Adsorption of Pollutant Ions From Residual Aqueous Solutions Onto Nano-Structured Calcium Silicate

Abstract

The sorption of contaminant ions existing in residual aqueous solutions onto nano-structured calcium silicate has been studied. The sorbent was prepared by chemical reaction between a soluble solution of sodium silicate and calcium hydroxide. X-ray diffraction analysis showed the amorphous character of the obtained calcium silicate, although patterns associated to wollastonite, CaSiO 3 , and larnyta-syn, Ca 2 SiO 4 were detected. The particle mean size was approximate 0.5 to 1.0 µm having an average BET surface area of 333.0 m 2 /g and a mean pore diameter variable between 15.8-23.6 nm. The nano-structured calcium silicates were contacted with industrial residual aqueous solutions containing, among others, Cu(II), Zn(II), Cd(II) and the anions PO 4 3-, SO 4 = and CrO 4 = , being copper (II) and phosphate the ions that were most easily and quantitatively adsorbed. The results of equilibrium experiments showed that the Redlich-Peterson adsorption isotherm model explained the experimental results for some metal ions.The experimental kinetics followed a pseudo-second-order kinetics model for Cu(II) and Zn(II) sorption.

Fundamentals and Practical Aspects of Acid Mine Drainage Treatment: An Overview from Mine Closure Perspective

“…Additionally, the permeability of these systems needs to be secured. Unreactive or low-reaction alkali materials are used as a fixed bed introducing more reactive materials inside the pores that can range from specifically designed materials to wastes from other industries such as ferrihydrite-bearing soils or nanostructured calcium silicate adsorbent, among others [89,90]. Since the growth of vegetation is not present in these systems, the permeability may be designed to avoid dead volumes or volumes with low mixing capabilities.…”

Wastewater Treatment through Low Cost Adsorption Technologies

“…The synthesized nanostructured calcium silicates exhibit a specific surface area, averaging values over 100-400 m 2 /g, showing a good sorption capacities for removing high contents of different ionic species. The mechanisms governing the sorption process are related to the presence of silanol, calcium and hydroxyl groups in its structure, which would act as binding or nucleation sites on its surface [16]. Recent efforts for modifying nanostructured calcium silicates by introducing in their structures other metals that generate an improved sorbent addressed to enhance the sorption of other species present in solutions like the AMD, by using simple and low-cost processes, have been achieved.…”