JWSS - Journal of Water and Soil Science

Sorption hysteresis in soil constituents has important environmental implications such as pollutant transport and bioavailability. This research was carried out to study sorption reversibility of cadmium (Cd) on natural zeolite. Sorption isotherms were derived by sorption of Cd (П) from solutions containing different concentrations of Cd in the range of 1 to 10 mg L-1 using a 24h batch equilibration experiment. Desorption of Cd(II) was studied with the clay samples initially treated with the metal loadings of 50 and 100% maximum sorption capacity (SCmax) during the sorption study. Sorption isotherms of Cd were well described by the Freundlich and Coble-Korrigan models (R2=0.96). Desorption isotherms of Cd from zeolite showed little deviation from sorption data indicating reversible sorption. On the other hand, the results revealed no hysteresis. The average amount of 71.75 % of the initially sorbed Cd was desorbed from zeolite after five successive desorption steps. Release of such a relatively high proportion of sorbed Cd indicates that zeolite is an effective sorbent for the repeated purification of polluted water and wastewater.

Removal of boron from aqueous environments (soil and water) is difficult, because it is present as B(OH)3 and B(OH)4- species. This research was done to study the sorption of boron by HDTMA-modified zeolite. The sorption of B on modified zeolite was studied as a function of pH (B concentration: 1 and 10 mg L-1) in the range of 6-9.5, and as a function of ionic strength (0.03 and 0.06 M Ca(NO3)2 or Mg(NO3)2) at a constant B concentration of 5 mg L-1. Sorption isotherm was performed for the solutions containing initial B concentration in the range of 1-15 mg L-1 using a 24h batch equilibration experiment. The results revealed that surfactant-modified zeolite exhibited the best performance at pH 9.5, and sorption of B increased with the increase of suspension pH. Greater B adsorption in the Ca system over the Mg system was clearly observed for the modified zeolite. Sorption isotherm of B were well described by the Freundlich and Langmuir models but the Freundlich sorption model described the interaction between B and the mineral material better than the Langmuir model. Maximum sorption capacity (qmax) of the sorbent was 120 mmol kg-1. The experimental data showed that HDTMA-modified zeolite used in this study had a reasonable sorption capacity for B.