Sorption of Cu2+ Ions by Bentonite Modified with Al Keggin Cations and Humic Acid in Solutions with pH 4.5

Abstract

The sorption of Cu2+ onto bentonite modified with Al Keggin cations and humic acid from CuCl2 solutions at pH 4.5 was studied. Modification of Na-bentonite with Al Keggin cations was found to result in an increase in the basal spacing of montmorillonite from 1.29 nm for N-form to 1.85 and 1.78 nm for HAl13 and Al13 forms respectively, in a reduction of CEC (cation exchange capacity) and in the formation of additional sites with a variable charge with pHPZC 4.2. Al13-bentonite is not affected by heat. Under the conditions of the experiments at pH of 4.5 Na-bentonite adsorbs more Cu2+ from CuCl2 solutions then Al13 forms of bentonites. The main mechanism of copper sorption on Na-bentonite is the cation exchange Cu2+–Na+. The reduction of CEC of Na-bentonite after modification with Al Keggin cations leads to a decrease in the Cu2+ sorption. pH-dependent sorption sites on Al13-bentonites have a pHPZC of 4.2 and, therefore, under conditions of the experiment have positive charge which prevents Cu2+ sorption. Na-bentonite adsorbs more humic acid solution (HA) then Al13-bentonite and the proportion of adsorbed HA remains constant over the entire concentration range. Treatment of the Al13-bentonite with HA leads to the formation of the additional sorption sites. The amount of sorbed Cu2+ and the percentage of their extraction from solutions by HAAl13-bentonite is similar to those values for Na-bentonite.

Adsorption and Desorption of Cd: Characteristics and Mechanisms in Reclaimed Soil Under the Influence of Dissolved Organic Carbon

“…The ionization of H + in the oxygen-containing functional groups of HA reduces the pH of the reclaimed soil solution, thereby changing the metal solubility and further reducing the Cd adsorption capacity of the soil. [32][33][34][35] Furthermore, HA, which is rich in anionic groups, such as phenolic, hydroxyl, and carboxyl groups, precedes Cd at occupying the soil seat sites via soil surface adsorption, [36][37] thereby reducing the Cd adsorption capacity of reclaimed soil. This interpretation of results is consistent with other ndings indicating that DOC has a signi cant inhibitory effect on Cd adsorption in soil.…”

Study adsorbents based on bent-Al13-CS-CTA and its application to the removal of CR from wastewater

“…Firstly, a 0.5 M NaOH solution was gently added to a vigorously stirred 0.3 M AlCl 3 ·6H 2 O solution at 60 °C, achieving a ratio of n [OH − ]/ n [Al 3+ ] = 0.8. 28 The stirring process continued for 2 hours, followed by incubation at an elevated temperature for 24 hours. Subsequently, the resulting mixture was then agitated for 5 hours at 60 °C and maintained at this temperature for another 24 hours before being rinsed multiple times with deionized water until no chloride ions were visible.…”

Adsorption and desorption of Cd in reclaimed soil under the influence of humic acid: characteristics and mechanisms

“…The ionization of H + in the oxygen-containing functional groups of HA reduces the pH of the reclaimed soil solution, thereby changing the metal solubility and further reducing the Cd adsorption capacity of soil (Li et al 2018;Yang 2018;Yan 2019;Jagadamma et al 2014). Furthermore, HA, which is rich in anionic groups (e.g., phenolic, hydroxyl, and carboxyl groups) occupies the soil seat sites quicker than Cd via soil surface adsorption (He et al 2020;Izosimova et al 2020), thereby reducing the Cd adsorption capacity of reclaimed soil. This interpretation of results is consistent with previous findings, indicating that HA exerts a significant inhibitory effect on Cd adsorption in soil (Bi et al 2018).…”