Application of Ni-doped ZnO rods for the degradation of an azo dye from aqueous solutions

Mehdi Shirzad-Siboni,Mitra Gholami,Jae-Kyu Yang 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.3

Ni-doped ZnO rods were applied as a photocatalyst for the degradation of an azo dye (Reactive Black 5). Effects of solution pH, catalyst dosage, initial RB5 concentration, H2O2 concentration, different purging gases, and type of organic compounds on the removal efficiency of RB5 were studied. Ni-doped ZnO rods were synthesized by co-precipitation method. Neutral pH was selected as an optimal pH condition due to a photo-corrosion of ZnO in acidic and basic conditions. Photocatalytic degradation efficiency of RB5 was increased as the catalyst dosage increased up to 1 g/ L, while it was decreased by increasing initial RB5 concentration. Pseudo-first-order rate constant (kobs) decreased from 0.122 to 0.0051 min−1 and electrical energy per order (EEo) increased from 39.34 to 941.18 (kWh/m3) by increasing RB5 concentration from 5 to 100mg/L, respectively. Photocatalytic degradation efficiency of RB5 increased by increasing H2O2 concentration, but this trend was not observed above 10 mM. Photocatalytic degradation efficiency of RB5 increased in the presence of folic acid and citric acid while interference was observed in the presence of humic acid, EDTA, oxalic acid, and phenol. Photocatalytic activity was maintained even after five successive cycles.

The Removal of Hexavalent Chromium from Aqueous Solutions Using Modified Holly Sawdust: Equilibrium and Kinetics Studies

M. Shirzad Siboni,M. R. Samarghandi,S. Azizian,W. G. Kim,S. M. Lee 대한환경공학회 2011 Environmental Engineering Research Vol.16 No.2

The removal of hexavalent chromium from aqueous solutions onto modified holly sawdust was studied at varying initial hexavalent chromium concentrations, adsorbent doses, pHs and contact times. The removal of hexavalent chromium from aqueous solutions increased with increasing adsorbent dosage and contact time. The percentage of hexavalent chromium removed from the aqueous solutions decreased with increasing hexavalent chromium concentration and pH of the solution. The kinetics of the adsorption of hexavalent chromium onto modified holly sawdust was analyzed using pseudo first-order and pseudo second-order models. The pseudo second-order model described the kinetics of adsorption of hexavalent chromium. The Langmuir and Freundlich isotherm models were used for modeling of the adsorption equilibrium data. The Langmuir isotherm model well described the equilibrium data for the removal of hexavalent chromium by modified holly sawdust. The obtained maximum adsorption capacity was 18.86 mg/g at pH 7. The results showed that modified holly sawdust can be used as a low cost adsorbent for the treatment of aqueous solutions containing chromium.

Removal of Phenol from Aqueous Solutions by Activated Red Mud

Mehdi Shirzad Siboni,Seyed Javad Jafari,Mehrdad Farrokhi,Jae Kyu Yang 대한환경공학회 2013 Environmental Engineering Research Vol.18 No.4

In this work, removal of phenol from aqueous solutions by activated red mud was investigated. Scanning electron microscopy and energy dispersive X-ray spectroscopy was used to observe the morphology and surface components of activated red mud, respectively. The effects of various parameters on the removal efficiency were studied, such as contact time, pH, initial phenol concentration, and adsorbent dosage. The removal percentage of phenol was initially increased, as the solution pH increased from 3 to 7, and then decreased above neutral pH. The removal percentage of phenol was decreased by increasing the initial phenol concentrations. Adsorption results show that equilibrium data follow the Freundlich isotherm, and kinetic data was well described by a pseudo-second-order kinetic model. Experimental results show that the activated red mud can be used to treat aqueous solutions containing phenol, as a low cost adsorbent with high efficiency.

Removal of acid blue 113 and reactive black 5 dye from aqueous solutions by activated red mud

Mehdi Shirzad-Siboni,양재규,Seyed-Javad Jafari,Omid Giahi,김임순,이승목 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4

Removal of acid blue 113 (AB113) and reactive black 5 (RB5) dyes from aqueous solutions by activated red mud was investigated at different reaction parameters. Activated red mud has higher removal efficiency for AB113 than that for RB5. This can be explained by a greater molecular size of RB5 than that of AB113 and by different binding affinity with the surface of the activated red mud. Equilibrium data was fitted well with Freundlich isotherm and the kinetic data followed a pseudo second-order model. Maximum adsorption capacity was 83.33 mg/g and 35.58 mg/g at pH 3 for AB113 and RB5, respectively.

