Enzymatic scavenging of oxygen dissolved in water: Application of response surface methodology in optimization of conditions

In this work, removal of dissolved oxygen in water through reduction by glucose, which was catalyzed by glucose oxidase – catalase enzyme, was studied. Central composite design (CCD) technique was applied to achieve optimum conditions for dissolved oxygen scavenging. Linear, square and interactions between effective parameters were obtained to develop a second order polynomial equation. The adequacy of the obtained model was evaluated by the residual plots, probability-value, coefficient of determination, and Fisher’s variance ratio test. Optimum conditions for activity of two enzymes in water deoxygenation were obtained as follows: pH=5.6, T=40°C, initial substrate concentration [S] = 65.5 mmol/L and glucose oxidase activity [E] = 252 U/Lat excess amount of catalase. The deoxygenation process during 30 seconds, in the optimal conditions, was predicted 98.2%. Practical deoxygenation in the predicted conditions was achieved to be 95.20% which was close to the model prediction

LaBO3 (B = Mn, Fe, Co, Ni, Cu, and Zn) Catalysts for CO + NO Reaction

A series of transition-metal LaBO3 perovskites (B = Mn, Fe, Co, Ni, Cu, and Zn) have been synthesized and tested as catalysts for the simultaneous removal of CO and NO in a fixed-bed reactor. To improve the catalytic activity, LaFeO3, the most active formulation, was modified by partially substituting other active metals (Mn, Co, and Cu) for Fe in the perovskite formulation (LaFe0.7M0.3O3). The results revealed that Mn substitution significantly improved the catalytic activity because it increased the Mn(IV)-to-Mn(III) ratio, leading to the generation of a large amount of structural defects, and also because it increased the amount of reducible active sites.Financial support from the Iran National Science Foundation (INSF) is gratefully acknowledged

Water treatment with CoZnAl-LDH and its mixed metal oxide

Abstract CoZnAl-layered double hydroxide (LDH) was synthesized by homogeneous co-precipitation. CoZnAl-Mixed Metal Oxide (MMO) was prepared by calcining the LDH. The samples' structure and morphology were studied by analytical techniques including X-ray diffraction, N2 adsorption-desorption isotherm, scanning electron microscopy and UV–visible spectroscopy. Acid orange 7 (AO7) adsorption by as-prepared samples was studied. CoZnAl-MMO showed 526.32 mg/g adsorption capacity, higher than that of CoZnAl-LDH, 243.9 mg/g. Kinetic studies confirmed the pseudo-second-order and pseudo-first-order AO7 adsorption kinetics of the LDH and MMO, respectively. AO7 adsorption onto both LDH and MMO fitted the Langmuir isotherm model well. Band gap calculation confirmed the ability of this nano-MMO to operate in the visible light region. It displayed synergetic adsorption-photocatalytic performance under visible light and the removal efficiency was about 97%.</jats:p