Preparation of lignosulfonate-based polycatecholamine composite membrane for efficient separation

Effective, safe, and rapid treatment of dye-contaminated wastewater is a challenging task at the global scale. In this study, lignosulfonate-based polycatecholamine and polyethersulfone composite (PES-PCA-LS) membrane was prepared by depositing aminated sodium lignosulfonate (LS) and catechol on polyethersulfone (PES) membrane. This membrane was characterized by various techniques and its performance was investigated using Congo red (CR) as the probe molecule. The results showed that the retention rate of CR solution by PES-PCA-LS membrane was above 99.5%. At this removal rate, one square meter of membrane could treat 351 L of CR waste solution (CR, 100 ppm; salt, 5,000 ppm). However, the retention rates of NaCl, Na 2 SO 4 , and K 2 SO 4 were found to be only 2.8%, 3.5%, and 0.9%, respectively. Besides, this membrane could target selective removal of CR from the mixed solution (CR/Rhodamine B). This PES-PCA-LS membrane also showed excellent cycling performance, with the removal rate maintained at about 97% at the tenth cycle. Thus, this study provides new ideas for the application of industrial lignin in the field of membrane separation for dye/salt or dye/dye mixed solutions.