Temperature and pH Effect on the Sorption of Divalent Metal Ions by Silica Gel

Abstract

The sorption of Zn2+, Ni2+ and Cd2+ ions by silica gel was studied as a function of ion concentration, pH and temperature. An increase in all three parameters led to an increase in the extent of sorption for all the metal cations studied. The selectivity of the solid was observed to be in the order Zn2+ > Ni2+ > Cd2+. Sorption of the metal cations was accompanied by the release of H+ ions into the bulk phase. On average two moles of H+ ions were released per mole of metal cation sorbed. The sorption data fitted the linear forms of both the Kurbatov and Langmuir adsorption equations. The values of the binding constants were used to estimate the apparent thermodynamic parameters, ΔH and ΔS, for the adsorption process. FT-IR spectroscopic studies also showed that the uptake of metal cations by the silica gel occurred via a cation-exchange process.

Effect of pH on cadmium biosorption by coconut copra meal

“…The spectra were identical to each other, indicating that no other solid phases were present in the residues on the surface after the biosorption reactions. Similar results were also shown by Xu et al [32] and Mustafa et al [16] who argued that identical IR spectra for biosorbent before and after metal cation biosorption reveals that precipitation/co-precipitation were not dominant in the biosorption process. Thus, the uptake of cadmium ions on the copra meal surface occurred via a cation exchange mechanism.…”

“…Other possible mechanisms involve mass-transport processes, bulk transport in the liquid phase, diffusion across the liquid film surrounding the solid particles, and diffusion into micropores and macropores [15]. System parameters such as temperature and pH can also markedly influence biosorption as they affect one or more of the above parameters [16]. The kinetic reaction order of biosorbate-sorbent interactions has been described by using various kinetic models.…”

Effects of Temperature and pH on Adsorption Isotherms for Cupric and Cadmium Ions in Their Single and Binary Solutions Using Corncob Particles as Adsorbent

“…Metal solutions: 5000 and 1000 mg/l cupric and cadmium stock solutions were prepared from cupric nitrate [Cu(NO 3 ) 2 ], which has been demonstrated to hardly bind with cupric ions, [22] was used for copper in the pH range of 4.0 -5.5, and HEPES buffer (N- piperazine-N 0 -[2-ethanesulfonic acid], C 8 H 18 N 2 O 4 F, Sigma Chemical Co.) was used for cadmium in the pH range of 6.0-8.3. The buffers were 0.05 M.…”

Biogenic Silica Extracted from Salacca Leaves Ash for The Adsorption of Salycilic Acid

“…Repulsive force may occur due to the hydroxyl group in SA (Mustafa et al, 2003) . The adsorption mechanism is suggested to be intensely dependent on the surface charge by the results.…”