Photodegradation of Organic Pollutants Via Carbon Nitride/Graphene-Oxide Nanocomposite Loaded on Polyacrylic Acid Hydrogel with Free Separation

The small size of nano-photocatalyst powders is a limiting factor during the filtration process after waste water treatment. In order to solve this separation issue, graphitic carbon nitride (CN) and graphene-oxide (GO) nanoparticles were loaded on polyacrylic acid (PAA) to fabricate CN/GO/PAA (CGP) composite hydrogel. The hydrogel exhibited adsorption-photocatalytsis synergy ability to remove methylene blue (MB) and rhodamine B (RhB) with visible-light irradiation. During adsorption process in dark, the adsorption capability of CGP hydrogel to MB (20 mg L −1 ) and RhB (10 mg L −1 ) could reach to 18.4 and 18.9 mg g −1 , respectively. Furthermore, CGP 1 hydrogel demonstrated excellent photodegradation capabilities in 30 min irradiation for MB. The reusability of CGP 1 hydrogel was stable in 3 times application for MB, with photodegradation efficiency over 98.0% for each time. The retention rates of CGP 1 kept relatively stable (about 96.0%) for MB purification. However, the photocatalytic capability for RhB declined for 3 times runs. This may due to RhB molecule two-dimensional planar structure causing greater steric hindrance during transfer process into the hydrogels and the surface charges of the hydrogel adsorbent were reduced in acid environment, which were unfavorable for the removal of positively charged RhB. Moreover, swelling behavior was also systematically evaluated. The effects of GO or CN to the swelling ratio was discussed. CGP hydrogel, which combines characteristics of both photocatalysts and polymers, provides reasonable stability and freely separation without using any filter system to solve the separation issue. Graphic Abstract