Danijela V. Bojić

Removal of Cu2+ and Zn2+ from model wastewaters by spontaneous reduction-coagulation process in flow conditions.

The treatment of model wastewaters containing heavy metals by spontaneous reduction-coagulation process using micro-alloyed aluminium composite (MAlC) in a laboratory semi-flow system (SFS) has been investigated. Several working parameters, such as treatment time, pH, initial metal concentration and flow rate were studied in an attempt to achieve a higher removal capacity. The residual concentrations of metals were at admissible levels after only 20 min of treatment. Removal rate of Zn(2+) was greater at neutral pH than at acid or basic, while Cu(2+) removal was less affected by pH. Removal constants of both metals decreased as initial metal concentration increased from 20 to 200 mg L(-1). In mixed wastewaters the presence of copper caused increase of Zn(2+) removal efficacy, however, the copper removal was not affected by zinc. The removal mechanisms depend on metals nature and pH: copper was mainly removed by reduction, while zinc by precipitation as hydroxide. The kinetic of process was mass-transport limited, thus increasing of flow rate accelerated removal of metals. The method was found to be highly efficient and faster compared to conventional treatments.

Comparison of new biosorbents based on chemically modified Lagenaria vulgaris shell

AbstractSorption characteristics of three Lagenaria vulgaris-based biosorbents: raw biomass (rLVB), acid–base-activated biomass (aLVB) and sulfuric acid-treated biomass (ccLVB), were compared as a function of contact time, initial methylene blue concentration, and initial pH, in order to evaluate the effect of chemical modifications. The adsorption studies of raw and chemically modified L. vulgaris biomass were compared in batch mode. The Fourier transform Infrared spectroscopy (FTIR) results of biosorbents’ characterization showed presence of different functional groups which can be responsible for sorption of MB from aqueous solutions. Moreover, FTIR analysis reveals that acid–base activation of raw biomaterial resulted in hydrolysis of esters providing more reactive sites (–COO−), while sulfuric acid-treatment method introduced new functional groups such as –SO3−. Surface functional groups containing oxygen, such as carboxylic, lactonic, and phenolic, are quantified using the Boehm’s method. The kineti...

Biosorption of copper(II) ions by methyl-sulfonated Lagenaria vulgaris shell: kinetic, thermodynamic and desorption studies

The biosorption of Cu(II) ions on chemically modified Lagenaria vulgaris shell was investigated as a function of temperature at different initial metal ion concentrations. Also, the effects of particle size and agitation rate on the adsorption yield were studied. Efficiency of biosorbent based on chemically modified Lagenaria vulgaris shell for Cu(II) ion removal from aqueous solution was studied in batch conditions. The thermodynamic parameters of copper biosorption indicated that the process was spontaneous and exothermic. Kinetic models applied to the sorption data at various particle sizes showed that the Cu(II) ion uptake process followed the pseudo-second order rate model and the adsorption rate constants decreased with increasing dimension of particles. Desorption studies revealed that the studied biosorbent can be regenerated using 0.1 M HNO3 and reused. The results indicate that the chemically modified Lagenaria vulgaris shell can be used as a promising alternative for the adsorption of Cu(II) ions from aqueous solution.

Equilibrium and kinetic studies of Pb(II), Cd(II) and Zn(II) sorption by Lagenaria vulgaris shell

The sorption of lead, cadmium and zinc ions from aqueous solution by Lagenaria vulgaris shell biosorbent (LVB) in batch system was investigated. The effect of relevant parameters such as contact time, biosorbent dosage and initial metal ions concentration was evaluated. The Pb(II), Cd(II) and Zn(II) sorption equilibrium (when 98% of initial metal ions were sorbed) was attained within 15, 20 and 25 min, respectively. The pseudo first, pseudo-second order, Chrastil’s and intra-particle diffusion models were used to describe the kinetic data. The experimental data fitted the pseudo-second order kinetic model and intra-particle diffusion model. Removal efficiency of lead(II), cadmium(II) and zinc(II) ions rapidly increased with increasing biosorbent dose from 0.5 to 8.0 g dm-3. Optimal biosorbent dose was set to 4.0 g dm-3. An increase in the initial metal concentration increases the sorption capacity. The sorption data of investigated metal ions are fitted to Langmuir, Freundlich and Temkin isotherm models. Langmuir model best fitted the equilibrium data (r2 > 0.99). Maximal sorption capacities of LVB for Pb(II), Cd(II) and Zn(II) at 25.0±0.5°C were 0.130, 0.103 and 0.098 mM g-1, respectively. The desorption experiments showed that the LVB could be reused for six cycles with a minimum loss of the initial sorption capacity.

