Document Type
Dissertation
Date of Award
8-31-2020
Degree Name
Doctor of Philosophy in Chemical Engineering - (Ph.D.)
Department
Chemical, Biological and Pharmaceutical Engineering
First Advisor
Kamalesh K. Sirkar
Second Advisor
Boris Khusid
Third Advisor
S. Basuray
Fourth Advisor
Roman S. Voronov
Fifth Advisor
S. Mitra
Abstract
At neutral pH levels, ammonia in aqueous streams exists in two forms: ammonium ion (NH4+) and dissolved ammonia gas molecules (NH3). Membrane separation serves as a viable option for treatment of ammonia containing effluents. This can be achieved via by stripping NH3 from an ammonia feed solution at feed solution pH > 11 via hollow fiber supported gas membrane (SGM) or removing NH4+ from an ammonia feed solution at feed solution pH < 7 via liquid or polymeric membranes.
The first study reported here examines the influence of feed volumetric flow rates on outlet NH3 concentrations in parallel flow hollow fiber modules (HFM). Comparisons made between model predictions of outlet NH3 concentrations and experimental values allows for tortuosity and membrane mass transfer resistance estimations. NH3 mass transfer via small crossflow HFM is also examined. The lab-scale crossflow HFM used in this study houses the same type of hollow fiber membranes used in the parallel flow module. Hence, the membrane resistance which gives better prediction of outlet NH3 concentrations in the parallel flow module is used to develop shell side correlations for the lab-scale crossflow HFM. A scaled-up model is developed for a large industrial HFM. The scaled-up model provides reasonable insights such as the effects of temperature and feed flow rates on the NH3 separation efficiency. Further, this scaled-up model highlights the significance of the membrane resistance on NH3 separation efficiencies.
A second study on NH3 removal via crossflow HFM elucidates the effects of strip side pH on NH3 transfer rates. This study is also deemed important because the purity of ammonium sulfate which can be used as fertilizer increases with increasing H2SO4 solution pH. On the other hand, results show higher transfer rates at low H2SO4 solution pH.
Further investigations of NH3 via HFM is centered around the effect of water vapor transport on NH3 transfer. Model NH3 feed tank concentrations deviate from experimental results due to transient water vapor partial pressure gradient and heat transfer from the strip to feed side when NH3 reacts with H2SO4 in actual processes.
A third study investigates the removal of ammonia as NH4+ via polymeric membranes. These membranes are classified as polymer inclusion membrane (PIM) and mixed polymer matrix membrane (MPMM). Both classes of membranes consist of a base polymer and extractant. NH4+ transport occurs via PIM but is unsuccessful with MPMM, possibly due to tight connections formed between the base polymer and extractant used in MPMM fabrication. Further, due to possible competition between metals such as Cu2+, Cu2+ extraction is studied. Results also confirm successful extraction with PIM and no extraction with MPMM.
Finally, solvent extraction of NH4+ from an aqueous solution of ammonium chloride (NH4Cl) to an organic phase consisting of bis (2-ethylhexyl) phosphoric acid (D2EHPA) as the organic extractant and sunflower oil as diluent is investigated. The equilibration time of D2EHPA in this system is ascertained and the effect of D2EHPA concentration on the distribution ratio (i.e., ratio of the concentration of NH4+ containing species in the organic phase to NH4+ containing species in the aqueous phase) is examined. The distribution ratio increases with D2EHPA concentration, for the range of D2EHPA concentrations used in this study.
Recommended Citation
Aligwe, Philip A., "Membrane-based removal of ammonia from a waste stream and its recovery" (2020). Dissertations. 1903.
https://digitalcommons.njit.edu/dissertations/1903
