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Optimization of sulfate removal from brackish water by membrane capacitive deionization (MCDI)
Wangwang Tang1, Di He1, Changyong Zhang1
1School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052, Australia.
Water Research
|May 31, 2017
Summary
Membrane capacitive deionization effectively removes sulfate from brackish water, even with coexisting chloride ions. Optimizing operating parameters like current and flow rate enhances efficiency and reduces energy consumption for practical applications.
Area of Science:
- Environmental Science
- Water Treatment Technologies
- Electrochemistry
Background:
- Sulfate removal from industrial wastewater is a significant environmental challenge.
- Existing methods for sulfate removal are often inefficient, costly, or unsustainable.
- The presence of other ions, like chloride, complicates sulfate removal processes.
Purpose of the Study:
- To investigate the feasibility of sulfate removal from brackish water using single-pass constant-current membrane capacitive deionization (MCDI).
- To explore the effectiveness of reverse-current desorption in the MCDI process.
- To optimize operating parameters for efficient sulfate removal while considering coexisting ions.
Main Methods:
- Utilized single-pass constant-current membrane capacitive deionization (MCDI) with reverse-current desorption.
- Investigated the preferential removal of sulfate over chloride ions.
- Proposed equivalent circuits to model the MCDI system during adsorption and desorption.
- Conducted optimization studies on adsorption current, pump flow rate, ending cell voltage, and desorption current.
Main Results:
- MCDI demonstrated preferential removal of sulfate compared to chloride ions.
- The dynamic variations in cell voltage and charging voltage were successfully explained.
- Optimal operating conditions were identified, balancing water recovery, energy consumption, and sulfate-to-chloride sorption ratio.
- Lower adsorption current and pump flow rate were found to be favorable for practical applications, maintaining effluent sulfate below 300 mg L⁻¹.
Conclusions:
- Single-pass constant-current MCDI with reverse-current desorption is a viable technology for sulfate removal from brackish water.
- Preferential sulfate removal over chloride is achievable, addressing challenges posed by coexisting ions.
- Optimization of operating parameters is crucial for achieving high performance in terms of water recovery, energy efficiency, and ion selectivity.
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