Removal of phenolic contaminants from water by pervaporation

A N, S-Containing Graphene Oxide Composite for the Adsorptive Removal of p-Nitrophenol from Aqueous Solutions

A novel 3-amino-5-mercapto-1,2,4-triazole functionalized graphene oxide composite (GO-ATT) was successfully prepared via a covalent coupling method, then employed for the removal of p-nitrophenol (PNP) from wastewater. The morphology as well as the composition of GO-ATT composite were investigated using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction spectroscopy (XRD), and X-ray photoelectron spectroscopy (XPS). The surface charge of GO-ATT composite was evaluated by Zeta potential analyses. The surface area and pore size distribution of GO-ATT composite were analyzed using specific surface analyses using the Brunauer-Emmett-Teller (BET) method. Batch adsorption experiments were performed to investigate the effects of conditional factors, including contact time, solution pH, initial PNP concentration, and contact temperature, on the adsorption process. A maximum adsorption capacity of PNP by GO-ATT composite (0.287 mmol g-1) could be obtained at 25 °C. Freundlich isotherm (R2 > 0.92505) can better describe the adsorption behavior of PNP on GO-ATT composite. The thermodynamic functions (ΔG°, ΔH°, ΔS°) indicate that adsorption is a spontaneous, endothermic, entropy-increasing process and features physisorption. The adsorption behavior of PNP on GO-ATT composite conformed to the nonlinear pseudo-second-order kinetic model. Adsorption mechanism investigation indicated that the electrostatic, π-π stacking, and hydrogen bonding interactions were involved in the adsorption process. After 10 adsorption-desorption cycles, the adsorbent exhibited a stable and efficient removal rate (94%) for PNP. Due to its advantages of a high efficiency, excellent reusability, and high stability, the covalently coupled GO-ATT composite might be used as an effective adsorbent for the removal of phenolic contaminants from wastewater.

Ultrasonic cavitation treatment of o-cresol wastewater and long-term pilot-scale study

Acoustic cavitation is a cutting-edge and eco-friendly advanced oxidation technology with significant efficacy in removing organic pollutants from water. Despite its potential, research on the degradation of o-cresol, a common and challenging phenolic pollutant, is limited. This study systematically investigates the optimal conditions for degrading o-cresol via acoustic cavitation and evaluates its application potential through extensive pilot tests. Batch test results indicate that ultrasonic cavitation effectively treats high concentrations of o-cresol (300 mg L-1), with aeration and neutral pH conditions enhancing removal efficiency, while the initial concentration has minimal impact on the removal rate. Additionally, analyses of total organic carbon (TOC), degradation products, and volatile organic compounds (VOCs) reveal that the main intermediates of o-cresol degradation through ultrasonic cavitation are substituted phenols and alkanes, with a mineralization rate reaching 60%. To assess the practical application of ultrasonic cavitation devices for o-cresol wastewater treatment, long-term pilot tests were conducted. These tests confirmed the device's effectiveness in removing o-cresol and its operational stability over 180 days. Furthermore, the study established the relationship between the o-cresol removal rate, hydraulic retention time (HRT), and operational cost. Consequently, this study demonstrates the feasibility of ultrasonic cavitation technology in treating high-concentration o-cresol wastewater and its potential for use in the pretreatment stage of biochemical treatment processes.

Treatment of high concentration phenol wastewater by low-frequency ultrasonic cavitation and long-term pilot scale study

Acoustic cavitation is an advanced, eco-friendly oxidation technology effective in removing organic pollutants from water. However, research on its use for degrading phenol, a common and challenging phenolic pollutant, is limited. This study explores the optimal conditions for phenol degradation using acoustic cavitation and assesses its practical application through extensive pilot tests. Results from batch tests show that low-frequency (15 kHz) ultrasonic cavitation effectively treats high concentrations of phenol (1000 mg L-1). Aeration and acidic pH enhance removal efficiency, while alkaline conditions inhibit degradation. Analysis of total organic carbon (TOC), degradation products, and volatile organic compounds (VOCs) reveals that the primary intermediates are substituted benzenes and alkanes. Long-term pilot tests demonstrated the device's effectiveness in phenol removal and its operational stability over 180 days. The study also establishes a relationship between removal efficiency, hydraulic retention time (HRT), and operating costs, highlighting the feasibility of low-frequency ultrasonic cavitation for treating high-concentration phenolic wastewater and its potential role in the pretreatment stage of biochemical processes.

