South African Journal of Chemical Engineering (Jul 2024)
Investigation on the stability and durability of PVDF membranes under prolonged exposure to household bleach cleaning agents
Abstract
This study delves into the impact of aging on PVDF membranes due to exposure to various NaOCl-based household bleach products, namely Bayclin, Proclin, and Soclin, over different durations (0, 1, 3, and 5 days). The primary objective is to assess the influence of household bleaches as cleaning agents on the stability and durability of PVDF membranes. Our findings underscore that prolonged exposure to NaOCl-based cleaning agents induces changes in pore structure, morphology, mechanical strength, and flux performance of the membranes owing to oxidation by hypochlorite. However, these alterations are mitigated when using household cleaning agents, particularly Soclin and Proclin. For instance, after 5 days, membranes aged with NaOCl exhibited an enlargement of pore size up to 0.2 mm, whereas those aged with Soclin (MS) and Proclin (MP) only experienced an enlargement to 0.12 mm from the original pore size of 0.05 mm. This increase in pore size is undesirable as it adversely affects the selectivity performance of the membranes. Additionally, the hydrophilicity of membranes was found to be better maintained when aged with household products compared to pure NaOCl, as evidenced by the higher water contact angle observed in MP and MS membranes. Furthermore, the flux recovery ratio (FRR) exhibited an upward trend with prolonged aging duration, with Bayclin showing the highest FRR of 180 %, closely to that of pure NaOCl at nearly 190 %, among the other two products. This significant increase in FRR is undesirable as it results from the enlargement of pore morphology caused by damage from exposure to hypochlorites which is stronger in the chemical-grade NaOCl compared to the household bleach products. In summary, this study highlights that household bleaches, especially Soclin and Proclin, present a promising option in terms of stability for prolonged use. These results are crucial for identifying chemicals that are not only more efficient in the cleaning process but also less damaging to the membranes with good stability in long-term use.
