2023, Volume 69(73), Issue 1 (March)

Contents

pages 1- 8   Download

Using XRD and TG/DTG/DSC Studies to Follow the Structural Changes Induced by the Substitution of Al3+ with Ga3+ in 2-D Zn-rich Layered Double Hydroxides Matrices

EUGENIA CORINA IGNAT, “Gheorghe Asachi” Technical University of Iasi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection
GABRIELA CARJA, “Gheorghe Asachi” Technical University of Iasi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection, gcarja@ch.tuiasi.ro

pages 9 – 17   Download
DOI: 10.5281/zenodo.7766972
Abstract
Changes in the structural characteristics of ZnAlLDHs, when Al3+ was replaced by Ga3+ and the structural features of the mixed oxide derived by calcination were rigorously assessed using X-ray diffraction (XRD) and thermogravimetric analysis (TG/DTG/DSC). The results of XRD analysis point out the formation of an LDH phase, without any impurity, with slight differences between samples prepared with specific trivalent cations, in relation to the higher volume of Ga compared to Al, due to their different cationic rays. After the calcination, the LDH structure collapsed and the characteristic XRD reflections of the mixed oxides were obtained. The results of the TG/DTG/DSC analysis indicate that the mass loss reported in terms of moles was almost similar for ZnAlLDH and ZnGaLDH. This demonstrates that the adsorbed water, CO2 and HO- content are similar in the substituted LDH. Hence, this study has revealed that both the composition of the Zn-rich LDHs and the calcination temperature are important parameters for tailoring the structural characteristics of the newly formed ZnO/Ga2O3/ZnGa2O4 homogeneous mixed oxides.
Keywords: Layered double hydroxides, mixed oxides, X-Ray diffraction, thermogravimetric analysis, structural properties

An Approach of Recycling Textile Waste with Industrial Applications

FLORIN ST. C. MUSTATA, “Gheorghe Asachi” Technical University of Iaşi, Faculty of Industrial Design and Business Management, Iaşi, Romania, florinmustata@gmail.com
ANTONELA CURTEZA, “Gheorghe Asachi” Technical University of Iaşi, Faculty of Industrial Design and Business Management, Iaşi, Romania

pages 19 – 25   Download
DOI: 10.5281/zenodo.7767000
Abstract
The fashion industry output a great volume of waste caused by mass production. A great percentage of those garments are disposed in land fields after use, instead of being recycled. In order to prevent the generation of this enormous quantity of waste, the paper will explore methods or strategies to recycle natural and synthetic textile waste. Industrial methods used to recycle textile waste evaluated are: textile recycling to cellulose, separation and conversion of textile waste from wool-polyester and cotton-polyester blends. Associated Recyclability Potential Index (RPI) will be evaluated. Some methods to separate textile waste use selective digestion of wool fibers from wool-polyester mixtures. Some applications use the keratinize in two step process with addition of a reducing agent. The polyester fibers are recovered after the process. We can see that, after the process, the natural fibers are decomposed and the polyester fabric is in good conditions, then can be used for new garment production.
Keywords: Textile waste, environmental strategies, recycling, wool-polyester blends, cotton-polyester blends

Spinning Disc Technology for Textile Wastewater Treatment: Characteristics, Modeling/Optimization Study

CARMEN ZAHARIA, “Gheorghe Asachi” Technical University of Iasi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection
EUGENIA TEODORA IACOB-TUDOSE, “Gheorghe Asachi” Technical University of Iasi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection, etudose@ch.tuiasi.ro

pages 27 – 45   Download
DOI: 10.5281/zenodo.7767015
Abstract
The spinning disc (SD) technology has been used for a number of applications due to its improved attributes. This study focuses on applying SD technology to a textile wastewater treatment in order to improve, without any other additional treatment, its suspended solids and color contents. An experimental planning based on a central compositional rotatable matrix of 23 order is used for modeling. Also, the optimal values of all considered process variables (independent ones: flow rate (z1) within 10-30 L/h experimental range, disc rotational speed (z2) in 200-1100 rpm range, operating time (z3) within 5-30 min range) were established together with the dependent ones: treatment degree of suspended solids content (Y1) and discoloration (Y2). The SD treatment feasibility was reasonably good (max. Y1 = 45.07% and Y2 = 26.59%). Thus, it can minimize color and solids loads within a relatively short time period and can be used within the primary treatment step.
Keywords: discoloration, flow rate, spinning disc (SD) technology modeling and optimization, suspended solids removal, textile wastewater treatment

