Highly efficient water purification devices utilizing the microfluidic electrochemical deionization technique

Abstract

A highly efficient water purification device is designed by a combination of electrochemical deionization and microfluidic techniques. The device is constructed with seven layers, in which MnO2 and polypyrrole are employed as positive and negative electrodes, respectively. The advantages of high sensitivity, large surface-to-volume ratio, and short ion diffusion path provided by such a microfluidic device dramatically increase the salt removal capacity (SRC) and salt removal rate (SRR) to 132 mg g−1 and 30 mg g−1 min−1 in the desalination test using a 600 mM NaCl solution. The salt removal percentage in a single-pass test of this microfluidic device using an 8 mM NaCl solution can reach 88 %, 33 times higher than 2.6 % obtained from a macro-scale experiment setup. The SRC remains over 75 % after a 180-cycle stability test. The “memory effect” provides both deionization and concentration ability without using a membrane. Over 160 mg g−1 of NaCl can be transferred from one solution to another under a 120-min deionization/concentration test. This innovative device in a semi-automatic system has been tested in real salinized underground water and seawater with the SRC of 199.4 mg g−1 and 456.6 mg g−1 for removing several ions such as Na+, K+, Mg2+, and Ca2+.