Physicochemical Conditions for Adsorption of Lead from Water by Rice Husk Ash

Abstract

The effects of physico-chemical parameters such as pH, temperature, and lead concentration on the efficiency of lead adsorption by rice husk ash were determined. Rice husk was incinerated at 800 °C for 6 h and then activated with 0.5 M HCl. Rice husk and rice husk ash (RHA) were characterized using scanning electron microscopy and X-ray fluorescence. Batch adsorption tests were conducted at different pH, temperature, and initial lead concentration. Kinetic studies were conducted at optimum pH of 3.0. The optimum lead removal of 80% was recorded at pH 3.0. Efficiency of lead removal by RHA decreased to 45% as pH increased to 9.0. Freundlich, Langmuir, Temkin, and Dubinin Radushkevich (D-R) isotherms performed acceptably well, with R 2 values of 0.954≤R 2 ≤0.991, 0.965≤R 2 ≤0.996, 0.949≤R 2 ≤0.979, and 0.970≤R 2 ≤0.997, respectively. Lead removal efficiency decreased from 75% to 50% as temperature increased from 30 °C to 40 °C. The adsorption of lead by RHA was by ion exchange in the acidic pH range and by physisorption in the alkaline pH range. Thermodynamic studies revealed that the process was exothermic and spontaneous and further confirmed the feasibility of the process with -22.34≤∆G 0 ≤-24.94. The intraparticle diffusion model and the pseudo first order kinetic model fit the experimental data very well, with average R 2 values of 0.985 and 0.987, respectively.

Equilibrium and Thermodynamic Investigation of Biosorption of Nickel from Water by Activated Carbon Made from Palm Kernel Chaff

“…The Freundlich adsorption isotherm describes adsorption characteristics of a heterogeneous surface. This isotherm recognizes the possibility of surface heterogeneity and intermolecular interactions between adsorbed molecules 41 . Freundlich and Langmuir isotherms have been the most widely used isotherms used by researchers to investigate the performance of adsorbents.…”

“…Arshadi et al 50 also noted that a low intake of heavy metals in an acidic medium may be as a result of particle attrition, partial protonation of the functional groups and the competition between hydrogen ions and metal ions for binding to the adsorption sites. The adsorption process is very dependent on pH and the concentration of the solution 41 . However, the effect of pH on adsorption varies according to the nature of the solute and the surface properties of the adsorbent.…”

Simultaneous adsorption of heavy metals from water by novel lemon-peel based biomaterial

“…1) i.e. the adsorbed amount of each metal ion (q, mg g −1 ) was calculated by subtracting initial and fi nal ion concentration at the moment of measurement according to Vanderborght and Van Griekenm 19 : (1) where C i and C f are initial and fi nal concentrations of each metal ion at the fi ltrate (mg L −1 ), V is the volume of solution (L) and m is the mass of the biosorbent (g). Heavy metal removal effi ciency (Eq.…”

Cd(II) Adsorption on Different Modified Rice Straws under FTIR Spectroscopy as Influenced by Initial pH, Cd(II) Concentration, and Ionic Strength

“…The functional groups such as carboxyl, silanol, etc., present in rice husk ash are favorable for Cd(II) adsorption [14]. Its porous structure has a larger specific surface area, and this morphological property is conducive to the uptake of metal ions [15]. Hence, the modification has the potential of transforming rice straw into a more valuable adsorbent to remove heavy metal pollution in water [10].…”