Removal of Methylene Blue From Aqueous Solution Using Activated Rice Husk Biochar: Adsorption Isotherms, Kinetics and Error Analysis

Abstract

Removal efficiency of methylene blue (MEB) from aqueous media was studied under different experimental conditions of pH, contact time and initial concentration of the adsorbate. Activated rice husk biochar (ARHB) was characterized using BET surface area and XRD. The XRD diffraction indicated amorphous nature of the biochar with pore size (cc/g) and pore surface area (m2/g) of 9.369 and 27.32 respectively from BET surface area plot. Equilibrium isotherm based on coefficient of non-determination indicated the following order as best fit model: Hill ˃ Kiselev ˃Elovic ˃Flory-Huggins > Langmuir > Jovanovic > Harkin-Jura >Freundlich > Henry > Temkin >Redlich Peterson>Durbinin-Kaganer Redushkevich >Hill-de Boer > Fowler-Guggenheim. Based on the highest correlation coefficient and the lowest values of the error functions applied to the kinetic models, Weber and Morris intra-particle diffusion and liquid film diffusion were noted to be in control of the sorption rate. The MEB sorption capacity of the activated biochar was 356.99 mmolkg-1 which was in the range of commercially available activated carbons and other biosorbents.

Equilibrium and Kinetic Studies for The Adsorptive Removal of Lead (II) Ions from Aqueous Solution Using Activated Plantain Peel Biochar

“…The Jovanovic isotherm Jovanovic isotherm model also assumes a close approximation for monolayer localized adsorption without lateral interactions. It is similar to Langmuir model, except that the Jovanovic model allows surface binding vibrations of an adsorbed species [3,12]. The linear form of the model is shown in equation 7 and a correlation coefficient (R 2 ) of 0.722 obtained from the plot of Inqe against Ce (Figure 7).…”

“…Further increase in the concentration of the metal ion decreases the quantity adsorbed at pH 10 at room temperature. The decrease could be that the adsorptive sites are saturated until no more exposed surface resulting from intermolecular hydrogen bonding and hence regress in the amount adsorbed [3].…”

“…This model is often applied under the condition of intermediate mode of sorbate concentration. It assumes that the fall in the heat of sorption of molecules in the layer to decreases linearly with area of coverage owing to sorbent or sorbate interaction instead of logarithmic (Nworie, 2019). Equation 8 is the linear form of Temkin isotherm model.…”

“…where C is the intercept and kp is the intraparticle diffusion rate constant (mg/g/min1/2), which can be evaluated from the slope in the linear plot of qt against t 1/2 . The intercept of the plot reflects the boundary layer effect [3]. The larger is the intercept, the greater will be the contribution of the surface sorption in the rate-controlling step.…”

“…The indiscriminate discharge of heavy metals such as zinc, lead, cadmium through anthropogenic means into the environment has been reported as the major cause of water and soil pollution [1][2][3]. The presence of heavy metals on the environment is of global concern due to possible adverse effects on human health, as well as aquatic flora and fauna.…”