Pre-concentration of heavy metals in aqueous environments using electrospun polymer nanofiber sorbents

This thesis presents an alternative approach for pre-concentrating heavy metals in aqueous environments using electro spun polymer nanofiber sorbents. The conditions for electrospinning polyethersulfone, polystyrene, polysulfone and polyamide-6 were optimized. The morphologies and porosities of the electrospun nanofibers were studied using SEM and BET nitrogen gas adsorptions. The nanofibers had mesoporous morphologies with specific surface areas up to 58 m2/g. The electro spun nanofiber sorbents were characterized in terms of their tunability for both uptake and release of heavy metals. The usability of the sorbent was also assessed. The sorbents showed fast adsorption kinetics for heavy metals « 20 min for As, Cu, Ni and Pb) in different aqueous environments. The adsorption characteristics of the sorbents best fitted the Freundlich isotherm and followed the first order kinetics. The efficiencies of adsorption and desorption of heavy metals on both imidazolyl-functionalized polystyrene and amino-functionalized polysulfone sorbents were more than 95% up to the fifth cycle of usage. Reusability improved dramatically (up to 10 runs of usage) when mechanically stable amino-functionalized nylon-6 electro spun nanofibers were used. The capacity of the amino-functionalized nylon-6 sorbent to pre-concentrate heavy metals compared very favourably with those of aqua regia and HN03+H202 digestions especially in less complex matrices. Due to their highly porous nature, the electro spun nanofibers exhibited high adsorption capacities (up to 50 mg/g) for heavy metal ions. The loading capacities achieved with the imidazolyl-functionalized sorbent were higher than those for amino-functionalized mesoporous silica and biomass-based sorbents. The electro spun nanofiber sorbents presents an efficient and cost effective alternative for preconcentrating heavy metals in aqueous environments

Heavy metal content and potential health risk of geophagic white clay from the Kumasi Metropolis in Ghana

AbstractGeophagia is the craving for non-food substances and commonly practiced among pregnant women and children. Consumption of geophagic clay samples can have serious implications on the health of the consumers as a result of the presence of toxic metals such as Pb, As, Hg and Cd. This study sought to determine the levels of heavy metals in the studied geophagic clay samples and to determine the potential risks of heavy metals as cumulative carcinogenic and non-carcinogenic risks to the health of the consumers via oral (ingestion) and dermal exposure routes. A total of thirty (30) white clay samples were analysed using Niton Thermo scientific XRF Analyser (Mobile Test S, NDTr-XL3t-86956, com 24). The clay samples were found to contain essential elements such as Ca, Fe, K and Zn as well as toxic metals such as As and Pb. There were isolated cases of the presence of Hg and all samples had Cd levels below detection. Health risk indices such as hazard quotient and cancer risk were calculated and the results indicated that consumers are likely to suffer from cancer through ingestion of geophagic clay. Bioaccessibility studies were done on zinc and it did not indicate any potential toxicity due to zincs essential nature. The levels of heavy metals in some of the geophagic clay consumed by some residents in the Kumasi were high compared to the Permitted Maximum Tolerable Daily Intake (PMTDI) by (WHO/FAO) and may pose potential health threat over time

Pesticide Residues in Honey from the Major Honey Producing Forest Belts in Ghana

Concentrations of pesticides residues in honey sampled from the major honey producing forest belts in Ghana were determined. Samples were purposively collected and extracted using the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method and analysed for synthetic pyrethroids, organochlorine, and organophosphate pesticide residues. Aldrin, γ-HCH, β-HCH, ∑endosulfan, cyfluthrin, cypermethrin, deltamethrin, permethrin methoxychlor, ∑DDT, chlorpyrifos, fenvalerate, malathion, dimethoate, and diazinon were all detected at the concentration of 0.01 mg/kg, while cyfluthrin and permethrin were detected at mean concentrations of 0.02 and 0.04 mg/kg, respectively. All the pesticide residues detected were very low and below their respective maximum residue limits set by the European Union. Hence, pesticide residues in honey samples analyzed do not pose any health risk to consumers

Accumulation of toxic metals in fish raised from sewage-fed aquaculture and estimated health risks associated with their consumption

We determined the health risks associated with the consumption of toxic metals in fish raised from a sewage-fed aquaculture. Concentrations of toxic metals in fish, water and sediments in the waste stabilization ponds were determined using atomic absorption spectrophotometer. All the fish samples had some amount of toxic metals in them. The maximum concentrations of lead, cadmium, copper, chromium and mercury in the water samples were 28.7, 18.2, 246.0, 310.0 and 150.0 μg/kg, respectively, which were all below the US-EPA limits. The maximum concentrations of Pb, Cu, Cr and Hg in all sediment samples are 27.4, 323.0, 240.0 and 150.0 μg/kg, respectively. The maximum concentrations of Pb, Cd, Cu, Cr and Hg in the fish samples were 48.6, 18.9, 434.0, 300.0 and 320 μg/kg, respectively, which were below the EU maximum residual limit. The estimated daily intake calculated ranged from 1.0 × 10−6 to 6.0 × 10−5 mg/kg/day. Mercury showed the highest health risk, while Pb had the lowest. None of the risk indexes was up to 1, indicating that human beings who consume fish from the ponds are not be exposed to health risks as far as toxic metals are concerned

Multidimensional Child Poverty in Ghana : Measurements, Determinants, and Inequalities

Early childhood deprivations and inequalities have social and economic implications in adulthood and thus, their elimination is essential for child development. However, child-level estimates of poverty are rare in low income countries. Using data from two recent rounds of the Ghana Demographic and Health Survey, we measure the extent and sources of childhood deprivations in Ghana and examine subgroup differentials in child poverty. In addition, we examine the child quality-quantity by estimating the causal relationship between number of children and child poverty. Finally, we assess the sources of rural-urban inequalities in child poverty. We find that despite declining incidence and intensity of multidimensional child poverty, significant subgroup differentials persist in Ghana. The findings of the paper reveal that living standards is the main contributor to multidimensional poverty in early childhood in Ghana. Our findings also confirm a significant causal relationship between child quality and quantity in Ghana, there exist a positive relationship between the number of children and the intensity of child poverty in Ghana. Finally, we find that rural-urban inequalities in child multidimensional poverty in Ghana are attributable to differences in observed maternal and household characteristics between rural and urban areas. The persistence of subgroup disparities in child poverty may be detrimental to achieving equitable and inclusive growth in the country. There is the need for considerations of equity, fairness and social justice in the distribution and development of social services and economic infrastructure to ensure even distribution of social and economic opportunities and promote social mobility across groups