Khaled Walha

Precipitation and adsorption during fluoride removal from water by calcite in the presence of acetic acid

ABSTRACTDefluoridation of groundwater is of major concern in several places around the world, such as North and East Africa, India and China. In this paper, removal of fluoride from model solutions and a Tunisian groundwater sample was performed using calcite particles in the presence of acetic acid in batch experiments. After 1 h decantation, dead-end microfiltration was further used to retain the fluorite (CaF2) precipitates present in the supernatant. At 5 mg L−1 fluoride concentration, removal efficiency was found to increase from 17.4% without acid to 30.4% with 0.1 M acetic acid. The increase in fluoride removal with acetic acid was mainly attributed to the renewal of the area available for adsorption on the calcite particles. At the fluoride concentration of 50 mg L−1, the removal efficiency was equal to 9.5% without acid and 94.3% with the addition of 0.1 M acetic acid. The removal of fluoride was attributed to precipitation as a result of higher supersaturation in the solution. Optimum parameters...

Fluoride removal from aqueous solution by Purolite A520E resin: kinetic and thermodynamics study

AbstractFluoride in drinking water above permissible level causes dental and skeletal fluorosis. Fluoride removal operations have been conducted first on a “model” water solution (i.e. distilled) in which the fluoride concentration has been varied, and second on underground water (Louza 2) using the Purolite A520E resin. Batch sorption studies were carried out to determine the effect of initial fluoride concentration, agitation time, adsorbent dose, co-ions, and temperature on the removal of fluoride by the resin. The amount of fluoride ions removed per unit mass of Purolite A520E resin, at 30°C from 5 mg L−1 fluoride ion solution, was estimated to be 2 mg g−1. The experimental data fitted well to the Langmuir and Freundlich isotherms. Thermodynamic parameters such as ΔH°, ΔS°, and ΔG° were calculated, indicating that the adsorption process was spontaneous and endothermic. The fluoride content was reduced to 1.20 from 3.39 mg L−1 by treating Louza 2 water with the Purolite A520E resin (2 g L−1, shaking ti...

Granulated cork as biosorbent for the removal of phenol derivatives and emerging contaminants

This study evaluated the ability of cork to adsorb a broad range of phenolic, pharmaceutical and cosmetic compounds: phenol, 2-chlorophenol, 2-nitrophenol, 2,4-dichlorophenol, pentachlorophenol carbamazepine, naproxen, ketoprofen, diclofenac, triclosan, and methyl paraben. The effect of variables such as the compound concentrations and the amount of cork were studied resulting in a highly pH dependence in the case of phenolic compounds. Maximum removal percentages and uptake values of 75% (1.61 mg/g) for 2,4-dichlorophenol, 55% (1.25 mg/g) for 2-nitrophenol, 45% (1.47 mg/g) for 2-chlorophenol, 20% (0.63 mg/g) for phenol, and 100% for pentachlorophenol, were obtained for a 30 mg L-1 solution at pH 6, showing that the adsorption process increased with greater electronegativity of the phenolic substituting group. Removal percentages and uptakes of 82% (3.56 mg/g) for naproxen, 57% (2.31 mg/g) for ketoprofen, 50% (1.84 mg/g) for carbamazepine, 50% (1.78 mg/g) for methyl paraben, 100% for sodium diclofenac, and 100% for triclosan, were obtained using 5 mg of cork and a 1 mg L-1 solution of each compound. The adsorption process was almost complete after 30 min for all the micropollutants. Experimental equilibrium data were analysed by Freundlich and Langmuir adsorption models. Cork has proved to be an effective sorbent for the removal of phenols and emerging contaminants from contaminated waters and is a readily available material that can be acquired at minimal or no cost in cork-producing areas.