Continuous Electrocoagulation Processes for Industrial Inorganic Pollutants Removal: A Critical Review of Performance and Applications

Electrocoagulation (EC) processes have emerged as an efficient solution for different inorganic and organic effluents. The main characteristics of this versatile process are its ease of operation and low sludge production. The literature indicates that EC can be successfully used as a single process or a step within a combined treatment system. If used in a combined system, this process could be employed as a pre-, a post-, or middle treatment step. Additionally, the EC process has been used in both continuous and batch modes. In most studies, EC has achieved significant improvements in the treated water quality and relatively low total energy consumption. This review presents a comprehensive evaluation and analysis of standalone and combined continuous EC processes. The influence of key operational parameters on continuous EC performance is thoroughly discussed. Furthermore, recent advancements in reactor design, modeling, and process optimization are addressed. The benefits of integrating other treatment processes with the EC process, such as advanced oxidation, membranes, chemical coagulation, and adsorption, are also evaluated. The performance of most standalone and combined EC processes used for organic pollutant treatment and published in the last 25 years is critically analyzed. This review is expected to give researchers many insights to improve their treatment scenario with recent and efficient environmental experiences, sustainability, and circular economy. The clearly presented information is expected to guide researchers in selecting efficient, cost-effective, and time-saving treatment alternatives. The findings ensure the considerable potential of continuous EC treatment processes for organic pollutants. However, more research is warranted to enhance process design, operational efficiency, scale-up, and economic viability.

We introduce a new graphene oxide (GO)-based membrane architecture that hosts cobalt catalysts within its nanoscale pore walls. Such an architecture would not be possible with catalysts in nanoscale, the current benchmark, since they would block the pores or alter the pore structure. Therefore, we developed a new synthesis procedure to load cobalt in an atomically dispersed fashion, the theoretical limit in material downsizing. The use of vitamin C as a mild reducing agent was critical to load Co as dispersed atoms (Co1), preserving the well-stacked 2D structure of GO layers. With the addition of peroxymonosulfate (PMS), the Co1-GO membrane efficiently degraded 1,4-dioxane, a small, neutral pollutant that passes through nanopores in single-pass treatment. The observed 1,4-dioxane degradation kinetics were much faster (>640 times) than the kinetics in suspension and the highest among reported persulfate-based 1,4-dioxane destruction. The capability of the membrane to reject large organic molecules alleviated their effects on radical scavenging. Furthermore, the advanced oxidation also mitigated membrane fouling. The findings of this study present a critical advance toward developing catalytic membranes with which two distinctive and complementary processes, membrane filtration and advanced oxidation, can be combined into a single-step treatment.

Organic micropollutants (OMPs) are detected in sources for drinking water and treatment possibilities are investigated. Innovative removal technologies are available such as membrane filtration and advanced oxidation, but also biological treatment should be considered. By combining an advanced oxidation process with managed aquifer recharge (MAR), two complementary processes are expected to provide a hybrid system for OMP removal, according to the multiple barrier approach. Laboratory scale batch reactor experiments were conducted to investigate the removal of dissolved organic carbon (DOC) and 14 different pharmaceutically active compounds (PhACs) from MAR influent water and water subjected to oxidation, under different process conditions. A DOC removal of 10% was found in water under oxic (aerobic) conditions for batch reactor experiments, a similar value for DOC removal was observed in the field. Batch reactor experiments for the removal of PhACs showed that the removal of pharmaceuticals ranged from negligible to more than 90%. Under oxic conditions, seven out of 14 pharmaceuticals were removed over 90% and 12 out of 14 pharmaceuticals were removed at more than 50% during 30 days of experiments. Under anoxic conditions, four out of 14 pharmaceuticals were removed over 90% and eight out of 14 pharmaceuticals were removed at more than 50% over 30 days' experiments. Carbamazepine and phenazone were persistent both under oxic and anoxic conditions. The PhACs removal efficiency with oxidized water was, for most compounds, comparable to the removal with MAR influent water.

