Chemical treatment technologies for waste-water recycling—an overview

Biocompatible PANI-Encapsulated Chemically Modified Nano-TiO2 Particles for Visible-Light Photocatalytic Applications

Polyaniline (PANI) constitutes a very propitious conductive polymer utilized in several biomedical, as well as environmental applications, including tissue engineering, catalysis, and photocatalysis, due to its unique properties. In this study, nano-PANI/N-TiO2 and nano-PANI/Ag-TiO2 photocatalytic composites were fabricated via aniline's oxidative polymerization, while the Ag-and N-chemically modified TiO2 nanopowders were synthesized through the sol-gel approach. All produced materials were fully characterized. Through micro-Raman and FT-IR analysis, the co-existence of PANI and chemically modified TiO2 particles was confirmed, while via XRD analysis the composites' average crystallite size was determined as ≈20 nm. The semi-crystal structure of polyaniline exhibits higher photocatalytic efficiency compared to that of other less crystalline forms. The spherical-shaped developed materials are innovative, stable (zeta potential in the range from -26 to -37 mV), and cost-effective, characterized by enhanced photocatalytic efficiency under visible light (energy band gaps ≈ 2 eV), and synthesized with relatively simple methods, with the possibility of recycling and reusing them in potential future applications in industry, in wastewater treatment as well as in biomedicine. Thus, the PANI-encapsulated Ag and N chemically modified TiO2 nanocomposites exhibit high degradation efficiency towards Rhodamine B dye upon visible-light irradiation, presenting simultaneously high biocompatibility in different normal cell lines.

Physico-chemical treatments for the removal of cyanotoxins from drinking water: Current challenges and future trends

Cyanobacteria are highly prevalent blue-green algae that grow in stagnant and nutrient-rich water bodies. Environmental conditions, such as eutrophication and human activities, increased the cyanobacterial blooms in freshwater resources worldwide. The excessive bloom formation has also resulted in an alarming surge of cyanobacterial toxins. Prolonged exposure to cyanotoxins is a potential threat to natural ecosystems, animal and human health by the spoilage of the quality of bathing and drinking water. Various molecular and analytical methods have been proposed to monitor their occurrence and understand their global distribution. Moreover, different physical, chemical, and biological approaches have been employed to control cyanobacterial blooms and their toxins to mitigate their occurrence. Numerous strategies have been engaged in drinking water treatment plants (DWTPs). However, the degree of treatment varies greatly and is primarily determined by the source, water properties, and operating parameters such as temperature, pH, and cyanotoxin variants and levels. A comprehensive compilation of methods, from traditional approaches to more advanced oxidation processes (AOPs), are presented for the removal of intracellular and extracellular cyanotoxins. This review discusses the effectiveness of various physicochemical operations and their limitations in a DWTP, for the removal of various cyanotoxins. These operations span from simple to advanced treatment levels with varying degrees of effectiveness and differing costs of implementation. Furthermore, mitigation measures applied in other toxin systems have been considered as alternative strategies.

Design and application of metal organic frameworks for heavy metals adsorption in water: a review

The growing apprehension surrounding heavy metal pollution in both environmental and industrial contexts has spurred extensive research into adsorption materials aimed at efficient remediation. Among these materials, Metal-Organic Frameworks (MOFs) have risen as versatile and promising contenders due to their adjustable properties, expansive surface areas, and sustainable characteristics, compared to traditional options like activated carbon and zeolites. This exhaustive review delves into the synthesis techniques, structural diversity, and adsorption capabilities of MOFs for the effective removal of heavy metals. The article explores the evolution of MOF design and fabrication methods, highlighting pivotal parameters influencing their adsorption performance, such as pore size, surface area, and the presence of functional groups. In this perspective review, a thorough analysis of various MOFs is presented, emphasizing the crucial role of ligands and metal nodes in adapting MOF properties for heavy metal removal. Moreover, the review delves into recent advancements in MOF-based composites and hybrid materials, shedding light on their heightened adsorption capacities, recyclability, and potential for regeneration. Challenges for optimization, regeneration efficiency and minimizing costs for large-scale applications are discussed.

Efficient performance of InP and InP/ZnS quantum dots for photocatalytic degradation of toxic aquatic pollutants

In recent years, the growing concern over the presence of toxic aquatic pollutants has prompted intensive research into effective and environmentally friendly remediation methods. Photocatalysis using semiconductor quantum dots (QDs) has developed as a promising technology for pollutant degradation. Among various QD materials, indium phosphide (InP) and its hybrid with zinc sulfide (ZnS) have gained considerable attention due to their unique optical and photocatalytic properties. Herein, InP and InP/ZnS QDs were employed for the removal of dyes (crystal violet, and congo red), polyaromatic hydrocarbons (pyrene, naphthalene, and phenanthrene), and pesticides (deltamethrin) in the presence of visible light. The degradation efficiencies of crystal violet (CV) and congo red (CR) were 74.54% and 88.12% with InP, and 84.53% and 91.78% with InP/ZnS, respectively, within 50 min of reaction. The InP/ZnS showed efficient performance for the removal of polyaromatic hydrocarbons (PAHs). For example, the removal percentage for naphthalene, phenanthrene, and pyrene was 99.8%, 99.6%, and 88.97% after the photocatalytic reaction. However, the removal percentage of InP/ZnS for pesticide deltamethrin was 90.2% after 90 min light irradiation. Additionally, advanced characterization techniques including UV-visible spectrophotometer (UV-Vis), photoluminescence (PL), X-ray diffractometer (XRD), energy-dispersive spectrometer (EDS) elemental mapping, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) were used to analyze the crystal structure, morphology, and purity of the fabricated materials in detail. The particle size results obtained from TEM are in the range of 2.28-4.60 nm. Both materials (InP and InP/ZnS) exhibited a spherical morphology, displaying distinct lattice fringes. XRD results of InP depicted lattice planes (111), (220), and (311) in good agreement with cubic geometry. Furthermore, the addition of dopants was discovered to enhance the thermal stability of the fabricated material. In addition, QDs exhibited efficacy in the breakdown of PAHs. The analysis of their fragmentation suggests that the primary mechanism for PAHs degradation is the phthalic acid pathway.

