A reverse osmosis $($RO$)$ membrane was used to treat a feed solution containing sodium chloride as the main electrolyte and nitrobenzene as a trace organic solute at pH $=6.$ Two tests were performed where the RO membrane was operated at two hydraulic pressure levels. The results for the two test are listed as below:

Cl$-($mg$/$L$)$ Nitrobenzene $($mg$/$L$),$ MW $=123$

Jv $($gpd$/$ft$2)$ Feed Product Feed Product

Test $120\mathrm{.}51,44014\mathrm{.}71\mathrm{.}720\mathrm{.}78$

Test $28\mathrm{.}911,43025\mathrm{.}61\mathrm{.}560\mathrm{.}92$

Note: the pH of the feed and product waters were the same $($pH $=6)$ for this medium rejection membrane, i$.$e$.,$ negligible permeation by ion exchange.

$(10$ pts$)$ Based on the RO model with concentration polarization, determine the solute permeability, B$,$ for both chloride and nitrobenzene. Indicate the unit of B$.$

Cp$/($Cf$-$Cp$)=($B$/$Jv$)+($B$/$Dl$)\backslash$delta