors, including physical (e.g., sand filtration, adsorption, membrane separation), chemical (e.g., flocculation, advanced oxidation, photocatalysis), and biological (e.g., microbial degradation) methods. The various technologies’ advantages, disadvantages, and application statuses are analyzed, and future research directions and challenges are presented.