Envisioning the innovative approaches to achieve circular economy in the water and wastewater sector

Given the challenges of urbanization and rapid resource depletion, policymakers have been compelled to abandon the old sequential paradigm of "take-make-use-dispose" to a circular approach that prioritizes preservation of natural resources. The circular economy represents a sustainable management concept that focuses on reducing, recovering, reusing, and recycling waste. While significant strides have been made in implementing circular economy principles in various industries such as automotive, electronics, and construction, particular attention has been given to the water and wastewater domains due to imbalances in water resources. Here we review the global progress of circular economy adoptability in the water and wastewater domains, considering technical, environmental, economic, and social perspectives. It assesses the current state of circular economy integration in the wastewater domain worldwide and presents approaches to promote and accelerate its adoption. The study critically examines the principles of waste management, known as the 6Rs (reclaim, restore, recycle, reduce, recover, reuse), in order to formulate effective strategies for integrating circular economy practices in the water and wastewater domains. Additionally, the study provides an overview of existing research conducted on different aspects of circular economy. Finally, the study analyzes the challenges and opportunities associated with implementing circular economy principles in the water sector.

Novel, Biosynthesis of Palladium Nanoparticles using Strychnos Potatorum Polysaccharide as a Green sustainable approach; and their effective Catalytic Hydrogenation of 4-Nitrophenol

In the current study, we successfully used strychnos potatorum polysaccharide through autoclaving to synthesize palladium nanoparticles in a green, sustainable process. These polysaccharide act as a stabilizing, capping, and reducing agent. It also used various analytical characterizations, including UV-Visible spectroscopy, FT-IR spectroscopy, X-Ray diffraction (XRD), Scanning electron microscopy (FE-SEM), EDAX, and X-ray photoelectron spectroscopy (XPS), TEM and gel permeation chromatography (GPC) are used to analyze biosynthesized pallidum nanoparticles (PdNPs). The surface plasmon resonance (SPR) band at 276 nm and UV-visible spectroscopy revealed the presence of the generated PdNPs. The XRD data show that PdNPs have crystalline behavior and a pristine face-centered cubic (FCC) structure. The PdNPs were successfully developed by catalytic reduction of 4-nitrophenol (4-NP). The catalytic activity and reusability of the environmentally friendly PdNPs catalyst were demonstrated by achieving a remarkable transformation of 95 % nitrophenol to 4-aminophenol after five cycles. The reaction rate constant (k) for the degradation of 4-nitrophenol (4-NP) using SP-PdNPs as a catalyst is 0.1201 min-1 and R2 0.9867, with a normalized rate constant of (Knor = K/m) of 7.206 s-1 mM-1. These findings provide fundamental knowledge of the catalytic process governing the hydrogenation of p-nitrophenol, which will help designers of effective catalysts. An innovative and affordable technique for creating PdNPs that are environmentally acceptable and can be utilized as effective catalysts in environmental applications is the use of strychnos potatorum gum polysaccharide. The green-synthesized PdNPs can be used for pollutant remediation, including pharmaceutical, domestic, heavy metal, industrial, and pesticide pollutants.

Application of 2D MoS2 Nanoflower for the Removal of Emerging Pollutants from Water

Two-dimensional (2D) nanomaterial-MoS2 (molybdenum disulfide) has gained interest among researchers, owing to its exceptional mechanical, biological, and physiochemical properties. This paper reports on the removal of organic dyes and an emerging contaminant, Ciprofloxacin, by a 2D MoS2 nanoflower as an adsorbent. The material was prepared by a green hydrothermal technique, and its high Brunauer-Emmett-Teller-specific area of 185.541m2/g contributed to the removal of 96% rhodamine-B dye and 85% Ciprofloxacin. Various characterizations, such as X-ray diffraction, scanning electron microscopy linked with energy-dispersive spectroscopy, and transmission electron microscopy, revealed the nanoflower structure with good crystallinity. The feasibility and efficacy of 2D MoS2 nanoflower as a promising adsorbent candidate for the removal of emerging pollutants was confirmed in-depth in batch investigations, such as the effects of adsorption time, MoS2 dosages, solution pH, and temperature. The adsorption mechanism was further investigated based on thermodynamic calculations, adsorption kinetics, and isotherm modeling. The results confirmed the exothermic nature of the enthalpy-driven adsorption as well as the fast kinetics and physisorption-controlled adsorption process. The recyclability potential of 2D MoS2 exceeds four regeneration recycles. MoS2 nanoflower has been shown to be an effective organic pollutant removal adsorbent in water treatment.

Membrane-catalysis integrated system for contaminants degradation and membrane fouling mitigation: A review

The integration of catalytic degradation and membrane separation processes not only enables continuous degradation of contaminants but also effectively alleviates inevitable membrane fouling, demonstrating fascinating practical value for efficient water purification. Such membrane-catalysis integrated system (MCIS) has attracted tremendous research interest from scientists in chemical engineering and environmental science recently. In this review, the advantages of MCIS are discussed, including the membrane structure regulation, stable catalyst loading, nano-confinement effect, and efficient natural organic matter (NOM) exclusion, highlighting the synergistic effect between membrane separation and catalytic process. Subsequently, the design considerations for the fabrication of catalytic membranes, including substrate membrane, catalytic material, and fabrication method, are comprehensively summarized. Afterward, the mechanisms and performance of MCIS based on different catalytic types, including liquid-phase oxidants/reductants involved MCIS, gas involved MCIS, photocatalysis involved MCIS, and electrocatalysis involved MCIS are reviewed in detail. Finally, the research direction and future perspectives of catalytic membranes for water purification are proposed. The current review provides an in-depth understanding of the design of catalytic membranes and facilitates their further development for practical applications in efficient water purification.

In Situ Interfacial Polymerized Arginine-Doped Polydopamine Thin-Film Nanocomposite Membranes for High-Separation and Antifouling Reverse Osmosis

In this work, we synthesized polydopamine nanoparticles (PDNPs-M, M = I, II, III, and IV) with uniform particle sizes but varying l-arginine (Arg) contents (0%, 0.53%, 3.73%, and 6.62%) through a one-pot synthesis approach. Thin-film nanocomposite (TFN) membranes were fabricated via in situ interfacial polymerization (IP). The effects of the PDNPs-M chemical structure on the IP process and the consequent impacts on the structure and properties of the polyamide (PA) selective layer were investigated. The hydrophilicity and dispersibility of PDNPs-M exhibited an upward trend with the Arg content. Furthermore, Arg doping contributes to a denser and smoother PA layer. Among the TFC and TFN membranes, TFN-PDNPs-IV exhibited a water permeability of 3.89 L·m-2·h-1·bar-1 (55.1% higher than that of TFC-0) with a NaCl rejection rate of 98.8%, signifying superior water/salt selectivity. Additionally, TFN-PDNPs-IV exhibited regular pressure stability, commendable acid/alkali stability, and enhanced antifouling properties. These findings highlight the significant impact of nanoparticle hydrophilic functional groups on the structural and functional attributes of TFN membranes, offering a promising approach for developing advanced reverse osmosis membranes.