Ultrahigh-purity ammonia recovery from synthetic coke wastewater via membrane contactor: Overcoming phenolic interference and assessing cost efficiency

Ammonia recovery from industrial wastewater using membrane contactor processes is emerging as a promising method owing to the diverse applications of ammonia. This study uniquely addressed ammonia recovery from coke plant wastewater, which is challenging due to the presence of numerous toxic and volatile phenolic compounds. Experiments were conducted using a synthetic coke plant effluent to assess the effects of various pH levels and temperatures on ammonia recovery. Specifically, the aim was to achieve high-purity ammonia recovery while minimizing the permeation of phenolic compounds. The results demonstrate that ammonia recovery in the membrane contactor processes is highly efficient, even in the presence of phenolic compounds. During temperature variations at 25 °C and 40 °C, the recovery of ammonia increased from 42.36% to 52.97% at pH 11. Additionally, increasing the pH of a feed solution from 7 to 12 significantly increased the ammonia content to 58.3%. At this pH, the recovered ammonia was of exceptional purity (>99%), with phenol, p-Cresol, and 2,4-xylenol present at negligible concentrations (0.001%, 0.002%, and 0.004%, respectively). This was attributed to the ionization of phenolic compounds at higher pH levels, which prevents their permeation through the hydrophobic membrane. The estimated cost analysis revealed that the membrane contactor process at pH 12 was approximately 1.41 times more cost-effective than conventional air-stripping processes over eight years of operating period (pH-12 membrane contactor: $19.79; pH-12 air stripping: $23.75). This study provides a detailed analysis of the optimal conditions for selective ammonia recovery from complex wastewater, highlighting both effective treatment and sustainable resource recovery and offering a superior alternative to traditional methods.

MnO/TiO2/C/N-CNTs derived from Mn-doped Ti MOFs for simultaneous detection of catechol and hydroquinone

Mn-doped Ti-based MOFs (MnTi MOFs) were synthesized by a solvothermal method, and calcined at high temperature after being mixed with pre-prepared PPy nanotubes to give MnO/TiO2/C/N-CNTs composites. The composites were studied by SEM, XRD, XPS and FTIR. Based on these composites, a new electrochemical sensor was prepared, which has good electrocatalytic ability for the redox of catechol (CC) and hydroquinone (HQ), and can detect CC and HQ simultaneously. The results showed that the oxidation peak current of CC and HQ increased linearly in the concentration range of 0.50-120.00 μM. The detection limits were 0.033 μM and 0.019 μM, respectively. The constructed sensor has been successfully used for the simultaneous detection of CC and HQ in lake water and tap water, and has a good recovery rate.

Advances in MXene-based technologies for the remediation of toxic phenols: A comprehensive review

The pressing global issue of organic pollutants, particularly phenolic compounds derived primarily from industrial wastes, poses a significant threat to the environment. Although progress has been made in the development of low-cost materials for phenolic compound removal, their effectiveness remains limited. Thus, there is an urgent need for novel technologies to comprehensively address this issue. In this context, MXenes, known for their exceptional physicochemical properties, have emerged as highly promising candidates for the remediation of phenolic pollutants. This review aims to provide a comprehensive and critical evaluation of MXene-based technologies for the removal of phenolic pollutants, focusing on the following key aspects: (1) The classification and categorization of phenolic pollutants, highlighting their adverse environmental impacts, and emphasizing the crucial need for their removal. (2) An in-depth discussion on the synthesis methods and properties of MXene-based composites, emphasizing their suitability for environmental remediation. (3) A detailed analysis of MXene-based adsorption, catalysis, photocatalysis, and hybrid processes, showcasing current advancements in MXene modification and functionalization to enhance removal efficiency. (4) A thorough examination of the removal mechanisms and stability of MXene-based technologies, elucidating their operating conditions and stability in pollutant removal scenarios. (5) Finally, this review concludes by outlining future challenges and opportunities for MXene-based technologies in water treatment, facilitating their potential applications. This comprehensive review provides valuable insights and innovative ideas for the development of versatile MXene-based technologies tailored to combat water pollution effectively.

