Potential of Agricultural Waste (Rice Husk and Sweet Lime Peel) in Bioremediation of Se (IV) Ions from Wastewater

Abstract

Selenium, a trace element, is an essential microelement required at low levels of intake but produces toxic symptoms when the level of ingestion increases. Se (IV) is released in the waste bodies from oil refining, industrial, and manufacturing operations. Selenium has been an unrecognized pollutant in many developing countries but due to development of industries and contaminants, the need of its remediation becomes important. Rice husk (RH) and sweet lime peel (SLP) have effective adsorption efficiency for Se (IV) ions. The groups present in RH and SLP such as carboxylic, hydroxyl, amino, and carbonyl are responsible for Se (IV) ion adsorption. The surface morphology of these adsorbents is porous in nature. The adsorption equilibrium establishes in 120 min with equilibrium adsorption capacity of 0.01 mg g–1 for both RH and SLP at pH 4. The Halsey isotherm model best fits with high R2 of 0.919 (RH) and 0.975 (SLP) showing multilayer adsorption system. The monolayer adsorption capacity (qmax) of Langmuir Isotherm for SLP was 1.21 mg g–1 and for RH was 0.87 mg g–1, hence SLP shows better adsorption phenomena towards Se (IV) ions. Kinetics reaction of Pseudo 2nd order is followed for both the adsorbents with R2 of 0.997 (RH) and 0.995 (SLP) and liquid film diffusion model is the rate controlling step. The positive value of ∆H0 15.9 kJ mol–1 (RH) and 14.3 kJ mol–1 (SLP) and ∆S0 (0.06 228kJ mol–1 K–1) (RH) and 0.05 kJ mol–1 K–1 (SLP) obtained suggest the reaction is endothermic and randomness at solid-solution interface.