Hollow Fiber Membrane Modules for NOx Removal using a Mixture of NaClO₃ and NaOH Solutions in the Shell Side as Absorbents

Nitrogen oxide (NOx) is one of the polluting gases harmful to humans and the environment. Nitrous oxide gas is mostly found in air, namely nitrogen monoxide (NO) and nitrogen dioxide (NO2). Nitrogen oxide gas in the air, which mostly comes from exhaust gases, needs to be reduced to minimize the threats to humans and the environment and comply with applicable regulations regarding hazards. The absorption process with a membrane contactor is an alternative to reduce NOx concentrations in the air. This study evaluates the hollow fiber membrane modules’ performance in the NOx absorption process using sodium chlorate (NaClO₃) and sodium hydroxide (NaOH) together as an absorbent solution. Based on the experimental results, the NOx reduction efficiency increased from 96.3 to 99.2% and from 99.4 to 99.7% with an increase in the concentration of NaClO₃ from 0.02 to 0.05 M and the number of fibers in the membrane module from 50 to 150. However, the absorption efficiency declined from 99.7 to 99.2% by increasing the feed gas flow rate from 100 to 200 mL/min. The highest value of NOx reduction efficiency, the overall mass transfer coefficient, the flux, and the NOx loading obtained in the study were 99.7%, 0.01743 cm s-1, 9.510×10-8 mmole cm-2 s-1, and 0.026 mole NOx/mole NaClO₃, respectively.