title: Coupling ion-exchangers with inexpensive activated carbon fiber electrodes to enhance the performance of capacitive deionization cells for domestic wastewater desalination.
abstract: A capacitive deionization (CDI) cell was built with electrodes made of an inexpensive commercial activated carbon fiber (ACF), and then modified by incorporating ion-exchangers into the cell compartment. Three modified CDI designs were tested: MCDI - a CDI with electrodes covered by ion-exchange membranes (IEMs) of the same polarity, FCDI - a CDI with electrodes covered by ion-exchange felts (IEFs), and R-MCDI - an MCDI with cell chamber packed with ion-exchange resin (IER) granules. The cell was operated in the batch reactor mode with an initial salt concentration of 1000 mg/L NaCl, a typical level of domestic wastewater. The desalination tests involved investigations of two consecutive operation stages of CDIs: electrical adsorption (at an applied voltage of 1.2 V) and desorption [including short circuit (SC) desorption and discharge (DC) desorption]. The R-MCDI showed the highest electric adsorption as measured in the present study by desalination rate [670 ± 20 mg/(L h)] and salt removal efficiency (90 ± 1%) at 60 min, followed by the MCDI [440 ± 15 mg/(L h) and 60 ± 2%, respectively]. The superior desalination performance of the R-MCDI over other designs was also affirmed by its highest charge efficiency (110 ± 7%) and fastest desorption rates at both the SC [1960 ± 15 mg/(L·h)] and DC [3000 ± 20 mg/(L·h)] modes. The desalination rate and salt removal efficiency of the R-MCDI increased from ∼270 mg/(L h) and 83% to ∼650 mg/(L h) and 98% respectively when the applied voltage increased from 0.6 V to 1.4 V, while decreased slightly when lowering the salt water flow rate that fed into the cell. The packing of IER granules in the R-MCDI provided additional surface area for ions transfer; meanwhile, according to the results of electrochemical impedance spectroscopy (EIS) analysis, it substantially lower down the R-MCDI's ohmic resistance, resulting in improved desalination performance.
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China.
authors.forename: Peng
authors.initials: P
authors.lastname: Liang
authors.forename: Lulu
authors.initials: L
authors.lastname: Yuan
authors.forename: Xufei
authors.initials: X
authors.lastname: Yang
authors.forename: Shaoji
authors.initials: S
authors.lastname: Zhou
authors.forename: Xia
authors.initials: X
authors.lastname: Huang
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry* / Q000191:economics; D000077482:Carbon Fiber; D002606:Charcoal / Q000737:chemistry* / Q000191:economics; D004560:Electricity; D004566:Electrodes / Q000191:economics; D005191:Family Characteristics; D007474:Ion Exchange; D007475:Ion Exchange Resins / Q000737:chemistry*; D008567:Membranes, Artificial; D012212:Rheology; D054712:Salinity; D012965:Sodium Chloride / Q000032:analysis; D062065:Wastewater / Q000737:chemistry* / Q000191:economics; D018508:Water Purification / Q000191:economics* / Q000379:methods*
chemical_list: D002244:Carbon; D000077482:Carbon Fiber; D002606:Charcoal; D007475:Ion Exchange Resins; D008567:Membranes, Artificial; D012965:Sodium Chloride; D062065:Wastewater