Gender differentiation in intergenerational care-giving and migration choices

We weave together care-giving, gender, and migration. We hypothesize that daughters who are mothers have a stronger incentive than sons who are fathers to demonstrate to their children the appropriate way of caring for one’s parents. The reason underlying this hypothesis is that women on average live longer than men, they tend to marry men who are older than they are and, thus, they are more likely than men to spend their last years without a spouse. Because it is more effective and less costly to care for parents if they live nearby, daughters with children do not move as far away from the parental home as sons with children or childless offspring. Data on the distance between the children’s location and the parents’ location extracted from the Survey of Health, Ageing and Retirement in Europe (SHARE), in conjunction with data on selected demographic characteristics and institutional indicators taken from Eurostat, the OECD, and the World Bank, lend support to our hypothesis: compared to childless daughters, childless sons, and sons who are fathers, daughters who are mothers choose to live closer to their parents’ home

Chemical Speciation of Chromium in Various Matrices in South African Terrestrial Water Using an Optimised Adsorptive Stripping Voltammetric Procedure

Optimization of analytical procedure for the determination of chromium (III)/(VI) speciation is described. A very sensitive adsorptive-catalytic stripping voltammetry method in the presence of diethylenetriaminepentaacetic acid (DTPA) is used for chromium speciation study in surface and ground water with in very different matrices. The effects of various parameters (pH, ligand concentration, potential, collection time, equilibration time,) on the response are optimized. Concentration ratio of chromium (III)/(VI), and interferences from other metals and anions, typical for South African waters, are considered. Results for total chromium determination are compared with atomic absorption spectrometry (AAS) measurements. South African Journal of Chemistry Vol.54 2001: 264-28

Synthesis of bulk ion-imprinted polymers (IIPs) embedded with oleic acid coated Fe3O4 for selective extraction of hexavalent uranium

A selective and reliable method for the extraction of trace quantities of U(VI) by the use of a magnetic U(VI) ion-imprinted polymer (IIP) was developed. In this study, oleic acid (OA) coated magnetite nano-particles were incorporated into the cross-linked polymeric matrix of the selective sorbent, in order to gain the physical advantages of separating the polymers. Many physico-chemical factors influence the adsorption process; uranyl ion uptake ability based on these parameters was investigated. The optimum parameters obtained were sample pH 4,50 mg of the magnetic polymer, a contact time of 45 min and an initial U(VI) concentration of 2 mg·ℓ-1. The adsorption capacities for the magnetic NIP and IIP were found to be 0.95 mg·g1 and 1.21 mg·g-1, respectively. The adsorption behaviour of U(VI) in the presence of other competing metal ions onto the cross-linked magnetic polymers was also examined in binary mixtures and the order of selectivity was found to be U(VI) > Pb(VI) > Ni(II). The resulting magnetic nano-composite polymers were found to be stable up to the sixth cycle of use and reuse. The Freundlich adsorption model was used for the mathematical description of the adsorption equilibrium and the adsorption kinetic data fitted the pseudo-first-order model with R2 > 0.92.Keywords: Bulk, magnetic imprinted polymers, oleic acid, uraniu

Determination of naproxen, ibuprofen and triclosan in wastewater using the polar organic chemical integrative sampler (POCIS): A laboratory calibration and field application

In this study, the occurrence in wastewater of two non-steroidal  anti-inflammatory drugs (NSAIDs), naproxen and ibuprofen, and one  personal care product, triclosan, was assessed using the polar organic  chemical integrative sampler (POCIS). The samplers were initially  calibrated in the laboratory to obtain sampling rates (Rs) for each target compound followed by deployment in the influent and effluent of  Goudkoppies and Northern Wastewater Treatment Plants (WWTPs), South Africa. Exposure was done for 14 days in 2012. High performance liquid chromatography (HPLC) system with ultraviolet (UV) and fluorescence (FLD) detectors was used to analyse POCIS extracts. Laboratory calibration of POCIS yielded Rs values for the three compounds that were between 0.087 and 0.383l.d-1 in quiescent conditions, and 0.125 and 0.936 l.d-1 in  stirred conditions. From the accumulated amounts in field-deployed  samplers, estimated freely dissolved concentrations of the studied compounds in wastewater influent ranged from 55.0 to 78.4 µg.l-1 and 52.3 to 127.7 µgl.-1 in Goudkoppies and Northern WWTPs, respectively. Average concentrations of these compounds in the treated effluent ranged from 10.7 to 13.5 µgl.-1 in Goudkoppies WWTP, and 20.4 to 24.6 µgl.-1 in Northern WWTP. Analyte removal efficiencies varied between 68 and 86% in Goudkoppies WWTP and 61 and 82% in Northern WWTP. Grab samples processed by SPE method yielded higher analyte concentrations (up to three-fold) as compared to POCIS-derived estimates. This  discrepancy was attributed to SPE's ability to extract both the free  dissolved, and particle sorbed fractions of the contaminants.Keywords: Polar organic chemical integrative sampler, pharmaceuticals and personal care products, wastewater, wastewater treatment plant

Column adsorption studies for the removal of U by phosphonated cross-linked polyethylenimine: modelling and optimization.

