Purification of water using surface engineered zeolites

Abstract

Coal fly ash obtained from Coca Cola Company in Harare was utilised in synthesis of zeolites by hydrothermal method using 3M NaOH. The Ze-ZnO nanoflakes and Ze-ZnO nanorods were successfully synthesised using a combination of hydrothermal and one pot homogeneous precipitation method. The zeolitic materials were characterised by FT-IR, BET SEM, XRD and EDX. The Ze-ZnO nanoflake and Ze-ZnO nanorod samples were tested for heavy metal removal capacity by using 300 ppm of Cd and Pb. The adsorption experiment was done using 0.2 g of the Ze-ZnO nanoflakes and Ze-ZnO nanorods under mechanical shaking for 60 mins. The Ze-ZnO nanoflakes proved to be efficient in the removal of heavy metals with adsorption capacities of 74 mg/g and 15.5 mg/g for Pb and Cd respectively compared to 62.5 mg/g and 11.3 mg/g with Ze-ZnO nanorods. The photocatalytic activities of Ze-ZnO nanorods and Ze-ZnO nanoflakes were tested using methylene blue dye as model pollutant under UV irradiation. The degradation efficiencies of Ze-ZnO nanorods and Ze-ZnO nanoflakes were almost the same, 95.61% and 96.87% respectively. The adsorption of heavy metals and degradation of MB dye on Ze-ZnO nanorods followed pseudo second order kinetics. The photocatalytic activities of Ze-ZnO nanoflakes and Ze-ZnO nanorods fitted in the first order kinetic plot. The adsorption isotherms of Pb, Cd and methylene blue dye fitted perfectly into the Langmuir isotherm. The multifunctional characteristics of Ze-ZnO nanorods were established and these included adsorption and photo degradation therefore it can qualify as an alternative to existing water treatment methodologies.