THERMAL TREATMENT OF PHOSPHOGYPSUM AS A SET RETARDER FOR PORTLAND CEMENT PRODUCTION

Abstract

Photocatalytic degradation of simulated solution of tetracycline using plant mediated (phytoenhanced) zinc oxide doped with graphitic carbon nitrite was investigated under solar light irradiation for 3 hours. Leaf extract from Moringa oleifera was the source of the phytochemical constituents used in the phyto-enhancement of zinc oxide synthesized by precipitation method using zinc nitrate precursor. Doping was achieved by physically mixing phyto-enhanced synthesized zinc oxide with graphitic carbon nitrite, a light yellow powder gotten from the calcination of melamine at 550 °C. The produced photocatalyst was characterized by FTIR, SEM-EDX, XRD and BET to determine the functional groups, structural morphology, elemental composition, crystallinity, surface area, pore volume and pore diameter. Doped phyto-enhanced zinc oxide showed evolved morphology, revealed loosed structure of uniformly distributed particles with increased surface area. This was confirmed by BET as the surface area (346.1 m2/g) was 10 times greater than that of pure zinc oxide (35.44 m2/g). The pore diameter and volume were 5.428 nm and 0.123 cm3/g respectively compared to 2.965 nm and 0.01259 cm3/g of pure zinc oxide. FTIR spectrum was recorded in the range of 4000–500 cm−1. The FTIR result showed that Zn–O functional group was found at low wavenumber. The XRD pattern of doped phyto-enhanced zinc oxide nanoparticles showed that the substances only belong to ZnO although there were diffraction peaks of other impurities as a result of surface contamination and storage. The average crystallite size of the pure zinc oxide and the doped phyto-enhanced zinc oxide was estimated to be 29.87 nm and 30.27 nm respectively using Debye Scherer equation. The effective operation parameters employed to enhance the photocatalytic process are solution pH, initial concentration and catalyst dosage. The result showed that 98.7% degradation of tetracycline concentration of 5 mg/L was obtained with the optimum doping ratio of 5% (w/w), pH 8 and photocatalyst dosage of 0.2 g/L. This may be attributed to narrow band gab and improved electron/hole separation efficiency. Based on this outcome, it can be concluded that, phytoenhanced zinc oxide doped with graphitic carbon nitrite photocatalyst can effectively degrade tetracycline in pharmaceutical effluents.