The article contains the results of scientific research and design work related to environmentally safe usage of hydropower potential of the small rivers of the Dnieper basin. The innovative design solutions for extraction of low-grade heat energy of water and systems for its transformation into energy convenient for consumption were offered. It was established that use of renewable low-grade energy of soil is widely used in environmentally safe and economically sound power systems. At the same time hydropower potential is not widely used in hydrothermal heat pump systems. It was proved that existing hydrothermal systems are not always adjusted to actual operating conditions and object location. The evidence was provided that the scientific approach to development of appropriate configuration of hydrothermal collector, to methodology of their optimal mounting and to efficiency determination depending on operating conditions is quite topical issue. The scientific novelty of the new process approach is use of special design of water collector that has modular configuration and consists of several functionally related water sondes. The efficiency of hydrothermal system was scientifically proved. The paper describes the results of experimental research of efficiency of hydrothermal heat pump system where the low-grade heat energy of water is used as a renewable primary heating energy source for functioning of the heat pump. The authors have developed experimental hydrothermal and geothermal heat pump systems to conduct the research. Both collector and ground section of the system have mounted sensors of temperature, pressure and coolant flow velocity. The software for archiving and visualization of obtained data was developed. The research procedure was developed. As part of study, observation data were received and performance efficiency of geothermal and hydrothermal systems was calculated. The comparative analysis of energy systems depending on used renewable energy source was carried out. The conclusion was made that use of hydrothermal heat pump systems is environmentally safe. The data obtained as part of study have great scientific and applied significance for engineering of heat pump energy systems using hydropower potential of the small rivers.

Recent advances in advanced oxidation processes for removal of contaminants from water: A comprehensive review

With the inevitable depletion of the nonrenewable resources of fossil fuels and due to their favorable environmental features, biofuels promise to be the preferred fuels of tomorrow. They can displace petroleum fuels and, in many countries, reduce the dependence on imported fuel. Biofuels, derived from biomass conversion, such as biodiesel, bioethanol, biohydrogen, and biogas, are sustainable and renewable sources of energy, which are also considered CO2 neutral. In addition, burning biofuels results in reduced levels of particulates, carbon oxides and sulfur oxides, emissions compared to fissile fuels. To respond to the increased demand for biofuels, advanced biochemical processes using enzymes are being developed, which are gaining increased global attention. Research in this field aims at improving efficiency, and reducing negative environmental impacts, of production processes, in addition to enhancing the quality of the produced biofuels. Enzymes have been employed to overcome the drawbacks associated with the use of conventional chemical catalysts. For example, biodiesel production by enzymatic catalyzed processes is less energy intensive and more environmental friendly compared to its production by conventional alkaline catalyzed processes. In addition, the biocatalyst allows using unrefined feedstock, including waste oil, readily without the need to separate the free fatty acids that may be present in large amounts in the feedstock. Another example is the use of enzymes for the hydrolysis of cellulose to produce fermentable sugars for bioethanol production. The utility cost of enzymatic hydrolysis is much lower compared to the alternative methods of acidic hydrolysis because it is carried out at mild conditions and does not require subsequent treatment step. There are several obstacles, however, facing the use of enzymes as catalysts for biofuels production, most importantly is their high costs. Therefore, repeated use of the enzymes is essential from the economic point of view, which can be achieved by using them in immobilized form. In a continuous process using immobilized enzyme, the operational stability, the exhaustion of enzyme activity, and inhibition by reactants and/or products play vital roles. The use of membrane bioreactors for the enzymatic processing is increasingly becoming more attractive, as such systems allow continuous separation of products and prevent enzyme inhibition. Research attention is also focused on genetic engineering in enzymes production. Recently, genes of various enzymes have successfully been cloned, and more genes are promised to be cloned rapidly in the coming years. The use of recombinant DNA technology to produce large quantities of recombinant enzymes will help lower the enzymes costs. In addition, protein engineering will help to create novel enzyme proteins that are more resistant and highly thermo-stable. The introduction of a new generation of cheap enzymes, with enhanced activities and resilience, should change the economic balance in favor of enzyme use. It gives me great pleasure to present to you this special issue. The issue covers both basic and applied aspects of using enzymes in the production of various types of biofuels. Articles published present different aspects of current and potential involvement of enzymes in biofuel production.