A continuous fixed-bed adsorption study was carried out by using phosphonated cross-linked polyethylenimine as an adsorbent for the removal of uranium (U) from aqueous solutions. The effect of inlet metal ion concentration (40, 70, and 100 mg L-1), feed flow rate (1, 2, and 3 mL min(-1)), and polymer bed height (2.5, 3.2 and 4.5 cm) on the breakthrough characteristics of the fixed-bed adsorption system at pH 2 were studied. The results showed that the breakthrough time appeared to increase with increase of bed height but decreased with increase of both influent U concentration and flow rate. Modelling of the dynamics of the fixed-bed adsorption process was studied and the application of different models to describe the breakthrough curves showed that the Thomas and Yoon-Nelson model gave better results for the operating conditions.SP201

Selective adsorption of uranium (VI) on NaHCO3 leached composite γ-methacryloxypropyltrimethoxysilane coated magnetic ion-imprinted polymers prepared by precipitation polymerization

Ion imprinted nano-magnetic composite polymers for selective removal of hexavalent uranium were prepared by a precipitation polymerization technique in the presence of γ-methacryloxypropyltrimethoxysilane (γ-MPS) coated magnetite and other pre-polymerization reagents. The synthesized magnetic polymers were then leached with NaHCO3 to produce magnetic ion imprinted polymers (IIPs) with fabricated adsorption sites complementary to the uranyl ions in terms of size and shape. Several parameters were investigated to obtain conditions which gave the optimum adsorption of the uranyl onto the magnetic IIPs and their corresponding controls, magnetic ion non-imprinted polymers (NIPs). The optimum amount of magnetic sorbent, initial concentration and contact time were 50 mg, 2.5 mg L-1 and 45 min, respectively. The adsorption capacity of the magnetic IIP (1.15 ± 0.01 mg g-1) was higher than that of the magnetic NIP (0.93 ± 0.02 mg g-1). This indicated that the former had a somewhat higher affinity for U(VI) than the later. The magnetic polymers also displayed good selectivity of the order: U(VI) > Ni(II) > Mg(II). After six cycles of use, the magnetic polymers illustrated good stability and reusability.SP201

Sample preparation using liquid membrane extraction techniques

A brief review is given of membrane extraction techniques that are seen as suitable for the extraction of various chemicals in water samples. Membrane-based extraction methods have now gained popularity as methods of choice in the extraction of both ionisable and non-ionisable molecules from different samples. The main attractive features for these techniques include the use of minimal organic solvents, high selectivity and clean-up efficiency, with high enrichment factors. In most cases the overall cost involved is low due to the simplicity of the techniques which normally involve relatively fewer steps and handling procedures as compared to many other sample-preparation techniques. The various forms and the configurations of membrane-based techniques are another attractive feature which allows the possibility of hyphenation with separation instruments such as gas/liquid chromatographs and even capillary electrophoresis.Keywords: liquid membrane extraction techniques, sample preparation, water monitoring, organic and inorganic compound

Functionalisation of cross-linked polyethylenimine for the removal of As from mining wastewater

Cross-linked polyethylenimine (CPEI) was phosphonated by reaction with phosphorous acid and formaldehyde. The functionalised polymer was used as an adsorbent for the removal of arsenic as an oxo-anion. The binding affinity of the synthesised polymer to abstract As from synthetic solutions and wastewater samples was assessed, as well as its ability to be regenerated for re-use. The PCPEI demonstrated an elevated loading capacity, removing up to 88% of As. The kinetic rates were modelled using pseudo first-order and pseudo second-order equations. The pseudo second-order equation was found to explain the adsorption kinetics most effectively, implying chemisorption. The Langmuir and Freundlich isotherms were used to interpret the adsorption of As onto PCPEI. The Freundlich isotherm was found to best fit and describe the experimental data. The thermodynamic study of the adsorption process indicated high activation energies (55.91 kJ mol-1) which confirms chemisorption as a mechanism of interaction between As and PCPEI.Keywords: Adsorption; arsenic; phosphonated cross-linked polyethylenimine, functionalisatio

Development and Application of Solid Phase Extraction Method for Polycyclic Aromatic Hydrocarbons in Water Samples in Johannesburg Area, South Africa

A solid phase extraction (SPE) technique has been developed for the quantitative determination of polyaromatic hydrocarbons (PAHs) in aqueous samples. The SPE technique involved extraction of PAHs froma 100 mL sample containing 10 % methanol as a modifier onto C18 cartridges. 40 % methanol in water was used as conditioning solvent, and 3 mL acetone:THF (1:1) as eluting solvent. After eluting, the extract was reduced to 1 mL under nitrogen and then analyzed by GC-MS. The extraction was optimized for the addition of organic modifier, sample load volume, conditioning solvent, washing solvent and eluting solvent. In order to evaluate the practical applicability of SPE technique, water samples were spiked with the PAHs to give final sample concentrationsbetween 3 and 7 μg L–1. Enrichment factors of 81–135 were achieved with relative standard deviations (RSDs) of less than 6 %. Recoveries obtained ranged from 81 to 135 %. Detection limits ranged from 20.0–52.0 ng L–1. The optimized method was validated by analyzing certified reference materials. The optimized method was then applied to spiked real river samples in and around the Johannesburg area, South Africa. The concentrations obtained varied from 22.0 to 1040.0 ng L–1. The RSDs were between 2.3 and 13 %. The overall order of PAHs levels was: phenanthrene > acenaphthene > naphthalene > fluoranthene > pyrene.Keywords: Solid phase extraction, polycyclic aromatic hydrocarbons, water samples, Johannesburg, South Afric