Comparative study of the performance of three cross-flow ceramic membranes for water treatment

Abstract

Several tests using water as effluent are used to analyse the performance of three types of microfiltration cross-flow ceramic membranes. Two of these membranes are commercial (Atech and Membralox/US Filter) and the third one is experimental. The main differences between them lie in their chemical composition (different origin of raw materials) and in their manufacturing process.The results presented here show the dominant effect of the filtering and the gel layer. Both are formed during operation acting as equalising agent between the three membranes. The membranes tested have similar performances in cross-flow operation, although permeability rates for the membrane Membralox/US Filter were about 15% higher. This increase might be due to the smoother surface formed by a second filtering ultrafiltration layer (0.01 µm) of 10 µm width, which probably contributes to a decrease in the thickness of the gel layer formed during operation.Using specific raw materials (non-industrial) as well as a second ultrafiltration layer improves the results in operation (performances and cleaning intervals). However, they are uneconomical because of the extra costs involved.In conclusion, low-cost membranes can achieve similar results to the commercial and more expensive ones opening up their application to new uses and emergent markets.

Removal of char particles from fast pyrolysis bio-oil by microfiltration

“…The spikes in data observed for the 0.5 m membrane at nearly 4 h, and for the 0.8 m membrane at 2 h, occurred due to stopping of the gear pump at these time intervals which resulted in the restarting of the whole microfiltration process. This type of fouling behavior in Membralox ® membranes with water has also been previously reported in literature [17,18]. Elmaleh and Naceur [18] have reported about 85% drop in permeability for the 0.5 m and approximately 90% drop in permeability for the 0.8 m Membralox ® membranes over a running time of 1 h. In comparison we observe a drop of nearly 40% for the 0.5 m and 70% for the 0.8 m membrane, and this drop in permeability occurs after 5-6 h of running water through the membranes.…”

“…The theoretical values are therefore higher by about a factor of three as compared to the initial values from the experiments. This might be attributed to the effects of the resistance of the underlayer and support layer [17], which could not be accounted for in the theoretical calculation, or possibly some adventitious adsorbed material that reduces the experimental flow.…”

“…Each membrane consists of a filtering layer which is about 10-15 m thick. The filtering layer is supported by two layers; an underlayer with an approximate pore size of 10 m and the macroporous support layer [17,18]. The total surface area available for filtration was 55 cm 2 .…”

“…The porosity and tortuosity values for these membranes were taken as 0.4 and 3, respectively [18,23]. The thickness of the active filtering layer ( x) is 15 m [17,18]. Since we have little or no information about the thickness and structure of the underlayer and support layer, we neglected their contribution to the membrane resistance in our computation.…”

Ceramic macromembrane for tangento-axial micro- and ultrafiltration water systems

“…The reduction in permeability was 20% approximately in 24 h. In comparison, this percentage is much lower than those observed in the case of tubular ceramic membranes, which ranged between 28 and 74% according to a study in which several types of membranes were compared [12]. Furthermore, after 24 h, the permeability of the macromembrane remained in 378 L/(m 2 h), while that in the case of the tubular membranes was reduced to 225-285 L/(m 2 h) [12]. So that, even at this initial stage of the project, the process of self-cleaning through tangento-axial drag in the macromembrane seems to meet design expectations.…”