Water pollution has become a serious concern in the twenty-first century due to the unchecked release of industrial and urban wastewater streams into freshwater sources. Both organic contaminants (OCs) and inorganic contaminants (IOCs) impose grave health and environmental impacts; however, IOCs – particularly heavy metals (lead, arsenic, mercury), anions (fluoride, cyanides, sulfates), mineral acids, and trace elements like selenium – are catastrophic due to bioaccumulation and biomagnification phenomena. Moreover, the presence of IOCs, even in low concentrations, causes significant changes in the physicochemical characteristics of water streams such as pH, biological oxygen demand (BOD), and chemical oxygen demand (COD) and is fatal for aquatic animals, plant life, humans, and environmental sustainability. Therefore, designing and developing commercially viable and highly efficient materials and technologies is imperative for eliminating IOCs from wastewater streams. To date, several wastewater treatment technologies such as photo-catalysis, membrane filtration, coagulation and flocculation, and adsorption have been tested for treating IOC-contaminated water. However, sorption, due to its cost-effectiveness, versatility, and operational simplicity, has emerged as the most promising technology. Among several classes of sorbent materials, biosorbents offer many advantages over traditional adsorbents in terms of scalability, cost-effectiveness, environmental benignity, and technological sustainability. Therefore, a comprehensive review of the role of biosorbents in the removal of IOCs and the present status of the development of these materials is of critical significance to grasp the importance of the research area and ultimately develop novel biosorbents of excellent sorption capacity, outstanding recyclability, promising post-life disposability, and facile commercial viability. Therefore, this chapter explores important aspects of the field, such as sources and hazards of IOCs, along with recent advancements in biosorption technology to eliminate these pollutants from wastewater and future prospects.

A new decentralized two-stage multi-objective control of secondary network driven hybrid microgrid under variable generation and load conditions

Microalgae present an enticing alternative to conventional fossil fuel-dependent technologies for producing hydrogen, offering an intriguing and sustainable energy source. Numerous strains of microalgae are under investigation for their capacity to generate hydrogen, alongside various techniques and breakthroughs being developed to optimize the process. However, significant hurdles must be addressed for commercial viability, including the high manufacturing costs and the necessity for efficient harvesting and sorting methods. This paper delves into several aspects concerning hydrogen synthesis in algae, encompassing microalgae anatomy and physiology, hydrogen synthesis via photosynthesis and dark fermentation, and the integration of microalgal hydrogen synthesis with other renewable energy sources. The potential for microalgal hydrogen generation is considered pivotal in transitioning toward a future reliant on more renewable and sustainable energy sources. This review aims to serve as a valuable resource for researchers, decision-makers, and anyone interested in the advancement of environmentally conscious energy technology. The primary objective of this research paper is to scrutinize the challenges, opportunities, and potential outcomes associated with eco-friendly bio-hydrogen production through algae. It evaluates the current technological hurdles facing bio-hydrogen synthesis from algae.Graphical abstractHighlightsInterest in developing renewable fuels, such as hydrogen from biomass, has surged due to escalating energy demands and the imperative to curtail greenhouse gas emissions. Overview of bio-hydrogen production pathway, reactor designs, and configurations for bio-hydrogen production from bio-algae were explored. Environmental, social sustainability and economic feasibility have been reviewed.DiscussionWill bio-hydrogen from bio-algae be a future renewable energy?Which is the best pathway to produce bio-hydrogen from bio-algae?Regarding greenhouse gas emissions, how does the generation of bio-hydrogen from bio-algae compare to conventional hydrogen production techniques?What difficulties lie in increasing the amount of bio-hydrogen produced by bio-algae to satisfy major energy demands?

