scholarly journals Theoretical Analysis of Constant Voltage Mode Membrane Capacitive Deionization for Water Softening

Membranes ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 231 ◽  
Author(s):  
Xin Zhang ◽  
Danny Reible
Keyword(s):  
Energy Consumption ◽  
Removal Efficiency ◽  
Process Model ◽  
Tap Water ◽  
Ion Selectivity ◽  
Water Recovery ◽  
Industrial Water ◽  
Capacitive Deionization ◽  
Constant Voltage ◽  
Water Softening

Water softening is desirable to reduce scaling in water infrastructure and to meet industrial water quality needs and consumer preferences. Membrane capacitive deionization (MCDI) can preferentially adsorb divalent ions including calcium and magnesium and thus may be an attractive water softening technology. In this work, a process model incorporating ion exclusion effects was applied to investigate water softening performance including ion selectivity, ion removal efficiency and energy consumption in a constant voltage (CV) mode MCDI. Trade-offs between the simulated Ca2+ selectivity and Ca2+ removal efficiency under varying applied voltage and varying initial concentration ratio of Na+ to Ca2+ were observed. A cut-off CV mode, which was operated to maximize Ca2+ removal efficiency per cycle, was found to lead to a specific energy consumption (SEC) of 0.061 kWh/mole removed Ca2+ for partially softening industrial water and 0.077 kWh/m3 removed Ca2+ for slightly softening tap water at a water recovery of 0.5. This is an order of magnitude less than reported values for other softening techniques. MCDI should be explored more fully as an energy efficient means of water softening.

scholarly journals Energy consumption analysis of constant voltage and constant current operations in capacitive deionization

Desalination ◽  
2016 ◽  
Vol 400 ◽  
pp. 18-24 ◽  
Author(s):  
Yatian Qu ◽  
Patrick G. Campbell ◽  
Lei Gu ◽  
Jennifer M. Knipe ◽  
Ella Dzenitis ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Constant Current ◽  
Capacitive Deionization ◽  
Constant Voltage ◽  
Energy Consumption Analysis

scholarly journals Exploring the Function of Ion-Exchange Membrane in Membrane Capacitive Deionization via a Fully Coupled Two-Dimensional Process Model

Processes ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1312
Author(s):  
Xin Zhang ◽  
Danny Reible
Keyword(s):  
Ion Exchange ◽  
Removal Efficiency ◽  
Cycle Time ◽  
Process Model ◽  
Ion Exchange Membrane ◽  
Membrane Thickness ◽  
Two Dimensional ◽  
Capacitive Deionization ◽  
Exchange Membrane ◽  
Fully Coupled

In the arid west, the freshwater supply of many communities is limited, leading to increased interest in tapping brackish water resources. Although reverse osmosis is the most common technology to upgrade saline waters, there is also interest in developing and improving alternative technologies. Here we focus on membrane capacitive deionization (MCDI), which has attracted broad attention as a portable and energy-efficient desalination technology. In this study, a fully coupled two-dimensional MCDI process model capable of capturing transient ion transport and adsorption behaviors was developed to explore the function of the ion-exchange membrane (IEM) and detect MCDI influencing factors via sensitivity analysis. The IEM enhanced desalination by improving the counter-ions’ flux and increased adsorption in electrodes by encouraging retention of ions in electrode macropores. An optimized cycle time was proposed with maximal salt removal efficiency. The usage of the IEM, high applied voltage, and low flow rate were discovered to enhance this maximal salt removal efficiency. IEM properties including water uptake volume fraction, membrane thickness, and fixed charge density had a marginal impact on cycle time and salt removal efficiency within certain limits, while increasing cell length and electrode thickness and decreasing channel thickness and dispersivity significantly improved overall performance.

scholarly journals Energy consumption in capacitive deionization – Constant current versus constant voltage operation

2018 ◽  
Vol 143 ◽  
pp. 367-375 ◽  
Author(s):  
J.E. Dykstra ◽  
S. Porada ◽  
A. van der Wal ◽  
P.M. Biesheuvel
Keyword(s):  
Energy Consumption ◽  
Constant Current ◽  
Capacitive Deionization ◽  
Constant Voltage

scholarly journals Investigations on the fouling characteristic of humic acid and alginate sodium in capacitive deionization