Environmental Friendly Manufacturing the Geopolymer Foam from Aluminosilicate Wastes Completely Excluding the Cement

BOGDAN VALENTIN PĂUNESCU, Consitrans SA Bucharest, Romania
ADRIAN IOANA, University Politehnica of Bucharest, Faculty of Science and Materials Engineering, Romania
LUCIAN PĂUNESCU, Cosfel Actual SRL Bucharest, Romania, lucianpaunescu16@gmail.com

pages 47 – 56   Download
DOI: 10.5281/zenodo.7767038
Abstract
Geopolymer foam was produced by foaming with hydrogen peroxide (H2O2) of aluminosilicate mixture composed of fly ash and clay brick waste activated with an alkaline activator (water glass and sodium hydroxide in aqueous solution). Other mixture components were expanded perlite as a siliceous additive, a usual fine aggregate (sand), and a less frequently used surfactant (olive oil). The characteristics of the geopolymer foam were: density in the range of 420 - 560 kg/m3, porosity between 71.5 - 76.9%, thermal conductivity within the limits 0.080 - 0.122 W/m·K, and compressive strength between 4.1-5.6 MPa. The low values of density and thermal conductivity indicated good thermal insulation properties of the geopolymer foam, similar to those of this type product presented in the literature. The residual materials contributed to the low level of costs and the complete replacement of ordinary cement in the concrete composition led to the significant reduction of CO2 emissions.
Keywords: geopolymer foam, aluminosilicate binder, coal fly ash, hydrogen peroxide, alkaline activator

Current Trends in The Radar Absorbing Materials

ELISA APOSTOLESCU, University Politehnica of Bucharest, Faculty of Aerospace Engineering, Romania
MIHAELA AURELIA VIZITIU, “Gheorghe Asachi” Technical University of Iasi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection, Iaşi, Romania, mihaela-aurelia.vizitiu@academic.tuiasi.ro

pages 57 – 68   Download
DOI: 10.5281/zenodo.7767050
Abstract
The study of materials with properties of reducing or blocking electromagnetic radiation used in RADAR detection has gained momentum in recent years, especially after the discovery of graphene and metamaterials. The paper aims to present the main absorbing radar materials, the classic ones based on metal or carbon particles but also the recently discovered ones, based on complex mixtures of materials with good electrical, magnetic and thermal properties with dielectric materials.
Keywords: Radar absorbing materials (RAM), graphene, metamaterials, electrical conductivity

Bio-Foaming Agent Used for Preparing Cellular Glass from Recycled Residual Glass

LUCIAN PĂUNESCU, Cosfel Actual SRL Bucharest, Romania, lucianpaunescu16@gmail.com
SORIN-MIRCEA AXINTE, Daily Sourcing & Research SRL Bucharest, Romania; Department of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Romania
ADRIAN IOANA, Faculty of Science and Materials Engineering, University Politehnica of Bucharest, Romania
ENIKÖ VOLCEANOV, Faculty of Science and Materials Engineering, University Politehnica of Bucharest, Romania; Metallurgical Research Institute SA Bucharest, Romania
BOGDAN-VALENTIN PĂUNESCU, Consitrans SA Bucharest, Romania

pages 69 – 81   Download
DOI: 10.5281/zenodo.7767150
Abstract
Cellular glass from powders of recycled residual glass, borax as a fluxing agent, and elm leaves as a bio-foaming agent thermally treated at over 825ºC by unconventional microwave heating (according to the own technique) was experimentally manufactured. The wetted mixture was pressed into a mold and then freely inserted into the inner space of a ceramic tube of high microwave susceptible materials placed inside the microwave oven. Ground elm leaves (51 wt. %) were used for the first time as a bio-foaming agent replacing the much more expensive usual foaming agents. The results showed that the cellular glass in the optimal variant is suitable for its application as a heat-insulating building material, having the apparent density of 0.35 g/cm3, thermal conductivity of 0.074 W/m·K, and porosity of 83.3%. Due to the choice of using borax (6 wt. %), the compressive strength of the foam was improved, the 2.5 MPa value of the optimal variant being only the lowest of the range of 2.5-5.9 MPa achieved in this experiment.
Keywords: cellular glass, residual glass, elm leaf, borax, microwave heating