Hard-to-abate industries, including steel, cement, and datacenters, are responsible for approximately 30% of global CO2 emissions and present intrinsic challenges for decarbonization due to their reliance on high-temperature heat, continuous processes, and carbon-intensive feedstocks. Achieving the climate goals of the Paris Agreement, requires reducing industrial emissions by up to 90% by 2050, as industrial CO2 could otherwise increase by 12–20% under a business-as-usual scenario. Hydrogen produced via renewable and nuclear energy sources emerges as a pivotal enabler for this transformation: in fact, as energy vector, it allows to overcome both the slow dynamics of nuclear plants and the intermittent and aleatory nature of renewable power plants while it provides a low-carbon, high-energy-density alternative to fossil fuels in energy-intensive processes. In this work, solutions will be presented to decarbonize hard-to-abate industries based on optimal operation and design aimed at costs minimization. The hydrogen value chain requires specialized infrastructure to ensure technical efficiency and economic feasibility. In the production phase, electrolyzers powered by renewable or nuclear energy are coupled with reciprocating or centrifugal compressors and asset performance management (APM) solutions to optimize hydrogen handling and system reliability. Transportation and storage involve centrifugal pumps and expanders to regulate flow and pressure during delivery, while sensor solutions enable continuous leak detection and predictive maintenance. At the utilization stage, hydrogen-fueled gas turbines can deliver high-efficiency, low-carbon power and process heat. Throughout the value chain, advanced Energy Management System (EMS) platforms guarantee the minimization of the Levelized Cost of Hydrogen (LCOH). Each component of the value chain is critical, and an integrated optimal approach, one that, using advanced algorithms for operation and design, seamlessly combines all these complex technologies to minimize the costs of the solution, is key to achieve technical viability and economic competitiveness for hydrogen-based infrastructures, enabling scalable decarbonization solutions. To demonstrate the potential of hydrogen-based technologies, integrated solutions suited for real-world applications in hard-to-abate industries are presented. Specifically, this work shows the optimal design of hydrogen-based infrastructures to decarbonize steel factories, combining electrolyzers, battery energy storage systems (BESS), hydrogen compression, storage technologies, renewable energy sources (RES) and hydrogen-fueled gas turbines. The selected optimal mixes provide the most cost-effective plant for different decarbonization targets. These examples highlight how a coordinated, optimal deployment of different technologies can enable effective and scalable decarbonization pathways. The optimal design and operation of hydrogen-based hybrid power plants applied to steel factories represents a new kind of approach, which is paramount to minimize the LCOH. The results underscore the importance of designing hydrogen ecosystems that optimize each phase of the value chain, ensuring sustainability, reliability, and cost-efficiency as we transition to a low-carbon industrial future.

The advantages of enzyme catalysis are high specificity and (enantio)selectivity, resulting in reactions with little or no by-products. The applications of enzymes in aqueous medium are well established and have been extended to organic synthesis more recently. The two limiting factors for large scale application of enzymes are continuous processing and process scale-up. Process intensification has the potential to overcome these challenges posed by conventional processing methods by incorporating a novel reactor design or by using alternate processing methods. Process intensified reactors like membrane reactors, microreactors, monolithic reactors and rotating disc reactors for enzyme catalyzed reactions will be discussed in this chapter. These reactors have shown an improved performance compared to the enzymatic reactors currently in use, and future opportunities include application for enzymatic catalysis on an industrial scale and advances in reactor design and process control.

