Kinetic and equilibrium study for the sorption of Pb(II) ions from aqueous phase by water hyacinth (Eichhornia crassipes)

This paper reports the kinetic and equilibrium studies of Eichhornia crassipes root biomass as a biosorbent for Pb(II) ions from aqueous system. Batch adsorption studies were carried out to examine the influence of various parameters such as the pH, contact time, adsorbent dose, initial metal ion concentration, temperature and agitation speed on the metal ion uptake. Uptake of Pb(II) ions on the E. crassipes roots showed a pH-dependent profile. The maximum metal uptake values were 164 μg/mL. Langmuir model fitted the experimental sorption equilibrium data with a good fit (R2 > 0.99). The biosorption kinetics was described by the pseudo-second-order model (R2 > 0.99). KEY WORDS: Water hyacinth, Biosorption, Kinetics, Water treatment, Pb(II) removal Bull. Chem. Soc. Ethiop. 2012, 26(2), 181-193.DOI: http://dx.doi.org/10.4314/bcse.v26i2.

Fluoride adsorption onto an acid treated lateritic mineral from Kenya: Equilibrium studies

Adsorption of fluoride (F) ions from water using acid treated lateritic mineral (LM-1) from Kenya was studied by batch experiments. The effect of acid-treatment of adsorbent and change in temperature, mass of LM-1, pH and selected competing ions was evaluated. The adsorption process was strongly influenced by temperature, pH and adsorbent dosage. The percentage F removal increased the presence of the nitrate and the chlorate ions but decreased the presence of sulphates, chloride and phosphate ions. Adsorption isotherms were classified according to Giles’ classification and the adsorption data validated using Langmuir and Freundlich isotherms. The data correlated to both the Langmuir and Freundlich isotherms although the data fit to the Freundlich model was somehow better. This showed that F adsorption onto LM-1 followed a mixed adsorption mechanism in which physisorption reactions involving intra-particle diffusion of F into mesoporous sites in LM-1 became increasingly important at higher concentrations and temperatures whereas ion-exchange mechanism involving surface OH- appear to dominate at low surface coverage in more alkaline conditions. With maximum adsorption capacity of 10.5 mg/g, LM-1 could be used to remove F water.Key words: Equilibrium analysis, fluoride adsorption, Langmuir and Freundlich isotherms, Lateritic mineral adsorbent, low-cost adsorbents

Equilibrium Studies of Fluoride Adsorption onto a Ferric Poly 12mineral from Kenya

African countries along the Great Rift Valley are among areas of the world where excess fluoride in water sources is a major public health problem. In this work, the removal of fluoride (F) from water solutions using a ferric poly-mineral (FPM) from Kenya was therefore studied using batch adsorption experiments. The effect of change in solution pH, temperature, initial concentration of F, mass of FPM, contact time and presence of various competing ions on F adsorption onto FPM was evaluated. Adsorption isotherms were then applied to the adsorption data to characterize and establish the adsorption capacity of the mineral. The adsorption of F onto FPM was found to be a fast process and, at 1000 mg/L initial F concentration at pH 3.32 and 293 K and using 0.2 g/mL adsorbent dosage, over 90% F removal from solution could be achieved in 30 min. Based on Giles system of classification of adsorption isotherms, F adsorption isotherm conformed to L4 Langmuir-type isotherms. This indicated that FPM is composed of a heterogeneous surface consisting of sites which, during adsorption, filled-up with F ions in succession. The adsorption data also correlated to Langmuir and Freundlich models indicating that F adsorption onto FPM was a mixed process involving chemisorption onto surface sites followed by gradual intra-particle penetration of F into mesoporous structure of the mineral. High mean Langmuir adsorption capacity of 10.8 mg/g, indicate that the mineral could be of use as an inexpensive substrate for the removal of F from aqueous streams

Kinetic and equilibrium study for the sorption of Pb(II) ions from aqueous phase by water hyacinth (<i>Eichhornia crassipes</i>)

This paper reports the kinetic and equilibrium studies of Eichhornia crassipes root biomass as a biosorbent for Pb(II) ions from aqueous system. Batch adsorption studies were carried out to examine the influence of various parameters such as the pH, contact time, adsorbent dose, initial metal ion concentration, temperature and agitation speed on the metal ion uptake. Uptake of Pb(II) ions on the E. crassipes roots showed a pH-dependent profile. The maximum metal uptake values were 164 μg/mL. Langmuir model fitted the experimental sorption equilibrium data with a good fit (R2 › 0.99). The biosorption kinetics was described by the pseudo-second-order model (R2 › 0.99).DOI: http://dx.doi.org/10.4314/bcse.v26i2.

