Membrane Rejection of Nitrogen Compounds

Abstract

Rejection characteristics of nitrogen compounds were examined for reverse osmosis, nanofiltration, and low-pressure reverse osmosis membranes. The rejection of nitrogen compounds is explained by integrating experimental results with calculations using the extended Nernst-Planck model coupled with a steric hindrance model. The molecular weight and chemical structure of nitrogen compounds appear to be less important in determining rejection than electrostatic properties. The rejection is greatest when the Donnan potential exceeds 0.05 V or when the ratio of the solute radius to the pore radius is greater than 0.8. The transport of solute in the pore is dominated by diffusion, although convective transport is significant for organic nitrogen compounds. Electromigration contributes negligibly to the overall solute transport in the membrane. Urea, a small organic compound, has lower rejection than ionic compounds such as ammonium, nitrate, and nitrite, indicating the critical role of electrostatic interaction in rejection. This suggests that better treatment efficiency for organic nitrogen compounds can be obtained after ammonification of urea.

A comprehensive review of nanofiltration membranes:Treatment, pretreatment, modelling, and atomic force microscopy

“…Monovalent ions, like nitrates, however, were found to have a lower extent of rejection by NF membranes [ 19,[50][51][52]. Molinari et al [53] compared rejection of several pollutants such as silica, nitrate, manganese and humic acids by means of RO and NF membranes.…”

Assessment of the hindered transport model in predicting the rejection of trace organic compounds by nanofiltration

“…Model calculation in previous studies showed that diffusion was often the predominant mass transport mechanism for a number of inorganic solutes (including mineral ions, arsenic and nitrogen compounds) [3,5,[24][25][26]. In contrast, experimental determination of the diffusion flux by conducting diffusion cell test indicated that diffusion played a minor role in mass transport of a number of organic solutes (including some disinfection by-products and pharmaceuticals (PhACs)) [27,28].…”

“…Successful models can also be utilized for the selection of suitable membranes and optimization of operational conditions. The DSPM&DE (Donnan and Steric Pore Model and Dielectric Effect) is an NF model which was found to be able to predict the rejection ratios for a variety of inorganic solutes with fairly high accuracy [1,3]. The DSPM&DE model is relatively simple to use and involves only three adjustable parameters including average pore size, effective thickness and surface charge density of the membrane [1,4,5].…”

Impact of acids on the structure and composition of Linde Type A zeolites for use in reverse osmosis membranes for recovery of urine-containing wastewaters

“…The low pH and complex composition of the wastewater brine present challenges for materials selection, as both chemical resistance to all components and acid stability are required. Commercial reverse osmosis (RO) membranes do not adequately reject small, neutral organic compounds found in urine [4][5][6], and the highly acidic wastewater brine would degrade the polyamide active layer, destroying the selectivity of the membrane [7]. http To meet the increased water recovery goals of NASA, our research aims to investigate the suitability of polymer/zeolite nanocomposite membranes and pure zeolite membranes for recovery of this wastewater brine through osmotic processes.…”