Enhanced degradation of Congo-red dye by Cr3+ doped α-Fe2O3 nano-particles under sunlight and industrial wastewater treatment

Considering the increasing amount of water pollution, nanocomposite advances for the effective elimination of hazardous pollutants are still needed. α-Fe2O3, Cr0·5Fe1·5O3 and CrFeO3 nanoparticles were synthesized via an eco-friendly material synthesis i. e hydrothermal route without using any precipitating agent and were studied to remove congo-red dye using photocatalytic properties. X-ray diffraction (XRD), Transmission electron microscopy (TEM), Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FESEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS) characterizations have been performed to know about the material structure and properties of synthesized samples. High efficiency (95.2%) of degradation was achieved under sunlight using a very low amount of CrFeO3 catalyst (0.2 g/L) at a 6-pH level of dye and was confirmed using UV spectroscopy, TOC (84%), LC-HRMS. Also, the potential to degrade the CR dye was concluded from the high rate of BOD5/COD. The results showed a significant enhancement in the degradation of α-Fe2O3 from 52.3% to 95.2% in a short duration of 15 min by introducing chromium as a dopant. The doping of chromium influenced the major factors responsible for the photocatalytic activity such as the increase in range of absorbance, increased e--h+ pair separation, improvement in the charge transfer process and active site formation which significantly enhanced the process of degradation. We found that the Cr-doped α-Fe2O3 nanomaterial could effectively remove dyes, such as congo-red, from industrial water-waste.

Cationic Surfactant-Modified Tetraselmis sp. for the Removal of Organic Dyes from Aqueous Solution

The modification of the Tetraselmis sp. algae material (Tetra-Alg) with surfactant Cethyltrimethylammonium Bromide (CTAB) yielded adsorbent Tetra-Alg-CTAB as an adsorbent of methyl orange (MO) and methylene blue (MB) solutions. The characterization of the adsorbent used an infrared (IR) spectrometer to identify functional groups and Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDX FEI Inspect-S50, Midland, ON, Canada) to determine the surface morphology and elemental composition. Methyl orange and methylene blue adsorption on the adsorbent Tetra-Alg, Tetraselmis sp. algae-modified Na+ ions (Tetra-Alg-Na), and Tetra-Alg-CTAB were studied, including variations in pH, contact time, concentration, and reuse of adsorbents. The adsorption of MO and MB by Tetra-Alg-CTAB at pH 10, during a contact time of 90 min, and at a concentration of 250 mg L-1 resulted in MO and MB being absorbed in the amounts of 128.369 and 51.013 mg g-1, respectively. The adsorption kinetics and adsorption isotherms of MO and MB and Tetra-Alg, Tetra-Alg-Na, and Tetra-Alg-CTAB tend to follow pseudo-second-order kinetics models and Freundlich adsorption isotherms with each correlation coefficient value (R2) approaching 1. Due to the modification with the cationic surfactant CTAB, anionic dyes can be strongly sorbed in alkaline pH due to strong electrostatic attraction, while MB is more likely to involve cation exchange and hydrogen bonding. The reuse of Tetra-Alg-CTAB was carried out four times with adsorption percent > 70%, and the adsorbent was very effective in the adsorption of anionic dyes such as MO.

A Sustainable Method for Removal of the Full Range of Liquid and Solid Hydrocarbons from Water Including Up- and Recycling

Beyond their CO2 emittance when burned as fuels, hydrocarbons (HCs) serve as omnipresent raw materials and commodities. No matter if as liquid oil spills or the endless amounts of plastic roaming the oceans, HCs behave as persistent pollutants with water as main carrier to distribute. Even if their general chemical structure [-(CH2 )n -] is quite simple, the endless range of n leads to contaminations of different appearances and properties. A water remediation method based on superparamagnetic iron oxide nanoparticles (SPIONs) modified with self-assembled monolayers of alkyl phosphonic acid derivatives is presented. These molecules enable the SPIONs to non-covalently bind HCs, independently from the molecular weight, size and morphology. The attractive interaction is mainly based on hydrophobic and Coulomb interaction, which allows recycling of the SPIONs. The superparamagnetic core allows a simple magnetic collection and separation from the water phase which makes it a promising addition to wastewater treatment. Agglomerates of collected plastic "waste" even exhibit superior adsorption properties for crude oil, another hydrocarbon waste which gives these collected wastes a second life. This upcycling approach combined with presented recycling methods enables a complete recycling loop.

Demonstrating removal credits for contaminants of emerging concern in recycled water through a reverse osmosis barrier-A predictive framework

The performance of individual reverse osmosis (RO) systems varies significantly with different contaminants of emerging concern (CECs). As such, log reduction values (LRVs) of the concentration of these chemicals cannot be arbitrarily credited in water treatment and water recycling. This study looks to present an approach to the management of chemical risks by providing a systematic validation of RO barrier performance with respect to LRV credits for various classes of CECs. In this work, a one-off sampling campaign across five treatment barriers (strainer filtration, ultrafiltration, RO, ion exchange, chlorination) of a full-scale water recycling plant was conducted, followed by a systematic sampling campaign for a period of six weeks across just the RO barrier. The CECs screening methodology used GC-MS for quantification of 948 trace organic chemicals along with specific 44 per- and polyfluoroalkyl substances (PFAS) screening using LC-MS/MS to demonstrate the removal credits of the RO barrier to a wide spectrum of CECs. The work was used to validate an LRV barrier credit framework so as to predict the performance of a polyamide RO membrane for removal of a range of chemical classes, under typical operational conditions. Conductivity was validated as an efficient surrogate for membrane integrity and RO performance, along with specified operational conditions associated with permeate flux and recovery rate. A bioassay method (photobacterium test) showed good potential to be used as a quick measure to indicate the general toxicity of a sample caused by chemical contamination, because of its high detection sensitivity and time and cost efficiency.

Modified approaches to prepare nano-magnesium silicates with hierarchical pore structure and their performance towards adsorption of Cd2

A series of flower-like magnesium silicate samples with hierarchical pore were prepared by the solvothermal method under template-free conditions using sodium dodecyl sulfate as the modifier and ethanol-water as the solvent. These samples were characterized by various methods and were evaluated for the adsorption of heavy metal Cd2+. The results showed that the adding modifier did not change the crystal structure of the magnesium silicate samples. In the range of 2~80 nm, they still showed hierarchical pore distribution mainly composed of mesopores and macropores, which facilitates the rapid transport of adsorbent within the pore channel. Therefore, the adsorption of Cd2+ was greatly accelerated. Meanwhile, the larger specific surface area (as high as 553 m2/g) of these samples significantly increased the theoretical maximum adsorption amount of Cd2+ up to 295.3 mg/g due to more available adsorption sites. The adsorption dynamic behavior of the samples on Cd2+ was in accordance with the pseudo-second-order adsorption model, and their thermodynamic behavior follows the Langmuir adsorption model. The adsorption mechanism of the sample was proposed as electrostatic adsorption and exchange of metal ions and acidic groups on its surface with ions in solution. The obtained magnesium silicate materials are expected to remove heavy metals from wastewater.

