One of the most crucial attributes of synthetic organic chemistry is to design organic reactions under the facets of green chemistry for the sustainable production of chemicals.

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A one-pot method was employed to immobilize sulfonic acid onto silica obtained from rice husk ash using 3-(mercaptopropyl)trimethoxysilane to form a solid catalyst denoted as RHASO3H. BET measurements of the catalyst showed the surface area to be 340 m2 g−1 with the average pore volume of 0.24 mL g−1 and the pore diameter of 2.9 nm. Acidity test of cation exchange capacity and pyridine adsorption studies revealed the presence of Brønsted acid sites on the catalyst surface. The catalyst was used in the acetalization reaction of glycerol with benzaldehyde. Under optimized conditions, the reaction showed the maximum conversion of 78 % after 8 h with 67 % selectivity towards the five membered ring isomer. Variation in the glycerol concentration had a significant effect on the reactants conversion. A single crystal X-ray study of one of the products proved the existence of a unique trimer formed by hydrogen bonding by the six-membered cis-isomer. The catalyst was several times recycled without any loss of its catalytic activity.

This study was carried out to evaluate the efficiency of metals (Ni, Cr, and Mn) removal using, raw and carbonized rice, millet and corn husks as low cost adsorbents. The sorption of these metal ions from aqueous solution was determined using Atomic Absorption Spectroscopy Analysis (AAS). Characterisation of the adsorbents using Fourier Transform Infra Red) FTIR) and Scan Electron Microscopy (SEM) images revealed some changes before and after the adsorption process. This indicated that, most likely adsorption has been taken place between the metal ions and the adsorbents in the aqueous solution. Batch experiments were carried out to determine the effect of different parameters such as adsorbent dose, pH of the medium, contact time and agitation rate. The result obtained showed that the sorption process was largely dependent on metal ion concentration, adsorbent dose and contact time. The experimental data was analyzed using paired sample -T test. The study also showed that, all the husks were effective for the quantitative removal of various toxic heavy metals and can be used as low cost and highly efficient adsorbents for the removal of heavy metal ions from industrial effluents.Citation: Batagarawa SM, Ajibola AK. Comparative evaluation for the adsorption of toxic heavy metals on to millet, corn and rice husks as adsorbents.

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