Understanding the Phenomenon of Copper Ions Release from Copper-Modified TFC Membranes: A Mathematical and Experimental Methodology Using Shrinking Core Model

Abstract

Type of metal and metal-oxide NPs added to modify Thin-Film Composites Reverse Osmosis Membranes (TFC-RO) can alter their anti-biofouling properties by changing the dissolution process. The development of a mathematical model can facilitate the selection of these NPs. This work consists of a mathematical and experimental methodology to understand copper-based NPs dissolution of three copper species incorporated into TFC-RO membranes: Cu-NPs, CuO-NPs and Cu-Oligomer complexes formed in situ during the polymerization process. Biocidal capacity of copper species into the membrane was evaluated using colony forming unit method (CFU) over E. coli. In addition, copper ion release kinetics for both NPs and modified membranes were determined. A model based on the shrinking core model (SCM) was validated and applied to determine the limiting rate step in the dissolution process and simulate the ion release kinetics. Fitted curves reached a good adjustment with the experimental data, demonstrating the SCM can be applied to predict ion release process for copper-based NPs in suspension and the modified membranes. All membranes reached similar inhibition rate >50%, however, differences in the dissolution level of copper-based NPs in membrane were noted, suggesting a dual-type effect that defined the copper toxicity into the membrane, associated to the dissolution capacity and ROS production.

Copper-Modified Polymeric Membranes for Water Treatment: A Comprehensive Review

“…Both mechanisms, contact killing and ion toxicity, lead to an increase in the oxidative stress of the cell membrane through the production of reactive oxygen species (ROS) [ 85 , 100 , 105 ]. Copper can impede the development of bacterial biofilm on a surface acting as a catalyst for redox reactions involving ROS.…”

“…For instance, the oxide-state of copper in CuO-NPs limits its dissolution capacity compared to Cu-NPs, due to the less soluble surface of CuO. On the contrary, elemental Cu-NPs have a rapid initial dissolution that can decrease in prolonged exposure [ 85 , 105 ]. Accordingly, compared to copper salts, both NPs exhibit great ROS production, even at low concentrations of dissolved copper.…”

“…Accordingly, compared to copper salts, both NPs exhibit great ROS production, even at low concentrations of dissolved copper. However, in the case of Cu-NPs, interaction of the nanoparticles with the membrane of bacteria is key to ensure ROS-induced toxicity [ 85 , 109 ]. When Cu-NPs are incorporated in polymeric membranes, they could diminish ROS production due to the reduced direct contact with bacteria.…”

“…The bactericidal effect increases with the copper types incorporated according to the following sequences: Cu-mPD ≥ Cu-NPs >> CuO-NPs ( Figure 5 c). Differences in the dissolution level of copper-based NPs in membrane were noted, suggesting a dual-type effect that defined the copper toxicity into the membrane, associated to the dissolution capacity, which depends on the interactions between the copper and the polyamide (PA) layer of the membrane, and ROS production, which vary depending on the copper type [ 85 ].…”

Influence of Multidimensional Graphene Oxide (GO) Sheets on Anti-Biofouling and Desalination Performance of Thin-Film Composite Membranes: Effects of GO Lateral Sizes and Oxidation Degree

“…To reduce biofouling problems, many researchers have modified the active layer membrane by adding different antimicrobial materials, such as inorganic nanoparticles (NPs) (Zn, TiO 2 , Ag, Cu, CuO, and Fe, among others) [15][16][17][18][19][20][21][22][23]. Moreover, another antimicrobial material that has gained much acceptance in membrane modification is graphene oxide (GO), as it has antimicrobial properties and increases hydrophilicity [24][25][26][27][28].…”