Design of PDMS/PAN composite membranes with ultra-interfacial stability via layer integration

The interfacial interaction between the selective layer and porous substrate directly determines the separation performance and service lifetime of functional composite membranes. Till now, almost all reported polymeric selective layers are physically in contact with the substrate, which is unsatisfactory for long-term operation. Herein, we introduced a functional composite membrane with ultra-interfacial stability via layer integration between the polydimethylsiloxane selective layer and polyacrylonitrile substrate, where a facile light-triggered copolymerization achieved their covalent bonding. The critical load for the failure of the selective layer is 45.73 mN when testing the interfacial adhesion, i.e., 5.8 times higher than that before modification and significantly higher than previous reports. It also achieves superior pervaporation performance with a separation factor of 9.54 and membrane flux of 1245.6 g m-2 h-1 feeding a 1000 ppm phenol/water solution at 60 °C that is significantly higher than the same type of polymeric ones. Not limited to pervaporation, such a strategy sheds light on the design of highly stable composite membranes with different purposes, while the facile photo-trigged technique shows enormous scalability.

Advances in molecularly imprinted materials for selective adsorption of phenolic pollutants from the water environment: Synthesis, applications, and improvement

The application of molecularly imprinted material (MIM) is widely employed as a material for removing phenolic pollutants from the water environment, owing to its exceptional capacity for selective adsorption and high sensitivity. In this paper, the preparation principle, bonding types, and preparation methods of MIM have been comprehensively introduced. Meanwhile, according to the binding type of MIM with phenolic pollutants, three categories of hydroxyl bonding, hydroxyl carboxyl bonding, and hydroxyl nitro bonding were carried out to explain its application to phenolic pollutants. Strategies for addressing the challenges of selective instability, high regeneration costs, and template leakage in MIM applications were summarized. These strategies encompassed the introduction of superior carriers, enhancements in preparation processes, and the utilization of molecular dynamics simulation-assisted technology. Finally, the prospects in the three aspects of material preparation, process coupling, and recycling. In summary, this paper has demonstrated the potential of utilizing MIM for the selective treatment of phenolic pollutants from the water environment.

Advancement of membrane separation technology for organic pollutant removal

In the face of growing global freshwater scarcity, the imperative to recycle and reuse water becomes increasingly apparent across industrial, agricultural, and domestic sectors. Eliminating a range of organic pollutants in wastewater, from pesticides to industrial byproducts, presents a formidable challenge. Among the potential solutions, membrane technologies emerge as promising contenders for treating diverse organic contaminants from industrial, agricultural, and household origins. This paper explores cutting-edge membrane-based approaches, including reverse osmosis, nanofiltration, ultrafiltration, microfiltration, gas separation membranes, and pervaporation. Each technology's efficacy in removing distinct organic pollutants while producing purified water is scrutinized. This review delves into membrane fouling, discussing its influencing factors and preventative strategies. It sheds light on the merits, limitations, and prospects of these various membrane techniques, contributing to the advancement of wastewater treatment. It advocates for future research in membrane technology with a focus on fouling control and the development of energy-efficient devices. Interdisciplinary collaboration among researchers, engineers, policymakers, and industry players is vital for shaping water purification innovation. Ongoing research and collaboration position us to fulfill the promise of accessible, clean water for all.

Phenolic compounds in water: Review of occurrence, risk, and retention by membrane technology

Phenolic compounds are one of the main contributors to water source contamination worldwide. In this review, the data collected on Elsevier, Scopus, and Pubmed, considering papers published between 2000 and 2023, showed more than 60 different phenols have been identified in water matrix (<0.065-179,000,000 ng L-1). The highest concentration reported was in surface water canals in India. The most recurrent and studied compound was bisphenol A (n = 93) in concentrations ranging from 0.45 to 2,970,000 ng L-1. The solid phase extraction (HBL Oasis cartridge) and methanol as solvent was the method of pre-concentration most used followed by gas chromatography for the determination of phenols in water samples. The importance of drinking water guidelines incorporating more phenolic compounds was emphasized given the variety of these compounds quantified in water matrix. The human health risk assessment (HRA) was performed for the min-max concentrations of the pollutants reported in the literature. High HRA even at the lowest concentrations for 2-nitrophenol, 2,6-dichlorophenol, 3,4,5-trichlorophenol, 2,3,4,6-tetrachlorophenol, and 2,4-dinitrophenol was recognized. The cancer risk estimated was considered possible for 3-methylphenol, 2,4-dimethylphenol, 2,4,6-trichlorophenol, pentachlorophenol, and 2,4-dinitrophenol in the highest concentrations. The in-depth discussion of mechanisms, advantages, challenges, and carbon footprint of membrane technologies in water treatment and phenols retention demonstrated the great potential and trends for the production of safe drinking water, highlighting reverse osmosis, as a mature technology, and membrane distillation, as an emergent technology.

