An efficient removal of methylene blue dye by adsorption onto carbon dot @ zinc peroxide embedded poly vinyl alcohol (PVA/CZnO2) nano-composite: A novel Reusable adsorbent

Abstract

Both novel nano-composites based on zinc peroxide (ZnO2) and carbon dots (CDots) decorated zinc peroxide (CZnO2) embedded in polyvinyl alcohol, (PVA/ZnO2 and PVA/CZnO2) films, have been successfully designed for pollutant dye removal. The obtained films are scrutinized by using XRD, BET, TEM and SEM microscope. SEM micrograph shows that both nano-composites have good dispersion of nano-particles and some pore structures. PVA/CZnO2 has a high surface area of (241.04 m2 g-1) higher than PVA/ZnO2 (167.17 m2 g-1), according to BET analysis, which gives it the opportunity to be a good catalyst. PVA/CZnO2 catalyst displays ultra-high adsorption capacity against methylene blue (MB). More excitingly, at the same concentration (4 wt%) of each filler, the PVA/CZnO2 catalyst shows the largest adsorption capacity (1972 ± 40 mg/g) where PVA/ZnO2 (1831 ± 20 mg/g) proves the important role of CDots on the adsorption process. More interestingly, 40 mg was the optimum dosage of (PVA/CZnO2) catalyst, which was able to remove MB dye with efficiency up to 98%. The supreme removal efficiency (>98%) of 2000 mg/L of MB dye has been quickly obtained (in 60 min) at the experimental conditions. Langmuir type I model is the adsorption mechanism suggesting MB dye mono-layer formation on the surface of catalyst. Chemisorption is the interaction type between the catalyst and molecules of dye, according to the kinetic model of pseudo-second-order. 75% of loaded-dye is desorbed from the catalyst by soaking it in a solution of pH = 1, according to desorption tests. The reused experiments confirm that the catalyst can be reused for at least 5 runs with minimal loss in its efficiency (~2%).