Direct conversion of eggshell to hydroxyapatite ceramic by a sintering method

Mercuric pollution of surface water, superficial sediments, Nile tilapia (Oreochromis nilotica Linnaeus 1758 [Cichlidae]) and yams (Dioscorea alata) in auriferous areas of Namukombe stream, Syanyonja, Busia- Uganda

“…The mean THg content of the sediments in this study is lower than the values registered in other global studies such as 0.265µgg -1 reported by Donkor et al [82] in Pra river (Ghana), 0.7-9.3µgg -1 reported by Ramirez-Requelme et al [83] in Amazon and 0.3-0.9µgg -1 recorded by Feng et al [84] in Shaanxi Province of the Peoples` Republic of China. However, Lasut et al [85] in Indonesia, Pataranawata et al [86] in Thailand, Mohan et al [51] in Nilambur, Kerala-India and Oladipo et al [57] in Manyera river, Nigeria reported lower THg content of sediments of 0.010-0.017, 0.096-0.402, 0.103-0.46, and 0.018µgg -1 respectively which are comparable to the mean THg concentrations recorded in this study. Taylor et al [87] reported that the drainage sediments from upstream of Uvinza on the Malagarasi river (Tanzania) contain THg in the range of 0.17-0.24 µg/kg, which were lower than for sediments from Ilagala with 0.10 to 0.66 mg/kg THg but all higher than the mean THg registered in this study.…”

“…All the THg concentrations of the sediments were lower than the Probable Effect Level (PEL) of 0.70µgg -1 for Hg in sediments postulated by Smith et al [88] and MacDonald [89]. THg in the sediments lying between TEL and PEL is expected to be associated with adverse biological effects [51]. Also, among the bottom sediment samples, none had THg higher than the background concentration of 0.25µgg -1 , which is considered as normal in non-contaminated sediments [90].…”

“…Since the stream contains organic matter, most of the Hg could have been retained within the sediments at upsluice and mid sluice, making them undetectable downstream. It is reported that organic matter can increase Hg methylation by stimulating heterotrophic bacteria (Pseudomonas species) in aerobic conditions [50] or abiotic methylation [51]. In anaerobic condition, Hg reacts with organic carbon in the sediments to form toxic methyl and di-methyl Hg [51].…”

“…It is reported that organic matter can increase Hg methylation by stimulating heterotrophic bacteria (Pseudomonas species) in aerobic conditions [50] or abiotic methylation [51]. In anaerobic condition, Hg reacts with organic carbon in the sediments to form toxic methyl and di-methyl Hg [51]. Some anaerobic bacteria that possess methane synthetase are also reported to be capable of Hg methylation [52].…”

Advances in Synthesis and Functional Modification of Nanohydroxyapatite

“…Phase pure highly crystalline HA derived from eggshell was reported recently. A flower-like morphology HA (Figure 1) can be obtained via a direct solidstate sintering method after preheat treatment of calcined eggshell and dicalcium phosphate dihydrate at 800 ∘ C [27].…”