Recent advances in remediation strategies for mitigating the impacts of emerging pollutants in water and ensuring environmental sustainability

The proliferation of emerging pollutants (EPs), encompassing a range of substances such as phthalates, phenolics, pharmaceuticals, pesticides, personal care products, surfactants, and disinfection agents, has become a significant global concern due to their potential risks to the environment and human well-being. Over the past two decades, numerous research studies have investigated the presence of EPs in wastewater and aquatic ecosystems, with the United States Environmental Protection Agency (USEPA) categorizing these newly introduced chemical compounds as emerging contaminants due to their poorly understood impact. EPs have been linked to adverse health effects in humans, including genotoxic and cytotoxic effects, as well as conditions such as obesity, diabetes, cardiovascular disease, and reproductive abnormalities, often associated with their estrogenic action. Microalgae have shown promise in the detoxification of both inorganic and organic contaminants, and several large-scale microalgal systems for wastewater treatment have been developed. However, the progress of algal bioremediation can be influenced by accidental contaminations and operational challenges encountered in pilot-scale research. Microalgae employ various processes, such as bioadsorption, biouptake, and biodegradation, to effectively remediate EPs. During microalgal biodegradation, complex chemical compounds are transformed into simpler substances through catalytic metabolic degradation. Integrating algal bioremediation with existing treatment methodologies offers a viable approach for efficiently eliminating EPs from wastewater. This review focuses on the use of algal-based biological remediation processes for wastewater treatment, the environmental impacts of EPs, and the challenges associated with implementing algal bioremediation systems to effectively remove emerging pollutants.

Catechol-Based Porous Organic Polymers for Effective Removal of Phenolic Pollutants from Water

Phenolic pollutants released from industrial activities seriously damage natural freshwater resources, and their elimination or reduction to safe levels is an urgent challenge. In this study, three catechol-based porous organic polymers, CCPOP, NTPOP, and MCPOP, were prepared using sustainable lignin biomass-derived monomers for the adsorption of phenolic contaminants in water. CCPOP, NTPOP, and MCPOP showed good adsorption performance for 2,4,6-trichlorophenol (TCP) with theoretical maximum adsorption capacities of 808.06 mg/g, 1195.30 mg/g, and 1076.85 mg/g, respectively. In addition, MCPOP maintained a stable adsorption performance after eight consecutive cycles. These results indicate that MCPOP is a potential material for the effective treatment of phenol pollutants in wastewater.

Nanoparticle-Embedded Polymers and Their Applications: A Review

There has been increasing interest in the study and development of nanoparticle-embedded polymeric materials and their applications to special membranes. Nanoparticle-embedded polymeric materials have been observed to have a desirable compatibility with commonly used membrane matrices, a wide range of functionalities, and tunable physicochemical properties. The development of nanoparticle-embedded polymeric materials has shown great potential to overcome the longstanding challenges faced by the membrane separation industry. One major challenge that has been a bottleneck to the progress and use of membranes is the balance between the selectivity and the permeability of the membranes. Recent developments in the fabrication of nanoparticle-embedded polymeric materials have focused on how to further tune the properties of the nanoparticles and membranes to improve the performance of the membranes even further. Techniques for improving the performance of nanoparticle-embedded membranes by exploiting their surface characteristics and internal pore and channel structures to a significant degree have been incorporated into the fabrication processes. Several fabrication techniques are discussed in this paper and used to produce both mixed-matrix membranes and homogenous nanoparticle-embedded polymeric materials. The discussed fabrication techniques include interfacial polymerization, self-assembly, surface coating, and phase inversion. With the current interest shown in the field of nanoparticle-embedded polymeric materials, it is expected that better-performing membranes will be developed soon.

Fabrication of PEBA/HZIF-8 Pervaporation Membranes for High Efficiency Phenol Recovery

Phenol and its chemical derivatives serve as essential chemical materials are indispensable for the synthesis of many kinds of polymers. However, they are highly toxic, carcinogenic, difficult to be degraded biologically, and often found in aqueous effluents. Recovery of hazardous phenol from wastewater remains a daunting challenge. Herein, we prepared a hybrid membrane containing polyether block amide (PEBA) matrix and HZIF-8 fillers. To improve the compatibility between ZIF-8 and PEBA, ZIF-8 was modified by using polystyrene (PS) as a template to prepare porous HZIF-8. ZIF-8, composed of zinc nodes linked by the imidazole ring skeleton, is a kind of inorganic material with high hydrothermal stability, ordered pores, and hydrophobic microporous surfaces, which has a wide range of applications in membrane separation. The separation performance of the PEBA/HZIF-8 based membranes for phenol/water is improved due to the presence of PS on the surface of HZIF-8 and the imidazole ring skeleton in ZIF-8, which enhance the π-π interaction between HZIF-8 and phenol molecules. The effects of HZIF-8 content, feed phenol concentration, and feed temperature on the pervaporation performance of PEBA/HZIF-8 membranes were further investigated. The results showed that the pervaporation performance of the PEBA/HZIF-8-10 membrane was promising with a separation factor of 80.89 and permeate flux of 247.70 g/m²·h under the feed phenol concentration of 0.2 wt % at 80 °C. In addition, the PEBA/HZIF-8-10 membrane presented excellent stability, which has great prospect for practical application in phenol recovery from waste water.

