Biosorptive removal of Pb2+, Cd2+ and Zn2+ ions from water by agenaria vulgaris shell

Lagenaria vulgaris (LV) shell was used as a biosorbent for the removal of heavy metal ions, Pb2+, Cd2+ and Zn2+, from aqueous solutions. Experiments were carried out under batch conditions. The effects of contact time, initial pH, temperature and stirring speed on removal efficiency are presented. Sorption of the investigated metals was fast, reaching equilibrium after about 5 to 10 min, depending on the metal. Biosorption was highly pH-dependent, and the optimal pH for investigated metals was in the range of 4.5 to 6.0. The effects of temperature demonstrated that biosorption of the metals is a chemical process. SEM analysis revealed interesting morphological changes after acid refinement of the raw biosorbent and metal uptake that is related to the chemical nature of the biosorption process. EDX analysis of Lagenaria vulgaris biosorbent(LVB) before and after metal sorption revealed that the ion exchange mechanism was the principal sorption process. Fourier transform infrared spectroscopy (FTIR) analysis has shown that major functional groups (carboxyl and hydroxyl) on the biosorbent surface took part in the metal ion uptake process as active sites. The results obtained showed that Lagenaria vulgaris based biosorbent could be used as an effective and low-cost pre-treatment step for removal of toxic metals from wastewaters

Modelling of hydrochemical and hydromechanical parameters' synergism in the process of solid deposit creation in geothermal and other hard waters

© 2018 Serbian Chemical Society. All rights reserved. This paper presents the experimental research results, regarding the effect of hydromechanical parameters and based on the relative reduction of the starting hardness of geothermal water of Sijarinska Banja and Niška Banja as well as the water from the Medijana spring in Niš.The measurements were conducted on a laboratory pilot plant/facility with glass pipes of diameter 2, 4, 6, 8 and 10 mm and with water flow controlled by a digital peristaltic pump with a flow interval from 2 to 5000 ml min-1.The effect of the hydrodynamic parameters on the change of input hardness of geothermal and other hard waters and the process of solid deposit creation were modelled by an empirical model based on simple linear regression analysis, multiple linear regression model and the neural network.The high accuracy of all applied models unequivocally proves that a synergism of hydrochemical and hydrodynamic parameters exists in the process of creation of solid deposit - limescale, thanks to which the starting hypothesis is confirmed

The influence of multifunctional microalloyed ceramics microstructure on its capacity properties

© 2018, University of Kragujevac, Faculty of Science. Modified porous alumo-silicate ceramics, alloyed with magnesium and microalloyed with aluminum, belongs to modern multifunctional ceramic materials. Microalloying has led to important changes in dielectric and electrical properties of ceramics, such as dielectric constant and electrical resistance. These changes are conditioned by the microstructural properties of modified porous ceramics. The obtained results have shown the unity of the influence of composition, structure, morphology and application of microalloyed multifunctional alumosilicate ceramics on electrophysical properties. Microstructural investigations have shown that this type of ceramics has an amorphous-crystal structure, which causes important changes in its electrical properties and affects its activity. Therefore the ceramics can be considered as an active dielectric. A correlation between microstructural properties and structurally sensitive, i.e. electrophysical properties of microalloyed multifunctional alumo-silicate ceramics, was confirmed

Physicochemically modified peat by thermal and oxidation processes as an active material for purification of wastewaters from certain hazardous pollutants

© 2017, Association of Chemists and Chemical Engineers of Serbia. All rights reserved. The physicochemical modification of peat through thermal and oxidation processes was carried out, in order to obtain new, inexpensive and active material for purification of different types of waters. During the modification, surface chemical compounds of Shilov type were formed. Batch adsorption properties and suitability of physicochemically modified peat (PCMP) for odor removal were tested in aqueous solutions of H2S and colloidal sulphur. Additionally, PCMP was tested in the removal of As(V) which is hazardous ingredient in contaminated waters. Possible mechanisms of pollutants binding include interactions, which lead to formation of adducts and clathrates. All these processes are elucidated in detail. The results showed that the obtained material can be used for the removal of sulphide, colloidal sulphur and As(V) from different types of waters

Removal of chromium (VI) from water by micro-alloyed aluminium composite (MAlC) under flow conditions

This paper deals with Cr(VI) ion removal from water, by micro-alloyed aluminium composite (MAlC), under flow conditions. In a water environment the MAlC acts as a strong reducing agent. Dissolving it in water is accompanied by the generation of Al(III) ions and reduction of water to H2, with OH- ions. The final product is insoluble Al(OH) 3. A series of Cr(VI) model solutions, with initial pH ranging between 1 and 5, were treated in the original semi-flow system (SFS), which simulated flow conditions well. The results demonstrate a high MAlC efficacy, considering that at the end of the treatment, concentrations of Cr(VI) were below the maximal allowed concentrations for drinking water, in all model solutions. The MAlC mechanism of action is based mainly on processes of reduction and co-precipitation by Al(OH) 3, because Cr(VI) is removed from the water phase as metal chromium and insoluble Cr(OH) 3. Behaviour of the composite in water is under significant influence of pH, which affects its efficacy and mechanism of action. Therefore, the rate of Cr(VI) removal is greater at the beginning, decreasing towards the end of the treatment. Additionally, the ratio of [metal chromium]/[Cr(OH) 3] in precipitate, at the end of the treatment, decreases with increasing initial pH of the model solution. Application of the SFS significantly enlarges efficacy of the MAlC, compared to work under stationary conditions. WaterSA Vol.30 (3) 2004: 353-35