Comparative removal of two textile dyes from aqueous solution by adsorption onto marine-source waste shell : Kinetic and isotherm studies

Mehdi Shirzad-Siboni,Alireza Khataee,주상우,Fatemeh Vafaei 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.8

Scallop shell was used as a low-cost adsorbent for removal of two anionic textile dyes, Reactive Blue 19(RB19) and Acid Cyanine 5 R (AC5R), from aqueous solutions. The adsorbent was characterized using inductivelycoupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), Fourier transform infrared spectroscopy(FT-IR) and scanning electron microscopy (SEM). The dye removal efficiency of scallop shell was determinedas function of contact time, solution pH, initial dye concentration and adsorbent dosage. With increasing dye concentration,the adsorption of both dyes decreased, while it increased with increasing adsorbent dosage. Optimum removalof RB19 and AC5R was achieved at pH=6. Adsorption equilibrium data were well described by the Freundlich model. The maximum dye adsorption capacity of scallop shell as estimated from the Langmuir isotherm was 12.36 and 12.47mg/g for RB19 and AC5R, respectively. The adsorption kinetic data showed excellent correlation with the pseudosecond-order model. It was concluded that scallop shell has a remarkable potential for the sorption of RB19 and AC5Rand can be used for treatment of the dye contaminated wastewater.

Kinetics and equilibrium studies of removal of an azo dye from aqueous solution by adsorption onto scallop

Mehdi Shirzad-Siboni,주상우,Alireza Khataee 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.2

In the present work removal of an azo dye (Reactive Black 5) was investigated from aqueous solution byadsorption onto scallop as a low-cost and widely available adsorbent. The effect of various operationalparameters, such as contact time, pH, initial dye concentration and adsorbent dosage on the removalefficiency of dye was studied. Removal efficiency declined with the increase in solution pH and initial dyeconcentration but with the decrease in adsorbent dosage. Experimental equilibrium and kinetics datawere fitted by Langmuir and Freundlich isotherms and pseudo-first-order and pseudo-second-orderkinetic models, respectively.

Levi problem in complex manifolds

Springer-Verlag 2018 Mathematische Annalen Vol.371 No.3

Pfaff systems, currents and hulls

Springer Science + Business Media 2017 Mathematische Zeitschrift Vol.285 No.3

<P>Let S be a Pfaff system of dimension 1, on a compact complex manifold M. We prove that there is a positive partial derivative partial derivative-closed current T of bidimension (1, 1) and of mass 1 directed by the Pfaff system S. There is no integrability assumption. We also show that local singular solutions always exist. Under a transversality assumption of S on the boundary of an open set U, we prove the existence in U of positive partial derivative partial derivative-closed currents directed by S in U. Using i partial derivative partial derivative-negative currents, we discuss Jensen measures, local maximum principle and hulls with respect to a cone P of smooth functions in the Euclidean complex space, subharmonic in some directions. The case where P is the cone of plurisubharmonic functions is classical. We use the results to describe the harmonicity properties of the solutions of equations of homogeneous, Monge-Ampere type. We also discuss extension problems of positive directed currents.</P>

Equidistribution problems in complex dynamics of higher dimension

Dinh, Tien-Cuong,Sibony, Nessim World Scientific 2017 International Journal of Mathematics Vol.28 No.7

<P>Equidistribution of the orbits of points, subvarieties or of periodic points in complex dynamics is a fundamental problem. It is often related to strong ergodic properties of the dynamical system and to a deep understanding of analytic cycles, or more generally positive closed currents, of arbitrary dimension and degree. The later topic includes the study of the potentials and super-potentials of positive closed currents, their intersection with or without dimension excess. In this paper, we will survey some results and tools developed during the last two decades. Related concepts, new techniques and open problems will be presented.</P>

Effect of Body Position on High-resolution Esophageal Manometry Variables and Final Manometric Diagnosis

( Carlo G Riva ),( Stefano Siboni ),( Davide Ferrari ),( Marco Sozzi ),( Matteo Capuzzo ),( Emanuele Asti ),( Cristina Ogliari ),( Luigi Bonavina ) 대한소화기기능성질환·운동학회(구 대한소화관운동학회) 2020 Journal of Neurogastroenterology and Motility (JNM Vol.26 No.3

Background/Aims According to the Chicago classification version 3.0, high-resolution manometry (HRM) should be performed in the supine position. However, with the patient in the upright/sitting position, the test could more closely simulate real-life behavior and may be better tolerated. We performed a systematic review of the literature to search whether the manometric variables and the final diagnosis are affected by positional changes. Methods A literature search was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. Studies published in English that compared HRM results in different body positions were included. Moreover, the change in diagnosis of esophageal motility disorders according to the shift of body position was investigated. Results Seventeen studies including 1714 patients and healthy volunteers met the inclusion criteria. Six studies showed a significant increase in lower esophageal sphincter basal pressure in the supine position. Integrated relaxation pressure was significantly higher in the supine position in 10 of 13 studies. Distal contractile index was higher in the supine position in 9 out of 10 studies. One hundred and fifty-one patients (16.4%) out of 922 with normal HRM in the supine position were diagnosed with ineffective esophageal motility (IEM) when the test was performed in the upright position (P < 0.001). Conclusions Performing HRM in the upright position affects some variables and may change the final manometric diagnosis. Further studies to determine the normal values in the sitting position are needed. (J Neurogastroenterol Motil 2020;26:335-343)