Daniela Suteu

Green synthesis of the silver nanoparticles mediated by pullulan and 6-carboxypullulan

Unoxidized and carboxylated pullulan (obtained by pullulan oxidation using TEMPO-sodium hypochlorite-sodium bromide system) have been used as mediators for the silver nanoparticles formation (AgNPs), under environment-friendly conditions: using aqueous solutions, room temperature and notably, by using both mediators as reducing and stabilizing agents. The formation of AgNPs was first screened by measuring the surface plasmon resonance peak in the range of 380-440 nm using UV-vis spectroscopy. The morphology of the synthesized silver nanoparticles was determined by TEM, which indicated that the AgNPs differ on shape and thickness of the polymer shell by varying the silver nitrate concentration, different size and shape of AgNPs was achieved. The presence of elemental silver and the crystalline structure of the AgNPs were confirmed by EDX and XRD analyses. Moreover, the possible functional groups of pullulan (oxidized pullulan) responsible for the reduction and stabilization of AgNPs were evaluated using FT-IR. The results showed that both, pullulan and 6-carboxypullulan could be successfully used as reducing as well as capping agents for the AgNPs synthesis which shows potential antimicrobial activity against Gram positive and Gram negative bacteria.

Removal of reactive dye brilliant red HE-3B from aqueous solutions by hydrolyzed polyacrylonitrile fibres: equilibrium and kinetics modelling

A cheap and efficient fibrous hydrolyzed polyacrylonitrile (HPAN) sorbent was obtained by alkaline hydrolysis of Romanian polyacrylonitrile fibres. Scanning electronic microscopy and infrared spectroscopy were used to characterize the hydrolyzed product and to confirm its functionalization. The adsorptive potential of the proposed sorbent for reactive dye Brilliant Red HE-3B removal from aqueous solutions of pH=2 was examined by the batch technique as a function of dye concentration, temperature solution and contact time. The Freundlich, Langmuir and Dubinin-Radushkevich adsorption models were applied to describe equilibrium sorption data and to determine the corresponding isotherm constants. The thermodynamic parameters ΔG, ΔH and ΔS were also determined; the values obtained show that sorption of reactive dye on HPAN fibres is a spontaneous, endothermic and entropy-driven process. The kinetics of sorption of the reactive dye were analyzed using pseudo-first order and pseudo-second order kinetic models. The kinetic data fitted well to pseudo-second order kinetics, indicating the chemisorption of reactive dye onto the fibrous sorbent. The sorption mechanism of the dye onto hydrolyzed fibres was confirmed by FTIR spectroscopy. The dye-loaded HPAN sorbent can be regenerated by treatment with 0.1M NaOH and the regenerated sorbent may be reused in several adsorption-desorption cycles. The results of this study provided evidence that the HPAN fibres are effective for removing reactive dye Brilliant Red HE-3B from aqueous effluents.

Biosorption of reactive dye from aqueous media using Saccharomyces cerevisiae biomass. Equilibrium and kinetic study

AbstractThe biosorption Brilliant Red HE-3B reactive dye by nonliving biomass, Saccharomyces cerevisiae, in batch procedure was investigated. Equilibrium experimental data were analyzed using Freundlich, Langmuir and Dubinin — Radushkevich isotherm models and obtained capacity about 104.167 mg g−1 at 20°C. The batch biosorption process followed the pseudo-second order kinetic model. The multi-linearity of the Weber-Morris plot suggests the presence of two main steps influencing the biosorption process: the intraparticle diffusion (pore diffusion), and the external mass transfer (film diffusion). The results obtained in batch experiments revealed that the biosorption of reactive dye by biomass is an endothermic physical-chemical process occurring mainly by electrostatic interaction between the positive charged surface of the biomass and the anionic dye molecules. The biosorption mechanism was confirmed by FT-IR spectroscopy and microscopy analysis

Equilibrium, kinetic, and thermodynamic studies of Basic Blue 9 dye sorption on agro-industrial lignocellulosic materials

AbstractThe sorptive potential of some lignocellulosic agro-industrial wastes (sunflower seed shells and corn cob) for Basic Blue 9 cationic dye removal from aqueous solutions was examined using the batch technique. The Freundlich, Langmuir, and Dubinin-Radushkevich isotherm models were used in order to determine the quantitative parameters of sorption. The Langmuir isotherm model indicated a maximum sorption capacity for these materials in the range of 40–50 mg dye per g (25°C), slightly higher for corn cob than for sunflower seed shells. The values of the thermodynamic parameters showed that the retention of cationic dye is a spontaneous and endothermic process. The application of pseudo-first order and pseudo-second order intraparticle diffusion models, and a Boyd — Reichenberg model for kinetic data interpretation suggested that sorption of Basic Blue 9 dye onto the studied materials is a process where both surface sorption and intraparticle diffusion contributed to the rate-limiting step. These lignocellulosic wastes can be used with good efficiency for dye removal from aqueous effluents.

