A novel module for scale inhibitors detection in RO process: Membrane modification and enrichment mechanism

Inventing a method for accurately determining trace scale inhibitor in reverse osmosis (RO) concentrate is of great value for improving RO operation efficiency. In this regard, a module for detecting scale inhibitor polyepoxysuccinic acid (PESA) based on membrane enrichment was designed and a novel polythersulfone (PES) membrane modified by cationic polyacrylamide (CPAM) and pinacyanol chloride (PC) was developed. CPAM adsorption reduced the electronegativity of PES substrate and formed a prefiltering layer, which increased the rejection rate of PESA from 85% to 95%. Meanwhile, PC could complex with PESA to increase the PESA particle size and further improved the detection accuracy. The electrostatic force between the modified layer and PESA revealed that the electronics of CPAM and the complexity of PC can parallel promote the enrichment of PESA. Further, the extensive comparative study between membrane detection and conventional PC detection was performed. The PES-(CPAM/PC) membrane detection showed high sensitivity and the minimum detection concentration was 0.1 mg/L. Compared with PC detection, PES-(CPAM/PC) membrane detection improved durability by 33%. Simultaneously, the change rate of detection results in ionic interference is reduced by 15%. Finally, the practicability of the new module was verified by the PESA concentration detection in four RO concentrate. The enrichment detection method and mechanism provided in this study can provide technical guidance for scale inhibitor monitoring in water treatment.