Sorption Reversibility of Cadmium from Aqueous Solutions on Natural Firoozkoh Zeolite

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.