Arsenic removal from water/wastewater using adsorbents—A critical review

A review of potentially low-cost sorbents for heavy metals

A review on the utilization of fly ash

The sorption of three divalent metal ions — copper, nickel and lead — from aqueous solution onto peat in single component systems has been studied and the equilibrium isotherms determined. The experimental data have been analysed using the Langmuir, Freundlich, Redlich-Peterson, Toth, Temkin, Dubinin-Radushkevich and Sips isotherm models. In order to determine the best fit isotherm for each system, six error analysis methods were used to evaluate the data: the coefficient of determination, the sum of the errors squared, a hybrid error function, Marquardt's percent standard deviation, the average relative error and the sum of absolute errors. The error values demonstrated that the Sips equation provided the best model for the three sets of experimental data overall.

http://dns2.asia.edu.tw/~ysho/YSHO-English/Publications/PDF/Wat%20Air%20Soi%20Pol141,%201.pdf

Equilibrium isotherm studies for the sorption of divalent metal ions onto peat: copper, nickel and lead single component systems

Lead removal from aqueous solution by natural and pretreated clinoptilolite: adsorption equilibrium and kinetics.

The removal of Pb(II) from aqueous solution by adsorption on china clay and wollastonite is an attractive process. The amount of Pb(II) removed by adsorption is highly dependent on the temperature of the adsorbate solution and favours low temperature. The equilibrium times were noted, i.e. 90 min for china clay and 120 min for wollastonite. The various rate parameters of the adsorption process have been determined at different temperatures. The activation energies were determined and found to be −5.345 kJ mol−1 and −8.730 kJ mol−1 for Pb(II)-china clay and Pb(II)-wollastonite systems, respectively. The adsorption isotherm was measured experimentally at various temperatures. The negative values of enthalpy change (ΔH = −77.95 kJ mol−1 and −16.40 kJ mol−1 for china clay and wollastonite, respectively) indicate the exothermic nature of the adsorption processes for both systems. The isosteric heats of the adsorption process have been determined at various surface coverages of the adsorbents used. The various thermodynamic parameters have been calculated to elucidate the mechanism involved in the adsorption process.

Effect of temperature on the removal of lead(II) by adsorption on China clay and wollastonite

The removal of Cd(II) by adsorption on fly ash has been found to be contact time, concentration, temperature and pH dependent. The process of removal follows first order adsorption kinetics and the rate controlling step is intrap article transport into the pores of fly ash particles. The equilibrium nature of Cd(II) adsorption at different temperatures has been described by the Langmuir isotherm. The temperature dependence of Cd(II) adsorption on fly ash indicates the exothermic nature of adsorption. Alkaline aqueous medium favours the removal of Cd(II) by fly ash. The increase in adsorption of Cd(II) with pH has been explained on the basis of surface complex formation approach.

Fly ash for the treatment of Cd(II) rich effluents

The removal of Pb(II) is dependent of contact time, concentration, pH and temperature, of the solution. The various rate parameters of adsorption, have been determined at different concentrations and temperatures for the present system. An empirical model has been tested to understand the kinetics of Pb(II) removal at different concentrations. The pore diffusion is mainly rate controlling step. The Langmuir isotherm has been applied to find out the adsorption parameters involved in the present adsorption process. The isosteric heat of adsorption has been determined at different surface coverages of the adsorbent. The negative value of enthalpy change (? H= ‐7.269 Kcal mol‐1) suggests the exothermic nature of the adsorption process. The activation energy has been determined and found to be ‐8.533 Kjoules. The various thermodynamic parameters have been calculated to understand the clear mechanism involved in the adsorption process.

Fly-ash for the treatment of water enriched in lead(II)

The present investigation describes the use of china clay for the removal of As(III) from aqueous solution at different concentrations, retention times, temperatures and pH of the solution. The process of removal follows first order rate expression and the uptake of adsorbate within the pores of china clay is also diffusion controlled. The equilibrium data of As(III) at various temperatures follow Langmuir isotherm. The mass transfer coefficient (sL) of As(III) diffusion has been determined at 20°, 30° and 40°C. Maximum removal was found at pH 8. In order to understand the mechanism of As(III) removal by china clay, thermodynamic parameters were calculated.

K.P. Yadava

Papers

Effect of temperature on the removal of lead(II) by adsorption on China clay and wollastonite

Fly ash for the treatment of Cd(II) rich effluents

Fly-ash for the treatment of water enriched in lead(II)

Removal of arsenic(III) from aqueous solution by china clay