2021 ◽  
Author(s):  
Huizhong Zhang ◽  
Jiayu Tian ◽  
Xiujuan Hao ◽  
Dongmei Liu ◽  
Fuyi Cui
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
Humic Acid ◽  
Natural Organic Matter ◽  
Water Desalination ◽  
Capacitive Deionization ◽  
Organic Substances ◽  
Water Softening ◽  
Electrical Field ◽  
Adsorption Amount

Abstract Capacitive deionization (CDI) has been investigated for brackish water desalination, selective removal of ions, and water softening. We used humic acid (HA) and alginate sodium (SA) to simulate different kinds of natural organic matter to investigate the fouling phenomena during CDI operation. Adsorption amount and energy efficiency were studied. Results showed that both SA and HA could decrease the removal of NaCl during CDI operation. There existed a slight decrease of energy consumption in SA solutions which was opposite to that in HA solutions. HA can compete with ions adsorbed by electrodes and attach to electrodes adhesively, resulting in co-ion repulsion. SA is not sensitive to electrical field and its fouling is not obvious. The amount of adsorbed Mg2+ would increase from 0.927 mg/g to 1.508 mg/g in ten cycles' operation and the increment of Ca2+ was from 1.885 mg/g to 2.878 mg/g in SA solutions. This increase of adsorption was due to the complexation between SA and cations. Simultaneously, energy consumption was decreased. In HA solutions, energy consumption of Mg2+ and Ca2+ adsorption increased. In ten cycles' operations, both HA and SA could reduce the efficiency of CDI operation. The types of organic substances are important factors in fouling of CDI electrodes.

scholarly journals Analysis of Boron Removal for Reverse Osmosis, Ion Exchange, and Capacitive Deionization

2021 ◽  
Vol 43 (10) ◽  
pp. 654-663
Author(s):  
Yu Chang Kim ◽  
Sungil Lim ◽  
Bangwoo Han ◽  
Sang Bok Kim ◽  
Inyong Park ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Ion Exchange ◽  
Reverse Osmosis ◽  
Ion Selectivity ◽  
Specific Energy Consumption ◽  
Operating Conditions ◽  
Feed Water ◽  
Carbon Electrode ◽  
Capacitive Deionization ◽  
Boron Removal

Objectives : This article provides a comparative analysis of boron removal for brackish water reverse osmosis (BWRO), boron selective ion exchange (IX), or capacitive deionization (CDI) processes. Permeate of 1st-Pass RO process has to be post-treated for additional boron removal. Hence, we experimentally analyzed the performance of boron removal and specific energy consumption (SEC) of three aforementioned processes and investigated whether the processes are suitable for 2nd pass process of RO desalination.Methods : Raw feed water was prepared using NaCl and B(OH)3. Semi-pilot scale RO and IX systems (over 1 m3/hr capacity) and bench scale CDI system (over 2.5 L/min) were tested for performance comparison. Boron concentration was measured using Azomethine-H method for feed and product water. Energy consumption was monitored by using power quality analyzer.Results and Discussion : Each process has its own operating conditions. The RO process required high pH of feed water for high boron removal rate, the IX process was operated below breakthrough point considering adsorption capacity of boron selective resin, and the CDI process didn’t remove boron because chloride ion has higher ion selectivity for carbon electrode than boron. In terms of SEC, the pressure-driven RO process showed the highest SEC among three processes. The CDI process based on electrical adsorption of carbon electrode showed a considerable energy consumption as well. On the other hand, the IX process was operated at low energy consumption because its removal is just based on adsorption-desorption mechanism.Conclusions : The RO and CDI processes have received a lot of attention as leading and emerging technology while the IX process was regarded as a stubborn process because of regeneration of resin and its several segmentalized steps. However, we found that the IX process has a better performance for boron removal and energy consumption.

scholarly journals Analytical Investigation of a Novel System for Combined Dew Point Cooling and Water Recovery

2021 ◽  
Vol 11 (4) ◽  
pp. 1481
Author(s):  
Aleksandra Cichoń ◽  
William Worek
Keyword(s):  
Energy Consumption ◽  
Convective Heat Transfer Coefficient ◽  
Specific Energy Consumption ◽  
Analytical Investigation ◽  
Dew Point ◽  
Energy Utilization ◽  
Coefficient Of Performance ◽  
Air Cooling ◽  
Water Recovery ◽  
Utilization Factor

