Removal of hardness agents, calcium and magnesium, by natural and alkaline modified pumice stones in single and binary systems

Abstract

International audienceNatural and alkaline modified pumice stones were used for the adsorption of water hardening cations, Ca2+ and Mg2+. The adsorbents were characterized using XRF, XRD, SEM and FTIR instrumental techniques. At equilibrium time and for 150 mg/L of a given cation, removal efficiencies were 83% and 94% for calcium and 48% and 73% for magnesium for raw and modified pumices, respectively. The optimal pH for raw and modified pumices were found to be 6.0, leading to the removal of 79 and 96% of calcium and 51 and 93% of magnesium by 10 g/L of raw and modified pumice adsorbents, respectively. Maximum adsorption capacities were 57.27 and 62.34 mg/g for Ca2+ and 44.53 and 56.11 mg/g for Mg2+ on the raw and modified pumices, respectively. Ca2+ and Mg2+ adsorption capacities of the pumice adsorbents decreased in the presence of competing cations. Less than 300 min were needed to achieve 99 and 92% desorption of the adsorbed Ca2+ and 100 and 89% of the adsorbed Mg2+ from the natural and modified pumices, respectively. After treating synthetic water solution simulating an actual water stream with the alkali-modified pumice, total hardness of the treated sample met the required standard for drinking water, namely below 300 mg/L of CaCO3 (297.5 mg/L). The studied pumice adsorbents, and especially the treated pumice, can be therefore considered as promising low cost adsorbents, suitable for the removal of hardness ions from drinking water

Dye Removal From Textile Waste Water Through The Adsorption By Pumice Used In Stone Washing

“…Natural and alkali-modified pumice adsorbents can be used for softening of hard water. Pumice adsorbents showed a higher selectivity for calcium adsorption compared to magnesium, especially [12]. Contrary to the works reported in the literature; the pumice used in this study is the waste of stone washing process.…”

“…As shown in the figure, the spectra of used and unused samples have the same features, only a dome is observed between 2q=5 and 40° indicating the presence of only amorphous phase in both samples [12]. Figure 2 shows the ATR-FTIR spectra of unused and used pumice stones at wave numbers in 4500-500 cm −1 .…”

“…Both spectra have the adsorption bands at approximately 1055 cm −1 and 785 cm −1 that are assigned to the symmetric stretching vibration of Si-O-Si and bending vibration of Si-O bonds, respectively [12]. The broadening peak at approximately 3626 cm -1 is attributed to Al-Al-OH stretching [24] and also asymmetric stretching vibration of H-O bond of adsorbed water molecules [12]. Other peak observed at approximately 1636 cm −1 is also owing to the bending vibration of H-O-H bond in adsorbed water molecules.…”

Application of Central Composite Design in the Adsorption of Ca(II) on Metakaolin Zeolite

“…The determination of Ca 2+ ions in aqueous solution was done by complexometric titration using standardized 0.1 M EDTA (ethylenediaminetetraacetic acid) in the presence of Eriochrome Black T as an indicator. Typically, 100 mL of each supernatant solution was pipetted into a 250 mL conical flask, 4 mL of 1.0 M NH 3 solution and 2-3 drops of Eriochrome Black T were added, and the mixture was titrated with 0.1 M EDTA solution until the color changed from pink to blue [12].…”

“…Because of their unique porous properties, zeolites could be applied in the removal of hardness in domestic water which is mainly due to calcium and magnesium ions. Water supplies with total hardness of more than 500 mg/L are not suitable for domestic consumption [12]. Hard water is responsible for the formation of deposits in boilers, cooling towers, water pipes, and household facilities, as well as diverse influences on the cleaning performance of detergents.…”