Adsorption, Hysteresis, and Trapping of Heavy Metals with Environmental Relevance onto Different Quick Clays and Montmorillonite

Industrial and pharmaceutical activities are contributing to global environmental contamination. These pollutants having various physicochemical properties are harmful to aquatic organisms and ecosystems. Among daily discharged pollutants, heavy metals can be removed from wastewater by sorption process using natural clay minerals. Quick clays (QCs) are unique glaciomarine clays with unstable structures contributing to their high cation exchange affinity. With a high cation exchange affinity, QC clays could be used as adsorbents in wastewater treatment. QCs could also have a significant impact on the fate of pollutants in littoral ecosystems. However, no research has yet reported on the ability of QCs to adsorb and trap heavy metals. In this work, we investigated the kinetics, sorption isotherms, and hysteresis of copper (Cu) and cadmium (Cd) on three Canada quick clays and montmorillonite (MMT), mostly recognized as a reference clay. Kinetics and isotherms results were processed using different sorption models to assess the sorption and hysteresis parameters of these clays. QCs were characterized by a rapid uptake with an equilibrium time of 10 min for both metals. They showed high distribution coefficients (k(d)) ranging from 2520 to 51,740 mL & BULL;g(-1) for Cu and 190 to 4590 mL & BULL;g(-1) for Cd, respectively. The Freundlich sorption isotherm model showed better fits for sorption experimental data with a sorption capacity constant (k(f)) ranging from 3.41 to 10.74 mg & BULL;g(-1)& BULL;(L & BULL;mg(-1))(1/n) for Cu and 0.60 to 1.07 mg & BULL;g(-1)& BULL;(L & BULL;mg(-1))(1/n) for Cd. QC showed a similar or higher adsorption capacity for these metals compared to MMT. Cu and Cd adsorption on QC were respectively 10 and 2.5 times more important than on MMT. Results have shown a hysteresis process for Cu and Cd suggesting a sequestration process of these metals on QC.

Automated summary

Industrial and pharmaceutical activities are causing environmental contamination, with heavy metals being a major pollutant. In this study, the sorption capacity of quick clays (QCs) from Canada for copper (Cu) and cadmium (Cd) was investigated. The results showed that QCs had a high affinity for these metals, with fast uptake and high distribution coefficients. The sorption isotherm model provided a good fit for the experimental data, and QCs exhibited similar or higher adsorption capacity compared to montmorillonite (MMT). Hysteresis was observed, suggesting a sequestration process on QCs.