Porous Hierarchical Ni/Mg/Al Layered Double Hydroxide for Adsorption of Methyl Orange from Aqueous Solution

A basic urea technique was successfully used to synthesize Mg/Al-Layered double hydroxides (Mg/Al LDHs), which were then calcined at 400 °C to form Mg/Al-Layered double oxides (Mg/Al LDOs). To reconstruct LDHs, Mg/Al LDOs were fabricated with different feeding ratios of Ni by the co-precipitation method. After synthesis, the Ni/Mg/Al-layered double hydroxides (NMA-LDHs) with 20% and 30% Ni (S1 and S2) were roasted at 400 °C and transformed into corresponding Ni/Mg/Al-layered double oxides (NMA-LDOs) (S1a and S2b, respectively). The physiochemical properties of synthesized samples were also evaluated by various characterization techniques, such as X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR), and Brunauer, Emmett, and Teller (BET). The adsorption behavior of methyl orange (MO) onto the synthesized samples was evaluated in batch adsorption mode under varying conditions of contact time, adsorbent quantity, and solution pH. As the dosage amount increased from 0.01-0.04 g, the removal percentage of MO dye also increased from 83% to 90% for S1, 84% to 92% for S1a, 77% to 87% for S2, and 93% to 98% for S2b, respectively. For all of the samples, the adsorption kinetics were well described by the pseudo-second-order kinetic model. The equilibrium adsorption data were well fitted to both Langmuir and Freundlich models for methyl orange (MO). Finally, three adsorption-desorption cycles show that NMA-LDHs and NMA-LDOs have greater adsorption and reusability performance for MO dye, signifying that the design and fabrication strategy can facilitate the application of the natural hydrotalcite material in water remediation.

Efficient Mn(II) removal by biological granular activated carbon filtration

Sufficient and sustainable manganese(II) removal is a challenging task to prevent Mn-related drinking water discoloration problems. This study investigated Mn(II) removal by granular activated carbon (GAC) filtration under various conditions. The results showed that biological GAC filter columns could reduce Mn(II) from 400 μg/L to 10 μg/L after a short ripening period, while sand filter columns did not show evident Mn(II) removal function. Water quality changes, pretreatment with NaClO and chemogenic MnO_x coating on GAC media surface did not influence the Mn(II) removal capacity of GAC filter columns. 16S rRNA gene sequencing showed that the abundance of potential Mn(II)-oxidizing bacteria in the GAC media was similar to that in the sand media. However, qPCR results indicated that GAC media colonized dramatically more biomass than sand media, resulting in highly effective Mn(II) removal by GAC filter columns. Under chlorinated conditions, GAC filtration underperformed sand filtration in Mn(II) removal, although activated carbon has been reported to be capable of catalyzing Mn(II) oxidation by chlorine. Fast chlorine decay in GAC filter columns made it hard to sustain chemical Mn(II) oxidation and thus led to less Mn(II) removal. This study highlighted the advantage of biological GAC filtration over sand filtration in Mn(II) removal.

Nanotechnology as an efficient and effective alternative for wastewater treatment: an overview

The increase in the surface and groundwater contamination due to global population growth, industrialization, proliferation of pathogens, emerging pollutants, heavy metals, and scarcity of drinking water represents a critical problem. Because of this problem, particular emphasis will be placed on wastewater recycling. Conventional wastewater treatment methods may be limited due to high investment costs or, in some cases, poor treatment efficiency. To address these issues, it is necessary to continuously evaluate novel technologies that complement and improve these traditional wastewater treatment processes. In this regard, technologies based on nanomaterials are also being studied. These technologies improve wastewater management and constitute one of the main focuses of nanotechnology. The following review describes wastewater's primary biological, organic, and inorganic contaminants. Subsequently, it focuses on the potential of different nanomaterials (metal oxides, carbon-based nanomaterials, cellulose-based nanomaterials), membrane, and nanobioremediation processes for wastewater treatment. The above is evident from the review of various publications. However, nanomaterials' cost, toxicity, and biodegradability need to be addressed before their commercial distribution and scale-up. The development of nanomaterials and nanoproducts must be sustainable and safe throughout the nanoproduct life cycle to meet the requirements of the circular economy.

pH-Tunable electrokinetic movement of droplets

Manipulation and control of droplet motion in an electric field is of interest in biological systems, microfluidics and electrokinetic (EK) separation techniques. In this work, we show that the electrokinetic motion of oil-in-water (O/W) emulsions stabilized by an amphoteric surfactant can be controlled by changing the pH. Amphoteric surfactants carry both positive and negative head groups and change charge under the influence of changing pH, which allows them to impact the surface charge of droplets as a function of pH, and in extension their direction of motion in an electric field. Using a microfluidic system, we evaluate the effect of pH, surfactant concentration and droplet size on the EK velocity of droplets, which is a combination of electrophoresis (EP) and electro-osmotic flow (EOF). We show that by changing the pH from acidic to alkali, the direction of droplet motion in an external electric field changes. The magnitude of the EK velocity at acidic and neutral pH is not significantly altered as a result of the competition of the EP and EOF in the system, which generally have opposite directions. Our results are in good agreement with theoretical predictions for the droplet EP mobility and can thus serve as a verification of the theoretical descriptions. In addition to the pH, the surfactant concentration affects droplet EK velocity, most specifically at pH of 7 which is close to the isoelectric point of the surfactant monomers. At this pH, changing the surfactant concentration changes the direction of droplet motion due the competing effect of the EP and EOF at different surfactant concentrations. By increasing the droplet size, the magnitude of the EK velocity increases because of the larger local ζ-potential of the larger droplets as well as the wall-enhanced effect in the system. The results from this work can be applied to design on-chip droplet separation strategies based on pH variations and are relevant for systems in which pH gradients naturally occur, such as the human body.

NMR-based metabolomics applied to ecotoxicology with zebrafish (Danio rerio) as a prominent model for metabolic profiling and biomarker discovery: Overviewing the most recent approaches

Metabolomics is an innovative approach used in the medical, toxicological, and biological sciences. As an interdisciplinary topic, metabolomics and its relation with the environment and toxicological research are extensive. The use of substances, such as drugs and pesticides, contributes to the continuous releasing of xenobiotics into the environment, harming organisms and their habitats. In this context, fish are important bioindicators of the environmental condition and have often been used as model species. Among them, zebrafish (Danio rerio) presents itself as a versatile and straightforward option due to its unique attributes for research. Zebrafish proves to be a valuable model for toxicity assays and also for metabolomics profiling by analytical tools. Thus, NMR-based metabolomics associated with statistical analysis can reasonably assist researchers in critical factors related to discovering and validating biomarkers through accurate diagnosis. Therefore, this review aimed to report the studies that applied zebrafish as a model for (eco)toxicological assays and essentially utilized NMR-based metabolomics analysis to assess the biochemical profile and thus suggest the potential biological marker.

