Direct contact membrane distillation as an approach for water treatment with phenolic compounds

Membrane distillation is a well-established technology for non-volatile components retention, but the removal of volatile and semi-volatile substances in trace concentration, such as phenols derivates commonly found in surface waters, requires further comprehension. In this context, the direct contact membrane distillation (DCMD) performance was assessed for the retention of fifteen phenolic compounds in surface water by different operating conditions of temperature (40, 50, and 60 degrees C), feed concentration (3, 5, 7, and 10 mu g L-1), and permeate recovery rate (30, 50 and 70%). Kruskal Wallis confirmed a significant difference (p < 0.05) between the global removal of phenolic compounds at different temperatures. The increase in temperature led to a reduction in all compound's removal. As expected, a positive correlation (r(Spearman)>0.8) between the compounds' volatility and their losses was observed. Regarding the feed concentration and the recovery rate, there was no statistical difference between the removal values obtained for the phenolic compounds. This indicates the DCMD strength for that application. However, a trend for flux decay was noticed as the recovery rate (RR) increased, confirmed by temporal trend analysis and Mann-Kendall tests, although the flux decay was relatively low (J/J(0) = 0.89). Aiming for a greater removal and to avoid a reduction in process performance, it is recommended to work with 40 degrees C as feed temperature and a RR prior to the flux decay (RR<30%). Nonetheless, the technology was efficient and did not compromise the permeate quality with >90% efficiency in pollutants removal, even for higher temperatures and RR.

Automated summary

Membrane distillation is effective for retaining non-volatile components, but further research is needed to fully understand the removal of volatile and semi-volatile substances like phenolic compounds in surface waters. The study found that increasing temperature led to decreased removal rates for these compounds, with a positive correlation between volatility and losses observed. Additionally, no statistical difference was found in removal values based on feed concentration and recovery rate, demonstrating the strength of DCMD for this application.