To ensure the operational stability of transistor-based biosensors in aqueous electrolytes during multiple measurements, effective electrode passivation is crucially important for reliable and reproducible device performances. This paper presents a highly effective and efficient electrode passivation method using a facile solution-processed self-assembled multilayer (SAML) with excellent insulation property to achieve operational stability and reproducibility of electrolyte-gated transistor (EGT) biosensors. The SAML is created by the consecutive self-assembly of three different molecular layers of 1,10-decanedithiol, vinyl-polyhedral oligomeric silsesquioxane, and 1-octadecanethiol. This passivation enables EGT to operate stably in phosphate-buffered saline (PBS) during repeated measurements over multiple cycles without short-circuiting. The SAML-passivated EGT biosensor is fabricated with a solution-processed In2O3 thin film as an amorphous oxide semiconductor working both as a semiconducting channel in the transistor and as a functionalizable biological interface for a bioreceptor. The SAML-passivated EGT including In2O3 thin film is demonstrated for the detection of Tau protein as a biomarker of Alzheimer's disease while employing a Tau-specific DNA aptamer as a bioreceptor and a PBS solution with a low ionic strength to diminish the charge-screening (Debye length) effect. The SAML-passivated EGT biosensor functionalized with the Tau-specific DNA aptamer exhibits ultrasensitive, quantitative, and reliable detection of Tau protein from 1 × 10-15 to 1 × 10-10 M, covering a much larger range than clinical needs, via changes in different transistor parameters. Therefore, the SAML-based passivation method can be effectively and efficiently utilized for operationally stable and reproducible transistor-based biosensors. Furthermore, this presented strategy can be extensively adapted for advanced biomedical devices and bioelectronics in aqueous or physiological environments.

Active pharmaceutical ingredient (API) production involving continuous processes – A process system engineering (PSE)-assisted design framework

Long-standing research efforts have enabled the widespread introduction of organic field-effect transistors (OFETs) in next-generation technologies. Concurrently, environmental and operational stability is the major bottleneck in commercializing OFETs. The underpinning mechanism behind these instabilities is still elusive. Here we demonstrate the effect of ambient air on the performance of p-type polymer field-effect transistors. After exposure to ambient air, the device showed significant variations in performance parameters for around 30 days, and then relatively stable behaviour was observed. Two competing mechanisms influencing environmental stability are the diffusion of moisture and oxygen in the metal-organic interface and the active organic layer of the OFET. We measured the time-dependent contact and channel resistances to probe which mechanism is dominant. We found that the dominant role in the degradation of the device stability is the channel resistance rather than the contact resistance. Through time-dependent Fourier transform infrared (FTIR) analysis, we systematically prove that moisture and oxygen cause performance variation in OFETs. FTIR spectra revealed that water and oxygen interact with the polymer chain and perturb its conjugation, thus resulting in degraded performance of the device upon prolonged exposure to ambient air. Our results are important in addressing the environmental instability of organic devices.

Electrocoagulation (EC), initially conceived for the treatment of wastewater, is currently the focus of concerted efforts to enhance its energy efficiency, sustainability, and green hydrogen production. The latest developments in the technology are examined in this review, including the fundamentals of EC, its primary applications, key operational parameters, and challenges. There have been notable advancements in reactor design – particularly continuous-flow reactors and single-channel CFSC – as well as in electrode configuration, aiming to improve pollutant removal efficiency and reduce energy consumption. Furthermore, the integration of advanced strategies such as photo electrocoagulation, alternating current (AC), pulsed current (APC), and automatic electrode cleaning contributes to reducing electrode passivation and extending system longevity. EC thus emerges as an attractive technology in the context of the energy transition, notably due to the simultaneous recovery of hydrogen and its compatibility with intermittent renewable energy sources (solar, wind). However, challenges remain, including the intermittency of these energies and the initial implementation costs. Recent research also highlights the benefits of combining EC with other emerging technologies. When associated with techniques such as electrooxidation, photocatalysis, and the coupling of reverse electrodialysis (RED) with EC, there is a significant increase in both the production and purity of hydrogen. This work outlines EC's role as a future-ready technology at the water – energy nexus by showcasing its potential as an independent, low-carbon, and circular solution for sustainable water treatment and by providing a roadmap that connects technological advancements in EC with integration of renewable energy sources and hydrogen recovery.