Voltammetric determination of lutetium

Half wave potential of lutetium was determined by anodic stripping voltammetry using various electrolyte solutions at the mercury electrode. The influence of electrolyte pH on the value of peak current was also observed. The results show that the choice of the supporting electrolyte and the electrolyte pH strongly influence the voltammetric behaviour of lutetium.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Determination of copper and nickel by ion chromatography and voltammetry

Simultaneous determination of copper(II) and nickel(II) by ion chromatography (IC) has been optimized and the detection limits of the new method were compared to stripping voltammetry. The best eluent enabling fast end efficient separation of Cu(II) and Ni(II) is a mixture of 8 mM citric and 0.3 mM oxalic acid using a Metrosep C2 (Metrohm) IC column. The detection limits are significantly lower using stripping voltammetry, while IC is considerably faster.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Adsorpcione karakteristike hidrogelova hitozana za uklanjanje boje kongo crveno iz vodenih rastvora

The present study investigated potential application of biopolymer chitosan, in the form of gel beads, for the removal of Congo red (CR) dye from aqueous solution. Chitosan hydrogel beads (CHBs) were prepared by a coupled ionic and covalent co-cross-linking, employing citric acid (CA) and glutaraldehyde (Glu) as an ionic and a chemical crosslinker, respectively. Batch experiments were carried out to optimize the process conditions for efficient removal of CR dye and to determine the adsorption capacity of prepared CHBs. The results showed that the highest removal efficiency of CR was obtained in the pH range from 6 to 10, and that the equilibrium was attained after 180 min. The Langmuir isotherm model provided the best correlation for the adsorption of CR onto CA/Glu cocross-linked CHBs, with the maximum adsorption capacity (qm) of 544.2 mg g-1 .Istraživanja u okviru ove studije okrenuta su ka ispitivanju mogućnosti primene hidrogelova hitozana, u obliku sfera, za uklanjanje boje kongo crveno (CR) iz vodenih rastvora. Sfere hidrogela hitozana (CHBs) pripremljene su spregnutim jonskim i kovalentnim umrežavanjem, pri čemu su limunska kiselina (CA) i glutaraldehid (Glu) korišćeni kao jonski i kovalentni umreživač, respektivno. Eksperimenti su rađeni u šaržnom sistemu kako bi se optimizovali uslovi za efikasno uklanjanje CR iz vode i odredili adsorpcioni kapaciteti sintetisanih CHBs. Eksperimentalni rezultati su pokazali da je efikasnost uklanjanja CR najveća u pH intervalu od 6 do 10, a da se ravnoteža uspostavlja nakon 180 minuta. Langmirova izoterma pokazala je najbolju korelaciju za adsorpciju CR boje na CA/Glu umreženim sferama hidrogelova hitozana, pri čemu maksimalni adsorpcioni kapacitet (qm) iznosi 544.2 mg g-1 .59th Meeting of the Serbian Chemical Society; June 1-2, 2023, Novi Sad, Serbi

Application of raw and modified clay for the removal of heavy metals from aqueous solutions

This work represents a fundamental study of the simultaneous sorption of heavy metals from aqueous solutions by locally available raw and mechanochemically activated natural clay. The obtained results show that the investigated clay, as an economical and efficient sorbent, has potential for application in the treatment of heavy-metal-contaminated wastewaters

Selective Adsorption of Ionic Species Using Macroporous Monodispersed Polyethylene Glycol Diacrylate/Acrylic Acid Microgels with Tunable Negative Charge

In this work, the possibility of fabricating composite magneto-optical ceramics by electrophoretic deposition (EPD) of nanopowders and high-temperature vacuum sintering of the compacts was investigated. Holmium oxide was chosen as a magneto-optical material for the study because of its transparency in the mid-IR range. Nanopowders of magneto-optical (Ho0.95La0.05)2O3 (HoLa) material were made by self-propagating high-temperature synthesis. Nanopowders of (Y0.9La0.1)2O3 (YLa) were made by laser synthesis for an inactive matrix. The process of formation of one- and two-layer compacts by EPD of the nanopowders from alcohol suspensions was studied in detail. Acetylacetone was shown to be a good dispersant to obtain alcohol suspensions of the nanopowders, characterized by high zeta potential values (+29–+80 mV), and to carry out a stable EPD process. One-layer compacts were made from the HoLa and YLa nanopowders with a density of 30–43%. It was found out that the introduction of polyvinyl butyral (PVB) into the suspension leads to a decrease in the mass and thickness of the green bodies deposited, but does not significantly affect their density. The possibility of making two-layer (YLa/HoLa) compacts with a thickness of up to 2.6 mm and a density of up to 46% was demonstrated. Sintering such compacts in a vacuum at a temperature of 1750 °C for 10 h leads to the formation of ceramics with a homogeneous boundary between the YLa/HoLa layers and a thickness of the interdiffused ion layer of about 30 μm

