Optimizing Ammonia Separation from Thermophilic Digestate: The Combined Effect of pH and Thermal Gradients in Direct Contact Membrane Distillation
Year: 2025
Type: article
Abstract: Ammonia recovery from synthetic thermophilic anaerobic digestate was achieved through Direct Contact Membrane Distillation (DCMD) using hydrophobic flat-sheet membranes under different operating conditions. The influence of temperature gradients (0 °C, 20 °C, 35 °C, and 45 °C) and pH levels of the thermophilic anaerobic sludge (7.8, 8.2, 9, and 12) was investigated. The process utilized a DCMD setup with hydrophobic PTFE membranes of 0.22 µm nominal pore radius, and receiving solutions consisting of deionized water and 1 M H2SO4. The best results were obtained with isothermal distillation and high pH levels in the feed. Isothermal distillation at 65 °C (a temperature gradient of 0 °C), with 1 M H2SO4 as the receiving solution, and at pH levels 8.2 and 12, yielded NH3 recoveries of 36.4 ± 1.6% and 100.0 ± 0.1%, respectively. Under the same conditions, the molar fluxes were 0.63 ± 0.01 mol TAN m−2 h−1 and 1.84 ± 0.01 mol TAN m−2 h−1, respectively. It is worth noting that some very low depositions on the membrane were detected, leading to changes in the surface morphology, as confirmed by atomic force microscopy.
Source: Membranes
Authors: Fanny Rivera, Luis Villarreal, Pedro Prádanos, Raúl Muñoz, Laura Palacio, Antonio Hernández
Institution: Universidad de Valladolid
Language: English
Subfield: Water Science and Technology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,654
OpenAlex ID: W4416596441