Abstract
In the present study, commercial PES, PVDF, PTFE ultrafilter membranes, and two different nanomaterial (TiO2 and TiO2/CNT composite)-covered PVDF ultrafilter membranes (MWCO = 100 kDa) were used for the purification of an industrial oil-contaminated (produced) wastewater, with and without ozone pretreatment to compare the achievable fouling mitigations by the mentioned surface modifications and/or pre-ozonation. Fluxes, filtration resistances, foulings, and purification efficiencies were compared in detail. Pre-ozonation was able to reduce the total filtration resistance in all cases (up to 50%), independently from the membrane material. During the application of nanomaterial-modified membranes were by far the lowest filtration resistances measured, and in these cases, pre-ozonation resulted in a slight further reduction (11–13%) of the total filtration resistance. The oil removal efficiency was 83–91% in the case of commercial membranes and > 98% in the case of modified membranes. Moreover, the highest fluxes (301–362 L m−2 h−1) were also measured in the case of modified membranes. Overall, the utilization of nanomaterial-modified membranes was more beneficial than pre-ozonation, but with the combination of these methods, slightly higher fluxes, lower filtration resistances, and better antifouling properties were achieved; however, pre-ozonation slightly decreased the oil removal efficiency.
Highlights
In the last few decades, water pollution has become a significant global problem due to the rapidly growing population and industrialization (Zhang et al 2018)
The purification efficiency of membrane filtration was determined by measuring the turbidity, chemical oxygen demand (COD), and extractable oil content (TOG/TPH)
On the basis of our previous study (Veréb et al 2018b), just the very brief preozonation of oil-in-water emulsions leads to significantly increased flux during the ultrafiltration; only 2-minlong pre-ozonation was applied, which resulted in 28 ± 2 mg L−1 of absorbed ozone dose
Summary
In the last few decades, water pollution has become a significant global problem due to the rapidly growing population and industrialization (Zhang et al 2018). It was proved to be efficient to decrease membrane fouling in the case of oily wastewaters (Veréb et al 2018b; Xue et al 2016) due to the effective surface charge modification of the oil droplets. The purification efficiency of membrane filtration was determined by measuring the turbidity, chemical oxygen demand (COD), and extractable oil content (TOG/TPH).
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