Volume 38, Issue 8

Reverse electrodialysis (RED) is among the evolving membrane-based processes available for energy harvesting by mixing water with different salinities. The chemical potential difference causes the movement of cations and anions in opposite directions that can then be transformed into the electrical current at the electrodes by redox reactions. Although several works have shown the possibilities of achieving high power densities through the RED system, the transformation to the industrial-scale stacks remains a challenge particularly in understanding the correlation between ion-exchange membranes (IEMs) and the operating conditions. This work provides an overview of the RED system including its development and modifications of IEM utilized in the RED system. The effects of modified membranes particularly on the psychochemical properties of the membranes and the effects of numerous operating variables are discussed. The prospects of combining the RED system with other technologies such as reverse osmosis, electrodialysis, membrane distillation, heat engine, microbial fuel cell), and flow battery have been summarized based on open-loop and closed-loop configurations. This review attempts to explain the development and prospect of RED technology for salinity gradient power production and further elucidate the integrated RED system as a promising way to harvest energy while reducing the impact of liquid waste disposal on the environment.

Seawater membrane distillation (SWMD) is a promising separation technology due to its ability to operate as a stand-alone desalination unit operation. This paper reviews approaches to improve laboratory-to-pilot-scale MD performance, which comprise operational strategies, module design, and specifically tailored membranes. A detailed comparison of SWMD and sea water reverse osmosis is presented to further analyze the critical shortcomings of SWMD. The unique features of SWMD, namely the ability to operate with extremely high salt rejection and at extreme feed concentration, highlight the SWMD potential to be operated under zero liquid discharge (ZLD) conditions, which results in the production of high-purity water and simultaneous salt recovery, as well as the elimination of the brine disposal cost. However, technical challenges, such as thermal energy requirements, inefficient heat transfer and integration, low water recovery factors, and lack of studies on real-case valuable-salt recovery, are impeding the commercialization of ZLD SWMD. This review highlights the possibility of applying selected strategies to push forward ZLD SWMD commercialization. Suggestions are projected to include intermittent removal of valuable salts, in-depth study on the robustness of novel membranes, module and configuration, utilization of a low-cost heat exchanger, and capital cost reduction in a renewable-energy-integrated SWMD plant.

The reforming of methane is an important industrial process, and reactor modeling and simulation is frequently employed as a design and analysis tool in understanding this process. While much research work is devoted to catalyst formulations, reaction mechanisms, and reactor designs, this review aims to summarize the literature concerning the simulation of methane reforming. Applications in industrial practice are highlighted, and the three main approaches to representing the reactions are briefly discussed. An overview of simulation studies focusing on methane reforming is presented. The three central methods for fixed-bed reactor modeling are discussed. Various approaches and modern examples are discussed, presenting their modeling methods and key findings. The overall objective of this paper is to provide a dedicated review of simulation work done for methane reforming and provide a reference for understanding this field and identifying possible new paths.

m -Cresol containing wastewater has generally become a globally environmental issue due to its refractory and high toxicity towards plants, animals and human being. The development of m -cresol related industries increases the risk of excessive m -cresol discharge, making high efficiency methods to treat m -cresol an urgent topic in both economic and environmental aspects. This review focuses on the chemical treatment methods of m -cresol wastewater, including chemical adsorption, photocatalytic degradation, electrocatalytic degradation and catalytic wet oxidation. The efficiency, cost and process optimization of different methods are discussed in detail. Chemical adsorption is convenient but has relatively low efficiency. Photocatalytic degradation is an easily operated technology with high efficiency, but the selection of catalyst is too limited and the cost of light source is relatively high. Electrocatalytic degradation is time-saving but energy-intensive, and operational difficulty brings a barrier to industrialization. Catalytic wet oxidation (CWO) is highly effective and easily modified, but the performance and stability of catalysts are still very moderate. Following this, the selection and application of different methods regarding the requirement of actual environment are analyzed. Finally, a perspective on the opportunities and development for efficient m -cresol removal method is given.

Cyclone separators have been widely used for gas–particle separation in chemical engineering. However, their enhancement in separation performances usually increases the pressure drop, which inevitably leads to an increase in operating energy consumption. One of the challenging issues is how to reduce the cyclone pressure drop while improving separation performances. To gain insight into the pathways and impacts of cyclone pressure drop reduction, this work reviews the state-of-the-art technical principles, performances and effects, focusing on the processes, mechanisms, and characteristics of pressure drop reduction by inlet/outlet variations, additional auxiliary devices, local cyclone dimension improvement, and global optimization based on intelligent algorithms. The cyclone performances are assessed using a proposed index that combines the Euler number and the square-root particle cut-off Stokes number. It is suggested that the pressure drop and separation capability usually have a dynamic compromise. Considering the comprehensive performances, the technology using helical roof inlet, cross cone, increasing cylindrical height with h / D  = 4.3 ( H / D  = 6.35), and globally optimized design by Sun et al. (2017) are respectively considered to the others. Particularly, the last one is recommended to be more representative in practice. Finally, the key issues to be considered in further research were also prospected.

Solar energy is a clean and abundant energy source. In a photoelectrochemical cell, energy from sunlight is captured and converted into electric power, chemical fuels such as hydrogen is employed to degrade organic pollutants. ZnO is a promising material for photoelectrocatalysis due to its remarkable properties. The aim of this review is to perform an exhaustive revision of nanostructured ZnO synthesis by electrochemical anodization in order to control surface characteristics of this material through anodization parameters such as electrolyte type and concentration, potential, time, temperature, stirring, and post treatment. Finally, application of ZnO nanostructures is overviewed to observe how surface characteristics affected the ZnO photoelectrocatalytic performance.

Cold plasma is a novel nonthermal technology that has been used for preserving and maintaining the quality of food materials. Researchers developed numerous cold plasma equipment to study the effect of plasma on food materials; however, the degree of processing such as flow of plasma species from the source of plasma to the food material and their interaction/diffusion into the food, differs with respect to the equipment. The computational study can simulate the flow dynamics of plasma which in turn can improve the efficiency of processing and design aspects. Computational fluid dynamics (CFD) is the most reliable, cost-effective, and robust numerical tool used for simulating various high-end food processing technologies. In cold plasma processing, computational study aids in revealing the distribution of reactive species and their flow dynamics on the target surface. As CFD studies on plasma interaction with food materials are not available, this review is focused on covering the basics of using CFD in cold plasma simulation. It also explores the significant use of CFD in cold plasma simulation in various sectors along with its possible and futuristic applications in food processing.