Sorption of Brilliant Red HE-3B Reactive Dye from Aqueous Solution onto Seashells Waste: Equilibrium and Kinetic Studies

The potential of waste seashells powder, as a new adsorbent for Brilliant Red HE-3B reactive dye removal from aqueous solutions, was examined by the batch technique. The Freundlich, Langmuir, and Dubinin-Radushkevich adsorption models were applied to describe the equilibrium sorption data and to determine the corresponding isotherm constants. The values of the thermodynamic parameters, ΔG, ΔH, and ΔS, indicate that the sorption of reactive dye is a spontaneous and endothermic process. The kinetic data evaluated by pseudo-first order, pseudo-second order, and intraparticle diffusion kinetic models suggested that the sorption of reactive dye onto seashell is a complex process and both surface sorption and intraparticle diffusion contributes to the rate limiting step.

Valorization of food wastes as sorbent for dye retention from aqueous medium

AbstractIn this paper, batch removal of Brilliant Red HE-3B (BRed) and Methylene Blue (MB) dyes onto apple seeds powder was studied in order to evaluate the sorptive properties of this food waste. The experimental data equilibrium was analyzed using the Langmuir, Freundlich, and Dubinin–Radushkevich adsorption models. Results of the study reveal that the Langmuir model best describes the dyes sorption processes. The monolayer sorption capacity was established to be 66.225 mg/g BRed and, respectively, 26.316 mg/g MB at 25°C. The values of the mean free energy obtained from the Dubinin–Radushkevich model indicated a porous structure of the sorbents and suggest that physical sorption is the main sorption type involved in the studied processes. The values of the thermodynamic parameters (ΔG, ΔH, and ΔS) showed that sorption of tested dyes was feasible, spontaneous, and endothermic under examined conditions. The Fourier transforms infrared spectroscopy has been used to investigate the interaction between apple...

Removal of Astrazone Blue from aqueous solutions onto brown peat. Equilibrium and kinetics studies

The aim of this study is to characterize and assess the sorption potential of brown peat, in relation to colored pollutants from the textile industry wastewater. The objectives of this paper were: the physicochemical, morphological, and mineralogical characterization of brown peat, testing the adsorption capacity of natural and chemically treated peat samples for Astrazone Blue, evaluation of adsorption process from equilibrium isotherm and kinetic point of view. The characteristics of the peat samples were investigated using elemental analysis, scanning electron microscopy and X-ray diffractometry. Experimental data indicated that the brown peat tested confirm a high level of adsorption (removal efficiency >93.00%, adsorption capacity reaching up to 24.27 mg/g) of Astrazone Blue from aqueous solution. The Langmuir and Freundlich adsorption isotherm models were used to find the best equation able to describe the adsorption process. Experimental adsorption data were successfully described by the Langmuir equilibrium isotherm model. This fact is supported by the agreement between the q values obtained using the Langmuir equation (26.32 mg/g), and the ones obtained experimentally (24.27 mg/g). The kinetic studies showed that the pseudo-second-order model described Astrazone Blue sorption kinetics, as confirmed by the high values of R2, which are over 0.99 for the whole investigated concentration range (200 to 800 mg/L). The use of brown peat adsorbent is more advantageous compared with other materials since it does not require a preliminary treatment, is low-cost and is an eco-friendly adsorbent. Hence, this peat appears to be a viable material for the decontamination of effluents containing dyes.

Kinetics studies on the adsorption behaviour of Basic Blue 9 dye on macroporous ion exchanger resins

AbstractAmong various types of adsorbents used in the treatment of wastewaters impurified with dyes, the ion exchange resins still have an important place. The aims of this paper are: to evaluate the influence of contact time on the dye adsorption from aqueous solutions on Purolite macroporous ion exchange resins for strong acid (C-145) and for weak acid (C-107E), to understand the mechanisms that govern dye removal and to find an appropriate kinetic model to describe the process. In order to investigate the mechanism of adsorption and the potential rate controlling steps, pseuso-first- and second-order equations, the intraparticle diffusion equation and the Elovich equation have been used to test experimental data. The kinetics of the adsorption process of Basic Blue 9 dye onto Purolite ion exchanges follows a pseudo-second- order rather than pseudo-first- order model, and both the film and the intraparticle diffusion mechanisms are involved in the adsorption processes, and may be the rate determining st...