Identification of intermediates and ecotoxicity assessment during the UV/H2O2 oxidation of azo dye Reactive Orange 16

Degradation of azo dye Reactive Orange 16, a widely used textile dye, was carried out with UV light in the presence of H2O2. The experiments were conducted in the batch mode using low-pressure mercury lamps, emitting at 253.7 nm. Liquid-chromatography tandem mass spectrometry (LC/MS/MS) and high resolution mass spectrometry (FT-ICR) were employed in order to identify some of degradation products as well as to suggest possible degradation pathways. According to the mass spectrum characterization of RO16 dye and MSn fragmentation (up to MS4), its possible fragmentation pattern was proposed. The results revealed that degradation occurred mainly via hydroxylation, cleavage of the C‒S bond between the aromatic ring and the sulfonate group, cleavage of the azo bond, cleavage of the C‒N bond between azo group and naphthalene ring and aromatic ring opening. Toxicity test with marine photobacterium Vibrio Fisheri was performed to consider whether or not the UV/H2O2 treatment of RO16 dye results in the products with enhanced toxicity for aquatic life.

Chemically Modified Lagenaria vulgaris as a Biosorbent for the Removal of CuII from Water

The ability of a biosorbent based on a chemically modified Lagenaria vulgaris shell for CuII ion removal from aqueous solution was studied in batch conditions. The biosorbent was characterized by Fourier-transform infrared spectroscopy and the effect of relevant parameters such as contact time, pH, biomass dosage, and initial metal ion concentration was evaluated. The sorption process was found to be fast, attaining equilibrium within 40 min, and results were found to be best fitted by a pseudo-second order kinetic model. Experimental data showed that the biosorption is highly pH dependent, and the optimal pH was 5.0. Results were analyzed in terms of the following adsorption isotherms: Langmuir, Freundlich, Temkin, and Flory–Huggins, by a linear regression method. The CuII biosorption followed the Langmuir isotherm model (r2 = 0.998) with the maximum sorption capacity of 14.95 mg g–1. The methyl-sulfonated Lagenaria vulgaris biomass investigated in this study exhibited a high potential for the removal of CuII from aqueous solution.

Synthesis of mesoporous triple-metal nanosorbent from layered double hydroxide as an efficient new sorbent for removal of dye from water and wastewater

In this study, co-precipitation synthesis of the mesoporous triple-metal nanosorbent from Fe, Cu, Ni layered double hydroxide (FeCuNi-LDH), on the basis of the data obtained from the TG analysis was carried out. The FTIR spectroscopy and XRD results confirm the formation of CuO, NiO and Fe2O3 nanoparticles, while the EDX analysis does not show significant variations on the surface in elemental composition. BET analysis shows that FeCuNi-280 (FeCuNi-LDH calcinated at 280 °C) with mesoporous structure, has larger surface area compared to FeCuNi-LDH and FeCuNi-550 (FeCuNi-LDH calcinated at 550 °C). The value of pHPZC of FeCuNi-280 is found to be 8.66. Obtained FeCuNi-280 material showed the ability for efficient removal of dye Reactive Blue 19 (RB19) from water, with a very high sorption capacity of 480.79 mg/g at optimal conditions: the sorbent dose of 0.6 g/dm3, stirring speed of 280 rpm and pH 2. The kinetics results of the sorption process were well fitted by pseudo-second order and Chrastil model, and the sorption isotherm was well described by Sips, Langmuir and Brouers-Sotolongo model. FeCuNi-280 was easily regenerated with aqueous solution of NaOH, and reutilization was successfully done in five sorption cycles. The present study show that easy-to-prepare, relatively inexpensive nanosorbent FeCuNi-280 is among the best sorbents for the removal of RB19 dye from water solution and wastewater from textile industry in wide range of pH.

Effects of operational parameters of process UV radiation/hydrogen peroxide on decolorization of anthraquinone textile dye

The photodegradation of textile dye Reactive Blue 19, an anionic anthraquinone dye of reactive class, was investigated using UV radiation in the presence of H2O2 in UV reactor with low-pressure mercury lamps, with maximum energy output at the wavelength 254 nm. The effects of experimental variables, namely initial pH, initial dye concentration and concentration of peroxide were studied. The change of concentration of RB19 was followed by UV/vis spectrophotometric measurement of absorbance at 592 nm. The increase of the initial pH resulted in the efficiency increase of dye decolorization. The total decolorization was achieved in about 15 min. Results show that with the increase of dye concentration from 10 to 100 mg dm-3 the efficiency of process decreases. With the increase of the initial concentration of H2O2 from 10 to 30 mmol dm-3, the decolorization rate constant increased from 0.083 to 0.120 min1, with the decrease of process rate at the concentrations above. The highest decolorization rates were achieved at peroxide concentration of approx. 30 mmol dm-3, above which decolorization was inhibited by scavenging effect of peroxide. This study shows that UV/H2O2 process is promising treatment for dye RB 19 degradation in water and wastewater.