Whey Recovery Using Nanofiltration-like Forward Osmosis: Optical Coherence Tomography Based Approach to Understanding Fouling Behavior

Abstract

Recovering nourishing compounds is of essential significance in the treatment of whey wastewater. It is desirable to enhance the efficiency of whey recovery by forward osmosis (FO) with a nanofiltration (NF)-like membrane, though there is a fundamental challenge standing in the way of investigating the harmful effects of membrane fouling. Optical coherence tomography (OCT) was explored to in situ characterize the fouling behavior in the NF-like FO process for whey recovery. The scientific focus was on the use of a divalent salt as the draw solute, which was required to maintain the transmembrane osmotic pressure difference but could have an elusive impact on the deposition of whey foulants. On the basis of determining the limiting flux, the OCT characterization results were exploited to correlate the morphological and structural evolution of the fouling layer. In addition to the varied effects on the dissipative structures, it was revealed that the back diffusion of divalent cations could increase the rate of initial deposition and yield a higher value of the specific resistance to the transfer of water. This study would help pave the way for implementing whey recovery via an approach based on NF-like FO.

Unraveling Distinct FO Performance of NF-Like Membranes Fabricated by Deposition of Bilayers Containing Polyamines with Minor Structural Differences

“…Both the membrane fouling and cleaning were in situ observed by an OCT system. − Briefly, the OCT system utilized a Fourier-domain bass unit (GANYMEDE-SP5, Thorlabs) to optically section the regions around the feed-membrane interface (through a glass window in the upper compartment of the filtration cell). By scanning at a rate of 1 frame/min, a series of three-dimensional data sets with dimensions of 0.8 mm × 0.2 mm × 1.5 mm (length × width × depth) were obtained, with the length of the scanned matrix being orthogonal to the flow of the feed solution.…”