Benchmarking on Aloe vera Gel Extraction

ABDOURAMANE NSANGOU, Department of Mechanical Engineering, ENSET, University of Douala, Cameroon
DOINA SIBIESCU, “Gheorghe Asachi” Technical University of Iaşi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection, Iaşi, Romania, dsibiesc@tuiasi.ro
PIERRE MARCEL ANICET NOAH, Department of Mechanical Engineering, ENSET, University of Douala, Cameroon
NKEMAJA DYDIMUS EFEZE, HTTTC Bambili-University of Bamenda, Cameroon
FABIEN EBANDA BETENE, Department of Mechanical Engineering, ENSET, University of Douala, Cameroon
BENJAMIN II CASTRO MPAH EKOUME, Department of Mechanical Engineering, ENSET, University of Douala, Cameroon
VALERY HAMBATÉ GOMDJÉ, Departments of Textile and Leather Engineering, ENSPM, University of Maroua, Cameroon

pages 83 – 91   Download
DOI: 10.5281/zenodo.7767181
Abstract
Aloe vera gel is composed of more than 70% saccharide and polysaccharides is the transparent mucilage contained in the parenchymal cells of the fresh Aloe vera leaf. This study objective was to produce a comparison of a set of extraction methods of Aloe vera in the literature. The methodology used is the synthesis of a set of scientific articles, theses, dissertations dealing with the issue of Aloe vera gel extraction. The databases used are (Science Direct, Google Scholar, and ResearchGate). This work studied 6 types of extractions (traditional extraction, Soxhlet extraction, Organic solvent extraction, Ultrasonic extraction, Supercritical extraction and Microwave). These types of extractions were evaluated on several parameters, namely: extraction principles, solvents, extraction time, yield, liquid ratio, gel efficiency and number of extractions. The analysis shows that the quality and yield of Aloe vera gel depends on the type of extraction it undergoes, organic solvent extraction which are: yield, which is 20.67 per kg, liquid ratio 1:15, number of extraction 2 times. Although other extraction methods have some information like traditional extraction the efficiency of gel is poor, the same Aloe vera can undergo three times traditional extraction then Soxhlet extraction the efficiency is improved. Ultrasonic extraction has a high efficiency, 98.06% compared to organic solvent extraction whose yield is 90% and microwave extraction in ethanol solvent with yield of 80%. Each type of extraction has its own principle and the solvent to be used.
Keywords: Aloe vera gel, benchmarking, extraction

Evaluation of the Biosorption Performance of Marine Green Algae Biomass (Ulva lactuca sp.) in the Removal of Inorganic Pollutants

ALINA-ALEXANDRA CIOBANU, “Gheorghe Asachi” Technical University of Iaşi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection, Iaşi, Romania
LOREDANA MUNTEANU, “Gheorghe Asachi” Technical University of Iaşi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection, Iaşi, Romania
GABRIELA VASILE, National Research and Development Institute for Industrial Ecology, Bucharest, Romania
LAURA BULGARIU, “Gheorghe Asachi” Technical University of Iaşi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection, Iaşi, Romania, lbulg@ch.tuiasi.ro