Fluoride Adsorption onto Acid-Treated Diatomaceous Mineral from Kenya

International audienc

Spent Bleaching Earth as a Pozzolanic Material

This paper proposes a cementing material from spent bleaching earth (SBE). SBE consists mainly of residual oil and bleaching clay. The SBE reported in this case is the waste material from vegetable oil processing industries. One of the SBE samples tested had a calorific value of 15.8 J/g. The ash content was 52.3 to 58.6 %. When calcined at 550 &#61616;C for four hours, the resulting ash met the Kenya Standard 02 1263 chemical composition requirements for pozzolanas. When calcined in small quantities in a muffle furnace and tested with commercial hydrated lime (CHL), the material met the ASTM 593 part C requirements for use of pozzolana with lime. The pozzolanic activity of the ashed SBE vis a vis commercial volcanic tuff was investigated. A 1: 2 ratio of the lime to the ash gave the highest compressive strength. At the 28th day of curing, the compressive strength was 10.9 Mpa while that of the volcanic tuff-lime was 8.99 Mpa. The setting time of a workable paste of the ashed SBE-lime material was well within the Kenya standard 02 1263 requirements for Portland pozzolana cements. Key words: Cement, pozzolana, Spent bleaching earth, volcanic tuff, hydrated lime, compressive strengths, setting time

Regeneration of spent bleaching earth and its adsorption of copper (II) ions from aqueous solutions

International audienc

Equilibrium Studies of Fluoride Adsorption onto a Ferric Poly−mineral from Kenya

African countries along the Great Rift Valley are among areas of the world where excess fluoride in water sources is a major public health problem. In this work, the removal of fluoride (F) from water solutions using a ferric poly-mineral (FPM) from Kenya was therefore studied using batch adsorption experiments. The effect of change in solution pH, temperature, initial concentration of F, mass of FPM, contact time and presence of various competing ions on F adsorption onto FPM was evaluated. Adsorption isotherms were then applied to the adsorption data to characterize and establish the adsorption capacity of the mineral. The adsorption of F onto FPM was found to be a fast process and, at 1000 mg/L initial F concentration at pH 3.32 and 293 K and using 0.2 g/mL adsorbent dosage, over 90% F removal from solution could be achieved in 30 min. Based on Giles system of classification of adsorption isotherms, F adsorption isotherm conformed to L4 Langmuir-type isotherms. This indicated that FPM is composed of a heterogeneous surface consisting of sites which, during adsorption, filled-up with F ions in succession. The adsorption data also correlated to Langmuir and Freundlich models indicating that F adsorption onto FPM was a mixed process involving chemisorption onto surface sites followed by gradual intra-particle penetration of F into mesoporous structure of the mineral. High mean Langmuir adsorption capacity of 10.8 mg/g, indicate that the mineral could be of use as an inexpensive substrate for the removal of F from aqueous streams

Removal of Cadmium(II) Ions from Water by Adsorption using Water Hyacinth (Eichhornia crassipes) Biomass

The kinetics and equilibrium binding of Cd(II) ions onto raw water hyacinth (Eichhornia crassipes) biomass (RBH) were investigated with the view to utilize it as a low-cost biosorbent for removal of toxic metal ions from water. The biosorption was analyzed through batch experiments with respect to the effect of contact time, agitation speed, biosorbent dosage, solution pH, Cd(II) concentration, and the presence of other metal ions. Cadmium adsorption onto Eichhornia crassipes biomass was pH- and temperature-dependent, and complete Cd(II) removal from solution was achieved at all Cd(II) concentrations up to 10 mg/L. The biosorption equilibrium was described by Langmuir and Freundlich isotherms, and the RBH Cd(II) uptake capacity was 104 mg/g. The biosorption process followed the pseudo-second-order model (R2 0.99). The root biomass of water hyacinth had one of the highest Cd(II) sequestration efficiencies when compared to other biosorbents that have been used to remove Cd(II) from water

<b>Kinetics and thermodynamics of aqueous Cu(II) adsorption on heat regenerated spent bleaching earth</b>

This study investigated the kinetics and thermodynamics of copper(II) removal from aqueous solutions using spent bleaching earth (SBE). The spent bleaching earth, a waste material from edible oil processing industries, was reactivated by heat treatment at 370 ^oC after residual oil extraction in excess methyl-ethyl ketone. Copper adsorption tests were carried out at room temperature (22±3 ^oC) using 5.4 x 10^-3C M metal concentrations. More than 70% metal removal was recorded in the first four hours although adsorption continued to rise to within 90% at 42 hours. The pH, adsorbent dosage and initial concentrations were master variables affecting RSBE adsorption of Cu(II) ions. The adsorption equilibrium was adequately described by the Dubinin-Radushkevich (D-R) and the Temkin isotherms and the maximum sorption capacity derived from the D-R isotherm was compared with those of some other low cost adsorbents. The adsorption process was found to follow Lagergren Pseudo-second order kinetics complimented by intra-particle diffusion kinetics at prolonged periods of equilibration. Based on the D-R isotherm adsorption energy and the thermodynamic adsorption free energy ∆G, it was suggested that the process is spontaneous and based on electrostatic interactions between the metal ions and exposed active sites in the adsorbent surface