Aleksandar Lj. 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.

A direct potentiometric titration study of the dissociation of humic acid with selectively blocked functional groups

A direct potentiometric titration method was applied to commercial and soil humic acids in order to determine their carboxyl and phenol group concentrations and apparent and intrinsic pK. In that context, acid-base properties of humic acids are interpreted by selective blocking of carboxylic and phenolic groups by esterification and acetylation. Differences in underivatized and derivatized HAs acid-base properties are ascribed to carboxyl and phenol groups influence on total humic acidity. Potentiometric data were treated with the modified Henderson-Hasselbalch equation. Infra red results, the acidic group contents and the average values of apparent and intrinsic pK for underivatized and derivatized HAs confirmed the selectivity of esterification derivatization method. After blocking of the functional groups, the values of acidic group contents decreased, while the value of apparent pK increased after derivatization. Phenol groups cannot be specifically identified by the acetylation method, due to low selectivity of the acetylation method.

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.

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.

Significance of the structural properties of CaO catalyst in the production of biodiesel: An effect on the reduction of greenhouse gases emission

The influence of the physicochemical properties of a series of CaO catalysts activated at different temperatures on the biodiesel production was investigated. These catalysts show dissimilar yields in the transesterification of triglycerides with methanol. We have found significant relationships between structural properties (the type of the pore system, the typical CaO crystal phase and the sizes of crystallites (up to 25 nm), the minimal weight percentage of CaO phase, the total surface basicity and potential existence of two types of basic active sites) of CaO prepared and activated by means of thermal treatment at highest temperature and catalytic efficiency. Benefits of this catalyst are short contact time, standard operating temperature and atmospheric conditions, relatively low molar ratios and small catalyst loading. These all together resulted in a very high biodiesel yield of high purity. The properties of different biodiesel (obtained with the use of the prepared CaO catalyst) blends with different diesel and biodiesel ratios indicate that the higher the fraction of biodiesel fuel the better the achieved fuel properties according to the EU standards. A significant reduction of CO2 and CO emissions and only a negligible NOx increase occurred when blends with an increased biodiesel portion was used. The use of biodiesel derived blends, and the eventual complete replacement of fossil fuels with biodiesel as a renewable, alternative fuel for diesel engines, would greatly contribute to the reduction of greenhouse gases emissions. [Projekat Ministarstva nauke Republike Srbije, br. ON 172061 i TR 34008]

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.

The acid–base, morphological and structural properties of new biosorbent obtained by oxidative hydrothermal treatment of peat

Samples of natural peat (NP) were hydrothermally treated at different temperatures in oxidative and acidic aqueous medium to tailor their acid–base, adsorption, morphological and other properties. The obtained materials were thoroughly characterized by SEM, XRD and FTIR techniques, followed by determination of pHpzc, examination of adsorption characteristics and the extent of organic matter leaching in water. Acid–base characteristics of these materials were examined by potentiometric and conductometric titration of corresponding aqueous suspensions. Experimental potentiometric data were interpreted using ProtoFit software (NEM, non-electrostatic model) which provided pKa values and concentrations of surface sites which are compared with corresponding values obtained by conductometric titration method. There are two main types of surface groups (carboxylic and phenolic) that are dominant in the materials and determine their acid–base behavior in the aqueous medium. Temperature during oxidative hydrothermal treatment has no significant effect on the total number of surface groups, but influences the ratio of carboxylic and phenol-type groups. Hence, acid–base properties of peat can be tailored, which is useful in designing and improving adsorptive characteristics of peat for the preferential removal of certain pollutants from water.

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.

Synthesis and Physicochemical Characterization of Anion Exchanger Based on Green Modified Bottle Gourd Shell

The structural performance and biosorption behavior of a new cationic biosorbent (CALV) prepared from bottle gourd (Lagenaria vulgaris) shell (LVS) as a potentially valuable agrowaste have been established. The biosorbent with anion exchangeable function was synthesized from a modified lignocellulosic biomass (MLV) by a quaternary ammonium agent, N-(3-chloro-2-hydroxypropyl)trimethylammonium chloride. Preparation of the appropriate MLV precursor was firstly carried out by the process of alkaline pretreatment of LVS biomass using a green carbonate solution. In this way, partial delignification, removal of extractive substances, and increased porosity of the cellulose-enriched MLV biomass, as well as the activation of available cellulosic microfibrils to alkaline-cellulose have been achieved. The optimization of synthesis conditions was carried out by direct estimation of the CALV biosorption efficiency to phosphate (using ICP-OES) and nitrate (using UV-VIS) from the aqueous solutions. The structural changes of MLV precursors during green modification and the success of synthesis and biosorbent performances before and after the removal of anions from contaminated solutions have been registered and clarified by physicochemical methods, which include elemental analysis, chemical constitution, morphological characterization, and FTIR spectroscopy. In accordance with the FTIR spectroscopic analysis and isotherm studies, a structural model of the CALV biosorbent and its ion exchange mechanism are proposed.