محسن منصوری

Methylene Blue (MB) is a popular harmful contaminant in wastewater, widely known, in needs to be handled, to maintain bodies of water.Briefly, in this research, the zinc oxide nanophotocatalyst was composited, by co-deposition technique, then doped with lanthanum (50%ZnO-LaO50%). it was used for degrading MB.Structural, optical and morphological properties of composited nano catalyst were characterized by FESEM, EDX, XRD, BET, BJH and FTIR techniques. In the XRD analysis, a new peak developed at many positions (2 theta) which indicate the existence of lanthanum oxides as a new phase.By FT-IR, absorption peaks are defined at (454, 727, 861, 1074, 1427, 3458) cm-1, confirming existence of stretching vibrational modes (Zn–O), (La–Zn–O), (Zn–O), (-C-C), (C=O, C–O), (O–H) consequentially. From BET analysis, the N2 adsorption-desorption isotherm shows that the hysteresis loop develops rapidly at (P/P0 > 0.8), confirming the accumulation of pores. According to BJH Analysis, pore size is 14.1 nm, means the composited catalyst is a mesoporous material. The FE-SEM micrograph revealed existence three different agglomerated particle forms, with a spherical shape and particle sizes between 20-40 nm. The results of EDX spectra corresponds with the XRD, confirm existence three elements La, Zn, and O. with ratios of (48.80, 28,31 and 22.89) wt% respectively, and consequently, it also confirms the existence of La in ZnO. The effects of pH, catalyst loading, H2O2 dose and light intensity were taken into accounts: pH has a positive linearly effect on MB removal, while the curvilinear effect of both catalyst dose and scavenger H2O2 was on MB degradation, it increases as they increase, then the decomposition start to collapse gradually, the maximum value of MB removal at catalyst loading (12) mg and H2O2 (0.44) ml, a positive non-linear effect of the light intensity on the removal, the highest value of removal was obtained at UV intensities (19) watt.The reaction kinetics was studied by carrying out five runs under optimal conditions (catalyst loading = 12 mg, pH = 9, light power = 23 W, and H2O2 content = 0.44 mL), where degradation was completely recorded after (120) minutes.The plot of ln C/Co versus irradiation time confirms that the photo-degradation of methylene blue conforms to a pseudo-first-order kinetic model, in which constant value k was 0.0363 min-1 and the correlation coefficient R2 (0.9917).