Optimization of pump scheduling in waterworks considering load balancing using improved genetic algorithm

The water transmission and distribution process of the water supply pump station of the water purification plant plays a key role in the entire urban water supply system. When the requirements of water supply quantity and water pressure are satisfied, the reduction of operating energy consumption of the pump set and improvement of its service life are urgent problems. Therefore, to reduce the cost of water supply pump station, a mathematical model is established to minimize the energy consumption of pump group, the number of pump switches and the load balancing in this paper. In order to solve the pump scheduling problem, a two-stage strategy based on genetic algorithm is proposed. In stage one, the frequency conversion ratio and the number of pumps needed to be turned on at the lowest energy consumption are calculated. In stage two, through the improved genetic algorithm and iterative way to reduce the number of pump switches and load balancing. Finally, a case study from a real waterworks in Suzhou, China is used to verify the validity of the proposed model. Numerical results reveal that the improved genetic algorithm outperforms the competing algorithms. In addition, a proper sensitivity analysis allows assessing the effects under different pump operating conditions.

Confinement effect of network-structured carbon dots/cellulose nanocellulose/magnesium hydroxide for enhanced heavy metal ions capture and immobilization

To solve pollution problem of heavy metal ions (HMIs) and recover them for sustainable development, a high-efficient-sewage treatment agent, carbon dots/cellulose nanofiber/Mg(OH)₂ (CCMg), has been fabricated via a simple hydrothermal method. A variety of characterizations show that cellulose nanofiber (CNF) formed a layered-net structure. Hexagonal Mg(OH)₂ flakes of about 100 nm has been attached on CNF. Carbon dots (CDs) around 10-20 nm in size were produced from CNF and distributed along CNF. The extraordinary structural feature endows CCMg with high removal performance towards HMIs. The up-taken capacities reach 992.8 and 667.3 mg g^-1 for Cd²⁺ and Cu²⁺, respectively. The composite bears excellent durability in treating wastewater. Notably, the qualification of the drinking water can be satisfied while applying CCMg to handle Cu²⁺ wastewater. The mechanism of removal process has been proposed. Practically, Cd²⁺/Cu²⁺ ions were immobilized by CNF due to the space confinement effect. It achieves the facile separation and recovery of HMIs from the sewage, and more importantly, eliminates the risk of secondary contamination.

A Comprehensive Review on Wastewater Nitrogen Removal and Its Recovery Processes

Discharging large amounts of domestic and industrial wastewater drastically increases the reactive nitrogen content in aquatic ecosystems, which causes severe ecological stress and biodiversity loss. This paper reviews three common types of denitrification processes, including physical, chemical, and biological processes, and mainly focuses on the membrane technology for nitrogen recovery. The applicable conditions and effects of various treatment methods, as well as the advantages, disadvantages, and influencing factors of membrane technologies, are summarized. Finally, it is proposed that developing effective combinations of different treatment methods and researching new processes with high efficiency, economy, and energy savings, such as microbial fuel cells and anaerobic osmotic membrane bioreactors, are the research and development directions of wastewater treatment processes.

Interpenetrating polymer networks for desalination and water remediation: a comprehensive review of research trends and prospects

Interpenetrating polymer network (IPN) architectures have gained a lot of interest in recent decades, mainly due to their wide range of applications including water treatment and environmental remediation. IPNs are composed of two or more crosslinked polymeric matrices that are physically entangled but not chemically connected. In polymer science, the interpenetrating network structure with its high polymer chain entanglement is commonly used to generate materials with many functional properties, such as mechanical robustness and adaptable structure. In order to remove a targeted pollutant from contaminated water, it is feasible to modify the network architectures to increase the selectivity by choosing the monomer appropriately. This review aims to give a critical overview of the recent design concepts of IPNs and their applications in desalination and water treatment and their future prospects. This article also discusses the inclusion of inorganic nanoparticles into traditional polymeric membrane networks and its advantages. In the first part, the current scenario for desalination, water pollution and conventional desalination technologies along with their challenges is discussed. Subsequently, the main strategies for the synthesis of semi-IPNs and full-IPNs, and their relevant properties in water remediation are presented based on the nature of the networks and mechanism, with an emphasis on the IPN membrane. This review article has thoroughly investigated and critically assessed published works that describe the latest study on developing IPN membranes, hydrogels and composite materials in water purification and desalination. The goal of this critical analysis is to elicit fresh perspectives regarding the application and advantages of IPNs in desalination and water treatment. This article will also provide a glimpse into future areas of research to address the challenges relating to advanced water treatment as well as its emerging sustainable approaches. The study has put forward a convincing justification and establishes the relevance of IPNs being one of the most intriguing and important areas for achieving a sustainable generation of advanced materials that could benefit mankind.

Development of Ni(II) resistant S. cerevisiae and its application: Adsorption study and modeling

The study aims to develop Ni(II) resistant Saccharomyces cerevisiae to decontaminate high Ni(II) concentrations from an aqueous system. Initially, two different microorganisms were taken: Bacillus circulans MTCC 3161, Saccharomyces cerevisiae. For these two strains, the experiments were carried out for successive screening for survival/tolerance, minimum inhibitory concentration (MIC), and biosorption capacity for Ni(II) from an aqueous solution. Ni(II) resistant Saccharomyces cerevisiae AJ208 showed a MIC of 5500 mg/L for Ni(II). Nucleotide sequences of Saccharomyces cerevisiae AJ208 were deposited in the Gene bank. All experiments were conducted to determine the effects of various physical conditions, such as pH, age and volume of inoculum, temperature, and incubation time, the volume of fermentation medium. The characterization of the Saccharomyces cerevisiae AJ208 was carried out using SEM-EDAX, FTIR. The Langmuir isotherm and pseudo-second-order kinetic models are well fitted with the experimental data. The Langmuir maximum adsorption capacity is 170.06 mg/g. The thermodynamic studies showed the mechanism of Ni(II) removal is an endothermic and spontaneous reaction. The experimental data have been analyzed using statistical method (MLR) and Genetic algorithm (GA). This study reports the highest Ni(II) resistant Saccharomyces cerevisiae AJ208 (5000 mg/L) and also the feasibility of Ni(II) removal from 3000 mg/L initial Ni(II) concentration into an aqueous solution, which could be of great interest as a potential reference strain for Ni(II) removal.

