IMPROVED MEMBRANES WITH POLYDOPAMINE COATINGS

摘要

In one embodiment of the disclosure, we provide improved membrane rejection properties for mono and divalent-salts, BOD and COD while also improving resistance to cleaning chemicals and maintaining higher permeability for water using thin polymeric coating. The coating prepared from polydopamine or hydroquinone or catechol or mixtures thereof (termed as Polymeric Coating), is deposited using a base process from Freeman et al. United States Patent number US 8,017,050 issued Sep. 13, 2011 and Freeman et al. in Non-provisional Patent Application 12/939764. In another embodiment of the disclosure, unique coating process steps and conditions are taught to achieve desired functionality. One novel aspect of the process is thickness control via chemical concentration and coating time to tune the rejection properties of the membranes. In another embodiment of the disclosure the coating process discloses removal of polymer particles during the polymerization process for effective utilization of the active chemistry (solution) thus reducing the coating cost. One embodiment discloses reuse of coating solution and discuss lifespan of active solution for polymerization. In one embodiment, we teach details of impact of presence of free CI" and its impact on coated polymer layer. With these details, we teach how to use bleach to strip of a previously applied Polymeric coating and reapply a new coating. We also disclose that due to presence of thin polymeric coating, a sacrificial protection is provided to base membranes such as polyamide RO and NF membranes to protect them from accidental CI exposure. We disclose the interaction details for free Chlorine and polydopamine layer based on contact angle measurements. In one embodiment, we teach details of the process for safe disposal of the coating materials once their useful life has been exhausted. In another embodiment, teach use of hot- water based cleaning and regeneration process (HWC(TM)) for membranes without using any chemical additives.