Zinc Oxide‐Based Materials Functionalized with Organic Acids: Synthesis, Characterization, and Adsorption Efficiency for Methylene Blue and Malachite Green Dyes

Abstract Zinc oxide‐based materials functionalized with organic acids such as malonic acid (MA) and oxalic acid (OA) (ZnO‐MA and ZnO‐MA‐OA) have been synthesized by green hydrothermal method. These materials have been characterized by using XRD, FESEM‐EDS, and FTIR analysis. Thermal stability analysis through TG‐DTA technique revealed that these materials are thermally stable. Their utility of these materials for the adsorption of MB (methylene blue) and MG (malachite green) from aqueous medium has been examined. Effects of important factors, such as pH, contact time, concentration of MB and MG, and temperature, on the adsorption efficiency have been scrutinized. The % removal of MB was 93% using ZnO‐MA, while it was 95% with ZnO‐MA‐OA. In the case of MG, the % removal was 94% with ZnO‐MA, and it was 97% using ZnO‐MA‐OA. Kinetic models revealed that pseudo‐second order performs best to describe adsorption process for both dyes in comparison with pseudo‐second order, intraparticle diffusion, and Elovich models. Langmuir and Freundlich isotherms indicate adsorption is not entirely monolayer adsorption but rather a little heterogeneous adsorption as well as partly chemical adsorption provided the driving force. These findings suggest that ZnO‐MA and ZnO‐MA‐OA are potent candidates in removing MB and MG dyes from aqueous media.