pages 93 – 104   Download
DOI: 10.5281/zenodo.7767225
Abstract
Contamination of water sources with inorganic pollutants (cations or anions) is still a serious environmental problem, for which solutions are still being sought. Therefore, finding a biosorbent that can retain both cations and anions represent a solution to this problem. In addition, if such a biosorbent has a low preparation cost, its use in decontamination processes is recommended. Based on these considerations, in this study, marine green algae biomass (Ulva lactuca sp.) was used as a biosorbent for the removal of Cu(II) (inorganic cation) and HPO42- (inorganic anion) from aqueous media. The experiments were conducted in batch systems, as a function of initial concentration of each inorganic ion, at constant pH (6.53), biosorbent dosage (4.0 g·L-1), contact time (1440 min) and temperature (20 ± 2°C). The maximum biosorption capacities obtained from Langmuir model under these experimental conditions, were 11.44 mg·g-1 for Cu(II) ions and 7.45 mg·g-1 for HPO42- ions, respectively. FTIR spectrometry, SEM microscopy and potentiometric and conductometric titration were used for the characterization of the algae biomass. The structural particularities highlighted by these methods, show that this type of biomass has functional groups on its surface that can interact both with cations and anions from aqueous media. Therefore, its use as a biosorbent in decontamination processes is a viable solution.
Keywords: marine green algae biomass, Ulva lactuca sp., Cu(II) ions, HPO42- ions, biosorption

Methods of Obtaining Magnesium Nanostructured Adsorbent Materials

LUISA MARIA TRIFAȘ, “Gheorghe Asachi” Technical University of Iaşi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection, Iaşi, Romania
GABRIELA CIOBANU, “Gheorghe Asachi” Technical University of Iaşi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection, Iaşi, Romania
MARIA HARJA, “Gheorghe Asachi” Technical University of Iaşi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection, Iaşi, Romania, maria.harja@academic.tuiasi.ro

pages 105 – 113   Download
DOI: 10.5281/zenodo.7767263
Abstract
Researches in material oxides offers solutions in a variety of fields including environment, energy production and storage, biotechnology, medicine and healthcare, electronics, etc. Nanomaterials have concerned attention in recent decades due to their different enhanced properties, such as a large surface, particle size, optical or magnetic properties. To obtain oxide nanomaterials with good performance, the controlled shape of nanoparticles is very important. This paper outlines few methods for the preparation of nanoparticles as well as the advantages of using methods to obtain oxide materials. Conventional methods are still used in the industrial production of many oxide materials, however there is a growing demand for alternative routes to green synthesizes of oxide materials with superior properties. The main current methods of obtaining nanomaterials in the solid state are the sol-gel method, coprecipitation, hydrothermal.
Keywords: nanomaterials, sol-gel method, precipitation/ co-precipitation method, hydrothermal/solvothermal method

Wastes Used for Obtaining Sustainable Building Materials

MIHAI VRABIE, S.C. Gemite RO SRL, Iaşi, Romania; “Gheorghe Asachi” Technical University of Iaşi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection, Iaşi, Romania
MIHAELA CAFTANACHI, S.C. Gemite RO SRL, Iaşi, Romania; “Gheorghe Asachi” Technical University of Iaşi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection, Iaşi, Romania
ALEXANDRU-IOAN COTOFAN, S.C. Gemite RO SRL, Iaşi, Romania
MARIA HARJA, “Gheorghe Asachi” Technical University of Iaşi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection, Iaşi, Romania, maria.harja@academic.tuiasi.ro

pages 115 – 126   Download
DOI: 10.5281/zenodo.7767280
Abstract
Advanced strategies have recently been investigated in order to decrease the environmental pollution, the danger of depleting raw material stocks, and increasing pollution following the release of significant volumes of CO2, resulted by the manufacturing of ordinary cement. The total or partial substitution of cement with a variety of wastes or by-products, from other industrial sectors, is one method of utilizing its to create new building materials. The following wastes can be employed as raw materials in the formulation of advanced materials based on their qualities and chemical content: fly ash, silica fume, bottom ash, phosphogypsum, rice husk ash, red mud, slag, oil fuel ash, etc. For design the building materials with the requirement properties, wastes and by-products utilized as raw materials are activated with different reagents. In this paper wastes from burning processes and few industrial wastes are presented, with refer to most important properties for obtaining the proper building materials.
Keywords: wastes, fly ash, alkali activated materials, alkaline solution, slag, silica fume