Photocatalytic Performance of Organically Templated Cr-Doped Co3O4 in Remediation of Industrial Wastewater: Effect of Order–Disorder in the Lattice

In photocatalysis, the optical properties and surface parameters significantly affect the catalytic performance. To engineer the optical properties and textural structure, Cr and p-phenylene diamine (PDA) were utilized as dopant and textural structure regulator, respectively. A series of Cr-doped Co3O4 with dopant percentages of 0, 1, 3, and 5, templated PDA at a fixed ratio of 5%, and another un-templated sample with a dopant ratio of 5% were prepared. The co-precipitation method was applied in swift and innovative procedures, where a calculated amount of NaOH was used as a precipitant. The optical properties, dopant concentration quenching, and surface parameters are strongly affected by the order–disorder in the lattice and dopant concentration. The lattice regularity affects the optical properties and the surface parameters along with the dopant concentration. The photocatalysts were evaluated in the disposal of organic pollutants in a representative sample of wastewater collected from different industrial activities. The function of another function was applied to monitor the pollutants' disposal, taking the total organic carbon (TOC) as a function of the pollutants' concentration and the photometric absorbance as a function of the TOC. The kinetic investigation exhibited the significant role of the pore system on the reaction rate.

Iron Oxide Nanoparticle-Based Ferro-Nanofluids for Advanced Technological Applications

Iron oxide nanoparticle (ION)-based ferro-nanofluids (FNs) have been used for different technological applications owing to their excellent magneto-rheological properties. A comprehensive overview of the current advancement of FNs based on IONs for various engineering applications is unquestionably necessary. Hence, in this review article, various important advanced technological applications of ION-based FNs concerning different engineering fields are critically summarized. The chemical engineering applications are mainly focused on mass transfer processes. Similarly, the electrical and electronics engineering applications are mainly focused on magnetic field sensors, FN-based temperature sensors and tilt sensors, microelectromechanical systems (MEMS) and on-chip components, actuators, and cooling for electronic devices and photovoltaic thermal systems. On the other hand, environmental engineering applications encompass water and air purification. Moreover, mechanical engineering or magneto-rheological applications include dampers and sealings. This review article provides up-to-date information related to the technological advancements and emerging trends in ION-based FN research concerning various engineering fields, as well as discusses the challenges and future perspectives.

Emerging technologies for enhanced removal of residual antibiotics from source-separated urine and wastewaters: A review

Antibiotic residues are of significant concern in the ecosystem because of their capacity to mediate antibiotic resistance development among environmental microbes. This paper reviews recent technologies for the abatement of antibiotics from human urine and wastewaters. Antibiotics are widely distributed in the aquatic environment as a result of the discharge of municipal sewage. Their existence is a cause for worry due to the potential ecological impact (for instance, antibiotic resistance) on bacteria in the background. Numerous contaminants that enter wastewater treatment facilities and the aquatic environment, as a result, go undetected. Sludge can act as a medium for some chemicals to concentrate while being treated as wastewater. The most sewage sludge that has undergone treatment is spread on agricultural land without being properly checked for pollutants. The fate of antibiotic residues in soils is hence poorly understood. The idea of the Separation of urine at the source has recently been propagated as a measure to control the flow of pharmaceutical residues into centralized wastewater treatment plants (WWTPs). With the ever increasing acceptance of urine source separation practices, visibility and awareness on dedicated treatement technologies is needed. Human urine, as well as conventional WWTPs, are point sources of pharmaceutical micropollutants contributing to the ubiquitous detection of pharmaceutical residues in the receiving water bodies. Focused post-treatment of source-separated urine includes distillation and nitrification, ammonia stripping, and adsorption processes. Other reviewed methods include physical and biological treatment methods, advanced oxidation processes, and a host of combination treatment methods. All these are aimed at ensuring minimized risk products are returned to the environment.

New energy approaches to the use of waste biosorbents of microalgae Chlorella kessleri (Chlorellaceae, Chlorellales)

The use of microalgae Chlorella kessleri VKPM A1-11 ARM (RF, NPO Algobiotechnology) for environmental and energy purposes is considered. The results of our study of the use of C. kessleri microalgae biomass as a biosorbent to purify model wastewater from Cu2+ ions under static conditions are presented. Biosorption is a promising technology for the treatment of industrial effluents containing various heavy metal compounds, but the issues of economic benefits of using biosorbents, their environmental safety and the cost of disposal of used sorbents are subject to much discussion. The paper proposes to dispose the used biosorbent formed after wastewater treatment from copper as an additional fuel. The copper concentration in the filtrate was determined by colorimetric analysis with sodium diethyldithiocarbamate. The cleaning efficiency and sorption capacity of the dry mass of C. kessleri were obtained by calculation. The maximum sorption capacity for Cu2+ ions was 4.2 mg/g. The purification efficiency reached 87% at the initial concentration of Cu2+ ions being 97 mg/l. Tests to estimate the specific heat of combustion of C. kessleri biomass and used biosorbents based thereon were carried out by the calorimetric method using a bomb calorimeter. The specific heats of combustion were 22,125 kJ/kg and 21,674 kJ/kg, respectively. A comparison of these values with traditional energy carriers is given. A technological scheme has been developed for a waste-free cycle of using C. kessleri to treat wastewater from industrial enterprises with the production of several valuable resources as end products, such as purified water, energy resources, fertilizers, and recycled metals. The obtained results of our study can be applied in technologies for post-treatment of wastewater from various industrial enterprises using biological non-waste resources.

UV-Cured Chitosan-Based Hydrogels Strengthened by Tannic Acid for the Removal of Copper Ions from Water

In this work, a new environmentally friendly material for the removal of heavy metal ions was developed to enhance the adsorption efficiency of photocurable chitosan-based hydrogels (CHg). The acknowledged affinity of tannic acid (TA) to metal ions was investigated to improve the properties of hydrogels obtained from natural and renewable sources (CHg-TA). The hydrogel preparation was performed via a simple two-step method consisting of the photocrosslinking of methacrylated chitosan and its subsequent swelling in the TA solution. The samples were characterized using ATR-FTIR, SEM, and Folin-Ciocalteu (F&C) assay. Moreover, the mechanical properties and the ζ potential of CHg and CHg-TA were tested. The copper ion was selected as a pollutant model. The adsorption capacity (Qe) of CHg and CHg-TA was assessed as a function of pH. Under acidic conditions, CHg-TA shows a higher Qe than CHg through the coordination of copper ions by TA. At an alkaline pH, the phenols convert into a quinone form, decreasing the Qe of CHg-TA, and the performance of CHg was found to be improved. A partial TA release can occur in the copper solution due to its high hydrophilicity and strong acidic pH conditions. Additionally, the reusability of hydrogels was assessed, and the high number of recycling cycles of CHg-TA was related to its high mechanical performance (compression tests). These findings suggest CHg-TA as a promising green candidate for heavy metal ion removal from acidic wastewater.