This paper presents the analytical investigation of a novel system for combined Dew Point Cooling and Water Recovery (DPC-WR system). The operating principle of the presented system is to utilize the dew point cooling phenomenon implemented in two stages in order to obtain both air cooling and water recovery. The system performance is described by different indicators, including the coefficient of performance (COP), gained output ratio (GOR), energy utilization factor (EUF), specific energy consumption (SEC) and specific daily water production (SDWP). The performance indicators are calculated for various climatic zones using a validated analytical model based on the convective heat transfer coefficient. By utilizing the dew point cooling phenomenon, it is possible to minimize the heat and electric energy consumption from external sources, which results in the COP and GOR values being an order of magnitude higher than for other cooling and water recovery technologies. The EUF value of the DPC-WR system ranges from 0.76 to 0.96, with an average of 0.90. The SEC value ranges from 0.5 to 2.0 kWh/m3 and the SDWP value ranges from 100 to 600 L/day/(kg/s). In addition, the DPC-WR system is modular, i.e., it can be multiplied as needed to achieve the required cooling or water recovery capacity.

scholarly journals Long-lasting, monovalent-selective capacitive deionization electrodes

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Eric N. Guyes ◽  
Amit N. Shocron ◽  
Yinke Chen ◽  
Charles E. Diesendruck ◽  
Matthew E. Suss
Keyword(s):  
Water Treatment ◽  
Ionic Conductivity ◽  
Ion Selectivity ◽  
Single Step ◽  
Carbon Electrodes ◽  
Capacitive Deionization ◽  
Treatment Technologies ◽  
Porous Carbon Electrodes ◽  
Monovalent Ion ◽  
Direct Use

AbstractEmerging water purification applications often require tunable and ion-selective technologies. For example, when treating water for direct use in irrigation, often monovalent Na+ must be removed preferentially over divalent minerals, such as Ca2+, to reduce both ionic conductivity and sodium adsorption ratio (SAR). Conventional membrane-based water treatment technologies are either largely non-selective or not dynamically tunable. Capacitive deionization (CDI) is an emerging membraneless technology that employs inexpensive and widely available activated carbon electrodes as the active element. We here show that a CDI cell leveraging sulfonated cathodes can deliver long-lasting, tunable monovalent ion selectivity. For feedwaters containing Na+ and Ca2+, our cell achieves a Na+/Ca2+ separation factor of up to 1.6. To demonstrate the cell longevity, we show that monovalent selectivity is retained over 1000 charge–discharge cycles, the highest cycle life achieved for a membraneless CDI cell with porous carbon electrodes to our knowledge, while requiring an energy consumption of ~0.38 kWh/m3 of treated water. Furthermore, we show substantial and simultaneous reductions of ionic conductivity and SAR, such as from 1.75 to 0.69 mS/cm and 19.8 to 13.3, respectively, demonstrating the potential of such a system towards single-step water treatment of brackish and wastewaters for direct use in irrigation.

scholarly journals Energy Consumption and Greenhouse Gas Emissions of Nickel Products

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5664
Author(s):  
Wenjing Wei ◽  
Peter B. Samuelsson ◽  
Anders Tilliander ◽  
Rutger Gyllenram ◽  
Pär G. Jönsson
Keyword(s):  
Energy Consumption ◽  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Process Model ◽  
Ghg Emissions ◽  
Primary Energy ◽  
Nickel Metal ◽  
Gas Emissions ◽  
Nickel Smelting ◽  
Ore Grade

The primary energy consumption and greenhouse gas emissions from nickel smelting products have been assessed through case studies using a process model based on mass and energy balance. The required primary energy for producing nickel metal, nickel oxide, ferronickel, and nickel pig iron is 174 GJ/t alloy (174 GJ/t contained Ni), 369 GJ/t alloy (485 GJ/t contained Ni), 110 GJ/t alloy (309 GJ/t contained Ni), and 60 GJ/t alloy (598 GJ/t contained Ni), respectively. Furthermore, the associated GHG emissions are 14 tCO2-eq/t alloy (14 tCO2-eq/t contained Ni), 30 t CO2-eq/t alloy (40 t CO2-eq/t contained Ni), 6 t CO2-eq/t alloy (18 t CO2-eq/t contained Ni), and 7 t CO2-eq/t alloy (69 t CO2-eq/t contained Ni). A possible carbon emission reduction can be observed by comparing ore type, ore grade, and electricity source, as well as allocation strategy. The suggested process model overcomes the limitation of a conventional life cycle assessment study which considers the process as a ‘black box’ and allows for an identification of further possibilities to implement sustainable nickel production.

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