Kinetics and pseudo-isotherm studies of 4-nitrophenol adsorption onto mansonia wood sawdust

Kinetic models alone are usually applied to describe adsorption onto porous materials, but little attention is given to the fact that diffusion of pollutants especially large organic pollutant molecules may also control the reaction rates. In this investigation, the kinetics and pseudo-isotherm studies of an organic pollutant, 4-nitrophenol from aqueous solution on mansonia sawdust was examined. The intraparticle diffusion particle plots revealed three distinct sections representing sorption into external diffusion, intraparticle diffusion and diffusion to a biosorption site within the particles. The fractional removal of pollutant versus square root of time plots further revealed three sectional straight lines whose slope may represent the rates of pollutant sorption into macro-, meso- and micropores.The equilibrium capacities determined using four forms of the Ho's pseudo-second order model and the Type-1 pseudo second-order expression was also used to evaluate equilibrium concentrations and pseudo-isotherms were obtained by changing initial concentration, C₀.