Ivan Andjelkovic

Graphene Aerogels Decorated with α-FeOOH Nanoparticles for Efficient Adsorption of Arsenic from Contaminated Waters

Arsenic (As) is the worlds most hazardous chemical found in drinking water of many countries; therefore, there is an urgent need for the development of low-cost adsorbents for its removal. Here, we report a highly versatile and synthetic route for the preparation of a three-dimensional (3D) graphene-iron oxide nanoparticle aerogel composite for the efficient removal of As from contaminated water. This unique three-dimensional (3D) interconnected network was prepared from natural graphite rocks with a simple reaction, without the use of harsh chemicals, which combines with the exfoliation of graphene oxide (GO) sheets via the reduction of ferrous ion to form a graphene aerogel composite decorated with iron oxide nanoparticles. The prepared adsorbent showed outstanding absorption performance for the removal of As from contaminated water, because of its high surface-to-volume ratio and characteristic pore network in the 3D architecture. The performed case study using real drinking water contaminated with As under batch conditions showed successful removal of arsenic to the concentration recommended by the World Health Organisation (WHO).

Kinetics of Thyroxine (T4) and Triiodothyronine (T3) Transport in the Isolated Rat Heart

The dynamics and kinetics of thyroid hormone transport in the isolated rat heart were examined using the modified unidirectional paired tracer dilution method. The uptake of 125I‐thyroxine (125I‐T4) and 125I‐triiodothyronine (125I‐T3) from the extracellular space into heart cells was measured relative to the extracellular space marker 3H‐mannitol. The thyroid hormone maximal uptake was 54.4% for 125I‐T4 and 52.15% for 125I‐T3. The thyroid hormone net uptake was 25.69% for 125I‐T4 and 25.49% for 125I‐T3. Backflux from the intracellular space was 53.17% for 125I‐T4 and 61.59% for 125I‐T3. In the presence of unlabelled thyroid hormones, 125I‐T4 and 125I‐T3 maximal uptakes were reduced from 10.1 to 59.74% and from 34.6 to 65.3%, respectively, depending on the concentration of the unlabelled hormone, suggesting a saturable mechanism of the thyroid hormone uptake by the heart cells, with Km(T4)= 105.46 μM and the maximal rate of 125I‐thyroid hormone flux from the extracellular space to heart cells (Vmax(T4)) = 177.84 nM min−1 for 125I‐T4 uptake, and Km(T3)= 80.0 μM and Vmax(T3)= 118.5 nM min−1 for 125I‐T3 uptake.

Protective effects of glucagon during the anaphylactic response in guinea-pig isolated heart

1 Cardiac anaphylaxis and the effects of glucagon pretreatment were studied in guinea‐pig isolated hearts actively sensitized to ovalbumin. 2 Antigen challenge of the sensitized hearts markedly increased creatine Phosphokinase (CPK) activity in the coronary venous effluent. Control values of CPK release from the hearts before challenge were 3.56 ± 0.15 mu min−1 mg−1. In the first 10 min following challenge, CPK release remained stable at increased levels which ranged between 4.88 ± 0.20 to 5.39 ± 0.38 mu min−1 mg−1. There was no correlation between immunologically released histamine and CPK release. 3 Pretreatment of the hearts with glucagon (0.15 μmol l−1) exerted a pronounced anti‐arrhythmic activity, reducing the conduction arrhythmias and completely preventing automaticity arrhythmias which normally occurred following ovalbumin challenge. 4 Anaphylactic histamine release was reduced significantly in the presence of glucagon. The percentage inhibition of histamine release from glucagon pretreated hearts, during the first 10 min after challenge, ranged between 58% and 94% of that from hearts similarly challenged in the absence of glucagon. 5 Glucagon significantly elevated sinoatrial nodal automaticity, enhanced atrioventricular conduction, improved coronary flow and reduced contractile force during anaphylaxis. It appears that these effects are caused both by modulating anaphylactic histamine release and by influencing the effects of the released histamine. 6 CPK release from the anaphylactic hearts was significantly inhibited in the presence of glucagon. The average percentage inhibition of CPK activity during the first 10 min after challenge ranged between 42% and 98%. 7 The findings from this study provide experimental evidence for protective effects of glucagon pretreatment during cardiac anaphylaxis.

Microwave-hydrothermal method for the synthesis of composite materials for removal of arsenic from water

Composite material Zr-doped TiO2, suitable for the removal of arsenic from water, was synthetized with fast and simple microwave-hydrothermal method. Obtained material, Zr-TiO2, had uniform size and composition with zirconium ions incorporated into crystal structure of titanium dioxide. Synthetized composite material had large specific surface area and well-developed micropore and mesopore structure that was responsible for fast adsorption of As(III) and As(V) from water. The influence of pH on the adsorption capacity of arsenic was studied. The kinetics and isotherm experiments were also performed. The treatment of natural water sample containing high concentration of arsenic with composite material Zr-TiO2 was efficient. The concentration of arsenic was reduced to the value recommended by WHO.

Bacterial iron-oxide nanowires from biofilm waste as a new adsorbent for the removal of arsenic from water

Biofilm, generated by the bacteria in the groundwater pumping system pipelines of the Salt Interception Scheme on the River Murray in South Australia is discarded as a waste material accumulated after periodic cleaning of the pipes. Structural and chemical composition characterizations confirm that this waste material is composed of amorphous twisted iron-oxide nanowires (ION), generated by bacteria, and they have a unique structure and properties. The adsorption performance of these iron-oxide nanowires for arsenic removal from water was evaluated to define their adsorption capacity for As(III) and As(V) and kinetics. Obtained results demonstrate considerable adsorption properties of this waste biological material and suggest its promising application as a new and low-cost adsorbent for water treatment.

The ultrasound assisted extraction of matrix elements and heavy metal fractions associated with Fe, Al and Mn oxyhydroxides from soil

Single agent extractions of major and trace metals from soil samples were conducted by means of a rotary mixer and an ultrasonic bath with soni- cation times of 10, 20, 30, 40 and 50 min. The sequential extraction was under- taken according to the European Community Bureau of Reference. The ob- tained soil extracts were analyzed by inductively coupled plasma-optical emis- sion spectrometry and according to the results, the rotary mixer-assisted ex- traction was more efficient in the case of alkaline earth elements. However, by use of ultrasound, several times higher amounts of matrix elements (Fe, Al and Mn) and heavy metals predominantly associated with Fe, Al and Mn oxyhyd- roxides were extracted. The increase of the sonication time failed to improve the extraction yields. The changes in the conductivity, pH, redox potential, par- ticle size diameter and zeta potential of colloid particles with increasing soni- cation time were measured. The extraction mechanism and expressed selecti- vity of ultrasound is discussed and an explanation is suggested.