Sorption of synthetic dyes on low-cost solid sorbents is a simple technique for their removal from wastewater. Recent initiatives in the sorption process have sought the use of activated carbon derived from agricultural wastes as it provides an attractive and cheaper alternative to commercial activated carbon, which is usually expensive. This research investigates the sorption kinetics and equilibrium of two synthetic cationic dyes, crystal violet and methylene blue from aqueous media using activated carbon prepared from an agro-waste, Millettia thonningii seed pods. Sorption experiments were carried out using the batch process. The kinetic data were analyzed using the pseudo-first-order, pseudo-second-order, and intraparticle diffusion models while the equilibrium data were analyzed using the Langmuir, Freundlich, and Redlich–Peterson isotherm models. Nonlinear regression method was used to fit the data to the isotherm models in order to determine model parameters and the best-fit isotherms. Thus, three error functions; coefficient of determination, Chi-square statistic test, and the sum of error squares were applied to evaluate the sorption data. The pseudo-second-order model best described the sorption kinetics of both dyes while the Redlich–Peterson model described the equilibrium data the most, followed closely by the Freundlich isotherm model indicating a heterogeneous sorbent surface. The experimental results indicate that the agro-waste derived activated carbon is a viable adsorbent for the remediation of dye-contaminated water.

In this report, synthesis, growth and formation kinetics of silver nanoparticles mediated by various plant extracts in their biodiversity have been monitored using UV-Vis spectrophotometer by sampling at time intervals during bioreduction process. Plasmon band resonance of the silver nanoparticles was observed as the reaction progresses indicating nucleation and particle formation. There were cases of red shifting indicating particle size increase. In the bioreduction process, onset of nanoparticle nucleation and growth were observed within 2, 5, 10 or 30 min and eventual formation of spherical or quazi-spherical amidst twinned morphology as determined by transmission electron microscope (TEM). The nanosilver growth kinetics mechanism has been probed using a time-resolved UV-Vis in conjunction with TEM following existing Lifshitz-Slyozov-Wagner theory. For some biological extractmediated synthesis, a single-stage mechanism that is diffusion controlled following Ostwald ripening (OR) is proposed. Whereas, for other bioreduction process, a double stage involving (1) initial OR followed by (2) surface adsorption-oriented attachment is proposed for temporal evolution of the nanosilver in green environment.

The dependence of Nigerian Government on foreign technology for oil spill cleanup in its water bodies does not add local content value in the development of the Nation's economy. Acetylation of natural cellulose gives a material with high sorption capacity for oil in water. This research investigates crude oil sorption from water using acetylated and unacetylated lignocellulose. Oil palm empty fruit bunch (OPEFB) and cocoa pod (CP) were acetylated under mild conditions. The acetylated (modified) and unacetylated (unmodified) sorbents were used to sorb oil from water, and their sorption capacities and mechanisms were compared. Paired t test showed there was significant difference in the sorption capacities of modified and unmodified sorbents. Sorption of oil from water was found to be time and concentration dependent. Equilibrium studies showed that CP has higher sorption capacity than OPEFB and acetylation enhanced the crude sorption capacities of the sorbents. Crude oil sorption from water is a monolayer process that might have progressed from multilayer processes. Kinetic studies showed that sorption of crude oil by the sorbents was diffusion-controlled with the aid of physisorption and chemisorption mechanisms. Fourier transform infrared and scanning electron microscope analyses showed clear evidence of successful acetylation and oil sorption.

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The economic downturn in Nigeria and Structural Adjustment Programme led to the flooding of Nigerian market with imported used automobiles. Most of these vehicles needed refurbishing and reworking. The present study is a human health risk assessment of metal exposure resulting from reworking of imported used vehicles in Nigeria. Scrap paint dusts from 56 Japanese made cars were collected from 8 different mechanic villages (workshops A-H] in Southeastern Nigeria. Scrap paints were homogenized, mixed, divided into fine particles and digested by standard method. The filtrates were assayed of lead, manganese and copper with atomic absorption spectrophotometry (AAS). Workshop B has the highest concentration of Pb (4.26 ± 0.93). Manganese in workshops A and F were (3.31 ± 0.85) and (3.04 ± 0.47) respectively and were higher than the levels from workshops C, B, D, G and H. Copper in workshop D (7.11 ± 0.21) was significantly greater than the other workshops. The highest hazard quotient (HQ) through ingestion, inhalation and dermal exposures in adults were 9.44E-05 (workshop B), 4.20E-01 (workshop B) and 1.08E-05 (workshop D) respectively. The highest values for HQ through ingestion, inhalation and dermal in children were 8.82E-04, 7.61E-01 and 2.86E-05 all in workshop B respectively. For children, the highest carcinogenic risk levels were 7.05E-08, 6.09E-05 and 2.29E-10 for ingestion, inhalation and dermal exposures respectively. In adults, the carcinogenic risk levels were 7.55E-09, 3.39E-05 and 8.67E-10 for ingestion, inhalation and dermal exposures respectively. Chronic exposure to scrap car paint dusts may be of significant public health importance in Nigeria as this may add to the body burden of some heavy metals.