Selective Adsorption of Ionic Species Using Macroporous Monodispersed Polyethylene Glycol Diacrylate/Acrylic Acid Microgels with Tunable Negative Charge

Monodispersed polyethylene glycol diacrylate (PEGDA)/acrylic acid (AA) microgels with a tuneable negative charge and macroporous internal structure have been produced using a Lego-inspired droplet microfluidic device. The surface charge of microgels was controlled by changing the content of AA in the monomer mixture from zero (for noncharged PEGDA beads) to 4 wt%. The macroporosity of the polymer matrix was introduced by adding 20 wt% of 600-MW polyethylene glycol (PEG) as a porogen material into the monomer mixture. The porogen was successfully leached out with acetone after UV-crosslinking, which resulted in micron-sized cylindrical pores with crater-like morphology, uniformly arranged on the microgel surface. Negatively charged PEGDA/AA beads showed improved adsorption capacity towards positively charged organic dyes (methylene blue and rhodamine B) compared to neutral PEGDA beads and high repulsion of negatively charged dye molecules (methyl orange and congo red). Macroporous microgels showed better adsorption properties than nonporous beads, with a maximum adsorption capacity towards methylene blue of 45 mg/g for macroporous PEGDA/AA microgels at pH 8.6, as compared to 23 mg/g for nonporous PEGDA/AA microgels at the same pH. More than 98% of Cu(II) ions were removed from 50 ppm solution at pH 6.7 using 2.7 mg/mL of macroporous PEGDA/AA microgel. The adsorption of cationic species was significantly improved when pH was increased from 3 to 9 due to a higher degree of ionization of AA monomeric units in the polymer network. The synthesized copolymer beads can be used in drug delivery to achieve improved loading capacity of positively charged therapeutic agents and in tissue engineering, where a negative charge of scaffolds coupled with porous structure can help to achieve improved permeability of high-molecular-weight metabolites and nutrients, and anti-fouling activity against negatively charged species

Removal of Cu(II) from aqueous solutions using adsorbent based on chitosan hydrogel beads

Mine waters and tailings resulting from mining and mineral processing often have a harmful effect on the local environment. Copper has a strong biocidal activity that greatly affects ecosystems. Therefore, the removal of copper from wastewater is of great importance to the environment. Chitosan, a natural biopolymer, obtained from chitin, the most abundant natural fiber, often has better properties than much more expensive synthetic polymers. This paper investigates the application of chitosan-based sorbents for removing copper from aqueous solutions. A novel adsorbent, chitosan hydrogel beads (CHBs), was synthesized from chitosan flakes (medium molecular weight), via ionic/covalent cross-linking. Batch experiments were carried out to optimize the process conditions for efficient removal of Cu(II) and to determine the adsorption capacity of prepared CHBs. The results showed that the maximum Cu(II) adsorption capacity estimated with Langmuir isotherm modeling was 103.6 mg/g which was three times higher than chitosan flakes (33.7 mg/g).IOC 2023 : 54th International October Conference on Mining and Metallurgy; October 18-21, 2023, Bor Lake, Serbi

Indirect determination of lutetium by differential pulse anodic stripping voltammetry at a hanging mercury drop electrode

Lutetium has been determined by differential pulse anodic stripping voltammetry in an acidic solution containing Zn-EDTA. Lutetium (III) ions liberated zinc (II), which was preconcentrated on a hanging mercury drop electrode and stripped anodically, resulting in peak current linearly dependent on lutetium (III) concentration. Less than 0.4 ng mL(-1) lutetium could be detected after a 2 min deposition

Uklanjanje hroma(VI) iz vode primenom praškastog ugljeničnog materijala dobijenog iz kokosove ljuske kao jeftinog adsorbenta

