Deposition of powdered activated carbon (PAC) on ultrafiltration (UF) membrane surface: influencing factors and mechanisms

Abstract

The deposition of powdered activated carbon (PAC) on an ultrafiltration (UF) membrane surface, a common phenomenon in the PAC/UF hybrid process, may have a pronounced influence on UF operation. In this study, the influencing factors and mechanisms of the deposition of PAC were systematically investigated. The influencing factors included the organic species, membrane material, PAC size, filtration volume, and cleaning water. The experimental results suggested that PAC itself was rarely deposited on the membrane surface, forming a monolayer. However, in the cases when organic matter was heavily deposited on the membrane surface (e.g., humic acid (HA) and sodium alginate (SA) in the presence of 0.5 mmol/L calcium ions), multilayers of PAC and the organic matter formed; thus, the mass of the deposited PAC significantly increased. The deposition of PAC was barely affected by the membrane material, and decreased as the PAC size increased. Physical cleaning with pure water could effectively detach the deposited PAC. The HA adsorbed by the PAC and the membrane hindered the deposition of PAC because this part of the HA decreased the attractive force between the PAC and the membrane. However, the HA rejected by the membrane promoted the deposition of PAC, as evidenced by the fact that the mass of the deposited PAC increased as the mass of the deposited HA increased. The PAC could be "trapped" in the layer of HA when it formed a cake layer with the HA rejected by the membrane.

Recent Aspects in Membrane Separation for Oil/Water Emulsion

“…[88] On the other way, fouling is an obstacle resulting in increasing energy expenses accompanied by shortened membrane lifespan. [89] Labus et al [90] and Shao et al [91] performed studies for competing fouling problems for membranes presenting that feed water pretreatment before membrane filtration was highly effective and applied widely as a strategy to retard organic fouling. During and after the pretreatment processes, [50,89] the feedwater characteristics are modified, through which adhesion of matter mainly organic on the surface of the membrane and may inside tiny pores was found to decrease quickly.…”

“…Differently, ion exchange processed by ion exchange resins [97] effectively declined the concentration of low lower molecular organic fractions. In addition to the fact that the presence of such adsorbents may have adverse effects [91] as sometimes a combined fouling layer is formed between NOM and adsorption sites on the surface of the membrane. Generally, this is attributed to transfer step presence.…”

“…[99,100] However, excessive remaining ozone may cause irreversible destruction in membrane properties. [91,101] Therefore, any problems need studying as feed OWW changes. That could be caused by the deposition of oil droplets and other undesirable molecules at the membrane surface or inside the pores, resulting in membrane deterioration.…”

Fabrication of Polyethersulfone Membranes Using Nanocarbon as Additive

“…The presence of nanocarbon particles in the polymer system causes changes in macro void structure and the formation of dense structures near the top surface. The mechanism of membrane formation by blending such kind of inorganic additives into polymer solutions is also widely explained in the literature [19,20]. In brief, the morphology changes of composite blend membranes are mostly affected by the concentration of polymer and its additives.…”

Combined Effect of Activated Carbon Particles and Non-Adsorptive Spherical Beads as Fluidized Media on Fouling, Organic Removal and Microbial Communities in Anaerobic Membrane Bioreactor

“…This phenomenon should be more pronounced with larger media size, a higher recirculation rate or mixing intensity through the AFMBR reactor [ 18 ]. As a result, GAC particles that are ground into a smaller size can accelerate the membrane fouling because the particles should be deposited on membrane surface or even within membrane pores due to the formation of very dense cake layers easily [ 18 , 19 , 20 , 21 ]. Fluidizing the media accounts for the major portion of the energy in the operation of AFMBR, but it can depend strongly upon their intrinsic properties [ 5 , 22 , 23 ].…”