Reusable silicon carbide/lanthanum hydroxide@cellulose composite membranes for selective removal of dyes with the same charge

Dye recovery offers a sustainable approach to treating dyeing wastewater. However, existing adsorbents used in such treatments lack high selectivity for dyes with the same charge and have unsatisfactory recycling properties, which have hindered progress in this field. Herein, the in situ loading of silicon carbide (SiC) and in situ growth of lanthanum hydroxide (La(OH) 3 ) on a cellulose gel-coated filter paper were achieved using a facile dip-coating method. The cellulose used was extracted from bagasse. The resulting membrane exhibits a high rejection rate for the anionic dye Congo red (97%) but a low rejection rate for anionic methyl orange (1.5%) owing to the incomplete coverage of La(OH) 3 by SiC. La(OH) 3 , an electron-deficient compound, shows a strong affinity towards electron-rich organics (e.g. Congo red). Moreover, its electron-deficient characteristic is conducive to separating photoinduced electrons/holes in SiC, improving membrane recyclability by enhancing photodegradation of the adsorbed dyes. Notably, after spraying with a low-concentration cellulose solution, the recyclability of the membrane is further improved because of its increased structural integrity during the recycling process. This work offers a method to utilise waste bagasse for dye recovery while demonstrating the feasibility of La(OH) 3 for photocatalytic applications.