Biomass, Abundant Resources for Synthesis of Mesoporous Silica Material

The synthesis of mesoporous silica materials was reviewed with a view to discuss the reaction mechanism and the various attempts made at enhancing the materials’ properties by utilizing varieties of templating agents and silica frameworks from pure synthetic chemicals. This chapter also reviewed studies in which either the template or the framework was synthesized from benign reagents obtained from renewable sources, to achieve enhanced material properties. The view was to encourage the development of mesoporous silica materials in which both the template and the silica framework are from biomass origin. This approach may promote the large‐scales synthesis of mesoporous silica for commercial purposes, which had previously been hampered by the toxic nature, cost of synthetic chemical reagents, and unsustainable synthetic routes

Organochlorine Pesticide Residues in Sediments and Waters from Cocoa Producing Areas of Ondo State, Southwestern Nigeria

Thisstudyinvestigatedlevelsoforganochlorinepesticide(OCP)residuesinwaterandsedimentsamplesfromelevenriversserving as drinking water sources and receiving runoff from nearby cocoa plantations in Ondo State, Nigeria. Twenty-two composite samplesofsurfacewaterandsediments(0–3cm)werecollectedrandomlyusinggrabtechniqueandreplicatedthriceperseason. The efficiency of the two techniques [supercritical fluid extraction (SFE) and liquid/liquid extraction (LLE)] was evaluated with percentageanalyterecoveries 98.17 ± 0.03 to 134.72 ± 0.02 forSFEand 84.82 ± 3.32 to1102.83 ± 3.17 forLLE.Determinationof OCPsbygaschromatographywithelectroncapturedetectiongavehigherconcentrationsforsedimentscomparedtotheequivalent water samples. The commonly occurring pesticide residues in the sediments were (range

Speciation Study of Heavy Metals in Soil within the Vicinity of a Metal Recycling Factory at Ile-Ife, Southwestern Nigeria

A speciation study of Al, Cd, Cu, Mn, Pb and Zn in soil samples from a metal recycling factory in Ile-Ife Osun State, Nigeria, was carried out in order to assess the heavy metal pollution impact of the industrial processes on the immediate environment. Surface soil dust samples collected within the vicinity of the factory were subjected to a five-stage sequential extraction process. Levels of heavy metals in each fraction were determined using Flame Atomic Absorption Spectrophotometer (FAAS). The overall mean values obtained for the metals in the fractions gave the range: Al (0.03 ± 0.01 to 0.20 ± 0.01 µg/g ); Cd (0.03 ± 0.01 to 0.23 ± 0.02 µg/g) ; Cu (2.93 ± 0.02 to 18.30 ± 1.95 µg/g) ; Mn (17.33 ± 0.03 to 91.68 ± 2.90 µg/g); Pb (0.03 ± 0.01 to 0.43 ± 0.02 µg/g)  and Zn (8.20 ± 0.01 to 35.08 ± 0.02 µg/g) . Both the contamination index and enrichment factor results indicated that all the soil samples were contaminated with Cd while a few sites showed Cu contamination. The mobility potential of the metals in the soil sample decreased in the order: Mn > Al > Zn > Cd > Cu > Pb (West) and Cd > Al > Pb > Zn > Mn > Cu (East). The study revealed that the soil around the metal recycling factory is contaminated with heavy metals, and if left unmonitored and controlled could lead to serious environmental risk in the future.Â

Concentrations and Human Health Risk of Heavy Metals in Rivers in Southwest Nigeria

Background. Rivers are the most vital freshwater resources in the world. In Southwest Nigeria, anthropogenic activity stresses the quantity and quality of water resources. Methods. The present study examined the concentrations and human health risk of five heavy metals (manganese (Mn), arsenic (As), chromium (Cr), cadmium (Cd), and lead (Pb)) in selected rivers in Southwest Nigeria. The determination of heavy metals was carried out by atomic absorption spectrophotometry after digestion with a di-acid mixture 9:4 (v/v) (nitric acid: perchloric acid). Results. All rivers had higher concentrations of the five heavy metals in the dry season except for As in Dandaru (0.012 mg/L) and Asejire (0.016 mg/L). Manganese was observed to have the highest mean concentration among all the five metals in both the rainy and dry seasons across the sampled rivers. Generally, the annual mean concentration of metals followed the order: Mn>Cr>Cd>Pb>As in all the selected rivers. Discussion. The human health risk assessment showed that the hazard index and hazard quotient for ingestion of water for Cd and As in all the sampled rivers were higher than the acceptable limit of 1.0, indicating carcinogenic risk (CR) via direct ingestion of water. The CR via ingestion for As in all of the sampled rivers was above the remedial goal target of 1×10−6. The recorded values for chronic daily intake (CDI) were higher for Cr and Mn in all four sampled rivers. Conclusions. The results of the present study showed that As is a driver for carcinogenic risk through ingestion in all of the sampled rivers compared to other metals. Competing Interests. The authors declare no competing financial interest