Rice husk a low cost agricultural waste was assessed for its efficiency as an oil spill sorbent by comparing its oil (crude oil, diesel and kerosine) uptake with that of a standard; conventional synthetic sorbent mat used in oil spill clean-up. The experiment was performed under the same experimental condition and procedure. The sorption process of crude oil, diesel and kerosine onto rice husk and the standard was studied using Langmuir, Freundlich, Elovich, Temkin and Dubinin Radushkevich adsorption models while the sorption kinetics was studied using Lagergren pseudo-first-order, pseudo-second-order, intraparticle diffusion and liquid film diffusion models. Suitable environmental applicability of both sorbents was also studied.. The result of the study shows that rice husk sorbed 3.30g of crude oil, 2.50g of diesel and 1.95g of kerosine per unit mass while the standard sorbed 11.50g of crude oil, 10.34g of diesel and 8.20g of kerosine per uint mass. About 2.46g of crude oil, 1.60g of diesel and 1.57g of kerosine were recovered from a unit mass of rice husk, while, 9.67g of crude oil, 8.40g of diesel and 6.50g of kerosine were recovered from a unit mass of synthetic sorbent mat. The amount of oils retained by a unit mass of rice husk is about 0.84g of crude oil (25 % of absorbed crude oil), 0.90g of diesel (36 % of absorbed diesel), and 0.38g of kerosine (20 % of absorbed kerosine), while, 1.83g of crude oil (15 % of absorbed crude oil), 1.94g of diesel (19 % of absorbed diesel) and 1.70g of kerosine (20 % of absorbed kerosine) were retained by a unit mass of synthetic sorbent mat. The result of the study indicates that the standard is a better sorbent for oil removal than rice husk. Rice husk has the ability to retain sorbed oil which makes it a good sorbent when oil recovery is not required. The sorption process for both sorbents follows the Langmuir isotherm. intraparticle diffusion contributed more than liquid film diffusion in the sorption mechanism for the standard, while the reverse is the case for rice husk. The standard and rice husk can be applied on oil spill clean-up on land and surface waters. Rice husk is not a very efficient sorbent for oil spill mop.
Key words: Rice husk, adsorption isotherm, adsorption kinetics, crude oil, refined petroleum products
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