Wollastonite as adsorbent for removal of Fe(II) from water

Abstract

Wollastonite was used as an adsorbent for the removal of Fe(II) at different experimental conditions. The extent of removal is favourable at low concentration and low temperature. Maximum adsorption was noted at pH 4.0. The batch adsorption kinetics has been described by a first order rate expression, and the surface mass transfer coefficients and diffusion coefficients have been calculated at different temperatures. The intraparticle transport of Fe(II) within the pores of wollastonite is found to be the rate limiting step. The applicability of the Langmuir isotherm for the present system has been tested at different temperatures. Thermodynamic parameters indicate the exothermic nature of Fe(II) adsorption on wollastonite. The variation of adsorption with pH has been explained on the basis of interaction of iron species with negatively charged constituents of adsorbent.

Modeling batch kinetics and thermodynamics of zinc and cadmium ions removal from waste solutions using synthetic zeolite A

“…The rate constant of each metal ion removal from the solution by zeolite A was determined using pseudo-firstorder and pseudo-second-order rate models. The Lagergren first-order rate expression [16] is written as:…”

Removal of Lead(II) Ions from Aqueous Solutions Using a Modified Cellulose Adsorbent

“…The heat change resulting from adsorption (∆H 0 ads ) can be determined from the Van't Hoff equation by carrying out adsorption measurements at a minimum of two separate temperatures (Singh et al 1998): (4) where K c is the equilibrium constant for the adsorption process at a specified temperature (T). The change in surface free energy resulting from adsorption (∆G 0 ads ) can be evaluated using: ) for the resulting adsorption process:…”

“…In particular, Pb(II) ions are found in a variety of wastewater streams from industries such as acid battery manufacturing, metal plating and finishing, ammunition, ceramic and glass industries (Goel et al 2005). Concentrations of Pb(II) ions in industrial wastewaters can range from 200 mg/dm 3 to 500 mg/dm 3 (Ucun et al 2003). At high concentrations, Pb(II) is known to be toxic to both plants and animals as it accumulates in vital organs and bones and can cause a number of diseases ranging from anaemia to nervous system degeneration (Adriano 1986).…”

“…was identified as cellulose-g-GMA-imidazole. The method of graft polymerisation has gained importance in the modification of the chemical and physical properties of pure cellulose for different uses (Vitta et al 1985;Gurdag et al 1997). The adsorption of heavy metal ions is one application which has been studied (Iwakura et al 1964;Kubota and Suzuki 1995).…”

“…The pseudo-second-order kinetic expression [equation (10)] can be used to assess the dependency of the process on the sorbed Pb(II) concentration (Xing et al 1994): (10) where k 2 [dm 3 /(min mg)] is the overall rate constant for the adsorption process, q e (mg/g) is the amount of Pb(II) ions adsorbed at equilibrium and q t (mg/g) is the amount of Pb(II) ions adsorbed at any time t. Re-arrangement of equation (10) leads to the linearised form given in equation (11): (11) The initial sorption rate, h, obtained as t → 0, may be defined as: (12) The initial sorption rate, h, the equilibrium sorption capacity, q e , and the pseudo-second-order rate constant, k 2 , can be obtained experimentally from the slope and intercept of the plot of t/q t versus t (Ho 2003). Figure 5 shows the corresponding second-order plots for Pb(II) ion adsorption onto cellulose-g-GMA-imidazole, the constants for the process being listed in Table 4.…”