Preparation and characterization of Na-A zeolite from aluminum scrub and commercial sodium silicate for the removal of Cd2+ from water

Abstract

In this work, a low cost preparation scheme of Na-A zeolite from low cost materials was described. Aluminum scrubs were used to prepare sodium aluminate. Commercial sodium silicate and sodium aluminate were then used in the synthesis of zeolite through hydrothermal method under mild conditions. X-ray fluorescence (XRF), X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques were employed to confirm the synthesis of pure Na-A zeolite phase. The specific surface area (BET) of the prepared zeolite has also been measured. Results indicated that zeolite has relatively high surface area (=374 m²/g). The performance of the prepared zeolite in the removal of Cd²⁺, a highly toxic heavy metal, from water was investigated. The removal of Cd²⁺ from water which occurred through precipitation and ion exchange mechanisms was seen to be more efficient comparing to the previous studies. The maximum sorption capacity of Cd²⁺ was found to be 54.05 meq/100 g according to the Langmuir isotherm model. However, the sorption capacity was found to be 84.09 meq/100 g after 4 repetitions which is attributed to the ease of reaching the Cd²⁺ ions to the inner pores of zeolite upon using slightly dilute Cd²⁺ solutions in each repetition.