PDMS with Tunable Side Group Mobility and Its Highly Permeable Membrane for Removal of Aromatic Compounds

Polydimethylsiloxane (PDMS), as the benchmark of organophilic membrane materials, still faces challenges for removal of aromatic compounds due to the undesirable transport channels. In this work, we propose to reconstruct the PDMS conformation with tunable side group mobility by introducing phenyl as rigid molecular spacer to relieve steric hindrance of large-sized aromatic molecules; meanwhile, polymer segments are loosely stacked to provide additional degrees of freedom as increasing the permeant size. Moreover, the reconstructed PDMS is engineered into the composite membrane with prevention of condensation of aromatic compounds in the substrate pores. The resulting thin-film composite membrane achieved one order of magnitude higher flux (11.8 kg m^-2  h^-1 ) with an equivalent separation factor (12.3) compared with the state-of-the-art membranes for aromatic removal. The permeant-customized membrane molecular and microstructure designing strategy opens a new avenue to develop membranes for specific separation targets.

MXene-based designer nanomaterials and their exploitation to mitigate hazardous pollutants from environmental matrices

MXenes are a rapidly expanding and large family of two-dimensional (2D) materials that have recently garnered incredible research interests for diverse applications domains in various industrial sectors. Owing to unique inherent structural and physicochemical characteristics, such as high surface area, biological compatibility, robust electrochemistry, and high hydrophilicity, MXenes are appraised as a prospective avenue for environmental-clean-up technologies to detect and mitigate an array of recalcitrant hazardous contaminants from environmental matrices. MXene-based nanoarchitectures are thought to mitigate inorganic pollutants via interfacial chemical transformation and sorption, while three different mechanisms, including i) surface complexation and sorption (ii) catalytic activation and removal and (iii) radical's generation-based photocatalytic degradation, are involved in the removal of organic contaminants. Considering the application performance of MXenes on the incessant rise to expansion, in this review, we discuss the wide-spectrum applicability of diverse MXenes-based hybrid nanocomposites in environmental remediation. A brief description related to environmental pollutants, structural properties, chemical abilities, and synthesis route of MXenes is delineated at the start. Afterwards, the adsorption and degradative robustness of MXene-based designer nanomaterials for various contaminants including organic dyes, toxic heavy metals, pesticide residues, phenolics, antibiotics, radionuclides, and many others are thoroughly vetted to prove their potentiality in the arena of wastewater purification and remediation. Lastly, challenges and trends in assessing the wide-range applicability and scalability of MXenes are outlined. Seeing encouraging outcomes in plenty of reports, it can be concluded that MXenes-based nanostructures could be considered the next-generation candidates for water sustainability.

The Influence of Photocatalytic Reactors Design and Operating Parameters on the Wastewater Organic Pollutants Removal—A Mini-Review

The organic pollutants removal by conventional methods (adsorption, coagulation, filtration, microorganism and enzymes) showed important limitation due to the reluctance of these molecules. An alternative to this issue is represented by the photocatalytic technology considered as an advanced oxidation process (AOP). The photoreactors design and concepts vary based on the working regime (static or dynamic), photocatalyst morphology (powders or bulk) and volume. This mini-review aims to provide specific guidelines on the correlations between the photoreactor concept characteristics (working regime, volume and flow rate), irradiation scenarios (light spectra, irradiation period and intensity) and the photocatalytic process parameters (photocatalyst materials and dosage, pollutant type and concentration, pollutant removal efficiency and constant rate). The paper considers two main photoreactor geometries (cylindrical and rectangular) and analyses the influence of parameters optimization on the overall photocatalytic efficiency. Based on the systematic evaluation of the input data reported in the scientific papers, several perspectives regarding the photocatalytic reactors’ optimization were included.