Enhancement of forward osmosis (FO) process by capillary force difference in microchannel

This study focused on atrazine concentration by integrating forward osmosis (FO) technology into the microfluidic chip. It mainly investigated the strengthening effect of the capillary force difference caused by different microchannel sizes on the FO process. A 5:1 ratio of 30 % NaCl and 0.001 % [C3H3O2Na]n solution was selected as draw solution because of its high draw flux and low flux decay rate. Qualitative experiments indicated that atrazine concentration rate of FO chip is significantly higher than that of the conventional FO device. The size difference between the upper and lower microchannels is positively related to the auxiliary effect of capillary force. A multi-channel parallel mode was developed in the draw solution side of FO chip to increase the mass transfer efficiency. Results indicated that the increase in the number of microchannels greatly improve the concentration efficiency. Subsequently, a series of low-concentration atrazine solutions were concentrated to determine the detection limit of atrazine. The initially diluted atrazine solution (2.784 x 10- 7 mol/L) below detection limit of ultraviolet spectrophotometer was concentrated about 8 times, reaching the detection limit (2.237 x 10-6 mol/L) in 32 min.