A green approach for the preparation of ZnO@C nanocomposite using agave americana plant extract with enhanced photodegradation

The present study demonstrates the crucial role of agave americana extract in enhancing the optical properties of zinc oxide (ZnO) through thermal treatment method. Various analytical and surface science techniques have been used to identify the morphology, crystalline structure, chemical composition, and optical properties, including scanning electron microscopy, x-ray diffraction, high resolution transmission electron microscopy (HRTEM), x-ray spectroscopy (EDS) and UV-visible spectroscopy techniques. The physical studies revealed the transformation of ZnO nanorods into nanosheets upon addition of an optimized amount of agave americana extract, which induced large amount of amorphous carbon deposited onto ZnO nanostructures as confirmed by HRTEM analysis. The use of increasing amount of americana extract has significantly reduced the average crystallite size of ZnO nanostructures. The resultant hybrid system of C@ZnO has produced a significant effect on the ultraviolet light-assisted photodegradation of malachite green (MG) dye. The photocatalyst dose was fixed at 10 mg for each study whereas the amount of agave americana extract and MG dye concentration are varied. The functionality of hybrid system was greatly enhanced when the amount of agave americana extract increased while dye concentration kept at lower level. Ultimately, almost 100% degradation efficiency was achieved via the prepared hybrid material, revealing combined contribution from synergy, stabilization of ZnO due to excess of carbon together with the high charge separation rate. The obtained results suggest that the driving role of agave americana extract for surface modification of photocatalyst can be considered for other nanostructured photocatalysts.

Surfactant modified waste ash for the removal of chloro and nitro group substituted benzene from wastewater

A surfactant-modified coal fly ash was developed as a multifunctional adsorbent for the removal of organic pollutants from wastewater. Sodium dodecyl sulfate (SDS) was used to modify the surface of coal fly ash (CFA). The modified CFA was characterized using scanning electron microscopy (SEM), surface porosity analyzer, thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The results showed that loading CFA with SDS not only improved the functionality and surface morphology of the raw ash for the adsorption of organic pollutants, but also enhanced its thermal stability. The efficiency of the modified fly ash was tested in terms of removal of two non-polar organic pollutants namely chlorobenzene (CB) and nitrobenzene (NB) from aqueous phase. The maximum uptake capacity of chlorobenzene and nitrobenzene with SDS-modified coal fly ash (SCFA) was 225 mg/g and 90 mg/g, respectively. The kinetic analysis was done by controlled kinetic models, i.e., pseudo first and second order kinetic models. The results showed that adsorption of CB and NB onto SCFA followed a pseudo second order kinetic model. The adsorption of chlorobenzene was exothermic over the modified adsorbent while nitrobenzene showed an endothermic behavior. The isotherm analysis depicted the multilayer adsorption of both pollutants onto the surface of the surfactant modified adsorbent. This work has shown that surface modification using surfactants can be a viable option to enhance the adsorption capacity of fly ash for pollutants removal.

Cosmetic wastewater treatment technologies: a review

Over the past three decades, environmental concerns about the water pollution have been raised on societal and industrial levels. The presence of pollutants stemming from cosmetic products has been documented in wastewater streams outflowing from industrial as well as wastewater treatment plants. To this end, a series of consistent measures should be taken to prevent emerging contaminants of water resources. This need has driven the development of technologies, in an attempt to mitigate their impact on the environment. This work offers a thorough review of existing knowledge on cosmetic wastewater treatment approaches, including, coagulation, dissolved air flotation, adsorption, activated sludge, biodegradation, constructed wetlands, and advanced oxidation processes. Various studies have already documented the appearance of cosmetics in samples retrieved from wastewater treatment plants (WWTPs), which have definitely promoted our comprehension of the path of cosmetics within the treatment cycle; however, there are still multiple blanks to our knowledge. All treatments have, without exception, their own limitations, not only cost-wise, but also in terms of being feasible, effective, practical, reliable, and environmentally friendly.

A sensitive and rapid method of lead detection using nanoparticle technology based on monoclonal antibody

Lead (Pb) threatens public health due to its toxicity and nonbiodegradable characteristics. It is of significance to develop a sensitive and rapid method for Pb detection. In this study, monoclonal antibodies against Pb were screened with a high affinity constant (K_aff) of 3.56 × 10⁹ L/mol. Au nanosphere particles (AuNS) and Au nanoflower particles (AuNF) were synthesized with a diameter of 15 nm and 60 nm, respectively. The specific anti-Pb antibodies were then immobilized on AuNS and AuNF for probe development. At last, AuNS- and AuNF-based strips were successfully assembled for comparative study, which were able to effectively detect environmental Pb in 10 min. The limits of detection (LODs) were determined to be 3.91 ng/ml and 0.2 ng/ml, respectively. Thus the developed method provides a feasible solution for sensitive and rapid detection of Pb on site, which is beneficial to food safety and pollution control.

The Role of Conventional Methods and Artificial Intelligence in the Wastewater Treatment: A Comprehensive Review

Water pollution is a severe health concern. Several studies have recently demonstrated the efficacy of various approaches for treating wastewater from anthropogenic activities. Wastewater treatment is an artificial procedure that removes contaminants and impurities from wastewater or sewage before discharging the effluent back into the environment. It can also be recycled by being further treated or polished to provide safe quality water for use, such as potable water. Municipal and industrial wastewater treatment systems are designed to create effluent discharged to the surrounding environments and must comply with various authorities’ environmental discharge quality rules. An effective, low-cost, environmentally friendly, and long-term wastewater treatment system is critical to protecting our unique and finite water supplies. Moreover, this paper discusses water pollution classification and the three traditional treatment methods of precipitation/encapsulation, adsorption, and membrane technologies, such as electrodialysis, nanofiltration, reverse osmosis, and other artificial intelligence technology. The treatment performances in terms of application and variables have been fully addressed. The ultimate purpose of wastewater treatment is to protect the environment that is compatible with public health and socioeconomic considerations. Realization of the nature of wastewater is the guiding concept for designing a practical and advanced treatment technology to assure the treated wastewater’s productivity, safety, and quality.

