2017, Volume 63(67), Issue 2 (June)

Contents

pages 1- 8    Download

Agri-Wastes – Feedstock for Biorefinery

ANA-MARIA CHEŞCĂ, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection
BOGDAN MARIAN TOFANICĂ, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection
ADRIAN CĂTĂLIN PUIȚEL, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection, puitelac@tuiasi.ro
DAN GAVRILESCU, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection

pages 9 - 18     Download
Abstract
Straws and stalks are important categories of lignocellulosic agri- wastes. The availability of these materials is high, taking into account their extended cultivation. Their chemical composition represents an argument for their use as feedstock for papermaking fiber production. In this study, soda pulping process was employed for delignification of wheat straws (Triticum aestivum), corn stalks (Zea mays), rapeseed (Brassica napus) and sunflower (Helianthus annuus). The obtained pulps have been characterized from the perspectives of papermaking. Lignin separated from spent liquors resulted from pulping of agri-wastes is an alternative to increase overall process feasibility. In such context, the separated spent liquors were acid treated for lignins separation, which were further characterized by UV and IR spectroscopy techniques and gel permeation chromatography. The obtained results are important in establishing the potential usage of such lignins.
Keywords: straw; stalks; pulp; paper; lignin.

XRD Analysis of the Structural Properties of Layered Double Hydroxides Comprising Zn and Al Partially Substituted with Cu and Ce and their Derived Mixed Oxides

DIANA GILEA, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection, gilea.diana91@gmail.com
GABRIELA CARJA, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection, gcarja@ch.tuiasi.ro

pages 19 - 25     Download
Abstract
The structural changes of layered double hydroxides (LDHs), when zinc was partially substituted by copper and aluminum was partially substituted by cerium in the layer of the LDHs matrix was monitored by X-ray diffraction (XRD), while the bulk composition of the studied samples was confirmed by X-ray fluorescence (XRF). The substituted samples preserved the layered structure, but the constrictions of the network appeared as a result of the substitution. After calcination at 850°C for 7 h, well crystallized mixed oxides containing copper and cerium were formed. The results point out that the calcination temperature is important to establish the structural features of the resulting mixtures of mixed oxides.
Keywords: layered double hydroxides; XRD; mixed oxides; copper; cerium

Diffusion Coefficients from Sorption Experimental Data

IONUŢ OVIDIU FORŢU, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection
RODICA SERETEANU, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection
EUGENIA TEODORA IACOB TUDOSE, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection, etudose@tuiasi.ro
IOAN MĂMĂLIGĂ, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection

pages 27 -39     Download
Abstract
The diffusion of volatile components trough polymers or other materials of different geometry (plane, spherical or cylindrical) is essential for many industrial applications. In order to characterize the mass transport in these processes, an effective diffusion coefficient is needed. The diffusion coefficients estimation, usually using indirect methods, is based on experimental measurements of volatile components diffusion, retained on sorbents. Hence, the diffusivity is assessed by measuring pressure, sample weight or concentration, externally. These calculations require an appropriate model which describes the processes and the occurring transport phenomena. In this paper we present estimations of the diffusion coefficients using theoretical and experimental methods. These experimental methods are based on the kinetics of the solvent retention within materials of different shapes.
Keywords: cylindrical geometry; diffusion; planar geometry; process; spherical geometry.

Conformational Analysis of Polysiloxanes Substituted with Azobenzene

SIMONA CIOBOTĂRESCU, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection, University of Angers, France Physics Department
ELENA-LUIZA EPURE, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection, lepure@tuiasi.ro
NICOLAE HURDUC, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection

pages 41 - 49     Download
Abstract
This work presents a molecular modeling study with regard to the conformational behaviour of azo-polysiloxane in function of the content in cis azobenzene (CA). Molecular dynamics was used to carry a NVT simulation of azobenzene substituted polysiloxane in bulk. Conformational analysis was performed to determine how the CA concentration affects the polymeric chain’s three-dimensional structure. The radius of gyration was found not to change with the variation of CA content, while the potential energy increased with the increasing of CA percentage. The low change in free volume from one structure to another supports the constant radius of gyration. The correlated results suggest that the CA brings conformational tension on the structure. The macromolecular chain is unable to position itself in a less structural conflictive arrangement and determines a growth in potential energy. More studies are needed for further investigation and to link these findings with simulations in layer and solution.
Keywords: molecular modelling; azo; isomerisation; configuration.

Iron Based Layered Double Hydroxide and its Calcined Derivate as Efficient Photocatalysts in Phenol Removal

ELENA-FLORENTINA GROSU, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection, elena_grosu89@yahoo.com
GABRIELA CARJA, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection, gcarja@ch.tuiasi.ro

pages 51 - 60     Download
Abstract
We report here the fabrication of novel semiconductor photocatalysts with high efficiency in the advanced oxidation reactions. Layered double hydroxides (LDHs) are nontoxic and environmental friendly anionic clays studied due to their photoresponses under UV, visible and solar irradiation. In this work ZnFeAlLDH and the derived mixed oxides obtained after calcination, denoted as ZnFeAl750 were synthesized and used for the first time in the process of phenol photodegradation under irradiation with a solar simulator. The structure and the optical properties of the catalysts were studied by XRD, FTIR and UV-Vis techniques. The photocatalytic tests were done using a solar simulator. The results demonstrate that ZnFeAlLDH has a specific hydrotalcite structure that transformed into highly homogeneous mixed oxides after calcination at 750°C. The tested catalysts are able to absorb light starting from the red region of the spectrum. Results show that the maximum photodegradation of phenol was reached with ZnFeAl750, which removed 70% from the initial concentration of the phenol pollutant after 6 h of irradiation with solar light.
Keywords: LDHs; photocatalyst; mixed oxides; pollutant; phenol; solar photodegradation.

Habilitation Thesis Summary:
Design of High Performing Materials with Increased Thermal Stability: Structure-Property Relationship and Degradation Mechanism

GABRIELA LISA, "Gheorghe Asachi" Technical University of Iaşi, Faculty of Chemical Engineering and Environmental Protection, gapreot@ch.tuiasi.ro

pages 61 - 64     Download