Valorization of rice husk silica waste:Organo-amine functionalized castor oil templated mesoporous silicas for biofuels synthesis

Rice husk is a rich source of waste silica which has potential for application in the preparation of porous materials for use as catalyst supports or sorbents. Here we report on the synthesis of rice husk silica (RHS) and mesoporous templated rice husk silica (MT-RHS) using sodium silicate, obtained from rice husk ash, and castor oil as a pore directing agent. The resulting silicas were functionalized with 3-aminopropyltriethoxysilane (APTS) or 3-diethylaminopropyltrimethoxysilane (DEPA), and their catalytic activity evaluated in the transesterification of model C4–C12 triglycerides (TAG) to their corresponding fatty acid methyl esters, of relevance to biodiesel synthesis. Castor oil templating enhances the surface area of rice husk silica, and introduces uniform 4 nm mesopores, albeit as a disordered pore network. Post-synthetic grafting of silica by APTS or DEPA resulted in base site loadings of 0.5 and 0.8 mmolg−1 respectively on RHS and MT-RHS. Turnover frequencies of amine-functionalized MT-RHS were 45–65% greater than those of their amine-functionalized RHS counterparts for tributyrin transesterification. Switching from a primary (APTS) to tertiary (DEPA) amine increased activity three-fold, delivering 80% tributyrin conversion to methyl butyrate in 6 h. DEPA-MT-RHS was effective for the transesterification of C8 and C12 triglycerides, with methyl caproate and methyl laurate selectivities of 93% and 71% respectively in 24 h

Phylogeography and conservation genomics of the African lion (Panthera leo) at a continental and local scale based on mitochondrial and nuclear molecular markers

Presented at the 9th international wildlife ranching symposium: wildlife - the key to prosperity for rural communities, held on 12-16 September 2016 at Hotel Safari & the Safari Court, Windhoek, Namibia.The African lion (Panthera leo) is listed as "vulnerable" by the IUCN Red List, mainly threatened by indiscriminate killing, primarily as a result of retaliatory or pre-emptive killing to protect human life and livestock, and prey base depletion. Habitat loss and conversion has led to a number of subpopulations becoming small and isolated. With the weakened connectivity between the main strongholds, genetic drift and loss of genetic diversity could affect the genetic health of the species. In the present study, we investigated the evolutionary history of the species at different scales of time and space. A total of 182 samples were used, including a larger number of 77 samples from Tanzanian protected areas. The mitochondrial cytochrome b gene was sequenced and the specimens were genotyped for 11 microsatellites and more than 9,000 SNPs. The preliminary results indicate that the lion is structured into two lineages at the continental scale (West-Central vs South-Eastern), a pattern observed within many other large African savanna species displaying large distribution ranges. Pleistocene climatic oscillations and biogeographical barriers were proposed as the main factors to have driven the lineage sorting. The first results based on microsatellites highlighted that the Tanzanian population displayed good level of genetic diversities with no signs of inbreeding. Indication of isolation-by-distance nevertheless highlighted a potential future impact of fragmentation on the population genetic health. SNPs allowed to identify 3 populations of lions in Tanzania, geographically structured. Using various molecular markers, the present work will further explore the taxonomy and the evolutionary history of the African lion for bringing insights in its conservation requirements

Visual MINTEQ simulation for prediction of the adsorption of arsenic on ferrihydrite

The surface of ferrihydrite adsorbs arsenic (As) effectively. In this investigation, the As laced water samples collected from Geita and Mara regions within the Lake Victoria Basin (LVB) under DAFWAT project were simulated onVisual MINTEQ 3.1 software to determine the amount of ferrihydrite required to adsorb a given amount of As from water. Model simulations show that As concentration of ≤1 mM can be completely adsorbed by 4 g L−1 ferrihydrite. Previous studies show that the lower pH 4 to 4.5 influences adsorption, while it decreases as pH increases as well as when As concentration increases. The increase of adsorbent dose to 4 g L−1 has shown to improve As(V) adsorption on pH 5 to 8 at 100%. The amount of adsorbent can now be used for laboratory adsorption experiments by using iron-based materials or commercial ferrihydrite.</p