Most heavy metals, such as Cr (chromium), Pb (lead), Cd (cadmium), Ni (nickel), Cu (copper) and Fe (iron), are extremely toxic above a tolerance limit. These heavy metals in wastewater are not biodegradable and can cause serious harm to human health and ecological environments.1 One of the top-priority toxic heavy metal in wastewater is chromium.2 In natural waters, chromium exists in both trivalent Cr(III) and hexavalent Cr(VI) forms. Cr(VI) is the most toxic one and have the tolerance limit 0.1 mg/L into surface water and 0.05 mg/L in potable water.3 Various methods, such as ion exchange, sedimentation, electrochemical process, cementation, coagulation, adsorption and solvent extraction have been developed for the removal of Cr(VI) and other toxic metals from wastewater.4 Among these methods, in some papers,5-8 adsorption has been used as one of the most effective method for the removal of Cr(VI) from aqueous solutions. Characteristics of adsorption, such as low cost, easy to perform, efficient and reversible method with high operating speed, make this method as most commonly used for the removal of Cr(VI) from aqueous solutions.9 Several adsorbents, like activated alumina,10 zeolites,11 natural bisorbents such as chitosan,12 but also activated carbon13 have been used for the removal of Cr(VI) from aqueous solutions. Due to the high cost, commercial activated carbon is not available in less developed countries and there is a considerable attention to produce activated carbon from less expensive and available materials. As a low-cost adsorbent, activated carbon can be produced from materials such as rice husk, seeds husk, tea leaves, sawdust, oil palm shell, coconut husk and coconut shell.14 Activated carbon is one of the most important adsorbents which is applied in different areas. In these areas it is important to determine and remove low concentrations of some pollutants, such as heavy metals. Very good features of this adsorbent are the main reason why it is used, such as large surface area, porous structure, high adsorption capacity, selective adsorption and low cost. Also, it is important to note that activated carbon has microcrystalline structure with different size and shape of pores, while surface groups plays important role in the adsorption process. Carbon - oxygen surface groups are the most important and they influence the surface characteristics, such as polarity and physicochemical properties of adsorbent. There are two processes for preparation of activated carbon, chemical activation which involves presence of chemical agents, and physical activation, which involves carbonization.15-16 For this research, low-cost powdered activated carbon made from coconut shell was used as adsorbent to remove Cr(VI) from aqueous solutions. Characterization of activated carbon, produced from coconut shell, was accomplished using scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) method. The effects of three 57. savetovanje SHD 137 adsorption parameters, such as solution pH, contact time and initial Cr(VI) concentration, were investigated with respect to the removal efficiency of Cr(VI) from aqueous solutions. Adsorption equilibrium characteristics were analyzed by using the two adsorption models, namely the Langmuir and the Freundlich isotherms.Praškast ugljenični materijal proizveden iz kokosove ljuske korišćen je kao adsorbent za uklanjanje Cr(VI) jona iz vodenih rastvora. Karakterizacija adsorbenta rađena je primenom dve analitičke tehnike, skenirajućom elektronskom mikroskopijom (SEM) i BET metodom. Eksperimenti adsorpcije rađeni su u šaržnom režimu, kako bi se istražili uticaji pH rastvora, vremena kontakta i početne koncentracije Cr(VI) jona. Eksperimentalni rezultati su pokazali da je efikasnost uklanjanja Cr(VI) najveća u pH intervalu od 2,0 do 3,5, a da se ravnoteža uspostavlja nakon 60 minuta. Dva ravnotežna adsorpciona modela, Langmirov i Frojndlihov, korišćena su za fitovanje dobijenih podataka. Frojndlihova izoterma je obezbedila najbolju korelaciju za adsorpciju Cr(VI) jona na ugljeničnom materijalu proizvedenom iz kokosove ljuske. Na osnovu dobijenih rezultata može se zaključiti da ugljenični materijal proizveden iz kokosove ljuske predstavlja jeftin i efikasan adsorbent koji bi potencijalno mogao biti korišćen za tretman otpadnih voda koje sadrže toksični Cr(VI).57th Meeting of the Serbian Chemical Society; June 18-19, Kragujevac, Serbi

Black inorganic pigments obtained from waste materials

Hazardous industrial wastes are the most common source of environmental pollution. Waters originating from unregulated landfills and places of inadequate disposal of this type of wastes can pollute the water sources and affect the human health. In this study, electroplating waste sludge (ES) and various Fe-rich wastes were used as starting materials for the synthesis of inorganic pigments. Obtained black Cr1.3Fe0.7O3 pigments possess adequate properties required for use as inorganic pigments