Nanoengineered metal-organic framework for adsorptive and photocatalytic mitigation of pharmaceuticals and pesticide from wastewater

Rapidly expanding water pollution has transformed into significant dangers around the world. In recent years, the pharmaceutical and agriculture field attained enormous progress to meet the necessities of health and life; however, discharge of trace amounts of pharmaceuticals and pesticides into water significantly have a negative influence on human health and the environment. Contamination with these pollutants also constitutes a great threat to the aquatic ecosystem. To deal with the harmful impacts of such pollutants, their expulsion has attracted researchers' interest a lot, and it became essential to figure out techniques suitable for the removal of these pollutants. Thus, many researchers have devoted their efforts to improving the existing technology or providing an alternative strategy to solve this environmental problem. One of the attractive materials for this purpose is metal-organic frameworks (MOFs) due to their superior high surface area, high porosity, and the tunable features of their structures and function. Among various techniques of wastewater treatment, such as biological treatment, advanced oxidation process and membrane technologies, etc., metal-organic frameworks (MOFs) materials are tailorable porous architectures and are viably used as adsorbents or photocatalysts for wastewater treatment due to their porosity, tunable internal structure, and large surface area. MOFs are synthesized by various methods such as solvo/hydrothermal, sonochemical, microwave and mechanochemical methods. Most common method used for the synthesis of MOFs is solvothermal/hydrothermal methods. Herein, this review aims at providing a comprehensive overview of the latest advances in MOFs and their derivatives, focusing on the following aspects: synthesis and applications. This review comprehensively highlights the application of MOFs and nano-MOFs to remove pharmaceuticals and pesticides from wastewater. For the past years, transition metal-based MOFs have been concentrated as photocatalyst/adsorbents in treating contaminated water. However, work on main group metal-based MOFs is not so abundant. Hence, the foremost objective of this review is to present the latest material and references concerning main group element-based MOFs and nanoscale materials derived from them towards wastewater treatment. It summarizes the possible research challenges and directions for MOFs and their derivatives as catalysts applied to wastewater treatment in the future. With the context of recent pioneering studies on main group elements-based MOFs and their derivatives; we hope to stimulate some possibilities for further development, challenges and future perspectives in this field have been highlighted.

Synthesis and Characterization of MWCNT-COOH/Fe3O4 and CNT-COOH/Fe3O4/NiO Nanocomposites: Assessment of Adsorption and Photocatalytic Performance

In this study the adsorption and photodegradation capabilities of modified multi-walled carbon nanotubes (MWCNTs), using tartrazine as a model pollutant, is demonstrated. MWCNT-COOH/Fe₃O₄ and MWCNT-COOH/Fe₃O₄/NiO nanocomposites were prepared by precipitation of metal oxides in the presence of MWCNTs. Their properties were examined by X-ray diffraction in powder (XRD), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, synchrotron-based Scanning PhotoElectron Microscopy (SPEM), and Brunauer-Emmett-Teller (BET) analysis. It was found that the optimal adsorption conditions were pH 4 for MWCNT-COOH/Fe₃O₄ and pH 3 for MWCNT-COOH/Fe₃O₄/NiO, temperature 25 °C, adsorbent dose 1 g L^-1, initial concentration of tartrazine 5 mg L^-1 for MWCNT-COOH/Fe₃O₄ and 10 mg L^-1 for MWCNT-COOH/Fe₃O₄/NiO and contact time 5 min for MWCNT-COOH/Fe₃O₄/NiO and 15 min for MWCNT-COOH/Fe₃O₄. Moreover, the predominant degradation process was elucidated simultaneously, with and without simulated sunlight irradiation, using thermal lens spectrometry (TLS) and UV-Vis absorption spectrophotometry. The results indicated the prevalence of the photodegradation mechanism over adsorption from the beginning of the degradation process.

Physicochemical methods for process wastewater treatment: powerful tools for circular economy in the chemical industry

In the chemical industry, a typical problem is the appropriate treatment of the process wastewaters. The biological treatment cannot be usually applied because of the high content of organochemical compounds. However, phsycicochemical methods can significantly contribute to the proper treatment of the process wastewater and usually also allows the recovery of the polluting materials. This phenomenon opens the application area of physicochemical methods for the treatment of process wastewater and can contribute not only to the aims of the circular economy but also to the zero liquid discharge. Besides literature studies, authors’ own results and innovations have been also presented. The treatment strategy for pharmaceutical process wastewater is reviewed in detail, which also serves to point out that hybrid methods can be usually efficient to solve the primary goal–maximum recovery and reuse of polluting materials.

Electrochemical Methods for Water Purification, Ion Separations, and Energy Conversion

Agricultural development, extensive industrialization, and rapid growth of the global population have inadvertently been accompanied by environmental pollution. Water pollution is exacerbated by the decreasing ability of traditional treatment methods to comply with tightening environmental standards. This review provides a comprehensive description of the principles and applications of electrochemical methods for water purification, ion separations, and energy conversion. Electrochemical methods have attractive features such as compact size, chemical selectivity, broad applicability, and reduced generation of secondary waste. Perhaps the greatest advantage of electrochemical methods, however, is that they remove contaminants directly from the water, while other technologies extract the water from the contaminants, which enables efficient removal of trace pollutants. The review begins with an overview of conventional electrochemical methods, which drive chemical or physical transformations via Faradaic reactions at electrodes, and proceeds to a detailed examination of the two primary mechanisms by which contaminants are separated in nondestructive electrochemical processes, namely electrokinetics and electrosorption. In these sections, special attention is given to emerging methods, such as shock electrodialysis and Faradaic electrosorption. Given the importance of generating clean, renewable energy, which may sometimes be combined with water purification, the review also discusses inverse methods of electrochemical energy conversion based on reverse electrosorption, electrowetting, and electrokinetic phenomena. The review concludes with a discussion of technology comparisons, remaining challenges, and potential innovations for the field such as process intensification and technoeconomic optimization.

Facile Synthesis of n-Fe3O4/ACF Functional Cathode for Efficient Dye Degradation through Heterogeneous E-Fenton Process

In order to put forward an efficient and eco-friendly approach to degrade dye-containing industrial effluents, an n-Fe3O4/ACF nanocomposite was synthesized using the facile precipitation method and applied as a functional cathode for a heterogeneous electro-Fenton (E-Fenton) process. In particular, optimal initial pH value, current density, pole plate spacing, and electrode area were confirmed through systematical experiments as 5.73, 30 mA/cm2, 3 cm, and 2 × 2 cm2, respectively. Under such optimal reaction conditions, 98% of the methylene blue (MB) was degraded by n-Fe3O4/ACF after 2 h of E-Fenton treatment. In addition, n-Fe3O4/ACF could still decolor about 90% of the methylene blue (MB) for five rounds with some reductions in efficiency. Furthermore, results of electrochemical impedance spectroscopy and heterogeneous E-Fenton performance tests indicated that the loading of metal material Fe3O4 could enhance the overall electron transport capacity, which could accelerate the whole degradation processes. Moreover, the rich pores and large specific surface area of n-Fe3O4/ACF provided many active sites, which could greatly improve the efficiency of O2 reduction, promote the generation of H2O2, and shorten the reaction length between •OH and the pollutant groups.